Why your stainless steel 1911 rust, 434 words

Good post Metalsmith. On target as usual.

Just to add more useless info.......

300 series Stainless is austenitic
400 series Stainless is ferritic.

That's why 400 is magnetic (austenitic vs ferritic refers to a different crystal structure in the alloy). And the lower Cr content of 400 series SS drops the corrosion resistance and also causes the shift to a ferritic structure. If I remember right you need about 12% Cr to have an austenitic steel.

Additionally, 416 often has trace elements added to improve machinability (such as Sulfur).

300 series Stainless is hardened by working the metal (e.g. cold rolling)and can be cold worked to extremely high yield strengths. while 400 series are heat treated. The beauty is that you can heat treat after machining, although controlling dimensions during heat treat is another trick in itself. You can also alter the heat treat regimen to get the hardness you want.

One thing I've always wondered - why isn't 17-7 or 17-4 PH used in guns? To my mind the stuff would have desirable characteristics for guns (good corrosion resistance AND heat treatable). The low temp heat treats would be desirable also. Anyone know? Metalsmith?

[This message has been edited by JiminCA (edited 04-07-2001).]

Hello Gentlemen,
To answer a few questions: Shane45, I don't build that many SS pistol to say one is better than the other, but I hear no positive comments from pistolsmiths that one is better than the other. Most companies don't advertise what they use and I guess they may want to keep it a "secret". I do know in fact what some manufacturers use but they don't advertise it so I don't feel I'm at liberty to reveal it for them on a public forum. I do know Kimber's & Springfield's frames are heat-treated to help with the galling and Colt's are not heat-treated but I find their slides a little extra hard. I do feel my post in on target for general uses. Caspian did advertise at one time they used 17-4 stainless, I think Ruger also uses it and the Randels, These castings were probably all done at Ruger's Pine Tree Investment casting plant in AZ. To why it's not used in more guns is probably because of the tough machine ability. I have machined these frames and they are TOUGH. 17-4 PH (PH is for pre-heat-treated at the mill) is some tough stuff to machine, very strong steel, it's used for drive shafts for props on big diesel powered work boats and specified for shafts on nuclear subs. Guy came to locally and needed a drive shaft for his work boat cut 8', treaded, key way and bearing fit. Someone gave him a piece of 1-1/2" 308 grade stainless steel, I told him use the right material 1- 1/4" 17-4 PH, cost $368.00 for the shaft and I would cut the tread, key way, fit bearing for 50 bux and a case of beer (the marina wanted $800.00 for the same shaft). He got someone else to turn the 308 shaft, it worked ok till he let someone else drove the boat and they laid on the throttle with a full load and rung the 1-1/2" shaft off, of course the price when up when he came back.
fanof1911's: I'm sorry if I confused you a little, yes 416 and 416 SS are the same. For bore cleaners I like regular good old Shooters Choice # 7 or Hoppes # 9, most cleaners will tell you if there high in ammonia like Sweets 7.62, you have to check before you buy. I really don't think it's that big of a deal to worry about and if you have a heavy copper fouled barrel I wouldn't hesitate to use the ammonia base cleaner but if I had a heavy fouler I would fire-lap the barrel to improve the accuracy and get rid of the fouling problem.
Thank you Blindhogg and JiminCA for the help, it's tough to give a metallurgy class in a few paragraphs, my post is meant to be basic so I don't get in to deep. Thanks again, MetalSmith

Hi tetly,
My daughter typed this for you from the book,(she types much faster then me) thank you Ociebell for the help, your post was good. Chrome-moly steel is used in rifle barrel, race car frames, moter shafts, it's very strong steel. MetalSmith

Chromium is used in constructional alloy steels primarily to increase harden ability, provide abrasion-resistance, and to promote carburization. Of the common alloying elements, Chromium is surpassed only by manganese and molybdenum in its effect on harden ability.

Chromium form the most stable carbide of any of the more common alloying elements, giving to high-carbon chromium steels exceptional wear-resistance. And because its carbide is relatively stable used to high temperatures, chromium is frequently added to steels used to high temperature applications.

A chromium content of 3.99% has been established as the maximum limit applicable to constructional alloy steels. Contents about this level place steels in the category of heat-resisting or stainless steels.

Molybdenum exhibits a greater effect on harden ability per unit added than any other commonly specified alloying element except manganese. It is a non-oxidizing element, making it highly useful in the melting of steels where close harden ability control is desired.

Molybdenum is unique in the degree to which it increases the temperature tensile and creep strengths of steel. Its use also reduces a steel's susceptibility to temper brittleness.

