Alloy issues?

[ryanmattes]

There wasn't a dark surface, it stayed bright and shiny the whole time. Silvery-er, if that's a thing, which I assumed was just the additional tin. The dross on the top looked the same as before, when I was working with just WW.

I just don't know the temps, but I've got a thermometer on the way. But it was set the same as it was in previous casting sessions; all the way up during the initial melt, backed off as the last pieces start to melt. Probably too hot, but no good way to tell.

Right up until I dumped the ingots out of the pan and saw the crystallization I hadn't seen anything that looked any different from previous sessions.

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[OS OK]

Well, I'll follow this one to the end...this is a really good riddle to solve, I'll learn something here for sure.

I can't for the life of me find a picture of a muffin ingot I took that showed that fine grain structure of antimonial lead, it was a much finer grain than what your showing.

I am sure that there's an answer to this riddle, someone somewhere has a picture of the same basic lead you used and can explain what happened.
I guess this is one of the mysteries about casting that keeps me coming back for more...there's always something more to learn.

[alamogunr]

Always thought that the solder rating was lead/tin, 60/40 was 60% lead and 40% tin. Have I been reading this wrong?

I hate to disagree with anyone, but everything I have found shows tin/lead as the convention for specifying solder. I have several 25# rolls of 40/60 solder that are labeled Sn40/Pb60.

I wish it was the other way around but I know that when it was ordered, the spec. was 40/60. I got it when my former employer was overstocked and wanted to get rid of it.

[Dusty Bannister]

Agree with John. Tin/Lead

https://en.wikipedia.org/wiki/Solder

Lead-based. Sn 60 Pb 40 solder. Tin - lead (Sn-Pb) solders, also called soft solders, are commercially available with tin concentrations between 5% and 70% by weight. The greater the tin concentration, the greater the solder’s tensile and shear strengths.

[fredj338]

From Rotometals:
60/40 Tin/Lead - The most popular dipping solder for electronic applications. Its low melting range makes it ideal for delicate work
Regardless, unless the bar solder or clip ww are not as described, your alloy should NOT be brittle. As noted, i make LHP with 20-1 all the time & they are anything but brittle. Even ole Elmer Keiths fav 16-1 was not brittle.

[John Boy]

mixed 1lb of 60/40 bar solder with 9lbs 12oz of stick-on WW,

Step 1 ... if you have any of the stick on weights left - test them for hardness to determine if they are less than 99% Pb. and if so - they have antimony in them

In addition, any cast bullets with a pot temperature too high will produce crystallized bullets. What was your pot temperature of the melt? If it was not 680 - 710 ... you have what you got

[quilbilly]

In my fishing jig making business of the last several decades, I never found WW's to be of consistent alloy. There were wild variations in hardness making some batches unreliable for certain lead jigs that anglers wanted to bend for action. As a result, I finally decided to stick to roofing and isotope lead from recyclers to make my lures as well as create my own alloys for boolits.

[alamogunr]

Regardless, 40% tin or 60% tin, it shouldn't make a substantial difference in the alloy unless you are aiming for a very high percentage of tin like 20%+.

[ryanmattes]

It sounds likely that the pot was way too hot, and in pouring off half and adding plain lead I lowered the temp enough to get casts that didn't look crystallized. It's also likely that the WW had other metals mixed in.

I don't have any of the raw WW left, I turned them all into ingots, most of which I mixed with the bar solder. I had about 6-7 lbs of the WW ingots left, but I have now mixed those 50/50 with the 20:1 ingots. They made decent enough bullets for range plinking. I never tested the hardness of the original WW.

Someone also mentioned the settings/markings on these pots not being consistent depending on the ambient temps, and this happened right after a cold front hit. I had the settings the same as before the cold front, but that was a 20F-30F degree difference in ambient temperature, which might be the reason it behaved so differently.

More experimentation is in order, which I'll do, probably extensively, starting tomorrow night. And next week I expect to have a new batch of 20 or so lbs of WW, plus I have a line on some stained glass solder, probably 20-30 lbs of it.

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[ryanmattes]

Ok, so I got my thermometer in and melted that same batch of alloy to see if it was a temperature problem. I followed the same process, and it happened again, but now I think I know why.



Left to right - first 5 casts


Left to right, second 5 casts


I think my mould was entirely too hot. I've been setting the mold with the bottom actually in the lead to warm up, and I waited for the thermometer to come of to 700. I forgot, that temperature included the influence of the mould, which means the mould was so hot that the sprue stayed liquid for a long time. The mould was approaching 700 degrees! So these bullets are what you might call "super-frosty."

It only happened for the first couple casts, and then the mould cooled enough they they started coming out like normal.

I also got in a couple new moulds, some Lee aluminum ones, and I did it again with some 358-125-RF I was casting later. Once again, I laid the mould in the lead to heat up, and the aluminum gets hot way faster than the brass NOE mould I was using for the .45s.





So, mystery solved, maybe? I still don't know why the ingots look so crystallized, but when I poured the leftover metal into my muffin molds, they did it again.



This time I know the temps were in the right range, so maybe I do have a bunch of antimony from the WW and the aluminum muffin tin is cooling it fast enough to make it crystallize?


Any thoughts?

[JonB_in_Glencoe]

It doesn't take "a bunch" of antimony in a Lead alloy to make it crystalize...1% will probably do what I see in your photos.

[OS OK]

I was thinking maybe that the grain structure changes in the pot as the temperature varies. When you quick/flash cool from a particular temperature you would get different grain structure outside especially and inside the cast.
I had read a lot about the 'phases' that these metals go through in the mixture and was looking for that particular article and the graph they showed but couldn't find the bookmark...
I did find this article in LASC that seems to say that in a different manner...


The Myth of Arsenic By: Wiljen

http://www.lasc.us/WiljenArsenic.htm

Second paragraph into the article, I think he is saying this...I'm not sure,

Heat treat hardening really isn’t the appropriate term either. What is actually happening is a process that has long been known as Hall-Petch Strengthening. Hall-Petch Strengthening is a method of strengthening materials by changing their average grain size. Typically, the smaller the grain size, the higher the strength exhibited. It is based on the observation that grain boundaries impede dislocation movement and that the number of dislocations within a grain have an effect on how easily dislocations can traverse grain boundaries and travel from grain to grain. So, by changing grain size one can influence dislocation movement and yield strength. As examples, heat treatment and changing the rate of solidification are ways to alter grain size.

I might be reading between the lines but to me...this seems to explain the variations in the appearance of the grain structure....how hot & how quickly it cools.

[kmw1954]

ryanmattes I get the same crystallization when I pour into an aluminum muffin pan. Not worried though because the cast bullets come out fine.