A BASIC GUIDE OF ARC WELDING ELECTRODES

Best Institutes of Welding Learning & Training

2020-03-16T23:22:00.001-07:00

KENTUCKY WELDING INSTITUTE

Overview: Are you looking to chase paper? The CPW program is designed to gain you employment in paper mills, power plants, refineries, nuclear power, pipeline, and other pipe-related jobs in both new construction and repair and maintenance work. Be prepared to work hard and continually push yourself to make that next weld better than the last.

WHAT YOU WILL LEARN:
All Processes on Pipe (SMAW, FCAW, GTAW, GMAW)
Carbon, Stainless, and Aluminum base metals and filler metals.
ISO drawings, pipefitting and prep on jack stands and in pipe lab
NCCER Welder, Boilermaker, Rigger, Pipefitter
All Processes on Plate (SMAW, FCAW, GTAW, GMAW)
Carbon base metals and stainless and carbon filler metals
Print Reading, layout, and fit up
NCCER Welder, Boilermaker, Rigger

1828 Maysville Road
Flemingsburg, KY 41041

Phone: (606) 849-9353

PLC Control Lathe Type Automatic Girth Welder

2020-03-16T23:09:00.002-07:00

PLC control Lathe type automatic girth welder

PLC control automatic girth welder/girth welding machine for pipe, water tank, gas tank, stainless steel tank,etc. This new technology has been introduced by Chinese. Very effective, low cost with multiple options machine.

Shielded metal arc welding

2015-10-31T00:22:00.002-07:00

Shielded metal arc welding (SMAW), also known as manual metal arc welding (MMA or MMAW), flux shielded arc welding^[1] or informally as stick welding, is a manual arc welding process that uses a consumable electrode covered with a flux to lay the weld.

An electric current, in the form of either alternating current or direct current from a welding power supply, is used to form an electric arc between the electrode and the metals to be joined. The workpiece and the electrode melts forming the weld pool that cools to form a joint. As the weld is laid, the flux coating of the electrode disintegrates, giving off vapors that serve as a shielding gas and providing a layer of slag, both of which protect the weld area from atmospheric contamination.

Because of the versatility of the process and the simplicity of its equipment and operation, shielded metal arc welding is one of the world's first and most popular welding processes. It dominates other welding processes in the maintenance and repair industry, and though flux-cored arc welding is growing in popularity, SMAW continues to be used extensively in the construction of heavy steel structures and in industrial fabrication. The process is used primarily to weld iron andsteels (including stainless steel) but aluminium, nickel and copper alloys can also be welded with this method.^[2]

Development[edit]

After the discovery of the short pulsed electric arc in 1800 by Humphry Davy^[3]^[4] and of the continuous electric arc in 1802 by Vasily Petrov,^[4]^[5] there was little development in electrical welding until Auguste de Méritens developed a carbon arc torch that was patented in 1881.^[1]

In 1885, Nikolay Benardos and Stanisław Olszewski developed carbon arc welding,^[6] obtaining American patents from 1887 showing a rudimentary electrode holder. In 1888, the consumable metal electrode was invented by Nikolay Slavyanov. Later in 1890, C. L. Coffin received U.S. Patent 428,459 for his arc welding method that utilized a metal electrode. The process, like SMAW, deposited melted electrode metal into the weld as filler.^[7]

Around 1900, A. P. Strohmenger and Oscar Kjellberg released the first coated electrodes. Strohmenger used clay and lime coating to stabilize the arc, while Kjellberg dipped iron wire into mixtures of carbonates andsilicates to coat the electrode.^[8] In 1912, Strohmenger released a heavily coated electrode, but high cost and complex production methods prevented these early electrodes from gaining popularity. In 1927, the development of an extrusion process reduced the cost of coating electrodes while allowing manufacturers to produce more complex coating mixtures designed for specific applications. In the 1950s, manufacturers introduced iron powder into the flux coating, making it possible to increase the welding speed.^[9]

In 1938 K. K. Madsen described an automated variation of SMAW, now known as gravity welding. It briefly gained popularity in the 1960s after receiving publicity for its use in Japanese shipyards though today its applications are limited. Another little used variation of the process, known as firecracker welding, was developed around the same time by George Hafergut in Austria.^[10]

Operation[edit]

SMAW weld area

To strike the electric arc, the electrode is brought into contact with the workpiece by a very light touch with the electrode to the base metal then is pulled back slightly. This initiates the arc and thus the melting of the workpiece and the consumable electrode, and causes droplets of the electrode to be passed from the electrode to the weld pool. As the electrode melts, the flux covering disintegrates, giving off shielding gases that protect the weld area from oxygen and otheratmospheric gases. In addition, the flux provides molten slag which covers the filler metal as it travels from the electrode to the weld pool. Once part of the weld pool, the slag floats to the surface and protects the weld from contamination as it solidifies. Once hardened, it must be chipped away to reveal the finished weld. As welding progresses and the electrode melts, the welder must periodically stop welding to remove the remaining electrode stub and insert a new electrode into the electrode holder. This activity, combined with chipping away the slag, reduces the amount of time that the welder can spend laying the weld, making SMAW one of the least efficient welding processes. In general, the operator factor, or the percentage of operator's time spent laying weld, is approximately 25%.^[11]

The actual welding technique utilized depends on the electrode, the composition of the workpiece, and the position of the joint being welded. The choice of electrode and welding position also determine the welding speed. Flat welds require the least operator skill, and can be done with electrodes that melt quickly but solidify slowly. This permits higher welding speeds.

Sloped, vertical or upside-down welding requires more operator skill, and often necessitates the use of an electrode that solidifies quickly to prevent the molten metal from flowing out of the weld pool. However, this generally means that the electrode melts less quickly, thus increasing the time required to lay the weld.^[12]

Quality[edit]

The most common quality problems associated with SMAW include weld spatter, porosity, poor fusion, shallow penetration, and cracking.

Weld spatter, while not affecting the integrity of the weld, damages its appearance and increases cleaning costs. It can be caused by excessively high current, a long arc, or arc blow, a condition associated with direct current characterized by the electric arc being deflected away from the weld pool by magnetic forces. Arc blow can also cause porosity in the weld, as can joint contamination, high welding speed, and a long welding arc, especially when low-hydrogen electrodes are used.

Porosity, often not visible without the use of advanced nondestructive testing methods, is a serious concern because it can potentially weaken the weld. Another defect affecting the strength of the weld is poor fusion, though it is often easily visible. It is caused by low current, contaminated joint surfaces, or the use of an improper electrode.

Shallow penetration, another detriment to weld strength, can be addressed by decreasing welding speed, increasing the current or using a smaller electrode. Any of these weld-strength-related defects can make the weld prone to cracking, but other factors are involved as well. High carbon, alloy or sulfur content in the base material can lead to cracking, especially if low-hydrogen electrodes and preheating are not employed. Furthermore, the workpieces should not be excessively restrained, as this introduces residual stresses into the weld and can cause cracking as the weld cools and contracts.^[13]

Safety[edit]

SMAW welding, like other welding methods, can be a dangerous and unhealthy practice if proper precautions are not taken. The process uses an open electric arc, which presents a risk of burns which are prevented by personal protective equipment in the form of heavy leather gloves and long sleeve jackets. Additionally, the brightness of the weld area can lead to a condition called arc eye, in which ultraviolet light causes inflammation of the cornea and can burn the retinas of the eyes. Welding helmets with dark face plates are worn to prevent this exposure, and in recent years, new helmet models have been produced that feature a face plate that self-darkens upon exposure to high amounts of UV light. To protect bystanders, especially in industrial environments, translucent welding curtains often surround the welding area. These curtains, made of a polyvinyl chloride plastic film, shield nearby workers from exposure to the UV light from the electric arc, but should not be used to replace the filter glass used in helmets.^[14]

In addition, the vaporizing metal and flux materials expose welders to dangerous gases and particulate matter. The smoke produced contains particles of various types of oxides. The size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger. Additionally, gases like carbon dioxide and ozone can form, which can prove dangerous if ventilation is inadequate. Some of the latest welding masks are fitted with an electric powered fan to help disperse harmful fumes.^[15]

Application and materials[edit]

Shielded metal arc welding is one of the world's most popular welding processes, accounting for over half of all welding in some countries. Because of its versatility and simplicity, it is particularly dominant in the maintenance and repair industry, and is heavily used in the construction of steel structures and in industrial fabrication. In recent years its use has declined as flux-cored arc welding has expanded in the construction industry and gas metal arc welding has become more popular in industrial environments. However, because of the low equipment cost and wide applicability, the process will likely remain popular, especially among amateurs and small businesses where specialized welding processes are uneconomical and unnecessary.^[16]

SMAW is often used to weld carbon steel, low and high alloy steel, stainless steel, cast iron, and ductile iron. While less popular for nonferrous materials, it can be used on nickel and copper and their alloys and, in rare cases, on aluminium. The thickness of the material being welded is bounded on the low end primarily by the skill of the welder, but rarely does it drop below 1.5 mm (0.06 in). No upper bound exists: with proper joint preparation and use of multiple passes, materials of virtually unlimited thicknesses can be joined. Furthermore, depending on the electrode used and the skill of the welder, SMAW can be used in any position.^[17]

Equipment[edit]

SMAW system setup

Shielded metal arc welding equipment typically consists of a constant current welding power supply and an electrode, with an electrode holder, a 'ground' clamp, and welding cables (also known as welding leads) connecting the two.

