Process analysis of integral quenching method using high-frequency induction heating equipment to longitudinally rotate and heat parts

High-frequency induction heating equipment is used to conduct longitudinal induction heating of parts. It uses longitudinal heating instead of circumferential heating. It uses two or more effective conductors arranged along the axis of the part to generate an induced current that flows longitudinally (axis direction) along the surface of the part. Heating is carried out when the parts rotate. The entire quenched surface is heated, and after reaching the quenching temperature, the entire surface is spray quenched or immersed quenched.

Longitudinal heating uses a loop inductor instead of the focused inductor used in circumferential heating. This kind of inductor is an ideal induction heating device for parts with steps, flanges, grooves, fillets, etc. and slender parts, such as half shafts, drive axles, etc. It replaces scanning or continuous heating quenching, as well as stationary heating with focused inductors.

The continuous induction heating quenching method is commonly known as the moving quenching method, which is completed through the relative movement between the heated part and the inductor. It is suitable for high-frequency continuous quenching of equal-diameter shaft parts. Its inductor is generally designed as a single-turn or multi-turn annular type. When a single-turn water-jet inductor is used for heating and quenching, the deformation of the parts is small. Due to its small output power (especially the inductor used for quenching small-diameter shafts), the production efficiency is low.

Although the multi-turn inductor can make full use of the power provided by the high-frequency heating equipment, it increases the heating area and heating depth of the parts in the coil and requires the addition of annular water sprayers, making it difficult to ensure the reliability of the inductor and water sprayers. Concentricity, therefore, the parts produce larger quenching deformations.

The advantages of using high-frequency induction heating equipment for continuous induction heating and quenching of parts: relatively long and large workpieces can be processed with smaller-power high-frequency heating equipment, the equipment occupies a small area and the production cost is low. For a long time, the traditional continuous quenching method mostly uses a ring-type continuous quenching inductor, which generates an induced current in the workpiece along the fillet direction. This process itself has a shortcoming that is difficult to overcome, that is, wherever the axial size of the workpiece changes (such as a stepped shaft), uneven hardened layers appear. The hardened layer is often discontinuous at the steps and at the shaft shoulder. It's easy to overheat. These factors often limit the application of continuous induction quenching. Sometimes in order to strengthen the steps, rolling or shot peening processes have to be added.

The adoption of the longitudinal rotating heating integral quenching method not only solves the above problems, but also expands the application range of continuous induction heating quenching and achieves good application results. Its biggest advantage is that it is suitable for processing variable-section parts with large diameter differences, such as drive axles, stepped shafts, ball pins and other parts. It can ensure that the surface temperature of each section of the part is uniform and the hardened layer is continuous, thus improving the strength of the part, especially the fatigue strength. For half-shaft parts, this method also has the advantages of greatly improving production efficiency and reducing energy consumption.