Post By kustomizingkid
Welding 4130 prehard to soft steel.
Have to weld 1,5" dia solid 4130 in a pipe, protruding halfway out of the tube.
Pipe is just standard non-hardenable steel.
Wonder if the area around the weld will be brittle?
There will be strain on that thing.
Plenty of preheat and you will be fine.
with 4140 I like to see 600F preheat
A post weld draw down probably wouldn't be a bad idea either...
"post weld draw down" ?
What is that?
stressrelieve nd a slow cool.
The mild steel pipe shouldn't get brittle, but the 4140 will. Since it's solid, brittle won't matter unless there's impact, I'd expect the pipe wall to fail first unless it's very thick. Preheating is good, at least 200°F on the 4140 will reduce embrittlement. Use mild steel rod or 308 stainless rod for maximum ductility.
We weld 4140 in production, pre heat to 400 and take the temp to 600 with the weld, cool slowly. If you want the hardness of the pre hard you will have to heat treat after it cools.
I wouldn't weld that with mild steel stick rod. Mild steel mig wire is fine. 4140 needs a low hydrogen process, mig qualifys, so does a low hydrogen stick filler.
Thank you all.
IŽll mig weld it and preheat to 400 to 600.