I have quenched cast bullets in water, but I have not known about quenching them in a brine solution until now.

quote:

but this waiting period is unnecessary if the slugs or balls are quenched suddenly in the water or in the ice-cold brine. (A solution of common salt and water, made for brining of the meat or fish. The brine is concentrated enough, when an uncooked potato floats on it). This is an old trick known by the bullet casters a century ago, but no more found from the cast bullet handbooks, written by some Engineers Graduate. Hardening of the steel is based on that same process

*source*

Anyone here familiar with this technique? Can anyone explain why an ice-cold brine solution would be better than water?

I would venture to guess that it is because the salt water freezes at a lower temp

Room temperature tap water works just fine. No special tricks are required, just antimony and a trace amount of arsenic.

Brine is sometimes used for quenching water-hardening steel, but not very often. If I remember correctly, the reason is that brine doesn't bubble (boil) as much when the hot steel piece is immersed compared to plain water. The bubbles reduce the heat transfer. There's little or no bubbling when you quench a hot bullet because they aren't that hot and they aren't that big.

As my 4th grade teacher admonished, "believe none of what you hear and only half of what you see."

Thanks, it makes sense now.

I suppose that the old timers got the idea for using an ice cold brine solution for quenching bullets from their local blacksmith shops.

I've always wanted to try ice/brine quenching bullets out of curiosity, but have never found regular tap water quenching to be lacking. I'd also be a bit leary about having my bullets infused with salt, and then driving that salt through my bores.

Brine quenching was only used for low carbon steels by blacksmiths, ie steels that wouldn't harden in a normal water or oil quench. Brine quenching can be quite violent to a quality high carbon steel and cause warpage or craking of the piece being quenched.

Utter BOL**KS!

The only important thing in quenching bullets is the speed of the drop in temperature from the liquidus / solidus phase to the totally solid phase. That is from about 620 - 750f to below 600f; these are only rough approximations btw. The act of the bullet falling through the water will mitigate against any effect the formation of steam bubbles may have; which is why when water quenching steel we swirl the part around in the water.

Final temperature is irrelevant, although keeping the bullets too cold will slow down the precipitation hardening process.

quote:

Originally posted by andrew375:
Utter BOL**KS!

The only important thing in quenching bullets is the speed of the drop in temperature from the liquidus / solidus phase to the totally solid phase. That is from about 620 - 750f to below 600f; these are only rough approximations btw. The act of the bullet falling through the water will mitigate against any effect the formation of steam bubbles may have; which is why when water quenching steel we swirl the part around in the water.

Final temperature is irrelevant, although keeping the bullets too cold will slow down the precipitation hardening process.

That brings up a couple of interesting (to me) questions:

1. Would quenching be of any use at all when using genuine eutectic alloys, and

2. If it is, why?

I ask those questions because a pure eutectic, such as "pure", non-degraded linotype, doesn't HAVE a lag time between pure liquidus and pure solidus phases. In fact, by definition as I understand it (which can always be wrong, of course) by definition a eutectic alloy is one that has no mushy or in-between state. It is pure solid until it reaches a particular temp, then it is pure liquid...and vice versa. Matter of fact, that is how metallurgists test an alloy to see if it is lino...lino apparently makes that sort of transition at a particular temp in the 565-degree area.

IF, and that's a big IF, that's correct, how would quenching help lino harden, or would it? If it would, what else is in play?

Even with an alloy that is approximately a eutectic, what solidifies from the melt is still a "solid solution" containing ingredients like antimony that aren't stable in "solid solution" at room temperature. They separate out as crystals as the solid slowly cools. The hard antimony crystals are surrounded by a lead matrix (with whatever else is alloyed in it), and that can "flow" around the crystals under deforming stress. If it's suddenly quenched, the antimony atoms don't have time to migrate through the matrix and agglomerate into large crystals. They form far more numerous, smaller crystals that more effectively disrupt the "flow" of the softer lead matrix around them.

quote:

Originally posted by Ricochet:
Even with an alloy that is approximately a eutectic, what solidifies from the melt is still a "solid solution" containing ingredients like antimony that aren't stable in "solid solution" at room temperature. They separate out as crystals as the solid slowly cools. The hard antimony crystals are surrounded by a lead matrix (with whatever else is alloyed in it), and that can "flow" around the crystals under deforming stress. If it's suddenly quenched, the antimony atoms don't have time to migrate through the matrix and agglomerate into large crystals. They form far more numerous, smaller crystals that more effectively disrupt the "flow" of the softer lead matrix around them.

That's useful information, though I am a bit confused by the term "approximately a eutectic". That sounds like "approximately pregnant" in a way.

I would presume that the less an alloy meets the exact "prescription" for beng a eutectic, the more what you are describing occurs. That's often obviously the case with linotype in the printing industry which has been used enough to "oxidize out" some of the alloying tin/antimony.

Does it still occur to any meaningful degree with alloy which IS a eutectic? (I.e., what "lab quality" linotype would be, if any such existed.)

I think it still happens with a perfectly eutectic alloy. Antimony's not miscible with lead at room temperature. It's got to separate out, one way or another. I've got to hem and haw around a bit, acknowledge that I don't know how linotype quench hardens, whether that significantly increases its hardness, and refer you to the best article I know of on heat treating lead alloys: http://www.key-to-metals.com/Article88.htm At their "Contact Us" link, you can likely find a real metallurgist who can fill you in on it in great detail.