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Stainless steels - Designation and chemical composition
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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 nitrogen
alloying.
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.
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%. For designations that produce both long strips and flat products, the
silicon content shall not exceed 1.00%. The choice of the lower or higher limit value is
determined by the specific product technical requirements.
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%. But it does not include free-cutting steel containing high sulfur
or selenium or steel that needs to increase nitrogen solid solubility.
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%. The
phosphorus content of other types of stainless steel shall not exceed 0.040%. However,
free-cutting steel is not included.
NOTE. The phosphorus content of some Cr-Mn-Ni or Cr-Mn-Ni-N stainless steels may not exceed
0.060%.
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), the upper and lower limits of nickel content shall not exceed 3%.
4.7 Chromium
The upper and lower limits of chromium content shall be 2%, but the maximum shall
not exceed 3%.
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%.
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.
6 Stainless steel designations and unified digital codes, their
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. The designations and
unified digital codes of various types of stainless steel and their chemical compositions
are listed in Tables 1 to 5.
a) Table 1 shows the designations, unified digital codes and chemical compositions
for austenitic stainless steel.
b) Table 2 shows the designations and unified digital codes as well as their chemical
compositions for austenitic-ferritic (duplex) stainless steel.
c) Table 3 shows the designations, unified digital codes and chemical compositions
for ferritic stainless steel.
d) Table 4 shows the designations, unified digital codes and chemical compositions
for martensitic stainless steel.
e) Table 5 shows the designations and unified digital codes and their chemical
compositions for precipitation hardening stainless steel.
6.2 The chemical composition of the stainless steel designations in this document is
determined based on the general criteria for the chemical composition limits of each
element determined in Chapter 4.Due to special technical reasons, the chemical
composition of the same stainless steel designation may vary slightly in the composition
requirements of each product standard. It is allowed to appropriately adjust the chemical
composition range in the product standard or technical agreement, or to make special
restrictions on the content of residual elements and harmful impurity elements, but the
original designation and unified digital code shall be kept unchanged. New designations
shall not be generated due to composition adjustments. If possible, the chemical
composition of the same designation shall be unified between various stainless steel
product standards.
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).
Example 1.
When the upper limit of carbon content is 0.08%, the content is expressed as 06.When the upper
limit of carbon content is 0.030%, the content is expressed as 022.When the upper limit of carbon
content is 0.020%, the content is expressed as 015.
Example 2.
When the upper limit of carbon content is 0.20%, the content is expressed as 16.When the upper
limit of carbon content is 0.15%, the content is expressed as 12.
Example 3.
When the carbon content is 0.16%~0.25%, 20 is used to represent the content.
A.1.3 Main element content
A.1.3.1 Use one or two Arabic numerals to indicate the average content of the main
elements (except carbon) (in percent). If the average content of the main elements is
less than 1.50%, only the elements shall be indicated in the designation, without
indicating the content (see Examples 1 and 2).
A.1.3.2 The main elements (except carbon) shall be arranged in descending order
according to the element content. If the average content of two or more elements is
equal, they shall be arranged in alphabetical order (see Example 3). If the same group
of designations represent the same, "-1, -2,..." can be added to the end of the designation
to distinguish them (see Example 4).
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.
Figure A.1 -- Schematic diagram of unified digital code for stainless steel
designations
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.
For 019Cr18MoTi, the unified digital code ISC is S11862, where the first digit 1 represents ferritic
stainless steel, the second and third digits 18 represent the average chromium content, the fourth
digit 6 represents the addition of Ti, and the fifth digit 2 represents ultra-low carbon steel (carbon
content not more than 0.025%).
Example 2.
The unified digital code ISC for both 022Cr11Ti and 022Cr11NiNbTi is S11163.In order to
distinguish, the fifth digit of 022Cr11NiNbTi is changed from 3 to 4, that is, the unified digital code
ISC for 022Cr11NiNbTi is S11164.
