4350 tempering question

[MarriedWithAnvils]

I found some properties for the 43xx family of alloys that would seem to apply to 4350, too, but the tempering color for a spring swage is a bit of a mystery to me. Does anyone know generally what I want for a spring swage that will not be used under a power hammer? Do I want straw color, or a bit darker into bronze/purple? I want to minimize deformation while also minimizing brittleness, but not sure what I'm supposed to target for a tool like this. I've never made one before. The 4350 blocks (x2) are just an inch thick each, and about 1.5" long each. They are connected with a 3/8" mild steel bar that acts as the spring. I will be hammering on this to put texture into round bar accents, so nothing really major in terms of striking. Thank you for your kind advice.

[anvil]

You can't harden and temper mild steel.

[George N. M.]

Dear Married:

Since 4350 has about 50 points of Carbon along with Molybdenum, Chromium, and a few other things it should be oil hardening.  For tempering only experimentation will tell but I'd start out with a blue to purple temper and then see how springy that is.  If too stiff go to a lighter blue.  If too soft go more towards purple.  You don't need a lot of springiness for a spring swage, just enough to lift the top half of the swage up between strokes. 

"By hammer and hand all arts do stand."

[MarriedWithAnvils]

10 hours ago, anvil said:

You can't harden and temper mild steel.

I’m not trying to harden and temper mild steel. The spring is not the part I’m talking about. Sorry if that wasn’t clear. The swages attaches to the mild steel spring are what I’m referring to that are 4350 steel. I know I can’t harden and temper mild steel.  

8 hours ago, George N. M. said:

Dear Married:

Since 4350 has about 50 points of Carbon along with Molybdenum, Chromium, and a few other things it should be oil hardening.  For tempering only experimentation will tell but I'd start out with a blue to purple temper and then see how springy that is.  If too stiff go to a lighter blue.  If too soft go more towards purple.  You don't need a lot of springiness for a spring swage, just enough to lift the top half of the swage up between strokes. 

"By hammer and hand all arts do stand."

Thanks George. I’m not making the spring out of 4350, just the swages that are attached to it that will be hammered upon. Sorry if I gave the indication that the spring itself would be 4350. The spring is simple mild steel, which I know can’t be hardened or tempered. I will have to just experiment like you said, but I will likely go with a darker straw first, which should be tough to prevent deformation while being soft enough to prevent shattering. Thanks!

A picture can help. The square swages are 4350; the bar spring is mild steel. Just need to harden and temper the pieces which will be hammered to create the pattern. I know to harden will be to take it to around 1500F and then oil quench. Then when still warm, temper to desired color. Will do it slowly to do a thorough harden rather than just surface harden (right?).

[ThomasPowers]

I'd start with purple and see how it works with the stuff I was doing and then switch either way depending on my druthers.