Thin steel pot for smelting 500lbs at once?

[Oreo]

I have a bunch of misc. range scrap ingots that I'd like to melt into a single 500lb batch for the sake of consistent alloy. The cheapest pots of such volume are at Walmart. They are stainless steel but the steel is pretty thin and 500lbs is a lot of weight. I'm thinking the pot would probably do it but what do you guys think? Any engineers here who can tell me how thick a stainless pot wall has to be for enough strength?

[carbine]

I am not an engineer. Lead melts at 6-700 degrees. steel is good for approx. 2,000.

500 Lbs of lead could be as small as 1.5 feet cubed about 3.3 cu ft Sounds laike a big lobster pot IF it and your burner can take 500 lbs.
Go easy

[dilly]

All I can say is if you're worried about it, don't do it. A pot failure would be not only very costly but also very dangerous. 500lbs of lead can hold enough heat to start a pretty mean fire. This is an area where one should err on the safe side. If you'll be melting 500 lbs at a time often it's worth getting an expensive but very solid pot, and if you're not it's not a big deal to do a few different batches with a smaller, less expensive but still very solid pot.

I wish I were an engineer with the appropriate calculations to give you more useful information.

[rodsvet]

I must be reading the post wrong. Even if you could get 500 pounds melted in one batch, how would you pour or handle it? I must need more sleep. Rod

[D Crockett]

Oreo I do not have a pot that will do 500 but I do have one that will do around 200 or I can make you one that will hold around 250 but that is a lot of lead that your burner will have to hold if you have a turkey fryer from Wal-marts I would have the out side frame of it reinforced with angle iron. in this game you have to think SAFETY SAFETY SAFETY give me a pm if I can help you D Crockett

[FLYCUTTER]

Get yourself a old Freon drum and cut the top off. A 30# on a gas turkey fryer works great but the 50# are even better. And as D. Crocket says, beef up the stand with angle iron because who needs a accident.

[Oreo]

The stand, burner, and fire hazard are not an issue. I just don't want the pot to let loose while I'm standing next to it. This would be a one-time thing so I don't want to spend too much money or effort on it. If it won't work I won't do it.

In my mind the engineering is not so different then calculating water pressure vs. pipe strength. But as was said, 500lb of molten lead is nothing to trifle with. I must be certain or I don't do it. If someone here is familiar with these types of calculations that would help me a lot.

[lightman]

I don't know if I would trust a thin steel pot holding 500# or not. My pot will hold 400# and is around 3/8 in thick. If you are young and may do this for several more years, I would suggest having a heavy duty pot built. Also consider the strength of your burner stand. Enough on safety, the others have already covered that.

If I were to start over, I would find a large propane tank (maybe 250 gallon) or an old air compressor tank, cut it off and weld legs on it. Think heavy and strong!

Good Luck with your decision. Show us what you decide to do.

[country gent]

Another thing to consider is doing smaller batches and ID ingots to batch number then add the same number from each batch to your casting pot to maintain consistency. Run 5 batches of 100 lbs 2 1lb ingots from batch 12345 equals 10 lbs in the casting pot and will work to have the same alloy everytime

[RogerDat]

You can rest the pot on bricks to take the weight off of the turkey fryer and IF YOU PRE-HEAT and use a sawed off 20# propane tank which will hold over 100# at a shot. You can get a pretty consistent batch by refilling with more material when the pot gets down to 1/2 full. Have to pre-heat the material to be added in order to make sure it is totally dry, piece of range scrap taking water below the melt will give you a dangerous visit from the tinsel fairy. Use a shovel with a long handle to add material, face shield, gloves etc.

If you really want consistency in an easier and safer manner use the 20# propane tank to do large ingots (say bread loaf pan sized) from each batch and keep ingots from each batch separate, label as A,B,C, etc. once cooled. Probably do 500# in 4 or at the most 5 batches with propane tank pot with no need to risk adding material to a half full pot. To make a pot of finished bullet material take one ingot from each batch and melt together. If every batch of material you cast from has an ingot from each pot then your casting material will be consistent.

