doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Torch job?

if cooked too long, and through hardened, metal takes on the properties of glass. hit it hard and it will shatter...

Ed,
I have done charcoal based Color Case hardening. YOu have a specific temperature (1300-1400 degrees) and a timetable. You dont just take it up to some undetermined high temperature for some unspecified time. That is why there are formulas and recipes that work and have worked for many years.

BS

stallones: glad you have developed methods that work for you. sadly, others have not. the results of their ignorance and experimentation, have created a fair supply of parts guns... a question: if you accept the fact that shotgun receiver metallurgy varies from manufacturer to manufacturer and even varies within manufacturer, depending on period, how do you develop a spec for a receiver you have never done before? it would seem to me, all you can do is guess?

Isn't the reason for case hardening to add enough carbon to a steel for it to have the ability to harden. I believe it takes quite a while for carbon to diffuse, so it may be difficult to turn a low carbon receiver into a high carbon steel that could actually through harden. Doesn't the hard layer end up only being a few thousandths thick.

I believe color casing might be different. I've been curious to know if the steel case on a part actually hardens if it's not quenched from a temperature that's somewhere around nonmagnetic. I've wondered if a wear point is actually hardened if a part is quenched from say 1200*.

craig: wikipedia has an excellent narrative on the subject of case hardening. as you surmise, case coloring is cosmetic enhancement only and does not affect the original heat treatment and hardening of the metal, surface or otherwise.

Not a throughly scientific description, BUT, case hardening is normally done on a low carbon steel which does not have a high enough carbon content to through harden. This can be done with or without the mottled colors, primarily dependent upon the source of the carbon & oxygen in the quench. Animal charcoal & free oxygen both enhancing the colors. At the elevated tewmp, above its critical temp, or the point it becomes non-magnetic, the carbon is absorbed into the steel. The longer it remains at temp the deeper the carbon penetrates, but also the deeper it goes the longer it takes for each additional .001" of penetration. After the part has soaked in the carbon gasses for the requisite time to attain the desired depth of penetration it is given the Quench from still above its critical temp, which is necessary for it to harden. This high carbon layer which is hardened is known as "The Case". The low carbon core is left in an unhardened state. When th process is done in a manner to produce the colors it is commonly referred to as "Color Case Hardening". Realize though the "Case" still refers to the hardened area, the colors are only superficial, being microscopicaly deep. They are strictly speaking "Temper Colors". Technically there is no such creature as Case Colors, as the colors do not form the case. It is noted though these colors are formed in the "Hardening" process, colors brought on by re-heating the part hot enough to produce color is in fact a true tempering process & is drawing or removing the hardness from the case. To produce varied colors with the hot tip of a torch flame tempers out the hardness in a spotty fashion according to the color produced, leaving the case having faried hardness. The colors put on some modern guns having alloy steel frames which are through hardened are done chemically at so low a temp as to have no affect on the hardness, usually no more than about 200�F I believe. These are not temper colors, nor are they produced through the hardening process, but are simply chemical colors. These can be produced by heating a piece of steel to the range of 160�-200�F & "Painting" on the colors with a Q-tip dipped in a cold blue such as Oxpho. They will never produce the colors of those produced through the bone charcoal process of case hardening, but they do no damage to the frame & can be simply & easily sanded off.
ANYONE putting the Hot Tip of an accetylene torch to a gun frame in a manner to give it mottelty temper colors should be given a "Suspended Sentence" of thirty (30) days on the end of a "New Rope".

Ed,
I have to disagree. You know not of what you stated at least twice in this thread. Possibly, you should read a bit on the case hardening process. Metallurgy textbooks are the best source of reliable information on this subject. Gun magazines and such can have annecdotal information from writers that often get technical information incorrect. I recall a completely erroneous statement in an article about carbon/graphite wrapped barrels where the redheaded Col. said this stuff aided in disippating heat from the metal because he could touch the outside of it and little heat was felt.

Thanks 2-piper, this is what I was curious about. Some formation of nice colors seem to be done at a temperature that is below critical. Do you have a ballpark on what critical temps. might be. Again, just wondering not trying to stir anything.

chuck: do you disagree with my referring craig to the wikipedia narrative?

or, do you disagree with my statement regarding case coloring as being cosmetic enhancement only?