Hello,
sometimes when making an ingot, the bar or rod will come out of the mold and have a snowflake- like crystaline pattern on the surface…like snow/ frost/ ice crystals on a window.
would anyone know what/ why this is happening, and, if it reduces the integrity of the metal, and should be re-poured?…what might be the cause of it?
julie
I can’t say much regarding alloys.
But in refining we see this when there are impurities in the metal.
This is usually due to contamination with base metals or metals like Ag or Pd in the gold.
What kind of alloy are you melting?
It can be just surface pollutants or overheating so the alloy stratify/separate a bit.
When I pour silver into an open steel ingot mold, I will sometimes get a snowflake shaped crystaline texture on the surface of the ingot in contact with the bottom of the mold. The surface is also near white in color. I have never had a problem forging, rolling or drawing these ingots. I have always attributed this texture to that part of the pour being hotter longer than the rest of the pour in a low O2 environment. That’s all the metalurgy I know. I hope that someone can help explain this. Thanks…Rob
I poured an open mold silver ingot today to see if I could create what I previously called crystals. I also wanted to see what problems might result when the ingot was rolled to a 2X2 square since I needed some 2X2 square wire. Attached is a picture of the crystals. The ingot rolled out fine and I was able to get 23" of 2X2 square wire with no waste. I would be interested in what the metalurgists among might say about these “crystals”. …Rob
I forgot t mention that the scrap did contain a small amount of medium to hard solder…Rob
hi Rob,
yes, that is the same crystal pattern i was asking about…curious to know what causes this, and if it is a concern…
julie
Hi.
There was a discussion regarding the same at GRF.
But there we mostly handle pure metal
99.9+ not alloys.
I think the conclusions was that if the Silver was very pure these patterns could emerge under
certain conditions.
Here, I don’t know. Maybe some stratification with pure Silver on the surface?
Is it workable and the alloy is good, then maybe all is ok?
Here you can see what I mean and read the thread yourself.
Its by Owltech, he has his own youtube channel too.
this has happened to me too. It’s usually just the surface, but I once had a batch of silver scrap that I fire refined by heating and injecting oxygen… it became “spitting” silver, when most of the copper burned off… the oxygen was expelled in large bubbles. It crystalized in the crucible… when removed, it was not workable, having been too hot and cooling slowly… when remelted and poured into an ingot mold, the cooling rate was much faster and there was no crystallization. surface crystallization only is not a problem…annealing will get rid of it…but not necessary if only on the surface…
