ISO 643:2019 pdf download

ISO 643:2019 pdf download.Steels-Micrographic determination of the apparent grain size.
1 Scope
ISO 643 specifies a micrographic method of determining apparent ferritic or austenitic grain size in steels. It describes the methods of revealing grain boundaries and of estimating the mean grain size of specimens with unirnodal size distribution. Although grains are three-dimensional in shape, the metallographic sectioning plane can cut through a grain at any point from a grain corner, to the maximum diameter of the grain, thus producing a range of apparent grain sizes on the two-dimensional plane, even in a sample with a perfectly consistent grain size.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ASTM E112, Standard Test Methods for Determining Average Grain Size
The grain size is revealed by micrographic examination of a polished section of the specimen prepare by an appropriate method for the type of steel and for the information sought.
NOTE If the order or the International Standard defining the product does not stipulate the method o revealing the grain, the choice of this method is left to the manufacturer.
This average size is characterized either
a) byanindexobtained
1) usually by comparison with standard charts for the measurement of grain size;
2) or by counting to determine the average number of grains per unit area; b) or by the mean value of the intercepted segment.
Ifthe order, or the International Standard defining the product, does not specify the number of specimens and the point at which they are to be taken from the product, these are left to the manufacturer, although it has been shown that precision of grain size determination increases the higher the number of specimens assessed. Therefore, it is recommended that two or more sections be assessed. Care shall be taken to ensure that the specimens are representative of the bulk of the product (i.e. avoid heavily deformed material such as that found at the extreme end of certain products or where shearing has been used to remove the specimen, etc.). The specimens shall be polished in accordance with the usual methods.
Unless otherwise stated by the product standard or by agreement with the customer, the polished face of the specimen shall be longitudinal, i.e. parallel to the principal axis of deformation in wrought products. Measurements of the grain size on a transverse plane will be biased if the grain shape is not equlaxial.ISO-643-2019

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