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Stainless and heat-resisting steels -- Designation and chemical composition
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GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.20
CCS H 40
Replacing GB/T 20878-2007
Stainless steels - Designation and chemical composition
Issued on. JULY 24, 2024
Implemented on. FEBRUARY 01, 2025
Issued by. State Administration for Market Regulation;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative references... 5
3 Terms and definitions... 5
4 General guidelines for determining chemical composition limits... 6
5 Methods for indicating designations and unified digital codes... 8
6 Stainless steel designations and unified digital codes, their chemical composition and
applications... 8
Annex A (normative) Methods for indicating stainless steel designations and unified
digital codes... 32
Annex B (informative) Physical performance parameters of some stainless steel
designations in this document... 38
Annex C (informative) Comparison table of stainless steel designations in this
document and foreign standard stainless steel designations (or similar designations) 50
Bibliography... 70
Foreword
This document was drafted in accordance with the rules given in GB/T 1.1-2020
"Directives for standardization - Part 1.Rules for the structure and drafting of
standardizing documents".
This document replaces GB/T 20878-2007 "Stainless and heat-resisting steels --
Designation and chemical composition". Compared with GB/T 20878-2007, in addition
to structural adjustments and editorial changes, the main technical changes are as
follows.
a) In the Scope chapter, "heat-resistant steel" was deleted (see Chapter 1 of this
Edition; Chapter 1 of Edition 2007);
b) The term and definition of "heat-resistant steel" was deleted (see Chapter 2 of
Edition 2007);
c) The definition of "austenitic-ferritic (duplex) stainless steel" has been changed
(see Chapter 3 of this Edition; Chapter 2 of Edition 2007);
d) The criteria for determining the limit values of manganese, phosphorus, nitrogen
and copper content have been changed (see 4.3 of this Edition; 3.3 of Edition
2007);
e) The provisions on the representation method of stainless steel designations and
unified digital codes have been added (see Chapter 5 and Annex A of this Edition);
f) Some unified digital code representation methods have been modified (see Table
1~Table 5, Table B.1, Table C.1 of this Edition; Table 1~Table 5, Table A.1, Table
B.1, Table C.1 of Edition 2007);
g) The chemical compositions of 8 designations have been changed (see Table 1,
Table 2, Table 3 and Table 5 of this Edition; Table 1, Table 2, Table 3 and Table 5
of Edition 2007);
h) 97 designations and chemical compositions were added, including 51 for
austenitic stainless steel, 14 for austenitic-ferritic (duplex) stainless steel, 23 for
ferritic stainless steel, 8 for martensitic stainless steel, and 1 for precipitation
hardening stainless steel (see Table 1~ Table 5 of this Edition; Table 1~ Table 5
of Edition 2007);
i) 23 designations and their chemical compositions have been deleted (see Table 1~
Table 5 of this Edition; Table 1~ Table 5 of Edition 2007).
Attention is drawn to the possibility that some of the elements of this document may be
the subject of patent rights. The issuing authority shall not be held responsible for
identifying any or all such patent rights.
This document was proposed by China Iron and Steel Association.
This document shall be under the jurisdiction of National Technical Committee on Steel
of Standardization Administration of China (SAC/TC 183).
The drafting organizations of this document. Metallurgical Industry Information
Standards Research Institute, Shanxi TISCO Stainless Steel Co., Ltd., Fujian Qingtuo
Special Steel Technology Research Co., Ltd., China Iron and Steel Research Institute
Co., Ltd., Huzhou Yongxing Special Stainless Steel Co., Ltd., Fushun Special Steel Co.,
Ltd., Jiangsu Yinhuan Precision Steel Pipe Co., Ltd., Gansu Jiugang Group Hongxing
Steel Co., Ltd., Jiangsu Wujin Stainless Steel Co., Ltd., National Carbon Structural
Steel Product Quality Inspection and Testing Center (Shandong), Sinopec Engineering
Construction Co., Ltd., Shandong Special Equipment Inspection and Research Institute
Group Co., Ltd., Shandong Taishan Iron and Steel Group Co., Ltd., Zhejiang Jiuli
Special Materials Technology Co., Ltd., Xinghua Juxin Stainless Steel Co., Ltd.,
Taizhou Tiansheng Stainless Steel Products Co., Ltd., Taizhou Jiqiang Stainless Steel
Products Co., Ltd., Zhejiang Zhengtong Pipe Industry Co., Ltd., Zhejiang Compass
Fluid Technology Co., Ltd.
Main drafters of this document. Luan Yan, Wu Qiang, Jiang Laizhu, Song Zhigang,
Chen Genbao, Gu Qiang, Liu Yu, Pan Jixiang, Hou Xiaolong, Hua Yangkang, Wang
Jinguang, Shao Yu, Wang Zhiyu, Shi Xianyun, Feng Han, Zhang Yong, Zhao Kun, He
Xikou, Liu Ming, Liu Zhenbao, Li Yufeng, Chen Liang, Fei Ting, Wang Chunmao, Wu
Yuhong, Liu Yonghua, Gu Fengquan, Ji Youlu, Ding Binhua, Zhang Jingjing, Chen
Qingxin, Li Zhaoguo, Yang Xin, Gong Yueqiang.
Versions of standard substituted by this document are.
- It was first published in 1984 as GB/T 4229-1984;
- It was first revised in 2007 as GB/T 20878-2007;
- This is the second revision.
Stainless steels - Designation and chemical composition
1 Scope
This document specifies the designations and unified digital codes of stainless steel and
their chemical composition. It also provides the physical properties of some
designations, and a comparison table of designations and unified digital codes with
foreign standard designations (or similar designations).
The stainless steel designations, unified numerical codes and chemical compositions
specified in this document are applicable to guiding the formulation and revision of
stainless steel (including ingots and semi-finished products) product standards.
