Question about temperature, alloy and possible contamination

[Ultravox]

Let me start by stating that I'm fairly new to casting. I have read a lot about it, here and other places.

I have purchase some smelted WW lead from eBay, and some smelted range lead from someone on this forum.

I'm using a Lee Pro VI 20 lb bottom pour pot.

I have cast and shot a small pile of bullets so far and thought I was having some great success. They seemed to cast pretty well and ran through my pistols nicely with no leading.

So what's the problem?

I did not have a thermometer, so I just ran the pot at a temperature that gave me filled out boolits with a nice frosting. The pencil test shows that they are around 12 BHN or so.

Then I built a PID temperature controller and started using it. I set it for 650 and waited for it to heat up. Once it reached 650 I fluxed the melt and got all kinds of dross out of it. A large pile of "cottage cheese" was on top, so I scooped it out.

Then the bottom pour would not work. So I hit the nozzle with a torch and it started running. But the bullets were coming out all wrinkled and had lots of weird banding.

I thought the mold was too cold, so I heated it by dipping it in the pot. No go.

So I bumped up the temperature to 725. It was better, but still not as good as before.

So I plugged the pot into the wall and turned the knob to 7 (which is what I was using before) to see what temperature I was using before.

850 degrees.

So I set the PID to 850 and started casting. The boolits look just like they did before I built the PID...

So, after that long winded intro, here are my questions:

1. Is 850 too hot? Or should I just run what works? Reading some other threads it seems like I should be able to cast much closer to 700 degrees - or lower.

2. Is it possible that my lead is contaminated, or the wrong mix? How do I tell?

Thanks for any help you can give a newbie.

[Stick_man]

You might try adding just a little bit of tin to your alloy and setting the temp to 700*. When I first start casting with my 20lb Lee, I have to heat the alloy up to over 700* just to get the pour spout cleared so it will pour. My 50/50 COWW/SOWW alloy would work well in my MP mold only if my casting temp was up over 775* or so. I added a little bit of solder to the mix and now the mold casts pretty boolits at 700*.

Not saying this will work for you, but it did for me. 650* might not be hot enough for your alloy.

[Iron Mike Golf]

Adding tin to your alloy lowers the melting temp (like throwing salt on ice). You want to run 100* or so above your alloy's lquidus (everything fully melted and liquid. no slush).

Keep in mind, the temp in your spout may be less than in the alloy. It depends on the layout of the heater coil. And that spout is sitting below the pot and out in the air. That's why you want to be well above the melting point.

Really hot adds too much heat to your mold and it will make you slow down your casting cadence.

[Ultravox]

Okay, stupid question, where is a good place to source tin and what should one expect to pay for it?

I see people selling 60/40 and 50/50 solder bars. Is that the best source?

[500MAG]

I use the same pot and have had this issue before. It has helped to make sure that when I flux, I stir all the way down to the bottom. Also, it helps me to have the pour spout right up to the opening of the mold. Believe it or not, a little distance can cool it while it is going in the mold.

[geargnasher]

You don't need tin for fillout.

A clean alloy will cast good boolits if it's five degrees above the mush phase provided the mould is hot enough.

Alloy temperature has nothing to do with frosted boolits, that's ENTIRELY a function of mould block temperature.

Tin is destroyed above 750 F. Don't go there if you add tin or have any in the alloy.

100 degrees above the end of the mush phase (full liquidus point) is ideal most of the time for casting.

If you have clumpy stuff in your melt at 650 F, it's probably calcium contamination. This can be dangerous. Calcium is a common contaminant in some WW alloy, it's used to harden it and is cheaper than antimony. Calcium is likely present due to recycled battery lead being purchased by WW manufacturers, or added on purpose. Calcium makes an intermetallic bond with antimony, creating the clumps at "in-between" temperatures. Remove calcium from the molten alloy with copious quantities of sawdust and lots of stirring, and when cooled, dispose of the ash as far away from humans as possible, as it will release phosgene gas when it gets wet or absorbs moisture from the atmosphere. Minute quantities of this gas are deadly.

If you can't get good boolits from clean alloy at 100 over full-liquidus, you need to get your mould hotter. Cast at a rate of four complete cycles per minute for 25 pours and make a generous sprue puddle to get the mould hot enough. You can slack the pace slightly once it's making good boolits, but you need to monitor how the boolits look and keep the pace adjusted for the best results.

Gear

[mold maker]

Between now and the end of lead WWs, we're going to see some strange things in our smelting and pouring pots. As lead is phased out at the mfg end, what ever is on hand will be used. Since there is no reason to stick to a standard except, that it hold fast to the rim, and weigh approximately what is noted on it, the mfg, doesn't care.
They were always supposed to be disposable ,after the first use. Neither the local tire guy, nor we casters, were ever figured into the equation, for a secondary use. Thats why we got them for free.
Nothing last forever and the end of the FREE LEAD trail is just ahead.

[sqlbullet]

Gear gave you really good advice, so read his post carefully.

I will add a little to reinforce his statements.

I have helped several guys start casting. They all have the same tendency. First, they rush and don't heat the mold well before they start casting. Second, they tend to look at their newly minted boolits with an empty, open mold, losing what little heat they did have.

Gear's last paragraph addresses this. Pre-heat the mold, then cast a bunch of rejects fast. The idea is to get the mold to temp. If you waste time looking see if they look bad, they will always look bad. Like a watched pot never boils, a watched boolit never casts good.

Hope this helps.

[shadowcaster]

Gear gave excellent advice. Also to dispell any doubt about if your PID is working properly, test your alloy temperature with a lead thermometer. I keep several on hand for both smelting and casting.

Shad