Case-hardened?


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ed dixon
May 24, 2003, 11:53 PM
Case-hardening.

I know what it looks like. I like it. But how is it done? What are the advantages? When did it start and why?

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Oracle
May 25, 2003, 12:23 AM
Check out this link:

http://members.aol.com/illinewek/faqs/case.htm

Cadwallader
May 25, 2003, 12:25 AM
I'll give a not-so-professional answer, and I'm sure someone will come along and do better soon. Case hardening is a process that raises the carbon content from the surface inwards on a piece of of wrought iron or low-carbon steel - you take your items to be treated, place them in a high-carbon, low-oxygen environment, and apply heat.

Traditionally, it involved packing the pieces to be treated in a box or case full of powdered charcoal, hence the term case-hardening. I don't know much about modern methods, but traditionally it was done to make hardenable items when there was no access to high-carbon steel or cost of such steel was prohibitive. There are probably applications that call for the properties case-hardening gives (hardenable outer "skin" and softer interior), so I assume that when it's done nowadays it's not for lack of better materials. I'm not sure exactly why it would be used in manufacture of modern firearms, but what do I know?

Mention of case-hardening always makes me thing of "trade knives" that salesmen sold to Native Americans in the 19th century. I own a couple and when you examine them you can see that the users were well aware of the properties case-hardening gives - they are both sharpened with a "chisel" bevel, which puts the edge on the harder "skin" of the blade instead of the soft middle.

Mike Irwin
May 25, 2003, 12:29 AM
Case hardening is done by introducing carbon into the outer layer of mild steel or iron.

If the part is iron, the addition of carbon actually turns the surface into steel.

Traditional methods for case hardening were to pack the part in a source of carbon in a crucible -- charcoal, charred leather, and bone meal were all used -- and then bury it in the forge for a number of hours. The part would take carbon into the surface, producing a layer that could be hardened and that would be a LOT longer wearing than an unhardened piece.

The advantage to case hardening is that while the outer surface is very hard and long wearing, the inner core is ductile. This gives the piece strength and durability but doesn't make it brittle.

Case hardening metals is easy today with a product from Brownell's called Casenit. You simply heat the part red hot, dunk it in the Casenit, then heat it again, and quench.

The first time I did this I tried it on some mild steel nails that were very easy to cut with a file.

After two treatments, I could barely touch the nail with the file.

Mike Irwin
May 25, 2003, 12:34 AM
"I'm not sure exactly why it would be used in manufacture of modern firearms, but what do I know?"

Because it's good for sears, hammer surfaces, revolver cylinders, receivers, etc.

If the entire part is a uniform hardness throughout, it can be brittle and prone to shattering.

This is part of the problem with "Low Number" Springfield 1903 rifles. The steel was over heated, burned, and hardened too much, making the receivers brittle and prone to shattering.

A sear that is hardened the whole way through is very prone to chipping. A revolver hammer that was hardened uniformly through the whole piece could actually shatter.

nextjoe
May 25, 2003, 01:16 AM
Revolver *cylinders*? I've never seen a casehardened cylinder. Could you provide a little more info on this, please? It seems like a bad idea to me.

Best,
Joe

Jim March
May 25, 2003, 01:55 AM
"Case hardened" is when you armor-plate a courthouse.

:neener:

Mike Irwin
May 25, 2003, 02:15 AM
Next,

Sorry, not the entire cylinder, the indexing notchs at the rear of the cylinder, which are actually part of the ejector star on most revolvers.

In the early days of their revolvers S&W had a problem with the lock notches wearing out as the cylinder bolt came up into the notch at the end of the cocking cycle.

A number of solutions were tried, including spot hardening the notch, but the solution that was adopted for some time was to line the notch with a piece of hardened steel.

That's no longer the case, as a process was finally adopted to heat treat and strengthen the cylinder that hardened the notches but didn't slow production.

caseydog
May 25, 2003, 02:55 AM
Case-hardening,I know what it looks like..

I've never seen a casehardened cylinder.

Some of you are confusing "case hardening" which the sole objective is to harden the surface of the steel with "color case hardening" which as well as hardening the surface is used to impart a decorative finish to the object. You can't tell by looking if a part is case hardened.

