I know that lead has a melting point. Tin has a melting point. And the mixture of lead and tin has a LOWER melting point (or range) than either of the two individually. In fact, it does not take a whole lot of tin to lower the melting point quite a bit.

I have not been able to find out what antimony does to the melting point. It has a melting point that is about twice as high as lead and nearly three times as high as tin. Does it raise or lower the melting point of whatever mixture it is put into?

I am also wondering about the same thing with zinc, but not as much. I have added quite a bit of lead and tin to zinc and don't seem to have made much of a dent in the melting point.

Any ideas on where to find this information? Also, I am sure the reduction in melting point (below the melting point of either of the metals that make it up) has a technical name, but I have not found it. Does anyone know what it is? If I knew that, I probably would have more success looking it up.

I believe the term you are looking for is eutectic, ie lead tin is an eutectic alloy.

Don't know what antimony does to the melting point.

You will find phase diagrams that will list the melting temperature for the whole range of percentages of two metals alloyed together, such as lead and tin. The eutectic mixture is the that which has the lowest melting point of all the ratios.

Phase diagrams get complicated with more than two elements in the mixture, so you won't see many.

In the "Cast Bullets" book by the NRA, Ed by Harrison, there is an article by Dennis Marshall, that everyone uses as the reference for lead, lead tin, lead antimony, lead tin antimony alloys.
There are phase diagrams for all the alloys at all concentrations and temperatures.
This is the article to read for reference. - Lew

Harry the melting point of a mixture will always be lower than the average of its components and often lower than any of its components. How much depends on the physical interaction of the different components. It will also vary to some extent with the heating rate If you are trying to measure these I would sugest that you record the freezing points instead of the melting points. To do this heat the mixture until completely fluid and then remove the heat observe the tempature as it drops. at the freezing point it will stay level or start back up a few degrees. This will give you a point instead of a range.
Langes' Handbook or a handbook of chemistry and physics will have the freeze points (they may be listed a melting points) of many common alloys.

I have heard about the NRA book from several people (all recommend it) and have checked the NRA website to try and buy a copy. No luck. Does anyone have a URL to where I could buy it?

Remember, these text book folks are using lab grade metals for showing their characteristic curves for the various alloys they cook up. Impurities slip into home made material from junk yards, and the curves from the books might not be even close to what would be expected for the guesstimated alloy in the pot. ... felix

HarryO: The NRA book is long out-of-print; even AbeBooks (my ultimate resource) doesn't currently show a copy. But Dennis Marshall has an excellent article on the lead/tin/antimony alloys in Lyman's 3rd Edition "Cast Bullet Handbook", pp. 43 - 52,a nd I think that is the article most people refer to. Nothing on zinc, though - but lead and zinc are basically incompatible for our purposes anyway. floodgate

HarryO

The Lead-Zinc Phase diagram is shown on page 45 of Lyman Cast Bullet Handbook above mentioned . They are not soluble under conditions we deal with. Diagram is completely different. The low temperature point for melting, or solidifying, are two and correspond to very very low percentages of lead or zinc.
Segregation of Zinc Lead melt is shown on page 41, figure 1 of the same book.

BA Shooter

I am sorry.Lead Zinc phase diagram is on page 46 and photo is on page 44, Lyman Cast Bullet Handbook, Third Edition

BA Shooter

HarryO: Our Argentine friend is right (thanks, BA!), and I was off-base; the lead/zinc data are also in the same article - it's been some time since I read it through, and I had forgotten. From the diagram, you can "float" the zinc off the mix down to about 1-2% Zn, but can't easily get rid of the rest, and that's enough to louse up your casting. I don't know how adding tin would affect the result; that's 'way out of my league. floodgate

Tanks for reminding me about the Lyman book. I had forgotten the lead/zinc diagram there.