Mush (you huskies?)

[leftiye]

I smelted about 60 lbs of linotype (from sticks of type), and about the same amount of stereotype (maybe not, but it was individual and BIG letters) tonight. Linotype is a eutectic alloy right? Melts at a low temp (450 degrees), no mush etc. Right? Well I got bigtime mush as it melted, maybe 3/4 inch of it. I had to go over 825 degrees, and flux it well to get it to re combine. Got a LOT of grey ash stuff (not from the flux) as dross, maybe a pound of it from each batch. Second pot I put the dutch oven lid on it and put some sawdust in the pot. It still made the mush- just as much.

I'm wondering if this is just oxide from a batch of lead that has been sitting for a long time or maybe the tin has been depleted out of it. Any guesses? I haven't hardness tested it yet. I can't until I cast some boolits that fit in my Saeco tester. This will also let me see if it makes the mush still when remelted. My guess is that it will. Something is wrong I'm sure. Anybody experienced this before?:confused:

[montana_charlie]

I don't know much about linotype, but I am certain of two things. (1) It is eutectic because of the ratio of metals within the alloy, and (2) it has probably been melted many times before a bullet caster would pick it up as 'scrap'.

'Melted many times' makes me doubt that it is still holding the original ratios, especially when experienced users talk about 'tin depletion' being a common thing.
So...maybe 'scrap' linotype is 'eutectic'...and maybe not quite.

When a printer finishes his workday, would it be common for him to carefully 'reduce' the oxides formed during that day...or just turn off the melter and go home. Somehow, I am more inclined to believe the oxides are allowed to solidify, along with the main load of alloy.

Maybe that is your 'mush' when you remelt...a hefty load of unreduced oxides.

Try the stick fluxing method, and use the 'mash and submerge' action to see if you can force that scum to recombine with the alloy.

CM

[snuffy]

I bought some "linotype" from a scarp dealer once. At least that's what he said it was. Upon melting it, it formed a scum that almost looked like lead foam. That was a very long time ago, but IIRC I skimmed it off, the rest of the lead made lousy boolits!:roll: I saved it for making lake Michigan cannon ball fishing weights.

[KYCaster]

The same thing has been discussed in a couple other threads recently. Concensus seems to be flux until it returns to the melt. That has always worked for me.

I think its caused by ink residue on the type, but I have no way of proving that.

Jerry

[Lead melter]

I had the same problem about 2 weeks ago. Threw in a piece of paraffin about the size of my thumb, ignited and let it burn away. Then some Frankford Arsenal flux compound, covered with a lid and let it sit about 10 minutes. The scum melted back and the dross was a hard film on top easy to get off. Good luck.

[leftiye]

I did flux it and stick stir it back into the melt. I'll remelt it and see if it makes the foam (foam is a good term) when remelted. I was afraid to just skim it off as I was pretty sure all of my antimony and tin would go with it. I'll get some boolits casted and see how it stacks up BHN wise. Thanks for your help!

[AZ-Stew]

Let me clarify.

"Mush" may mean different things to different people.

A Eutrctic alloy (such as linotype) has a single tempreature for "freezing" and "thawing". As the pot temperature rises, it goes from solid to liquid. No squishy state in between. Same goes for the cooling process. The metal will be liquid until the eutectic temperatue is reached, then it will suddenly become solid. No semi-melted state in between.

If your melt is liquid near the bottom of the pot and full of semi-melted stuff near the surface, you either have a contamination problem (dirt or other metals) or a non-eutectic alloy. Fluxing may help you re-combine the metals and obtain the casting alloy you want. Skimming after fluxing will remove the contaminents.

Regards,

Stew

[leftiye]

I remelted 5 lbs. of both batches tonight, and cast a few boolits of each batch. They tested out at BHN 22 for the linotype, and about BHN24 for the other stuff. This was immediately after cooling, so the metal is plenty hard. Used an old Lee ladle (tiny ladle) I've had forever, there was gobs of slag with the alloy at 600 degrees. Slag got in the way of pouring, and would plug the sprue hole, preventing a quick clean pour. I suspect that either there is a contaminant or maybe too much tin in this alloy.

[andrew375]

I've suffered this. It is caused by contamination, probably Zinc. Likely at some point some Zymek (used in die cast parts) got chucked into the pot. The clue is in the fact that raising the temperature gets it back into solution. If it was the result of the alloy not being eutectic then the entire melt would go through a "mushy" stage, not just the surface.

I would suggest you get rid of this contamination by holding the melt at a point where the bulk of the alloy is liquid and skimming off the mush that does indeed have the appearance and texture of foam.

