Several methods for tempering steel ball and time control skills

Tempering when steel quenching into martensite then heated to 150 ° C - With 170 ° C tempered, tempering temperature, according to its internal organization structure change, divided into four stages: 1) The decomposition of martensite; 2) The change of residual austenite; 3) The change of carbide; 4) Secondary hardening: when the more carbide forming elements contained in the steel, the tempering stage 4 temperature area ( About 500 ~ 550 ℃) Forming alloying cementite or special carbide. The precipitation of carbides, will make the hardness increases again, referred to as the secondary hardening of the image. Tempering purpose: to reduce or eliminate the quenching stress, plasticity, toughness and hardness, strength, plasticity and toughness of the appropriate coordination, in order to meet the performance requirements of the steel ball. 1 carbon steel quenching the mechanical properties of steel after tempering tempering properties, often in terms of hardness. Alloy steel tempering characteristic, basic similar to carbon steel. But with the secondary hardening steel is different, also can't simply use M parameters for characterization of tempering degree. 2. Low temperature tempering temperature tempering is also called 'eliminating stress tempering. Tempering temperature range is 150 - 250 degrees Celsius, organization for tempering martensite after tempering. Steel with high hardness and high wear resistance, but the internal stress and lower brittleness. After carburizing and hardening the surface of the parts, after tempering hardness of 58 - in general 64HRC。 3. Tempering tempering time should include the workpiece cross-section evenly heating time required to achieve tempering temperature and tempering hardness according to the requirements of M parameters to achieve the time needed to complete the organization change, if you consider the elimination of internal stress, is under different tempering temperature should be considered stress relaxation time. To give priority to with stress relaxation of low temperature tempering time should be longer than tabular data, long can reach dozens of hours. Type of secondary hardening high alloy steel, and its change tempering time should be based on the carbide process was determined by experiment. When contained more residual austenite, and by the secondary hardening eliminate, should also determine the number of tempering.