High-frequency induction heating machine heat-treats tappets, how much do you know about the process?

The valve lifter is a key component of the automobile engine. The valve lifter moves up and down in the engine cylinder block duct, transmitting the cam action and its thrust to the pushrod to transmit power. Therefore, during the working process, the tappet has to withstand huge friction. For this reason, many manufacturers use high-frequency induction heating machines for heat treatment to improve the hardness, wear resistance and service life of the tappet. The effect is very good.

(1) Technical requirements for heat treatment. The lifter and the camshaft are a pair of friction pairs, so the material selection and heat treatment requirements of the two are mutually restrictive. In mass production, steel valve lifters are usually formed by cold extrusion or hot heading.

(2) Heat treatment of tappet

1. The purpose of heat treatment for the tappet is to obtain higher surface hardness, high contact fatigue strength and wear resistance. In order to prevent decarburization on the surface of the tappet, the heating process of heat treatment is usually carried out using a high-frequency induction heating machine. The quenching tool is a hanging structure made of Q235 steel, with many short columns welded on it, and the tappet can be hung on it. Preheating is also done using a high-frequency induction heating machine. The quenching heating temperature is 840-850°C. It is cooled in 20# mechanical oil. The oil temperature is less than 80°C. The end hardness of the quenched tappet is greater than 62HRC. In order to ensure that the hardness meets the requirements, it is recommended to perform tempering heat treatment. The tempering temperature is 180-200°C. The base hardness after tempering is in the range of 54-62HRC.

2. Surface treatment of tappet

a.Quenching. Preheat (840±10)℃, heat at 1050℃×8min, oil cooling, hardness 48-53HRC.

b. Tempering (560±10)℃, water cooling.

This article briefly talks about the high-frequency heat treatment process of automobile tappets. When performing heat treatment according to the above process, everyone must be very serious and careful to avoid defects during the heat treatment process that affect the service life of the tappets.