Welding Tips and Tricks

I was practicing tig welding on 1/8" steel flat stock, had argon, cleaned metal, etc. I had welded two different lap joints without a problem. Then I cleaned the edge and surface of the two raised pieces of the lap joint (the higher ones if set down on the table) and tried a butt weld. I got horrible contamination. The metal was cleaned as before when all went well. I did another but weld with two pieces laying flat on the table and that worked ok. I saw a video that put argon on the underside of what was being welded, was this my problem?

Okay, Tom, this may be a stretch in your case, but...

In a lap joint, as you close the sides and there is less room for anything trapped to escape (Moisture, oils. oxides, etc) it will tend to boil out at the point of the weld, the hottest point.

I deal with this all the time with "working doublers" that must have a "weep-hole" to allow trapped gasses to escape while closing the weld.

Steve S