The material of traction gear and its relationship with railway locomotive

The material of the traction gear, the materials of the traction gear of the railway locomotive mostly use surface hardened steel, which can be divided into carburized hardened steel and induction heated surface hardened steel according to different hardening methods. The former uses low carbon alloy steel, and the latter uses medium carbon alloy steel. For the material of the driving gear, the gear teeth are relatively worn due to the small number of teeth, and low-carbon alloy steel is mostly used at home and abroad. Smelting of materials Although the level of steel smelting in China has improved somewhat over the years, there is a certain gap with foreign developed countries. Qishuyan Locomotive and Rolling Stock Technology Research Institute once analyzed the original traction driven gear of the US ND5 diesel locomotive. It found that the material used is equivalent to China 45 steel 1, and we have to develop and use the new alloy steel grade 50CrMo in the domestic process. (A), the performance of the material and the performance of the gear can meet the requirements of the locomotive. There are many reasons for this, but one important reason is that the purity of the material is high, the sulfide inclusions are very small, the oxide inclusions are few and distributed in small dots, the tooth blank is forged reasonably, and there is no band segregation in the material. The metallurgical quality of steel has a great influence on the contact fatigue and bending fatigue strength of gear materials. At present, almost all gear steels in China are smelted and cast in the atmosphere by ordinary electric furnaces or open hearth furnaces. The oxygen content in steel is generally in the range of 25-40 ppm, and the oxygen content of some steel grades such as 20CrMnMo is even as high as 30-130 ppm. The content of non-metallic inclusions is high and the band structure is also serious, which reduces the fatigue strength of the gear. .
Foreign countries pay more attention to the metallurgical quality of gear steel. The United States, Japan, Germany, etc. generally use ladle degassing, vacuum smelting, electroslag remelting of refined steel, and refined grain processing. When we used 17CrNiMo6 material to manufacture locomotive traction gears for a well-known foreign company, we found that to meet its requirements, it took a lot of manpower and financial resources to meet the requirements in our country's best special steel mills. In recent years, the design and manufacturing level of locomotive traction gears in China have been step by step internationally, but the material of gears has always been a headache. Sometimes we have to import materials from abroad. Therefore, there is still much work to be done in the smelting of materials in China. This is a good sign for the traction locomotive traction gear whose outer diameter of the driven gear is strictly limited by the railway line boundary, because the gear selection range of the driven gear becomes larger as the gear modulus decreases, which can be further increased. The large transmission ratio makes the technical use of the superior characteristics of the further use of the AC motor. The specific value of the modulus of the gear has standard requirements, but in the specific design, due to many factors, non-standard modulus values ​​can also be used. The result of this value is the ordering and production belt of the metal cutting tool of the gear. Come to a certain difficulty.
The pressure angle of the traction gear is generally 20° for the traction gear of the railway locomotive. The pressure angle of the traction gear of the early domestic locomotive Dongfeng series and the Laoshan 1 locomotive is 20°, and the pressure angle of the traction gear of the foreign locomotive is 20°. Not uncommon, there are other options, such as ND2, ND3 locomotive traction gear to choose 15 °. With the development of railway transportation to high speed and heavy load, in order to ensure the bending strength of the wheel gear, there is a tendency to adopt a large pressure angle direction, such as Dongfeng 11 locomotive, Dongfeng 4D locomotive, Dongfeng 11G locomotive, and the pressure angle of the traction gear. Developed to 22.5° or 25°. This is also the case in foreign countries, such as the DN5 locomotive, and the designer of the Japanese locomotive traction gear, the pressure angle of the gear is also 26°. Increasing the pressure angle of the gear can increase the bending strength of the gear and increase the load carrying capacity of the traction gear. However, as long as the contact strength of the gear is roughly calculated, it is found that increasing the pressure angle of the gear will sacrifice the contact strength of the partial gear. Therefore, according to the different conditions of the use of the locomotive, comprehensive consideration and reasonable selection of the traction gear pressure angle. Number of teeth of the traction gear When designing the traction gear, first pay attention to the problems of structure, strength, stiffness and lubrication, and then calculate and check the parameters such as root strength, contact stress, tooth surface slip, wear and gluing, etc. Pay attention to processing technology and heat treatment. The choice of the number of teeth of the gear does not seem to pay much attention. Generally speaking, the maximum speed nmax of the traction motor is given by the overall design; the traction gear ratio i is also determined by the overall design of the locomotive; the number of teeth z1 and z2 of the traction main and driven gears is gradually approached by the gear ratio i. And consider the possibility of design, structure and processing. Modification of the traction gear The proper modification of the traction gear of the locomotive is a powerful measure to improve its bearing capacity and reliability. In the traction gear of the railway locomotive, most of the driving gear and the electric shaft are directly connected by taper, and the single-side gear transmission is adopted, and the support is in the form of a cantilever, and the gear is outside the support point of the two points. Since the load of the traction gear and the meshing skew are larger than that of the double-side gear transmission, the tooth orientation is not modified, and the spiral drum shape correction is necessary. In the design of the traction gears of the early locomotives, the load speed was not high due to the small load, and the tooth orientation modification has not received much attention.

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