RM
May 6, 2006, 04:18 PM
What is "case hardening" and why are guns "case hardened?" And why does the process result in "case hardened colors?" Thank you.
What is "case hardened?"
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mbs357
May 6, 2006, 04:21 PM
I've never heard of this. D=
I'd like to know as well.
I'd guess that it has something to do with the case hardening and not expanding to seal the chamber?
I'd like to know as well.
I'd guess that it has something to do with the case hardening and not expanding to seal the chamber?
GunnySkox
May 6, 2006, 04:37 PM
It's a treatment applied to a metal part to make it more durable.
http://en.wikipedia.org/wiki/Case_hardening
Case hardening or surface hardening is the process of hardening the surface of steel whilst leaving the interior unchanged. The idea behind case hardening is to have two different types of steel in the same item. This allows a relatively soft, tough core of a component to be combined with a hard (but potentially brittle) surface. Case hardening improves the wear resistance of machine parts without affecting the tough interior of the parts. Many processes are available for surface hardening.
Example pictures:
http://www.lonestarrifle.com/images/casecolr.gif
From www.lonestarrifle.com
http://www.trapdoorcollector.com/pics_html/turner.jpg
From www.trapdoorcollector.com
~GnSx
http://en.wikipedia.org/wiki/Case_hardening
Case hardening or surface hardening is the process of hardening the surface of steel whilst leaving the interior unchanged. The idea behind case hardening is to have two different types of steel in the same item. This allows a relatively soft, tough core of a component to be combined with a hard (but potentially brittle) surface. Case hardening improves the wear resistance of machine parts without affecting the tough interior of the parts. Many processes are available for surface hardening.
Example pictures:
http://www.lonestarrifle.com/images/casecolr.gif
From www.lonestarrifle.com
http://www.trapdoorcollector.com/pics_html/turner.jpg
From www.trapdoorcollector.com
~GnSx
Jim March
May 6, 2006, 05:39 PM
Modern metallurgy doesn't require case hardening except for cosmetics if you want to make a gun look old-school. A few manufacturers (Ruger and Uberti/Beretta) do fake coloring of this sort on traditional looking guns.
The original process took low-carbon-content steel and implanted carbon into the surface, hardening it. Hard steel is brittle. If it was hard all the way through it would shatter, so they leave the softer core in.
They heated the metal in a pile of coals that had carbon-containing materials in it. Swordmakers did similar things for a long time...one trick was to add animal parts to the coals, ground up bone for example, to increase the carbon content. Which is why steel was said to be "alive", they would "feed it".
The case-hardened appearance is from heat-implanted carbon and other impurities added along with it.
(The other way to get different parts of the metal at different hardnesses was differential tempering - cooling different parts of the metal at different speeds. This was common in swords and knives but I'm not aware of it being done in guns. I'd be curious if it was. Probably not, it tends to warp things...the curve of a Japanese sword comes in large part from hardening the edge and leaving a softer spine and core behind...)
The original process took low-carbon-content steel and implanted carbon into the surface, hardening it. Hard steel is brittle. If it was hard all the way through it would shatter, so they leave the softer core in.
They heated the metal in a pile of coals that had carbon-containing materials in it. Swordmakers did similar things for a long time...one trick was to add animal parts to the coals, ground up bone for example, to increase the carbon content. Which is why steel was said to be "alive", they would "feed it".
The case-hardened appearance is from heat-implanted carbon and other impurities added along with it.
(The other way to get different parts of the metal at different hardnesses was differential tempering - cooling different parts of the metal at different speeds. This was common in swords and knives but I'm not aware of it being done in guns. I'd be curious if it was. Probably not, it tends to warp things...the curve of a Japanese sword comes in large part from hardening the edge and leaving a softer spine and core behind...)
Jim Watson
May 6, 2006, 06:20 PM
As said, case hardening of iron or steel is in general done by heating the part in a source of carbon like charcoal and then quenching it to "freeze" the surface in a harder crystalline form. The core, lacking the extra carbon, does not harden or not as much, and is left tough and resillient.
If the carbon is uniform and the quench clean, all you get is a hardened gray surface. The case colors are due to unevenness in the carbon source, as caused by different size bits and pieces of wood, leather, and bone charcoal; and to impurities in the quench. Under controlled conditions, the quench water will have such things as potassium nitrate dissolved and will be aerated by air injection into the quench tank.
You can use other hardening processes. The British term for such is "cyanide mottling." Heat steel in molten sodium and/or potassium cyanide to add carbon and nitrogen to the surface, then quench in aerated potassium nitrate solution and you get a color display.
