| ? ? ? The common annealing processes of 20Cr precision steel pipe include recrystallization annealing, stress relief annealing, spheroidizing annealing, complete annealing, etc. The purpose of annealing: mainly to reduce the hardness of metal materials, improve the plasticity, to facilitate cutting or pressure processing, reduce the residual stress, improve the homogenization of structure and composition, or prepare for the subsequent heat treatment. ?
? ? ? Normalizing of 20Cr precision steel pipe: refers to the heat treatment process in which the steel or steel parts are heated to 30-50 ¡æ above AC3 or ACM (upper critical point temperature of steel) for appropriate time and cooled in still air. The purpose of normalizing is to improve the mechanical properties of low carbon steel, improve machinability, refine grain size, eliminate structural defects, and prepare for subsequent heat treatment. ?
? ? ? Quenching of 20Cr precision steel pipe: refers to the heat treatment process that steel parts are heated to a certain temperature above AC3 or AC1 (the lower critical point temperature of steel) for a certain period of time, and then obtain martensite (or bainite) structure with appropriate cooling rate. The common quenching processes are salt bath quenching, martensite step quenching, bainite isothermal quenching, surface quenching and local quenching. The purpose of quenching is to obtain the required martensite structure, improve the hardness, strength and wear resistance of the workpiece, and prepare the microstructure for the subsequent heat treatment.
? ? ? Tempering of 20Cr precision steel pipe: refers to the heat treatment process of steel parts after quenching, heating to a certain temperature below AC1, holding for a certain time, and then cooling to room temperature. The common tempering processes are: low temperature tempering, medium temperature tempering, high temperature tempering and multiple tempering. The purpose of tempering: mainly to eliminate the stress produced by quenching steel parts, so that the steel parts have high hardness and wear resistance, and have the required plasticity and toughness.