How to Anneal Steel
In metallurgical terms, annealing steel is heating the metal to a specific temperature and holding it there until the steel is at its softest and most malleable. The steel is then cooled and hardened. Since each steel has a specific annealing temperature and a unique time it must be held at that temperature, thermal tables have been established for specific steel grades. These tables are produced by either the manufacturer of the steel or by independent standardization bodies such as the American Iron and Steel Institute, or AISI. Does this Spark an idea?
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Instructions
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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.
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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.
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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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Tips & Warnings
Standardization companies such as the American Iron and Steel Institute, American Society for Testing and Materials and the Society of Automotive Engineers list the annealing charts for most steels. For custom or specialty steels the annealing charts are available through the foundry.
Annealing steel requires extremely high heat; caution and protective equipment are required to prevent injury.
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