The different hardening mixes and different quench methods and materials give distinctive color patterns. The real experts can distinguish between makes of guns just by the patterns. The CPA Stevens reproduction has a wave pattern in the colors unlike any other I have seen.
If the carbon is uniform and the quench clean, all you get is a hardened gray surface. The case colors are due to unevenness in the carbon source, as caused by different size bits and pieces of wood, leather, and bone charcoal; and to impurities in the quench. Under controlled conditions, the quench water will have such things as potassium nitrate dissolved and will be aerated by air injection into the quench tank.
You can use other hardening processes. The British term for such is "cyanide mottling." Heat steel in molten sodium and/or potassium cyanide to add carbon and nitrogen to the surface, then quench in aerated potassium nitrate solution and you get a color display.
The different hardening mixes and different quench methods and materials give distinctive color patterns. The real experts can distinguish between makes of guns just by the patterns. The CPA Stevens reproduction has a wave pattern in the colors unlike any other I have seen.
RM
May 6, 2006, 06:34 PM
Thanks, Gentlemen, for the excellent replies! So why is case hardening no longer necessary?
billybob
May 6, 2006, 07:00 PM
Heat treating takes care of it now.
The "case" that was hardened was the OUTSIDE of the hardened piece. The inside of case hardening is not that hard.
The "case" that was hardened was the OUTSIDE of the hardened piece. The inside of case hardening is not that hard.
Onmilo
May 6, 2006, 07:09 PM
Steel from one hundred twenty five years ago was really nothing more than highly refined iron.
That steel contained a high carbon content but the forgers did not have the capability of regulating the dispersion of the carbon throughout the structure of the iron.
Hot rolling the molten metal compressed the iron/carbon mixture and produced steel
Consequently this iron/steel featured weak spots the could not be regulated or controlled.
Cold rolling, which refines and compacts the steel, wasn't widely employed in the ninteenth century.
Most steel was hot rolled and machined as is.
Casehardening the iron/steel after machining placed a hard surface on top of the composition in an effective attempt to provide a tough but shallow surface that would not allow the iron/steel to fracture under repeated impact stresses.
Modern steel is much more regulated in the dispersion of carbon/iron (stellite) through the structure of the base iron (hellamite).
Additions of chromium and molebdenum among other much more advanced metal inclusions have stabalized steel structures to the point that the once produced, cold rolling and furnace heat treating will produce a steel that can be exactly controlled in the depth of the hardening without the need for surface case hardening.
Case hardening is still utilized in steel production, it just isn't neccessary for the production of safe gun grade steel any longer.
That steel contained a high carbon content but the forgers did not have the capability of regulating the dispersion of the carbon throughout the structure of the iron.
Hot rolling the molten metal compressed the iron/carbon mixture and produced steel
Consequently this iron/steel featured weak spots the could not be regulated or controlled.
Cold rolling, which refines and compacts the steel, wasn't widely employed in the ninteenth century.
Most steel was hot rolled and machined as is.
Casehardening the iron/steel after machining placed a hard surface on top of the composition in an effective attempt to provide a tough but shallow surface that would not allow the iron/steel to fracture under repeated impact stresses.
Modern steel is much more regulated in the dispersion of carbon/iron (stellite) through the structure of the base iron (hellamite).
Additions of chromium and molebdenum among other much more advanced metal inclusions have stabalized steel structures to the point that the once produced, cold rolling and furnace heat treating will produce a steel that can be exactly controlled in the depth of the hardening without the need for surface case hardening.
Case hardening is still utilized in steel production, it just isn't neccessary for the production of safe gun grade steel any longer.
Jim Watson
May 6, 2006, 07:10 PM
It IS still necessary, if you want the specific physical properties of a surface harder than the core. Tennifer, Mellonite, QPQ, etc., etc. are just brand names of modern high tech, high speed, uniform property case hardening. Still common in guns and a lot of other machinery. Just not colored.
dfariswheel
May 6, 2006, 07:12 PM
Case hardening has two purposes.
One is to harden the surface to prevent wear.
The second is as a decorative finish, and is known as "Color Case Hardening".
Standard case hardening is NOT the beautiful mottled colors as shown above, in fact, you can't detect case hardening by appearance.
Color case hardening is a process involving sealing the parts in an air-tight steel drum with a mixture of charcoal, charred leather, bone meal and other ingredients.
When the drum is heated, the parts take on the typical mottled colors of color case hardening.
These colors are actually fairly fragile and are easily worn away.
In modern guns case hardening is still used.
As an example, modern MIM (Metal Injection Molded) parts have a thin case hardened coating to make the part wear better, while retaining the softer, tougher core.
