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钢的晶粒尺寸的大小不仅对热处理工艺有影响,而且对钢的许多使用性能有影响。因此测定A体晶粒度已成为评定钢材质量的重要检验项目之一。正确地规定晶粒度标准不仅涉及到钢材的生产和使用,也涉及到经不同热处理后钢件的安全使用等问题。因此,规定A体晶粒度标准时必须考虑钢件的热处理工艺、晶粒度与使用性能之间的内在联系以及合理的评定方法。可是,YB27-77晶粒度标准在这些基本问题上存在着缺点和错误。 YB27-77中规定:“若试样中发现有晶粒不均匀现象时……占优势晶粒所有的面积不少于视场的90％”。对细晶钢中的“混晶”
The size of the steel grain size not only affect the heat treatment process, but also affect the performance of many steel. Therefore, the determination of A grain size has become one of the important test items to evaluate the quality of steel. Correctly stipulating the grain size standard not only involves the production and use of steel, but also involves such issues as the safe use of steel after different heat treatments. Therefore, the provisions of A-body grain size standards must consider the heat treatment process, the relationship between grain size and the use of performance and a reasonable assessment method. However, YB27-77 grain size standards in these basic problems there are flaws and mistakes. YB27-77 states: “If the sample is found to have uneven grain ... ... all the dominant grain area of not less than 90% of the field of view.” Fine grain of steel in the “mixed crystal”