GB/T 20878-2024 Stainless steels — Designation and chemical composition
1 Scope
This document specifies the designations and iron and steel code (ISC) of stainless steels and their chemical compositions, and gives the physical properties, designations and comparison tables between ISC and foreign standard designations (or similar designations) of some designations.
The designations and ISC of stainless steels and their chemical compositions specified in this document are applicable to guide the development and revision of product standards for stainless steels (including ingots and semi-finished products).
Note: The content of each element representing the chemical composition of stainless steel in this document is expressed as a mass fraction.
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions 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% (mass fraction) of chromium and not more than 1.2% (mass fraction) of carbon
Note: Stainless steels are divided into corrosion-resistant steel, heat-resistant steel and creep resistant steel according to their main characteristics.
3.2
austenitic stainless steel
stainless steel mainly composed of austenitic structure with face-centered cubic crystal structure in the matrix and strengthened mainly by cold working or nitrogen alloying
3.3
austenitic-ferritic (duplex) stainless steel
stainless steel with a duplex phase structure of austenite and ferrite (with a lesser phase content of at least 25%), which can be strengthened by cold working
3.4
ferritic stainless steel
stainless steel mainly composed of austenitic structure with body-centered cubic crystal structure in the matrix, generally cannot be hardened by heat treatment, but can be slightly strengthened by cold working
3.5
martensitic stainless steel
stainless steel mainly composed of martensitic structure with distorted body-centered cubic crystal structure in the matrix, which can be heat-treated for adjusting mechanical properties
3.6
precipitation hardening stainless steel
stainless steel mainly composed of martensitic or austenitic structure in the matrix, and can be hardened by precipitation hardening (also known as age hardening)
4 General guidelines for determining limits for chemical composition
4.1 Carbon
When the carbon content is greater than or equal to 0.04%, two decimal places are recommended; when the carbon content is equal to or less than 0.030%, three decimal places are recommended.
Foreword II 1 Scope 2 Normative references 3 Terms and definitions 4 General guidelines for determining limits for chemical composition 5 Representation of designations and ISC 6 Designations, ISCs of stainless steels and their chemical compositions and applications Annex A (Normative) Representation of designation and ISC of stainless steel Annex B (Informative) Physical property parameters of some stainless steel designations in this document Annex C (Informative) Comparison between stainless steel designations in this document and stainless steel designations (or similar designations) in foreign standards Bibliography
GB/T 20878-2024 Stainless steels — Designation and chemical composition
1 Scope
This document specifies the designations and iron and steel code (ISC) of stainless steels and their chemical compositions, and gives the physical properties, designations and comparison tables between ISC and foreign standard designations (or similar designations) of some designations.
The designations and ISC of stainless steels and their chemical compositions specified in this document are applicable to guide the development and revision of product standards for stainless steels (including ingots and semi-finished products).
Note: The content of each element representing the chemical composition of stainless steel in this document is expressed as a mass fraction.
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions 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% (mass fraction) of chromium and not more than 1.2% (mass fraction) of carbon
Note: Stainless steels are divided into corrosion-resistant steel, heat-resistant steel and creep resistant steel according to their main characteristics.
3.2
austenitic stainless steel
stainless steel mainly composed of austenitic structure with face-centered cubic crystal structure in the matrix and strengthened mainly by cold working or nitrogen alloying
3.3
austenitic-ferritic (duplex) stainless steel
stainless steel with a duplex phase structure of austenite and ferrite (with a lesser phase content of at least 25%), which can be strengthened by cold working
3.4
ferritic stainless steel
stainless steel mainly composed of austenitic structure with body-centered cubic crystal structure in the matrix, generally cannot be hardened by heat treatment, but can be slightly strengthened by cold working
3.5
martensitic stainless steel
stainless steel mainly composed of martensitic structure with distorted body-centered cubic crystal structure in the matrix, which can be heat-treated for adjusting mechanical properties
3.6
precipitation hardening stainless steel
stainless steel mainly composed of martensitic or austenitic structure in the matrix, and can be hardened by precipitation hardening (also known as age hardening)
4 General guidelines for determining limits for chemical composition
4.1 Carbon
When the carbon content is greater than or equal to 0.04%, two decimal places are recommended; when the carbon content is equal to or less than 0.030%, three decimal places are recommended.
Contents of GB/T 20878-2024
Foreword II
1 Scope
2 Normative references
3 Terms and definitions
4 General guidelines for determining limits for chemical composition
5 Representation of designations and ISC
6 Designations, ISCs of stainless steels and their chemical compositions and applications
Annex A (Normative) Representation of designation and ISC of stainless steel
Annex B (Informative) Physical property parameters of some stainless steel designations in this document
Annex C (Informative) Comparison between stainless steel designations in this document and stainless steel designations (or similar designations) in foreign standards
Bibliography
