Alloy management @ 700 degrees

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Wm Cook posted this 2 weeks ago

I would appreciate some advice on how to care for alloy, specifically Linotype at 700 degrees.

As some of you may know I’ve been working toward cast accuracy with a modern bolt gun and have narrowed the process down to using single cavity brass mold’s (~198 to 214 grain) and ladle casting from a 10lb Lyman pot. My cadence is twice as long as yours but the results are worth it for me. Sprue cut, base fill out and weight deviation is good to great. But my alloy does not like being heated over an extended period of time at 690 - 700.

Starting with a freshly fluxed mirror like surface I’m soon getting what I think is tin oxidation on the surface, which build up as I paw the surface with my ladle over a period of time, say 30 minutes or longer.

A heavy foam like oxidate’d alloy builds up on the surface (edges of the pot since I’m pawing a path clear in the middle and doesn’t reduce when I re-flux. Instead it clings to the cedar shavings (pet store) I’m using even after considerable stirring. Alloy is then being carried out along with the dross when I skim the surface.

How do you keep your alloy fresh when ladle pouring over an extended period of time. Thanks Bill Cook.

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Wm Cook posted this 2 weeks ago

I think what I was trying to ask was whether there is a dynamic situation occurring between the 4% tin, 12% antimony and 84% lead over time when heated at 690-700? John Alexander had a post a while back about someone having left their pot on overnight that maybe I can learn from.

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delmarskid posted this 2 weeks ago

Do you need to have your temp this high. I’ve been able to ladle cast at 650. This may help with the drossing. I used to brush the goop back with the ladle pointed down and let it fill through the spout.

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RicinYakima posted this 2 weeks ago

I cast Linotype at 670*, but only to keep mould temperature up. Every time the pot coil kicks on, the alloy goes rapidly up and down and brings fresh tin to the surface. That is the only reason for bottom pour pots. FWIW

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Wm Cook posted this 2 weeks ago

When I was running at 650-660 I was seeing wrinkles so I ran it up to 690-700 out of habit. In hindsight there were other options to getting and keeping the mold hotter than forcing it with alloy temp.

Running a melt temperature of 670 might solve the problem. I may even be able to pick up my cadence a bit if the mold runs cooler. Maybe. Probably not.

Rick when you said that “the alloy goes rapidly up and down and brings fresh tin to the surface”. Does that mean that the tin is separating from the alloy at 700.

Would that explain the chrome (tin?) looking tinsel that flash cools on my ladle if I do a quick empty dip. That buildup causes me to have to tap the ladle before every dip to keep the ladle clean.

In short, I had no idea that with Linotype the temp difference between 670 and 700 would cause the tin to rise to the surface. Thanks for that. I appreciate the help. Bill.

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RicinYakima posted this 2 weeks ago

Linotype is 100% liquid at 459* F. It would make good bullets at 560* if you could keep the mould hot. 

No, tin does not separate from the the solution. What it does is the tin molecules are exposed to oxygen on the surface and once every hundred thousand or so pick up oxygen and become tin oxide. The higher the temperature the faster that happens. 

The tinsel is indeed, tin oxide. 

I flux with a pea size bit of beeswax every 10 minutes or so. It smokes, stinks and is messy but works for me. REMEMBER THIS ART AS MUCH AS SCIENCE! 

Questions are welcome, but I may not have exact answers. 

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Wm Cook posted this 2 weeks ago

This was a very important lesson for me.

My world had been wrapped around mold temperature and finding a cadence to keep a quality sprue cut with fully formed bases. When you include the need to avoid abusing your alloy with excessive heat it adds another variable and a greater degree of complexity is added to the process.

This is not insurmountable by any means but from my experience this past year working toward cast accuracy, it can only be learned by more time at the casting bench. You can lead a horse to water but …….

I know I’m overthinking this but I wish for a wireless sensor and an LED display so the mold temp can be monitored. This feature would be of no use to a skilled caster and it would be no use for those casting high volumes of 9mm, 7.72’s etc with an aluminum mold but for high end cast accuracy out of a bolt gun I have the unproven theory that 4 & 1’s, 3 & 2’s are bullets with poor formed bases, poor sprue cuts.

And while I’m wishing and wanting how about an off the shelf PID controller for a ladle dipping pot. I ain’t got the fore with all to put the pieces together.

Again, thanks for the help, Bill

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Larry Gibson posted this 2 weeks ago

"I flux with a pea size bit of beeswax every 10 minutes or so. It smokes, stinks and is messy "

 

Drop a couple wood matches onto the melting beeswax.  They'll ignite by themselves and will burn off the smoke and most of the stink.  By the time you're done fluxing they will have burned up and are easily removed with the rest of any residue.

LMG

Concealment is not cover.........

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John Alexander posted this 2 weeks ago

Bill sen: "Running a melt temperature of 670 might solve the problem. I may even be able to pick up my cadence a bit if the mold runs cooler. Maybe. Probably not."

Seems like this would be the quickest and easiest thing to try.

This comment won't be helpful to someone who likes to dip, but I use cat litter to shield the alloy from the air and bottom pour. I have a PID hooked up which is interesting but not sure it changes anything since I still depend on time for sprue to harden to keep near the sweet spot. Seems like the litter ought to do some good but I'm not sure how much, but if oxidation still happens it is out of sight and doesn't distract me from tending to the casting.

John

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Lee Guthrie posted this 2 weeks ago

Hmm.  Hmm.  Please excuse -- this is a Monday morning and this could be side effects from my meds.......

When I read your post somehow my mind inserted a short video of you, along with a couple friends, all wearing black with tall pointy hats, standing around your lead pot and methodically stirring while the smoke was rising.

 

applause

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Wm Cook posted this 2 weeks ago

Someone needs to coin a catchy phrase that would go along with the image Lee had.  Bill.

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Mike H posted this 2 weeks ago

Ric and Larry are telling us something important,fluxing is necessary,many times I have read where people are having trouble with their alloy and melt,a bit more fluxing and less obsession on getting the alloy to some exact perfect temperature would help.

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TRKakaCatWhisperer posted this 2 weeks ago

I find no buildup on the sides of the pot since I started to stir with wood.

 

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Paul Pollard posted this 2 weeks ago

We may not be using enough fluxing material. The following is a partial list which Shakespeare used:

Double, double toil and trouble; 

Fire burn, and cauldron bubble. 

Fillet of a fenny snake, 

In the cauldron boil and bake; 

Eye of newt and toe of frog, 

Wool of bat and tongue of dog, 

Adder's fork and blind-worm's sting, 

Lizard's leg and owlet's wing, 

For a charm of powerful trouble, 

Like a hell-broth boil and bubble.

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delmarskid posted this 2 weeks ago

I bought one of those laser infrared hand held thermometers to check the surface temperature of my mould cavities. I have not tried it yet. Mechanics use them to check exhaust manifold temps so it may work .

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