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PSA: Don't skip the pre-heat on a cold morning weld
I was rushing to patch a small leak on a feedwater heater at a plant in Erie last Tuesday, and it was maybe 35 degrees in the bay. I tacked the patch plate on, but didn't let the base metal warm up enough with the torch first. The weld looked fine, but when I did the hydro test at 150 psi, it cracked right along the edge of the heat affected zone. My foreman, Jim, just shook his head and said, 'Metal's gotta breathe, kid.' Had to grind it all out and start over, which cost us half a day. Has anyone else had a weld fail just from the cold? What's your rule of thumb for pre-heat temps?
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