Non Destructive Testing & Welding GTAW, GMAW, SMAW, SAW, FCAW

Welding Spatter

2014-08-09T05:53:00.002-07:00

Weld spatter is an all-too-common and persistent issue ? one of those things that you hate, but you figure you just have to deal with. But that’s not necessarily true, because there are actually many ways to control it. Weld spatter consists of small balls of molten metal that are created near the welding arc that stick to the gas shroud of the weld gun and block gas flow. Resulting problems include the spatter sticking to work pieces and/or tooling, injuries to workers, clean-up, porosity and loss of material.

Even when using spatter-preventative methods, it eventually builds up inside and on the weld nozzle and nozzle tip anyway, restricting the inert gas flow and causing porous, brittle weld joints. Fortunately, there are many options for reducing, or even eliminating, this dangerous and costly nuisance.

What causes spatter? Well, according to Matt Brooks of a manufacturer of welding equipment, cutting equipment, torches, robots, positioning equipment, and standard and custom arc welding cells, there could be several causes. According to Brooks, the main factor is a disturbance in the molten weld pool during the transfer of wire into the weld, typically caused by voltage being too low or amperage being too high, which in turn means the arc is too cold to keep the wire and pool molten and causes a stubbing effect of the wire. Spatter may also occur because of the gas selected for use ? for example, CO2 creates more spatter than MAG welding.

Additionally, coatings are one way to go when looking to reduce weld spatter. For instance, developer of fastening and assembly technologies, came up with a creative solution to help reduce their weld spatter problems. Their need for a spatter solution arose because they felt that cleaning spatter off a welding nozzle took too much time, and that most anti-spatter sprays or dips do not prevent spatter adhesion, must be frequently reapplied in order to be effective, and can be messy and even dangerous. In addition, the company wished to provide an alternative to procedures such as reaming, which they viewed as costly and inefficient, so they came up with Spatter-Nix, which is a new coating application. According to the company, this coating process helps prevent weld spatter accumulation, improves MIG gas flow and weld quality, reduces the frequency of nozzle cleaning, makes nozzle cleaning faster and easier, increases the lifespan of MIG weld nozzles and reduces the need for anti-spatter dips and sprays.

Ideal for thin metal automotive applications (0.7−1.0 mm) that employ a longer electrode, Spatter-Nix is a slick coating process that allows the spatter to be vibrated out. It coats the weld nozzle inside and out, providing maximum protection against spatter. (Internal coating length is dependent on the presence or absence of an insulator.) Even if the coating chips or flakes off outside of nozzle, the coating performance inside the nozzle and on the weld tip remains unaffected.

According to ND, the process has been garnering great response from welding companies. FIC America Corporation, a manufacturer of “stitched” welded muffler parts for Toyota, experienced improved productivity. Weld nozzle cleaning was reduced from every 15 minutes to every six hours, and weld nozzle cleaning was reduced from once every five cycles to once every 500 cycles. At one major automotive plant, Spatter-Nix was applied to two weld nozzles of robotic welders. Each robot performed six welds on each piece welded, averaging of 25 to 35 pieces welded per hour. The robots were employed continuously for two eight-to nine-hour shifts per day. Normally, operators found it necessary to clean the weld nozzles an average of three times during every eight– to nine-hour shift, but with this coating application, the robotic welders ran for six consecutive shifts without the need for cleaning.

In addition, a Tier 1 automotive supplier used Spatter-Nix on a robotic welder that performed seven-inch welds. The weld nozzle typically required reaming every four weld cycles. With the use of Spatter-Nix the robotic welder was able to complete 184 welding cycles without the need to ream the weld nozzle. What little spatter that did build up inside the nozzle was able to be removed with a gentle tap to the nozzle. Weld nozzle cleaning reduced from every six minutes to once every 100 hours. Also, a tool and die welding company implemented Spatter-Nix coated nozzles used in a heavy die repair application. In one application multiple welds were performed on steel pieces about five feet long and 3/4 in thick. The welding of one piece took, on average, 45 minutes to one hour. The hand welder found it necessary to clean his weld nozzle at least 10 times during the welding of one piece. Using a coated nozzle, the welder was able to weld 10 pieces without cleaning the nozzle.

