- 1). Place steel in a furnace preheated according to the steel's thermal table. Allow the steel to preheat for the required reference preheat time. The thicker the piece of steel, the longer the preheat time required to properly anneal it. For a form of steel such as AISI simple 1040, the preheat temperature is about 1,100 degrees Fahrenheit. For a high carbon tool steel such as O-1, the preheat temperature is 1,250 to 1,300 degrees.
- 2). Increase the furnace temperature to the annealing temperature. This temperature varies from steel to steel. Simple 1040 is annealed at 1,600 to 1,850 degrees, while O-1 tool steel is annealed at a lower 1,450 to 1,500 degrees.
- 3). Cool the steel slowly, about 34 degrees Fahrenheit per hour, until the steel reaches about 90 degrees Fahrenheit. The steel can then be cooled to room temperature.
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