Water dropped cast lead vs annealing brass with a water drop.

[greenjoytj]

I read that dropping a cast lead bullet hot out of the mold into cold water will increase the hardness of the bullet.
How these this work?
I heat a brass cartridge case neck and drop it into cold water anneal the brass.
I though a sudden cold quench to harden metal was only for ferrous metal.

[Rcmaveric]

For lead:
It has to do with the alloy and crystaline structure of the solid. Lead at room temperature is close enough to its melt temp that the crystals continue to change as it sits on a shelf. When antimony is present, and the alloy is molten it is well mixed. So when you pour a bullet then water drop it. It freezes the antimony i nice long even chains. Think of antimony as rebar and lead as concrete but on a microscopic scale. Arsenic act as catalyst to help with water quench. Not sure how the arsenic works, but it is not needed as the arsenic is just for an instant affect. With out it it will just have to age harden. Selenium, arsenic and sulfur will all have the same catalyst affect. Anything we add to the lead is just to modify or enhance its crystaline structure and fill in voids at the microscopic scale. Water quench only works if antimony is in the lead.

When you create an alloy, its more like a solution. At the molecular level its like a lattice matrix with filled voids. Different ellemnts act and react differently.

Brass is copper and zinc. It work hardens because its compacting the crystaline structure. Smaller tighter structures are harder. Heating it just returns the structure to its natural state.

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[upnorthwis]

The only thing water quenching does for brass is make it easier to handle.

[Larry Gibson]

The only thing water quenching does for brass is make it easier to handle.

This is correct; water quenching the case after annealing has nothing to do with hardening or softening the case......it just cools it so it can be handled.

When water quenching cast bullets out of the mould it must be done correctly for maximum and consistent bullet to bullet hardness. Because the alloy is cooling very fast the sprue must be cut just as soon as it hardens. Too soon and you smear lead alloy on the mould and sprue plate.....too late and the bullets have cooled too much for maximum hardening. Just watch the sprue harden and cut when it turns mottled grey. Immediately knock the bullets out into the water. Some water may splash onto the mould but, not to worry, as it will sizzle and sputter off immediately. Adjust you casting tempo so the mould does not get too hot and the bullets frost.

I WQ my #2 alloy bullets and the BHN increases (after 48 hours) from 14 - 16 to 22 - 24. Linotype, with it's higher antimony content, will WQ harden to 28 - 30+ depending on bullet and how quick it gets from the mould to the water.

[Willbird]

On brass cases however the quench could make sure that the body and head of the case does not get annealed :-)....the quench is not needed for the annealing process....but it may be part of selective annealing :-)