Two questions about heat treating

[Elkins45]

1) Does it do any good to heat treat pure linotype? I am fortunate to have squirreled away some printer's type from a newspaper where I worked 25 years ago. I use it exclusively to cast rifle boolits, so it has lasted a long time. Does it make any difference to try to HT an alloy that's already about as good as it can be?

2) What is the proper technique for hot-quenching directly from the mold? Should I drop the boolits onto a soft cloth, pick them up and quench them, or do I lose too much heat that way? Should I open the mold directly over the bucket of water for an immediate quench?

TIA for any info.

[HeavyMetal]

Drop directly into a bucket of water!

Not sure how much of a gain in hardness your gonna get using Lino but I bet you'll bump from around 25BHN or so to the mid to high 30 on the BHN scale.

I always set my water drop bucket at 90 degrees or so from the pot with me between the two. This means I must turn to my left open and dump the mold then turn back to cast again.

This has successfully kept me from spalshing water into the pot for over 40 years

[wiljen]

1) Does it do any good to heat treat pure linotype? I am fortunate to have squirreled away some printer's type from a newspaper where I worked 25 years ago. I use it exclusively to cast rifle boolits, so it has lasted a long time. Does it make any difference to try to HT an alloy that's already about as good as it can be?
If it is true linotype, it will be lacking the required grain refiner to heat treat harden.
Adding something with trace arsenic, copper, selenium, sulfur, or others will allow you to heat treat harden it.



2) What is the proper technique for hot-quenching directly from the mold? Should I drop the boolits onto a soft cloth, pick them up and quench them, or do I lose too much heat that way? Should I open the mold directly over the bucket of water for an immediate quench?


Out of the mold into the bucket. I suspend a towel so the middle is about 6 inches deep in water. This allows the bullets to drop into something soft so the bottom of the bucket doesnt ding them up.


See http://www.castpics.net/memberarticles/arsenic.htm for more on grain refiners.

[DLCTEX]

I water drop my boolits directly into a 5 gal. bucket of cold water when heat treating. I did some 475-400 boolits yesterday and only one had a small ding where another struck it during dropping through that much water. Casting with a hot mould at a fast pace and using Bullplate lube so I can cut the sprue early, the boolits sizzle when they hit the water. I cast on a tall workbench and place the bucket slightly under the bench to prevent splashes from hitting the pot. I have never cast with lino, so I don't know if WD will add any value. It may be that you could mix it with lead or WW and WD to save some lino and still get hard boolits.:castmine:

[cbrick]

You'll get minor hardening from quenching lino because of the antimony, working against you is the percentage of tin and as wiljen mentioned, lack of arsenic. The higher the tin percentage the less effect from HT.

A better question is do you really need your alloy any harder than lino? Harder IS NOT BETTER, it's merely harder and many times harder can cause it's own problems.

Rick

[runfiverun]

mixing ww's and lino 50-50 will harden in your oven to over 30 and close to 37.
you need to practice to get the heat just right with the 2% tin,and dump them quickly into the water.
if straight from the hot mold to the cool water ww's will get as hard as lino.
i too turn to the side to dump and occasionally get a splash on the mold, so be careful you don't have any in the cavities when you start pouring.

[243winxb]

Does it do any good to heat treat pure linotype? No, linotype will do all you need to do with rifles or pistols.
What is the proper technique for hot-quenching directly from the mold? I feel oven heat treating is the only way to go. When boolits are dropped directly from the mould, they do not all hit the water at the same temperature. Heat treating is best with alloy using 2% to 6% antimony and very little tin, maybe .5% IMO

[sqlbullet]

Linotype is 'satisfied' eutectic alloy, and for this reason will not heat treat.

When you heat treat a lead/antimony compound, you freeze the metal lattice quickly enough to limit atom migration and clumping. Tin does the same by trapping the antimony atoms in the lattice even when they cool slowly.

Linotype is a 'satisfied' alloy in that the ratios of lead/antimony/tin provide maximum solubility with no excess of any component. As a result, the lattice forms the same whether quenched or air cooled, yielding the same hardness.

However, not all linotype is true linotype. Frequently what we see has been tin depleted through repeated casting during it's life in the print industry. This linotype, if tested, would not meet the ratios of a satisfied alloy, and will therefore heat treat.

The correct course of action for any wondering about their alloy is to try it and see, assuming you can justify the need for a projectile harder than air cooled.

[felix]

Excellent! ... felix