1. Characteristics of induction heat treatment

Induction heat treatment is an advanced heat treatment technology with high productivity, no environmental pollution, easy automation and energy saving. This technology has been developing rapidly since its inception, and the largest user of induction heat treatment technology is in the field of automotive parts.

Induction heat treatment technology because of high quality, high efficiency, energy saving, environmental protection and many other advantages, in line with the needs of modern automobile production, the technical level of rapid improvement [4]. High-frequency induction heating equipment is widely used in the field of auto parts, such as valves, tappets, connecting rods, crankshafts, camshafts, gears, universal joint bell shells and half shafts. Among them, continuous quenching or impact quenching of the valve rod end and automatic continuous operation of the cone surface have become the most successful technology of valve induction heat treatment at home and abroad, and have won the favor of valve manufacturers, more than 100 domestic valve manufacturers have more than 5 high-frequency equipment. Among them, our company has more than 30 induction hardening equipment (or continuous production lines), with an annual output of more than 20 million induction hardening valves, making it one of the manufacturers with the largest output and the largest number of exports among Chinese valve manufacturers.

2. Basic requirements for induction hardening of internal combustion engine valves

Induction quenching is carried out after heat treatment (quenching and tempering treatment) of the valve to meet the wear resistance requirements of the rod end surface (or cone surface). In the Technical Conditions for Intake and Exhaust Valves of Internal Combustion Engines (GB/T23337-2009) and the Technical Conditions for Valves of Automobile Engines (QC/T469-2002), it is pointed out that the hardness of the rod end surface after surface quenching should be ≥ 48HRC. When the rod end length> 4mm, the depth of the hardened layer shall be 2mm) or the depth of the hardened layer shall be 0.6mm. The hardened layer of the conical surface of the disc after surface quenching shall be ≥ 1.5mm, and its hardness value shall comply with the provisions of the drawing. The grain size of the rod end and the conical surface after induction quenching shall be finer than Grade 8. It can be seen that induction hardening of the cone and rod of the valve is required by the standard and is an indispensable heat treatment method to improve the surface hardness of the valve.