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View Full Version : New caster with no idea on melt mix.



Dogueman
10-24-2011, 02:44 PM
New caster here with no real experience. I read a ton of posts here before trying my first melt that has left me with several challenging questions.


The melt was composed of about 20 pounds of reclaimed range lead, about 10 pounds of some sort of lead roofing sheet, and about 4 pounds of some sort of solder wire. Everything was purchase from a local scrap yard. Everything was melted in a 5 quart dutch oven that was placed on a gas grill running at the 650-700 degree zone. I tried to keep the melt under 700 degrees and fluxed a few times with candle wax before pouring into muffin pans.

During the melting process I noticed the melt would solidify rather quickly and often had a grainy frosty look if the temp was not maintained above approximately 650 degrees. When I would use my slotted steel spoon to scoop dross out of my melt the lead on the spoon would clump and harden within a half second. With the lead in a molten form I was able to pour about a dozen or so muffins with varied degrees of success due to rapid solidification. Upon inspecting the cooled muffins I noticed they had a light silvery frosty color with a sponge like surface that almost had a speckled glitter look, the tops of the muffins looks okay. Pouring ingots at a temperature lower than 650-700 degrees would result in a clumpy pour.


I did a test batch casting of some fishing sinkers and noticed the melt would not fill the mold cleanly. I later increased my furnace temperature and tried to pour some boolits for practice. I noticed most boolits lacked a sharp edge with periodic voids along the surface where the lead appeared to be folding in as it poured (700 degrees pot temp.). All bullets were returned to the pot, melted, and poured out into marked ingots to isolate the batch.

One thing I noticed during the boolit casting was that as soon as the sprue lost it's shine and I went to cut it, the sprue plate was very tough to cut (hard).

My thoughts. Do I have an excessive amount of tin in my melt? What could that unknown roofing sheet I assumed was lead really be made from. Was that solder wire mixed with something other than tin? Why is the batch of lead I smelted so hard? Why won't the mix flow smoothly and give me clean sharp edges when casting?

And now for the most important question. How do I clean out my bottom pour melting pot so what's left in the pot does not contaminate future melts.

:killingpc

Trey45
10-24-2011, 02:56 PM
Welcome to the forum, firstly, thanks for giving such a precise description of your efforts thus far, it's going to make diagnosis much easier. Tin allows lead to fill in the fine details of a mold easier, I doubt having too much tin is the culprit here. My first inclination is to say your molds weren't hot enough and thus preventing fine fillout. Try again with a hot mold, dip a corner of your mold in the melt for a while, pour fast and hard at first, get that mold hot, then start taking your time, pour evenly and keep a decent cadence going, if you don't soon see better fillout, then I'd be more concerned about the alloy. Before you get too far into this, you did clean those molds out good and dry and free from oil and grit right?

As far as the composition of your raw materials, almost 100% certain the roofing lead is pure, the solder is a guess.

bumpo628
10-24-2011, 03:46 PM
With that mix, you should have an alloy with 5 to 7.5% tin depending on what kind of solder it was.

If cleaning the mold doesn't work, try increasing the temperature of the alloy. I have seen the grainy alloy you're describing before when I tried too big of a pot on a small heat source. There could be some cold spots in your pan. I got a smaller pot and the problem went away. Later, I got a bigger heat source (turkey fryer).

R.M.
10-24-2011, 05:33 PM
There's no need to stay under the 650 like you said if you're not melting raw wheel-weights. The idea there is in case there happens to be any zinc WW in the batch, they won't melt till the temp gets up to 787 degrees.
Increase your heat a bit, and let your spoon float on top of the melt for a while. This will drive off any moisture, and keep the alloy from solidifying on it.

runfiverun
10-24-2011, 07:05 PM
that much tin would allow zinc and even copper to alloy in the batch easily enough.
if you got a bunch of 2/6/92 alloy in the range scrap you got waaaay too much tin to antimony ratio.

Dogueman
10-24-2011, 09:22 PM
that much tin would allow zinc and even copper to alloy in the batch easily enough.
if you got a bunch of 2/6/92 alloy in the range scrap you got waaaay too much tin to antimony ratio.

I am new to casting. What is the effect of too much tin to antinomy causing zinc and copper to alloy into the lead?

The more I learn the more I realize how little I know about casting.

Thanks in adavance for the replies...

badbob454
10-25-2011, 02:18 AM
tin allows the zinc and copper to stay more fluid in the mix i wouldnt worry about either , the range lead ,, never heard of a problen with it , as most shoothers will not allow it in their mix ,.... sheet of roofers lead 99.9 percent lead no problem there . the solder ??? could have anything in it from antimony tin lead silver ,, not to worry yet if i had more roofing lead i would add some to the mix to soften it im thinking high antimony and tin in your mix , if heating up your molds and some more temp of the mix dosent fix the fillout then try to add roofers lead or pure lead of another source im just making an educated guess so i hope this helps you ... bob

runfiverun
10-25-2011, 06:24 PM
tin likes lead it however loves antimony.
the problem arises when you got a long chain of tin that ain't attatched to any antimony on one end.
it tears free from the antimony and tries to bind with the free lead as the boolit cools.
it can't.
it then form free spots of tin in the alloy surrounded by soft spots of pure lead.

you gotta think about a drop of food coloring in a glass of water, it goes in red but you stir it up and one drop disappears.
put in a drop of blue and you start to see some color put in two drops of blue and you cant see the red no more.
the other stuff like copper and zinc are other colors.
blended properly you get purple,do it wrong you get grey [not black] a godawful grey.