The Leaded Bore From Hell, Part III

MAD DOG,

You know a whole lot more than me about hardened steels and heat-treating, but here's some hypothetical grist for your mill.

The fact the fouling from hell is ferromagnetic got me thinking. Consider how it may have formed:

1. smear out a thin layer of iron (abrasion from iron/steel bullet traveling down the bore)
2. dust with fine carbon particles (from unburned powder)
3. heat under high pressure (by shooting another round)
4. quench (the very thin fouling layer "shell" has large surface area contact with the barrel, which acts as an effective heat sink, causing the fouling layer to cool relatively fast)
5. repeat

This sounds like a recipe for high-carbon steel with a heat-treat method that would produce a hardened steel - like building up thin layers of case-hardened steel. No wonder you are wearing out stainless brushes.
 
Edmund Rowe and Gopher,

Barrels start out as bar stock. If not stainless, most are AISI 4140 or something close to it. They are routinely blued by the hot tank process, so I doubt hot water will hurt them any. BTW, I hope the aircraft parts that won't stand up to hot water are not things like jet engine turbines.

Jim


[This message has been edited by Jim Keenan (edited March 15, 2000).]
 
Jim Keenan:

I hope I made this clear, but maybe I did not:

The problem isn't the hot water by itself. The problem is the cleaning agent/detergent that was tested at room temp to pass a mil-spec for cleaning steel. The late breaking info is that if the water temp is heated then a LOT more detergent chemical reaction goes on, not all of it good for the metal. How hot is too hot is not well understood right now. At room temp the effect doesn't show up.

Hydrogen embrittlement is a very squirrely phenomena. It might take 5 years to develop a catastrophic failure in landing gear steel, or one good landing and it goes CRACK-O!!! At the microscopic level, hydrogen works it's way inside the steel creating tiny fissures that become larger over time.

Hope that helps.

Edmund
 
A post wash bake of 450F for 4-6 hours will alleviate the hydrogen problem, as it forces the H out of the steel.
This is a common thing to do after most plating processes, etching, and other hydrogen intensive chem processing of steel.

It can be done at lower temperatures, but it takes longer.
 
Maddog-

I believe the bore is fouled with paint or lacquer. "Old time" gunsmiths used this method to prevent the bore from rusting during rust bluing. I used this method during the construction of my Springfield Express rifle. No rust in the bore, but removing the stuff afterward was a real bitch...

If you're stuck, try paint remover.
 
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