Case hardening powder, any advise?

[MikeParticipant @mike89748]

Old-fashioned gun makers case-hardened with animal bone charcoal. They put in bits of leather and other substances to produce colour-hardening – a random pattern largely made up of blues and browns.

[GeorgineerParticipant @georgineer]

My great grandfather, an engine smith, used scraps of leather mixed with hoof clippings. I believe he held them in an old leather bike saddle cover.

George

Edited By Georgineer on 20/04/2018 11:25:23

[MWParticipant @mw27036]

interesting question,

can you harden carbon steel, even further by case hardening? or would you consider it redundant at that point.

Michael W

[HopperParticipant @hopper]

Posted by Michael-w on 20/04/2018 13:33:40:

interesting question,

can you harden carbon steel, even further by case hardening? or would you consider it redundant at that point.

Michael W

I suppose it would be like any other steel: if you heat it and shove it in the Kasenit, the outside skin is hardened and the core remains soft and flexible. If you have already hardened the carbon steel, as you say its redundant to harden it any further before tempering back to useful hardness grades. They do make special case-hardening steels with alloys of nickel and chromium etc in them so you get a high tensile very strong but flexible core, with the case hardened outside. Best of both worlds.

[MWParticipant @mw27036]

Posted by Hopper on 20/04/2018 13:48:36:

They do make special case-hardening steels with alloys of nickel and chromium etc in them so you get a high tensile very strong but flexible core, with the case hardened outside. Best of both worlds.

Ah yes, like EN19 or what the U.S would call 4140, is a tough chromium alloy steel. Sometimes called "Chromoly" as well. I have interest in using that for tooling bodies and the like.

I suppose the powder has a tendency to cake (looking at the heated cake dazzles the eye as well) and would therefore make another job to clean up the surface if you wanted a pristine looking body just heating it, without case hardening, would make things easier on you.

Thanks for clarifying that.

 

Edited By Michael-w on 20/04/2018 14:45:00

[RobinParticipant @robin]

I thought that case hardening was good for puddled/wroght iron which is very pure iron with a slag inclusion. Case hardening allowed a thin, glass hard, gall reistant skin to be applied. A very slippery surface that allowed all sorts of unlikely lever systems to work a treat.

However it would not hold a fine edge, which is why they started wrapping iron in leather and toenail clippings etc and then baking them to get carbon in to the surface before melting the whole shebang so they could remove the slag but keep the carbon as an even distribution. The so called crucible steel or Marshall's iron.

Then Henry Bessemer invented his converter c1860, all things became possible and they eventually started introducing lead to stop the iron crystallising and made the material "free cutting" and totally resistant to case hardening.

Case hardening carbon steel is possible but how to harden just the surface? If you temper you lose the glass hard coating that works so well.

I realise my brains are somewhat addled, but I don't think I can be 100% wrong here

[duncan webster 1Participant @duncanwebster1]

All steel is crystalline, the best turbine blades are made from a single huge crystal. Steel with low carbon content cannot be hardened by heat treatment alone. The idea of case hardening is to increase the carbon content at the surface but leave the core soft. You don't then have to temper it.

If the carbon content is above the magic limit (and I can't remember what it is, must be 0.3% or so), you will harden it by electric weoding, as the zone around the weld is rapidly coled from very hot to cool by the surrounding metal. That's why you have to adopt special measures to weld EN8 for instance.

[BazyleParticipant @bazyle]

Don't overdo it. It improves up to about 1% then deteriorates as it becomes cast iron at up to 4.5%. This youtube video shows a guy turning mild steel into cast iron.

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