Flummoxed over fluxing

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David R. posted this 1 weeks ago

I have run in to what for me is a new problem. It seems that I have impurities in my metal that I have so far been unable to remove. In the past this has never been an issue. I add a dab of bee's wax to my wheel weights, Linotype, whatever and after it smokes off I skim the dross off of the top and start making pretty bullets. I have some fifty pound ingots that came from an old boat. A while back I melted one down using a cast iron caldron over a cajun  cooker, casting it in to smaller ingots that I can use in my Lee furnace. I was making pretty bullets with that metal as I have been accustomed to. I recently melted down another ingot and I have been unable to have the same results. I'm making pure lead or nearly pure lead bullets for my 40-65 that I will shoot with Black Powder. Even with the metal at 800 degrees F and adding some tin I still get wrinkled bullets. I have fluxed with bee's wax, paraffin and saw dust but it only gets slightly better. I ordered some flux from a vendor on ebay and today I melted down the whole mess again and attempted to flux it some more. You can see below what I presently have.  I don't see how I can get decent bullets out of this stuff. Obviously ballast doesn't need to be particularly pure to work, but I need clean metal. I readily admit that I know very little about metallurgy or the science of how all of this actually works. I just practice what I was taught thirty years ago and until now it always worked. I have skimmed a huge pile of dross off  and it just keeps coming to the surface again. Do I just need to be more patient and keep working it? 

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onondaga posted this 1 weeks ago

I don't believe your problem is related to alloy or fluxing at all. Your problem is thermodynamic and related to your casting. Wrinkling is caused by either to high a temperature  of either the mold or the alloy, not fluxing.

Establish the ideal temperature for casting your alloy, Learn  with a thermometer to record the fluidus point at the first sign of solidification while cooling from a hot melt. ,The fluidis point plus 100 F. is the ideal casting temp for 1-4 cavity molds and +125 for 6 cavity.

The ideal casting temp is also a good fluxing temp.

Temp control and a thermometer will do you a great service.

Higher by a lot over the ideal temp for your alloy causes rapid oxidation of all the metals in your alloy. The colors in your pot are typical of overheating lead to the point of rapid oxidation.

 

Gary

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David R. posted this 1 weeks ago

Thanx, I do use a thermometer in my little furnace when casting, but not in the big pot. I didn't know that too hot could cause this problem. I had only seen wrinkles when the mold wasn't warmed enough so I assumed that I needed to go hotter. Also I'm finding that pure lead needs to be hotter than I usually cast. Perhaps there is an ideal range that is narrower than I was aware. I'll give it a try. 

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RicinYakima posted this 1 weeks ago

Your picture is at close to 900 degrees F. Loose the turkey burner and get regular lead casting equipment, IMHO. What ever was in the alloy, all the tin is gone, lots of lead and even the antimony is oxidizing away.

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David R. posted this 1 weeks ago

I only use the big burner to break down large fifty pound ingots in to smaller ingots that will fit in my casting furnace. This particular metal is intended for pure lead bullets for my BPCR shooting. This is what those bullets look like. I had been advised by another shooter that my metal wasn't hot enough so I intentionally brought it up to a higher temperature. I also read that impurities would increase surface tension preventing the metal from flowing properly and causing wrinkles. I'm now thinking that I have inadvertently caused a second problem by overheating my metal. I plan to try a small quantity in my casting furnace and follow Onandaga's advise for finding the optimal temperature and see how that works. 

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admiral posted this 1 weeks ago

I have always found casting large long bullets out of pure lead to be difficult. If the mould blocks are aluminum even more so.

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RicinYakima posted this 1 weeks ago

Agree with "admiral", metal may be hot, but mould isn't. I have always had to heat/cool cycle aluminum moulds a lot with cleaning in between. Picture not only shows cool mould but also appears to have some petroleum product still in the cavities. HTH, Ric

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Eutectic posted this 1 weeks ago

 

Fluxing cannot remove contaminating metals in lead alloys. Some fluxes claim to be able to “purify” the alloy of unwanted metals. This is bogus advertising. If you have a flux which will do this, patent it and the metal industry will pay you millions to use it. Fluxing can only remove dirt and dross from the alloy. Fluxing also allows alloy entrained in the dross to be separated back into the pot.

 

 

 

Can you remove contaminating metals from the alloy? The answer is yes, but only some metals. You can remove copper, nickel, calcium and strontium. Copper and nickel as well as calcium and strontium, combine with antimony to form inter-metallic compounds with melting points higher than the lead tin antimony alloy. These form clumps which inhibit fill out.

