The study on the cooling strategy of punch dies under hot compound extrusion of critical components of trains

Train critical components play an important role in ensuring the safety and high-speed running of trains. Failure of critical components will affect the normal operation of trains, or even cause serious accidents, resulting in economic losses, the manufacturing process of which is important to ensure life and reliability of trains. Especially, the design and manufacture of large, complex, and precise punch die is the critical technology for the manufacture of train components. In the process of extrusion, the die of the punch is at high temperature, which has a bad influence on the processing accuracy and reliability of train components. Also, hot compound deformation due to long punch stroke will reduce the life of punch die, which can increase the train manufacturing costs. Therefore, ensuring the cooling of the punch die timely is important to ensure the machining accuracy. In this study, a cooling strategy of punch die under hot compound extrusion of critical components of the trains is proposed. A numerical simulation of the cooling process of critical components of the trains is carried out to assist the optimization design of the extrusion die, and the extrusion process parameters are adjusted to cooling temperature and rate of the die. Firstly, the theoretical temperature rise of the punch die is carried out. Then, the formula of the temperature rises and cooling of the punch are obtained. Secondly, according to the forced convective heat transfer of cooling water, we calculate the convective heat transfer coefficients on the surface of the cooling pipe. Meanwhile, the interior and external heat dissipation of punch is simulated by finite element simulation. Thirdly, production beat and parameters of compound extrusion is calculated. On this basis, we design and develop a piece of interior circulation cooling cycle equipment. Finally, an example of an engineering experiment is given. The variations of the temperature field distribution are obtained after the punch extrusion and heat dissipation through the infrared temperature measuring equipment. The experiment results agree with the theoretical ones.