Cooling Off period

Let's hope it holds together. I'll bet it will be perfectly fine.

Although there is an entire mythology about welding 4130, it's really relatively ductile, which makes it more forgiving that many people think.

As I said in that article, the reason 4130 leads to so much head-scratching is that it's *very* slow-quenching. In thin tubes, which are almost always welded in the normalized condition, it can wind up quench-hardened from welding. It actually will air-harden. That's why it was two decades before TIG welding it was accepted. It's only recently (the last couple of decades) that MIG welding has met the approval of the "experts." Stick is similar.

Sections as thick as you're welding generally don't experience that quench-hardening problem, but the quench characteristics can produce a very confused HAZ. That's why the pre-heating and the slow cooling. Every authority I've talked to over the last decade or so says that's all it takes.

When welding thin normalized or annealed 4130 that will not be heat treated, using a mild steel filler "draws" some of the carbon and alloy from the base into the weldment, making the air hardening/quench hardening less of a problem, and as the weld is generally thicker than the tubing being welded, the lesser tensile strength of the weldment is not an issue, as there is more metal, of lower strength, producing virtually the same(or better) strength overall, and the joint/HAZ is slightly softer, more ductile, or less brittle.