Analysis of the local quenching heat treatment process of the two convex surfaces of the cam using a medium frequency induction quenching machine

The chassis of Dongfeng Motor Company's EQ1141G 8-ton flat-head vehicle is produced using Japan's Nissan diesel technology. There are four S-shaped brake cams on the front, rear, left and right of the car. The brake cam is a mechanical rotary or sliding part that transmits motion to a roller that moves close to its edge or a needle bar that moves freely on the groove surface, or it receives force from such rollers and needle bars. The brake cam is used when braking. During the process, it is subjected to a large torsion moment and a large friction force, so the design requires the sucker rod and fillet to be quenched at intermediate frequency, and the two convex surfaces of the cam to be locally quenched at intermediate frequency.

Part material is 45 steel, forging blank, pre-heat treated for modulation. The hardened layer of the cam and rod is 2-3.5mm, the rounded hardened layer is greater than 0.5mm, and the hardness of the quenching area is HRC55-60. We usually use a medium frequency induction quenching machine to perform quenching heat treatment on them.

After many tests (the sharp corners of the ring inductor were overheated; the stiffness of the flat profiling inductor was too poor, the quenching effect was very good, and it was difficult to guarantee a single heating gap), the final test was successful with the overall heating and partial cooling of the convex profiling inductor.

The effective circle of the sensor has four water chambers, and there are two water chambers corresponding to the two convex surfaces, which are passed through quenching cooling water. When the two convex surfaces reach the quenching temperature, they are sprayed for cooling and quenching. In addition, the two water chambers corresponding to the two concave surfaces have cooling water sprayed to the concave surfaces. When the cam is inductively heated, since the vortex is a closed circulation flow, the convex surface is heated and the concave surface is also heated at the same time. In order to make the concave surface temperature lower than the quenching temperature , spray water to cool it while heating. These are the four functions of the water chamber. When the heating is terminated, the water spray in the water chamber ends.

In order to prevent the sharp corners from overheating, two notches are opened at the corresponding positions of the sensor to keep the medium-frequency current away from the sharp corners.

As an important part of the car, the heat treatment of the cam plays an important role both in the cam itself and in the car. Therefore, it is very necessary to master its heat treatment process. This article briefly introduces the medium-frequency heat treatment process of brake cams. I hope it will be helpful to your work.