A brief analysis of the heat treatment process of piston rod quenching by medium frequency induction quenching equipment and the prevention measures of brittle fracture

The piston rod is the main wearing part of the mud pump. It transmits alternating axial loads during the working process. Its working conditions are very harsh. Therefore, it requires high hardness and small roughness. In order to meet the requirements of its working performance and improve its service life, many manufacturers use medium frequency induction quenching equipment to perform simple heat treatment to meet the requirements.

Piston rods commonly use 40Cr, 35CrMo, and 42CrMo steel as raw materials. Today, let’s talk about the surface quenching of 35CrMo steel piston rod. The quenching technology requirements are that the hardness reaches 52-60HRC after induction quenching and low-temperature tempering, and the bending distortion is ≤0.5mm. The heat treatment process is (860~870)℃×2h+(560~600)℃×2h, oil cooling after quenching, rapid water cooling after high temperature tempering, and the hardness after quenching should be higher than 50HRC. The frequency used for medium frequency induction quenching of the piston rod is 8000Hz. The piston rod rotates on the machine tool for continuous heating and decreases at a certain speed to achieve continuous sequential quenching. Its main parameters are: output voltage 750V, power factor 0.9~0.95, quenching heating temperature 880~900℃. Finally, temper at 160~180℃ for 2h. When the piston rod is quenched by medium-frequency induction heating, the gap between the sensor and the part should be uniform, and the rotation speed and descending speed should match to avoid the appearance of black and white soft bands, which will reduce wear resistance.

A common heat treatment defect of piston rods in medium frequency induction quenching is brittle fracture. Measures to prevent brittle fractures of piston rods are:

1. Strictly inspect and control non-metallic inclusions and other defects inside the material to prevent structural defects and coarse grains from causing a decrease in strength and an increase in brittleness.

2. Increase the quenching and cooling rate of the piston rod so that it can obtain a martensite structure after quenching and a tempered troostite structure after tempering, which can significantly improve the performance of the piston rod.

This article briefly describes the heat treatment process of medium frequency induction quenching of the piston rod and the prevention measures of common defects and brittle fracture. I hope it will be helpful to you. As a professional manufacturer of medium frequency induction hardening equipment, Zhengzhou Gou's equipment has complete functions and is easy to operate. It can not only quench the piston rod, but also the running wheels, crankshafts, etc. It can also be used for diathermy forging, which is widely used. If you are interested in such equipment or the medium frequency induction quenching heat treatment process, please call us for consultation.