ISO 643-2012 pdf free download.Steels一Micrographic determination of the apparent grain size. ISO 643 specifies a micrographic method of determining apparent ferntic or austenitic grain size in steels. It describes the methods of revealing grain boundaries and of estimating the mean grain size of specimens with unimodal 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 referenced documents are indispensable for the application 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. ISO 3785, Steel — Designation of test piece axes ISO 14250, Steel — Metallographic characterization of duplex grain size and distributions ASTM El 12, Standard Test Methods for Determining Average Grain Size 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 4 Symbols and abbreviated terms The symbols used are given in Table 1. 5 Principle The…

ISO 643-2019 pdf free.Steels一Micrographic determination of the apparent grain size. 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 equiaxial. 6.2 Revealing ferritic grain boundaries The ferritic grains shall be revealed by etching with nital (ethanolic 2 % to 3 % nitric acid solution), or with an appropriate reagent. 6.3 Revealing austenitic and prior-austenitic grain boundaries 6.3.1 General In the case of steels having a single-phase or two-phase austenitic structure (delta ferrite grains In an austenitic matrix) at ambient temperature, the grain shall be revealed by an etching solution. For single phase austenitic stainless steels, the most commonly used chemical etchants are glyceregia, Kalling’s reagent (No. 2) and Marbles reagent. The best electrolytic etch for single or two-phase stainless steels is aqueous 60 % nitric acid at 1,4 V d.c. for 60 s to 120 s, as it reveals the grain boundaries but not the twin boundaries. Aqueous 10 % oxalic acid, 6 V d.c., up to 60…