As stated earlier, the type of gas used in welding may also contribute to spatter. According to (Cleveland, OH), Argon can be very useful in this area. According to the company, for most mild steel applications, CO2 will provide adequate shielding, but when you must have a flatter bead profile, less spatter or better wetting action, you may want to consider adding 75– to 90-percent argon to your CO2 shielding gas mix. Argon is inert to the molten weld metal and therefore will not react with the molten weld metal. When CO2 is mixed with Argon, the reactivity of the gas is reduced and the arc becomes more stable. However, Argon is more expensive. In production welding, selecting the perfect shielding gas can be a science of its own. Attributes such as material thickness, welding position, electrode diameter, surface condition, welding procedures and others can affect results. But fortunately, whether you decide to use a coating, try different gases, adjust your voltage, or try another solution, combating weld spatter is getting easier.

FIVE WAYS TO PREVENT WELD SPATTER

1. Up the Voltage. Cut down on spatter by adjusting your voltage. Voltage is closely tied to the welding arc’s length and the heat input of the weld. Find the right balance, so the weld is being created with the right intensity.

2. Up the Voltage. Make Sure the Welding Surface is Clean. One simple way to avoid spatter is to keep your welding surface free from contamination. Substances like oil may trigger the welding power supply to alter parameter settings — creating spatter before and after the right adjustments are made. Anything that oxidizes the weld pool (such as rust) may cause bubbles — which burst, creating more spatter. It’s best to clean the surface and avoid the mess. Remove buildup with an abrasive tool or chemical.

3. Up the Voltage. Secure the Welding Environment. In the fight against spatter, wind is an enemy. Make sure your shielding gas isn’t being affected by air circulation. Another environmental problem that causes spatter, cable grounding, can be easily fixed. Make sure cabling is secure and on clean surfaces.

4. Up the Voltage. Find the Right Torch Angle. Angling your torch with the wire in front may make a nice, smooth weld, but it shoots spatter outward. A drag angle with the wire behind keeps spatter in the weld pool.

5. Up the Voltage. Pay Attention to the Shielding Gas and Wire. Make sure your shielding gas and wire are preventing spatter, not contributing to it. Argon gas can minimize spatter, but it can change other aspects of the weldment. Many wires have deoxidizing substances in them, which will decrease the amount of spatter. Flux cored wires are a good safeguard against spatter.

Welding Electrode

2014-08-09T05:50:00.003-07:00

For Low Carbon Steels:

Cellulose Coated Electrode (E 6010)

(i) Lightly coated

(ii) All Positional, thin brittle slag, highly ductile

Cellulose Coated Electrode (E 7010)

(i) It is a cellulose type, all position, friable slag and good penetration

(ii) Good ductility and creep resistance up to 550c

Rutile Coated Electrode: (E 6012)

(i) All positional including vertical down with good penetration

Rutile Coated Electrode: (E 6013) 7411

(i) All positional, medium penetration, low spatter, high deposition rates

Rutile Coated Electrode: (E 6013) 7412

(i) All positional included Vertical down, medium penetration

Rutile plus Iron powder coated: (E 7014)

(i) All positional, medium heavy coated

(ii) Iron powder that enables the use of heavy current

(iii) Deposition efficiency up to 110%

Rutile plus Iron powder coated: (E 7024) 7512K

(i) Heavy coated electrodes with high deposition rate

(ii) Down hand (Butt, Fillet and Horizontal Fillet welds)

(iii) Easy to manipulate, High welding current can be used

(iv) Deposition Efficiency is nearly 140%

(v) It can be used as a Touch electrode

Rutile plus Iron powder coated: (E 7024) 7512L

(i) Super heavy coated iron powder

(ii) Metal recovery of about 210%

(iii) Suitable for high speed welding of down hand, Butt, Fillet and Horizontal Fillet welds

Acid Coating: (E 6020)

(i) Medium heavy coated electrode producing a fluid slag for down hand, horizontal and vertical welding

(ii) Recommended for low carbon steel where high strength, high quality weld deposits

(iii) Use for high current and high welding speeds

Basic Coating: (E 7018)

(i) Low hydrogen plus iron powder type

(ii) For heavy joints under restraint and subject to dynamic loading

(iii) Deposition efficiency 115%

Basic Coating: (E 7018) 1514HJ

(i) A medium heavy coated , low hydrogen, iron powder type

(ii) All position electrode

(iii) Medium high tensile structural steels

(iv) 1.4% Manganese

(v) Deposition efficiency 112%

(vi) Suitable for sub zero ( 0 ~ -40c)

Basic Coating: (E 7018) 1515HJ

(i) Low temperature up to -60c

(ii) 112% metal recovery

Basic Coating: (E 7018-A1)

(i) A medium heavy coated all positional

(ii) Deposition efficiency is 106%

Welding Formulas

2014-08-09T05:44:00.001-07:00

Welding Formulas:

Q1: A pressure of 20 volts is applied across ends of a wire, and a current of 5 Amperes flow through it. Find the resistance of the wire in ohms:

Ans: R= V÷I = 20÷5= 4 ohms

Q2: A welding resistor has a resistance of 0.1 ohms. Find the voltage drop across it when a current of 150 Amperes is flowing through it.

