A welder in Lafayette told me to skip the preheat on 2-inch plate, bad idea

I was working a job outside Lafayette last month on a 2-inch carbon steel plate for a hopper base. This old welder, guy had 30 years in, said the preheat was just a waste of time on mild steel, that it was only for fancy alloys. I listened because he seemed like he knew his stuff, figured he had seen it all. We ran a bead and within ten minutes I noticed a hairline crack forming right along the weld toe. Took me three hours to grind it out and redo the joint with proper preheat at 250 degrees. Cost me the whole afternoon and a chunk of my profit on that repair. Has anyone else gotten bad advice from a senior hand that ended up costing more than just time? What do you do when a veteran pushes back on basic procedure like that?

2 comments

2 Comments

the_vera1mo ago

250 degrees on 2-inch plate sounds about right, but I gotta ask, did you actually verify the crack was from skipping preheat or could it have been something else? Cold weather, damp rod, or even a tight fit-up can mess with you too. I've seen guys skip preheat on way thicker stuff and get away with it for years, so sometimes it's luck of the draw. That old timer might have had a point for his setup, but every joint is different. Still, you got the job done in a day, so maybe it was just a bad bead and not a procedure issue. Either way, extra heat never hurt anyone, so I'd say you're both kinda right.

jake_bell991mo ago

Was the bead actually cold, though, because I've seen plenty of cracks that looked like preheat issues but were really just a damp rod or a dirty joint? That's the thing about @the_vera's point about luck of the draw, some guys run hot rod all day and never see a crack, then one cold morning everything changes. I remember a job where we had a 3-inch plate, no preheat, and it held fine for a decade, but the next year the same setup cracked within a week because the shop got drafty. So yeah, the old timer's advice might sound rigid, but he's banking on consistency over being right every single time. You got it done in a day, so the fix worked, but I'd still mark that as a warning for the next joint. Extra heat costs you a little time, but a redo costs you the whole day.