Process analysis of heat treatment of gear pump using high-frequency induction heating equipment

The gear pump is composed of a pump body, a front and rear pump cover, and a pair of gears that mesh and rotate in the pump body. During the working process, these parts are required to have good wear resistance, certain toughness and strength, etc. The main parts that require heat treatment include gears, gear pump bodies, gear pump shafts, and positioning pins. The specific parts are as follows, and they all have certain technical requirements. In order to meet the working requirements of these parts, we usually use high-frequency induction heating equipment for heat treatment, and the effect is very good.

(1) Working conditions and technical requirements

1. Gear pump gear. During the working process of the gear pump, the pulsation between the tooth surfaces is subject to contact stress and corrosion, the tooth root is subject to the pulsating bending stress, and the whole is subject to the complex effects of bending fatigue stress. Therefore, in order to improve the overall strength and have high wear resistance , perform induction hardening heat treatment on low-pressure gears.

2. Gear pump shaft. The pump shaft is a part that transmits torque. During the rotation process, it is affected by impact, torsional stress and bending fatigue stress caused by hydraulic pressure. The shaft neck is subject to wear. The form of failure is partial fracture at the shaft keyway or overall torsion. Therefore, the pump shaft is required to have high strength and hardness as well as good toughness. Medium and high pump shafts are quenched with 42CrMo or 40Cr.

3. Positioning pin. It plays a connecting role in the gear pump. It must have high hardness and certain strength requirements. Therefore, quenching + medium temperature tempering can meet the technical requirements.

4. Gear pump body. Under the action of hydraulic pressure on the pump body, the gear is pressed to the side of the low-pressure oil chamber. The tooth top contacts the pump body and generates pressure and scrapes, which has a negative impact on the pump pressure and volumetric efficiency. Therefore, the pump body is required to have high strength. And wear resistance, the use of deformed aluminum alloy and cast aluminum alloy, and solid solution + aging treatment can meet its working needs.

(2) Heat treatment of gear pump parts

1. Heat treatment of CB-H and CBF gear pump gears. Made of 20CrMnTi carburized steel, technical requirements: surface hardness is 58-63HRC, core hardness is 32-45HRC, coaxiality ≤ 0.05mm. High-frequency induction heating equipment is used for quenching heat treatment at 830-850°C, and the surface hardness is above 58HRC. Tempering is also carried out using high-frequency induction heating equipment, the process temperature is 180-220°C, and the surface hardness after tempering is 58-63HRC.

2. Heat treatment of gear pump shaft. Made of 42CrMo, it requires quenching + medium temperature tempering. The overall hardness is 38-43HRC, and the coaxiality is ≤0.05mm.

High-frequency induction heating equipment is used for heating in order to reduce deformation. The process specification is (830-850) ℃ × 30 minutes, and the oil is cooled after the heat preservation is completed. Tempering temperature is 470-500℃, oil cooling or water cooling to avoid secondary tempering brittleness.

3. Heat treatment of positioning pins. The material is 45 steel, technical requirements: overall hardness is 35-40HRC. The required hardness can be obtained by using the quenching + medium temperature tempering process. Considering that the parts are relatively thick and short, the heat treatment deformation of the parts will not be large, so high-frequency induction heating equipment is used for heating. The heating temperature is 830-850°C to ensure sufficient heating. , the brine temperature of the cooling medium should not be higher than 30°C, and the hardness after quenching is 50HRC. The temperature of medium temperature tempering is 400-420℃.

This article briefly introduces the high-frequency heat treatment process of the gear pump. When operating according to the above process, everyone must be very serious and careful to avoid defects in the gear pump that affect its service life.