GB/T 1979-2025 (GB/T 1979-2001) PDF EnglishUS$70.00 · In stock · Download in 9 seconds
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Similar standardsGB/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/GBT1979-2001GB 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 ContentsForeword... 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... 65ForewordThis 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 steels1 ScopeThis 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 referencesThe 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 etching3 Cutting and display method of the test-sampleThe 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 defects4.1 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 diagram5.1 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 method6.1 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 reportTest 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. |