Vanadium improves the strength and toughness of thermally treated steels, primarily because of its ability to inhibit grain growth over a fairly broad quenching range. It is a strong carbide former and its carbides are quite stable. Harden ability of medium carbon steels is increased with a minimum effect upon grain size with vanadium additions of about .04% to .05%; above this content, the harden ability can be increased with the higher vanadium contents by increasing the austenitizing temperatures.

Wow! This is great information! Thanks for taking the time to answer. So, I guess the high strength and high-temp resistant steel would be the type they'd use to make engine piston sleeves/cylinder liners in internal combustion motors, etc.

As long as everybody is being so helpful, could you tell me, in layman's terms, what causes metal fatigue? For example, back in the 1950's, the UK's first commercial jetliner, the DeHaviland "Comet" suffered a series of crashes due to metal fatigue in its skin, apparently traced to one of the corners of a square window. It was caused by routien cabin pressurization and de-pressurization cycles. Does the "stretching" of the metal cause its molecular "bonding" to weaken, thereby causing catastrophic failure?--just guessing. If so, why? I think I may have know this at one time, maybe back in high school chemistry. I hate to admit that I've forgotten. I know I'm off topic here, so please feel free to move me to the Off-topic section.

[This message has been edited by tetley (edited 04-08-2001).]

The beauty of the precipitation hardening process is that it occurs at relatively low temps. Low heat treat temperatures equal less distortion of the workpiece

For instance, my book says 17-4PH can be hardened at 900 deg to Rc of 44, yield strength (YS) of 185,000 psi.

For reference the annealed condition 17-4 material is Rc 34, YS 110,000psi.

416 has to be heat treated at between 1850 and 1950 degrees, and quenched (in air for small pieces or oil for larger pieces). High temps and quenching can alter the dimensions of the part.

BTW 416 is 12.5-13% Chromium, .75% Nickel (max)
302/304 is 17-20% Cr, 8-10% Ni
17-4 is 15-17.5% Cr, 3-5% Ni

You can read all of this in a good metal supplier's catalog. They give you all the useful info you really need without all the engineering/metallurgist mumbo-jumbo. (I'm an engineer and I've learned more from these books than I ever learned in school).

Good thread guys

hey tetley, about your question on fatigue and the Comet. Fatigue happens when a material is exposed to a high number of cycles of it being loaded to a certain stress. The paper clip analogy is usually used and works well, if you bend a paper clip back and forth enough times, eventually it will break. By bending the paperclip, you are in essence putting the paperclip cross-section under repeated cycles of compression and tension. What happens is that each time you load the material, you weaken it a bit. Enough cycles and eventually the material will fail.

The number of cycles that a material can sustain before failure is dependent on the magnitude of the loading. The lower the material is stressed for each cycle, the more cycles it can take before failure. Some materials such as steel will not fail for an infinite number of cycles if the applied stress is kept below a certain level. On the other hand, aluminum does not have this cutoff point where it can take an inifinite number of cycles. Eventually it will fail no matter what stress is applied.

As for the Comet problem. The Comet was the first plane to use a pressurized cabin. Each time the plane would take off the cabin would be pressurized, and when the plane landed the cabin would be depressurized. So in essence, each time the plane made a trip, the cabin was exposed to a cycle of loading. Since this was the first use of a pressurized cabin, the engineers did not take fully into consideration this cycle of loading on the aluminum cabin and the fatique that would result. The square windows simply made the problem worse. Square corners in a material will create a stress concentration at the corner. This means that the stress at the corner will be much higher than in the body of the material. As a result, due to higher stresses at the corners at the windows, the initial cracking from fatigue occured at the window corners first. Once a crack starts, it simply proprogates under each cycle of loading, until complete failure occurs.

I hope this has been of some help. I believe everything stated above is correct, but I could of accidently mis-stated something, so if anyone can verify my statements, feel free.

[This message has been edited by jason h (edited 04-12-2001).]

CJ, thanks. You may be correct. 17-4 in the heat treated condition is some touch stuff.

Jason, good post. Let me add a little history to the Comet. When they started to just fall out of the sky, nobody could figure out why. It was by accident only that they noticed that the number of take offs and landings for each aircraft that crashed was approximately the same. This was the first clue pointing to cyclic fatique. They took a Comet out of service, took the wings off of it, put into a water tank, and pressured the cabin to simulate take off/landing sequences. It failed at approximately the same number of cycles as the aircraft that crashed. The Comet was a great aircraft, the first commercial jet passenger aircraft. It it would have had round windows, DeHaviland would probably be the worlds leader in jet aircraft today, not Boeing.


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John

"And by the way, Mr. Speaker, The Second Amendment is not for killing ducks and leaving Huey and Dewey and Louie without an aunt and uncle. It is for hunting politicians like (in) Grozney and in 1776, when they take your independence away".
Robert K. Dornen, U.S. Congressman. 1995