This clumping behavior can be used to advantage. The intermetallic compounds are lighter than the lead alloy. Maintain the alloy just above the melting point. Flux it and allow it to stand quietly for 5 minutes. The inter-metallic compounds will rise to the surface, giving it a “gravel road” appearance. Do not flux, skim off the surface dross. Repeat this until the surface remains clear for 5 minutes. Now you can cast the alloy into ingots. Dispose of the dross immediately as calcium or strontium contamination will render the dross dangerous.

 

The disadvantage of this is it depletes the antimony as well as the unwanted metals. It is most effective in cleaning scrap like set type and bearing metal before they are used to harden alloys. There is some copper and nickel left in the melt, but subsequent addition of lead or alloy dilutes it so it is not a problem.

This procedure does not remove all potential contaminants, zinc, aluminum and others remain.

Zinc and aluminum increase the surface tension, inhibiting fill out causing wrinkles and rounded bands. There is nothing you can do - sell the alloy to a scrap dealer or make a boat anchor with it.

 

Steve

 

 

 

 

 

 

 

 

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onondaga posted this 1 weeks ago

David, The voids in the casting picture you posted have rounded edges on the voids and is technically called "cold short". Your mold or metal weren't hot enough to fill the mold.

Voids from overheat of the metal or mold are VERY DIFFERENT and jagged and crystalline looking.

Establishing the ideal temp for your alloy or any bullet alloy is the same and related to the fluidus point at 100 Degrees F above fluidus.The ideal temp is based on dropping bullets from the mold 3-4 times a minute from a 1 to 2 cavity mold. A slower cadence of casting speed will not keep molds warm enough and you will also have cold shorts even if your metal is the perfect 100 degrees above fluidus. Casting is a thermodynamic method balance to achieve optimal results.

 

Gary (retired casting analyst and instructor, Williams Gold Refinery)

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R. Dupraz posted this 1 weeks ago

admiral

RicinYakima

 

My experience as well, especially with aluminum molds.

 

R.

 

 

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OU812 posted this 6 days ago

I have one LBT mould that was very difficult to learn. Both bottom pour and ladle had problems much like yours. Finally I learned that increasing pouring distance helps fill mould better. Holding ladle about 1" above sprue plate and pouring or increase pouring distance when using bottom pour.

Much like in this picture.

 

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David R. posted this 6 days ago

The mold is a Lyman. It isn't aluminum. I had also already cast quite a few bullets before I took that photo. In the past, I've only seen wrinkles if the metal and / or the mold wasn't hot enough. Usually just casting a few bullets will bring it up to temp. My practice is to lie the mold across the top of my furnace and let it be warming as the metal warms up. Normally it only takes a handful of bullets at the most to get it up to temp. I'll try to find time today to have another go at it. 

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Eutectic posted this 6 days ago

David,

I stand by my previous statement since you said:

" I was making pretty bullets with that metal as I have been accustomed to. I recently melted down another ingot and I have been unable to have the same results."

You changed the alloy and things went south. Therefore the alloy is the problem. The comments on how to get good fill out are normally helpful, but if the situation is as you stated, they will not help.

I have had this problem in the past as I am a Cheap Bas@#$d and ran around the local scrap yard looking for deals.

Steve

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David R. posted this 5 days ago

To follow up: Today I fired up the "turkey burner" , but took care to turn the flame down lower. I brought the metal up to about 750º F by my Lyman thermometer. I did a little fluxing and skimmed off what dross there was, but it wasn't too bad this time. I turned off the heat and just made as many ingots as I could before the metal went stiff. I ended up with a nice little stack. . Afterwards I plugged in my Lee casting furnace and brought things up to to temp. Again I monitored temperature, keeping it as close to 750º as I could. I made about forty or so bullets. They were much nicer than my recent efforts. Evidently I just had my metal too hot. Live and learn. The furnace I'm using is a bottom pour. I experimented with lowering the mold support to give the lead more distance to fall. Initially I had gone too far as it was spewing back out of the mold and leaving voids in the bullets. I raised it back up about halfway to where it had been before and that seems to be the sweet spot. 

Thanx everyone for the input. I now have another issue with my mold, but thats for another thread. 

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R. Dupraz posted this 5 days ago

Glad to hear that your problem is solved and of it's solution. One more little detail to file away in these vintage memory banks that hopefully is retrievable. Seems to be a problem these days.

My long time general MO is to heat the alloy and mold just enough to make good bullets. works most of the time, depending.

 

R.

 

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OU812 posted this 5 days ago

Shaking the mould slightly before sprue solidifies will help also. I know it sounds like BS but it works. Sprue should not solidify too quickly for shaking to work best. More heat or faster casting speed helps sprue from solidifying too quickly. 

Along with Spout flow rate adjustment and distance poured can help with difficult moulds.

Some of my easiest moulds to cast with require very little fine tuning.

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R. Dupraz posted this 4 days ago

Seems that every mold has it's own unique personality.

 

R.

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