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silicon bronze


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I had a conversation with Dorothy Stiegler about working Bronze. If memory serves me rigth, 1750 is the upper limit for heat in silicon bronze. Her main point was, buy extra and experiment. Learn the color in your working environment and if possible, use a temperature limited forge.

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If you experiment with it so that you can find the upper limit you can then work safely below that. I find it works just like butter compared to steel's cheese and stainless' Parmesan! You can move it very radically in one heat so you do not need to push the heat limit. In my forge I can see that it is red before it gets too hot, but as Fe Wood says the ambient light levels of your workplace are specific even at different times of day.

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Greetings Iron,


I found it best to turn the shop lights off for better color view and forge at dull red...   Save some of the scraps and form them of for filler rod when brazing..

It makes for a much better color match..  Most filler rod available will not match..   Oddly enough when forging parts of your size you can tell by sound when to quit forging.. A dull thud means your material requires reheat...


Make pretty things


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Most of the bronzes I cast began to melt at around 1800, 1900 degrees, say the lower end of yellow, and was poured around 2200-2300. As soft as silicone bronze is, I'd stay well into the orange range or lower for forging. Maybe about a  light red/dull orange to be safe.


I have much less experience hot forging with it than casting or cold work. Try some and see, just know that if it gets to bright yellow, you're probably in danger of starting to melt it. Nice thing about silicon bronze is it's much safer than some of the "bronzes" containing stuff like zinc. Also, it feels a lot softer than what you'd be used to in steel, even worked cold.

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Why are you using cast iron for your mould? The basic process/principle of casting is that you pour molten metal into a sacrificial mould from sand or clay which can then be broken off easily.


What you are doing is a form of brazing where brass is melted onto the work pieces to effect a joint. The whole point of which is that it should stick... the problem arises if it does not.


Your original post asked for advice about the temperature it could be worked at. On a forging forum context "working" implied forging. Were you actually wanting information about casting? 



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I cast silicon bronze, and pour the excess into steel ingot molds, but the mold is at room temp.  the bronze is shrinking while the mold is expanding, so there is no problem sticking.  If the mold was large, the bronze would stay molten long enough to heat the mold, then braze to it as they both cool together though.


Dripping molten bronze into an iron or steel mold gradually heats the mold, and gives the bronze the chance to braze to the mold.


Silicon bronze is hot short below it's melting/freezing point.  That means that although it is solid, the crystals are not well bonded with each other yet.  During cooling, if a casting can't shrink evenly, or feed more molten metal, there is the risk of it seperating to a greater or lesser degree during the hot short phase.


As Timothy said, if you heat it into hot short temps and try to forge it, it will crumble under your hammer.


If you do overheat a piece and have it crumble though, don't throw it away.  you have spoiled your piece, but not the alloy.  just melt it down and reuse it.  Little or no chemical change happens to the alloy at forging or casting temps.


Do be careful not to mix plumbing bronze or brass with your good silicon bronze though.  Many of them contain lead, and you don't want that in your silicon bronze.


Cheers, Carl

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