please help me identify lead alloy

[bigborefan]

I recently bought some lead from a metal salvage yard and one large ingot (about 7 lbs) is so hard that using the ball bearing method to measure BHN doesn't even mark the ingot the ingot at all using 200 lbs of pressure. The ingot is lighter than what the same size would have been in lead. Also when I tried to melt it down with a coleman gas stove, I couldn't get it hard enough to melt. The only way to mark or dent this ingot is by hitting it with a hammer but even using that method, it doesn't mark up that easy. I doubt very much that it is babbitt. Could this be a bar of Antimony? Bar is 12"X3"1.5" and says NLCO KIRK from the mould on it. Anyone to venture a guess as to what alloy this is?

[whisler]

NLCO could be National Lead Co. but I have no idea what KIRK stands for. Could be the name of their plant or ? Try Google or National Lead's Website if they have one. If you don't find National Lead, try NL Industries (their newer name I think).

[grumpy one]

The observations seem to be consistent with it being kirksite, which is zinc with about 4% aluminium and is used for casting temporary press tooling. It is quite a commonplace material. You might be able to verify that your ingot is kirksite by checking with the company that produced it. Needless to say, zinc is not a useful additive to lead for casting purposes.

[NVcurmudgeon]

bigborefan, from the light weight, high melting temperature, and "Kirk" you may have an ingot of a ZINC, or a ZINC alloy. I have seen 1950s American rifleman magazines that had articles about casting bullets of "Kirksite" alloy. IIRC, Kirksite bullets weighed not much more than half the weight of a bullet cast of lead in the same mould. Also IIRC, the article said that using a mould, dipper, or pot with Kirksite ruined it for any normal lead alloy casting. Guess during WWII some casters would use anything that melted!

[bigborefan]

Thank you gentlemen for your input. That sounds like what this is. I'm glad that I couldn't melt it down now. Sounds like I saved me from some grief later down the line. That's the only thing bad about buying from a salvage yard. You don't know what's alloyed with what you get. I've also picked out bars of what I believe is lead with lots of copper and tin in them. I didn't smelt those down yet. Sounds like a perfect zinc paper weight now.

[bigborefan]

I just googled about kirksite and the problem with it being kirksite is that it has a very low melting temperature (396 degrees to be exact) and my guess of the coleman stoves temperature was at least 850-950 degrees without showing any start of melting.

[ANeat]

Here is the info I found

Ultimate Tensile Strength 35,000 psi
Elongation in 2" 2.0%
Impact Strength 6 ft-lbs
Melting Range 717-745°F
Density 0.25 lb/cu in
Brinell Hardness 100
Solidification Shrinkage 0.14"/ft


They also mentioned that the casting temp was 800 to 850

[grumpy one]

bigborefan, it sounds as if you have the melting point in degrees Celcius, which translates as 745 degrees Fahrenheit.

[bigborefan]

Grumpy one, You are right. I went back to the website that I got the information from and it was celcius. I was going by the statement that it had a low melting point and never paid attention of the large C. My bad. Thanks for pointing this out. I guess that there's a good chance that it is kirksite. The 100 BHN sure fits.