GB/T 34474-2025 English PDF

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GB/T 34474-2025	RFQ	ASK	3 days	Methods for determination of banded structure of steels	Valid
GB/T 34474.1-2017	265	Add to Cart	Auto, < 3 mins	Determination of Banded Structure of Steel - Part 1: Micrographic Method Using Standards Diagrams	Valid

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)
Date of Implementation: 2026-03-01
Older Standard (superseded by this standard): GB/T 34474.1-2017, GB/T 34474.2-2018

GB/T 34474.1-2017: Determination of Banded Structure of Steel - Part 1: Micrographic Method Using Standards Diagrams

---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Determination of banded structure of steel-Part 1.Micrographic method using standards diagrams ICS 77.040.99 H24 National Standards of People's Republic of China Evaluation of band structure in steel Part 1.Standard rating chart method 2017-10-14 release 2018-07-01 Implementation General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Issued by China National Standardization Management Committee

Contents

Foreword Ⅲ Introduction IV 1 Scope 1 2 Normative references 1 3 Terms and definitions 1 4 Overview and Application 1 5 Sampling 2 6 Sample preparation 5 7 Evaluation method 5 7.1 Observation Method 5 7.2 Comparison Method 5 7.3 Standard rating map 5 8 Test report 6 Appendix A (Normative Appendix) Standard Rating Chart 7

Foreword

GB/T 34474 "Assessment of Banded Structure in Steel" is intended to be divided into several parts. This part is part 1 of GB/T 34474. This section was drafted in accordance with the rules given in GB/T 1.1-2009. This part is proposed by China Iron and Steel Association. This part is under the jurisdiction of the National Steel Standardization Technical Committee (SAC/TC183). This section was drafted by. Fushun Special Steel Co., Ltd., Metallurgical Industry Information Standards Institute, Daye Special Steel Co., Ltd., Shougang Corporation, Institute of Metal Research, Chinese Academy of Sciences, Tianjin Iron and Steel Group Co., Ltd. The main drafters of this section. Cheng Lijie, Luan Yan, Gu Qiang, Ju Xinhua, Gai Xiuying, Lu Bihong, Zhang Long.

Introduction

This part of GB/T 34474 is based on the geometric distribution of ferrite bands of hypoeutectoid steel, and does not strictly stipulate the second type of organization band. composition. This part is used to determine the band structure of ferrite and pearlite in near-equilibrium state of subeutectoid steel, and also for ferrite and other non-flat Banded tissue assessment of the balance organization. Evaluation of band structure in steel Part 1.Standard rating chart method

1 Scope

This part of GB/T 34474 stipulates the use of comparative methods for the hypoeutectoid steel band structure (including ferrite bands and second type structure bands) Assessment method. This section is applicable to the evaluation of the band structure of hypoeutectoid steel after plastic deformation, but not to the evaluation of the band structure of carbide in hypereutectoid steel.

2 Normative references

The following documents are essential for the application of this document. For dated references, only the dated version applies to this article Pieces. For the cited documents without date, the latest version (including all amendments) applies to this document. GB/T 13298 Metal microstructure inspection method GB/T 30067 Metallographic Terms

3 Terms and definitions

The terms and definitions defined in GB/T 30067 and the following apply to this document. 3.1 Banded structure During the plastic processing of steel, the deformation and elongation of the microsegregation zone result in an alternating zone of microstructure parallel to the processing direction. Note. This refers to ferrite and the second type of tissue belt. 3.2 Second class organization band classⅡstructurebanding Other tissues besides ferrite, including pearlite, bainite and other non-equilibrium tissues, are single or mixed together. Note. At the time of evaluation, they participate in the evaluation as an organization category. 3.3 Continuous banding In a field of view, the same type of structure band appears, only grain boundaries are separated between the grains, and no other type of structure exists.

