What are the disadvantages of the long shaft of 40Cr steel after being quenched by high-frequency induction hardening equipment? How to correct it?

The long shaft is an important general-purpose part on mining machinery and equipment, and has a wide range of applications. Long shaft parts of drilling and production equipment require high hardness and high strength on the surface, high overall strength and toughness, wear resistance, corrosion resistance, and high resistance to bending fatigue and torsional fatigue. The long axis of drilling equipment is often made of 40Cr steel. During production, it was found that a batch of 40Cr steel long-axis quenched and tempered by high-frequency quenching equipment produced large deformation, and the runout exceeded 1-2mm, which far exceeded the control accuracy of the workpiece technical requirements (runout ≤ 0.2mm). In order to improve the quenching quality of the long shaft and save the deformed and out-of-tolerance workpiece, a high-frequency quenching equipment treatment test was carried out on the out-of-tolerance 40Cr long shaft, and good results were obtained.

There are two types of long-axis workpieces, the specifications are 60mm x8mm (wall thickness) x 2300mm, 50mm x 2300mm; the depth of quenching and hardening is 0.7mm, and the hardness is 600-720HVO.l; 3kWC0 laser is used, the spot diameter is 5mm, and the scanning speed is 20mm/s. The test found that the long axis was bent and deformed during the quenching asymmetric scanning treatment. The function relationship between long-axis vibration deformation and quenching scan length is related to workpiece size, shape, quenching power density, etc., and the test K≈1. According to the analysis, the characteristics of high-frequency quenching equipment quenching are the rapid rise and rapid cooling of the local temperature of the parts, the uneven heating and cooling temperatures of various parts of the workpiece, resulting in anisochronism of thermal stress and tissue stress. Under the combined action, the workpiece is deformed and bent. Quenching hardening and martensitic transformation are carried out within the depth of 0.7mm corridor layer, so the hardened layer is very thin, and the stress of the phase transformation structure caused by the surface area is small. On the other hand, high-frequency quenching equipment is a high-density energy heat source, with high heating heat density and concentrated energy, so the thermal stress deformation caused by it is more obvious.

To sum up the above analysis, use the quenching deformation law of high-frequency induction hardening equipment to perform quenching correction treatment on quenched long-axis deformation out-of-tolerance parts, and select and adjust quenching parameters, such as power size and spot diameter, according to the influencing factors of K in the formula KL x lo-3 The size, scanning speed, etc., by controlling the laser scanning length, can effectively control the quenching deformation vibration of long shaft parts. The test found that after the above-mentioned high-frequency quenching equipment quenching correction method is used for the long-axis parts with vibration deformation exceeding 1-2mm, the vibration of the long-axis deformation is between 0.07-0.20mm, and the long-axis deformation is between 0.07-0.20mm. Using the above-mentioned process, the final deformation and vibration are less than 0.20mm. This test method has been used in production and has achieved good technical results. This improved process provides an effective method for people to use high-frequency quenching equipment to control quenching, reduce deformation of long-axis workpieces, and improve product accuracy. At the same time, the application of this method in production has also brought good technical and economic benefits.