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 Your current position: Home >> Three Phenomena of Heating Temperature in Heat Treatment FurnaceThree Phenomena of Heating Temperature in Heat Treatment FurnacePublished by：2023-4-7 Categories:Industry news Viewed by: 3898 times General overheating: overheating occurs when the heating temperature during heat treatment is too high or the holding time at high temperatures is too long, which causes austenite grain coarsening. Coarse austenite grains can lead to a decrease in the strength and toughness of the steel, an increase in the brittle transition temperature, and an increase in the tendency for deformation and cracking during quenching. The reason for overheating is that the furnace temperature instrument is out of control or mixed materials (often caused by not understanding the process). The overheated structure can undergo annealing, normalizing, or multiple high-temperature tempering, and under normal circumstances, undergo re austenitization to refine the grains. Fracture inheritance: After heat treatment of steel with overheated structure, reheating and quenching can refine austenite grains, but sometimes coarse granular fractures still appear. There are many controversies about the theory of fracture inheritance. It is generally believed that impurities such as MnS were dissolved into austenite and enriched at the grain interface due to excessive heating temperature. However, during cooling, these inclusions precipitate along the grain interface and are prone to fracture along the coarse austenite grain boundary when subjected to impact.
Heredity of coarse structure: When steel parts with coarse martensite, bainite and widmanstatten are re austenitized, they are slowly heated to the conventional quenching temperature, or even lower, and the austenite grain in the heat treatment furnace is still coarse, which is called structural heredity. To eliminate the heritability of coarse structure, intermediate annealing or multiple high-temperature tempering treatments can be used.
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