45 steel is a high quality carbon structural steel, axle is one of the application direction, reasonable heat treatment of 45 steel can effectively improve the service life of axle.
The axle is a cylinder with variable diameter. To achieve the full length surface quenching depends largely on the structure design and manufacture of inductor. The design of heating inductor should mainly consider (1) to make the surface temperature of the heated parts uniform; (2) inductor loss is small, high electrical efficiency; (3) Sensor cooling is good; (4) Simple manufacture, enough mechanical strength, easy to operate and use. The axle heating inductor is made of a circular inductor made of rectangular copper pipe and cooled by water, and the parts are cooled by jet cooling with attached water spray ring after heating. In order to reduce magnetic leakage as much as possible in induction heating and improve heating efficiency, the spacing between the inductor and the parts should be as small as possible, but there should be enough clearance to ensure that the relative movement of the inductor and the axle can proceed smoothly.
First of all, China’s locomotives, vehicles are using high quality carbon steel axle, throughout the overall situation, it should be said that carbon steel axle is mature, reliable. There is no mature technology in China to choose carbon steel or alloy steel for high-speed train axle material. Due to different national conditions, different technical points of view, the selection of axle materials are not the same, but all belong to the category of low carbon steel. Applying surface induction hardening on the basis of quenching and tempering or normalizing can prolong service life exponentially. Therefore, this is an important process to improve the service life of the axle. Surface induction hardening is very effective in improving the bending or torsional fatigue strength of axle and reducing the sensitivity to notch and stress concentration. After surface induction hardening, due to the high effective toughness and plasticity of the core, the hardened layer is allowed to have a high hardness, so as to maintain high wear resistance, strength and residual compressive stress, and give full play to the potential of the material anti-fatigue. The high frequency induction quenching of axle abroad has developed from local quenching and subsection quenching in the past to the present full-length surface quenching.
Secondly, the heating temperature and heating time when the material and the original structure are constant, the phase transition temperature increases with the heating rate In order to obtain qualified quenching microstructure, the corresponding quenching temperature is also increased. The heating rate of axle induction heating is generally 30 ~ 100 ℃/ s, and 890 ~ 960 ℃ is the best heating temperature for surface quenching of 45 steel axle. In order to obtain deeper depth of hardened layer, the upper heating temperature is selected. Longer heating time and higher heating temperature can obtain deeper heating depth, on the contrary, the heating depth is shallow.
The size range of 45 steel easy to crack is 5 ~ 11mm, too small or too large are not easy to crack. Because the axle diameter is large, the heating depth is deep, so the heating power is 150 ~ 220kW, the heating time is 6 ~ 15s, and the heating temperature is 920 ~ 960 ℃.
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