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GB/T 34474-2025: Methods for determination of banded structure of steels
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GB/T 34474: Evolution and historical versions
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Methods for determination of banded structure of steels
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| GB/T 34474.1-2017 | English | 265 |
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Determination of Banded Structure of Steel - Part 1: Micrographic Method Using Standards Diagrams
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Basic data | Standard ID | GB/T 34474-2025 (GB/T34474-2025) | | Description (Translated English) | Methods for determination of banded structure of steels | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | H24 | | Classification of International Standard | 77.040.99 | | Word Count Estimation | 50,529 | | Date of Issue | 2025-08-29 | | Date of Implementation | 2026-03-01 | | Older Standard (superseded by this standard) | GB/T 34474.1-2017, GB/T 34474.2-2018 | | Issuing agency(ies) | State Administration for Market Regulation; Standardization Administration of China | GB/T 34474-2025: Methods for determination of banded structure of steels---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT34474-2025
ICS 77.040.99
CCSH24
National Standards of the People's Republic of China
Replaces GB/T 34474.1-2017 and GB/T 34474.2-2018
Evaluation method of banded structure in steel
Published on 2025-08-29
Implemented on 2026-03-01
State Administration for Market Regulation
The State Administration for Standardization issued a statement.
Table of Contents
Preface III
1.Scope 1
2 Normative References 1
3.Terms and Definitions 1
4 Symbols 1
5.Method Overview 4.
6 Equipment 4
7.Sampling 4
8 Sample Preparation 7
9.Assessment Methods 7.
10 Test Results 14
11 Inspection Report 14
Appendix A (Normative) Standard Rating Chart 15
Appendix B (Normative) Calculation of Expanded Uncertainty and Relative Expanded Uncertainty 24
Appendix C (Normative) Simplified Algorithm for Feature Parameters 26
Appendix D (Informative) Example 28 of the determination of characteristic parameters of banded tissue
Appendix E (Informative) Examples of Characteristic Parameters for Different Types of Tissues 33
Appendix F (Informative) Example 42 of Hardness Test Results for Bands
Appendix G (Informative) Conversion from Knoop Hardness (HK) to Rockwell Hardness (HRC) 43
Appendix H (Informative) Prediction of Quenching Hardness for Carbon Content 45
Foreword
This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1.Structure and Drafting Rules of Standardization Documents".
Drafting.
This document supersedes GB/T 34474.1-2017 "Assessment of banded structure in steel - Part 1.Standard rating chart method" and GB/T 34474.2-
The.2018 standard, "Evaluation of Banded Structures in Steel - Part 2.Quantitative Methods," compared to GB/T 34474.1-2017, includes structural adjustments and editorial modifications.
Aside from the changes, the main technical changes are as follows.
a) A hardness test has been added (see 7.3, 8.1, 8.2.3, 9.4);
b) A special examination method for banded tissue in use has been added (see 9.2.8);
c) A special examination method for extremely narrow band-like tissues has been added (see 9.2.9);
d) An isothermal annealing heat treatment was added to the specimens (see 8.1);
e) Added calculation methods for the anisotropy index AI and orientation degree Ω12 (see 9.3.2.2.8 and 9.3.2.2.9);
f) The determination of the band ratio BR parameter was added (see 9.3.2.2.11);
g) A method for calculating volume fraction VV has been added (see 9.3.2.2.13);
h) A method for calculating the morphological ratio e has been added (see 9.3.2.2.17);
i) Added a method for calculating the 95% uncertainty of the parameters anisotropy index AI, orientation degree Ω12, and banding ratio BR (see
Appendix B);
j) A simplified algorithm for the anisotropy index AI, orientation degree Ω12, and band ratio BR parameters has been added (see Appendix C).
Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.
This document was proposed by the China Iron and Steel Association.
This document is under the jurisdiction of the National Steel Standardization Technical Committee (SAC/TC183).
This document was drafted by. Fushun Special Steel Co., Ltd., Shougang Group Co., Ltd., Lianfeng Steel (Zhangjiagang) Co., Ltd., and other steel companies.
Research Institute Co., Ltd., Benxi Steel Plate Co., Ltd., Metallurgical Industry Information and Standardization Research Institute, Nanjing University of Aeronautics and Astronautics.
