Semi – axial induction heat treatment process
The engine power passes through the transmission and the rear axle and is transmitted to the wheel by half axle so that the wheel bears the torque and impact. The early half shaft was treated with tempering. Now, most of the shaft has been used in the induction hardening process. The key to improving the fatigue strength of half shaft is whether the flange is continuous with the hardening layer and the ratio of the depth of the hardening layer to the diameter of the rod. The shaft is generally made of 40Cr, 40MnB, and 42CrMo steel.
Half – shaft induction quenching method, there are two kinds of scanning quenching and primary heating. The scanning quenching method is suitable for batch production of multiple varieties; The one-shot heating method is generally used for mass production on special aircraft. In terms of productivity, quenching quality, energy saving effect, and production cost, the one-time heating method is better than the scanning quenching method, but it requires a high-power power supply, a large-flow water pump, and the structure of the special inductor is relatively complex, so the one-time investment cost is very large, and it is only suitable for mass online production.
(1) Half shaft scanning quenching method generally adopts a vertical general quenching machine or special quenching machine. The structure of the half-shaft inductor should first heat the flange surface to the quenching temperature and then scan the rod and spline parts for quenching.
The technical requirements of modern half shaft quenching usually stipulate that the flange face quenching diameter shall not be less than XMM. The larger the x value is, the higher the design requirements for inductors will be. At the same time, as the workpiece does not move when heating the flange face, the total heating time of the rod near the flange R is longer, which is equal to the heating time of the flange plus the scanning heating time, so the hardening layer in this area is particularly deep.
Another characteristic of semi-axial scanning quenching is that, when the scanning quenching reaches the rod and spline itD, the magnetic field lines on the effective ring will often be offset, that is, the rod part has not been heated to the transition section, while the spline has been heated (this phenomenon becomes more significant when the outer diameter of the spline is larger than that of the rod part).In the process, it is often used to reduce the scanning speed in this transition section, so that the temperature in this section is uniform through conduction. After half shaft scanning quenching, since there is no self-tempering formation, it is necessary to supplement tempering. Induction tempering is often used in the tempering process.
(2) Semi-axle one-step heating quenching method heats the quenching area of the whole semi-axle in one step, which is an advanced technology. It adopts two rectangular effective heating rod parts and spline parts which are equipped with the magnetic body above, the effective ring of the flange part is semi-annular, and one side of the shaft end, when the semi-ring is too short to get a suitable hardening pattern, often additional collector.
The power frequency used by the semi-axle heating method is usually 4-kHz, while the power is usually more than 400kW according to the heating area of the semi-axle. Because the primary cooling area is particularly large, it is necessary to equip with a large capacity water pump, adopt a polymer water solution, and adopt a quenching machine with a correction roll. Heating, correction, quenching, and self-tempering are completed at one time. Domestic automobile manufacturers have successfully applied this process to production, and achieved the effect of increasing productivity several times, greatly increasing bending fatigue strength, and saving energy.