Power supply[edit]

The power supply used in SMAW has constant current output, ensuring that the current (and thus the heat) remains relatively constant, even if the arc distance and voltage change. This is important because most applications of SMAW are manual, requiring that an operator hold the torch. Maintaining a suitably steady arc distance is difficult if a constant voltage power source is used instead, since it can cause dramatic heat variations and make welding more difficult. However, because the current is not maintained absolutely constant, skilled welders performing complicated welds can vary the arc length to cause minor fluctuations in the current.^[18]

A high output welding power supply for Stick, GTAW, MIG, Flux-Cored, & Gouging

The preferred polarity of the SMAW system depends primarily upon the electrode being used and the desired properties of the weld. Direct current with a negatively charged electrode (DCEN) causes heat to build up on the electrode, increasing the electrode melting rate and decreasing the depth of the weld. Reversing the polarity so that the electrode is positively charged (DCEP) and the workpiece is negatively charged increases the weld penetration. With alternating current the polarity changes over 100 times per second, creating an even heat distribution and providing a balance between electrode melting rate and penetration.^[19]

Typically, the equipment used for SMAW consists of a step-down transformer and for direct current models a rectifier, which converts alternating current into direct current. Because the power normally supplied to the welding machine is high-voltage alternating current, the welding transformer is used to reduce the voltage and increase the current. As a result, instead of 220 V at 50 A, for example, the power supplied by the transformer is around 17–45 V at currents up to 600 A. A number of different types of transformers can be used to produce this effect, including multiple coil and inverter machines, with each using a different method to manipulate the welding current. The multiple coil type adjusts the current by either varying the number of turns in the coil (in tap-type transformers) or by varying the distance between the primary and secondary coils (in movable coil or movable core transformers). Inverters, which are smaller and thus more portable, use electronic components to change the current characteristics.^[20]

Electrical generators and alternators are frequently used as portable welding power supplies, but because of lower efficiency and greater costs, they are less frequently used in industry. Maintenance also tends to be more difficult, because of the complexities of using a combustion engine as a power source. However, in one sense they are simpler: the use of a separate rectifier is unnecessary because they can provide either AC or DC.^[21] However, the engine driven units are most practical in field work where the welding often must be done out of doors and in locations where transformer type welders are not usable because there is no power source available to be transformed.

In some units the alternator is essentially the same as that used in portable generating sets used to supply mains power, modified to produce a higher current at a lower voltage but still at the 50 or 60 Hz grid frequency. In higher-quality units an alternator with more poles is used and supplies current at a higher frequency, such as 400 Hz. The smaller amount of time the high-frequency waveform spends near zero makes it much easier to strike and maintain a stable arc than with the cheaper grid-frequency sets or grid-frequency mains-powered units.

Electrode[edit]

Various accessories for SMAW

The choice of electrode for SMAW depends on a number of factors, including the weld material, welding position and the desired weld properties. The electrode is coated in a metal mixture called flux, which gives off gases as it decomposes to prevent weld contamination, introduces deoxidizers to purify the weld, causes weld-protecting slag to form, improves the arc stability, and provides alloying elements to improve the weld quality.^[22] Electrodes can be divided into three groups—those designed to melt quickly are called "fast-fill" electrodes, those designed to solidify quickly are called "fast-freeze" electrodes, and intermediate electrodes go by the name "fill-freeze" or "fast-follow" electrodes. Fast-fill electrodes are designed to melt quickly so that the welding speed can be maximized, while fast-freeze electrodes supply filler metal that solidifies quickly, making welding in a variety of positions possible by preventing the weld pool from shifting significantly before solidifying.^[23]

The composition of the electrode core is generally similar and sometimes identical to that of the base material. But even though a number of feasible options exist, a slight difference in alloy composition can strongly impact the properties of the resulting weld. This is especially true of alloy steels such as HSLA steels. Likewise, electrodes of compositions similar to those of the base materials are often used for welding nonferrous materials like aluminium and copper.^[24] However, sometimes it is desirable to use electrodes with core materials significantly different from the base material. For example, stainless steel electrodes are sometimes used to weld two pieces of carbon steel, and are often utilized to weld stainless steel workpieces with carbon steel workpieces.^[25]

Electrode coatings can consist of a number of different compounds, including rutile, calcium fluoride, cellulose, and iron powder. Rutile electrodes, coated with 25%–45% TiO₂, are characterized by ease of use and good appearance of the resulting weld. However, they create welds with high hydrogen content, encouraging embrittlement and cracking. Electrodes containing calcium fluoride (CaF₂), sometimes known as basic or low-hydrogen electrodes, are hygroscopic and must be stored in dry conditions. They produce strong welds, but with a coarse and convex-shaped joint surface. Electrodes coated with cellulose, especially when combined with rutile, provide deep weld penetration, but because of their high moisture content, special procedures must be used to prevent excessive risk of cracking. Finally, iron powder is a common coating additive that increases the rate at which the electrode fills the weld joint, up to twice as fast.^[26]

To identify different electrodes, the American Welding Society established a system that assigns electrodes with a four- or five-digit number. Covered electrodes made of mild or low alloy steel carry the prefix E, followed by their number. The first two or three digits of the number specify the tensile strength of the weld metal, in thousand pounds per square inch (ksi). The penultimate digit generally identifies the welding positions permissible with the electrode, typically using the values 1 (normally fast-freeze electrodes, implying all position welding) and 2 (normally fast-fill electrodes, implying horizontal welding only). The welding current and type of electrode covering are specified by the last two digits together. When applicable, a suffix is used to denote the alloying element being contributed by the electrode.^[27]

Common electrodes include the E6010, a fast-freeze, all-position electrode with a minimum tensile strength of 60 ksi (410 MPa) which is operated using DCEP^[28]

. E6011 is similar except its flux coating allows it to be used with alternating current in addition to DCEP. E7024 is a fast-fill electrode, used primarily to make flat or horizontal welds using AC, DCEN, or DCEP. Examples of fill-freeze electrodes are the E6012, E6013, and E7014, all of which provide a compromise between fast welding speeds and all-position welding.

Process variations[edit]

Though SMAW is almost exclusively a manual arc welding process, one notable process variation exists, known as gravity welding or gravity arc welding. It serves as an automated version of the traditional shielded metal arc welding process, employing an electrode holder attached to an inclined bar along the length of the weld. Once started, the process continues until the electrode is spent, allowing the operator to manage multiple gravity welding systems. The electrodes employed (often E6027 or E7024) are coated heavily in flux, and are typically 71 cm (28 in) in length and about 6.35 mm (0.25 in) thick. As in manual SMAW, a constant current welding power supply is used, with either negative polarity direct current or alternating current. Due to a rise in the use of semiautomatic welding processes such as flux-cored arc welding, the popularity of gravity welding has fallen as its economic advantage over such methods is often minimal. Other SMAW-related methods that are even less frequently used include firecracker welding, an automatic method for making butt and fillet welds, and massive electrode welding, a process for welding large components or structures that can deposit up to 27 kg (60 lb) of weld metal per hour.^[10]

China–Pakistan Economic Corridor

2015-10-31T00:03:00.004-07:00

The China–Pakistan Economic Corridor (CPEC)^[a] is a ongoing development megaproject which aims to connect Gwadar Port in southwestern Pakistan to China’s northwestern autonomous region of Xinjiang, via a network of highways, railways and pipelines to transport oil and gas.^[1] The economic corridor is considered central to China–Pakistan relations and will run about 3,000 km from Gwadar to Kashgar. Overall construction costs are estimated at over $46 billion, with the entire project expected to be completed in several years.^[2]^[3] The Corridor is an extension of China’s proposed 21st century Silk Road initiative.^[4]^[5] According to a Firstpostreport, "this is the biggest overseas investment by China announced yet and the corridor is expected to be operational within three years and will be a strategic gamechanger in the region, which would go a long way in making Pakistan a richer and stronger entity than ever before."^[6]

Other than transport infrastructure, the economic corridor will provide Pakistan with telecommunications and energy infrastructure. The project also aims to improve intelligence sharing between the countries.^[7]^[8] China and Pakistan hope the massive investment plan will transform Pakistan into a regional economic hub as well as further boost the growing ties between Pakistan and China.^[9] The Pakistani media and government called the investments a "game and fate changer" for the region.^[10]^[11] According to The Guardian, "The Chinese are not just offering to build much-needed infrastructure but also make Pakistan a key partner in its grand economic and strategic ambitions."^[12] The project will also open trade routes for Western China and provide China direct access to the resource-rich Middle East region via the Arabian Sea, bypassing longer logistical routes currently through the Strait of Malacca.^[13]

During the state visit of President of China Xi Jinping to Pakistan in April 2015, he wrote in an open editorial that "This will be my first trip to Pakistan, but I feel as if I am going to visit the home of my own brother." During his visit, Islamabad was dotted with slogans and signboards such as "Pakistan-China friendship is higher than the mountains, deeper than the oceans, sweeter than honey, and stronger than steel." ^[14]

In August 2015, the two countries signed 20 more agreements worth $1.6 billion to further boost the corridor.^[15]

Gawadar Airport

Strategic importance[edit]

“

The move represents a shift toward greater economic cooperation between Pakistan and China, which have long had close security ties amid common disputes with neighboring India. The corridor would give China access to the Indian Ocean and lead to investments that would help ease power shortages that are hindering economic growth in Pakistan.

