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Tempering is a process of heat treating, which is used to increase the toughness of iron-based alloys. Tempering is usually performed after hardening , to reduce some of the excess hardness , and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air.
By 1931, the tempering process was developed to control chocolate bloom, but it was not understood how it worked. The effects on the crystal structure were not understood until the 1970s. By the 1950s, the tempering process involved cooling chocolate to 86 °F (30 °C), until it was "mushy", then raised to 91.4 °F (33.0 °C) before it was molded.
The tempering colors can be used to judge the final properties of the tempered steel. Very hard tools are often tempered in the light to the dark straw range, whereas springs are often tempered to the blue. However, the final hardness of the tempered steel will vary, depending on the composition of the steel.
The steel is then tempered. In this process, austenite is transformed to martensite by step quenching, at a rate fast enough to avoid the formation of ferrite, pearlite, or bainite. [1] [2] In the martempering process, austenitized metal part is immersed in a bath at a temperature just above the martensite start temperature (Ms).
Tempering (metallurgy), a heat treatment technique to increase the toughness of iron-based alloys Temper mill, a steel processing line; Tempering (spices), a cooking technique where spices are roasted briefly in oil or ghee; Tempered glass, a type of safety glass processed by controlled thermal or chemical treatments
Differential tempering begins by taking steel that has been uniformly quenched and hardened, and then heating it in localized areas to reduce the hardness. The process is often used in blacksmithing for tempering cutting instruments, softening the back, shaft, or spine, but simultaneously tempering the edge to a very high hardness. The process ...
Using tempered glass can pose a security risk in some situations because of the tendency of the glass to shatter completely upon hard impact rather than leaving shards in the window frame. [10] The surface of tempered glass does exhibit surface waves caused by contact with flattening rollers, if it has been formed using this process.
No tempering is required after austempering if the part is through hardened and fully transformed to either Bainite or ausferrite. [5] Tempering adds another stage and thus cost to the process; it does not provide the same property modification and stress relief in Bainite or ausferrite that it does for virgin Martensite.