Helical cylindrical gear is an important transmission part widely used in automobile and machinery industry. Its shape is complex, and its dimensional accuracy, surface quality and comprehensive mechanical properties are highly required. At present, the current technology at home and abroad produces this type of spiral cylindrical gear by rough forging first, and then cutting and finishing the tooth shape. In the current process, the metal fiber structure is cut off by cutting, which reduces the strength of helical cylindrical gear, has low material utilization rate and high energy and man hour consumption. Closed die forging process can overcome the shortcomings of traditional process. Warm forging is easier to form than cold forging due to its small deformation resistance and good material plasticity. On the other hand, compared with hot forging, warm forging has better dimensional accuracy and surface quality due to lower heating temperature, reduced oxidation and decarburization. Therefore, closed die forging warm formed parts have high dimensional accuracy and surface quality Good mechanical properties.
(1) The spiral cylindrical gear of automobile gearbox is formed by closed die forging. Compared with the traditional production process, it can reduce working hours and energy consumption. The spiral cylindrical gear forging has high surface quality and good mechanical properties.
(2) The closed die forging of helical cylindrical gear adopts two kinds of blanks, one is the blank with boss and the other is the round bar blank. Compared with the blank with boss, the round bar blank is easy to process and saves materials. Through the numerical simulation analysis, it is found that the forming of the two billets is roughly the same. Due to the large strain value, the corresponding load is also slightly larger than that of the blank with boss. When the blank of helical cylindrical gear is filled into the tooth cavity, the equivalent stress and equivalent effect at the tooth root become larger. In the final filling stage, the equivalent stress of tooth ejection becomes larger.
(3) From the load stroke curve, the closed die forging of helical cylindrical gear can be divided into three stages: rough forging stage, tooth cavity filling forming stage and final filling stage. In the final filling stage, in order to overcome the hydrostatic pressure generated by the metal at rest, the working load increases sharply.