Rapid Cooling of CastBoolits or CastBalls

[bugoutbicyclist]

Does rapid cooling of CastBoolits increase the hardness of the Boolit? What liquid and at what temperature would you use? I'm casting .501 Boolits in multiple weights.

[tazman]

Yes, provided you have a suitable alloy. Others can give you specifics on alloy composition, or you might look in the lead and lead alloys forum.
For a cooling liquid, I use cold tap water and drop from the mold into the water.
I am casting for pistol so I don't require the consistency or hardness a rifle would. Others use different techniques to be more consistent. Heating in ovens and very cold antifreeze solutions are a couple of the techniques as I remember.

[Big Boomer]

All I have ever done is water drop directly from the cast boolit mould. Some go to the trouble of standing their boolits in or on a firm metal pan in an oven and heating them to about 400 degrees Fahrenheit for about an hour, quickly removing them and dumping them into a container of water. Some think ice water works best. Both these methods work (water drop directly from boolit mould and oven heated and dropped in to water) but it is critical that the cast boolit/ball have a sufficient percentage of antimony along with the lead alloy and a certain percentage of arsenic for best hardening results. Some more knowledgeable members will chime in. Big Boomer

[bangerjim]

If you are going to mess around with trying to gain hardness thru water dropping, Sb is your friend.

I do not do it. I mix my alloys for the air cooled hardnesses I desire. But I have over 400# of a 20% Sb rich alloy.

But I have played around with it. COWW's air cooled will be around 12. Water dropping them will gain 6-10 over time. I have that 20% Sb alloy and if water dropped, it ends up over 40! Waaaay to hard for any boolits!

I now only cast 9-12 hardness and then PC.....not worrying about old school hardness gain from water quenching. 14 for sonic loads.

Most just drop directly from the mold. 400F is not really hot enough to get desired hardnesses. Again depends on your alloy.

bangerjim

[Motor]

I use a lead / linotype alloy and water quench for convenience mostly. I measure the hardness right after quenching. How long does it take for the boolits to stabilize hardness wise after doing it this way?

I've never re-checked one after sitting. Never had any problems with them either.

Motor

[RobS]

As been said antimony is needed for water quench hardening. If you are a hunter then this property is a potential desired trait in that a person can make a boolit hard yet ductile and not shatter on impact of a hard object like a bone etc. Also for those who need a harder boolit and do not want to deal with mixing alloys. And for those who powder coat, heat treating can be a bit tricky too as baking the boolits will anneal the boolits back down to a softer BHN. Although I've read that people are taking their oven cooked powder coated/Hi-Tec coated boolits and quenching them from the oven although..........

I know I can water quench or heat treat a non coated boolit to whatever hardness is permitted with the alloy I'm working with and then even anneal them down to whatever BHN I like should I choose. I do see the appeal to the coated boolit though but I'm just not sold on it's application with all my different reloading realms.

There are reasons for a end result and there are different ways to make and end result positively accurate.

[DrCaveman]

Yes, usually. If you have a wheelweight/linotype/lyman #2 alloy, then yes.

If you are using an elmer keith 20:1 lead:tin alloy then NO.

I use tap water, a 2 gallon bucket full. Maybe ice water would work even better, but i havent felt it neccessary to try

[NuJudge]

What makes the Lead harder is things that make the deformation mechanism more difficult. Just Tin does not make it much more difficult, dissolving in the Lead, and distorting the crystal lattice of the Lead by, here and there, a Tin atom substituting into the Face Centered Cubic structure for a Lead atom. The Tin atoms are a slightly different size, and distort the structure just a little.

When you add Tin and Antimony, you get fine precipitates of a Lead-Tin-Antimony compound all over. These precipitates grow really quickly perhaps before freezing, definitely during freezing, and while the Lead is frozen but still hot. If you can get the bullet cold really quick, you should have a lot more fine precipitates, and this does a lot better job resisting the deformation mechanism.

My experience in the Met Lab was that cold water does not do a much more rapid quench than warm water. Brine (salt water) does do a significantly faster quench, but who wants salt anywhere near something that's going to go down your barrel? The salt inhibits bubble formation on the hot part being quenched, resulting in greater and more rapid heat transfer.

[Wayne Smith]

NuJudge, isn't there something else that interfers with the bubble formation? Something in the back of my mind tells me that I have read that somewhere, or was that with quenching steel?

[jonp]

I asked a similar question a while ago and tried varying the water temp from icewater to hot tap water. I could not tell a difference beyond a normal variance. I use a lee tester so its probably not as accurate as most others.

[Yodogsandman]

Check this article out...

http://www.lasc.us/HeatTreat.htm