4 Overview and Application

4.1 This section describes the degree of banded tissue segregation based on the morphology of the tissue. 4.2 The segregation that occurs during solidification of steel forms a regular arrangement during subsequent deformation, and the solid phase transition is affected by microsegregation, which may cause Produce alternately arranged microstripes. This method describes the difference in the extent of the micro-ribbon structure morphology along the deformation direction. 4.3 The micro-segregation zone formed by solidified selective crystallization is the root cause of the distribution of the banded structure. The subsequent deformation of the micro-segregation zone Process elongation forms a layered structure parallel to the direction of deformation. Other factors may also affect the formation of banded structures, such as the heating of thermal processing Temperature and final forging temperature, deformation rate of cold working or hot working. The hardenability and cooling rate determine the phase transformation decomposition, the formation of microstructure, The cooling rate of the final phase transformation has the greatest influence on the display degree of the band-like structure. 4.4 Band structure will affect the anisotropy of mechanical properties. 4.5 The results obtained by the inspection can be used for product inspection according to the technical agreement reached between the supplier and the buyer, or to compare different manufacturing processes Or process changes, or provide data for organization-performance-application research. 4.6 After the same sample has undergone different heat treatments, there will be differences in the level of the banded structure. The test status of the sample shall be indicated. 4.7 This part adopts the comparison and rating of the observed field of view and the atlas of this part. The magnification of the standard rating picture is 100×, the standard The field of view diameter is 80mm. 4.8 Appendix A gives the ratings of the five series A~E. The levels of each series of pictures range from 0 to 5, and these levels The number of voxel bands, the degree of penetration through the field of view, continuity and width increase. See 7.3 for the specific boundaries. Note. When more non-equilibrium structures appear in the structure, the segregation of alloy elements is not fully reflected. It is recommended to control the unbalanced group when using standard rating pictures The texture content, generally requires that the bainite content is not greater than 30%.

5 Sampling

5.1 In general, the sample should be intercepted on the product in the delivery state, and the inspection area of the sample is about.200mm2 (20mm×10mm). Sampling method and quantity are specified according to product standards or technical conditions. 5.2 If the product standard does not specify, the sampling method is as follows. a) For steel with diameter or side length or thickness less than 25mm, the inspection surface is the entire longitudinal section passing through the steel axis or width 1/4 Face, see Figure 1; b) For steel with diameter or side length greater than 25mm and less than or equal to 40mm, the inspection surface is the entire longitudinal section from the center to the edge, see figure 2; c) For steel with a diameter or side length greater than 40mm, the inspection surface is a longitudinal specimen from the outer surface to the center of the center, see Figure 3; d) For a flat bar with a thickness less than or equal to 25 mm, the full thickness section of the inspection surface at a width of 1/4, see Figure 4; e) For flat materials with a thickness greater than 25mm and less than or equal to 50mm, the inspection surface is located at a width of 1/4, from the center to the surface 1/2 The longitudinal section of thickness, see Figure 5; f) For flat materials with a thickness greater than 50mm, the inspection surface is a longitudinal section at a width of 1/4 from the center to the surface of 1/4 thickness, see Image 6; g) For flat materials with a thickness greater than 80mm, the inspection surface is a longitudinal section with a thickness of 20mm from the center to the surface at a width of 1/4. Figure 1 Steel rod with diameter or side length ≤25mm Figure 2 Steel rods with diameter or side length >25mm~40mm The unit is mm Figure 3 Round rods with diameter or side length > 40mm Explanation. r---width. Figure 4 Sampling of flat materials with thickness ≤25mm Explanation. r---width. Figure 5 Sampling of flat products with thickness >25mm~50mm Explanation. r---width. Figure 6 Sampling of flat bars with thickness >50mm

6 Sample preparation

6.1 The inspection status of the sample shall be in accordance with the product standard or agreement. When not specified, it is recommended to inspect in delivery state. 6.2 Grinding and erosion of the sample shall be carried out in accordance with GB/T 13298.

