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Old 07-05-2017, 07:51 AM
Senior Member
Join Date: Dec 2012
Location: near yelloystone park
Posts: 179
Default metalurgy 101

alloy metals behave diferently depending on the alloy and temperatures. The college professor had a carbon steel wire streched between two insulators wired in series with a light bulb. He turned on the switch, the light on and the wire started to heat up and expand, sagging down. then when it got almost to toaster red the wire shrank . The professor explaned that at the critical temperature the molecular structure of the iron and alloying elemants changes, becomes non magmetic. He turned it off and the rapid air cooling kept the wire tight. He explaned that when heat treating a piece of tool steel heating then rapid cooling keeps the structure dense and hard. some tool steels become fragile and will crack and break like a piece of glass. If you polish a piece that has been hardened , then slowly reheat you will get the rainbow colors as the steel molecture structure start to change back. sometimes a propane torch soft flame to allow the steel to slowly cool down, or packing parts in sand.
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