The main drafters of this document are. Cheng Lijie, Wen Juan, Cao Lihong, Ju Xinhua, Li Jikang, Yu Chao, Tian Yuwei, Wang Lin, Gu Qiang, Meng Yang, and Zhang Shasha.
Feng Changwei, Lai Ping, Shi Jiakai, Li Bibo, Hai Chao, Yan Chengming, Shu Changqing.
The document replaced by this document has been released in the following versions.
---GB/T 34474.1, first published in.2017;
---GB/T 34474.2, first published in.2018.
Evaluation method of banded structure in steel
1.Scope
This document describes three methods for assessing banded microstructure in steel. the standard rating chart method, the quantitative method, and the hardness method. It includes an overview of the methods, equipment, and sampling procedures.
Sample preparation, evaluation methods, test results, and test reports.
This document applies to the inspection and evaluation of banded structures in steel that has undergone plastic deformation.
2 Normative references
The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.
For references to documents, only the version dated [date] applies to this document; for undated references, the latest version (including all amendments) applies.
document.
GB/T 225 Steel - End-quenching test method for hardenability (Jominy test)
GB/T 4340.1 Metallic materials - Vickers hardness test - Part 1.Test method
GB/T 13298 Examination Methods for Metallic Microstructure
GB/T 15749 Quantitative Metallographic Determination Methods
GB/T 18449.1 Metallic materials - Knoop hardness test - Part 1.Test method
GB/T 30067 Metallographic Terminology
GB/T 33362-2016 Conversion of Hardness Values for Metallic Materials
3.Terms and Definitions
The terms and definitions defined in GB/T 30067 and the following terms and definitions apply to this document.
3.1
banded structure
During processing, alternating zones of tissue are formed parallel to the processing direction due to the deformation and elongation of the segregation zone.
3.2
Class II structure banding
Other tissues besides ferrite, including pearlite, bainite, martensite, and other non-equilibrium structures, either singly or in mixtures.
Note. In the standard rating chart method, the second category of organizations is included in the rating as a whole.
3.3
Continuous banding
The same type of structure band exists in the evaluation field of view, and the grains within the band are separated only by grain boundaries, with no other types of structure present.
4 symbols
The following symbols and explanations apply to this document (see Table 1).
Table 1 Symbols and Explanations
Symbol Explanation Formula Units
Anisotropy index of AI field of view
AI=
NL⊥
NL∥
AI=
PL⊥
PL∥
The anisotropy index of the AI specimen, the average AI value across n fields of view.
∑AI
B is the bandwidth, evaluated as the difference between the average strip spacing and the free path, B = SB⊥ - λ⊥ mm.
BR is the zonal ratio of the field of view.
sL∥
sL⊥
BR is the band ratio of the sample, and the average value of BR across n fields of view.
∑BR
The ratio of banded tissue shape, the transverse mean length of the intercept and the longitudinal mean length
Average length ratio
e=
∑lL∥/NL∥
∑lL⊥/NL⊥
k is the number of measurement lines perpendicular to the deformation direction.
k95%
Coverage factor, used together with standard deviation to determine the coverage probability of 95%.
Expanded uncertainty
- -
L - Length of measuring line (mm)
Lt
The true length of the measuring line, i.e., the length of the measuring line divided by the magnification factor.
Number M
Lt=
M mm
Lt∥ The true total length of all measurement lines perpendicular to the deformation direction, Lt⊥ = k·Ltd⊥ mm
Lt⊥ The true total length of all measurement lines parallel to the deformation direction, Lt∥ = m·Ltd∥ 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 Intercept of feature - mm
l⊥
All features on a single measurement line perpendicular to the deformation direction within the field of view
Sum of intercepts of the objects
l⊥=∑l⊥i mm
l∥
All features on a single measurement line parallel to the deformation direction within the field of view
Sum of intercepts of the objects
l∥=∑l∥i mm
lL⊥
The characteristic linear fraction in the vertical direction, perpendicular to the deformation direction in the field of view.
Intercept and proportion of features on a single measurement line
lL⊥=
l⊥
Ltd⊥
lL∥
The characteristic linear fraction in the parallel direction, parallel to the deformation direction within the field of view.
Intercept and proportion of features on a single measurement line
lL∥=
l∥
Ltd∥
M Magnification - -
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