MIG welding & lack of fusion

by Jim Fisher
(Ashland, OH)

I am a welding instructor @ local JVS, all of the welding machines in the shop are having the same problem --lack of fusion. We are doing a 1G weld on 3/8" plate. The dimensions are: 3/8" x 3" x 7" with a 3/8" x 1" x 8" backing plate. The AWS D1.1/D1.1M:2002 says that we must use a .250" gap between the plates.
Everything sounds great, looks great, & seems to weld great, however, on the bend test-every one of our samples have cracked or broken on the root side (including my own welds!)
I am at a loss. I have taken & passed several weld tests, both x-ray and destructive testing as well.
Any insight into this matter would be greatly appreciated.

Jim Fisher


can you use 1/4" backing? I think that is called for for 3/8" plate in the D1.1.

also, what process? if it is fcaw, I have found problems with .035 wire " but .045" worked much better.

thanks for posting,


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Aug 01, 2013
Mig welding and lack of fusion NEW
by: Anonymous


are you running your machines at a transfer mode of short circuit or spray transfer?

If in short circuit are you weaving the root or are you running stringers?

Try gapping the plates a little wider and running two stringers for the root pass.

In spray transfer mode in the flat position there should be no problem getting the root to tie in.

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