”

— Bloomberg Business on April 1, 2015, ^[28]

When the corridor is constructed, it will expand the number of trade routes between China, the Middle East and Africa. Energy security is a key concern for China, as it is the world's biggest oil importer,^[23] and oil pipelines through Pakistan would cut out ocean travel through Southeast Asia.^[29]

The Asian Development Bank terms the project as "CPEC will connect economic agents along a defined geography. It will provide connection between economic nodes or hubs, centered on urban landscapes, in which large amount of economic resources and actors are concentrated. They link the supply and demand sides of markets."^[30]

According to Chinese Foreign Ministry Spokesperson Hua Chunying, the corridor will "serve as a driver for connectivity between South Asia and East Asia." Mushahid Hussain, chairman of the Pakistan-China Institute, told China Daily that the economic corridor "will play a crucial role in regional integration of the 'Greater South Asia', which includes China, Iran, Afghanistan, and stretches all the way to Myanmar."^[19]

China plans to build oil storage facilities and a refinery at Gwadar Port, with oil transported to its Xinjiang Uighur Autonomous Region via road and pipeline. This will let it move energy and goods to inland China without going through the Strait of Malacca, which could be blocked by the U.S. or India should hostilities break out in the region. The project will also lead to development in western China, where tensions are simmering from activities by radical separatists.^[31]^[32] Iran has also responded positively over the proposal to link the Iran–Pakistan gas pipeline with China, with the Iranian ambassador to China describing it as a "common interest" between the three countries.^[33]

CPEC is considered economically vital to Pakistan in helping it drive economic growth.^[34] Moody's Investors Service has described the project as a "credit positive" for Pakistan. In 2015, the agency acknowledged that much of the project's key benefits would not materialise until 2017, but stated that it believes at least some of the benefits from the economic corridor would likely begin accruing even before then.^[35] A study by the Pew Research Center in 2014 found that 78% of Pakistanis have a positive view of China.^[26]^[36]

Gwadar - A Jewel in Crown

2015-10-30T23:57:00.006-07:00

Gwadar (Balochi: گوادر Gwadur) is a city on the southwestern Arabian Sea coastline of Pakistan, in Balochistan province. Under development as a free trade port, it is the district headquarters of Gwadar District and, in 2011, was designated the winter capital of Balochistan province. It is situated near to Persian gulf countries, Eastern European countries Armenia, Georgia, Azerbaijan and western Asian countries Iran and Turkey.

Until 1958, Gwadar was an overseas possession of Muscat and Oman. On 8 September 1958 it was annexed by Pakistan, with Oman then agreeing to sell its former enclave to Pakistan for a price of 5.5 billion rupees, with effect from 8 December 1958. The area was not integrated into Balochistan province of Pakistan until 1 July 1977, when it became a full sub-division called the Gwadar District and was designated as the "winter capital" of Balochistan. Most of the money for the purchase from Oman came from donations, with Prince Sultan Mohammad Shah, the reigning Aga Khan, being the greatest contributor, while the remainder was raised by taxation.^[2]Gwadar has a population of approximately 85,000. It is about 700 km from Karachi and 120 km from the Iranian border. Gwadar Port is located at the mouth of thePersian Gulf, just outside the Strait of Hormuz, near the key shipping routes in and out of the Persian Gulf.

Gwadar Port is a strategic warm-water deep-sea port developed jointly by the Government of Pakistan and the Government of China at a cost of USD $248 million and officially opened by the President of Pakistan on 20 March 2007.^[3]), which have been developed from scratch under an urban master plan. Before its development as a port city, the town was a fishing village. A master plan for the development of Gwadar City with land zoning and internal infrastructure networks was approved by the Government of Pakistan in 2003. The Gwadar Development Authority (GDA) is charged with the execution of this master plan. A major part of its current work program is focused on the fast-track construction of roads, other infrastructure and public buildings. The provincial government of Balochistan has started with the development of infrastructure for the industrial parks located east of the city. Related to this rapid development, the population growth rate of Gwadar has accelerated during the past two years. The current population of Gwadar city is estimated at around 85,000 and is expected to reach half a million in about five years.

In 2013, Gwadar Port operations were officially handed over to China ^[4] Under the contract with China, the port will be further developed into a full-scale commercial port, with an initial construction investment of $750 million.^[5] The port is said to be strategically important to China because it will enable China to more safely and reliably import oil. Currently, sixty percent of China’s oil must be transported by ship from the Persian Gulf to the only commercial port in China, Shanghai, a distance of more than 16,000 kilometres. The journey takes two to three months, during which time the ships are vulnerable to pirates, bad weather, political rivals, and other risks. Using Gwadar port instead will reduce the distance these ships must travel and will also enable oil transfers to be made year-round. ^[6]

In February 2013, Iran announced it would set up a $4 billion oil refinery in Gwadar with an estimated capacity of about 400,000 barrels per day. According to the plan, the Iranians will also construct an oil pipeline between its territory and Gwadar to transport crude oil for processing.^[7]^[8] It has also been announced that, under China’s coastal refinery plan, China will invest $12 billion in multiple projects in Gwadar and other parts of Pakistan, including construction of a refinery which will have a processing capacity of 60,000 barrels of crude oil per day.^{[citation needed]}

Banners Broker: BB Friday Q&A Webinar Notes 12/6/13

2013-12-07T03:50:00.001-08:00

Banners Broker: BB Friday Q&A Webinar Notes 12/6/13: Chris Smith: We have a huge crowd on the call today, almost at capacity. As you may know we have launched the mobile division of the compa...

Banners Broker: BB Friday Q&A Webinar 11/8/13

2013-11-09T04:35:00.001-08:00

Banners Broker: BB Friday Q&A Webinar 11/8/13: Chris Smith Speaking: One little update -- we had a little glitch with organic traffic but that's good to go. In terms of traffic...

CARBON STEEL

2013-08-24T08:02:00.000-07:00

Carbon steel is steel in which the main interstitial alloying constituent is carbon in the range of 0.12–2.0%. The American Iron and Steel Institute (AISI) defines carbon steel as the following: "Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 percent; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60."^[1]

The term "carbon steel" may also be used in reference to steel which is not stainless steel; in this use carbon steel may include alloy steels.

As the carbon percentage content rises, steel has the ability to become har

der and stronger through heat treating, however it becomes less ductile. Regardless of the heat treatment, a higher carbon content reduces weldability. In carbon steels, the higher carbon content lowers the melting point.^[2]

Carbon steel is broken down into four classes based on carbon content:

Mild and low-carbon steel

Mild steel, also called plain-carbon steel, is the most common form of steel because its price is relatively low while it provides material properties that are acceptable for many applications, more so than iron. Low-carbon steel contains approximately 0.05–0.3% carbon^[1] and mild steel contains 0.3–0.6%^[1] carbon; making it malleable and ductile. Mild steel has a relatively low tensile strength, but it is cheap and malleable; surface hardness can be increased through carburizing.^[3]

It is often used when large quantities of steel are needed, for example as structural steel. The density of mild steel is approximately 7.85 g/cm³ (7850 kg/m³ or 0.284 lb/in³)^[4] and the Young's modulus is 210 GPa (30,000,000 psi).^[5]

Low-carbon steels suffer from yield-point runout where the material has two yield points. The first yield point (or upper yield point) is higher than the second and the yield drops dramatically after the upper yield point. If a low-carbon steel is only stressed to some point between the upper and lower yield point then the surface may develop Lüder bands.^[6] Low-carbon steels contain less carbon than other steels and are easier to cold-form, making them easier to handle.^[7]

Higher carbon steels

Carbon steels which can successfully undergo heat-treatment have a carbon content in the range of 0.30–1.70% by weight. Trace impurities of various other elements can have a significant effect on the quality of the resulting steel. Trace amounts of sulfur in particular make the steel red-short, that is, brittle and crumbly at working temperatures. Low-alloy carbon steel, such as A36 grade, contains about 0.05% sulfur and melts around 1426–1538 °C (2599–2800 °F).^[8] Manganese is often added to improve the hardenability of low-carbon steels. These additions turn the material into a low-alloy steel by some definitions, but AISI's definition of carbon steel allows up to 1.65% manganese by weight.

Medium carbon steel

Approximately 0.30–0.59% carbon content.^[1] Balances ductility and strength and has good wear resistance; used for large parts, forging and automotive components.^[9]^[10]

High-carbon steel

Approximately 0.6–0.99% carbon content.^[1] Very strong, used for springs and high-strength wires.^[11]

Ultra-high-carbon steel

Approximately 1.0–2.0% carbon content.^[1] Steels that can be tempered to great hardness. Used for special purposes like (non-industrial-purpose) knives, axles or punches. Most steels with more than 1.2% carbon content are made using powder metallurgy. Note that steel with a carbon content above 2.0% is considered cast iron.

2013-08-22T09:05:00.000-07:00

Q: I have a new fabrication project for furnace racks made with 304H stainless steel and the specifications say to weld it with an E308H electrode. However, I already have some E308/E308L stick electrodes and want to know if I can use those instead? What is the difference between 308, 308L and 308H? I actually have two brands of E308 / E308L electrodes, one type has a “-16” after the 308 numbers and the other has a “-17”. What do those mean?

A: First, note that an American Welding Society (AWS) E308 classification electrode is meant for welding Austenitic types of stainless steel. Therefore, this article will only address this type. While Austenitic stainless steels are very common, there are also Ferritic, Martensitic, Duplex and Precipitation Hardening types of stainless steels.