Ans: V= I X R, i.e, V= 150 X 0.1= 15 volts drop

Q3: A welding generator has an output of 80 volts, 250 Amperes. Find output in Kilowatts and Joules per second:

Ans:

V= 80

A= 250

W= 80 X 250 = 20000

KW= 20000/1000= 20 KW

20000 J/s

Q4: How do you find Chromium equivalent if Si= 0.8% and Cr = 19.0%?

Ans: Formula:

% Cr + % Mo(1.5 X %Si) + (0.5 X % Nb)

% Cr + % Mo(1.5 X % Si) + ( 0.5 X %Nb)

% 19.0 + 1.2 + 0

% 20.2

Q5: How do you find Nickel equivalent if C = 0.03%, Mn = 0.7%, Ni = 10.0% ?

Ans= Formula=

% Ni + (30 X % C) + ( 0.5 X % Mn)

% 10.0 + 30 X 0.03 + 0.5 X 0.7

% 10.0 + 0.9 + 0.35

% 11.25

Q: What is definition of dilution?

Ans: When two metals are fusion welded together by metal arc, TIG, MIG or submerged Arc processes, the final composition consists of an admixture of parent plate and welding wire.

Formula:

% percentage dilution = weight of parent metal in weld X 100

Total weight of weld

If there are 15 parts by weight of parent plate in75 parts by weight of weld metal then the dilution is 15/75 X 100 = 20%

Average values of dilution for various processes are:

Metal Arc: 25-40%

SAW: 25-40%

MIG (S.T) 25-40%

MIG (D.T) 15-30%

TIG 25-50%

Q6: What will be the approximate composition of the final weld if there is 40% dilution? With 40% dilution the plate will contribute 40% and the welding wire 60%. If 9% Nickel plate, 80% composition welding wire Nickel, 20% chromium:

Nickel Plate = 40 / 100 X 9 = 3.6

80% Ni welding wire= 60/100 X 80 = 48

20% Cr welding wire = 60/100 X 20 = 12

Iron = 40/100 X 91 = 36.4

So, %

Nickel = 3.6 + 48 = 51.6 %

Chromium = 12 %

Iron = 36.4%

Q7: A plate of an alloy of composition 70% Ni, 30 % Cu is to be welded to a plate of alloy steel of composition Cr-18%, Ni-12%, Fe-70% using a wire of composition 75%, Ni-15%, Cr-8% Fe.

Assuming 30% dilution, what will be the approximate composition of the final weld?

With 30% dilution each plate will contribute 15% and the welding wire 70%.

Nickel: 15/100 X 70= 10.5

A plate of alloy steel: 15/100 X 12 = 1.8

Welding wire: 70/100 X 75 = 52.5

So, Nickel is: 10.5 + 1.8 + 52.5 = 64.8%

Chromium:

15/100 X 18 = 2.7

70/100 X 8 = 10.5

So, Chromium is = 2.7 + 10.5 = 13.2

Copper:

15/100 X 30 = 4.5

Iron:

15/100 X 70 = 10.5

70/100 X 8 = 5.6

10.5 + 5.6 = 16.1

Q8: How do you find Arc energy (KJ/mm)?

Ans: Arc energy (KJ/mm) = arc voltage X welding current

Welding speed (mm/s) X 1000

Q9: How do you find Heat Input by Japanese standard?

Ans: Heat = Ampere X Volts X 60

Travelling speed

Heat= 170 X 25 X 60 = 17000 Joules/cm

If you require in KJ then,

Heat = 170 X 25 X 0.06 = 17 KJ/cm

Q10: What is Arc Energy ?

