What are the hardness changes of 12Cr1MoV seamless steel pipe after quenching and tempering

The working conditions and the shape of the part should be noticed when determining the hardness of the quenched and tempered 12Cr1MoV seamless steel pipe parts. Generally speaking, the fatigue strength of high hardness, tensile strength, yield strength and smooth samples are all high, but the plasticity index decreases, brittle failure tendency and stress concentration sensitivity increases. Therefore, when there is a notch (spline, groove or section change greatly) on the 12Cr1MoV seamless steel pipe, in order to uniform the stress and reduce stress concentration, the lower hardness can obtain higher fatigue performance.

The determination of hardness of quenched and tempered 12Cr1MoV seamless steel pipe must take into account the requirements of manufacturing process and the load conditions in use. Considering the manufacturing process, it is hoped that 12Cr1MoV seamless steel pipe parts will be quenched and tempered in rough condition and then machined and assembled. In this way, the deformation and decarbonization of 12Cr1MoV seamless steel pipe during heat treatment will be eliminated in the later cutting process. However, the hardness of the parts with this manufacturing process can not be too high, generally not more than 300 HB, individual not more than 350 HB. Otherwise it is unfavorable for cutting. Higher hardness 12Cr1MoV seamless steel pipe parts (such as some automotive semi-axles require 341-415HB hardness), can only be machined first, and then tempered, at this time 12Cr1MoV seamless steel pipe heating should prevent decarbonization and deformation, and sometimes it need to increase the straightening process after heat treatment. The hardness allowed by cutting can be increased appropriately in small batch or single piece parts.