Contradictory info in Lymans Casting Handbook 3rd edition

[braindead0]

So, I got Lyman's 3rd edition..and noted a rather glaring contradiction regarding fluxing. There's and entire section devoted to the metallurgy of lead alloys, and it basically (after much technical explanation) says that fluxing has nothing to do with keeping bullet alloys mixed.

Then on pg 57, where it gets to the meat of things.. It says that the greyish 'scum' on the top of a melt is tin and you need to flux to re-incorporate it into the alloy.


??? Anybody have any thoughts on this?

My thinking is that the 'greyish scum' is simply oxidized lead...

On a related note, I got some marvelux flux.. and loaded up my pot.. Seems like marvelux is perhaps a bit harder to deal with than simple wax.. sticks to my spoon and dipper like crazy..

 

[cheygriz]

Good catch, my friend. The old timers always told me that the grey scum was antimony. At any rate, fluxing is important to clean the metal. I don't now if it helps the alloy or not, but I strongly suspect that it does.

One thing's for certain though, frequent fluxing won't HURT anything.

 

[braindead0]

A bit unnerving though. My Dad always thought it was Tin.....

The article basically said flux is only necessary to clean out dross...and only needs to be done when adding more material to the pot.

Interesting stuff..

 

[BigG]

The greyish scum is tin, iirc, and needs flux so it mixes with the other metal. You can tell the difference between slag and tin once you do it a while. Beeswax is good flux.

 

[braindead0]

The greyish scum is tin, iirc, and needs flux so it mixes with the other metal

Therein lies the quandary, according to a rather extensive article in Lymans 3rd edition... tin seperating from lead is an old wives tale, tin will not separate out from lead at liquidus temperature without the assistance of some form of mechanical or magnetic separation processes.

This is the first technical article on the subject I've seen, I wonder if there is any factual backing for the 'it's tin floating on top' viewpoint.

 

[braindead0]

Just called Lyman customer service, the lady I talked to said she'd pass the information on...

 

[BigG]

All I know is it mixes back in after you throw a piece of beeswax on and stir. In contrast, your impurities will float like dust or grit on top of the mercurylike molten lead.

 

[braindead0]

Well, if it's simply oxidation.. removing the oxygen (fluxing usually does that) and stirring/heating the oxidized material will re-incorporate that into the mix.. perhaps. This works on iron oxides quite well without even being molten.

But it will not affect the hardness or tin/lead/antimony content of the alloy. According to the article in Lymans 3rd edition that is...

 

[cheygriz]

I will weigh in again with the one thing in this debate that I am absolutely certain of: Pure beeswax is a damn good flux.

 

[braindead0]

Toilet bowl wax rings work great and are very cheap.....

 

[LAH]

I can't say what the gray matter is on the melt. I can say it returns to the mix when fluxed leaving the top of the melt shinny and clean after the skimming. I use a commercial flux and stir for appox. 1 to 1 1/2 min. When done properly I get no dross, only rust like particles. Our alloy is foundery quality and produces only a 3 pound coffee can of waste per 1500 pounds of alloy using our flux. When using canning wax or bullet lube the waste is higher perhaps a 3 pound coffee can per 800 to 1000 pounds of alloy.

 

[labgrade]

Well, I'll bite then.

I've never used a bottom pour pot, but old friends did & laid a layer of Borax (?) acroos the top. Never did have to flux.

Seems to lend some credence to oxidation (which the borax layer prevents).

I dunno. I flux when the grey skum seems too much. Always just used a smallish hunk of RCBS bullet lube as I've switched to Orange Majic & won't used the former anymore unless hard-pressed.


LAH, care to post your flux?

 

[braindead0]

The borax thing is interesting, I use anhydrous borax for flux when forge welding... It does make for a nice temperature resistant 'coating'... Pretty sure I've got a few pounds lying around, might try it...

 

[LAH]

Labgrade why don't you use a bottom pour pot? I know guys, both hobby and commercial casters, who use the ladle but IMHO the bottom pour is quicker, easier, and for most less messy. Please this is just a simple question and I wish not to start a war.

Fluxing, according to my old Lyman manuals not only cleans but returns materials to the melt. I've never tested the gray matter on top our alloy or 1-20, or wheelweights. I've been told for years it's tin and just accepted it as fact.

There's an excellent article written by Glenn Fryxell titled "The Simple Act of Fluxing" over at www.sixgunner.com and is a must read for the hobby caster. He uses sawdust to flux and leaves the burnt sawdust on the melt to cut down on oxidation causes by the tin making contact with the air as the melt turns over in the pot. While I feel using a covering should work and cut down on the amount of fluxing required it comes down to a matter of waste products for us. The more waste you have the more that must be processed before disposal.

Please understand some of the best fluxing products are highly toxic and should only be used by commercial smelters. The hobby caster is well served by beeswax, canning wax, and certain bullet lubes. As for commercial flux I'm no expert on such but the one I'm using at present and one which I have a large supply of is from NEI.

 

[labgrade]

Simplest reason, LAH, is because I don't have one. I'm sure you're correct about the bottom pour & no flames/wars assumed nor taken.

More than willing to try & accepting donations as we speak.

Casting out of a heavy steel bucket-thing set on top of a Coleman stove - out on the deck. Seems to work very well for a 168 gr Lyman Keith .357 & a 173 gr (or so) .30 FNGC

Already had the stove, the pot & had to buy the moulds & stuff anyway. Just never got around to the "better bucket."

 

[braindead0]

It just bothers me a bit when there is so much "knowledge" passed on (I got it from my dad too) that may (or may not?) be true at all.

The article in Lymans 3rd edition is "The Metallurgy of Molten Lead Alloys" by Dennis Marshall. His credits seem to be good (1997 award from International Metallurgy Society for Metallography, decades of research in lead metallurgy)

I called Lyman and pointed out this contradiction, perhaps they'll get to the bottom of it in the future..

For the time being, I'll probably not flux except to remove impurities... Using a bottom pour certainly helps in that respect ;-)

 

[labgrade]

"Using a bottom pour certainly helps in that respect ... "

Except unless you need to flux to re-alloy your mix.

Glad you brought this up though. I haven't a clue.

 

[braindead0]

His article fits in with what I know of the metallurgy of molten iron alloys... not to say they are the same.

He apparantly did some consulting for laser-cast, so I emailed them hoping they'll forward a request for more references on the subject..

Fluxing isn't really expensive, but OTOH why do it more than necessary?

 

[LAH]

Labgrade there's nothing wrong with the way you're casting. I started with a ladle, 10 pound cast iron pot, and a electric burner myself. Once I was ran out of the kitchen I converted to a camp stove. Like I said I know guys that use Rotwell (spelling) bottom pour lables and think I'm silly to us a bottom pour pot. To each his own. I just can't picture ladle pouring the thousands of bullets we make each week.

 

[labgrade]

No question. LAH, & I'm not bitchin'.

At times, I'll sit down & cast a few hundred - sometimes a 1K+ .... works & I've no bothers about it.

Actually wish that I did somehow break into the "lower-spout" crowd. Never did & don't feel the lack for the volumne I cast.

Each his own. Yes Sir!

But always willing to learn a better/more effcient way ....

 

[braindead0]

My father and I used to cast single cavity with dippers on an old coleman stove (from the 20's we think, it's really old).. Went hog wild when we got a bottom pour ;-)