International ISO 4 Standard IS0 643 Steels Micrographic determination Fifth edition of the apparent grain size 2024-08 Aciers - Deétermination micrographique de la grosseur de grain apparente Reference number IS0643:2024(en) @ ISO 2024 IS0 643:2024(en) COPYRIGHTPROTECTEDDOCUMENT IS02024 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may the internet or an intranet, without prior written permission. Permission can be requested from either IsO at the address below or ISo's member body in the country of the requester. ISO copyright office CP 401 : Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +41 22 749 01 11 Email: copyright@iso.org Website: www.iso.org Published in Switzerland @ IS0 2024 - All rights reserved ii IS0 643:2024(en) Contents Page Foreword. .iv 1 Scope .1 2 Normative references .1 3 Terms and definitions .1 3.1 Grains. ..1 3.2 General ..2 4 Symbols. .2 5 Principle. ..3 6 Selection and preparation of the specimen .5 6.1 Testlocation ..5 6.2 Revealing ferritic grain boundaries ..5 6.3 Revealing austenitic and prior-austenitic grain boundaries. .5 6.3.1 General. .5 7 Characterization of grain size .6 7.1 General ..6 7.1.1 Characterization methods .6 7.1.2 Formulae 7.1.3 Accuracy of the methods .6 7.2 Comparison method .6 7.3 Planimetric method 7.4 Intercept method. 13 7.4.1 General 13 7.4.2 Linear intercept method .14 7.4.3 Circular intercept method 15 7.4.4 Assessmentofresults 15 7.5 Other methods. .16 8 Test report 17 Annex A (informative) Methods for revealing austenitic or prior-austenitic grain boundaries in steels .18 Annex B (normative) Determination of grain size with standard comparison charts .23 Annex C (informative) Evaluation method .35 Annex D (informative) Calculation of grain size and confidence interval .37 Annex E (informative) Grains of different size indices. .40 Bibliography .46 @ IS0 2024 - All rights reserved iii