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GB/T 8731-2008 PDF in English


GB/T 8731-2008 (GB/T8731-2008, GBT 8731-2008, GBT8731-2008)
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GB/T 8731-2008: PDF in English (GBT 8731-2008)

GB/T 8731-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S 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...
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.