Ans: ARC Energy = (KJ/mm) = Volts X Ampere

Travel speed (mm/sec) X 1000

MAG Process:

Volts = 24

Ampere = 240

Travel Speed = 300 mm/ per minute

Arc Energy (KJ/mm) = Volts X Amperes

Travel speed (mm/sec) X 1000

= 24 X 240 X 60

300 X 1000

= 345600

300000

Arc Energy = 1.152 or 1.2 KJ/mm

Important:

Thermal Efficiency factors:

SAW (Wire Electrode) : 1.0

MMA (Covered Electrode): 0.8

MIG /MAG: 0.8

FCAW (with or without gas shield): 0.8

Tungsten Inert Gas (TIG): 0.6

Plasma: 0.6

Heat Input (KJ/mm) = volts X Amperes X 60 X K

Travel speed (mm/sec) X 1000

Volts = 24

Amp= 240

v = 300 mm/per minute

Heat Input (KJ/mm) = Volts X Amperes X 60 X K

Travel speed (mm/sec) X 1000

Heat Input (KJ/mm) = 24 X 240 X 60 X 0.6

300 X 1000

Heat Input (KJ/mm) = 207360 / 300000 = 0.6912 KJ/mm

Q10: How do you find Heat Input by American Standard?

Ans: Root = 140 X 14.5 X 60 = 121800/ 2.300= 52.9 KJ/mm

1000 X 2.3

Filling = 160 X 16 X 60 = 153600/ 1500 = 102.4 KJ/ mm

1000 X 1.5

Capping = 150 X 15 X 60 = 135000 / 1500 = 90 KJ /mm

1000 x 1.5

Travelling Speed :

Root: 140 X 14.5 X 60 = 121800/ 52950 = 2.3 X 25.4 = 58.4mm/min

1000 X 52.95

Filling: 160 X 16 X 60 = 153600 / 102400 = 1.5 X 25.4 = 38.1mm/min

1000 X 102.4

Capping: 150 X 15 X 60 = 135000 / 90000 = 1.5 X 25.4 = 38.1 mm/min

1000 X 90

Q11: How do you calculate Welder Travel speed?

Ans:

Welder Travel= 4 inches

Time : 50 seconds

Formula: 4 / 50 = 0.08 inch per/sec

0.08 X 60 sec/per min= 4.8 inches /per min

Conversion formula:

4.8 inches X 2.54 = 12.1cm/min

12.1cm X 0.393 = 4.8 inches/min

Important:

Shield Metal Arc Welding:

Electrode Holder: Maximum Current Range Resistance: 150A – 500A Normal Range. If metal thickness less than 5mm then Gap will be between 1mm -2mm and if thickness is 5mm – 8mm and the gap will be between 2mm-4mm without any special preparation.

Lap weld:

(i) Parent metal should be proper cleaned

(ii) Pipes to have different diameters

(iii) Not recommended above 10mm thickness

(iv) Metal is wasted in providing a lap

Butt Weld:

(i) When the material thickness exceeds 8mm, it is often difficult to achieve full penetration with square edge preparation.

(ii) Then prepared by machining to V configuration.

(iii) When plate thickness above 20mm, it is better to have double V edge preparation. This helps in achieving good quality weld without distortion.

Current Adjustment:

If plate thickness is between 5mm-60mm, the electrode size is recommended between 3mm-6mm.

SMAW operation:

(i) In a welding transformer usually two settings for OCV are available say 80 V and 100V.

(ii) The OCV setting for a D.C. power source is usually 10-20% lower than in a welding transformer of the same current ratings.

(iii) It is often observed that the weld bead becomes wide and peaky at the point of restarting; this is usually due to over welding of the crater. This should be avoided , as far as possible, because it is not only un-slightly but also can be the source of weld defects like slag entrapment, porosity and cracks.

Electrode Motions:

The width of the weld bead formed under normal welding conditions in SMAW is between 1.5-2.5 times the diameter of the electrode; with well penetrated and smooth passage of the deposited metal to the work piece surface.

Cellulose coated electrodes: E6010

These are usually light coated, all position electrodes with a forceful penetrating arc. The weld metal is highly ductile.

Rutile coated Electrodes: E6012

It is an all position electrode with good penetration and quick freezing slag. Easy to operate.

Rutile coated Electrodes: E6013

All positional electrode, gives low spatter and easy to remove slag.

Rutile plus Iron Powder: E7014

A medium heavy coated all position electrode containing iron powder that enables the use of heavy current which consequently leads to higher welding output with a deposition efficiency of up to 110%.

