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An old welder in St. Louis told me to always preheat 4130 chromoly to 400 degrees
I was working on a custom header and thought I could skip it to save time. The weld cracked right along the heat line after the first thermal cycle. Now I never skip that step, no matter how thin the material looks. What's one piece of shop advice you got that you learned the hard way to follow?
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stellag216mo ago
Feel that pain. I had a similar thing happen with some 1/8 inch wall tubing on a roll cage brace. Looked solid coming off the table, passed the initial checks. First real bump in the dirt and a hairline crack showed up right at the toe of the weld. Cost me a whole weekend to cut it out and redo it right, with the preheat this time. Never makes sense to skip it once you've paid that time tax.
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max3885mo ago
Learned that lesson the hard way myself, cracked a bead so bad it looked like a spiderweb.
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lucas1596mo ago
That preheat rule is no joke, especially with chromoly. It's not just about the weld holding, it's about letting the whole piece cool down slow and even. You can get away with skipping it sometimes, but then it's just a time bomb waiting for that first real heat cycle to crack. Makes you wonder how many shortcuts are actually costing more time in the long run.
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