GB/T 1979-2025 (GB/T 1979-2001) PDF English
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Evaluation of macrostructural defects in structural steels - Acid etching method and ultrasonic testing method
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Standard diagrams for macrostructure and defect of structural steels
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GB/T 1979-2001: Standard diagrams for macrostructure and defect of structural 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/GBT1979-2001
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.01
H 24
Replacing GB/T 1979-1980
Standard diagrams for macrostructure
and defect of structural steels
Issued on. DECEMBER 17, 2001
Implemented on. MAY 1, 2002
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative references... 5
3 Cutting and display method of the test-sample... 5
4 Classification, characteristics, causing reasons and assessment principles of
the defects... 5
5 Classification and applicable scope of the standard diagram... 10
6 Assessment method... 10
7 Test report... 12
Appendix A... 13
References... 65
Foreword
This revision of this Standard modifies the following provisions (diagrams).
- Modify the previous spot-segregation character into the spotted segregation;
- Partially modify and supplement the assessment principle of the previous ingot-shape
segregation and subsurface blowholes.
- Partially modify and supplement the characteristics and assessment principle of the
previous peeling.
- Partially modify the causing reason of the previous white spot.
- Modify and supplement the characteristics and assessment principle of the previous
axial inter-crystalline cracks.
- The previous standard diagram I. appropriately modify the general-porosity grade-4
diagram;
- The previous standard diagram II. appropriately modify the ingot-shape segregation
grade-4 diagram;
- The previous standard diagram III. cancel the rating of the peeling; retain the previous
diagram as the representative diagram.
The main amended and additional contents of this revision are as follows.
- The provisions of "2 - Normative references", "3 - Cutting and display method of test-
sample" AND "7 - Test report";
- The defect name, characteristics, causing reasons, assessment principles and
diagrams of white-band AND center segregation;
- The defect name, characteristics, causing reasons and assessment principles of cap
segregation;
- 4 ingot-shape-segregation grading diagrams which are less than 40mm;
- There are totally 12 diagrams of general-porosity, central-porosity and ingot-shape-
segregation grading diagrams with 4 diagrams for each one, greater than 250mm.
Appendix A of this Standard is normative.
This Standard replaces GB/T 1979-1980 “Diagram of a low magnification texture blemish
grading of structural steel” from the date of implementation.
This Standard was proposed by the former State Bureau of Metallurgical Industry.
This Standard shall be under the jurisdiction of the Technical Committee on Steel of
Standardization Committee of China.
Main drafting organizations of this Standard. Shanghai Fifth Iron & Steel Co., Ltd. of
BaoSteel Group, Taiyuan Iron & Steel (Group) Co., Ltd., China Metallurgical Information
and Standardization Institute, Fushun Special Steel Co., Ltd. AND Special Steel Co., Ltd.
of Chongqing Iron and Steel Group.
The main drafters of this standard. Yuan Xinfang, Zhang Shengke, Luan Yan, Zeng Wentao,
Hua Wenjie, Li Yuchun and Sun Shiqiu.
This Standard was first issued in August 1980.
Standard diagrams for macrostructure
and defect of structural steels
1 Scope
This Standard specifies and describes the classification, characteristics, causing
reasons and assessment principles, classification and the scope of application of the
standard diagram, assessment methods and test report of acid-pickling
macrostructure-defect of structural steel.
This Standard is applicable to assess the allowable and unallowable defects in the
acid-pickling macrostructure of the cross-section of carbon structural steel, alloy
structural steel and spring steel products (forging billet, rolling billet). According to the
agreement between the supply-demand parties, it can also be used to assess the
defects in other steel’s macrostructure.
2 Normative references
The provisions in following documents become the provisions of this Standard through
reference in this Standard. For the dated references, the subsequent amendments
(excluding corrections) or revisions do not apply to this Standard, however, parties who
reach an agreement based on this Standard are encouraged to study if the latest
versions of these documents are applicable. For undated reference documents, the
latest versions apply to this Standard.
GB/T 226 Test method for macrostructure and defect of steel by etching
3 Cutting and display method of the test-sample
The test-sample shall be cut and displayed according to the provisions of GB/T 226.
4 Classification, characteristics, causing reasons and assessment principles of the defects
4.1 General porosity
Characteristic. on the acid-pickling test-piece, it appears that the tissue is not compact;
it appears as the dark spots and the gaps, which are dispersed on the whole cross-
section. Most of the dark spots appear as the roundness or oval. Through the
observation under the magnifying glass, most of the gaps appear as the irregular holes
or round pinhole. These dark spots and gaps generally appear between the principal
axis and each secondary axis of the thick dendritic crystal. The porosity zone is dark;
the axis is bright. If the difference of the corrosion degree between the dark zone and
bright zone is not large, then it shall not generate pits.