[Lloyd Smale]

ive melted thosands of pounds of lino and have allways fluxed it in. I allways figured it was a combo of oxidation and ink that was left on the plates.

[leftiye]

Thanks to everyone for the help. Long ago I melted some linotype, which didn't do this. Am still using it. Other lino which came in ingots didn't do it either.
Andrew, Very well thought out! Thanks for the help. I do hesitate to dump the slag due to possibly losing tin from the melt. This alloy looks like it was casting okay if the slag weren't in the way. Wouldn't zinc make casting difficult? I usually bottom pour, so I think it will cast okay ( or get one of them Rowell Ladles). I'll let the slag accumulate on the top, and hardness test the boolits. If it doesn't lose hardness, then I might skim off the dross. I can always add tin, I have several hundred lbs. of solder.

[andrew375]

Thanks to everyone for the help. Long ago I melted some linotype, which didn't do this. Am still using it. Other lino which came in ingots didn't do it either.
Andrew, Very well thought out! Thanks for the help. I do hesitate to dump the slag due to possibly losing tin from the melt. This alloy looks like it was casting okay if the slag weren't in the way. Wouldn't zinc make casting difficult? I usually bottom pour, so I think it will cast okay ( or get one of them Rowell Ladles). I'll let the slag accumulate on the top, and hardness test the boolits. If it doesn't lose hardness, then I might skim off the dross. I can always add tin, I have several hundred lbs. of solder.

One of the design requirements of type metals is that they are eutectic alloys, which for our use simply mean they change state (phase) at a single temperature rather than start to change at one temperature and finish at another. A good example of an alloy designed to do the latter is plumbers solder, the property of going through a semi liquid stage is what enables you to "wipe" a joint, where you can scoop a gob of the solder on to a cloth pad and then massage it around and in to the joint.

A good example of a non eutectic alloy we commonly use is wheel weight alloy which is a simple lead - antimony mix, here in the UK the standard for WW alloy is for 2%- 2.4% Antimony. When you melt WW alloy it will go through a mushy stage but it will all be in that condition, not just the surface. Lead and Antimony will make a eutectic alloy at the ratio 87.3%Pb-12.7Sb.

What is happening in the alloy as it goes from liquid to solid is that the atoms link together to form crystals, like building a pile of bricks into a wall. The problem is that with different atoms they will only link together in certain combinations, this is not just differences in size but also in how the atoms actually link. Now, just like if you are building a wall from two different sizes of brick there will be a particular sequence and ratio that will give you a uniform finished article without odd gaps so there is a set ratio at which to metals can build a crystal, that ratio is the eutectic ratio.

As WW alloy solidifies it forms crystals of 87.3Pb/12.7%Sb and the surplus lead is ejected. This is what makes the alloy "mushy"; it is actually a mix of lead/antimony crystals in suspension in an increasingly lead rich liquid. When fully set and viewed under a microscope you see a structure of Pb/Sn crystals interspersed with “blobs" that are lead crystals.

If you have an antimony rich alloy then you get the same result but with crystals of pure Antimony being formed. A common use for such an alloy is for white metal bearings. Running in an engine wears away the soft eutectic alloy crystals to expose the hard antimony crystals that actually support the moving part. The spaces between the exposed peaks allow oil to flow.

The above applies to the alloy being cooled slowly; the technical phrase is "under equilibrium conditions". If you cool the alloy fast, by quenching, than the surplus lead cannot be ejected from the crystal matrix, the result is that the matrix gets stressed as it attempts to push the surplus lead out. This give increased strength and so hardness. The process is called "precipitation hardness.

That is as far as I am willing to explain things here as going any further requires pictures and diagrams. Instead I refer you to the Lyman cast bullet handbook that has a very good article on the subject. You might also want to check out books on materials technology and basic metallurgy. By good fortune lead alloys are used in text books to explain the above concepts.

The problem with the Zinc is that it wont easily dissolve in to the molten lead so what you have are two solutions one fully liquid and one semi solid. The Zinc solution is on the surface because it the less dense of the two. Like crude oil on water. The problem is that being composed of solid crystals suspended in a liquid the crystals can jam up if they try to flow through any restriction, which is why Zinc buggers up bottom pour pots and ladles.

One other thing is that when an alloy is molten the constituents are "in solution" that is they are dissolved into each other, just like sugar is dissolved in water. This is how Antimony can be part of a lead melt that is several hundred degrees below the melting point of Lead. Tin and Antimony can no more come out of the alloy than alcohol can separate out off a hundred year old wine. What you are skimming off the surface, apart from the usual collection of dirt and detritus is Lead Oxide, Tin Oxide and Lead-Tin Oxide. This layer on the surface of a clean melt is only one molecule thick. Once the oxides form, as they do immediately, they seal off the rest of the alloy from the atmosphere and the reaction stops.

