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White metal alloy question


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So I’ve been casting my own scenic items / accessories, I make my own moulds with Mold Max 60.

 

The metal alloy that I’ve been casting with is pewter, being 97% tin + 3% bismuth.  This alloy does not have the white metal look and feel to it, it’s much shinier.

 

So I had an XRF test done on a piece of white metal from a Wizard Models wagon kit (my favorite quality white metal) to see what exactly it’s made of, the results show 66.7% lead + 33.3% tin.

 

I was excited to see how basic the alloy was. It’s basically 2 parts lead to 1 part tin. I have plenty of lead fishing sinkers. I melted them down, and mixed 2 pounds of them with 1 pound of tin.

 

After pouring the mixed alloy into the moulds, the end result is not what I expected. It still doesn’t have that white metal look and feel to it. It’s more of a shiny grey than a matte white.

 

Am i doing something wrong? Is there more to alloying than simply mixing the correct ratios of elements together in a furnace?

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Yes, there can be.  Depending on the metals, there may be a small amount (like .1%) of another metal to cause them to alloy.  Consider that lead & tin do alloy fairly well together, but have different melting points and boiling points.  My guess would be that there will be something like a small quantity of bismuth in there, or of copper (or silver).  There must be information out there somewhere on how to alloy what amounts to solder, but exactly where is going to be difficult to find.  Some of it will be trade secret, I am sure.  
There is one suggestion in https://edu.rsc.org/experiments/making-solder-as-an-alloy-of-tin-and-lead/1742.article  in the form of putting a layer of carbon over the melted mixture...

 

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9 hours ago, niteshadex said:

So I had an XRF test done on a piece of white metal from a Wizard Models wagon kit (my favorite quality white metal) to see what exactly it’s made of, the results show 66.7% lead + 33.3% tin.

 

I was excited to see how basic the alloy was. It’s basically 2 parts lead to 1 part tin. I have plenty of lead fishing sinkers. I melted them down, and mixed 2 pounds of them with 1 pound of tin.

 

After pouring the mixed alloy into the moulds, the end result is not what I expected. It still doesn’t have that white metal look and feel to it. It’s more of a shiny grey than a matte white.

 

 

silly question: is the XRF mass based? or is it eventually volume based?

Nevertheless, I am wondering about the relation. Solder is roughly 60% tin and only about 40% lead which will form a eutectic system with a low melting point. Your alloy will not solidify at one temperature, it will solidify in the whole temperature range between 327°C (lead) down to 232°C (tin). This will probably be the reason for the matte and grey appearance.

 

just an idea,

Michael

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In case anyone is interested, I sort of fixed the situation and ended with a satisfactory result...

 

I tweaked the tin and lead ratios, and added a little bismuth. The ratio I ended with is 55% tin, 42% lead, 3% bismuth. The metal is a rich silvery white that really picks up the tiny details.

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On a possibly related subject (If not, apologies for the thread hijack) I am attempting to improve a couple of cast whitemetal farm carts that I made a rather poor job of building a few years ago, but am finding the 70 degree solder I used to build them now has a melting point so close to that of the whitemetal they are proving impossible to dismantle.  My initial assumption was that the solder was suffering from some obscure variation on the theme of age hardening, but it has since been suggested that the solder and the whitemetal formed an alloy with a much higher melting point.

Your thoughts, please.

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The one person who could probably answer that easily is no longer with us.

 

When Adrian Swain used to produce white metal bus kits for me he used several different metals for different parts. some was quite pliable for awkward thin parts, while the metal used for larger parts line bus sides was a harder metal with a higher melting point. If that's any help..

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10 hours ago, mike morley said:

On a possibly related subject (If not, apologies for the thread hijack) I am attempting to improve a couple of cast whitemetal farm carts that I made a rather poor job of building a few years ago, but am finding the 70 degree solder I used to build them now has a melting point so close to that of the whitemetal they are proving impossible to dismantle.  My initial assumption was that the solder was suffering from some obscure variation on the theme of age hardening, but it has since been suggested that the solder and the whitemetal formed an alloy with a much higher melting point.

Your thoughts, please.

I never had any luck with low-melt solder. When I build whitemetal kits, I will usually use solder to tack parts together, then finish off with super glue

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