A.2.3 For austenitic-ferritic (duplex) stainless steel S2××××, the first four digits are
Prefix letter S. stands for
A.2.4 For austenitic stainless steel S3××××, the first, second and third digits are used
as the steel group, borrowing the three-digit number of the American AISI or UNS
system; the fourth digit indicates that the steel contains special elements, and the fifth
digit indicates the steel type or the serial number of the designation in the same steel
group, see Example 1; but the last four digits of some designations are borrowed from
the last four digits of the American AISI or UNS system (see Example 2). For Cr-Mn-
Ni or Cr-MnNi-N stainless steel, 35× is used as the steel group (see Example 3), and
the third digit × represents the following meanings. 0 -- blank or sequence number; 1 -
- low chromium series (the upper limit of chromium content is generally not more than
16.5%); 2 -- low nickel series (corresponding to the 204 series in the AISI or UNS
system of the United States); 3 -- manganese content is about 5%~8% (corresponding
to the 201 series in the AISI or UNS system of the United States); 4 -- manganese
content is about 7%~10% series (corresponding to the 202 series in the AISI or UNS
system of the United States); 5 -- manganese content is about 10%~13% (manganese
content is higher than the 202 series in the AISI or UNS system of the United States);
6 -- nickel content is lower than the 202 series in the AISI or UNS system of the United
States; 7 -- high chromium and high nickel series; 8 -- molybdenum-added steel series,
9 -- blank or sequence number.
Example 1.
For 06Cr19Ni10, the unified digital code ISC is S30408, where the first digit 3 represents austenitic
stainless steel, the first, second and third digits 304 represent the steel group (corresponding to AISI's
304), the fourth digit 0 represents the sequence number, and the fifth digit 8 represents low carbon
steel (carbon content not more than 0.08%).
Example 2.
For 022Ni25Cr21Mo7N, the unified digital code ISC is S38367, where the first digit 3 represents
austenitic stainless steel, and the last four digits 8367 borrow the last four digits of UNS N08367.
Example 3.
For 12Cr17Mn6Ni5N, the unified digital code ISC is S35350, where 353 represents the Cr-Mn-Ni-
N steel group, the third digit 3 indicates that the manganese content is about 5%~8% (corresponding
to AISI201), the fourth digit 5 indicates the addition of nitrogen, and the fifth digit 0 is the sequence
number.
A.2.5 For martensitic stainless steel S4××××, the first, second and third digits are used
as the steel group, and are arranged using the three-digit number system of the American
AISI and UNS systems; the fourth digit indicates that the steel contains special elements,
and the fifth digit indicates the steel type or the serial number of the designation within
the same steel group, see Examples 1 and 2.
Example 1.
For Y12Cr13, the unified digital code ISC is S41617, where the first digit 4 represents martensitic
stainless steel, the first, second and third digits 416 represent the steel group (corresponding to AISI's
416), the fourth digit 1 represents the sequence number, and the fifth digit 7 represents free-cutting
steel.
Example 2.
For 13Cr13Mo, the unified digital code ISC is S41092, where the first digit 4 represents martensitic
stainless steel, the first, second and third digits 410 represent the steel group (borrowed from AISI's
410), the fourth digit 9 represents the addition of molybdenum, and the fifth digit 2 represents the
sequence number.
A.2.6 For precipitation hardening stainless steel S5××××, the second, third, fourth and
fifth digits are numbered according to the two elements Cr-Ni and their contents, where
the second and third digits represent the average chromium content (in percent), and
the fourth and fifth digits represent the average nickel content (in percent), see Example
1; or the fourth digit represents the average nickel content (in percent), and the fifth
digit represents the distinguishing sequence number of different designations in the
same steel group, see Example 2.
Example 1.
For 06Ni25Cr15Ti2MoAlVB, the unified digital code ISC is S51525, where the first digit 5
represents precipitation hardening stainless steel, the second and third digits 15 represent the average
chromium content, and the fourth and fifth digits 25 represent the average nickel content.
Example 2.
For 05Cr15Ni5Cu4Nb, the unified digital code ISC is S51550, where the first digit 5 represents
precipitation hardening stainless steel, the second and third digits 15 represent the average
chromium content, the fourth digit 5 represents the average nickel content, and the fifth digit 0
represents the sequence number.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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