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.