Changed my mind on pre-heating thick plate with a rosebud

Last week we were fitting a 2-inch thick pressure vessel head in Baton Rouge, and the foreman insisted we skip the rosebud and just run the beads hot. I thought he was crazy, given the thickness. But we ran the root at 300 amps with a 1/8 rod and it fused perfectly, no cold lap. It saved us nearly three hours of setup and gas time on that joint alone. I've always been taught to pre-heat everything over an inch and a half. Has anyone else found certain procedures are more about habit than need?

4 comments

4 Comments

wade_anderson2mo ago

Yeah but that's a huge gamble on fit-up and the welder's skill. One bad day and you're looking at a crack in a critical joint, not worth the saved time to me.

morganl712mo ago

Remember that story about the guy who tried to weld his own trailer hitch? He was so sure he could match the factory specs, saved a ton of time skipping the proper jig. Thing held for about a month, then just snapped clean off on the highway with his boat attached. Totaled the boat and nearly caused a huge wreck. The shop that fixed it said the weld looked okay on the surface but had zero penetration because the fit was off by a few degrees. That's the gamble, right there.

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hunt.jennifer2mo ago

Exactly. That's the scary part, it looked fine. No cracks, nice bead. But the metal underneath never fused. All that stress went right to a tiny line. Like a perforated tear.

knight.uma7d ago

Oh come on. That trailer hitch story gets brought up every time someone wants to scare people into following every rule to the letter. Guy probably had way more problems than just skipping a jig. Bad fit-up, wrong rod, who knows. I've seen plenty of backyard welds hold up just fine for years. The horror stories always get told way more than the boring ones where everything worked out.