The reason case hardening isn't used on receivers and many other gun parts is, modern metallurgy can harden steel much more reliably than in past years, and this process is cheaper than case hardening most parts.
In short case hardening of parts has been overtaken by modern science and production techniques.
Always remember, there's a difference between case hardening and COLOR case hardening.
One is to harden the surface to prevent wear.
The second is as a decorative finish, and is known as "Color Case Hardening".
Standard case hardening is NOT the beautiful mottled colors as shown above, in fact, you can't detect case hardening by appearance.
Color case hardening is a process involving sealing the parts in an air-tight steel drum with a mixture of charcoal, charred leather, bone meal and other ingredients.
When the drum is heated, the parts take on the typical mottled colors of color case hardening.
These colors are actually fairly fragile and are easily worn away.
In modern guns case hardening is still used.
As an example, modern MIM (Metal Injection Molded) parts have a thin case hardened coating to make the part wear better, while retaining the softer, tougher core.
The reason case hardening isn't used on receivers and many other gun parts is, modern metallurgy can harden steel much more reliably than in past years, and this process is cheaper than case hardening most parts.
In short case hardening of parts has been overtaken by modern science and production techniques.
Always remember, there's a difference between case hardening and COLOR case hardening.
Clipper
May 6, 2006, 07:12 PM
Case hardening isn't necessary today because the metalurgy has advanced to the point that modern alloys are tough enough to withstand service in a firearm, without being brittle. 4140 steel is an excellent and widely used example. It can be tempered in a wide hardness range, and is extremely tough and very wear resistant. It is probably the most widely used non-stainless alloy in gunmaking.
mbs357
May 6, 2006, 07:28 PM
lol!
I guess it has nothing to do with cases. =D
I guess it has nothing to do with cases. =D
Husker1911
May 6, 2006, 07:40 PM
Lucky for you that you don't know my ex-wife..................................:) :barf: :eek:
Detritus
May 6, 2006, 07:43 PM
I guess it has nothing to do with cases.
earliest reference i've run across to the term "case hardening" reffered to making hardened steel "bodkin point" arrow heads (AP rounds for the medieval archer). it spoke of "case hardening" as a term coming from a blacksmith hardening the points by packing them in an iron box along with charcoal, bonemeal, etc and then placing the iron "case" under the coals of his forge for a time to heat and absorb carbon to harden.
earliest reference i've run across to the term "case hardening" reffered to making hardened steel "bodkin point" arrow heads (AP rounds for the medieval archer). it spoke of "case hardening" as a term coming from a blacksmith hardening the points by packing them in an iron box along with charcoal, bonemeal, etc and then placing the iron "case" under the coals of his forge for a time to heat and absorb carbon to harden.
nadeem
May 7, 2006, 07:36 AM
heated to cherry red and dipped in carbon powder. gives the outside a much tougher and harder case. therefore it will resist to denting, scratching and corrosion much better. (this is for steel or iron)
Jim Watson
May 7, 2006, 08:49 AM
I don't know why you guys keep saying case hardening isn't "necessary."
Tell Glock that it "isn't necessary." Tennifer is an industrial carbo-nitriding surface hardening process that gives a hard case and tough core. It has helped them sell a bunch of guns over the last 30 years.
There are alloys you can pick out of the steel catalogs specially formulated for case hardening by various methods.
Case hardening isn't "necessary" only if you take it to mean only pack hardening in charcoal and exclude other methods of getting the same results.
Dumb author story: The Lovejoy antique dealer/detective character by Johnathan Gash once explained that "case hardening" was the appearance taken on by an item (a flintlock dueling pistol in the particular story) that was left undisturbed in a closed *case* for many years.
Tell Glock that it "isn't necessary." Tennifer is an industrial carbo-nitriding surface hardening process that gives a hard case and tough core. It has helped them sell a bunch of guns over the last 30 years.
There are alloys you can pick out of the steel catalogs specially formulated for case hardening by various methods.
Case hardening isn't "necessary" only if you take it to mean only pack hardening in charcoal and exclude other methods of getting the same results.
Dumb author story: The Lovejoy antique dealer/detective character by Johnathan Gash once explained that "case hardening" was the appearance taken on by an item (a flintlock dueling pistol in the particular story) that was left undisturbed in a closed *case* for many years.
Hawkmoon
May 7, 2006, 11:30 AM
My question is this: With modern metallurgy replacing the *need* for case hardening in firearms, is the "color case hardening" that we see on modern replica firearms (such as, for example, the Uberti SAA clones) really color case hardening, or is it just a chemically-applied finish that approximates the appearance of color case hardening?