The answer to your first question is no, an E308 / E308L stainless steel electrode is not meant for use on an AISI type 304H base metal. You do need to use an E308H electrode. The reason why will be explained shortly. Regarding your second question, “308” is a particular type of stainless steel. It is typically used to make welding electrodes and used to join common types of austenitic stainless steels, such as 301, 302, 304 and 305. The “H” and “L” designators indicate a specific composition of the electrode. More specifically, they refer to the carbon percentage in the electrode, with “H” electrodes in the high end and “L” electrodes in the low end of the electrode’s carbon range. An E308 type stainless steel electrode must have a maximum of 0.08% by weight of carbon (C). An E308H electrode however, must have at least 0.04%C, up to a maximum of 0.08% C. Carbon content in the range of 0.04 – 0.08% provides higher tensile and creep strengths at elevated temperatures. They are primarily used in industrial equipment at high service temperatures (sometimes over 2,000°F (1,093°C). Therefore, an E308H electrode would be the appropriate choice for your furnace rack project. Conversely, an E308L electrode can have no more than 0.04% C. The “L” type electrodes are sometimes referred to as “ELC” (extra low carbon) types. The lower carbon content helps minimize the damaging effects to the corrosion resistance of the heat affected zone (i.e. sensitization) caused by intergranular carbide precipitation. They are most often used for weldments that operate in severe corrosive conditions at temperatures under 800°F (427°C)

Note that a particular electrode could, and often is, dual classified. It could be classified as E308 / E308L or as E308 / E308H. The 308 grade has a broader carbon range, so if a particular electrode’s carbon content falls within the tighter L or H carbon level requirements, it also meets the more general 308 requirement. However, you could never have an E308L / E308H classified electrode, as one electrode could never have a carbon content that fits within both the low and high end of the carbon range. Note also that the “H” and “L” carbon designators can apply to other types of austenitic stainless steels besides E308. Some examples include E309H, E309L, E310H, E316H, E316L, etc.

Your third question refers to the type of coatings that are available for stainless steel shielded metal arc (stick) electrodes. There are three types of coating, a “15”, “16” and “17”. A “15” electrode has a lime based coating and is intended for DC+ polarity only. They have a lighter slag than the other two types and used for all position welding, with some electrodes of this type used primarily for vertical down welding. A “16” electrode has a titania or rutile based coating and can be used with both DC and AC polarity. Electrode sizes of 5/32 in. (4.0 mm) and smaller are often used for all welding positions. Note, there is also a “26” classification, which is the same as a “16” type coating, but for higher deposition applications and limited to the flat and horizontal position only. A “17” electrode has a silica-titania type coating and is a modification of a 16 coating, in that some of the titania is replaced with silica. They also can be used with both DC and AC polarity. Additional silicon in the coating acts as a wetting agent, having the effect of increasing puddle fluidity. This is particularly helpful with stainless steel, as it tends to have more of a sluggish weld bead than carbon steel. Seventeen type electrodes produce a flatter bead profile than the other two types and are often used for flat and horizontal position welding. However, electrode sizes of 5/32 in. (4.0 mm) and smaller can be used for all position welding. Note that with a vertical up progression, the slower freezing slag will require more of a weave technique than with a 16 type electrode.

Figure 1: Examples of “H” and “L” Type Stainless Steel Electrodes

GENERATORS MARKET IN PAKISTAN

2013-08-14T09:13:00.001-07:00

Yamaha generator are loaded with cutting edge engineering that not only ensures great performance in all operations you expect from a generator but also makes them superb in user friendliness, economy, sound levels and reliability.

Get your Yamaha generator today and experience a higher level of ease and effortless usage that only the most superior technology in the power equipment industry can offer. Yamaha generators will make your work easier, more proficient and more resourceful.

http://www.ypel.com.pk/

In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric current to flow through an external circuit. The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air, or any other source of mechanical energy. Generators provide nearly all of the power for electric power grids.
The reverse conversion of electrical energy into mechanical energy is done by an electric motor, and motors and generators have many similarities. Many motors can be mechanically driven to generate electricity and frequently make acceptable generators.
http://www.shophive.com/shophive/Generator-c-426.pakistan.html

http://www.pel.com.pk/genset.html

NEW DAMS IN PAKISTAN

2013-07-23T10:43:00.003-07:00

government of Pakistan has so far constructed 49 small dams and plans to build eight more in Rawalpindi, Jhelum, Attock and Chakwal areas in order to promote agriculture in these regions.

According to an official of the Ministry of Water and Power, construction of the six small dams is expected to be completed during the current financial year which would help irrigate around 12,310 acres of agricultural land.

The dams include Darmalak Dam (Kohat), Lawaghar and Karak Dam (Karak), Khair Bara Dam (Haripur), Jabba Khattak Dam (Nowshera) and Palai Dam (Charsadda).

“The feasibility study is being done on 11 more dams. Some of them will be built in 2011-12 while others in 2012-13,” he added.

He further said that the 12 dams would be constructed in two phases in all the four provinces with storage capacity of four MAF water. In the first phase Winder and Naulong dams will be constructed in Balochistan, Kurram Tangi in Khyber-Pakhtunkhwa, Darwat and Nai Gaj in Sindh and Ghabir Dam in Punjab.

The provincial government has allocated Rs1 billion for Punjab Agriculture Research Board and also doubled the budget for the improvement of research infrastructure.

South Korean Firm To Install 300MW Solar Power Plant In Pakistan’s Baluchistan Province

2013-07-23T10:38:00.002-07:00

Pakistan’s largest province, by area, Baluchistan is rich in mineral resources, and while it is highly strategically located near Iran and the rest of Pakistan, it remains quite underdeveloped. Over the past few years, foreign companies have forged partnerships with the provincial government for extraction of valuable minerals from the area. Now a Korean company plans to set up a solar power plant which can bring prosperity and growth to the region. K Solar Korea has signed a Memorandum of Understanding with the Baluchistan government to set up a 300 MW solar power project near the province’s largest city, Quetta. The project is expected to require $900 million investment. The project will bring relief to the province which, like the rest of the country, is suffering from acute power shortage. The project will also help the province increase self-reliance in the energy sector. While the province is the gateway to Pakistan’s much needed energy supplies from neighbouring Iran, it lags behind most parts of the country in economic development. Despite being very rich in natural resources and being the largest province in the country, Baluchistan’s contribution to Pakistan’s GDP has been less then 5% between 1973 and 2000.

Due to the predominantly tribal lifestyle of the population of the province, urbanisation has had limited penetration. The importance of infrastructure development in the region cannot be overstated. The need for sustainable energy infrastructure also stems from the fact that several foreign companies are now looking to set up exploration and extraction businesses in the province. With the development of such industries it is essential that substantial growth in the clean energy infrastructure takes place so that the pristine ecosystem of the province is preserved as much as possible.

Pakistan has taken up several large renewable energy projects in recent years as it aims for a sustainable future to counter its resource-strained present. In addition to it’s large-scale projects, the provincial governments have launched innovative measures to popularise the use of clean energy. The Punjab government distributed solar PV modules to students who faired well in their high school examinations. Such measures may eventually help the country raise an army of highly skilled clean energy professionals who could help the country out of its energy crunch.

Welding Electrodes in Pakistan

2013-02-25T10:00:00.002-08:00

DIAMOND WELD RODS (Pvt) LTD and

SHANGHAI INDUSTRIES (Pvt) LTD

ISO 9001:2008 Certified Company

Manufacturer of Welding Electrodes in Pakistan, both companies are well renowned in Pakistan and producing a variety of good quality electrodes and competing with all other manufacturers and importers especially China brand. Brand of these companies are very famous in Pakistan with affordable prices. Company main suppliers in Pakistan are:-

Aslam & Sons, Kashmir Road, Rawalpindi (051-5568274)
Bilal Traders, Lahore
Muhammad Sajid, Vehari
Muhammad Hanif, Chowk Shaheedan, Multan
Punjab Hardware, Peshawar

Comapny was established in early 80s with a firm conviction and determination of enhancing and advancing the welding line by giving it a new dimension and by introducing high standard welding electrodes and accessories. Famous brands are:-

Pak Bridge

Diamond Brand

POWER SUPPLIES

2013-02-24T08:09:00.000-08:00

To supply the electrical energy necessary for arc welding processes, a number of different power supplies can be used. The most common classification is constant current power supplies and constant voltage power supplies. In arc welding, the voltage is directly related to the length of the arc, and the current is related to the amount of heat input. Constant current power supplies are most often used for manual welding processes such as gas tungsten arc welding and shielded metal arc welding, because they maintain a relatively constant current even as the voltage varies. This is important because in manual welding, it can be difficult to hold the electrode perfectly steady, and as a result, the arc length and thus voltage tend to fluctuate. Constant voltage power supplies hold the voltage constant and vary the current, and as a result, are most often used for automated welding processes such as gas metal arc welding, flux cored arc welding, and submerged arc welding. In these processes, arc length is kept constant, since any fluctuation in the distance between the wire and the base material is quickly rectified by a large change in current. For example, if the wire and the base material get too close, the current will rapidly increase, which in turn causes the heat to increase and the tip of the wire to melt, returning it to its original separation distance.[1]

The direction of current used in arc welding also plays an important role in welding. Consumable electrode processes such as shielded metal arc welding and gas metal arc welding generally use direct current, but the electrode can be charged either positively or negatively. In welding, the positively charged anode will have a greater heat concentration and, as a result, changing the polarity of the electrode has an impact on weld properties. If the electrode is positively charged, it will melt more quickly, increasing weld penetration and welding speed. Alternatively, a negatively charged electrode results in more shallow welds.[2] Non-consumable electrode processes, such as gas tungsten arc welding, can use either type of direct current (DC), as well as alternating current (AC). With direct current however, because the electrode only creates the arc and does not provide filler material, a positively charged electrode causes shallow welds, while a negatively charged electrode makes deeper welds.[3] Alternating current rapidly moves between these two, resulting in medium-penetration welds. One disadvantage of AC, the fact that the arc must be re-ignited after every zero crossing, has been addressed with the invention of special power units that produce a square wave pattern instead of the normal sine wave, eliminating low-voltage time after the zero crossings and minimizing the effects of the problem.[4]

Duty cycle is a welding equipment specification which defines the number of minutes, within a 10 minute period, during which a given arc welder can safely be used. For example, an 80 A welder with a 60% duty cycle must be "rested" for at least 4 minutes after 6 minutes of continuous welding.[5] Failure to observe duty cycle limitations could damage the welder. Commercial- or professional-grade welders typically have a 100% duty cycle.