Assuming 10# ingots 5 of those (1 from each batch) should fit fine in a Dutch oven on a regular turkey fryer to be re-poured into usable sized ingots of completely blended material as needed. Or as a separate operation if you wanted to process the whole 500# and be done with it. Same process as country gent described but bigger ingots. (we were both working on our post at the same time)

I think D Crockette sells those pots ready made at a reasonable price, thread on his equipment in swapping and selling people seemed pleased with his product. Give him a PM. If nothing else instead of buying a disposable and possibly unsafe Chinese made pot from wal-mart you would have a re-usable propane tank pot with a market value if you decided to sell it later.

[Mike W1]

A pot built from a propane tank would be cheap to make. They're about 12" diameter and you can figure the part where the sides are straight at about 46 lbs to the inch. Need good support system and a heat system to match. Doable though.

[theperfessor]

The height of the column of molten lead makes a big difference in the amount of stress placed on the walls of the pot. The pressure against the walls of a vessel at any point is the fluid density multiplied by the height. A tall, skinny pot filled with a tall column of lead will have a higher wall stress than a short, wide pot with a shorter column of lead. Once the maximum pressure is calculated you need to use that to calculate the hoop stress that is trying to cause the walls to fail (under tension). Remember that even stainless steel loses a lot of strength at elevated temperatures, and becomes more ductile (stretches and deforms easier).

None of these calculations is difficult to do, but you have to know your pot size and so forth to solve.

My gut feeling is that if things like this make me nervous I DON'T DO THEM. I would work with smaller batches, a thicker vessel, etc.

[rickys2]

come on man a 500lb ingot of lead. How do you plan on remelting it?

[jsizemore]

Fella at the scrapyard picked up a 55gal steel drum with a forklift pinching the sides of the drum with the forks. He set it on the scale to check weight. 1800lbs. Picked it up and loaded it in my truck. Other then the collapse of the sides, the bottom was not affected. I use 55gal drums for ingot storage but fully support the bottom. Mine were free but they sell for scrap steel price in my area.

[bangerjim]

Do smaller batches!!!!! I would never attempt over 100# at a time. No matter what the pot is made of.

I never mix huge batches of alloy because someday I will probably want to change it and I am stuck with it. I mix my alloys in my casting pot from the basic materials to get me to the mix I want using the alloy calc spreadsheet. Works ever time for me!

banger-j

[RogerDat]

In this case the OP has a 500# pile of one alloy source, range scrap and wants to get it consistent across the whole 500# so when casting it the batches don't vary in hardness based on what type of bullet was in that particular small batch pot. The typical problem of mixing big batch of alloy and later finding out you wish you still had some of the ingredients separate for a different use probably does not apply.

All I can think of is really big batch, impractical to my way of thinking and possibly unsafe. Or smaller batches segregated then blended with equal amounts from each smaller batch. More work but safer and should yield good consistency. It is all range scrap so I doubt there would be a huge variation between any two 100# batchs but one never knows. Could find a few BHN between the hardest and the softest 100# pot. Second smelting with some from each batch should deal with that.

[Oreo]

come on man a 500lb ingot of lead. How do you plan on remelting it?I feel like it should be obvious that my plan is to ladle the whole batch back into small ingots once blended. What would anyone ever do with a single 500lb chunk of lead?

I have some different alloys that I will keep segregated. I have quite a bit of reclaimed No.2 shot and likely more coming. That will remain segregated because I know what it is and it's different enough from anything else I have. I have a batch of high tin content, solder of some kind. I don't have anything with higher antimony content. I'll have to purchase some if I ever need it. And then there's all this range scrap I mined myself from several different berms and smelted in several batches that I never kept track of. Its all different enough to warrant blending but not different enough to warrant sorting and segregating. It's pretty good base alloy for most shooting I do that I can use the other stuff to adjust as needed.

Melting and remelting a bunch of different 100lb batches is too much work and time. I just need to find a suitable pot or not do it.

[2ridgebacks]

Has anyone tried to melt this much? I have a very large (700lb by my figuring) pot and a 250k burner. A lid is obvious for heat retention, but it has also been suggested to firebrick around the pot to insulate. Anyone with ant experience?

