Die Cast Dies Design For Semi-solid Rheo-Extrusion Technique And Study On The Process Properties Of Gear Of Tachometer

With the development of the railway transportation towards high speed and over loading, the service conditions of engine vehicles were becoming much worse. Common carbon steel castings were unable to satisfy the higher requirements at present, which were replaced by low alloy material parts gradually. When carbon steel castings were replaced by low alloy material, a series of questions were discovered in traditional sand casting process. In order to solve the questions discovered, semi-solid rheological squeeze casting technique was put forward as the forming method for manufacturing gear of tachometer of engine vehicle in this paper firstly. In the study, 7075 alloy instead of common carbon steel, which is the common material for gear of tachometer of engine vehicle, was adopted as the researching material. Gear of tachometer and property samples obtained through semi-solid rheological squeeze casting were used as experiment examples. The technique was studied systemically through experiments and theories in the following aspects, where were preparation of the semi-solid slurry, control of the quality and structure of the formed parts etc.Nondendritic-structure slurry that suitable for semisolid rheological squeeze casting was obtained through Inclined Slope Pre-crystallization Method, and characteristics of the nondendritic-structure slurry were analyzed quantitatively by the average equal-area-circle diameter, and the suitable process parameters were obtained: the inclined slope length and angle are 400mm,60°. Under these processing parameters, the average equal-area-circle diameter of the 7075 alloy nondendritic-structure was 40.5μm. Qualities of the 7075 alloy casts formed by semisolid rheological squeeze casting process were studied through examples of gear of tachometer casts, and the study was done under the most suitable processing parameters mentioned above. The results revealed were as: the suitable processing parameters were critical factors to gain the advantages of semi-solid rheological squeeze casting process. If improper processing parameters were chosen in a semi-solid rheological squeeze casting process, cold laps were engendered easily on the surfaces of the formed parts, gas holes were formed easily. When preheating temperature of the die was 180-220℃, stripping angle of the punch was 1 , the forming pressure was 61.9MPa and the holding time was 5 s, favorable gear of tachometer with excellent inner and outer quality were obtained. In the optimal technical parameters, the simulation of gear of tachometer has been done by software ProCAST and Ansys. It revealed that the result of simulation is consistent with the experiment.