doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com CC of Modern Guns?

MS - bearwith me here. I didn't catch you distinction between case hardening and case hardening in colors.

Are you saying only plain carbon steels of carbon content below about 0.4% can be case hardened?

What about coloring of higher alloy steels (little less than "true" CC colors - more oxide color) at oxide formation temperatures?

I could be wrong on this one, but I was of the opinion that many Mausers were "Selectivly" case-hardened Ie only in areas where needed as on the bolt lug seats etc. Many will give a soft reading if checked on the receiver ring etc, but are properly hardened where essential. It may well be noted that German custom makers follow several practises that are frowned upon by "Conservative Americans". A couple in addition to the CC that comes to mind is converting J bore 8MM to S bore by increasing the bullet seat dia & adding a longer leade as well as cutting those humongus dovetails for a claw mount block across the top of the receiver ring. Everyone just has to choose what they are willing to risk.
Personally I am of the opinion that a C-scale penertrator would break through the normal depth of case on a CC-hardened surface & the reading would be of little use.

What is the difference between case hardening with a carberizing process or a nitrating process? Don't they case harden without the colors of color case hardening. I think Miller is correct, that color case hardening has much less depth, than the other two.

Craig

Rocketman-

It is a lot like the old saying from when I was a kid, "Not all people with long hair are hippies, but all hippies have long hair."

Not all "case hardening" is "color casehardening", but all color case hardening is case hardening. I did not just re-read my earlier posts, but i tried to keep it straight and make the distinction by mentioning "color", "color casing", "CC'ing", and similar terms when referring to the process of color case hardening.

You can case harden a lot of steels, but it does not mean you should CC a part that is to be used in a gun. Typical "modern" steels used in guns today should not be color case hardened. THat is what the original question posted here was asking about. People are CC'ing tool steels for purely cosmetic reasons and winding up with a part with a weak and "undurable" finish, as well as a gun part that has compromised mechanical properties.

That is my question, MS. In terms of effect on the steel, the colors are mostly a by-product. You can color the steel without case hardening. Equally, you can case harden without getting colors. Are you saying that the desire for case colors is leading people to case harden parts that are of unsuitable steels just for the colors?

As far as I know, all steels can have a case of higher carbon alloy applied via the case hardening method. The more complex and higher carbon the base alloy, the more likely the extra carbon of the case layer will be of no benefit and the more likely it will lead to a crack. However, I don't see where modern medium carbon steels like 4140 would have a problem. Which "tool" steels are you refering to as being used for gun parts?

I agree that normal Rockwell testing would not give useful results on normal case hardening.

This is I believe "Technically" true.
However, here is a quote from Machinery's Handbook (old edition) "A low-carbon steel containing, say, from 0.15 to 0.20 percent of carbon is suitable for casehardening. In addition to straight-carbon steels, the low-carbon alloy steels are employed. The alloys add to casehardened parts the same advantageous properties which they give to other classes of steel."
From another section after defining carburizing (heating the part in a carbon rich enviroment until it absorbs a "Skin" of high carbon alloy);
"When a carburized object is rapidly cooled or quenched in
water, oil, brine, etc, from the proper temperature, this case becomes hard, leaving the inside of the piece soft, but of great toughness."
The key here is these low carbon steels are not subject to through hardening, the low carbon core not responding to the quench, this is however not the case when higher alloys are used. In this case either the core properties or the case properties will not be that desired. Heat-treated steels having a higher alloy of carbon will "Normally" be tempered or "Drawn" to a higher temp in order to give desired properties to the part than will that of a case-hardened part. To draw to these temps would simply wipe out the advantages of the case.
This leaves us with the fact on these steels it would be for decorative purposes only. The risk of detrimental properties is to me simply too great for me to risk on a gun of mine.
But then of course I am not real keen on "Re-Casing" older guns anyway, as there is still a certain amount of risk involved. My "Field grades remain field grades, so have had no reason for annealing an action, thus no reason other than cosmetic for re-casing. I have simply learned to enjoy them as they are.

It all depends on the steel and the temps. If someone treats 4140 to get "case colors" then you are operating at different temps than you operate at to get the best mechanical properties. The part would show colors that are the fad now, but the life and usefulness of the part would be compromised. If you treat 4140 to have the best mechanical properties, then you will not have the en vogue colors...but then part will be able to function with reduced chance of failure for along time.

The colors on the old doubles were just a by-product of the hardening process and were originally polished off. Then the colors became cool and folks started leaving them showing on the external metal part. But they were not color casing just for beauty's sake-it was a by-product of the treatment required to give a part the required mechanicla properties.

Some steels can be color case hardened and still be OK for certain applications. 8620 is incredibly tough when case hardened for maximum strength. It is still pretty tough when color case hardened and would work fine for lower pressure rounds. But the temps require for the operations are different, so color casing 8620 for use in an application that would use a "modern" high intensity cartridge is not a good idea. Say a single shot with an 8620 frame could be color cased and used in an old BPE cartridge operationg at the lower pressure The same frame could be colored for maximum toughness and stand up just fine to a 7x65R, but the required temps for this treatment will not going to give you the colors that are the fad these days.

Marc,
Oscar left me with the distinct impression that Turnbull had developed a process where coloring was accomplished (maybe not casehardening?) and thru hardening to desired levels was accomplished. I'm hoping Doug Turnbull can enlighten us.

I found the saved post from Oscar.

Btw Jerry Kuhnhausen and R.A Walsh definately both work on the RC scale, if it's good enough for them to use as reference it's good enough for me.

Arnold, I recall this post of Oscar's. But, I believe 4140 will begin to temper in the 400-500F range