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GB/T 8731-2008 English PDF (GBT8731-2008)

GB/T 8731-2008 English PDF (GBT8731-2008)

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GB/T 8731-2008: Free-cutting structural steel

This standard specifies the scope, terms and definitions, ordering information, dimensions, shape, weight and tolerances, technical requirements, test methods, inspection rules, packing, marking and quality certificate of free-cutting structural steels. This standard is applicable to steels such as bar steels, wire rods, steel wires, steel plates, and steel strips that are used for mechanical machining. Their chemical.
GB/T 8731-2008
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 77.140.01
H 40
Replacing GB/T 8731-1988
Free-cutting Structural Steel
ISSUED ON. SEPTEMBER 11, 2008
IMPLEMENTED ON. MAY 01, 2009
Jointly issued by. General Administration of Quality Supervision,
Inspection and Quarantine (AQSIQ);
Standardization Administration (SAC) of the
People's Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 5
1 Scope ... 6
2 Normative References ... 6
3 Terms and Definitions ... 9
4 Classification ... 9
5 Ordering Information ... 10
6 Dimension, Shape, Weight and Tolerance ... 10
7 Technical Requirements ... 11
8 Test Methods ... 15
9 Inspection Rules ... 16
10 Packing, Marking and Quality Certificate ... 17
Appendix A (Informative) Reference Values for Mechanical Properties
of Bar Steels and Wire Rods Made from Free-cutting Structural Steel ... 18 Appendix B (Informative) Comparison Table of Designations in this
Standard with Foreign-countries?€? Designations ... 22
Foreword
This standard replaces GB/T 8731-1988 "Free-cutting Steel - Technical
Requirements".
Compared with the previous standard, the main revision contents of this standard are as follows.
-- Steels such as steel plates and steel strips were added in the application scope (see Chapter 1);
-- The definition of the free-cutting structural steel was added by reference to the definition specified in ISO 683-9.1998 (see Chapter 3);
-- The classification was added (see Chapter 4);
-- The ordering information was added (see Chapter 5);
-- The table that specifies the dimensions, shape and tolerances of the hot-rolled and cold-drawn bar steels, steel wires and bright steels in the previous standard was deleted and replaced by the literal descriptions (Table 1 in 1998 edition; 6.1 in this edition);
-- The composition range of Y12Pb in the previous standard was modified; the designations that are commonly used in foreign countries such as Y08, Y45, Y15Mn, Y45MnS, Y08Pb were added; some designations such as Y08Sn, Y15Sn, Y45Sn and Y45MnSn of the patent ZL 03 1 22768.6 AND the designations that are being manufactured and used by domestic manufacturers such as Y08MnS, Y35Mn,
Y45Mn and Y45MnSPb were added (See Table 1, Table 2 and Table 3);
-- The finished product composition tolerance of the unspecified tin and sulfur element exceeding the specified range in GB/T 222 were added (see Table 5);
-- The requirements of the smelting process were added (see 7.2);
-- Delivery in the bright condition was added in the article of the delivery condition (see 7.3);
-- The requirements of the tensile mechanical property for steels in the previous standard was modified; the must-be-ensured value was changed to be the
reference value and was listed in Appendix A (Table 3, Table 4, Table 5 and Table 6 in 1998 edition; Appendix A in this edition);
-- The requirements of the surface quality was modified; the depth of the allowable defects on the surface of steels such as hot-rolled bar steels, wire rods and hot forged components was quoted from the relevant requirements of GB/T 699; the bright steel was implemented by the relevant requirements of GB/T 3207; the requirements of the surface quality for steel plates and steel strips were added (2.7 in 1988 edition; 7.9 in this edition);
-- Appendix B, the corresponding relationship between the specified designations in this standard and the foreign-countries relevant designations, was added. Appendix A and Appendix B of this standard are informative.
This standard was proposed by China Iron and Steel Association.
This standard shall be under the jurisdiction of the National Technical Committee on Iron and Steel of Standardization Administration of China.
Drafting organizations of this standard. Shougang Group, Dongbei Special Steel Group CO., LTD., Guiyang Special Steel Co., Ltd., Qingdao Iron and Steel Group CO., LTD., and China Metallurgical Information and Standardization Institute. Chief drafting staffs of this standard. Gong Cui, Zhu Chen, Wang Liping, Yang Liu, Zhang Chunhong, Zhou Yinghao, Tian Qiaoli, and Zhang Qizhu.
