Running the Weld Test Centre here for the past 6 years, we have heard every excuse in the book for why a weld fails and I am considering a blog post listing the most interesting reasons we get. Many welders want to see their weld and understand why it has failed. Respecting that this is their livelihood we want to help them understand the failures that occur after many of the same questions, one of the women in the office set out to do some research. She has found some great information on some of the most common weld defects. So here we are, a series of three blogs on the top three weld defects that we see, here at our weld test centre.
Weld Defects – Week 2 – Incomplete Penetration
The second most common reason for failure that we have here is incomplete penetration.
Definition of Penetration : Depth of fusion with the base metal. Thank you to “Welding skills by R.T. Miller, 2nd edition, published 1997.
Lack of Penetration therefore indicates that the weld metal is not making its way through the gap and into the backing bar.
Just as with Lack of Fusion, it is important to ensure that the new piece is as strong as a single piece of material, the weld metal must adequately penetrate into the backing bar and parent metal.
When welding from both sides of material, partial penetration may occur. Depending on the requirements of the weld, partial penetration, may be acceptable. Unless a complete penetration weld is required, then this is incomplete penetration and is considered a weld defect.
There is lots of really technical writing out there about incomplete penetration, its causes, and ways to prevent this defect. The best article we have found is by ESAB http://www.esabna.com/euweb/mig_handbook/592mig10_2.htm
The information presented references specifically the GMAW welding process, which in structural welding, has the highest failure rate.
Check out next weeks blog on Slag inclusion!
Until next week,