Welding Joints

2011-02-24T20:39:00.000-08:00

Welding joints are formed by welding two or more workpieces, made of metals or plastics, according to a particular geometry. The most common types are butt and lap joints; there are various lesser used welding joints including flange and corner joints.

Butt welds

Butt welds are welds where two pieces of metal are joined at surfaces that are at 90 degree angles to the surface of at least one of the other pieces.^[1] These types of welds require only some preparation and are used with thin sheet metals that can be welded with a single pass ^[2]. Common issues that can weaken a butt weld are the entrapment of slag, excessive porosity, or cracking. For strong welds, the goal is to use the least amount of welding material possible. Butt welds are prevalent in automated welding processes, such as submerged-arc welding, due to their relative ease of preparation.^[3] When metals are welded without human guidance, there is no operator to make adjustments for non-ideal joint preparation. Because of this necessity, butt welds can be utilized for their simplistic design to be fed through automated welding machines efficiently.

Types

Butt joint geometries

There are many types of butt welds, but all fall within one of these categories: single welded butt joints, double welded butt joint, and open or closed butt joints. A single welded butt joint is the name for a joint that has only been welded from one side. A double welded butt joint is created when the weld has been welded from both sides. With double welding, the depths of each weld can vary slightly. A closed weld is a type of joint in which the two pieces that will be joined are touching during the welding process. An open weld is the joint type where the two pieces have a small gap in between them during welding.

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Square butt joints

The square-groove is a butt welding joint with the two pieces being flat and parallel to each other. This joint is simple to prepare, economical to use, and provides satisfactory strength, but is limited by joint thickness. The closed square butt weld is a type of square-groove joint with no spacing in between the pieces. This joint type is common with gas and arc welding.

For thicker joints, the edge of each member of the joint must be prepared to a particular geometry to provide accessibility for welding and to ensure the desired weld soundness and strength. The opening or gap at the root of the joint and the included angle of the groove should be selected to require the least weld metal necessary to give needed access and meet strength requirements.

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Bevel butt joints

Single-bevel butt welds are welds where one piece in the joint is beveled and the other surface is perpendicular to the plane of the surface. These types of joints are used where adequate penetration cannot be achieved with a square-groove and the metals are to be welded in the horizontal position ^[4]. Double-bevel butt welds are common in arc and gas welding processes. In this type both sides of one of the edges in the joint are beveled.

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V-joints

Single-V butt welds are similar to a bevel joint, but instead of only one side having the beveled edge, both sides of the weld joint are beveled. In thick metals, and when welding can be performed from both sides of the work piece, a double-V joint is used. When welding thicker metals, a double-V joint requires less filler material because there are two narrower V-joints compared to a wider single-V joint. Also the double-V joint helps compensate for warping forces. With a single-V joint, stress tends to warp the piece in one direction when the V-joint is filled, but with a double-V-joint, there are welds on both sides of the material, having opposing stresses, straightening the material.

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J-joints

Single-J butt welds are when one piece of the weld is in the shape of a J that easily accepts filler material and the other piece is square. A J-groove is formed either with special cutting machinery or by grinding the joint edge into the form of a J. Although a J-groove is more difficult and costly to prepare than a V-groove, a single J-groove on metal between a half an inch and three quarters of an inch thick provides a stronger weld that requires less filler material. Double-J butt welds have one piece that has a J shape from both directions and the other piece is square.

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U-joints

Single-U butt welds are welds that have both edges of the weld surface shaped like a J, but once they come together, they form a U. Double-U joints have a U formation on both the top and bottom of the prepared joint. U-joints are the most expensive edge to prepare and weld. They are usually used on thick base metals where a V-groove would be at such a extreme angle, that it would cost too much to fill.

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Others

Thin sheet metals are often flanged to produce edge-flange or corner-flange welds. These welds are typically made without the addition of filler metal because the flange melts and provides all the filler needed. Pipes and tubing can be made from rolling and welding together strips, sheets, or plates of material.^[5]

Flare-groove joints are used for welding metals that, because of their shape, form a convenient groove for welding, such as a pipe against a flat surface.

The Tee Butt Weld is formed when two bars or sheets are joined perpendicular to each other in the form of a T shape. This weld is made from the resistance butt welding process.

Selection of the right weld joint depends on the thickness and process used. The square welds are the most economical for pieces thinner than 3/8”, because they don’t require the edge to be prepared.^[6] Double-groove welds are the most economical for thicker pieces because they require less weld material and time. The use of fusion welding is common for closed single-bevel, closed single J, open single J, and closed double J butt joints. The use of gas and arc welding is ideal for double-bevel, closed double-bevel, open double-bevel, single-bevel, and open single-bevel butt welds.

Below are listed ideal joint thicknesses for the various types of butt welding joints. When the thickness of a butt weld is defined it is measured at the thinner part and does not compensate for the weld reinforcement.

Workpiece thickness limits per joint type^{[citation needed]}
Joint type	Thickness
Square joint	Up to ¹⁄₄ in (0.64 cm)
Single-bevel joint	³⁄₁₆–³⁄₈ in (0.48–0.95 cm)
Double-bevel joint	Over ³⁄₈ in (0.95 cm)
Single-V joint	Up to ³⁄₄ in (1.9 cm)
Double-V joint	Over ³⁄₄ in (1.9 cm)
Single-J joint	¹⁄₂–³⁄₄ in (1.3–1.9 cm)
Double-J joint	Over ³⁄₄ in (1.9 cm)
Single-U joint	Up to ³⁄₄ in (1.9 cm)
Double-U joint	Over ³⁄₄ in (1.9 cm)
Flange (edge of corner)	Sheet metals less than 12 gauge^{[clarification needed]}
Flare groove	All thickness

Cruciform

Diagram of a cruciform joint between 3 plates of metal

A cruciform joint is a specific joint in which four spaces are created by the welding of three plates of metal at right angles. In the American Bureau of Shipping Rules for Steel Vessels, cruciform joints may be considered a double barrier if the two substances requiring a double barrier are in opposite corners diagonally. Double barriers are often required to separate oil and seawater,chemicals and potable water, etc.^[7]

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Plate edge preparation

In common welding practices, the welding surface needs to be prepared to ensure the strongest weld possible. Preparation is needed for all forms of welding and all types of joints. Generally, butt welds require very little preparation, but some is still needed for the best results. Plate edges can be prepared for butt joints in various ways, but the five most common techniques are oxyacetylene cutting (oxy-fuel welding and cutting), machining, chipping, grinding, and air carbon-arc cutting or gouging. Each technique has unique advantages to their use.

For steel materials, oxyacetylene cutting is the most common form of preparation. This technique is advantageous because of its speed, low cost, and adaptability. Machining is the most effective for reproducibility and mass production of parts. Preparation of J or U joints is common prepared by machining due to the need for high accuracy. The chipping method is used to prepare parts that were produced by casting. The use of grinding to prepare pieces is reserved for small sections that cannot be prepared by other methods. Air carbon arc welding is common in industries that work with stainless steels, cast iron, or ordinary carbon steel.^[8]

Welding Procedure Specification

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A Welding Procedure Specification (WPS) is a formal document describing weldingprocedures. The purpose of the document is to guide welders to the accepted procedures so that repeatable and trusted welding techniques are used. A WPS is developed for each material alloy and for each welding type used. Specific codes and/or engineering societies are often the driving force behind the development of a company's WPS. A WPS is supported by a Procedure Qualification Record (PQR or WPQR). A PQR is a record of a test weld performed and tested (more rigorously) to ensure that the procedure will produce a good weld. Individual welders are certified with a qualification test documented in a Welder Qualification Test Record (WQTR) that shows they have the understanding and demonstrated ability to work within the specified WPS.

The following are definitions for WPS and PQR found in various codes and standards:

According to the American Welding Society (AWS), a WPS provides in detail the required welding variables for specific application to assure repeatability by properly trained welders. The AWS defines welding PQR as a record of welding variables used to produce an acceptable test weldment and the results of tests conducted on the weldment to qualify a Welding Procedure Specification.

The American Society of Mechanical Engineers (ASME) similarly defines a WPS as a written document that provides direction to the welder or welding operator for making production welds in accordance with Code requirements.^[1] ASME also defines welding PQR as a record of variables recorded during the welding of the test coupon. The record also contains the test results of the tested specimens.

