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GB/T 28300-2012 English PDF (GBT28300-2012)

GB/T 28300-2012 English PDF (GBT28300-2012)

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GB/T 28300-2012: Surface quality classes for hot-rolled bars and rods technical delivery conditions

This Standard specifies the terms and definitions, code, requirements, test, modification, etc. for the surface quality of hot-rolled bars and rods. This Standard is applicable to the surface quality classes of hot-rolled bars and rods with nominal dimension of 5mm ~ 150mm. The hot-rolled bars and rods with nominal dimension greater than 150mm can also be applicable through the negotiation between the supplier and the purchaser.
GB/T 28300-2012
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 77.140.60
H 40
Surface Quality Classes for Hot-Rolled
Bars and Rods Technical Delivery Conditions
ISSUED ON. MAY 11, 2012
IMPLEMENTED ON. FEBRUARY 1, 2013
Issued by. General Administration of Quality Supervision, Inspection and Quarantine;
Standardization Administration of PRC.
3. No action is required - Full-copy of this standard will be automatically and immediately delivered to your EMAIL address in 0~60 minutes.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Terms and Definitions ... 4
4 Codes ... 6
5 Requirements ... 6
6 Test ... 10
7 Grinding ... 12
Appendix A (Informative) Description of Discontinuities on Common Hot-
Rolled Bars and Rods ... 13
Appendix B (Informative) Clause No. Comparison between this Standard
and EN 10221.1995 ... 16
Appendix C (Informative) Technical Differences and Causes between this
Standard and EN 10221.1995 ... 17
Bibliography ... 18
Foreword
This Standard was drafted as per the rules specified in GB/T 1.1-2009.
This Standard adopts the re-drafting method to modify and use EN 10221.1995 Surface Quality Classes for Hot-Rolled Bars and Rods Technical Delivery Conditions (English Version).
Compared with EN 10221.1995, this Standard has the structural adjustment; the Appendix B lists the clause comparison list between this Standard and EN 10221.1995. There are technical differences between this Standard and EN 10221.1995; the clauses of these difference involved have been marked by a vertical single line (|) in the blank positions of the outer margin; Appendix C gives the corresponding technical differences and their causes.
This Standard was proposed by China Iron and Steel Association.
This Standard shall be under the jurisdiction of National Technical Committee for Standardization of Steel (SAC/TC 183).
Drafting organizations of this Standard. Shougang Corporation, China Metallurgical Information and Standardization Institute, and Jiangsu Shagang Group Co., Ltd. Chief drafting staffs of this Standard. Tang Mu, Xie Ruiping, Wang Liping, Luan Yan, Dai Qiang, and Huang Zhengyu.
Surface Quality Classes for Hot-Rolled
Bars and Rods Technical Delivery Conditions
1 Scope
This Standard specifies the terms and definitions, code, requirements, test, modification, etc. for the surface quality of hot-rolled bars and rods. This Standard is applicable to the surface quality classes of hot-rolled bars and rods with nominal dimension of 5mm ~ 150mm. The hot-rolled bars and rods with nominal dimension greater than 150mm can also be applicable through the negotiation between the supplier and the purchaser.
This Standard is applicable to the engineering steel; can also be used for structural steel or tool steel through the negotiation between the supplier and the purchaser. This Standard doesn?€?t include the depth requirements of surface decarburization layer. 2 Normative References
The following documents are essential to the application of this document. For the dated documents, only the versions with the dates indicated are applicable to this document; for the undated documents, only the latest version (including all the amendments) are applicable to this document.
GB/T 239 Metallic Materials Wire Torsion Test (GB/T 239-1999, eqv ISO
7800.1984; ISO 9649.1990)
YB/T 5293 Metallic Materials - Forging Test
3 Terms and Definitions
The following terms and definitions are applicable to this document.
3.1 Delivery lot
Unless otherwise specified in the ordering list and product standard; the delivery lot indicates the steel with the same grade, specification and delivery state; ordered by the same surface quality class; and delivered at the same time.
3.2 Bar
3.2.1 Rounds
The bar with cross-section of round shape, and general diameter of no less than 8mm. [GB/T 15574-1995, definition 6.2.1.2.1.1]
3.2.2 Squares
