The Home Machinist!

The downside of a fabricated brass barrel is attaching the trunnions. You don't want to heat it excessively or you will anneal the brass to its softest state which is not desirable. While I would have no concern silver soldering trunnions to a steel barrel, I would not do so with a brass one.

GeorgeGaskill wrote:The downside of a fabricated brass barrel is attaching the trunnions. You don't want to heat it excessively or you will anneal the brass to its softest state which is not desirable. While I would have no concern silver soldering trunnions to a steel barrel, I would not do so with a brass one.

George,

I'm pretty sure that to anneal brass, it must be quenched in water. Simply heating it and allowing it to air cool should have no effect on the temper. A well known method of annealing cartridge cases for hand loading involves setting them in a pan of water, heating them up and tipping them over to quench. The barrel I'm using, with its silver soldered trunnions has been proofed at double the powder charge and as I said, it's been serving me well for around 30 years.

Here's a closeup pic of what they look like.

Tom

TGriffin wrote:I'm pretty sure that to anneal brass, it must be quenched in water. Simply heating it and allowing it to air cool should have no effect on the temper. A well known method of annealing cartridge cases for hand loading involves setting them in a pan of water, heating them up and tipping them over to quench.

I am not 100% certain, but my understanding of setting the case heads in a pan of water was to insure that the hardness of the brass was not removed from the head, when heating the neck. The quenching at the end does not effect the temper just cools enough to be able to pick them up with your fingers and not burn them.

I have seen lots of annealing with out quenching In water or having the heads set in water. Just a different way of doing it.

TGriffin wrote:[I'm pretty sure that to anneal brass, it must be quenched in water.

No, it does not. It's not the quench that anneals, but the temperature. Quenching yields a cleaner surface, I'll grant you that, but the material will be softened, even if you allow it to air cool.

A well known method of annealing cartridge cases for hand loading involves setting them in a pan of water, heating them up and tipping them over to quench.

That's a process used to control how much of the brass gets annealed. It's mandatory that the head remain work hardened, so by placing them in water and tipping as the appropriate temperature is achieved, they are annealed only where they were heated. Tipping stops the process, but does little towards the actual softening. If they are allowed to air cool, and they are heated too far down the cartridge, the head will be softened as well. The level of water is held below the shoulder, otherwise it's difficult to get the neck up to annealing temperature because of the ability of the brass to conduct heat rapidly to the water.

Harold

How about soldering the trunnions with "TIX", which melts about 275° F, and has a tensile strength of about 4500 lbs/sq.in.; or Harris "Sta-Brite", which is tin and silver, and melts around 450° F ? (I think Sta-Brite is quite a lot stronger, too, tensile around 10,000 or more lb/sq.in.).

This is lifted from the Harris web page (underlining mine):

"Both Stay-Brite and Stay-Brite 8 produce an overall component with greater strength than a brazed component whose base metals are weakened by annealment from high brazing heat. Stay-Brite solders bond with all of the ferrous and nonferrous alloys. Joints soldered with Stay-Brite solders exhibit considerably higher than nessessary elongation for sound, dissimilar metal joints and vibration applications. "

If you can keep the temperature of the barrel below 500°F, you are probably OK, but I am more or less guessing about that. I think even 500°F will start the lessening of hardness and therefore, strength.

Although you may have been successful with silver soldered trunnions, it may be because the pressure at the middle of the barrel is not enough to cause a problem with the barrel strength in a reduced state.

The whole point of temper is pretty much academic if there is adequate wall thickness on the barrel. The original barrels were cast and certainly not heat treated, but they had a heck of a lot of mass. Metallurgy was a pretty young science back then so they probably just over engineered the heck out of the barrels and then proofed them just like I did.

Tom

A point well taken, and one with which I agree. However, heat treat wasn't an option, as brass does not heat treat. Hardness is developed by cold working, which you'd find in bar stock, but not in castings.

There are copper alloys that respond to heat treat, but the process is not related to the typical carbon cycle with which we're generally familiar.
They are precipitation hardening alloys that require a prolonged soak at a prescribed temperature, which develops the desired grain growth, increasing hardness and tensile strength. Beryllium copper is one such alloy. You're most likely not going to encounter the stuff in everyday life, in particular when you consider it's quite toxic.

Some grades of aluminum, too, harden by the same process

Harold

Yet another thread which may or may not interest all here on the board, but very interesting reading. I have a piece of 304 stainless that I have considered using for a cannon barrel. I would be interested in opinions of the suitability of this metal for this purpose.

Jack.

Tough to drill, but adequate for a small cannon if you're willing to fight the drilling operation. Keep cutting speed under 75 fpm with HSS. Great elongation and respectable tensile strength.

Harold

My experience with stainless for black powder cannon barrels has been good and they seem to clean up much faster and more thoroughly than steels like 1018.

Thanks for the reply Harold and George.



Jack.

P.S. What is a good way to color stainless, if there is a good way, to brown or yellowish?