In Europe, the European Committee for Standardization (CEN) has adopted the ISO standards on welding procedure qualification (ISO 15607 to ISO 15614) and on welder qualification (ISO 9606), with the exception of qualification for steel welders, where a new version of the old european EN 287-1 standard still applies. EN ISO 15706 defines a WPS as "A document that has been qualified by one of the methods described in clause 6 and provides the required variables of the welding procedure to ensure repeatability during production welding". The same standard defines a Welding Procedure Qualification Record (WPQR) as "Record comprising all necessary data needed for qualification of a preliminary welding procedure specification". ^[2] In addition to the standard WPS qualification procedure specified in ISO 15614, the ISO 156xx series of standards provides also for alternative WPS approval methods. These include: Tested welding consumables (ISO 15610),Previous welding experience (ISO 15611), Standard welding procedure (ISO 15612) and Preproduction welding test (ISO 15613).

In the oil and gas pipeline sector, the American Petroleum Institute API 1104 standard is used almost exclusively worldwide. API 1104 accepts the definitons of the American Welding Society code AWS A3.0.^[3]

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Gas Welding

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The most common gas welding process is oxyfuel welding, also known as oxyacetylene welding. It is one of the oldest and most versatile welding processes, but in recent years it has become less popular in industrial applications. It is still widely used for welding pipes and tubes, as well as repair work. It is also frequently well-suited, and favored, for fabricating some types of metal-based artwork. Oxyfuel equipment is versatile not only because it is preferred for some sorts of iron or steel welding but also because it lends itself to brazing, braze-welding, metal heating (for bending and forming), the loosening of corroded nuts and bolts, and also is the ubiquitous means for oxy-fuel cutting of ferrous metals.

The equipment is relatively inexpensive and simple, generally employing the combustion ofacetylene in oxygen to produce a welding flame temperature of about 3100 °C. The flame, since it is less concentrated than an electric arc, causes slower weld cooling, which can lead to greater residual stresses and weld distortion, though it eases the welding of high alloy steels. A similar process, generally called oxyfuel cutting, is used to cut metals.^[6] Other gas welding methods, such as air acetylene welding, oxygen hydrogen welding, and pressure gas welding are quite similar, generally differing only in the type of gases used. A water torch is sometimes used for precision welding of small items such as jewelry. Gas welding is also used in plastic welding, though the heated substance is air, and the temperatures are much lower.

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Resistance

Resistance welding involves the generation of heat by passing current through the resistance caused by the contact between two or more metal surfaces. Small pools of molten metal are formed at the weld area as high current (1000–100,000 A) is passed through the metal. In general, resistance welding methods are efficient and cause little pollution, but their applications are somewhat limited and the equipment cost can be high.

Spot welder

Spot welding is a popular resistance welding method used to join overlapping metal sheets of up to 3 mm thick. Two electrodes are simultaneously used to clamp the metal sheets together and to pass current through the sheets. The advantages of the method include efficient energy use, limited workpiece deformation, high production rates, easy automation, and no required filler materials. Weld strength is significantly lower than with other welding methods, making the process suitable for only certain applications. It is used extensively in the automotive industry—ordinary cars can have several thousand spot welds made by industrial robots. A specialized process, called shot welding, can be used to spot weld stainless steel.

Like spot welding, seam welding relies on two electrodes to apply pressure and current to join metal sheets. However, instead of pointed electrodes, wheel-shaped electrodes roll along and often feed the workpiece, making it possible to make long continuous welds. In the past, this process was used in the manufacture of beverage cans, but now its uses are more limited. Other resistance welding methods include flash welding, projection welding, and upset welding.^[25]

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Energy beam

Energy beam welding methods, namely laser beam welding and electron beam welding, are relatively new processes that have become quite popular in high production applications. The two processes are quite similar, differing most notably in their source of power. Laser beam welding employs a highly focused laser beam, while electron beam welding is done in a vacuum and uses an electron beam. Both have a very high energy density, making deep weld penetration possible and minimizing the size of the weld area. Both processes are extremely fast, and are easily automated, making them highly productive. The primary disadvantages are their very high equipment costs (though these are decreasing) and a susceptibility to thermal cracking. Developments in this area include laser-hybrid welding, which uses principles from both laser beam welding and arc welding for even better weld properties, and X-ray welding.^[26]

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Solid-state

Like the first welding process, forge welding, some modern welding methods do not involve the melting of the materials being joined. One of the most popular, ultrasonic welding, is used to connect thin sheets or wires made of metal or thermoplastic by vibrating them at high frequency and under high pressure. The equipment and methods involved are similar to that of resistance welding, but instead of electric current, vibration provides energy input. Welding metals with this process does not involve melting the materials; instead, the weld is formed by introducing mechanical vibrations horizontally under pressure. When welding plastics, the materials should have similar melting temperatures, and the vibrations are introduced vertically. Ultrasonic welding is commonly used for making electrical connections out of aluminum or copper, and it is also a very common polymer welding process.

Another common process, explosion welding, involves the joining of materials by pushing them together under extremely high pressure. The energy from the impact plasticizes the materials, forming a weld, even though only a limited amount of heat is generated. The process is commonly used for welding dissimilar materials, such as the welding of aluminum with steel in ship hulls or compound plates. Other solid-state welding processes include co-extrusion welding, cold welding, diffusion welding, exothermic welding, friction welding (including friction stir welding), high frequency welding, hot pressure welding, induction welding, and roll welding.^[27]

Quality

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Most often, the major metric used for judging the quality of a weld is its strength and the strength of the material around it. Many distinct factors influence this, including the welding method, the amount and concentration of energy input, the base material, the filler material, the flux material, the design of the joint, and the interactions between all these factors. To test the quality of a weld, either destructive ornondestructive testing methods are commonly used to verify that welds are defect-free, have acceptable levels of residual stresses and distortion, and have acceptable heat-affected zone (HAZ) properties. Welding codes and specifications exist to guide welders in proper welding technique and in how to judge the quality of welds.

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Heat-affected zone

The blue area results from oxidation at a corresponding temperature of 600 °F (316 °C). This is an accurate way to identify temperature, but does not represent the HAZ width. The HAZ is the narrow area that immediately surrounds the welded base metal.

The effects of welding on the material surrounding the weld can be detrimental—depending on the materials used and the heat input of the welding process used, the HAZ can be of varying size and strength. The thermal diffusivity of the base material plays a large role—if the diffusivity is high, the material cooling rate is high and the HAZ is relatively small. Conversely, a low diffusivity leads to slower cooling and a larger HAZ. The amount of heat injected by the welding process plays an important role as well, as processes like oxyacetylene welding have an unconcentrated heat input and increase the size of the HAZ. Processes like laser beam welding give a highly concentrated, limited amount of heat, resulting in a small HAZ. Arc welding falls between these two extremes, with the individual processes varying somewhat in heat input.^[31]^[32] To calculate the heat input for arc welding procedures, the following formula can be used:

where Q = heat input (kJ/mm), V = voltage (V), I = current (A), and S = welding speed (mm/min). The efficiency is dependent on the welding process used, with shielded metal arc welding having a value of 0.75, gas metal arc welding and submerged arc welding, 0.9, and gas tungsten arc welding, 0.8.^[33]

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Defects

Main article: Welding defect

There are many types of defects that can occur depending on the material and welding process. Types of defects include cracks, distortion, gas inclusions (porosity), non-metallic inclusions, lack of fusion, incomplete penetration, lamellar tearing, and undercutting.

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Weldability

Main article: Weldability

The quality of a weld is also dependent on the combination of materials used for the base material and the filler material. Not all metals are suitable for welding, and not all filler metals work well with acceptable base materials.

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Unusual conditions

Underwater welding

While many welding applications are done in controlled environments such as factories and repair shops, some welding processes are commonly used in a wide variety of conditions, such as open air, underwater, and vacuums (such as space). In open-air applications, such as construction and outdoors repair, shielded metal arc welding is the most common process. Processes that employ inert gases to protect the weld cannot be readily used in such situations, because unpredictable atmospheric movements can result in a faulty weld. Shielded metal arc welding is also often used in underwater welding in the construction and repair of ships, offshore platforms, and pipelines, but others, such as flux cored arc welding and gas tungsten arc welding, are also common. Welding in space is also possible—it was first attempted in 1969 by Russian cosmonauts, when they performed experiments to test shielded metal arc welding, plasma arc welding, and electron beam welding in a depressurized environment. Further testing of these methods was done in the following decades, and today researchers continue to develop methods for using other welding processes in space, such as laser beam welding, resistance welding, and friction welding. Advances in these areas may be useful for future endeavours similar to the construction of the International Space Station, which could rely on welding for joining in space the parts that were manufactured on Earth.^[34]

Geometry (Welding Joints)

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Welds can be geometrically prepared in many different ways. The five basic types of weld joints are the butt joint, lap joint, corner joint, edge joint, and T-joint (a variant of this last is the cruciform joint). Other variations exist as well—for example, double-V preparation joints are characterized by the two pieces of material each tapering to a single center point at one-half their height. Single-U and double-U preparation joints are also fairly common—instead of having straight edges like the single-V and double-V preparation joints, they are curved, forming the shape of a U. Lap joints are also commonly more than two pieces thick—depending on the process used and the thickness of the material, many pieces can be welded together in a lap joint geometry.^[28]

Often, particular joint designs are used exclusively or almost exclusively by certain welding processes. For example, resistance spot welding, laser beam welding, and electron beam welding are most frequently performed on lap joints. However, some welding methods, like shielded metal arc welding, are extremely versatile and can weld virtually any type of joint. Additionally, some processes can be used to make multipass welds, in which one weld is allowed to cool, and then another weld is performed on top of it. This allows for the welding of thick sections arranged in a single-V preparation joint, for example.^[29]

The cross-section of a welded butt joint, with the darkest gray representing the weld or fusion zone, the medium gray the heat-affected zone, and the lightest gray the base material.

