Tube vs. Pipe

thurgood said:
"Right up front, I will tell you that it is not possible to accurately stress relieve a welded 4130 steel assembly by heating it red-hot with an oxy-acetlyene torch in an open air workshop. Stress relieving a welded 4130 assembly such as an aircraft engine mount or a race car rear suspension member is a metallurgical process that requires at least six hours to do correctly. The steel grain structure must be brought up to about 1150 degrees F, held at that temperature for several minutes to a couple of hours, then slowly cooled back down to room temperature. This very specific process absolutely cannot be accomplished by a hand-held torch in a welding shop."

From Performance Welding by Richard Finch
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Beat me to it!
 
thurgood said:
Typically failures occur beyond the weld at the edge of the heat affected zone from what the books say.
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we know, I already said that...
:flipoff2: :D
rockcity said:
The weld will not fail, its that small part just past the weld where it fails...Rob
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but good info/quotes otherwise...
 
It seems books have conflicting information about welding 4130 and whether or not heat-treatment is necessary. I have TIG welded a bunch of thin-wall 4130 without heat-treatment and without failure problems. Is it better to (properly) anneal 4130? Yes. Is it always necessary? No.

I don't have anything to add on the actual topic of the thread, but I prefer tube for structural members (i.e anything your life might depend on).
 
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