[Ricochet]

I believe that the only common type metal alloy that's eutectic is linotype.

[felix]

Radiator lead as well. When you really get down to the practical definition, it means no slush stage. The two temperatures, the melting and the freezing, are the same for the object which is composed of TWO or more DISTINCT constituents. ... felix

[jonk]

Let me clarify.

"Mush" may mean different things to different people.

A Eutrctic alloy (such as linotype) has a single tempreature for "freezing" and "thawing". As the pot temperature rises, it goes from solid to liquid. No squishy state in between. Same goes for the cooling process. The metal will be liquid until the eutectic temperatue is reached, then it will suddenly become solid. No semi-melted state in between.

If your melt is liquid near the bottom of the pot and full of semi-melted stuff near the surface, you either have a contamination problem (dirt or other metals) or a non-eutectic alloy. Fluxing may help you re-combine the metals and obtain the casting alloy you want. Skimming after fluxing will remove the contaminents.

Regards,

Stew
I disagree with this a bit. Stew would be right if a uniform heating of the metal could be assured; however, the point of contact in the pot closest to the element will heat and melt first, followed by the rest. Also, the part of the mix exposed to air is a radiant surface moreso than the sides of the pot; it liquifies last. However, it may be hot enough to exhibit a plastic response at the melting threshold- about the same consistency as oatmeal, i.e. mush in my book.

Same on hardening. The surface hardens but if you poke it with a sharp metal rod you will see liquid metal fill the hole. Come to think of it that's how water freezes as well, as any ice fisherman will tell you.

I do think there is merit to the idea that the lead in the mix melts first, ergo the ability to carefully melt out zinc contaminants for instance, so you might see some 'mush' from metals seperating too, until the melting point of the highest is reached. As such metals are liberated in very small amounts, they float to the surface as mush.

In any case I don't worry about it. If it melts in and casts good bullets I'm happy.

[felix]

Jonk, I think what Stew is saying is that there is no slush stage with an "eutectic" alloy. Either it is liquid, or it is solid. That would mean a strong delineation between the two. Yes, you can have solids within the liquid, but no slush. However, I have never seen this "perfect" alloy at home, no matter what it is called. Some Corky (Sundog) and I made by accident were very, very close. Accident here means unintentional. ... felix

[Backgear]

Now and then we read posts about Zinc WW problems, so my question is, if someone has a batch of Zinc contaminated WW what can be done to salvage it?

[38 Super Auto]

Andrew375: Nice post-very informative.

[QUOTE= If you cool the alloy fast, by quenching, than the surplus lead cannot be ejected from the crystal matrix, the result is that the matrix gets stressed as it attempts to push the surplus lead out. This give increased strength and so hardness. The process is called "precipitation hardness.
[/QUOTE]

I assume this is the mechanism for water cooled bullets having higher BHNs?

[leftiye]

Fwiw, I've read other threads about zinc contamination interfering with casting, but always assumed that it was turning the alloy "bad" or into an alloy that actually wouldn't cast. (I guess this is because I've until recently had lots of experience with alloys with hard to remove oxides that played h@!! with the actual casting.) Is this correct, or is this slag interference that I got what they were talking about? This alloy actually seems to cast okay, just lots of slag.

[felix]

Zinc and aluminum, together or separately, pull in the sides of the boolit when cooling within the cavities. Call it surface tension, like water not spilling over the glass edge when the glass is just barely too full. Copper cools so dang fast into solid form and floats to the coolest surface such as the pot/ladle nipple. You can see the copper floating when pouring lead with too much copper back and forth between two pots. It looks like a sheet. Zinc and aluminum are comparatively captured in the lead for any sheeting to take place, or it could be that I have not seen it occur because of the lower amounts within the lead. Different fluxes are typically used which help keep stuff like this in solution until "properly" poured. Industrial applications not typically for home use. ... felix

[Ricochet]

Lead alloys won't maintain internal stresses for long, because they creep under extremely low pressures and recrystallize at room temperature. The reason precipitation hardening works after quenching alloys of lead with metals like antimony works is that when the alloying element is trapped in a supersaturated solid solution at room temperature it crystallizes out in far more numerous, smaller crystals than when it precipitates during slow cooling from high temperature. (Because the atoms are less mobile in the matrix at lower temperature, and can't easily diffuse over longer distances to get together in bigger crystals.) The larger number of small crystals "nail" together the slipping planes of lead atoms at many more points than the fewer, larger crystals that form at higher temperatures. When the lead planes can't slip across each other as easily, the metal is harder and less malleable.

