TIL my old foreman was right about preheating plate edges before welding

Burned through about 3 hours of labor last Tuesday redoing a seam on a 1 inch thick tank wall down at the Port of Houston. Old timer Tim came by and said I needed to get the edges up around 250 degrees before striking the arc. I always figured it was just old school nonsense. After I cleaned up my mess and tried his way, the weld flowed way smoother and I didnt have to chase any cracks. Has anyone else had a job get saved just by listening to a veteran's pipe trick?

2 comments

2 Comments

claire_hart531mo ago

My brother in law is a pipefitter over in Beaumont and he told me the same thing about preheating. He said it was something about keeping the hydrogen out of the weld so it doesn't get brittle. I always thought he was just repeating what some old guy told him, but after watching him work on a pressure vessel last summer I changed my mind. He used a temp stick to check the edge and it really did make the puddle act different. I mean, I guess there's a reason they've been doing it for decades.

lily701mo ago

Oh yeah, @claire_hart53 your brother in law nailed it. Preheating slows the cooling rate just enough to let that hydrogen diffuse out before it wrecks the weld.