NOTE. In this document, the content of each element representing the chemical composition of
stainless steel is expressed in mass fraction.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
GB/T 8170, Rules of rounding off for numerical values & expression and judgement
of limiting values
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 stainless steel
Steel containing at least 10.5% chromium (mass fraction) and not more than 1.2%carbon (mass fraction).
NOTE. Stainless steel is divided into corrosion-resistant steel, heat-resistant steel and creep-
resistant steel according to its main characteristics.
3.2 austenitic stainless steel
Stainless steel that the matrix is mainly composed of austenite with a face-centered
cubic crystal structure, which is mainly strengthened by cold working or nitrogenalloying.
3.3 austenitic-ferritic (duplex) stainless steel
Stainless steel with a matrix consisting of both austenite and ferrite phases (the content
of the lesser phase is at least 25%) that can be strengthened by cold working.
3.4 ferritic stainless steel
Stainless steel that the matrix is mainly composed of ferrite with a body-centered cubic
crystal structure, which generally cannot be hardened by heat treatment, but can be
slightly strengthened by cold working.
4 General guidelines for determining chemical composition limits
4.1 Carbon
When the carbon content is greater than or equal to 0.04%, it is recommended to take
two decimal places. When the carbon content is equal to or less than 0.030%, it is
recommended to take three decimal places.
4.2 Silicon
Unless used as an alloying element, the silicon content of pipes and related products
shall not exceed 0.75%, and the silicon content of long strips and forgings shall not
exceed 1.00%.
4.3 Manganese
The manganese content of austenitic stainless steel (except Cr-Mn-Ni or Cr-Mn-Ni-N
steel) shall not exceed 2.00%. The manganese content of other types of stainless steel
shall not exceed 1.00%.
4.4 Phosphorus
Unless there are special technical requirements that specify a lower limit value, the
phosphorus content of austenitic stainless steel shall not exceed 0.045%.
4.5 Sulfur
Unless there are special technical requirements specifying a lower limit value, the sulfur
content of all types of stainless steel shall not exceed 0.030%. But it does not include free-cutting steel.
4.6 Nickel
Unless special technical requirements require a wider composition range (generally higher content),
4.7 Chromium
4.8 Molybdenum
Unless special technical requirements require a wider composition range, the upper and
lower limits of molybdenum content in all types of molybdenum-containing stainless
steels shall not exceed 1%.
4.9 Copper
As an alloying element, the content of copper shall be specified with upper and lower limits.
4.10 Nitrogen
As an alloying element, the nitrogen content shall be specified with upper and lower limits.
4.11 Niobium and tantalum
Unless a special purpose requires the inclusion of tantalum, when both niobium and
tantalum are listed, it is recommended that only niobium be listed.
5 Methods for indicating designations and unified digital codes
5.1 The methods for indicating stainless steel designations shall comply with the provisions of A.1 in Annex A.
5.2 The unified numerical code for stainless steel designations shall comply with the provisions of A.2.
5.3 Each unified digital code is only applicable to one standard designation. Conversely,
each standard designation only corresponds to one unified digital code. When a standard designation is cancelled,
generally speaking, the original corresponding unified digital code will no longer be assigned to another standard designation.
6 Stainless steel designations and unified digital codes, their chemical composition and applications
6.1 Stainless steel is divided into five categories according to metallurgical
characteristics. austenitic steel, austenitic-ferritic (duplex) steel, ferritic stainless steel,
martensitic steel and precipitation hardening stainless steel.
6.3 This document cannot be used alone for ordering. The chemical composition of the
stainless steel designations in this document is not a requirement for the chemical
composition of any product before it is adopted by product standards or technical
agreements.
6.4 The physical properties parameters of some stainless steel designations in this
document are shown in Annex B.
6.5 See Annex C for a comparison table of stainless steel designations and unified
digital codes in this document and foreign standard designations (or similar designations).
Annex A
(normative)
Methods for indicating stainless steel designations and unified digital codes
A.1 Methods for indicating stainless steel designations
A.1.1 General
A.1.1.1 Stainless steel designations are indicated by combining chemical element
symbols and Arabic numerals (A.1.1.2). The carbon content shall comply with the
provisions of A.1.2.The content of other elements shall comply with the provisions of
A.1.3.
A.1.1.2 The Arabic numerals representing the content (mass fraction) of each element
in the chemical composition of stainless steel shall be rounded to the specified number
of digits in accordance with GB/T 8170.
A.1.2 Carbon content
Generally, two Arabic numerals are used to indicate the carbon content (in parts per ten
thousand). For ultra-low carbon stainless steel with a carbon content not exceeding
0.030%, three Arabic numerals are used to indicate the carbon content (in parts per
hundred thousand) and the following provisions shall be met.
a) If only the upper limit is specified, if the carbon content upper limit is not greater
than 0.10%, then 3/4 of the upper limit is taken to represent the carbon content
(see Example 1). If the carbon content upper limit is greater than 0.10%, then 4/5
of the upper limit is taken to represent the carbon content (see Example 2).
b) If upper and lower limits are specified, the average of the upper and lower limits
is taken to express the carbon content (see Example 3).
A.1.3 Main element content
A.2 Methods for indicating unified digital code for stainless steel designations
A.2.1 The unified digital code ISC (Iron and Steel Code) for stainless steel designations
uses the English letter "S" as the prefix (the first letter of "Stainless"), followed by five
Arabic numerals. The numbering rules are shown in Figure A.1.
A.2.2 For ferritic stainless steel S1××××, the second and third digits indicate the average
chromium content (in percent), the fourth digit indicates the presence of special
elements in the steel (see Example 1), and the fifth digit indicates the steel type or the
serial number of the designation within the same steel group (see Example 2).
Example 1.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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