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

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. UVU CRT 2009

Mig Welding  Uses a constant voltage source.  Wire feed rate sets the current.  Continuous flow of shielding gas.  Continuous supply of wire. UVU CRT 2009

Mig Internals  Straight or Reverse Polarity.  Wire Tension Adjustment.  Continuous Wire. UVU CRT 2009

Electrode Wire Sizes  There are three common sizes of MIG wire is recommended for collision repair work. UVU CRT 2009

Mig Welding Adjustments  Wire Feed Speed  Voltage  Continuous/Spot  Distance from coupon  Push/Pull UVU CRT 2009

Mig Welder Settings  Voltage Adjustment  Wire Feed Adjustment UVU CRT 2009

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. UVU CRT 2009

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 UVU CRT 2009

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 UVU CRT 2009

Weld Positions  Standard Flat Position.  Vertical – Start at the top and move down. UVU CRT 2009

Weld Positions  Horizontal – Used on vertical panels.  Overhead – Can be a difficult weld to master. UVU CRT 2009

Defects – High Heat  A voltage setting that is too high will result in holes melted through the panel. UVU CRT 2009

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 UVU CRT 2009

Defects – High Wire Speed  High wire speed will create a cooler weld with very little penetration and excessive surface bead buildup. UVU CRT 2009

Defects – No Gas  A weld without shielding gas will be porous and very uneven. UVU CRT 2009

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. UVU CRT 2009

Defects – Speed too Fast  If the travel speed is too fast inadequate heat will create a tall bead with no penetration. UVU CRT 2009

Defects – Speed too Slow  Travel speed that is too slow will result in a wide bead with a large heat affect zone. UVU CRT 2009

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. UVU CRT 2009

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. UVU CRT 2009

Problem Solving  Clean The Metal Coatings Rust-proofing Grime Rust Don’t Grind off Galvanizing UVU CRT 2009

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. UVU CRT 2009

Weld Fit Up  Assure Good Fit Up Tightly Clamp the Metal Using Locking Pliers Grind Off Burrs Use Metal Screws Use Clecos UVU CRT 2009

References  Miller Electric Mfg. Co. Education  Lincoln Electric Co. Lincoln Welders  Inter Industry Conference on Automotive Collision Repair. I-CAR Online Training UVU CRT 2009