Detail of GB/T 3488.2-2018

Introduction of GB/T 3488.2-2018

GB/T 3488.2-2018 Hardmetals - Metallographic determination of microstructure - Part 2 : Measurement of WC grain size 1 Scope This part of GB/T 3488 gives guidelines for the measurement of hardmetal grain size by metallographic techniques using optical or electron microscopy. It is intended for sintered WC/Co hardmetals (also called cemented carbides or cermets) containing primarily WC as the hard phase. It is also intended for measuring the grain size and distribution by the linear-intercept technique. This part essentially covers four main topics: ——calibration of microscopes, to underpin the accuracy of measurements; ——linear analysis techniques, to acquire sufficient statistically meaningful data; ——analysis methods, to calculate representative average values; ——reporting, to comply with modern quality requirements. The part is supported by a measurement case study to illustrate the recommended techniques (see Annex A). The part is not intended for the following: ——Measurements of size distribution; ——Recommendations on shape measurements. Further research is needed before recommendations for shape measurement can be given. Measurements of coercivity are sometimes used for grain-size measurement, but this method is concerned only with a metallographic measurement method. It is applicable to sintered hardmetals, but not to powders. However, the method could, in principle, be used for measuring the average size of powders that are suitably mounted and sectioned. 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 3326 Hardmetals - Determination of (the magnetization) coercivity ISO 3369 Impermeable sintered metal materials and hardmetals - Determination of density ISO 3738-1 Hardmetals - Rockwell hardness test (scale A) - Part 1 : Test method ISO 3738-2 Hardmetals - Rockwell hardness test (scale A) - Part 2 : Preparation and calibration of standard test blocks ISO 3878 Hardmetals - Vickers hardness test ISO 4489 : 1978 Sintered hardmetals - Sampling and testing ISO 4499-1 Hardmetals - Metallographic determination of microstructure - Part 1 : Photomicrographs and description ISO 4505 Hardmetals - Metallographic determination of porosity and uncombined carbon 3 Terms, definitions, abbreviations, symbols and units 3.1 General A very wide range of terms are used to describe powders or sintered hardmetals of different sizes. For example, the following have been used in a variety of publications and reports. Nanograin Nanograin Nanophase Micrograin Microfine Submicron Ultra fine Extra fine Very fine Fine Medium/Fine Medium Medium/Coarse Coarse Extra coarse None of these terms have commonly agreed or well-defined size ranges among users and producers of powders or sintered products. Consequently, following discussion in the hardmetal community, the following terms for the sizes defined in 3.2 are recommended. The uncertainty associated with the measurement of linear-intercept grain size is about 10 %, if typically 200 grains to 300 grains are counted. Thus, measurements on or close to the class boundaries shall be treated carefully. It is recommended that measurements that fall within 10 % of any of the class boundaries should be classed as follows: Example: 0.19μm as Nano/Ultrafine 0.21μm as UItrafine/Nano 0.75μm as Submicron/Fine 0.85μm as Fine/Submicron 1.29μm as Submicron/Fine 1.31μm as Medium/Fine 2.4μm as Medium/Coarse 2.6μm as Coarse/Medium 3.2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.2.1 nano with WC grain size < 0.2μm Note: measured by the mean-linear-intercept method described in this part. 3.2.2 ultrafine 0.2μm≤WC grain size<0.5μm Note: measured by the mean-linear-intercept method described in this part. 3.2.3 submicron 0.5μm≤WC grain size<0.8μm Note: measured by the mean-linear-intercept method described in this part. 3.2.4 fine 0.8μm≤WC grain size<1.3μm。 Note: measured by the mean-linear-intercept method described in this part. 3.2.5 medium 1.3μm≤WC grain size<2.5μm

Contents of GB/T 3488.2-2018

Foreword I 1 Scope 2 Normative references 3 Terms, definitions, abbreviations, symbols and units 4 General 5 Apparatus 6 Calibration 7 Grain-size measurement by the linear-intercept method 8 Reporting Annex A (Informative) Measurement case study Annex B (Informative) Report proforma Bibliography