Whoa - what happened here?

[44Blam]

I was casting some boolits today and I had something happen that made me just dump the pot (into ingots) and stop.

I had already cast about 10lb and my alloy is 5:1 COWW to linotype and my casting temp is around 675.

I added in another ~10 lb with the same ratio and after I fluxed it in I started seeing some strange results.

On every cast the boolits were very frosty and the sprue just crumbled when opening the plate. The lead in the pot looked fine. It was shiny and consistent so I went and cast a few rounds and all the boolits came out the same. So, I thought that I might have some sort of contamination so I thought I have enough boolits, I'll just get this stuff out of the pot and ask the folks at Cast Boolits if it looks as if I got some zinc in there or maybe just too hard of an alloy?

In this pic, on the left is an ingot of my COWW lead then next to it an ingot of some 4:1 COWW to lino from a while back (oxidized a little) and then the next two are what I just dumped out of my pot. They are much whiter and not smooth/shiny.



Is this Zinc contamination or is it that maybe the COWW lead I got was much harder than I thought?

[Rcmaveric]

I intentionally add zinc to my lead. Doesnt cause that. Sounds like your mold was too hot and/or you didnt let the sprue cool long enough.

Sounds like your alloy isnt balanced like most of use. Makes your alloy have phases. If your mold gets to hot makes it have like a "Magic Sand" like phase that last. If the mold is cooler it will transition through its phases faster and you wouldn't notice it.

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[Minerat]

Last time I got extreme frosting with a grainy finish and crumbling sprues I had the mould tooooo hoooottt. I had it on a hot plated while the pot was heating. It was even causing the HPs to break out a side when dumping the casts. I'd guess you had the same problem.

[RickinTN]

yep, most likely a mold that's too hot. With as much antimony as you have in the mix you would have to let the sprue cool much longer to get a good smooth cut.

[kevin c]

I had the same results with 95-3-2 alloy. This was in my pre PID controlled pot set for 720 degrees when full. The problem showed up with a more than half empty pot still on the same thermostat setting as full and after I had paused in the session and left the mold on a hot plate. The casts looked like silver glitter covered BBs and the sprue crumbled when dumped.

[44Blam]

Hmm. I had just added more alloy so my mold was on a hot plate. But I keep the hot plate between low and medium.

I'll just remelt a few lbs of the same alloy and try again in the next couple days.

Good thing is that it got me to finally clean out that pot.

[poppy42]

I was gonna say ya got your mold way to hot and when you opened it your spruce wasn’t completely solidified. But so many others posted the same I figured why bother. Oh wait I just did!

[John McCorkle]

I intentionally add zinc to my lead. Doesnt cause that. Sounds like your mold was too hot and/or you didnt let the sprue cool long enough.

Sounds like your alloy isnt balanced like most of use. Makes your alloy have phases. If your mold gets to hot makes it have like a "Magic Sand" like phase that last. If the mold is cooler it will transition through its phases faster and you wouldn't notice it.

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Il bite...why do you add zinc intentionally?

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[tomme boy]

To harden the lead

[Valornor]

I thought zinc really screwed with how the lead fills out the mold.


Check out my website www.theballisticassistant.com

[BK7saum]

I think over a couple of percent zinc turns to oatmeal. a small percentage alloys. higher percentages do not alloy into your lead and clump. Again least that's how I understand it.

[rintinglen]

Even small amounts of Zinc adversely affect lead alloy casting characteristics. In amounts of less than 2 % it raises the temp required to get good fill out, but is still useable. Over that, it makes boat anchors. I avoid it like the plague.

[JonB_in_Glencoe]

Il bite...why do you add zinc intentionally?

I did a test
https://www.artfulbullet.com/index.p...let-alloy.589/
read from OP down to post #15 for results.

Bottom line is, 1% zinc will only add about 1 Bhn of hardness, and that 1% is still pretty cast-able, BUT is still somewhat troublesome in the pot forming a little bit of oatmeal. Also, that extra 1 Bhn of hardness, may be a false hardness...meaning you can read it with measuring equipment, but might not help with the pressure happening in a rifle's chamber or with "skidding" in the Rifling.

[blackthorn]

If you suspect Zinc in your alloy, place a couple of drops of Muriatic acid on the surface. If it bubbles, you have Zinc!

[John McCorkle]

If you suspect Zinc in your alloy, place a couple of drops of Muriatic acid on the surface. If it bubbles, you have Zinc!

Is there a good way to remove zinc if you test positive for zinc in alloy?

I've always cast junk plinkers out of them but not sure what to do with any alloy that is zinc laiden...

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[Rcmaveric]

Around .12% zinc it doesnt cause any noticeable effect to casting. The goal is increased toughness. At .24% ita a PITA. I guess my own added bit spice to be different.

I had hunch and idea about dislocation hardening. Can't prove anything without a microscope and a PHD. But it sounded good in my head.

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[Springfield]

Rcmaveric: is that .12% of yours mean 12/100 of a percent or 12 %?

[Rcmaveric]

Rcmaveric: is that .12% of yours mean 12/100 of a percent or 12 %?

I mean .12% or .0012 or 12/10000

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[Walter Laich]

If you suspect Zinc in your alloy, place a couple of drops of Muriatic acid on the surface. If it bubbles, you have Zinc!

don't do this with a pot of hot melted alloy

[44Blam]

I've been busy and haven't gotten a chance to really poke around and try to identify my issue. But, I did have frosty boolits and crumbly sprue, etc but I didn't do anything I don't normally do and I don't tend to over heat molds. Now the thing I took a picture of were the ingots I dumped out of the pot. I dumped them in to a room temp LEE tray so you would think that you would get at least one or two shiny ingots. But all of the ingots I made when dumping the pot were frosty and almost white.
I did do some research on what a pot that has zinc in it looks like and I don't think that is it. The surface of my melt was silvery and fluid. So, no lump/chunk would indicate that I didn't have a zinc problem. I will stop by the pool supply store soon and get a little tester kit to rule out the zinc, though.

What I think may have happened is that my alloy was much harder than what I anticipated and that my melt was hotter than what my thermometer was indicating. When I get a chance, I'll do a hardness test of one of the ingots and see what it looks like. And maybe I'll melt a couple down and see if they cast...