Heat treat box material?

Laverda · May 29, 2018

I was going to make a box to case harden a 8620 shaft out of sheet metal. Now I am wondering if I could just use some iron plumbing pipe and screw a cap on each end? I will be stripping off the plating and drill a tiny air hole in one end cap. Any problems with this? Does the material used to make the box make any difference as long as it does not melt? I am assuming the iron pipe once the zinc plating is gone will work OK? It will be in the oven at 1700 degrees for 6 hours.

Rob F. · May 29, 2018

That is an old method used by blacksmiths to heat delicate items. Put pipe in coal forge with part you can not burn up inside the pipe...
You should use black pipe not galvanized pipe. Maybe put a little bit of paper inside pipe with the part or some oil. You need something in there to burn up the oxygen to help prevent scale but you are probably not quite hot enough for that. Do not put the end caps on more than hand tight.
Edit: missread OP and thought heat treat, should be fine for case harden also, just be sure to have the kasenite filling the pipe.

sable · May 29, 2018

The old books refer to a cast iron box ,don't know where you would find them , with your pipe plan ,I would be making the hole a bit bigger than tiny.

Miguels244 · May 29, 2018

I thought stainless foi from McMaster was the thing for shout runs.

atex57 · May 29, 2018

I do enough of this that I made boxes from 304 SS sheet. Be careful you leave it in long enough, I like 6hrs after oven reaches temp.

Ed.

billzweig · May 31, 2018

Any steel for the container is fine. I make the boxes as needed (for a close fit for the part as not to waste too much hardening material) out of #12 (or about) mild steel sheet metal. Black pipe, stainless or cast iron are fine. Steel containers get quite oxidized on the surface and are discarded after a number of runs - in this aspect stainless is better.

steve-l · May 31, 2018

These boxes are called muffles and Inconel is the material of choice. Quite often a flange is welded on one end and machined flat. Then a plate of Inconel is placed across this flange and a vacuum is pulled in the muffle after the part is inserted. Then the muffle is placed in the oven.

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Heat treat box material?

Laverda

Cast Iron

Rob F.

Diamond

sable

Titanium

Miguels244

Diamond

atex57

Stainless

billzweig

Stainless

steve-l

Titanium

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