slag inclusion

Weld Defect #3 – Slag inclusion

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 3 – Slag inclusion

Slag inclusion is a common issue in FCAW welding.

Definition of Slag: small particles of cooled flux trapped in the weld metal. Thank you to “Welding skills by R.T. Miller, 2nd edition, published 1997.

Slag inclusion is the small particles of flux that become trapped in the weld metal which prevent complete penetration of the weld.

slag inclusion Slag inclusion in a CWB Weld Test Plate

There is lots of really technical writing out there about Slag inclusion.   The best article we have found is
“The Fabricator”

The information presented references specifically the FCAW welding process.

Check out previous week’s blogs on

  • Lack of Fusion
  • Incomplete Penetration

Until next week