Does lead require more heat than WWs?

[crabo]

I have a new mold from BABore that he suggests I cast pure lead at 725-750 degrees. This is the first time I've used pure lead for something other than lap boolits.

When I run my RCBS wide open with wheel weights it will get 825 or so. Wide open with pure lead and it stays in the 725-750 range. This is not a problem, in fact it is what I want.

SO, does it take more heat to heat lead to the same tempeture as WWs?

Inquiring minds want to know.

[chboats]

You have an interesting problem. I do know that to cast pure lead you have to cast at much higher temp than aloyed lead. But I would not think that the pot could not bring it to the same temp.

Carl

[KYCaster]

I'm certainly no expert, but that sounds kinda odd to me.

I can understand a difference in the TIME it takes to reach a particular temp, but logic tells me the max temp should be the same.

The difference could be from the radiation heat loss from the surface which could be affected by ambient temp or the thickness of the oxide layer.

It would be interesting to see if a layer of kitty litter on top of the melt would reduce the discrepancy. [smilie=f:

Jerry (If you can't dazzle 'em with brilliance, baffle 'em with BS! :roll:)

[Dannix]

It would be interesting to see if a layer of kitty litter on top of the melt would reduce the discrepancy. [smilie=f:
I was just thinking that perhaps a thick layer of sawdust could help.

Let us know how it works out crabo. Perhaps you weren't waiting long enough? May be worth giving RCBS a ring.

[crabo]

I was building a 10/22 and I just turned the pot on and monitored it for several hours. At wide open, it stayed 725-750.

NOW.... I always have a layer of walnut shells on my WWs, but I didn't have any on this lead. I may put some on it tomorrow and try again.

[geargnasher]

Crabo, from Lyman Cast boolit handbook #3, pure Pb has a liquidus temp of about 620*, while any addition of Sn brings that point down until eutectic point of 19% which has a liquidus point of 361*. In Sb/Sn/Pb alloy, the same reduction in melt point occurs depending on concentration of Sn/Sb. If the alloy is eutectic (linotype, for example) the phase changes at 464*, and for Lyman #2 the phase changes at about 560*. So, as you experienced, pure lead has the highest melting point of our common boolit casting alloy.

The manual also suggests casting at about 100* over liquidus temp. of the alloy, and my experience concurs except for hollow point moulds. That's why Mr. Brandt made the suggestion he did for pot temp. with pure lead, it takes a lot more energy to get and keep it hot enough to cast well, and that also explains why your pot labors so much harder and still doesn't get quite as hot as with alloyed lead.

Gear

[crabo]

Thanks Gear, I figured there was a scientific reason for it.

[qajaq59]

NOW.... I always have a layer of walnut shells on my WWs, but I didn't have any on this lead. I may put some on it tomorrow and try again. The insulation of the walnut shelss should help a little. But, I've never noticed it was harder to maintain the temp on the softer lead over the harder. And I do cast both pretty regularly.