[Newboy]

I have done maybe 750 pounds before. I only had a 30 gallon steel drum, and used that. No problem. They look like the 55 gallon drums, just smaller. I was concerned about the seams and thin metal, but it worked fine. Ended up with nice homogenous ingots.

[Animal]

I had tooled around once with an r134a drum that I was wanting to use. I put a tourch to it on a low heat setting to get it warm enough to make a nice cut. The steel was so thin that it started cutting during the warming process. I don't know if that drum was a particularly thin drum, but it sure seemed flimsy. Not what I expected at all. I wouldn't smelt water in that old drum. I'm sure there are some better ones because they seem like a popular option for smelting. I just wasn't feeling too good about how it started to fall apart so quickly on a low heat setting. Be cautious about the quality of some refrigerant drums.

[birddog]

I have converted a 6gal paint pot to my smelting pot, but also cut it down to hold about 3.5gal. That is all I would care to work with at one time
Charlie

[Oreo]

Running the calculations right now. Looks like a 16" diameter pot, 8" depth of molten lead is not quite 660lbs. At 8" depth lead exerts something like 3psi, if I've calculated correctly. Still working on it...

[jsizemore]

Has anyone tried to melt this much? I have a very large (700lb by my figuring) pot and a 250k burner. A lid is obvious for heat retention, but it has also been suggested to firebrick around the pot to insulate. Anyone with ant experience?

You can use sheetmetal too. I use the sheetmetal jacket from an old hot water heater cuz it was free. I use the bottom or top for a lid. The holes in the lid let me stick my thermometer stem into the melt so I can monitor temp.

[40-82 hiker]

Do smaller batches!!!!! I would never attempt over 100# at a time. No matter what the pot is made of.

I never mix huge batches of alloy because someday I will probably want to change it and I am stuck with it. I mix my alloys in my casting pot from the basic materials to get me to the mix I want using the alloy calc spreadsheet. Works ever time for me!

banger-j

Bangerjim has a lot of wisdom here, along with others.

I can't add much, but am responding to say that you must ask yourself why you need to take such a risk for no added benefit. I too smelt to clean the lead and make ingots, and then make my alloy in my casting pot, which can be done with great consistency (never had any problems with it). A sturdy $50 dollar burner stand with a HP burner, and a 20 pound propane tank properly modified is really all that is needed at largest, IMHO. It's too simple, really. I mean this with great respect, but it appears your making this unsafe by making it too complicated, unnecessarily so. I think this site has hundreds of members and guests who safely smelt lead in the 100 to 200 pound range safely all the time. Think you're out there on a limb with 500 pounds...

[lightman]

I can do about 400# with my set-up. The steel pot and the stand are plenty strong enough for that weight. I like the consistency that I get with the larger volume. I've never felt in danger using my rig. Blending batches smaller than this is plenty good for what we are doing, so mine is probably overkill. Its just what I had at the time.

Oreo, if you were close to me I would go partners with you on this project. I probably either have what we would need or can get it. Good Luck with this project.

[dikman]

I have a 1/2 propane tank that holds about 150 lbs crammed to the gills. I wouldn't consider any more than that, myself, in the interests of safety. If you want to go heavier I would use a pot made of thicker metal.
Don't forget that you're actually heating the bottom of the tank itself too. While it's all very well to say that it's only at the temp. of molten lead, during the heating process you're pouring a lot of heat onto the bottom of the tank and while you won't get it hot enough to melt if you put enough heat on it then it could very well soften a bit. This could apply in particular to a pot with a thin base. Not a good idea if you've got a couple of hundred lbs. of molten lead sitting on top.

As has been said, if in any doubt don't try it.

[theperfessor]

I made up a spreadsheet using several simplifying assumptions that calculates the tensile stress in the walls of a thin wall (t = .032") pot. The equations used are as follows:

Density of lead, constant, 0.4097 (lb/in^3)
Weight of lead, constant, 500 (lbs)
Wall thickness, constant, assumed to be .032 (in)
Volume of lead, calculated, = Weight/Density (in^3)
Diameter of pot, incremented constant, 1 to 16 in .5 increments (in)
Height of lead, calculated, = (Volume x 4)/(pi x Diameter^2) (in)
Pressure at base of pot wall, calculated, = Density x Height (lb/in^2)
Hoop (tensile) stress at base of pot wall, calculated, = Diameter x Pressure/wall thickness (lb/in^2)

What you make of this information is up to you.