After welding, a number of distinct regions can be identified in the weld area. The weld itself is called the fusion zone—more specifically, it is where the filler metal was laid during the welding process. The properties of the fusion zone depend primarily on the filler metal used, and its compatibility with the base materials. It is surrounded by the heat-affected zone, the area that had its microstructure and properties altered by the weld. These properties depend on the base material's behavior when subjected to heat. The metal in this area is often weaker than both the base material and the fusion zone, and is also where residual stresses are found.^[30]

Laser beam welding

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Laser beam welding (LBW) is a welding technique used to join multiple pieces of metal through the use of a laser. The beam provides a concentrated heat source, allowing for narrow, deep welds and high welding rates. The process is frequently used in high volume applications, such as in the automotive industry.

Operation

Like electron beam welding (EBW), laser beam welding has high power density (on the order of 1 Megawatt/cm²(MW)) resulting in small heat-affected zones and high heating and cooling rates. The spot size of the laser can vary between 0.2 mm and 13 mm, though only smaller sizes are used for welding. The depth of penetration is proportional to the amount of power supplied, but is also dependent on the location of the focal point: penetration is maximized when the focal point is slightly below the surface of the workpiece.

A continuous or pulsed laser beam may be used depending upon the application. Milliseconds long pulses are used to weld thin materials such as razor blades while continuous laser systems are employed for deep welds.

LBW is a versatile process, capable of welding carbon steels, HSLA steels, stainless steel, aluminum, and titanium. Due to high cooling rates, cracking is a concern when welding high-carbon steels. The weld quality is high, similar to that of electron beam welding. The speed of welding is proportional to the amount of power supplied but also depends on the type and thickness of the workpieces. The high power capability of gas lasers make them especially suitable for high volume applications. LBW is particularly dominant in the automotive industry.^[1]^[2]

Some of the advantages of LBW in comparison to EBW are as follows: the laser beam can be transmitted through air rather than requiring a vacuum, the process is easily automated with robotic machinery, x-rays are not generated, and LBW result in higher quality welds.

A derivative of LBW, laser-hybrid welding, combines the laser of LBW with an arc welding method such as gas metal arc welding. This combination allows for greater positioning flexibility, since GMAW supplies molten metal to fill the joint, and due to the use of a laser, increases the welding speed over what is normally possible with GMAW. Weld quality tends to be higher as well, since the potential for undercutting is reduced.^[3]

[edit]
Equipment

The two types of lasers commonly used in are solid-state lasers and gas lasers (especially carbon dioxide lasers and Nd:YAG lasers).
The first type uses one of several solid media, including synthetic ruby and chromium in aluminum oxide, neodymium in glass (Nd:glass), and the most common type, crystal composed of yttrium aluminum garnet doped with neodymium (Nd:YAG).
Gas lasers use mixtures of gases like helium, nitrogen, and carbon dioxide (CO2 laser) as a medium.
Regardless of type, however, when the medium is excited, it emits photons and forms the laser beam.

[edit]
Solid state laser

Solid-state lasers operate at wavelengths on the order of 1 micrometer, much shorter than gas lasers, and as a result require that operators wear special eyewear or use special screens to prevent retina damage. Nd:YAG lasers can operate in both pulsed and continuous mode, but the other types are limited to pulsed mode. The original and still popular solid-state design is a single crystal shaped as a rod approximately 20 mm in diameter and 200 mm long, and the ends are ground flat. This rod is surrounded by a flash tube containing xenon or krypton. When flashed, a pulse of light lasting about two milliseconds is emitted by the laser. Disk shaped crystals are growing in popularity in the industry, and flashlamps are giving way to diodes due to their high efficiency. Typical power output for ruby lasers is 10–20 W, while the Nd:YAG laser outputs between 0.04–6,000 W. To deliver the laser beam to the weld area, fiber optics are usually employed.

[edit]
Gas laser

Gas lasers use high-voltage, low-current power sources to supply the energy needed to excite the gas mixture used as a lasing medium. These lasers can operate in both continuous and pulsed mode, and the wavelength of the laser beam is 10.6 μm. Fiber optic cable absorbs and is destroyed by this wavelength, so a rigid lens and mirror delivery system is used. Power outputs for gas lasers can be much higher than solid-state lasers, reaching 25 kW.^[4]

[edit]
Fiber laser

In fiber lasers, the gain medium is the optical fiber itself. They are capable of power up to 50 kW and are increasingly being used for robotic industrial welding.

Plastic Sealing/Welding Technologies

2010-03-11T20:23:00.000-08:00

The purpose of this article is to outline the most commonly used heat sealing technologies in the Industrial Fabrics market using Engineered Textiles with Polymer coatings. Advancements in industrial materials/fabrics, such as greater heat resistance and strength, stronger weaves and coatings, and consistency roll to roll have opened the market up to new applications. These new applications have created a greater demand for sealing technologies that deliver more consistency and speed.

For example, we now have flexible hurricane shields, inflatable aircraft slides, fire resistant clothing, and countless new military products. Applications also exist in the Automotive industry, Photography products, Media storage,and retail promotion.

Common Product examples

Loose leaf binders, Checkbooks, Passport holders, and Shower curtains.

Radio Frequency Welding (RF)

Radio frequency welding is a very mature technology that has been around since the 1940s. Two pieces of material are placed on a table press that applies pressure to both surface areas. Dies are used to direct the welding process. When the press comes together, high frequency waves (usually 27.12 MHz) are passed through the small area between the die and the table where the weld takes place. This high frequency (radio frequency) field causes the molecules in certain materials to move and get hot, and the combination of this heat under pressure causes the weld to take the shape of the die. RF welding is fast. This type of welding is used to connect polymer films used in a variety of industries where a strong consistent leak-proof seal is required. In the Industrial Fabrics Industry, RF is most often used to fuse/weld vinyl (PVC) and polyurethane(PU) coated fabrics. This is a very consistent method of welding.

Please note that Exposure conditions experienced by RF heater operators can cause elevated body temperature, eye irritation, RF burns, and some neurological problems. To reduce exposure conditions the use of Electromagnetic shielding should be used as much as possible without hindering the manufacturing process.

The most common materials used in Radio Frequency Welding are Thermoplastics such as PVC and Polyurethane. It is also possible to weld other polymers such as Nylon, PET, EVA and some ABS Resins.

Hot Air/wedge Welding

Hot air welding uses hot air or a wedge to heat the coating on the fabric where it is to be bonded together. A Nozzle or heated wedge is positioned between two rollers that pull the material through the machine. As the material is pulled through the machine, hot air is applied to the surfaces to be fused together. Pressure from the rollers and heat form the hot air cause the plastic to fuse as the plastic cools. Like Radio Frequency RF—thermal welding is fast.

Ultrasonic Welding

Ultrasonic welding like radio frequency welding creates heat through friction, however,the heat is created between two layers of material rather than within the material itself. It uses a vibrating tool (die) to create the heat. Ultrasonic can be used on almost all plastic material. It is the fastest heat sealing technology available. It is a rather new technology for Industrial Fabric applications, however it can be more costly to weld large surface areas.

Oxy-fuel Welding and Cutting

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Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the U.S.) and oxy-fuel cutting are processes that use fuel gases and oxygen to weld and cut metals, respectively. French engineers Edmond Fouche and Charles Picard became the first to develop an oxygen-acetylene welding machine in 1903.^[1]

Oxy-fuel is one of the oldest welding processes, though in recent years it has become less popular in industrial applications. However, it is still widely used for welding pipes and tubes, as well as repair work. It is also frequently well-suited, and favored, for fabricating some types of metal-based artwork. Oxyfuel equipment is versatile, lending itself not only to some sorts of iron or steel welding but also to brazing, braze-welding, metal heating (for bending and forming), and also oxyfuel cutting.

In oxy-fuel welding, a welding torch is used to weld metals. Welding metal results when two pieces are heated to a temperature that produces a shared pool of molten metal. The molten pool is generally supplied with additional metal called filler. Filler material depends upon the metals to be welded.

In oxy-fuel cutting, a cutting torch is used to heat metal to kindling temperature. A stream of oxygen then trained on the metal combines with the metal which then flows out of the cut (kerf) as an oxide slag ^[2].

Torches that do not mix fuel with oxygen (combining, instead, atmospheric air) are not considered oxy-fuel torches and can typically be identified by a single tank (Oxy-fuel welding/cutting generally requires two tanks, fuel and oxygen). Most metals cannot be melted with a single-tank torch. As such, single tank torches are typically used only for soldering and brazing, rather than welding.

Uses

Oxy-gas torches are used for or have been used for:

Welding metal: see below.
Cutting metal: see below.
Also, oxy-hydrogen flames are used:
- In Stone Work for "flaming" where the stone is heated and a top layer crackles and breaks. A steel circular brush is attached to an angle grinder and used to remove the first layer leaving behind a bumpy surface similar to hammered bronze.
- In the glass industry for "fire polishing".
- In jewelry production for "water welding" using a "water torch". [1].
- Formerly, to heat lumps of quicklime to obtain a bright white light called limelight, in theatres or optical ("magic") lanterns.
- Formerly, in platinum works, as platinum is only fusible in the oxy-hydrogen flame and in an electric furnace.

