concave weld bead

[axehind]

I recently got a harris O/A set and leased the tanks. I've been praticing welding on 3/16 inch steel. How I do it is I take the steel, clean it, and then cut 6 inch long cuts into a 8 inch piece with my chop saw. Then I weld the cuts using 3/32 welding rod and a #6 tip. The problem is that the bead ends up having a slight concave to it after I'm done. Is this from not dipping the welding rod enough? Is the gap too big from the cuts? The blade is 5/32 abrasive on the saw. Whats usually the cause of the concave weld bead?

Thanks,
axehind

[chip hayden]

assuming you are doing a butt and not a lap joint, yes, you probably need to add more filler. possibly, a little too hot also.
weld the very start and the end of the butt joint by aiming the inner cone of the flame directly at each extreme end of the joint. once thats joined, pivot the torch to the upright, forehand[push] angle and proceed.
as you go forward, add filler to the leading edge of the molten pool. allow the pool to momentarily freeze by pulling your wrist back [the one with the torch handle]. then go back down with the torch to melt the edge of the weld again, add filler as before, and move forward. this might help prevent a concave weld.

[Roger]

Use 1/8" welding rod when welding 3/16" plate should solve your problem. Filler rod should be close to metal thickness. I never had to raise torch each time after adding filler metal with right size flame. That could give stack of dimes pulsed tig bead look. I never considered that a good gas weld bead.

[axehind]

Do you think the gap is too big? It's got to be at a min 5/32" since the abrasive blade it that thick. I'm guessing it's probably wider than that. Thats almost twice as thick as the rod I'm currently using. I'll try the 1/8" rod.

axehind

[chip hayden]

Roger. I'm not a fan of "stacking" in any process. trust me. by moving ONLY the wrist upward at the end of the half-moon motion cools the pool enough so it won't sink as it shrinks.