Heat treatment of quenched and tempered steel

Pre-heat treatment
In order to eliminate and improve the organizational defects and internal stresses of the former process (casting, forging, rolling and drawing) and to make the organizational and performance preparation for the later process (quenching, cutting and drawing), annealing or normalizing Process is pre-heat treatment. On the pre-quenched and tempered steel prior to cutting heat treatment, pearlite steel can be carried out in the Ac3 above a normalizing or annealing; martensitic steel with high content of alloying elements are first Ac3 above an air-cooled quenching, and then Ac1 The following high-temperature tempering, so that the formation of tempered sorbite. 

The final heat treatment
Quenched and tempered steel general heating temperature above Ac3 30 ~ 50 ℃, quenching martensitic organization. Tempering sorbite should be obtained by tempering at high temperature after quenching. Tempered tempering temperature according to the performance requirements of the parts, generally take between 500 ~ 600 ℃, depending on the specific scope of the chemical composition of steel and parts of the technical conditions may be. Because alloying elements will slow down the decomposition of martensite, carbide precipitation and aggregation and the transformation of residual austenite and other processes, the tempering temperature will shift to higher.