The original structure of the 9SiCr steel workpiece is spheroidal carbon content, which increases the Ms point. After the workpiece is rapidly cooled, cryptocrystalline martensite is obtained. At the same time, staggered lath dislocation martensite is formed in the structure. In high-carbon alloy steel, at the same strength, lath-like dislocation martensite has better toughness than lamellar martensite, thus reducing the hidden danger and danger of quenching fiber cracks in workpieces, making 9SiCr steel workpieces Improved fatigue strength. The above analysis explains the main reason why the service life of 9SiCr steel rolling gear dies is improved after ultrasonic induction annealing and quenching.
The test analyzed the reasons for the large distortion of Cr12MoV steel and the poor identity of the same mold. Cr12MoV steel is a high-carbon, high-alloy alloy steel. After quenching, the residual carbides are about 8%-9%, and the residual austenite is 18-20%. The workpiece structure is unstable. During quenching and cooling, the positions of each workpiece are different and the cooling conditions are different. The amounts of martensite and retained austenite obtained after cooling are different, so their volume changes are also different. This results in large distortion of the Cr12MoV steel rolling gear die. Moreover, the distortion amount of the same auxiliary mold is inconsistent, and the identity is poor.
After ultrasonic induction heating and quenching treatment, the shrinkage of the rolling tooth mold is less than 0.06mm, and the shrinkage of the same mold is stable and the uniformity is good. Then, after the ultrasonic induction heating and quenching of the gear rolling mold, the roundness distortion was large and did not meet the technical requirements. In response to this point, a replication test was added, and five methods were used to improve the roundness distortion of the workpiece, thereby selecting better measures to solve this problem. The measure is to process two process holes with a diameter of 12mm at 120°C at the keyway position, so that the workpiece set variable is reduced from the original 0.06 to less than 0.02mm, thus fully meeting the technical requirements.
The analysis pointed out that 9SiCr steel has good hardenability. When the workpiece obtains the required hardness and hardened layer, using appropriate processes to achieve tissue stress distortion in the workpiece is a technical idea for improving the gear rolling die process. In ultrasonic induction heating quenching, the purpose of adding two process holes is to balance the stress of the workpiece while reorganizing the superposition of stress and thermal stress. At the asymmetry of the quenching cooling section of the workpiece, additional process holes are added to make the cross section of the workpiece more balanced. It tends to be symmetrical, which promotes the internal stress distribution to become balanced, because it further reduces the distortion of the workpiece and the roundness distortion of the workpiece, which meets the technical requirements of gear rolling die processing.
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GS-ZP-1200