The previous edition replaced by this standard is as follows.
-- GB/T 8731-1988.
Introduction
The issuing organization of this standard calls attention to the following fact. When claiming that it complies with this standard, it may use the relevant patents related to the relevant tin-bearing free-cutting structural steel in Table 3, namely, the designations Y08Sn, Y15Sn, Y45Sn and Y45MnSn.
The issuing organization of this standard has no opinion to the scope, validity and verification materials of patents.
The patent holder has already guaranteed to the issuing organization of this standard that he/she is willing to negotiate with any applicant about the application authorization license, under the reasonable and non-discrimination provisions and conditions. In this respect, the statement of this patent holder has already been recorded in the issuing organization of this standard. The relevant information may be obtained from the following address.
Patent name. "Tin-bearing Free-cutting Structural Steel"
Patent number. ZL 03 1 22768.6
International patent main classification number. C22C 38/04
Patent holder. Shougang Group
Contact person. Zhu Chen
Communication address. Shougang Research Institute of Technology,
Shijingshan District, Beijing, China
Post code. 100041
Please note that except the above-mentioned identified patent, some contents of this standard may involve in patents; the issuing organization of this standard shall not undertake the responsibility of identifying these patents.
Free-cutting Structural Steel
1 Scope
This standard specifies the scope, terms and definitions, ordering information, dimensions, shape, weight and tolerances, technical requirements, test methods, inspection rules, packing, marking and quality certificate of free-cutting structural steels.
This standard is applicable to steels such as bar steels, wire rods, steel wires, steel plates, and steel strips that are used for mechanical machining. Their chemical compositions are also applicable to ingots, billets and their products. 2 Normative References
The following normative documents contain provisions which, through reference in this text, constitute provisions of this national standard. For dated references, subsequent amendments (excluding corrigendum) or revisions of these publications do not apply. However, the parties who have entered into an agreement according to this standard are encouraged to study whether the latest edition of the normative document is applicable. For undated references, the latest edition of the normative document referred to applies.
GB/T 222 Permissible Tolerances for Chemical Composition of Steel Products GB/T 223.3 Methods for Chemical Analysis of Iron, Steel and Alloy - The Diantipyrylmethane Phosphomolybdate Gravimetric Method for the Determination of Phosphorus Content
GB/T 223.11 Methods for Chemical Analysis of Iron, Steel and Alloy - The Ammonium Persulfate Oxidation Volumetric Method for the Determination of Chromium Content
GB/T 223.12 Methods for Chemical Analysis of Iron, Steel and Alloy- The Sodium Carbonate Separation - Diphenyl Carbazide Photometric Method for the
Determination of Chromium Content
GB/T 223.19 Methods for Chemical Analysis of Iron, Steel and Alloy. The Neocuproine-chloroform Extraction Photometric Method for the Determination of Copper Content
GB/T 223.23 Iron Steel and Alloy - Determination of Nickel Content - The Dimethylglyoxime Spectrophotometric Method
GB/T 223.29 Methods for Chemical Analysis of Iron, Steel and Alloy - The Xylenol Orange Photometric Method for Determination of Lead Content after Carrier Precipitation
GB/T 223.50 Methods for Chemical Analysis of Iron, Steel and Alloy - The Phenylfuorone-CTMAB Direct Photometric Method for the Determination of Tin Content
GB/T 223.58 Methods for Chemical Analysis of Iron, Steel and Alloy - The Sodium Arsenite-sodium Nitrite Titrimetric Method for the Determination of Manganese Content
GB/T 223.59 Methods for Chemical Analysis of Iron, Steel and Alloy. The Reduced Molybdoantimonyl Phosphoric Acid Photometric Method for the
Determination of Phosphorus Content
GB/T 223.60 Methods for Chemical Analysis of Iron, Steel and Alloy. The Perchloric Acid Dehydration Gravimetric Method for the Determination of Silicon Content
GB/T 223.61 Methods for Chemical Analysis of Iron, Steel and Alloy. The Ammonium Phosphomolybdate Volumetric Method for the Determination of
Phosphorus Content
GB/T 223.62 Methods for Chemical Ana...

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