Standard No.:	GB/T 34474-2025
English Name:	Methods for determination of banded structure of steels
Chinese Name:	钢中带状组织的评定方法
Chinese Classification:	H24    Metallographic testing method
Professional Classification:	GB    National Standard
ICS Classification:	77.040.99 77.040.99    Other methods of testing of metals 77.040.99
Source Content Issued by:	SAMR; SAC
Issued on:	2025-08-29
Implemented on:	2026-3-1
Status:	valid
Superseding:	GB/T 34474.1-2017 Determination of banded structure of steel-Part 1:Micrographic method using standards diagrams GB/T 34474.2-2018 Determination of banded structure of steel—Part 2:Quantitative method
Target Language:	English
File Format:	PDF
Word Count:	21000 words
Translation Price(USD):	630.0
Delivery:	via email in 1 business day

GB/T 34474-2025 Methods for determination of banded structure of steels 1 Scope This document describes three methods for determination of banded structure of steels: micrographic method using standards diagrams, quantitative method, and hardness method. It covers the method overview, equipment, sampling, specimen preparation, determination methods, inspection results, and inspection reports. This document is applicable to the inspection and determination of banded structure of steels that have undergone plastic deformation. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies. GB/T 225 Steel - Hardenability test by end quenching (Jominy test) GB/T 4340.1 Metallic materials - Vickers hardness test - Part 1: Test method GB/T 13298 Inspection methods of microstructure for metals GB/T 15749 Measuring method in quantitative metallography GB/T 18449.1 Metallic materials - Knoop hardness test - Part 1: Test method GB/T 30067 Standard terminology relating to metallography GB/T 33362-2016 Metallic materials - Conversion of hardness values 3 Terms and definitions For the purposes of this document, the terms and definitions given in GB/T 30067 and the following apply. 3.1 banded structure alternating structure banding parallel to the processing direction, formed by the deformation-induced elongation of segregation zones during processing 3.2 class II structure banding banding composed of single or multiple structures (except ferrite), including pearlite, bainite, martensite, and other non-equilibrium structures Note: When determined with the micrographic method using standard diagrams, class II structure banding shall be rated as a whole as a structure class. 3.3 continuous banding structure banding of the same class appearing in a field of view, wherein, grains are separated only by grain boundaries, and no structure of other class appears 4 Symbols The following symbols and descriptions apply to this document (see Table 1). Table 1 Symbols and descriptions Symbol Description Equation Unit AI Anisotropy index of the field of view — AI Anisotropy index of the specimen, average of AI of n fields of view — B Bandwidth, evaluated as the difference between the average spacing of the bands and the average free path mm BR Banding ratio of the field of view — BR Banding ratio of the specimen, average of BR of n fields of view — e Shape ratio of banded structure, ratio of the average transverse interception length to the average longitudinal interception length — k Number of measurement lines perpendicular to the deformation direction — Pcs k95% Coverage factor, used together with standard deviation to determine the expanded uncertainty with a coverage probability of 95% — — L Length of measurement line — mm Lt True length of measurement line, i.e., the length of measurement line divided by magnification M mm Lt// True total length of all measurement lines perpendicular to the deformation direction mm Lt⊥ True total length of all measurement lines parallel to the deformation direction mm Ltd⊥ True length of a single measurement line perpendicular to the deformation direction — — Ltd// True length of a single measurement line parallel to the deformation direction — — l Interception of the feature — mm l⊥ Sum of intercepts of all features on a single measurement line perpendicular to the deformation direction within a field of view mm l// Sum of intercepts of all features on a single measurement line parallel to the deformation direction within a field of view mm lL⊥ Characteristic linear fraction in the perpendicular direction, i.e., the ratio of the sum of feature interceptions on a single measurement line perpendicular to the deformation direction to the line length within a field of view — lL// Characteristic linear fraction in the parallel direction, i.e., the ratio of the sum of feature interceptions on a single measurement line parallel to the deformation direction to the line length within a field of view — M Magnification — — m Number of measurement lines parallel to the deformation direction — Pcs N⊥ Sum of transversal count perpendicular to the deformation direction within a field of view — Pcs N// Sum of transversal count parallel to the deformation direction within a field of view — Pcs NL⊥ Transversal count per unit length perpendicular to the deformation direction Pcs/mm NL// Transversal count per unit length parallel to the deformation direction NL//=N//Lt// Pcs/mm NL⊥ Average of the transversal count perpendicular to the deformation direction of n fields of view Pcs/mm NL// Average of the transversal count parallel to the deformation direction of n fields of view Pcs/mm n Number of inspected fields of view — Pcs P⊥ Sum of all intersection counts perpendicular to the deformation direction within a field of view — Pcs P// Sum of all intersection counts parallel to the deformation direction within a field of view — Pcs PL⊥ Intersection count per unit length perpendicular to the deformation direction Pcs/mm

Contents Foreword i 1 Scope 2 Normative references 3 Terms and definitions 4 Symbols 5 Method overview 6 Equipment 7 Sampling 8 Specimen preparation 9 Determination methods 10 Inspection results 11 Inspection report Annex A (Normative) Standard rating diagrams Annex B (Normative) Calculation of expanded uncertainty and relative expanded uncertainty Annex C (Normative) Simplified algorithms for characteristic parameters Annex D (Informative) Example for determination of characteristic parameters of banded structure Annex E (Informative) Examples of characteristic parameters for different types of structures Annex F (Informative) Example of banding determination results by hardness method Annex G (Informative) Conversion from Knoop hardness HK to Rockwell hardness HRC Annex H (Informative) Prediction of carbon content from quenched hardness