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目前汽车发动机气门都已广泛采用了55X20Γ9AH_4（0.5～0.6％C;8～10％Mn;20～22％Cr; 3.5～4.5％Ni;0.3～0.6％N, ΓOCT5632-72）耐热奥氏体钢制造。它的使用寿命,以其发动机燃烧时高温持久强度和抗腐蚀性能及在规定的工作温度（65O～800℃）下硬度和塑性等性能来考核。气门在使用过程中,气门钢必须具有综合性能以满足发动机工作的可靠性。要达到这个要求,气门钢除要求一定的化学成份外,还必须要采取适宜的热处理工艺, 55X 20Γ9AH_4的不同热处理规范,使气门具有不同的机械性能。晶粒的大小,第一次和第二次析出的碳化物的大小、形状和分布对55X 20Γ9AH_4的性能影响极大。气门经1180～1190℃高温固溶,立即在760～780℃ 下时效处理13～16小时,再
At present, automobile engine valves have been widely used in 55X20Γ9AH_4 (0.5-0.6% C; 8-10% Mn; 20-22% Cr; 3.5-4.5% Ni; 0.3-0.6% N; ΓOCT5632-72) Steel manufacturing. Its service life, with its high temperature combustion engine combustion strength and corrosion resistance and the specified operating temperature (65O ~ 800 ℃) hardness and plastic properties to assess. Valve in use, the valve steel must have a comprehensive performance to meet the reliability of the engine. To achieve this requirement, in addition to requiring certain chemical composition valve steel, but also must take appropriate heat treatment process, 55X 20Γ9AH_4 different heat treatment specifications, the valve has different mechanical properties. The size of the grains, the size and shape of the first and second precipitated carbides greatly influence the performance of 55X20Γ9AH_4. Valve by 1180 ~ 1190 ℃ high temperature solution, immediately after aging at 760 ~ 780 ℃ for 13 to 16 hours, and then