Quote:
Originally Posted by CWPASADENA
I think you may have it backwards.
Cold rolled has a lot of internal stress due to the rolling process and is hard. If cold rolled steel is annealed, it will be soft but then it is no longer cold rolled.
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Cold Rolled is kind of a misnomer since it is hot formed before it's cold formed. We are also referring to sheet metal and not formed structural components. Draw quality steel is what is used for forming stuff like a cross member or a frame rail. The carbon content is not all that high in sheet metal.
The major difference is the size and finish. Hot rolled has a rough finish and tends to shrink when you heat it for forming. Either one can be hot worked if forming to fit as a patch. Both would be welded and then stress relieved. The cold rolled will keep its size and finish better plus be a bit more ductile after the stress relief. It would be the closest thing to what piece broke out of there on the original part.
My guess is that the member cracked in service so it was welded. It likely wasn't stress relieved so it failed again at the welds. They likely reinforced it with some flat stock welded on the next time and finally the whole patch and part of the member all broke out. I've seen a lot of stuff like this on old farm vehicles that were overloaded and road hard.