Question: Un Harden - Engrave - Re Harden

[jimzim75]

So I have a piece of steel that I've taken the hardness out of by heating up
in the kiln. Worked great by the way. This is a tool steel.

So, I'm going to engrave a pattern in it. I will do all this bright cutting and I'm
worried about what happens next.

I have to re harden the steel but what about all that high polish?
I going to have to take it up to hardening temps and then dunk it in oil.

Then it need to be tempered.

What about the finish? I know the steel is going to come out blackened.
I don't think I want to use acid because that would frost the finish.
So that only leaves polishing, but I don't want to round anything.

Suggestions?

 

[vanknife]

Good day Jim,
The Only way to get around the "not to much polish" is to do the hardening in a salt bath that leaves virtually no scale and the discoloration is minimal but to get it to shine you will have to polish it again.

Cheers

"VAN"

 

[jerrywh]

Another thing to consider is warpage. What kind of part are you dealing with?

 

[jimzim75]

Two inch thick cross section on a cyclinder. So I don't think it's going to be a issue,
those could be famous last words.

 

[BJREBUCK]

Jim,
the process you're describing is usually done in heat treating furnaces that are equipped with an inert gas blanketing system.
You might try contacting a tool manufacturer like dave manson or clymer. They should be able to give you some good info.
Brian

 

[McAhron]

Use Brownells Anti-Scale.You apply at 500f and it melts to coat the steel.Then you can heat to hardening temp and quench.The anti-scale washes off with boiling water.It protects the steel from decarb and scale formation.

 

[Arnaud Van Tilburgh]

If I can add something to this, polishing after the steel is hardened is hard to do it the regular way, I learned that the diamond powder liquid we use to polish gravers, put some on a leather flap that is glued on a flat wooden stick. I even use the diamond spray to polish scratches on the ocular and screen of my digital camera. It will polish everyting with some patient

arnaud

 

[rod]

Jim,

I take it that your steel is simple high carbon 'old fashioned tool steel', and not High Speed or other exotic steel? Only high carbon steel is harden-able in a home workshop.

Rod

 

[Roger Bleile]

Two inch thick cross section on a cyclinder. So I don't think it's going to be a issue,
those could be famous last words.

Jim,

Are you speaking of the cylinder of a revolver?

 

[jerrywh]

If that is a cylinder from a smokeless powder revolver I wouldn't want to heat treat it. Or more important, I wouldn't want to fire it after it was heat treated by an armature. You probably have no way of knowing exactly what kind of steel it is. I did one awhile back and S&W did the job for me and proofed it in their shop. I do a lot of heat treating on guns and you need to know what kind of steel it is and exactly what temp to temper it at. Also there is a time factor when it comes to heat treating. A certain temp for a certain time period. The part can be annealed without oxidizing it by fluxing it with a furnace brazing flux and wrapping it in stainless foil. Also it helps a lot to put a piece of titanium in the wrap with the part. Hardening is another trick. The best way I know is to pack it in charcoal in a container, heat to 1450 or 1500F and quench in room temp. water with about 1/8" or transition oil on top of it. This will prevent cracking. The cylinder will not warp. The tempering temp and the hardening temp depends on the type of steel it is made of. This process is critical. the temperatures cannot be guessed at. You need accurate pyrometers and a controllable furnace.
Some of these parts are not heat treated at all. They are just tough or hard steel alloys.
No offence--- that’s just the way it is. I do this stuff very often.
ps. arnaud's trick for polishing works real well.

 

[jimzim75]

Hi Arnaud,
Thanks for the tip about the diamond polish. Excellent idea.

Hi Rogger and Rod,
This is not a gun part but rather a tool part, a die in fact. So I don't have the problem
of it warping because there are no thin cross section that have to deal with expansion
gas from gun power. I would think the steel is high carbon tool steel. Most likely the same
type used for letter hand stamps. I put in the kiln at just under 1000° f for six hours then
let it cool over night. It turned dark but is engrave-able. So I just sanded off the dark
oxide with a fine belt sander.

Hi McAhron,
I just happen to have a Brownell catalogue handy and I think I'm going to try Anti-Scale
stuff. Thanks very much for the tip.

Hi Jerrywh,
Wow, that is some great information. Thanks for being on the forum and sharing.
I would have muddled my way through this but it sure is nice to talk to someone who's
done it before.

This is a large piece of engraving to do, so it's gonna take a while Finnish. I've got to fit
it in between job that pay the bills. I'll keep ya posted on how I make out with the
hardening and tempering part.

Thanks everyone,
Jim

 

[jerrywh]

Jimzim75
I have tried the anti scale also. It works faily well but not as good as the stainless foil and the oven flux. How hard do you want this object to be when your done??

 

[jimzim75]

Since what it's to do is imprint on Silver or gold, it's doesn't have to be that good really.
Just as long as the high spots don't mush over. I suppose for that matter I could probable forgo hardening all together. I just think the die would hold up longer if it's
harden then temper, I don't want to break it in use.

I think I'll try it under use without hardening to see what happens. I have a good look
with the scope to see what the high point are doing. Then if it still needs hardening,
I can pop it in the kiln.