Hardening steel after welding

[joedhiggins]

So I am in the process of making some tool rests for the lathe. I am using spare 4140 and 1045 rods for the face of the tool rest, and mild (1018 and A36) steel for the remainder. I would like to harden these rods. I for the weld, I preheat beforehand, welded, peened, normalized.

My plan is to clean the pieces up, harden and temper them, then weld the posts on (that weld will be mild to mild, so I am not as concerned about it).

I am planning on an oil quench for the smaller (5/8" diameter 4140) and thinking the 7/8 1045 might also harden deeply enough in oil that I don't need to do a brine quench.

My questions are: oil or brine for the 7/8" 1045 rod, and are there any other things I ought to do to minimize the chance of weld cracking on quench?

 

[kuraki]

If you preheated and cooled slowly I think that's about all you can do. We weld different grades of hardening carbon steel to a36 and the like fairly often and the biggest thing is dealing with the initial weld shrinkage causing stress fractures. Once you're past that point, you can basically treat it as a homogenous piece, as long as you heat and quench the whole weldment together.