GB/T 6478-2015Steels for cold heading and cold extruding (English PDF)

Foreword

This Standard was drafted as per the rules specified in GB/T 1.1-2009.

This Standard replaced GB/T 6478-2001 Steels for Cold Heading and Cold Extruding.

Compared with GB/T 6478-2001, this Standard has the major technical changes as

follows.

--- Expand the upper limit of applicable wire rod diameter from 40mm to 60mm;

--- Add non-quenched/tempered steel for cold heading and cold extruding in the

"classification";

--- Confirm the allowable deviation of hot-rolled wire rod dimension conforms to the

provisions of Grade-B accuracy stipulated in GB/T 14981-2009;

--- Add 14 grades and relevant technical requirements, such as ML06Al, ML10,

ML12Al, ML12, ML15Cr, ML30Cr, ML45Cr, ML20CrMo, ML25CrMo, ML45CrMo,

ML25B, ML25MnB, ML30MnB, ML40Mnb;

--- Add MFT8, MFT9 and MFT10 non-quenched/tempered steel for cold heading

and cold extruding, and relevant requirements;

--- Increase the manganese content in Grade ML30~ML45 from 0.30%~0.60% to

0.60%~0.90%; delete the relevant requirements of two Grades ML30Mn and

ML35Mn;

--- Adjust ML22Mn into ML20Mn; ML37Cr into ML35Cr; ML42CrMo into ML40CrMo;

ML28B into ML30B;

--- Straighten the phosphorus content and sulfur content in the quenched/tempered

steel for cold heading and cold extruding from "<=0.035%" to "<=0.025%";

--- Add the refining requirements outside of the furnace;

--- Modify the decarburization requirements;

--- Modify the macrostructure requirements;

--- Modify the surface quality requirements;

--- Add the relevant provisions of digit rounding off;

--- Modify the re-inspection and judgment rules;

--- Add Appendix B "Grade Comparison List between this Standard and ISO

4954.1993, etc.";

--- Add Appendix C "Clause No. Comparison List between this Standard and Parts

of ISO 4954.1993"

--- Add Appendix D "Technical Difference and Causes between this Standard and

ISO 4954.1993".

This Standard adopts the re-drafting method to modify and use ISO 4954.1993 Steels

for Cold Heading and Cold Extruding.

Compared with ISO 4954.1993, this Standard has more adjustments in the structure;

Appendix C gives the Clause No. Change Comparison List between this Standard and

ISO 4954.1993.

Considering China's national conditions, this Standard modifies ISO 4954.1993 when

adopting it; the relevant technical differences have been compiled into the text; the

involved clauses of which have been marked with vertical single line in the blank

margin of the clauses. Appendix D gives the technical differences and causes list for

reference.

This Standard has also made the following editorial changes.

--- Replace "this international standard" with "this Standard";

--- Replace "comma that represents decimal point" with "decimal point";

--- Delete the foreword of the international standard.

This Standard was proposed by China Iron and Steel Industry Association.

This Standard shall be under the jurisdiction of National Technical Committee for

Standardization of Steel (SAC/TC 183).

Drafting organizations of this Standard. Jiangsu Shagang Group Co., Ltd.,

Zhangjjiagang Lianfeng Iron and Steel Research Institute Co., Ltd., Qingdao Iron and

Steel Co., Ltd., Fangda Special Steel Technology Co., Ltd., Ningbo Zhenhai Jinli High

Strength Fasteners Co., Ltd., Hangzhou Iron and Steel Group Company, China

Metallurgical Information and Standardization Research Institute, Xingtai Iron and

Steel Co., Ltd., Beijing Jiaotong University, Shougang Corporation, and Magang

(Group) Holding Co., Ltd.

Chief drafting staffs of this Standard. Li Xiaobo, Yuan Changsheng, Luan Yan, Hui

Weijun, Huang Zhengyu, Zhang Xiantie, Hu Haiping, Zhang Na, Lu Xinwu, Wo Jinyuan,

and Yu Tongren.

The historical editions replaced by this Standard are as follows.

--- GB/T 6478-1986, GB/T 6478-2001.

Steels for Cold Heading and Cold Extruding

1 Scope

This Standard specifies the classification, grade, ordering contents, dimension,

appearance, weight and allowable deviation, technical requirements, test methods,

inspection rules, package, mark, and quality certificate, etc. for the non-alloyed steels

and alloyed structural steels for cold heading and cold extruding.

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 222 Permissible Tolerance 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

3 Booking Contents

According to this Standard, the booking contract shall include the following contents.

4 Classification and Grade Expression method

The steels can be divided into four types according to the using state in this Standard.

not heat-treated steel, case-hardened steel, quenched and tempered steel (including

boron-contained steel) and non-quenched and tempered steel for cold heading and

cold extruding.

5 Dimension, Appearance, Weight and Allowable Deviation

6 Technical Requirements

The quenched and tempered steel (including the boron-contained steel) or non-

quenched and tempered steel shall conduct the decarbonization layer test. The depth

of decarbonization layer shall conform to the provisions of Table 9.

According to the demand of the purchaser, the steel shall be conducted macrostructure

acid leaching inspection.

7 Test Methods

8 Inspection Rules

The steels shall be checked and accepted per batch; each batch consists of the steels

with the same furnace number, the same grade, the same specification and the same

heat-treatment furnace times.

9 Package, Mark, and Quality Certificate

Unless otherwise is specified, the steel package, mark and quality certificate shall

conform to the provisions of GB/T 2101.

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