doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Shooting Fox with annealed frame?

One thing to keep in mind, most barralled actions in England...and other places by that matter go to the proof house before hardening, I think the vast majority pass proof.

This quote from David T's Technicana " at this point ,the gun...essentially a barrelled action with locks, fasteners, and ejectors but lacking triggers and a trigger plate, went back to the Proof House for definitive proof. Then it was ready for the stockmaker"

I would say if they can handle a few heavy proof loads it should be able to take some target loads...just don't overdo it, but it should be re-hardened at some point.

CJ

A "soft" action can bend and spring back under firing stress as long as the strain (deflection) does not exceed its yield strain. If it does then the soft action will bend and stay bent.

Rocket I get your point about the .002" being very thin compared to the rest of the cross section of the action but I make the point again that the strength of a monocoque fusealage is primarily due to the thin skin held in place by bulkheads and runners. And the maximum tension strain is most likely at the surface, as is the maximum compression strain.

Don,
My non-statistical sample of cutting into a couple pieces of case hardened steel leads me to believe that while there is a uniformly hard layer of something like .002-008", there is also a gradient of hardness many times that. I base this on the machining of the steel and the observation of the finish. You can literally see the hardness gradient in terms of shineyness. I estimate that I've seen layers of gradient hardness up to .050". Or at least the gradients of shineyness up to that.

To be blunt and for the safety of the shooter, this Thread needs a short discourse in Metalurgy.
Case hardening and heat treating are too different processes designed to cause two different effects. Heat treating takes steel in its annealed state (annealing raises the temperature after forming to allow the stresses induced during forming to flow and 'anneal' which is actually an atomic process as 'dislocations' induced during forming actually flow to relieve themselves) which was designed to remove the stresses caused by forming and hardens the entire volume by raising the Tensile Stress. Prior to the use of high tensile steel by Winchester and Browning, shotguns were manufactured of lower tensile strength steel and as such the surfaces were not very hard to resist wear of both internal parts and the surface of the action. Case hardening was developed to harden the surfaces and the colors that resulted are a by product of the case process.
After the reciever of a shotgun is annealed for metal work, it is essential that it should both be heat treated correctly and the surface case hardebned properly for safety.
The receiver is probably safe to shoot as the design most likely will not cause catastrophic failure with a mild steel but should be done properly.-Dick
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There are of course numerous processes which fall in the category of "Heat Treating", case hardening being one process in the broad category, IE it "IS" a heat treating process. In actuality, though often combined into a single operation, Case hardening is a two part process. The first step consists of "Carburizing" the low carbon steel to give the outer surface a higher carbon content. 2nd step is then to "Heat Treat" this carburized portion, thus the common name Case Harden.
The carburizing portion consists of bringing thr part to a temp above its critical temp & holding it there in the presence of a carbon rich atmophere for a time suitable to the desired penetration. The longer it is held the deeper the carbon penetrates though the deeper it gets the longer it takes for more depth, so there are practical limits which are not often exceeded.
The Heat treating portion is simply to quench the part in a suitable medium, usually water here, from a tamp above its critical temp. Since the part is already above this temp in the carburizing process it is quite common to simply quench directly from the carburizing, but this is not a requirement. The carburizing & heat treting can be done in seperate operations, though this would require bringing the part up to heat twice.
I totally agree with Chuck here, there simply is not a sharply defined "Line" to which the carbon penetrated & stopped but as he said it simply thins & eventually fades out as you go deeper from the surface. When the carbon content drops too low even though it may still be more than the original alloy as in the center it no longer hardens from the quench.
I believe this is basically what Dick was saying, but his statement seemed to indicate that casehardening was not heat treating, which it of course is.

Rocketman/DDA. I do not agree that the depth of hardness would be .002" A typical figure would be .008" per hour at carburising temperature.Gun actions are held for 1&1/2 - 2 hours so an effective case depth of .012"-.016 would be anticipated.

Thank you, gents, a very good discussion.

Chuck, can you go a bit deeper into the circumstances of seeing gradiant carbon content to the depths you indicated? Gun parts? I don't disagree, but would like to know more. I certainly agree 100%with the gradiant concept, but am surprised at the 0.050" number. 2-p, any input on depths likely for guns? I've heard of depths to 0.150", but only under very special circumstances.

DDA

My sentiments exactly and we're still springing along....

A friend has a Birmingham 16 gauge singleshot hammergun. It was loose when he bought it. He sent it to a gunsmith both he and I consider to be very good. The gunsmith tightened it. My friend took it hunting and fired a few shots. It was loose again. Back to the gunsmith, gunsmith fixed it, back to my friend, no charge. Again my friend shot it a few times and it went loose. Back to the gunsmith. After investigation the gunsmith said that the frame was soft and had been improperly heat treated (after it left the maker) or had never been case hardened and wanted to have it case hardened so it would be springy. My friend, tighter than the proverbial bark-on-a-tree, declined and after the last tightening quit shooting it.

Best,

Mike

Everyone has some different view and experience with CCH. I feel like we have a tendency to mystify this process in gun circles because of the visual aspects of what it provides rather than the mechanical properties it provides.

Everyone should try to level set with some form of reference that is a good baseline and then take individual information as necessary to further your understanding.

The key here is that first and foremost case hardening is a heat treatment process for low carbon steels. First understand how they did it then and now.

From there you can work out how to translate the extra effort to get to CCH, which just adds the colors.

Get a baseline from some place like Wikipedia or buy a book on the heat treatment of metals.

http://en.wikipedia.org/wiki/Case_hardening

Then add to it:

http://www.doublegunshop.com/doublegunjournal_v7i4_9.htm
http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=113

I love these forums but in all the posts it can sometimes be hard to put all the different parts provided by different knowledgeable folks into the right order to fully see the puzzle you are trying to build and solve. Take a step back and find a reference that allows you to level set so when reading all the good posts you can put them into the right order.

Jason