Rutile plus Iron Powder: E7024

It is a heavy coated electrode with high deposition rate for down hand butt and fillet welds as well as horizontal fillet welds. Very easy to manipulate, low spatter rate, high welding current and deposition efficiency is nearly 140%. It can be used as a touch electrode.

Rutile plus Iron Powder: E7024

A super heavy coated iron powder electrode with a metal recovery rate of about 210%, suitable for high speed welding of down hand butt, fillet and horizontal fillet weld.

Acid Coating: E 6020

A medium heavy coated electrode producing a fluid slag for down hand horizontal, and vertical welding. For low carbon steel where high strength and high quality weld.

FIRE FIGHTING & FIRE PREVENTION MANAGEMENT

2011-07-11T03:46:00.000-07:00

Triangle of Fire:-
Heat
Fuel
Oxygen: 21% in Air

Spread of Fire:
Three modes:
1) Conduction: Travel from one side to another side
2) Convection: It is applicable in Chemical and Gases. One thing collapse another
3) Radiation: Laser is the form of Radiation

Principles of Extinguishing:-
1) Heat ------- Oxygen
2) Smothering: mean to cover with anything.
3) Cooling: Water etc.

Classification of Fire:
A) Class fire: wood , paper, cloth,rubber, etc. ( Extinguisher Type: Water)
B) Liquids: ( Oils, Paints, etc) (Foam: AFFF (Aqus film forming foam protiene)
C) Gases: ( Sui gas, LPG, CNG, Hydrogen) ( DCP: Dry Chemical Powder( Ammonium Phosphate +Silicon)
D) Light metals: Like magnesium use in color form ( Dry Chemical Powder)
E) Electric, Electrical equipment ( Co2, Halotron) Halotron has more density than air.

Remember: Smoke will increase less of oxygen.
Carbon will be increase.
Back Draft:

A fire that has burned out all the oxygen in a room leaving only superheated gases.

Indications:
1) Yellow or brown smoke exits in puff form.
2) Incomplete Combustion caused dark colours.
3) Un burned carbon
Signs & Symptoms:
Yellow or brown smoke, Smoke which exits small holes in Puff
2) Extremely hot surrounding environment
Always occurred in Basement

Suit: Black Smoke
Cracked Windows
Slight Vibration of glass pan
Air Suction
Preventive Measures:
Immediate Evacution
Ventilation
Careful Entry
Boundry cooling
Fire Suit
Flash Over:-
Temperature: 500c (930 F)

Stages of Flashover:-
1) Initial Fire procedure layer of Hot Smoke
2) Hot Smoke spreads across the ceiling
3) Hot smoke bounded by the walls
4) Depth of Buoyant smoke layers grows
Fires always travel from ceiling to Wall.
Radiated heat, Heat the combustible materials
Flammable gases are given off
Surface Temperature attained from.
Brick : 250c
Concrete: 800c – 900c
Preventive Measures:-
1) Careful entry ( Sitting beside the door) Always use Nomex Material Turn Out gear
2) Use of Appropriate PPE ( Personal Protective Equipment)
Fire Prevention System:-
1) Hydrant system
2) Wet Hydrant system anytime available
3) Dry: No water in lines, Stored in Tank Fixed Installation
4) Sprinkler System: Installed in Walls inside
5) Operate Automatically.
6) Heat & Smoke Detectors: Is a fixed fired detection system.
7) To detect heat
8) Smoke Detector: To detect smoke
9) Fire Alarm system: Fixed fire appliances:-
10) Nozzels, Hose, Hose reels, (Nozel: 2.50 inches) ( Reels: 75 Inches)

Emergency Exits:-
1) Fire stairs
2) Fire doors
3) First Aid Fire Appliances
4) Fire Extinguisher
5) SCBA: Self contained breathing apparatus

Gas / Smoke Masks
Respirators: Effective
EEBD: Emergency Escape Breathing Devices: ( 5-10 minutes)
EMBOW Bags:
Fire plans:-
1) Sketch of a building
2) Fire Fighting Appliances
3) Installations
4) Emergency evacuation plan

Classification of Fire Volume:
Small Fire: 1-2 Jets
Medium Fire: 3-8 Jets
Large Fire: 9-18
Major Fire: 18 + plus
Extinguisher Parts:
1) Neck Ring
2) N2 20%
3) Water (80%)
4) Plastic Belt
5) Syphone Tube
6) Barrel
7) Bottom Ring

What is P A S S?
P: Pull the Pin
A: Aim the nozzle at fire
S: Squeeze the lever
S: Sweep

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