Weld defects are often caused by improper technique (like poor shielding gas coverage or incorrect travel speeds), parameters or equipment settings. It’s important to teach students how to fix the situation as quickly as possible when a weld defect appears.
These are a few troubleshooting and remedy solutions to cover in your CTE welding classes.
Porosity
One of the most common MIG welding defects is porosity — the result of gas becoming trapped in the weld metal. These are a few common causes and solutions.
Cause: Inadequate shielding gas coverage
Solution:
- Check the regulator or flow meter for adequate gas flow, increasing it as necessary.
- Check the gas hoses and welding gun for possible leaks, and block off the welding area if drafts are present.
- Be sure to use a large enough nozzle to shield the weld pool fully with gas, keep the nozzle clean and free of spatter, and follow the manufacturer’s recommendation for proper contact tip recess.
Cause: Dirty base material
Solution: Use clean base material
Cause: Excessive gun angle
Solution: Correct your technique and practice often, especially with cost-effective virtual reality welding solutions
Cause: Extending the wire too far from the nozzle
Solution: A good rule of thumb is to extend the wire no more than 1/2 inch past the nozzle
Cause: Wet or contaminated shielding gas cylinders
Solution: Replace damaged cylinders immediately
Lack of fusion and cold lap
You may have heard the terms cold lap and lack of fusion used interchangeably. However, these are slightly different concepts and can happen independently or in conjunction with one another in MIG welding.
Lack of fusion is the result of the weld metal failing to fuse completely to the base metal or to the preceding weld bead.
Cause: Usually by improper welding gun angle or incorrect travel speed
Solution: Maintain a 0- to 15-degree gun angle during welding and keeping the arc on the leading edge of the weld pool. It’s sometimes necessary to increase travel speed to maintain correct arc position.
Cause: Insufficient heat in the weld
Solution: Increase voltage settings or wire feed speeds
A cold lap, on the other hand, causes the weld to overfill and essentially overlap on the toes of the weld.
Cause: Using incorrect travel speeds
Solution: Increase travel speed
Burn-through
Cause: When the weld metal penetrates completely through the base material (especially common when welding thin materials less than 1/8 inch or about 12 gauge)
Solution: Reduce your voltage or wire feed speed to reduce heat. You can also try increasing ravel speed, particularly when MIG welding on materials especially prone to heat buildup like thin aluminum.
Two other common MIG weld defects are Excessive Splatter and Concave and Convex Weld Beads. To learn more about the causes and solutions for these, head over to the Miller Welding blog.
Interested in welding training and certification? We’re hosting — alongside the experts from Miller — an American Welding Association (AWS) Certification professional development workshop Wednesday, October 16, 2019 at 1pm at New River Community College (Dublin campus). Get all the details and register here.