If it is just a finish (and I suspect that it is), aren't manufacturers and/or vendors who advertise it as "color case hardening" engaging in deceptive (or even fraudulent) advertising?
If it is just a finish (and I suspect that it is), aren't manufacturers and/or vendors who advertise it as "color case hardening" engaging in deceptive (or even fraudulent) advertising?
Jim Watson
May 7, 2006, 12:10 PM
Ruger chemically mottles their cast Vaquero frames to resemble color case hardening.
USFA says their high grade guns are Armory Bone Case finish. Does that mean they are really pack case hardened and quenched for good color? Or is that just a brand name for blotchifying chemistry?
Cimarron imports some of their Ubertis in the white for true color case hardened finish in the USA.
I think Colt still does it the old fashioned way.
All of the above have sent guns out to Doug Turnbull for really nice really real color case hardening in high priced editions.
I don't know about the usual run of Eyetalian clones.
USFA says their high grade guns are Armory Bone Case finish. Does that mean they are really pack case hardened and quenched for good color? Or is that just a brand name for blotchifying chemistry?
Cimarron imports some of their Ubertis in the white for true color case hardened finish in the USA.
I think Colt still does it the old fashioned way.
All of the above have sent guns out to Doug Turnbull for really nice really real color case hardening in high priced editions.
I don't know about the usual run of Eyetalian clones.
Cosmoline
May 7, 2006, 12:40 PM
By the 1890's advanced arsenals had learned how to case harden without leaving the splotches. Early Mosin-Nagant receivers and other firearms in that vintage were case-hardened, but never had the "old timey" look to them from surface impurities. They've held up extremely well over the century.
LexusNexus
May 7, 2006, 01:18 PM
Isn't it ironic that back in the days they left undesirable blotches and worked hard to get rid of it, and then eventually could do it w/o blotches, and now there's not even a need to case harden with modern steel, yet now peole want blotches back for cosmetic purposes.
zeke1312
May 7, 2006, 02:08 PM
I kinda remember in machine shop while in high school 1959, we case hardened steel by heating the steel object to a cherry red, dipped the item in a powder mixture of sulphur (sp) and carbon (as I remember!) then watching for the color(s) change on the objects surface. After reaching the desired color (which also determined the hardness,) quenching the item in cold water. Too hardened made object brittle, subject to breaking, too little, softer than desired. Spent 2 yrs in that shop course, loved it!:)
Onmilo
May 7, 2006, 05:35 PM
Mellonite and tenifer are modern techniques that allow cheaper formulas of steel to be used in gun grade production.
I understand what Jim Watson is trying to point out and he is correct that those treatments are a very modern form of casehardening.
Mellonite is a surface treatment that is applied to high quality gun grade steels to improve surface wear resistance and increase the steels ability to resist all forms of corrosion be they oxidizers or chemical corrosives.
Tennifer reacts the same way but also allows softer, more machinable, grades of steel to be used in gun production.
I don't know the exact composition of Glock internal steel, I haven't sectioned anything and had it spectroanalyzed by a lab and they keep the exact fusing process a closely guarded secret.
I understand what Jim Watson is trying to point out and he is correct that those treatments are a very modern form of casehardening.
Mellonite is a surface treatment that is applied to high quality gun grade steels to improve surface wear resistance and increase the steels ability to resist all forms of corrosion be they oxidizers or chemical corrosives.
Tennifer reacts the same way but also allows softer, more machinable, grades of steel to be used in gun production.
I don't know the exact composition of Glock internal steel, I haven't sectioned anything and had it spectroanalyzed by a lab and they keep the exact fusing process a closely guarded secret.
Jim Watson
May 7, 2006, 05:47 PM
Such corporate literature as I have seen says that Tennifer and Mellonite are just trade names for the same product... surface carbo-nitriding of steel.
I don't know what you mean by "fusing process" but I suspect the only closely guarded secret of Glock's materials of construction is how ordinary they are. Has turned out to be the case with about every other product on the market.
I don't know what you mean by "fusing process" but I suspect the only closely guarded secret of Glock's materials of construction is how ordinary they are. Has turned out to be the case with about every other product on the market.
AJAX22
May 8, 2006, 03:32 PM
My friends and I used to gheto case harden homeade knives by heating them up almost white hot then sticking them in a jar of sugar. then heating them up red hot and quenching in oil.
gave a rather nice finish and a pretty hard edge, although if it was too thin, it would get brittle at the edges.
gave a rather nice finish and a pretty hard edge, although if it was too thin, it would get brittle at the edges.
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