近年来,国内外电站频繁发生发电机护环开裂并造成设备损坏的事故。因此,在不拆卸护环的条件下检出内壁微裂纹是防止护环开裂的重要手段。能否不拆卸作金属探伤关健在于准确测定被测部位的晶粒度级别。根据晶粒度尺寸,决定探头的频率、晶片尺寸与裂纹深度的检出范围。由奥氏体钢制成的护环多为粗晶钢,粗 In recent years, accidents of generator guard ring cracking and equipment damage occur frequently in domestic and foreign power stations. Therefore, without removing the retaining ring detection of the inner wall of the microcracking is an important means to prevent cracking ring. Can not disassemble the key for metal detection lies in the accurate determination of the grain size of the measured site level. According to the grain size, determine the probe frequency, chip size and crack depth detection range. Ring made of austenitic steel mostly coarse-grained steel, coarse