1.1 This standard specifies the expression and rating methods of average grain size of metal structure. These methods may also be applicable to nonmetallic materials with grain shape similar to the series of rating picture in this standard. These methods are mainly applicable to single-phase grain structures, but after specific provisions, they may also be applicable to the measurement of average size for specific type of grain in multi-phase or multicomponent specimens.
1.2 This standard is to determine the average grain size of the specimen through unimodal distribution of grain area, grain diameter and section line length. Such distribution is approximate to normal distribution. The determination method of this standard is not applicable to grain size with bimodal distribution.
1.3 The measuring method of this standard is only applicable to the measurement of horizontal grain size, i.e. two-dimensional grain indicated on the specimen section, but not applicable to three-dimentional grain of the specimen, i.e. measurement of three-dimentional grain size.
1.4 This standard is only taken as a recommended test method and can not determine whether the tested material is received or determine the suitable use scope.