[leftiye]

I remelted this stuff this afternoon and lost 40% of it in slag (mush) that I skimmed off. Just tickles the stuffing out of me! Junk costs $2.00 an lb. after the loss, no answer from the thief that sold it to me!

[Old Ironsights]

Lead alloys won't maintain internal stresses for long, because they creep under extremely low pressures and recrystallize at room temperature. The reason precipitation hardening works after quenching alloys of lead with metals like antimony works is that when the alloying element is trapped in a supersaturated solid solution at room temperature it crystallizes out in far more numerous, smaller crystals than when it precipitates during slow cooling from high temperature. (Because the atoms are less mobile in the matrix at lower temperature, and can't easily diffuse over longer distances to get together in bigger crystals.) The larger number of small crystals "nail" together the slipping planes of lead atoms at many more points than the fewer, larger crystals that form at higher temperatures. When the lead planes can't slip across each other as easily, the metal is harder and less malleable.

Ya know, that read all scientific like... ;)

[KYCaster]

I think there is a basic flaw in the reasoning here. Many people, here and in other threads, talk about "eutectic alloys" and "no slush stage". I really believe that this has nothing at all to do with the original question, i.e. "What is the foam on the melt?"

Consider the most common "eutectic alloy" on our planet....water. Water is liquid at 33*F and its solid at 31*F...no argument there, but what is it at 32*F?...liquid or solid? Put a thermometer in a bucket of water and sloooooly lower the temperature and when ice starts to form on the surface and sides of the container the temp. will be 32*F. The thermometer will continue to say 32*F until the very last molecule of water becomes solid and then will drop to 31*F. For every pound of water in the bucket, you have to remove a particular amount of energy to change it from liquid to solid...that's the definition of BTU (British Thermal Unit)...the heat required to change the temp. of one pound of water one deg. F.

Now agitate the container while you change the temp. and what happens? You mix the liquid water with the solid water and get...slush. That's the stuff that ruins your blue suede shoes when you walk across the Wally World parking lot in the winter time. BUT, they salted the parking lot to eliminate the ice...now what's the temp. of the slush?

Same deal with the alloys we use. Linotype (84-12-4) is a eutectic alloy. Apply heat and at some point it will melt. Hold the temp. at the exact melting point of the alloy and it will appear to be "mushy". Add or subtract any ammount of any component of the alloy and the "mushy" state will occur over a wider range of temp.

So my point is, the "slush" stage has nothing to do with the foamy layer on top of the melt. I have used, literally, TONS of linotype from many different sources and I have yet to find any reason to believe that, for the purpose of cast boolits, the composition is anything other that 84-12-4. Sure, the Sn may be depleted somewhat, but for our application its insignificant.

If the alloy you have is in the form of type or spacer strips or the common lino ingots, is there any reason to believe that it is anything other than linotype? Is there any reason to believe that a typesetter would add Zinc or anything else to the alloy? I don't think so.(caveat emptor)

I seldom use 100% linotype, most often I add it to WW or pure lead to get 92-6-2 alloy, but I have seen the "foamy" surface on many occasions and in every instance, flux and stir will cure the problem. I think its due to either ink residue on the type or dust particles from long term storage that causes it.

I've also seen similar effects when adding Antimony, but that's a whole 'nother topic.

Jerry

[leftiye]

Well, it were linotype, it was in letters, lines of type, and spacers, and every time you melt it and flux it back in and remelt it 40 % by weight in crud reappears on the top as it is melted, and the crud doesn't dissapear until it gets above 700 degrees and is fluxed extensively. Then it doesn't cast with a ladle for spit because of the crud forming so rapidly on the surface.

Ink or dirt would have cleaned off at the first fluxing (and a lot did), as would virtually anything else except a metallic alloying contaminant. I do think that this must be zinc as Andrew375 suggested. I'm guessing that after it got contaminated the printer just raised the temp, and continued to use it. At any rate the fact that it re occurs after being fluxed into the metal makes it just about unuseable with that in it.

As for the eutectic thing, this metal starts melting BELOW 450 degrees, and the slag wont' go back into slution again until almost 300 degrees higher. Eutectic alloys- like the water example remain at the one temperature throughout the phase change.

There ain't no using this stuff with that crud in it. I'll try remelting the foam, slag, crud, and see what temp it melts at etc.