Mig Welding

1
Mig Welding
Presentation, Pictures, Graphics and Content
Produced by Terrance K. Orr M.Ed. Assistant
Professor Collision Repair Technology Utah
Valley University 2007-2008
2
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.

3
Mig Welding

• Uses a constant voltage source.
• Wire feed rate sets the current.
• Continuous flow of shielding gas.
• Continuous supply of wire.

4
Mig Internals

• Straight or Reverse Polarity.
• Wire Tension Adjustment.
• Continuous Wire.

5
Electrode Wire Sizes

• There are three common sizes of MIG wire.
• .035
• .030
• .023
• .023 is recommended for collision repair work.

6
Mig Welding Adjustments

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

7
Mig Welder Settings

• Voltage Adjustment
• Wire Feed Adjustment

8
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.

9
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

10
Gun Technique
Pushing the Weld
Pulling the Weld

• Heat into Work
• Easier Burn Through
• Faster Rate of Travel

• Heat into Puddle
• Slower Rate of Travel

11
Weld Positions

• Standard Flat Position.
• Vertical Start at the top and move down.

12
Weld Positions

• Horizontal Used on vertical panels.
• Overhead Can be a difficult weld to master.

13
Defects High Heat

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

14
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
15
Defects High Wire Speed

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

16
Defects No Gas

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

17
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.

18
Defects Speed too Fast

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

19
Defects Speed too Slow

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

20
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.

21
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.

22
Problem Solving

• Clean The Metal
• Coatings
• Rust-proofing
• Grime
• Rust
• Dont Grind off Galvanizing

23
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.

24
Weld Fit Up

• Assure Good Fit Up
• Tightly Clamp the Metal Using Locking Pliers
• Grind Off Burrs
• Use Metal Screws
• Use Clecos

25
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.co
  m/, 2006.