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“本质晶粒度”是我国航空工业部门用以控制钢材质量的重要指标之一,是检验奥氏体晶粒长大倾向的一种方法。1 978年,改用晶粒边界腐蚀法检验“本质晶粒度”以来,暴露了不少钢种具有不同程度的混晶现象,导致钢材合格率大幅度下降。两年多来,冶金工业部和航空工业部有关单位作了大量试验研究工作,明确了控制晶粒粗化温度的三大技术措施:(1)控制残余铝含量,改善冶炼工艺;(2)控制形变温度及变形量;(3)选择适宜的予处理制度。本文选用铝、氮元素处于佳值范围的40CrNiMoA钢进行热加工对奥氏体晶粒度影响的研究,并选择合适的予处理制度控制AlN相呈弥散态分布,从而提高“本质晶粒度”的合格率。
“Intrinsic grain size ” is one of the important indicators used by China’s aviation industry to control the quality of steel. It is a method to test the tendency of austenite grain growth. In 1978, the use of grain boundary corrosion test instead of “intrinsic grain size ” has revealed that many types of steel with different degrees of mixed crystal phenomenon, resulting in a substantial decline in the passing rate of steel. Over the past two years, the Ministry of Metallurgical Industry and the relevant departments of the Ministry of Aeronautics have done a great deal of experimental research and clarified three major technical measures to control the grain coarsening temperature: (1) controlling the residual aluminum content and improving the smelting process; (2) Control of deformation temperature and deformation; (3) Select the appropriate pre-treatment system. In this paper, aluminum and nitrogen elements in the good value range of 40CrNiMoA steel for the austenite grain size of the impact of heat treatment, and select the appropriate pretreatment control AlN dispersed state, thereby increasing the “intrinsic grain size ”Pass rate.