There are several annealing processes for wear - resistant castings
Recrystallization annealing is usually referred to as recrystallization annealing because recrystallization occurs once during heating and cooling process. This annealing method is quite common in steel. Steel recrystallization annealing process is slowly heated to Ac1 (eutectoid steel or hypereutectoid steel) more than 30 ~ 50 ℃, keep the appropriate time, and then slowly cooled down, by heating during pearlite (or there are proeutectoid ferrite and cementite) into austenitic phase transformation recrystallization (round) the opposite happened in the process of the cooling and the second round of phase transformation, recrystallization, form the crystal grain more fine, slice layer thicker, organize uniform pearlite (or and eutectoid ferrite and cementite). If the annealing temperature is above Ac3 (subeutectoid steel), the steel will undergo complete recrystallization, which is called complete annealing. If the annealing temperature is between Ac1 and Ac3 (subeutectoid steel) or between Ac1 and Acm (hypereutectoid steel), the steel will undergo partial recrystallization, which is called incomplete annealing. The former is mainly used in the casting of hypoeutectoid steel to eliminate the microstructure defects (such as wechsler microstructure, banded microstructure, etc.), make the microstructure become fine and uniform, so as to improve the plasticity and toughness of steel pieces. The latter is mainly used for medium carbon, high carbon steel and low alloy steel castings. In addition, the annealing temperature between Ac1 and Acm is also incomplete annealing. Spheroidizing annealing will be heated to a temperature of steel castings to begin to form the austenitic temperature above 20 ~ 40 ℃, slow cooling after heat preservation, in the process of cooling of pearlite lamellar cementite into a ball, reducing the hardness.