In 1985, the 59th Institute of ordnance industry successfully used the cold rotary forging process to realize the cold forming of end tooth profile for the first time in China.
As shown in the figure, the developed parts are end gears for motorcycle starting mechanism. The material is 15CrMo or 20CrMo. The main technical difficulty is to form thirty equal teeth along the circumference of the outer ring of the boss on the end face of the rotary forging part. The tooth depth is 0.9mm. The fillet of tooth top and tooth bottom is R 02- R 04 。 Because there is no undercut between the end face boss and the tooth profile of the outer ring, it is impossible to cut and process, and the cold swing rolling process is adopted to form the end face teeth. The success of cold rotary forging of this part is the first precedent for large-scale forming of tooth shaped precision parts by cold rotary forging in China.
In 1986, Wuhan Institute of technology began to study the warm rotary forging process of differential planetary powder metallurgy bevel gear of automobile rear axle. Dry swing rolling is a local continuous forming, and the position of the plastic deformation area is constantly moving, that is, the boundary of the plastic deformation area moves in the deformation body, which makes each part of the deformation body deform for many times under the repeated action of shear stress, which is equivalent to the continuous destruction and compaction of each pore of the powder metallurgy porous body. Therefore, swing rolling can densify the powder metallurgy porous body better than general forging.
In 1988, the 59th Institute of ordnance industry cooperated with Xi’an Jiaotong University to study the cold rotary forging of planetary bevel gears. The influence of swing head shape, swing head trajectory, swing rolling time, feed rate and blank shape on the filling degree of bevel gear tooth shape is studied, and the forming force of cold swing rolling and metal flow during photoplastic simulation swing rolling are calculated.
In 1989, China uses cold rotary forging process to produce spiral bevel gears. Compared with the straight bevel gear, the spiral bevel gear has stable transmission, low impact, low noise and large bearing capacity, but it is difficult to process and high cost. The spiral bevel gear with modulus less than 3 is generally processed by Gleason machine tool in China. The success of cold rotary rolling of “small screw umbrella” has greatly improved the machining technology level of this kind of products in China.
In 1992, the motorcycle starting ratchet with “ears” was successfully rolled by cold swing rolling, as shown in the figure. The technical difficulty of the part is that there is an irregular small boss called “ear” on the outer circumference of the gear. It is difficult to form by using the traditional forging process, and the cutting process is labor-consuming and time-consuming. Therefore, the cold swing rolling process is adopted. After many tests and careful design of the mold, it was successful. The formed parts have high precision and good interchangeability. Because the metal streamline is continuous, the deformation of the tooth shape during heat treatment is small. Work hardening during rotary forging improves the comprehensive mechanical performance of the tooth profile part. Its wear resistance and service life are improved.
In 1995, China introduced Swiss technology and rotary forging machine to produce differential planetary bevel gears with modulus less than 4 for micro cars.
In 1997, the 59th Institute of ordnance industry succeeded in cold rotary rolling. One side has end face tooth shape and the other side is spiral part. In recent years, the research on rotary forging in China has made great progress. According to the statistics of the 5th China rotary forging academic conference, China has 56 rotary forging machines for forging production. So far, China has been able to produce automobile rear half shaft, large-diameter thin-walled disc flange, brass gong, speaker magnet, end gear, various gear blanks and various thin-walled disc and cake forgings by swing rolling process. The cold rotary forging production of automotive planetary bevel gear, rear axle driven gear, half shaft bevel gear and steel synchronizer ring is still in the trial production stage. In addition, the development of rotary forging and riveting technology provides a new application field for rotary forging and riveting technology. At present, hundreds of rotary forging and riveting machines in China are in normal operation.