Contaminated alloy?

[ChestnutLouie]

I did a short casting session using ingots that I buy from a guy who melts them down from WW. I've bought a bunch from him but today one or more of them were wrong. Even at 700 degrees it was very slushy??? I thought that zinc is the most common contaminant and that it melts at about 787 degrees. After lots of skimming and stirring in some sawdust with more skimming it looked sort of OK . My Lee 4-20 pot was about 2/3 full and I began to cast. When the pot got down to 1/3 full alloy was coming out of the spout in a weak stream and bullets started looking like the picture so I stopped casting and dumped the pot. That will be discarded. I re melted the bullets that looked ok added some more ww ingots and an oz of tin and the new melt looked and casted fine.

What do you suppose messed up my first batch? seemed to be slush floating on top.

Thanks
Francis

 

[462]

. . . one or more of them were wrong.

Zinc contamination, and all of the remaining ingots may be as contaminated.

 

[farmboy]

First off do you use a lead thermometer? Are you really sure the pot was 700? Discarding that whole pot could cost you $$$. There are ways to salvage that lead...maybe. By using copper sulfate and re-melting that whole batch. Skim off the sludge and stir...wait several minutes and use more copper sulfate, wait until it turns from blue to gray/white. This should remove most of the zinc. What zinc that is left will combine with the copper and actually make your alloy stronger and more malleable. I'm just waiting for " POPPER" to jump in as I think he is the expert.

 

[farmboy]

Copper sulfate can be found at farm & garden stores. It is used for killing weeds in farm ponds and as a tree and stump killer. I bought some last year at a Farm Bureau for about $2 a pound

 

[ChestnutLouie]

Yes I have a thermometer, why would I say that the melt was700 degrees?

Zinc does not melt at 700? Unless there is a zinc alloy that will?

 

[Dusty Bannister]

Zinc and even antimony will dissolve into the lead solution at 700 degrees. That is one reason that most who melt and clean lead alloys keep the temp well below the melting temp of zinc. Also the temperature for zinc at 787 is pure zinc, and not a lead zinc alloy. I suggest you do the acid test on the remaining ingots before you get too excited. The weak stream might just be a bit of debris building up in the nozzle area. Often just applying a little heat to the nozzle will allow the debris to release and normal flow will return. The heating element is in the middle of the casting furnace so at 1/3 full, the element is above the alloy and might be part of the reason the alloy is sluggish. Another factor is low alloy levels do tend to not flow as quickly as those in a full casting furnace. If the probe of a PID or thermometer is resting against the side or bottom of the casting furnace, you are reading the crucible and not the alloy.

 

[Michael]

I had a batch of WW that I melted down once and obviously missed some Zn weights, Silver slush is right, amazing how little Zn it takes.
Next time out I grabbed my ladel, a slug mold, and turned up the heat, figured no lube grooves to worry about, and 3"-4" at 50yds will get the job done.

 

[Ian]

Zinc does not melt at 700? Unless there is a zinc alloy that will?

Like Dusty pointed out, Zink alloys all melt way below 787, same as lead-alloy WW melt at about 570-590 which is lower than the melt point of pure lead. WW are something like ZAMAK #3 which is zink, aluminum, and magnesium if I remember right. Zink WW melt at about the temperature of pure lead.

 

[fiver]

garden sulpher will clean it better than copper sulphate.
the copper stuff will only change out maybe 1% of the zinc for copper.
which is a good thing, if you think 3% zinc causes problems wait till you see what a 3% copper alloy acts like.

just throw some good known alloy in the mix with the bad stuff, when you get to about 1% or so [1.6% is the max solubility,,, before [shrug] you'll never even notice it's there unless your BHN testing.

 

[Dusty Bannister]

No real problem until the drop of acid reacts with the lead alloy to show it is a problem.

 

[ChestnutLouie]

Thanks!

but it was only 6 lbs or so that I paid $1 per lb so its in the trash

 

[johnnyjr]

Interesting post,about the WW's.
I cast up close to 15 lbs to make 243 bullets. These came out of the mold to large. I'm no expert,but I'm thinking to much antimony. They were about 12/14 with my lee hardness test. What's up with that. Roto metal from now on
Probably Lyman num.2...

 

[popper]

Yup, Sulphur will take out the excess zinc and stink real bad. And it toughens the alloy. And stinks real bad! Just add known good alloy to reduce zinc %. Or save it to add to the next non-zinc batch. Low zinc % isn't really bad.
Johnny -- pushing small bore bullets fast needs tougher alloy. #2 is probably good for 243. I get superhard (pellets) from Roto to add for Sb, cheaper way to go. Don't use any tin but I only cast for 30 cal. Their high Sb varies too much, 3-5%. Some have reverted to using high temp header paint to reduce nose size.

 

[Tomme boy]

How hard are the bullets you cast? Zinc will make them a lot harder. Don't throw it away! Its not that big of a deal like people make it out to be. I think you just have a clogged nozzle from using the saw dust to flux. Both of my pots will start to flow really slow when i get them low. Thats when I know I need to empty them and clean them out.