Lid my lead for less oxidation?

[jandbn]

I am in the process of building a PID controlled bottom pour pot with some band heaters from evilBay and stainless schedule 10 pipe. While mulling things over about material and design, I couldn’t decide on a pot diameter. I wanted a small diameter so there would be less surface area of the alloy being oxidized while exposed to air. Then another thought dawned on me that it sure would also be nice not to deal with more oxidized alloy after the alloy was fluxed; my thought was that regardless of the diameter of the pot, maybe I could use a metal (stainless?) “lid” to lay directly on top of the alloy so that contact between “lid” and alloy would force air out and away from most of the surface of the alloy.

There obviously would be some exposure of the alloy to the air as the “lid” could not be a snug fit in the pot and the valve rod would need to go through a slot in the “lid”. Even with the edge of the alloy around the perimeter of the pot and the slot area for the valve rod exposed, the remaining surface area exposed to air would be drastically reduced.

Other than wasting heat warming the “lid” up to alloy temp, can anybody think of a reason or reasons not to reduce air exposure with a “lid”? Is there enough surface tension in lead or lead allow to cause the surface to convex enough that an 1/8 inch flat thick plate would not be heavy enough to squash the convex surface of the lead or lead alloy so that there would not be any air in between?

[lwknight]

I think most people here would just say to use a layer if kitty litter on the melt. Personally I don't worry about it. It only oxidizes a thin layer and stops. I will usually flux it when I'm done and the pot is cooling.

[geargnasher]

You could use about a 1/4" layer of sawdust, it does the same thing.

If you want to follow through with your idea completely, flux, reduce, and skim per your normal routine, then add the lid and purge the air with a can of "canned air" for cleaning keyboards. Make sure it's 100% CO2, no flammable propellants.

Gear

[cbrick]

When I'm bottom pouring I leave a layer of sawdust ash on top of the melt. When I ladle cast I remove the sawdust ash but I'm stirring the melt with each dip of the ladle, plus I don't cast hot enough to get excess oxidation.

I've never used a lid but as a SWAG I would think at the least it should help with oxidation especially if you have a fan or other air current blowing on the melt. The sawdust ash or the kitty litter would probably work better.

Rick

[blikseme300]

When I built my smelters I thought about doing a lid of some kind but discarded the idea as I do like to return the cut sprues immediately after cutting. Also, considering that unless you are able to create an oxygen-less environment, then this approach won't have much benefit.

What I ended up doing is to leave the top open but periodically to drop a lubed boolit into the mix. This does a fine quicky flux on the top surface and mixes in as I drop in more cut sprues.

Are you going to insulate your smelter? My experience has been that the efficiency of the unit is substantially better if it is wrapped in kaowool and has a metallic shield.

Here you can see how I did mine: http://bliksemseplek.com/boolits.html

Building stuff is addictive.;)

Bliksem

[462]

For the last couple months, I've been covering the pot with a piece of aluminum foil. While it doesn't completely eliminate oxidation, it has substantially reduced it.

[prs]

Kitty Litter (actually I use clay based "oil dry" for sweeping garage floors) seems to provide me with a consistent alloy in flux from full to empty and I also can continue with some of my evil, yet convenient, habits. I drop spru waste directly back on top of the rather thick layer of clay granules and have had no splashing or souch risk of being burned. I can even add ingots right through it as I finally replenish the pot adn again no risk of splash or splatter out of he pot even if they are cool and normally damp as stored at room temp (better to pre-heat them anyway on edge of pot). Seems to work great and with minimal fuss, although maybe I am trapping tin oxide in the clay and tossing it in trash at end of sessions -- I dunno about that.

prs

[leadman]

If you use canned air as gear suggests follow thru with his advice on co2. Some are HFC134a, same as the refrigerant in most automobiles.

[jandbn]

All,

I was hoping I would be able to avoid putting anything on the top of the alloy such as sawdust or kitty litter if the lid was laid directly on top of the alloy. My assumption (assuming as bit me more than once!) was that if air can't get to the surface of alloy, I wouldn't get much oxidation other than a minimal amount from where air contacted the alloy around the edge of the lid and the slot for the valve rod. Regardless of what my assumptions are, I respect everybody’s opinion here so I thought I should ask. And I surely do appreciate all the responses.

CB has been my home for the past couple years. I wouldn't have dreamed of pouring my own 25 years ago when I thought a J-word at max velocity in a rifle was “king” and a 44 Mag revolver with factory ammo was less than impressive. After some major schooling here on CB, I became a proud owner of a Ruger Bisley 45.



bliksem,

As the son and grandson of a mechanic, I love tinkering (as long as it has nothing to do with a vehicle-had enough of that when I was younger). I have already built one double PID (pot for pouring and mold heater), a single PID (convection oven for heat treating) and I have a couple more PID units left over which will go towards a lube machine base heater and another smelting pot when I can afford to do so.

And yes, my pot design does will have a reflective barrier around the pot/band heaters, a 2" layer of Kaowool, and another barrier surrounding the Kaowool so that the wool will stay vertical. I looked at your design prior to even starting the build of the two PID units I have already finished.

I got so involved "tinkering" with the PID's, FWFL for pan lubing, lapping the bore, smelting WW along with other various lead I’ve collected into ingots, smelting pewter, and other gun related stuff that the last thing I still need to ladle pour my own is a mold! (I actually had ordered a 45-270-SAA mold, but I didn't find out until after ordering it that it was out of stock and used the $ elsewhere for the family.) As an FYI, my wife frequently complains that I tinker too much and also calls me a mad scientist when she sees all the stuff I tinker with.

As much as I like to tinker I don’t have much to tinker with at the moment. I’m getting very impatient waiting to use all the stuff I’ve been tinkering with over the past couple years. The only obstacle at the moment seems to be more $. The benefit to having a lack of funds every now and then has allowed me to spend additional time here on CB and learn even more than I already have. My “college education” here should allow me to cast my own with few if any problems. But with my luck, or lack there of, there is always Murphy’s Law…

[lwknight]

With that much insulation you probably could turn off the power and cast for hours before it gets too cool. LOL

[jandbn]

lwknight,

I didn't think 1" would suffice and the Kaowool I want to use is 1" thick so I just planned on doubling the thickness.