On 2018-08-08 14:48:54
Automotive half axle heat treatment process
Why heat treatment of car axle?
Half shaft is car rear axle torque and a certain impact of important structures, is one of the main components of transmission power, in the heart of the working process of the main reducer, differential torque to the drive wheels, finally coming which have passed the engine torque and drive rear axle circular cone gear wheel forward, spline there are both sliding and impact force, the service life of the axle shaft depends on spline tooth compressive ability, requires a high static torsional strength and torsional fatigue life and good fatigue resistance and impact toughness, deeper hardening layer and so on, to meet the needs of the normal solid axle shaft.
General automobile axle shaft adopts continuous quenching heating ring sensors, and to strengthen the efficiency of heating, often containing silicon steel sheet on effective ring magnetizer, notch is inclined to the flange rounded corners, the purpose is to use notch effect, will be effective on intermediate frequency electric current in the rounded out to correspond to the rounded, available here in 10 s rapid heating, can be very reasonable surface hardening layer.
The process parameters and technical requirements of surface heating and quenching are as follows: the heating power is 150 ~ 300kW, the frequency is 2500 ~ 3000Hz, the half shaft adopts intermediate frequency induction heating surface quenching, the cooling water flow rate is not less than 10m/s, the surface compressive stress of the quenched workpiece can reach 700 ~ 800MPa, after 250℃ tempering, it can be reduced to 400 ~ 500MPa. Therefore, to ensure the existence of a certain residual compressive stress on the surface of the semi-axle will help to make the semi-axle have a higher fatigue strength, which can be self-tempering or tempering in the furnace, the temperature is controlled at 180 ~ 250℃, and the time is 90 ~ 120 min. In order to ensure the uniform heating of the flange fillet, the inductor can be added with a magnetic flux. Tempering after surface quenching is generally carried out induction heating tempering immediately after quenching, followed by further tempering in well furnace or box furnace. Can also be induction quenching immediately after tempering in the furnace. It is proved that the former method is beneficial to prevent the crack before tempering.
The hardness of surface quenching of half shaft can be tested by hardness tester and file. Rockwell hardness tester is usually used to judge whether the hardness after quenching meets the technical requirements. In the practice of heat treatment, the hardness of the surface of parts should be qualified.
The alignment of the half axis should be cold as much as possible. After heating with oxyacetylene hot spot, once the temperature is higher than the phase change temperature, a thick martensite will be formed after rapid cooling and the stress will be great. Therefore, the half axis will gradually expand under the effect of repeated loads and fatigue fracture will occur.
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