Tack welds - compliance with AS1554

[frans]

We have been analyzing welding time on a job and found some of our welders were grinding out tacks and others welding over them. Obviously it takes a lot more time grinding them out. My question is, what is common and accepted practice?

I may mention this is 1554.1 GP work on pipe bridges. The welders are all qualified to our workshop procedure.

 

[dhengr]

Frans:
Generally, if you are careful about where you make tack welds, you just weld over them and remelt the entire area in the process. There is no need to grind them out in this case. I think most welding textbooks talk about this someplace. The problem is that most tack welds are quick and short of length so they don’t allow the normal metallurgical changes to happen in the area of the weld. They cool too quickly, not enough heat input, and they tend to cause hard spots in the steel and stress raisers at the starts and stops. Arc strikes and tack welds should be ground out and cleaned up where they are not welded over becuase they are potential stress raisers and embrittle the base metal.