GB/T 34474: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivered in | Standard Title (Description) | Status | PDF |
| GB/T 34474-2025 | English | RFQ |
ASK
|
3 days [Need to translate]
|
Methods for determination of banded structure of steels
| Valid |
GB/T 34474-2025
|
| GB/T 34474.1-2017 | English | 265 |
Add to Cart
|
0--9 seconds. Auto-delivery
|
Determination of Banded Structure of Steel - Part 1: Micrographic Method Using Standards Diagrams
| Valid |
GB/T 34474.1-2017
|
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| | Sector / Industry | National Standard (Recommended) | | Date of Implementation | 2026-03-01 | | Older Standard (superseded by this standard) | GB/T 34474.1-2017, GB/T 34474.2-2018 | GB/T 34474.1-2017: Determination of Banded Structure of Steel - Part 1: Micrographic Method Using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)
|