(1) Forging material
The forming metal material selected for the driven spiral bevel gear of automobile rear axle is a kind of carburized steel with the brand of 20mncr5. It has the characteristics of high strength, good toughness, good hardenability, small quenching deformation, good low-temperature toughness and good machinability. It is generally used after carburizing, quenching or quenching and tempering.
(2) Part shape
The two-dimensional and three-dimensional mathematical models of the driven spiral bevel gear of the automobile rear axle studied in this paper are shown in the figure. Its shape is conical, like an umbrella, and its teeth are distributed in spiral lines, so it is called spiral bevel gear. For the shape of spiral bevel gear, because it has a certain taper and takes the section with the largest cross section as the parting surface, the cavities of the upper die and the lower die are inclined, so it is easy to realize the die out.
(3) Dimensional accuracy and surface quality of forgings
Compared with traditional processing methods, open die forging has many advantages, such as improving material utilization, improving forging accuracy, saving production processes, reducing energy consumption and improving mechanical properties of forgings. The basic processing method of the driven spiral bevel gear of the automobile rear axle studied in this paper is still based on machining the tooth shape. The more common processing methods are gear hobbing, gear shaping, gear milling, gear grinding and gear shaving. The gear accuracy processed by this kind of modern NC machining machine tool is it7, that is to say, as long as the machining accuracy of the forging reaches it7, it can meet the accuracy requirements of the spiral bevel gear. There are many factors affecting the dimensional accuracy and surface roughness of forgings, and the dimensional accuracy of forgings is generally one or two levels lower than that of die bore. In terms of accuracy, with the increasing maturity of modern NC machining technology, molds with dimensional accuracy of it5 ~ 6 can be manufactured, and the accuracy of forgings can reach IT6 ~ 7, which can meet the industrial requirements. For surface roughness, there are two main methods of tooth surface finish machining of spiral bevel gear: gear grinding and gear grinding. As a traditional process method, gear lapping has high production efficiency, which can change the roughness and contact position of the effective tooth surface and slightly correct the tooth profile error; Gear grinding technology can obtain high machining accuracy, so it is generally used for the machining of gears with high requirements.
(4) Production batch
Since the end of last century, China’s automobile industry has developed vigorously. Now, the automobile industry has developed rapidly into China’s pillar industry. It is expected that China’s annual automobile output will increase significantly in the next ten years. With the development of science and technology and the progress of the times, cars have entered thousands of households, from a luxury of social life – a symbol of identity to a necessity of modern life – a means of transportation. The automobile industry has entered the era of mass automobile consumption. The rapid development of the automobile industry drives the rapid development of all automobile related industries. As the main transmission part of the main reducer of the automobile rear axle, the demand for the driven spiral bevel gear of the automobile rear axle is increasing day by day. With the increasing demand for spiral bevel gears, the improvement of quality standards and the control of processing costs, innovative production processes are required to meet this market demand. Therefore, the precision forging process of spiral bevel gears has also become one of the research directions of the whole automobile industry. At the same time, because the spiral bevel gear has the advantages of strong bearing capacity and stable transmission, it is also widely used in machine tools, ships, aerospace and other fields. Therefore, the spiral bevel gear has great development space and huge market potential. Using precision forging process to process spiral bevel gear for mass production can save cost and improve efficiency, and has a great development prospect.