7 Evaluation methods

7.1 Observation The following methods can be selected for inspection under the microscope. a) Projection method. project the image of the banded tissue on the screen, it should be guaranteed to be enlarged 100 times, the actual field of view diameter is 0.80mm, projection The size of the image on the screen is 80mm, and then compare this image with the standard rating chart; b) Direct observation method. Direct observation through the eyepiece, magnification of 100 times, the actual field of view diameter is 0.80mm, you can use the ϕA ruler with a field diameter of 80mm or use the field bar to determine the inspection area. 7.2 Comparison method 7.2.1 When evaluating the band structure in steel, the number of ferrite bands should be considered, and the degree, continuity and ferrite penetration of the ferrite bands should be considered The width of the band determines the level of banding. When rating, the most serious field of view on the inspection surface should be selected and compared with the rating map Rating. 7.2.2 The rating results are expressed in numbers representing levels and letters in series, such as 1A, 3B, etc. Between two adjacent levels, assessment Half grade, for example, between grade 2 and grade 3, is rated as grade 2.5. 7.3 Standard rating map 7.3.1 The band diagram is composed of white and black two types of organization, white is ferrite, black is the second type of organization, see Appendix A. 7.3.2 The banding structure rating map is divided into five series A to E according to carbon content. a) A series. the banded structure rating of steel with carbon content less than 0.10%; b) B series. the banded structure rating of steel with carbon content of 0.10%~0.19%; c) C series. rating of the ribbon structure of steel with a carbon content of 0.20% to 0.29%; d) D series. rating of the ribbon structure of steel with carbon content of 0.30%~0.39%; e) E series. the rating of the ribbon structure of steel with carbon content of 0.40%~0.60%. Note. The presence of alloy elements will affect the eutectoid point, and the faster cooling rate may also cause a pseudo-eutectoid structure. According to the carbon content, the series is divided, and there may be ferrite. If the ratio does not match the picture, the applied picture series can be determined in the technical agreement between the supplier and the buyer. If not specified, according to the nominal carbon of the steel The content selection uses the series of pictures. 7.3.3 The level of each series of pictures is from level 0 to level 5, increasing according to the number of ferrite bands, the degree of penetration through the field of view, continuity and width And increasing. Table 1 gives a detailed description of the organizational characteristics of each level. Table 1 Organizational characteristics of each level Organizational characteristics of level A seriesa Organizational characteristics of series other than A series 0 Isometric ferrite grains and a small amount of second-phase structure, no uniform equiaxed ferrite and second-type structure, no banding The general orientation of the tissue is the direction of deformation, there is no continuous penetration of the field of view Deformed ferrite band Ferrite aggregates, oriented in the direction of deformation, without continuous penetration of the field of view Ferrite band Table 1 (continued) Organizational characteristics of level A seriesa Organizational characteristics of series other than A series One to two continuous deformations on the isometric ferrite grain matrix Ferrite band There are 1 to 2 continuous ferrite bands that run through the entire field of view. Zhou Wei intermittent ferrite zone and the second type of tissue zone There are more than two strips on the equiaxed ferrite grain matrix throughout the entire Field, continuous deformed ferrite band More than two continuous ferrite belts that run through the entire field of view, and are broken around Continued ferrite zone and the second type of tissue zone Isometric ferrite grains and wider deformed ferrite bands Alternate field of view Through the field of view, a wide, continuous ferrite belt and a second type of tissue belt, Evenly alternating Isometric ferrite grains and a large number of wider deformed ferrite bands Alternating zone across the field of view Through the field of view, wide, continuous ferrite bands and second-type tissue bands, not Evenly alternating a A series ferrite belt refers to deformed ferrite belt.

8 Test report

The test report should include the following. a) Standard number; b) Steel grade and furnace number; c) Product specifications and dimensions; d) Check the condition of the sample; e) inspection results; f) inspection date; g) Signature of the inspector.

Appendix A

(Normative appendix) Standard rating chart A.1 A series rating chart is shown in Figure A.1. Level 0 Level 1 Figure A.1 A series rating chart level 2 Level 3 Figure A.1 (continued) level 4 Level 5 Figure A.1 (continued) A.2 B series rating chart is shown in Figure A.2. Level 0 Level 1 Figure A.2 B series rating chart level 2 Level 3 Figure A.2 (continued) level 4 Level 5 Figure A.2 (continued) A.3 C series rating chart is shown in Figure A.3. Level 0 Level 1 Figure A.3 C series rating chart level 2 Level 3 Figure A.3 (continued) level 4 Level 5 Figure A.3 (continued) A.4 D series rating chart is shown in Figure A.4. Level 0 Level 1 Figure A.4 D series rating chart level 2 Level 3 Figure A.4 (continued) level 4 Level 5 Figure A.4 (continued) A.5 E series rating chart is shown in Figure A.5. Level 0 Level 1 Figure A.5 E series rating chart level 2 Level 3 Figure A.5 (continued) level 4 Level 5 Figure A.5 (continued) ......

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