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一、问题的提出 进、排气门长期在高温燃气腐蚀和反复冲击负荷恶劣的条件下工作。随着汽车生产的日益发展和发动机性能的不断提高,应用部门对气门提出了愈来愈高的技术要求。例如:抗腐蚀能力、机械强度、生产成本等。 气门采用电镦锻压工艺,在通电加热电镦过程中不易控制工件的温度;各部位的温度不均匀;与砧块接触部温度低;颈部温度高;易产生折叠;电源电压的波动;液压系统的压力及电镦速度都会影响气门电镦质量。 1.晶粒组织对室温和高温机械性能的影响
First, the problem put forward, exhaust valve long-term high temperature gas corrosion and repeated shock load conditions work under harsh conditions. With the continuous development of automobile production and continuous improvement of engine performance, the application department has put forward higher and higher technical requirements on the valve. For example: corrosion resistance, mechanical strength, production costs. The valve adopts upset forging process, which is not easy to control the temperature of the workpiece in the process of electric heating upsetting; the temperature of each part is not uniform; the temperature at the contact part with the anvil block is low; the temperature of the neck is high; the folding is liable to occur; the fluctuation of the power supply voltage; System pressure and electrical upsetting speed will affect the quality of valve electrical upsetting. 1. The effect of grain structure on the mechanical properties at room temperature and high temperature