The boundaries of cold and hot working are divided by recrystallization temperature, lower than recrystallization temperature for cold working, and higher than recrystallization temperature for hot working.
The work hardening produced during the hot working of the press is quickly counteracted by the softening of the recrystallization, so that the hot working does not bring about the work hardening effect. Recrystallization is when the cold plastic deformation of the metal is heated to a higher temperature, due to the increase in atomic activity, the shape of the grain began to change from the broken elongated grain into a complete equiaxed grains, this cold The process of reorganization of the deformed tissue during heating is called recrystallization. Due to the restoration of the structure after recrystallization, the strength of the metal, the decrease in hardness, the improvement of plasticity and toughness, and the disappearance of work hardening. Recrystallization temperature is not a constant temperature process, it is from a certain temperature, in a temperature range of continuous process, the occurrence of recrystallization of the minimum temperature is called recrystallization temperature. The main factor affecting the recrystallization temperature is the pre-deformation process of the metal, the greater the degree of metal deformation, the lower the recrystallization temperature. The trace impurities or alloying elements in the metal increase the recrystallization temperature; increasing the heating rate will cause the recrystallization to be delayed to a higher temperature and prolong the holding time to reduce the recrystallization temperature.
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