The colour of a piece of polished steel after it has been tempered in air.
When steel is heated in air, a thin layer of iron oxide forms on its surface. The colour of this oxide varies with the temperature at which the steel is held and was previously used to judge the tempering temperature of tools.
See also hardening colours.
The colour of a piece of polished steel after it has been tempered in air.
When steel is heated in air, a thin layer of iron oxide forms on its surface. The colour of this oxide varies with the temperature at which the steel is held and was previously used to judge the tempering temperature of tools.
See also hardening colours.
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