The bar with cross-section of square shape, and general side length of no less than 8mm.
[GB/T 15574-1995, definition 6.2.1.2.1.2a)]
3.2.3 Hexagons
The bar with cross-section of hexagon shape, and the opposite side distance of no less than 8mm.
[GB/T 15574-1995, definition 6.2.1.2.1.2b)]
3.2.4 Octagons
The bar with cross-section of octagon shape, and the opposite side distance of no less than 8mm.
[GB/T 15574-1995, definition 6.2.1.2.1.2c)]
3.3 Rod
The finished product after hot-rolling is delivered in disk. Generally, the cross-section shall be round, oval, square, rectangular, hexagonal, octagonal, semi-circular, and other shapes; the nominal dimension of the wire rod shall be no less than 5mm. The surface of the wire rod is smooth, it can be used for further processing deformation. 3.4 Discontinuities
Irregular shape of convex and concave.
NOTE. the description for the discontinuities of the common hot-rolled bars and rods can refer to Appendix A.
3.4.1 Imperfections
The discontinuities with depth and height no greater than the specified limit. 3.4.2 Defects
5.2 Ordering
The following contents shall be indicated in the contract.
a) Surface quality classes (see Table 2);
b) Maximum allowable number of defects;
1) If the original depth of the discontinuities still can be measured after the material processing, then the maximum allowable number of defects za for the whole delivery lots shall be confirmed during or after the material processing (see NOTE 1 and NOTE 2);
2) If the whole delivery lots can be inspected before processing, then the maximum allowable number of defects zb for the whole delivery lots shall be confirmed before the material processing (see NOTE 1 and NOTE 2);
3) If it is impossible to inspect the whole delivery lot, then special agreement shall be concluded to confirm the maximum allowable number of defects z.
c) The type of test, for instance. inspect and give the Acceptance Quality Limit (AQL) and inspection plan through sampling; obtain quality level inspection through the statistical process control. 1)
NOTE 1. Due to the limit of the continuous inspection equipment of the wire rod, against the measurement value of the depth or height accuracy of imperfections, generally it can only inspection the end of the coil. Therefore, it can?€?t be proved that there are no discontinuous defects beyond the specified value in the entire coil.
NOTE 2. The treatment method against the defective materials shall be confirmed through negotiated when inquiring and ordering; for instance. whether return the products to the factory or abandoned or other treatment. Similarly, the treatment method against the defective materials that have passed the acceptance in the whole delivery lots shall also be confirmed through negotiation when inquiring and ordering.
5.3 Marking
The requirements for surface quality shall be indicated when inquiring and ordering. The following Items a) and b) are the marking examples based on the user-specified sampling methods (for instance. test plan, statistical process control, etc.). a) The situation example of Item b) 1) in 5.2
1) Refer to GB/T 2828.1-2003 Sampling Procedures for Inspection by Attribute ?€? Part 1. Sampling Schemes Indexed by Acceptance Quality Limit(AQL) for Lot-By-Lot Inspection, and GB/T 13393-2008 Guide to Acceptance Sampling Inspection
6.2.2 Inspection method of discontinuities
The following methods or other suitable methods are applicable for inspecting the discontinuities.
6.2.2.1 Non-destructive method, for instance.
--- Visual examination of appearance;
--- Magnetic flux method; for instance, magnetic particle testing method or probe method;
--- Inductance method (eddy current);
--- Penetration test;
--- Heat phase method.
6.2.2.2 Destructive method
The following test can be considered.
--- Hot upset test (as per YB/T 5293);
--- Cold upset test (as per YB/T 5293);
--- Torsion Test (as per GB/T 239).
6.2.3 Test method of depth or height of discontinuities
6.2.3.1 Non-destructive method, for instance.
--- Magnetic flux test method; use rotated or fixed probe;
--- Inductance method;
--- DC potential probe method;
--- Ultrasonic test.
These methods can only measure the approximate values for the depth or height of discontinuities.
6.2.3.2 To accurately measure the depth or height of discontinuities, it can be only realized through grinding the discontinuities to the root, and checking the metallographic specimens. These two methods?€? measurement against the depth or height is only radial.
6.2.4 Inspection lot
Appendix A
(Informative) ...

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