Weird Sprues

[Mr. S]

Hello,

After getting back in to casting over a year ago, my casting had been going well. I was happy with my results. Things were good. Then about six or seven months ago, I ran out of the commercial Lyman #2 that I had been using for most of my boolits when I got back into casting. That commercial supplier was out of #2 so I ordered some #2 alloy from a different commercial supplier.

For the last few months now, when using the new #2 alloy, I am getting what looks to me like sparkly sprues. They also seem very brittle. Now at first when this happened, I was also using a couple of new molds I had bought. The first problem I had noticed was in fillout with the new molds. One was brass and the other was aluminum.

At that time I kept cranking up the heat on my RCBS furnace. It was near to maxed out before I got good fillout. I also tried to speed up my casting. I had cleaned the molds like I usually do, hot water mixed with Dawn then let dry, hose down with brake cleaner and then denatured alcohol. This has always worked.

At first back then when I saw the sparkly sprues, I thought it was from running the heat so high, but dropping the temp gave me the fillout problems again. I contacted the retailer I got the second #2 alloy from and they had me send some of the sprues to them. After a month or so I called them back and was told the alloy was within their specifications for Lyman #2 with just a slightly higher amount of tin.

Well, I just stopped casting for a few months since I just could not get the results I had before. Now I guess it was in November this year, or maybe a little longer I decided to try again with an inexpensive Lee .38 wadcutter mold I had bought on sale.

I put the Lyman #2 ingots in my pot, added a pinch of flake flux, turned the pot on and let it heat up. After the ingots were melted and the flux was like charcoal, I used a wooden paint stirring stick to work the flux through the pot and waited for any crud to rise to the top. What little came up I skimmed off. I had the temp set with an RCBS thermometer to around 725 degrees. I would say during this casting session the temp was between that 725 degrees to maybe 750 degrees.

Once the mold heated up, the boolits were not too bad. I did struggle with fillout again at first. However, I am still getting the weird sprues. When I swing over the sprue plate, I can feel it doesn't cut, it feels more like the sprue is breaking off. Occasionally, when the sprue drops on the towel on my bench it will actually break in half.

I guess I am doing something wrong, I just don't know what it is. My routine is the same as I did when I started casting again slightly over a year ago, and had some pretty good results.

There may not be enough info in this post. It is early here and we have had a lot of late nights with family in for Christmas. I meant to do this post a month ago and other things got in the way. I am going to include some pictures of the sprues in question. Any thoughts would be appreciated.

Thanks

Rick

http://i404.photobucket.com/albums/pp130/Rickkster707/Weird%20Sprues/Sprues1.jpg

http://i404.photobucket.com/albums/pp130/Rickkster707/Weird%20Sprues/Sprues2.jpg

http://i404.photobucket.com/albums/pp130/Rickkster707/Weird%20Sprues/Sprues3.jpg

http://i404.photobucket.com/albums/pp130/Rickkster707/Weird%20Sprues/Sprues4.jpg

[Nazgul]

Looks like zinc contamination.

Don

[Wayne Smith]

I'm guessing too much antimony, but that's just a guess. Much more qualified people than I will respond. From what I've heard zinc will be much worse.

[lwknight]

I guess stranger things are happening somewhere but thats not zinc. Zinc contamination will make oatmeal dross quickly everytime you melt it and the spru will be smooth with swirls in it. Also the zinc will be very soft when its first cast and then harden to brittle within a few days.

Mr S , I would suggest a new supplier. There is something out of whack with that stuff.

[old turtle]

I had zinc in some alloy years ago and it did not look like that, but who knows. I was wondering if the content of lead is low and the tin and/or antimony is too high. I am not an expert and I agree with Wayne that someone on this site will have good information.

[docone31]

That is not zinc.
You got a **** blend.
If you add some Roof lead to the mix, it will straighten out. You might write to the people who got you the #2 and show them the photo.
It looks like Antimony grains. Sounds like a dense mix.

[Uncle R.]

I've seen scrap type metal that casts like that - I'm guessing it has a very high antimony level and little or no tin. If that metal was mine I'd experiment by mixing one batch (maybe ten lbs) 50/50 with soft lead to lower the antimony - even if I had to buy hardware store pig lead to get the soft stuff. I'd sweeten the test mix with 3% tin - even if I had to buy solder to get a verified tin content. It wouldn't take a lot of cash invested to make up only ten lbs and you might find the new mix casts very nicely.
Uncle R.

