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- Jun 7, 2013
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The problem with bronze is that the molten metal picks up gasses from the furnace atmosphere that results in nasty porosity, the cure for it is to use a oxidizing flux during melting, then plunge in a degassing tube containing (I think) phosphor bronze pellets and mix it around; after that treatment, the metal, when the dross is skimmed off should appear bright and shiny, if it still looks dull it probably needs more; if you use too much, the metal gets super fluid and results in dirty castings where the fluid metal soaks out into the sand. This can be the result of re melting too much "returns", that is castings and sprues/gates/runners that were likely over de oxidized, along with new metal, then being re melted and re deoxidized. Been there, done that.
Brass, on the other hand has zinc in it; when melted, exerts a vapor pressure on the melt, excluding the contaminating gasses.
Another tip; do not add silicon bronze scrap to any other brass/bronze mixture; the result is a casting so brittle that it breaks like glass and chips/spalls like obsidian.
Brass, on the other hand has zinc in it; when melted, exerts a vapor pressure on the melt, excluding the contaminating gasses.
Another tip; do not add silicon bronze scrap to any other brass/bronze mixture; the result is a casting so brittle that it breaks like glass and chips/spalls like obsidian.