4.2 Central porosity
Characteristic. The central part of the acid-pickling test-piece appears centrally-
distributed gaps and the dark spots. The main difference between it and the general
porosity is that the gaps and dark spots only exist at the central portion of the test-
sample, rather than disperse throughout the cross-section.
4.3 Ingot segregation
Characteristic. The frame strap which appears deeper corrosion on the acid-pickling
test-piece, and it is consisted of dark spots and gaps, similar to the shape of the original
ingot cross section, generally square.
4.4 Spotted segregation
Characteristic. on the acid-pickling test-piece, it appears the dark spots of different
shapes and sizes. No matter whether the dark spot and the blowholes exist at the
same time, this dark spot is collectively referred to as the spotted segregation. When
the spots are dispersed over the whole cross section, it is called the general spotted
segregation; when the spot exists on the edge of the test-piece, it is called edged
spotted segregation.
4.5 White-band
Characteristic. on the acid-pickling test-piece, it appears strong corrosion resistance,
and it appears as the dense gloss-white or light-white frame-band.
Causing reasons. it is caused by the improper electromagnetic stirring during the
4.6 Central segregation
Characteristics. on the central part of the acid-pickling test-piece, it appears dark spots
with deep corrosion; sometimes, there are gray-white-bands and porosity around the
dark spots.
4.7 Cap-mouth segregation
Characteristics. on the central part of the acid-pickling test-piece, it appears the dark
and easily-corroded metal zone.
4.8 Subsurface blowholes
Characteristic. On the acid-pickling test-piece, it appears as the elongated slit which is
distributed in dispersed or clustered form, or oval air hole. Most of the elongated slits
are perpendicular to the surface of the steel products (billet).
4.10 Peeling
Characteristics. on the acid-pickling test-piece, some of them appear shiny-white
curved strip or irregular dark-black line, and there are air holes and inclusions on or
around it; some of them are the strips which are consisted of the dense gaps and
inclusions.
4.11 White spot
Characteristics. generally, in addition to the section outside the edge area of the acid-
pickling test-piece, it appears as the sawtooth-shaped fine stripe, in distributions of
radial, concentric-circle or irregular shapes.
4.12 Axial inter-crystalline cracks
Characteristics. this defect commonly appears in the high-alloy stainless & heat
resisting steel (such as Cr5Mo, 1Cr13 and Cr25). Sometimes this defect also appears
on the high-alloy structural steel, such as the 18Cr2Ni4WA. On the acid-pickling test-
piece, it appears three-branch or multi-branch, flexural, fine, spiderweb-shape strips,
from the axis of the billet materials to all directions.
4.13 Internal blowholes
Characteristic. on the acid-pickling test-piece, it appears as the straight or curved
cracks with different lengths. Its inner wall is relatively smooth; some of them have
small visible inclusions.
4.14 Non-metallic inclusions (visually visible) and slag inclusion
Characteristic. on the acid-pickling test-piece, it appears as the particles with different
shapes and colors.
4.15 Dissimilar metal inclusions
Characteristic. on the acid-pickling test-piece, its color is different from that of the
matrix tissue. It is the metal block, without certain shape.
5 Classification and applicable scope of the standard diagram
5.1 According to the size and defect properties of the steel (forging and rolling billet),
see Table 1 for the provisions of the classification and applicable scope of standard
diagrams.
5.2 For the macrostructure-defects of the round steel or square steel of which the
diameter or side length is less than 40mm, except that the “ingot-shape segregation”
is assessed according to standard diagram I,
6 Assessment method
6.1 When assessing various defects, the diagrams which are listed in Appendix A shall
prevail. When conducting the assessment, various defects shall be limited within visual
visibility. In order to determine the category of the defect, it is allowed to use the
magnifying glass which is not greater than 10 times. On the basis of the severity degree
of the defect, conduct comparison according to the assessment principles which are
described in Chapter 4;
6.2 When conducting comparison to assess the defect grade of the steels (billet) in
other sizes, they shall be reduced or enlarged according to the severity degree of the
defect.
6.3 The permissibility and the qualification level of the steel’s macrostructure-defect
shall be specified in the corresponding product standards.
7 Test report
Test report shall include the following contents.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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