Mig Welding

Presentation, Pictures, Graphics and Content

Produced by:

Terrance K. Orr M.Ed.Assistant Professor

Collision Repair Technology

Utah Valley University

2007-2008

Why Mig Weld?

Wire-feed Fusion Welding Process. Minimizes the loss of strength in High

Strength Steel. Minimized Metal Distortion. Vehicle Manufacturers demand its

use. Faster Procedure.

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Mig Welding

Uses a constant voltage source.

Wire feed rate sets the current.

Continuous flow of shielding gas.

Continuous supply of wire.

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Mig Internals

Straight or Reverse Polarity.

Wire Tension Adjustment.

Continuous Wire.

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Electrode Wire Sizes

There are three common sizes of MIG wire. .035 .030 .023

.023 is recommended for collision repair work.

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Mig Welding Adjustments

Wire Feed Speed Voltage Continuous/Spot Distance from coupon Push/Pull

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Mig Welder Settings

Voltage Adjustment

Wire Feed Adjustment

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Welder Suggested Settings Each welder has

suggested wire feed and voltage settings dependant on the thickness of the material, the shielding gas, and type of wire used.

This is found on the lid of the welder.

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Tuning the Welder

Tune For Specific Metal To Be Joined Set Voltage and Wire Speed Make Sample Weld Readjust Settings as Necessary Practice the Push and Pull Technique

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Gun Technique

•Heat into Puddle

•Slower Rate of Travel

•Heat into Work

•Easier Burn Through

•Faster Rate of Travel

Pulling the Weld Pushing the Weld

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Weld Positions

Standard Flat Position.

Vertical – Start at the top and move down.

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Weld Positions

Horizontal – Used on vertical panels.

Overhead – Can be a difficult weld to master.

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Defects – High Heat

A voltage setting that is too high will result in holes melted through the panel.

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Defects – Good Weld

This is an example of a good weld. Look for an even bead without spatter, and an even heat affect zone.

Heat Effect Zone

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Defects – High Wire Speed

High wire speed will create a cooler weld with very little penetration and excessive surface bead buildup.

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Defects – No Gas

A weld without shielding gas will be porous and very uneven.

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Travel Speed

Travel Speed is another variable that can affect your weld quality. Too slow can cause excessive

penetration and burn-through. Too fast can cause excessive bead

buildup without adequate penetration. It is a combination of Travel Speed,

Voltage, and Wire Speed that creates a good weld.

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Defects – Speed too Fast

If the travel speed is too fast inadequate heat will create a tall bead with no penetration.

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Defects – Speed too Slow

Travel speed that is too slow will result in a wide bead with a large heat affect zone.

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Weld Penetration

Weld penetration should also be checked to ensure complete metal fusion without excessive heat.

This picture shows a good even ribbon of penetration.

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Weld Penetration

This picture is showing excessive penetration.

The weld puddle is literally falling through the metal and if left unchecked will result in a hole.

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Problem Solving

Clean The Metal Coatings Rust-proofing Grime Rust Don’t Grind off Galvanizing

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Problem Solving - Weld Fit Up The term Fit Up

refers to the preliminary alignment and securing of the panels to be welded.

Proper fit up can greatly enhance the weld quality.

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Weld Fit Up

Assure Good Fit Up Tightly Clamp the

Metal Using Locking Pliers

Grind Off Burrs Use Metal Screws Use Clecos

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References Miller Electric Mfg. Co. Education.

http://www.millerwelds.com/education/library.html, 2006.

Lincoln Electric Co. Lincoln Welders. http://www.lincolnelectric.com/, 2006.

Inter Industry Conference on Automotive Collision Repair. I-CAR Online Training. http://www.i-car.com/, 2006.

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