133983

[40-82 hiker]

Perfessor,

Thanks for the chart, but how would we calculate the failure point of mild steel at a given temp. based on the hoop stress of your chart? Obviously the strength decreases with temp., but how is that decrease calculated? Also, steel does not transmit heat as efficiently as aluminum (am not advocating the use of Al for smelting - just example), so is it possible to say that the burner side of the steel vessel (using a HP propane regulator) is hotter than the 675 degree inside surface regulated by the lead absorbing the heat? This would weaken the vessel even further than appearance due to lead temp., would it not? SS is an even worse conductor of heat, so the difference there would be even greater.

Thanks.

[badbob454]

my worry is a thin metal pot will get cherry or white hot where the lead is not touching it , over a very hot burner ,
go with a good heavy pot, and support your weight on the burner

[theperfessor]

I don't know of any fundamental way to calculate the strength of a given material at elevated temperatures. If there is an equation to do this it would be a derived equation, i.e. a best-fit curve that would use numerous data points taken from tensile tests across a range of temperatures. There is data for the tensile strength of various materials at elevated temperatures in some engineering handbooks.

The typical design process is to calculate the stress in a certain spot and then multiply that by a safety factor to determine the minimum material strength needed. Most safety factors range from 2 to 10 or more. A safety factor of 2 might be used when sizing a component that wouldn't hurt anyone if it failed, where a safety factor of 10 might be used when there might be a loss of human life involved. If I recall hydraulic hoses use a safety factor of 6 or 8, not sure what sf is applied to elevator cables but I think you get the idea.

Actual stress x safety factor =< material yield strength

If I were doing this I would look up the tensile strength of my material at some point above my melt temp just to be safe. Let's say you find out mild steel (or stainless or whatever) has a tensile strength of 15,000 psi at 900F. Using a safety factor of 10 (melted lead scares me) I would have to be sure the actual stress doesn't exceed 1/10th of 15,000 psi, in other words I would not stress the material above 1,500 psi.

I could change the wall thickness, melt less than 500 lbs, or use a larger diameter pot.

Won't tell anybody else what to do, but I have a propane powered rig that melts 80 lbs or so at a time and once it is fired up and cooking I stay as busy as I ever want to be keeping up with the loading, casting, ingot handling, etc. I personally would probably find 500 lbs at once a little overwhelming.

[40-82 hiker]

I don't know of any fundamental way to calculate the strength of a given material at elevated temperatures. If there is an equation to do this it would be a derived equation, i.e. a best-fit curve that would use numerous data points taken from tensile tests across a range of temperatures. There is data for the tensile strength of various materials at elevated temperatures in some engineering handbooks.

The typical design process is to calculate the stress in a certain spot and then multiply that by a safety factor to determine the minimum material strength needed. Most safety factors range from 2 to 10 or more. A safety factor of 2 might be used when sizing a component that wouldn't hurt anyone if it failed, where a safety factor of 10 might be used when there might be a loss of human life involved. If I recall hydraulic hoses use a safety factor of 6 or 8, not sure what sf is applied to elevator cables but I think you get the idea.

Actual stress x safety factor =< material yield strength

If I were doing this I would look up the tensile strength of my material at some point above my melt temp just to be safe. Let's say you find out mild steel (or stainless or whatever) has a tensile strength of 15,000 psi at 900F. Using a safety factor of 10 (melted lead scares me) I would have to be sure the actual stress doesn't exceed 1/10th of 15,000 psi, in other words I would not stress the material above 1,500 psi.

I could change the wall thickness, melt less than 500 lbs, or use a larger diameter pot.

Won't tell anybody else what to do, but I have a propane powered rig that melts 80 lbs or so at a time and once it is fired up and cooking I stay as busy as I ever want to be keeping up with the loading, casting, ingot handling, etc. I personally would probably find 500 lbs at once a little overwhelming.

Thanks for the post. I was just wondering if there was any way to work this backwards when you posted your chart. I still think it best to use what works safely for so many people, but was hoping there was a quantitative way to determine the stress capable with a given vessel.