GB/T 8731-2008 PDF English
US$85.00 · In stock · Download in 9 secondsGB/T 8731-2008: Free-cutting structural steel Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedureStatus: Valid GB/T 8731: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB/T 8731-2008 | English | 85 |
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Free-cutting structural steel
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| GB/T 8731-1988 | English | 285 |
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Free-cutting steel--Technical requirements
| Obsolete |
Excerpted PDFs (Download full copy in 9 seconds upon purchase)PDF Preview: GB/T 8731-2008
GB/T 8731-2008: Free-cutting structural steel---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/GBT8731-2008
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
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
3 Terms and Definitions
The following terms and definitions are applicable to this standard.
3.1 Free-cutting structural steel
The structural steel that has favorable machining performance because of adding
higher content of sulfur, lead, calcium and other free-cutting elements.
4 Classification
Steels shall be classified into the following two classes according to the different
application and processing methods. The application and processing method for steel
bars shall be noted in the contract; and the unnoted one shall be supplied as steels for
machining.
5 Ordering Information
The contract for ordering goods according to this standard shall cover the following
relevant contents.
6 Dimension, Shape, Weight and Tolerance
6.1 Dimension, shape, weight and tolerance of steels
6.1.1 The dimensions, shape, weight and tolerances for hot-rolled steel bars,
hot-rolled hexagon bars and octagonal steels shall meet the requirements of GB/T 702.
6.1.2 The dimensions, shape, weight and tolerances for forged steel bars shall meet
the requirements of GB/T 908.
6.1.3 The dimensions, shape, weight and tolerances for hot-rolled wire rods shall
meet the requirements of GB/T 14981.
6.2 The deformation length at both ends of all shorn hot-rolled bar steels shall not be
greater than 20mm. It shall be noted in the contract if the purchaser requires to clear
burrs at both ends of bar steels.
6.3 The end of the cold drawn bar steels shall not be cut into a bent shape.
The cut-end may have shear deformations when steels are shearing with the shears.
And the maximum dimension of the end shall not be larger than the nominal
dimension plus the tolerance value, after deformation.
7 Technical Requirements
7.1 Designation and chemical composition
7.1.1 The designations and chemical compositions (heat analysis) of steels such as
sulfur free-cutting steels, lead free-cutting steels, tin free-cutting steels and calcium
free-cutting steels shall be in accordance with those specified in Table 1, Table 2,
7.1.2 As required by the purchaser, other elements that are able to improve the
cutting performance of steels may be properly added based on the agreement of both
the supplier and the purchaser.
7.1.3 For the chemical composition tolerances of finished products of steels, the
free-cutting elements such as sulfur and tin shall be in accordance with those
specified in Table 5; other elements shall meet the requirements of GB/T 222.
7.2 Smelting process
Unless the user has specific requirements, the smelting process shall be specified by
the supplier.
7.3 Delivery condition
Steels shall be delivered in conditions such as hot-rolled, hot forging or cold-rolled,
cold drawn, and bright conditions; the delivery condition shall be indicated in the
contract. They may also be delivered in other conditions as required by the purchaser.
7.4 Mechanical property
7.4.1 The Brinell hardness of the free-cutting bar steels and wire rods delivered in
hot-rolled condition shall be in accordance with those specified in Table 6.
7.4.2 The mechanical property of bar steels and wire rods in conditions of hot-rolled,
hardening and tempering, cold drawn and cold-drawn high tempering may refer to
Appendix A based on the agreement of both the supplier and the purchaser.
7.7 Decarburized layer
As required by the purchaser, the total decarburized layer depth on one side may be
inspected, for steels with nominal carbon content larger than 0.30%; the acceptance
criterion shall be negotiated by the supplier and the purchaser.
7.8 Nonmetallic inclusion
As required by the purchaser, the nonmetallic inclusion of steels may be inspected;
the grade of Class B, C and D inclusions shall all not be larger than Grade 3.
7.9 Surface quality
7.9.4 The surface quality of the bright steel shall meet the requirements of GB/T 3207.
7.9.5 The surface of steel plates and steel strips shall be free from cracks, bubbles,
scars, folds, inclusions and embedded iron oxide scales. The steel plates shall be free
from sub-layers.
8 Test Methods
8.1 The inspection items, sampling quantity, sampling positions and test methods of
each batch of steels shall be in accordance with those specified in Table 9.
8.2 In the tensile test for bar steel, the scale distance of test sample L0=5d0 (d0 is the
sample diameter). The sample diameter shall be in accordance with those specified in Table 10.
8.3 The scale distance of steel wire test samples shall be 100mm.
9 Inspection Rules
9.1 Inspection and acceptance
The inspection and acceptance of steels shall be carried out by the quality supervision
department of the supplier.
9.2 Batching rules
The steels shall be inspected for acceptance in batches; each batch shall be
composed of such steels of the same-designation, same-furnace number,
same-thermal treatment heats (when steels are supplied in heat treatment condition),
same-specification and same-delivery condition.
9.3 Sampling quantity
The sampling quantity for steel inspection shall be in accordance with those specified in Table 9.
9.4 Re-inspection and judgement rules
The re-inspection and judgement rules shall be carried out according to the relevant
requirements of GB/T 17505 or the requirements of the agreement reached by
supplier and the purchaser.
10 Packing, Marking and Quality Certificate
10.1 Packing, marking and quality certificate of bar steels and wire rods shall comply
with those specified in GB/T 2101.
10.2 Packing, marking and quality certificate of steel wires shall comply with those
specified in GB/T 2103.
10.3 Packing, marking and quality certificate of bright steel shall comply with those
specified in GB/T 3207.
10.4 The steel plates and steel strips shall be in accordance with those specified in GB/T 247.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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