[sqlbullet]

That looks to me like high antimony lead. Here is my guess.

You are used to Lyman #2 which has a tin content of 5%, antimony of 5% and the balance being lead. It had a hardness of BHN 15 and a relatively low melting point due to it's high tin content.

The new batch of #2 alloy you received is similar in hardness, but achieves this with much less tin and much more antimony in order to reduce costs. It also has a much higher melting point than proper #2 alloy.

Those sprues look to me like the results I get with very hot lead. My alloy is 96% lead, 3% antimony and 1% tin and I cast between 700° and 725° pot temp. If my alloy is much over 750° my sprues start to have that exact appearance. Even at this temp though, I will get poor fill out if my mold is not fully up to temp.

Chances are since your experience is with much higher tin content lead, you have been running with your molds a little on the cool side. High tin content is very forgiving of this. Dial you pot back to about 700°, and then pour 10 pours as fast as you can, cutting the sprues as soon as they won't smear. Don't worry about tearing them. I would bet your fill out issues go away.

Then you will just need to adjust your tempo so your molds stay up to this new temp level.

[NHlever]

The break in the sprues, and the way they cut off sounds like too much antimony to me too. If it were too much tin, you sure wouldn't have fillout problems, but antimony will give you that. Antimony really doesn't alloy with tin, and gives you a "composite" material, as you can see clearly in the photos. The boolits, and sprue will also be brittle because of the grains of antimony being "in the mix" but not actually blended. In a normal alloy, the antimony bonds with the tin in the mix, and the tin actually alloys with the lead. The way to find out closer is to obtain the specific gravity of your alloy. There was a thread titled "weight of solder alloy" here a year, or two ago that explains how to check the specific gravity. You can also Google "specific gravity". Have you weighed the boolits, and are they lighter, or heavier than the mold specs? It sounds to me like you have some linotype with the tin depleted out of it, or something close. I have some mystery alloy too. My boolits came out VERY shiny, well filled out, and 10%, or more lighter than they should have. My sprues were also very brittle. After trying this, and that I finally did the specific gravity test, and it checks out to be 50/50 lead, and tin. I'm still not positive that is what I have, but I have been using it that way, and everything comes out right for it to be that.. boolit weight, fillout, etc. Good luck with your mystery.

[runfiverun]

it looks like too much tin to me.
the tin content is much higher than the antimonial content.

when you form a sbsn chain and have excess tin it tends to hang onto the chain till the last second then attempts to alloy with the lead ,it can't do it in time and you end up with tin spots surrounded by soft lead.
what you have looks like a classic case of that in the extreme.

the supplier told you what was wrong with the alloy, they just didn't stand behind their product.

[lwknight]

This might help
Specific Gravity chart (http://castboolits.gunloads.com/attachment.php?attachmentid=18225&d=1261865841)


http://castboolits.gunloads.com/showthread.php?t=71012

[Mr. S]

Thank you for the replies everyone. I haven't worked since May, but I think I am going to try and pick up some pure lead and mix up a 10 pound test batch maybe 50/50 with the Lyman #2 I have and see how that works.

I probably won't be able to do that until next week or so. I have tried speeding up my casting routine. It did help with fillout, but didn't seem to help the weird sprues. I also have some 1-20 & 1-30 that I had bought for some Webley boolits. Any thoughts on using some of that with the #2? Of course, if it is too much tin, I guess that may not be much good to use.

When I first contacted the supplier, they did sort of offer to make some adjustment. I didn't take them up on that because I thought I was just doing something wrong, and I really couldn't pin down what they were willing to do. After they tested the sprues I sent to them, it seemed like that offer was off the table.

Since I have like four boxes of this #2, I would like to find some way of using it. The fastest I currently push any boolits is 1100 fps in my .45 Colt. I do also load for our .357's and would like to be able to get 1200 fps out of boolits for them. Other than that, most of the shooting we do is with target loads at 800 - 850 fsp, except for the Webley at 620 fps or so.

Thanks again everyone! I will keep you updated when I try adding some lead and maybe I can pick up a bar of tin at some point as someone suggested. There is no getting wheelweights around here, they are all spoken for or I would have just used that instead of the #2 in the beginning.

Thanks,

Rick

[runfiverun]

i would test some small batches.
but if it were mine i would mix it with some linotype 50-50 about 1lb each and see if the funny sprues go away.