近年来,由于国内汽油机和柴油机已向高速、大功率和高性能方向发展,从而对排气阀的热负荷和使用寿命提出了新的要求。原来采用4Cr9Si2、4Cr10Si2Mo等材料制成的排气阀,由于经常发生早期磨损、腐蚀和阀头断裂的现象,严重影响发动机性能的提高,甚至导致发动机被破坏,已不能满足用户的使用要求。因此,试验和使用“21-4N”制阀工作已成为改进和发展内燃机的必要措施之一。 In recent years, as the domestic gasoline engine and diesel engine have been to high-speed, high-power and high performance direction, thus the thermal valve exhaust valve life and put forward new requirements. The original use of 4Cr9Si2, 4Cr10Si2Mo and other materials made of exhaust valve, due to the frequent occurrence of early wear and tear, corrosion and valve rupture phenomenon, seriously affecting the performance of the engine to improve, and even lead to engine damage, can no longer meet the user's requirements. Therefore, testing and using the “21-4N” valve has become one of the necessary measures to improve and develop the internal combustion engine.