Smelting 101

[kbstenberg]

Well my first smelting is completed. I only have a couple questions.
1 When i fluxed an stirred i got a dark substance on the top of the melt is that the impurities coming out of the lead? it wasn't much, an it was easily skimmed of. But it came back after i look about 4 ladels of lead out of the pot an put in ingot molds. I fluxed again, an skimmed again.
2 when i poured into the molds the surfaces were mirror like, an as they cooled they turned flat grey. Is that the way shey should act? I was using muffin pans. The lead i poured into a enclosed bulk mold came out shiny silver color.
Well if everything was OK on to pouring into bullets as soon as i get a mold.
1a I have a question on pre-heating molds. Should the molds be open to heat both inner faces of the mold
2a how much heat is too much for pre-heating? ya i know a !000 degrees is too much.

[243winxb]

Your alloy sounds ok, you will know more when you start casting bullets. First they must be the correct diameter needed, thats most important. As for Pre-heating> From Lyman Bullet Making Guide-
Never dip your cool mould into molten bullet metal because the rapid temperature change may cause permanent block warpage.

From Ohaus guide to better bullet making -
Never submerse the blocks into the molten alloy. The Lee can be heated by dipping in the pot.

[Dale53]

I might mention for a new caster, when it is said, "to dip your mould in the molten lead", it is meant to submerge the corner of the mould in the melt. DO NOT immerse the whole mould, whether Lee or someone else, whether iron or aluminum.

If you are using a large multi-cavity mould, it may be too large or too cumbersome to dip into the melt. Those moulds can be nicely pre-heated by placing them on a hot plate (mine works perfectly just a bit over Medium - yours may vary from mine). My hot plate has a solid sheet metal surface. If yours has a bare Calrod unit, I suggest you might want to place a piece of sheet metal over the burner. Putting a mould across a calrod unit MAY warp the mould because of differential heating. The sheet metal eliminates this possibility.

Dale53

[KYCaster]

Q #1....The dark layer is oxides. You can't stop it. It will always return. Just ignore it and pour your ingots.

When you start casting boolits you will see the same thing. If it bothers you then cover the surface of the liquid metal with a layer of cat litter. (the cheapest clay litter you can find) That will protect the metal from exposure to Oxygen. You can add fresh ingots right through the cat litter. (crushed charcoal also works)

Q #2....The hot surface of the metal oxydizes very quickly, so the surface turns dark as it cools. The ingots poured in a closed mold were protected from the air; therefore no oxydation and shiny surfaces.

Jerry

[snuffy]

As to pre-heating molds. I was just doing a little experiment with pre-heating a lee 6 cav. mold. I nearly wrecked a sprue plate when I cast too soon, thinking the mold was hot enough. Shearing 6 sprues that hardened RIGHT NOW! cracked the sprue handle! Some epoxy and elec. tape fixed it!:-D

I bought a laser thermometer from harbor freight. I use a small camp stove that sits on top of a propane bottle to pre-heat molds. But how long to leave it on the burner? I heated it until the sprue plate read 350 degrees. That of course meant the mold was hotter, BUT the laser doesn't read well on shiny surfaces. The mold itself,(down in the cavs), read only 200 D. The first cast, the sprues sheared with little effort, and the boolits were nearly all filled out!

[Wayne Smith]

Molten metal creates oxides of the metal on contact with O2. When you use a ladle you stir and drop some of the metal, exposing more of it to the O2. You just have to flux more frequently as it doesn't work well to keep Kitty Litter on the melt when ladling.

[JIMinPHX]

I might mention for a new caster, when it is said, "to dip your mould in the molten lead", it is meant to submerge the corner of the mould in the melt. DO NOT immerse the whole mould, whether Lee or someone else, whether iron or aluminum.

Dale53

Why not? I normally dip the entire bottom of my mold in the melt about 3/8"-1/2" deep for about 30 seconds before I start pouring. I've never seen any problems from doing this.

[Dale53]

I didn't tell you to not dip the bottom of your mould, I suggested that you do not IMMERSE your mould (completely put it under the molten lead - BAD IDEA).

Dale53

[JIMinPHX]

Not being argumentative, but an honest question here - why not?

[snuffy]

I don't dip ANY mold in the molten lead anymore. Why? Because some of it hangs onto the surfaces that were in the lead. It has, at times, ended up between the mold halves, causing them to create fins and oval boolits. I pre-heat using the above mentioned propane stove, mold gets hot and has no lead clinging to it.

As for the mold warping, if the front is getting hotter, while the back is still cool, dimensional differences will exist. You COULD call that warping, but it's not permanent. The mold will return to it's original dimensions once it's heated uniformly. That's all assuming the metal is stress relieved to begin with.

[kyle623]

I always just rest my mold on top of my melting pot while it heats up. it seems to work just fine, then when i ready to change molds set the new mold on it and cast till it reaches temp.

[snuffy]

I always just rest my mold on top of my melting pot while it heats up. it seems to work just fine, then when i ready to change molds set the new mold on it and cast till it reaches temp.

I used to do that too. But getting burned picking the mold up by the handles, and the handles getting scorched, stopped that! Then if I were ladle casting, having the mold on top of the pot is impossible.

[Huntducks]

Your first ??? has been address.

I heat my mould with a propane torch.:drinks:

[JSnover]

I ended up with one of those little Lee melting pots (4 lb, I think) and it's almost useless because it's so tiny. But a 1 or 2 cav mold will fit right in there for a preheat and the handles don't get cooked.

[JIMinPHX]

I don't dip ANY mold in the molten lead anymore. Why? Because some of it hangs onto the surfaces that were in the lead.

I get around that problem with a smear of high temperature grease on the outside of the blocks.