Many, many parts are case hardened without the added cooling touch to give them the tell tale "rainbow" appearance. And as for use in guns, as Mike Irwin mentioned a revolver hammer is a great candidate , the surface needs to be very hard to withstand 10's of thousands of firing pin impacts and sear disengagements , yet were the entire hammer as hard as the surface ,hammer shatter would be a common occurance.

As for cylinders , while they are not a mild steel by any stretch , the surfaces should be harder than the body to withstand the hand /index wear , and excessive bolt stop wear, but the bulk of the body of the cylinder should be able to "yeild" when subjected to "some" overpressure , rather than exploding. Of course any steel can be pushed past it's limitations , which is why forgetting you have Bullseye in the powder measure when using 2400 data in max loads will pretty much guarantee 100% fragmentation of a cylinder and it's supporting structures. Case

Detritus
May 25, 2003, 04:17 AM
Some of you are confusing "case hardening" which the sole objective is to harden the surface of the steel with "color case hardening" which as well as hardening the surface is used to impart a decorative finish to the object. You can't tell by looking if a part is case hardened.

Casey, you're mostly correct, in that "case hardening" does not always result in the rainbow-like finish, but in recent years non quenched hardning has fallen under "surface hardning, and "case hardning" has come to mean to many if not most "the form that results in the rainbow effect".
and "Color case hardning " is NOT case hardning. but niether is it "hardning".

rather the purpose of CCH is to acheive the mottled, "rainbow" coloration on a modern piece of steel, that on 19th century Era mild steel and iron pieces was attained through the "quenched" form of True "Case Hardening" (note: some, like Doug Trumbull, still use the true Case hardening process on some modern steels to acheive the result but it's rather expensive for use on a non-custom gun, and results vary greatly). COLOR case Hardening is acheveived through any number of chemical finnishing processes. some of the lower end companies that do it dip the peice to be CCH'ed in oil, light the oil then quickly douse it, then spray the piece with a fixative to keep the "finish" from rubbing off. Ruger, like most other "better" companies that offer a "CCH" finish, uses a more resilient "coating" type process (am told it is akin to a thin chemical paint) to obtain the result they want, but like all forms, (including the REAL thing, btw) it fades with use or exposure to sunlight and the elements.

as i understand it the best way to ilistrate the difference is that you can Case Harden iron adn steel, but NOT the likes of aluminum. while "COLOR case hardning" can be acheived on anything that will take the coating.

CZ-75
May 25, 2003, 04:32 AM
A revolver hammer that was hardened uniformly through the whole piece could actually shatter.

Had a couple S&W hammers do this by snapping off at the spur.

nextjoe
May 25, 2003, 12:04 PM
Mike,

Thanks for the info. I hadn't been aware of that. I don't know much about the old Smiths, but the more I learn the more I'm impressed. I think the neatest touch I've seen on the old Smiths is the Triple Lock. They definitely deserve further study.

Best,
Joe

Mike Irwin
May 26, 2003, 02:05 PM
"Had a couple S&W hammers do this by snapping off at the spur."

CZ, that's usually a different process that causes that to happen. That's normally caused by what's known as "crystalization" of the metal, where the metal becomes progressively weaker through a certain point, usually an area of locked in stress.

CZ-75
May 27, 2003, 01:52 AM
Mike,

What's the cure for this problem?

FWIW, S&W always replaced the hammer.

braindead0
May 27, 2003, 09:31 AM
The funny thing about this 'color case hardening' thing is it leaves an inferior unevenly hardened product.. I guess the usual parts for this treatment aren't all that critical, and they probably start with good quality steel anyway....

Mike Irwin
May 27, 2003, 02:41 PM
"What's the cure for this problem?

FWIW, S&W always replaced the hammer."

That's the cure.

Once this happens, as best as I know the only other solution is to take the affected part, melt it down, and start over.

ed dixon
May 28, 2003, 09:36 PM
You know, I meant to say color case-hardened, but the slip generated even more info, so it's all to the good. ("I'm smart! I can do things! I'm not dumb like people say!" Exeunt with two chorus girls/hookers.)

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