[edit]
Apparatus

The apparatus used in gas welding consists basically of an oxygen source and a fuel gas source (usually cylinders), two pressure regulatorsand two flexible hoses (one of each for each cylinder), and a torch. This sort of torch can also be used for soldering and brazing. The cylinders are often carried in a special wheeled trolley.

There have been examples of oxyhydrogen cutting sets with small (scuba-sized) gas cylinders worn on the user's back in a backpack harness, for rescue work and similar.

There are also examples of pressurized liquid fuel cutting torches, usually using gasoline. These are used for their increased portability.

Welding Procedure Specification

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A Welding Procedure Specification (WPS) is a formal document describing welding procedures. According to the American Welding Society (AWS), a WPS provides in detail the required welding variables for specific application to assure repeatability by properly trainedwelders and welding operators.

The American Society For Mechanical Engineers (ASME) similarly defines Welding Procedure Specification (WPS) as a written document that provides direction to the welder or welding operator for making production welds in accordance with Code requirements.

The American Welding Society defines welding Procedure Qualification Record (PQR) as a record of welding variables used to produce an acceptable test weldment and the results of tests conducted on the weldment to qualify a Welding Procedure Specification. The American Society of Mechanical Engineers (ASME), similarly defines welding Procedure Qualification Record (PQR) as a record of variables recorded during the welding of the test coupon. The record also contains the test results of the tested specimens.

Covered Arc-Welding Electrode

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A covered arc welding electrode includes a steel core wire and a flux which is applied to the outside periphery of said steel core wire. The welding electrode can form a superior crack-resisting weld zone even if fluctuating stresses are continually applied to a base metal while the base metal is welded. The flux includes 40 to 60% metal carbonate, 10 to 25% metal fluoride and 4 to 25 metal oxide by weight. The flux comprises 24 to 32% of the total weight of said electrode. The composition of the welding electrode includes 0.005 to 0.05% carbon, 0.1 to 1.1% silicon, 1.5 to 2.5% manganese, not more than 0.007% sulfur and not more than 0.25% nickel by weight and the manganese/sulfur ratio is more than or equal to 350 to 1. In addition, the welding electrode can include 0.01 to 0.10% rare earth metal by weight. In which case, the Mn content may be 1.0 to 2.5% by weight and the manganese/sulfur ratio may be more than or equal to 270 to 1. In addition, the composition of the welding electrode can include titanium and zirconium, the total content of which may be less than or equal to 1.2% the total weight of the electrode, and/or aluminum and magnesium, the total content of which may be less than or equal to 1.2% of the total weight of the electrode.

1. A covered arc welding electrode comprising:
a flux including 40 to 60% metal carbonate, 10 to 25% metal fluoride and 4 to 25% metal oxide by weight; and a steel core wire, onto the outer periphery of which said flux is applied so as to comprise 24 to 32% of the total weight of said electrode, said electrode as a whole being comprised of 0.005 to 0.05% carbon, 0.1 to 1.1% silicon, 1.5 to 2.5% manganese, not more than 0.007% sulfur and not more than 0.25% nickel by weight and in which the manganese/sulfur ratio is more than or equal to 350 to 1.

2. A covered arc-welding electrode as set forth in claim 1, further comprising titanium and zirconium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

3. A covered arc-welding electrode as set forth in claim 2, further comprising aluminum and magnesium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

4. A covered arc-welding electrode as set forth in claim 1, further comprising aluminum and magnesium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

5. A covered arc-welding electrode comprising:
a flux including by weight 40 to 60% metal carbonate, 10 to 25% metal fluoride and 4 to 25% metal oxide; and a steel core wire, onto the outer periphery of which said flux is applied so as to comprise 24 to 32% of the total weight of said electrode;
said electrode as a whole being comprised of 0.005 to 0.05% carbon, 0.1 to 1.1% silicon, 1.0 to 2.5% manganese, not more than 0.007% sulfur, not more than 0.25% nickel and 0.01 to 0.10% rare earth metal by weight and in which the manganese/sulfur ratio is more than or equal to 270 to 1.

6. A covered arc-welding electrode as set forth in claim 5, further comprising titanium and zirconium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

7. A covered arc-welding electrode as set forth in claim 6, further comprising aluminum and magnesium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

8. A covered arc-welding electrode as set forth in claim 5, further comprising aluminum and magnesium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

Safety Issues

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Welding can be a dangerous and unhealthy practice without the proper precautions; however, with the use of new technology and proper protection the risks of injury or death associated with welding can be greatly reduced.

[edit] Heat and sparks
Because many common welding procedures involve an open electric arc or flame, the risk of burns is significant. To prevent them, welders wear protective clothing in the form of heavy leather gloves and protective long sleeve jackets to avoid exposure to extreme heat, flames, and sparks.

[edit] Eye damage
The brightness of the weld area leads to a condition called arc eye in which ultraviolet light causes inflammation of the cornea and can burn the retinas of the eyes. Goggles and helmets with dark face plates are worn to prevent this exposure and, in recent years, new helmet models have been produced featuring a face plate that self-darkens upon exposure to high amounts of UV light. To protect bystanders, transparent welding curtains often surround the welding area. These curtains, made of a polyvinyl chloride plastic film, shield nearby workers from exposure to the UV light from the electric arc, but should not be used to replace the filter glass used in helmets.[26]
Those dark face plates must be much darker than those in sunglasses or blowtorching goggles. Sunglasses and blowtorching goggles are not adequate for arc welding protection.
In 1970, a Swedish doctor, Åke Sandén, developed a new type of welding goggles that used a multilayer interference filter to block most of the light from the arc. He had observed that most welders could not see well enough, with the mask on, to strike the arc, so they would flip the mask up, then flip it down again once the arc was going: this exposed their naked eyes to the intense light for a while. By coincidence, the spectrum of an electric arc has a notch in it, which coincides with the yellow sodium line. Thus, a welding shop could be lit by sodium vapor lamps or daylight, and the welder could see well to strike the arc. The Swedish government required these masks to be used for arc welding, but they were not used in the United States. They may have disappeared.[27]

[edit] Inhaled matter
Welders are also often exposed to dangerous gases and particulate matter. Processes like flux-cored arc welding and shielded metal arc welding produce smoke containing particles of various types of oxides. The size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger. Additionally, many processes produce various gases (most commonly carbon dioxide and ozone, but others as well) that can prove dangerous if ventilation is inadequate. Furthermore, the use of compressed gases and flames in many welding processes pose an explosion and fire risk; some common precautions include limiting the amount of oxygen in the air and keeping combustible materials away from the workplace.[28]

[edit] Interference with pacemakers
Certain welding machines which use a high frequency AC current component have been found to affect pacemaker operation when within 2 meters of the power unit and 1 meter of the weld site[29].

A BASIC GUIDE OF ARC WELDING ELECTRODES

Best Institutes of Welding Learning & Training

WHAT YOU WILL LEARN:

KENTUCKY WELDING INSTITUTE

PLC Control Lathe Type Automatic Girth Welder

PLC control Lathe type automatic girth welder

Shielded metal arc welding

Development[edit]

Operation[edit]

Quality[edit]

Safety[edit]

Application and materials[edit]

Equipment[edit]

Power supply[edit]

Electrode[edit]

Process variations[edit]

China–Pakistan Economic Corridor

Strategic importance[edit]

Gwadar - A Jewel in Crown

Banners Broker: BB Friday Q&A Webinar Notes 12/6/13

Banners Broker: BB Friday Q&A Webinar 11/8/13

CARBON STEEL

Mild and low-carbon steel

Higher carbon steels

GENERATORS MARKET IN PAKISTAN

NEW DAMS IN PAKISTAN

South Korean Firm To Install 300MW Solar Power Plant In Pakistan’s Baluchistan Province

Welding Electrodes in Pakistan

POWER SUPPLIES

Welding Joints

Butt welds

Types

[edit]Square butt joints

[edit]Bevel butt joints

[edit]V-joints

[edit]J-joints

[edit]U-joints

[edit]Others

Cruciform

[edit]Plate edge preparation

Welding Procedure Specification

[edit]

Gas Welding

[edit]Resistance

[edit]Energy beam

[edit]Solid-state

Quality

[edit]Heat-affected zone

[edit]Defects

[edit]Weldability

[edit]Unusual conditions

Geometry (Welding Joints)

Laser beam welding

Operation

[edit]Equipment

[edit]Solid state laser

[edit]Gas laser

[edit]Fiber laser

Plastic Sealing/Welding Technologies

Common Product examples

Radio Frequency Welding (RF)

Hot Air/wedge Welding

Ultrasonic Welding

Oxy-fuel Welding and Cutting

Uses

[edit]Apparatus

Welding Procedure Specification

Covered Arc-Welding Electrode

Safety Issues

[edit]
Square butt joints

[edit]
Bevel butt joints

[edit]
V-joints

[edit]
J-joints

[edit]
U-joints

[edit]
Others

[edit]
Plate edge preparation

[edit]
Resistance

[edit]
Energy beam

[edit]
Solid-state

[edit]
Heat-affected zone

[edit]
Defects

[edit]
Weldability

[edit]
Unusual conditions

[edit]
Equipment

[edit]
Solid state laser

[edit]
Gas laser

[edit]
Fiber laser

[edit]
Apparatus