What do you know about induction heating surface quenching of crankshafts?

Induction heating surface quenching is a quenching method that uses the principle of electromagnetic induction to cut magnetic lines of force in parts in an alternating magnetic field and generate induced current on the surface. Based on the alternating current skin effect, the surface of the part is rapidly heated in the form of eddy current and then quenched rapidly. Induction heating surface quenching is one of the better surface quenching methods, so it is widely used. Today, we will take the crankshaft as an example to introduce the induction heating surface quenching of the crankshaft.

In mass production of crankshafts, induction heating surface quenching is widely used. Quenching methods usually include: induction quenching method using a full-circle separate inductor with the crankshaft in a stationary state; and induction quenching method using a half-circle quenching inductor with the crankshaft in a rotating state. The crankshaft half-turn quenching sensor consists of four main parts: the effective ring, the outer plate, the positioning block, and the quenching cooling device.

The use of half-turn quenching inductor crankshaft rotation induction heating method not only changes the direction of the magnetic field generated by the inductor from longitudinal to transverse (circumferential), it basically eliminates the shielding of the magnetic field by the crank, thus quenching the axle journal. The hardened area remains uniform, and because the crankshaft rotates relative to the inductor, the inductor uses the positioning block to flexibly track the rotational motion of the journal. With the help of the positioning block, the sensor can stably maintain the gap between the inductor and the journal to ensure This ensures the uniformity and stability of the depth of the hardened layer of the journal after quenching. Therefore, the half-turn inductor rotation heating quenching of the crankshaft is becoming more and more widely used. The advantages of using half-turn inductor rotation heating quenching are that the hardened layer is deep and uniform, the width of the hardened zone is uniform, it can reduce the crankshaft quenching distortion and prevent hole quenching cracks.

The quenching inductor in which the journal and fillet are quenched at the same time is based on the journal quenching inductor, changing the angle of the arc section of the effective circle, and adding a magnetic conductor in the arc section, so that the fillet R and the journal are quenched at the same time. It is heated and quenched under strong induced current. After the crankshaft is induction quenched at the journal and fillet at the same time, it can not only eliminate the tensile stress at the junction of the journal and the fillet, but also generate greater compressive stress at the fillet, thus greatly improving the fatigue strength of the crankshaft. The fatigue strength of the forged steel crankshaft can be more than doubled after the journal and fillets are quenched at the same time.

Simultaneous induction hardening of crankshaft journals and fillets will increase distortion. According to the shape and size characteristics of the crankshaft, selecting a reasonable quenching sequence, determining the appropriate delayed quenching cooling process based on the quenching cooling characteristics of the crankshaft material, etc. can reduce the quenching distortion of the crankshaft. In order to ensure the dimensional accuracy of the crankshaft during operation, a special fixture should be used for static reverse straightening during the low-temperature tempering process after induction quenching, and the phase change plasticity should be used to achieve a stress-free straightening effect.

Autothermal tempering is often used after induction quenching of the crankshaft. For crankshafts with high dimensional accuracy requirements, a low-temperature tempering furnace with hot air circulation should be used for tempering. For example, a 40Cr steel crankshaft is tempered at (160±20)℃ for 2 hours. Full tempering can control the hardness within a narrow range, such as 55~60HRC can reduce grinding cracks and ensure dimensional stability during long-term use.

This is a brief introduction to the induction heating surface quenching of the crankshaft. Zhengzhou Gou's is a manufacturer specializing in the production, manufacturing and sales of induction heating equipment. If you have any questions about induction heating surface quenching, you can call us freely.