GB/T 222-2025 Steels and alloys - Permissible deviations of product analyzed chemical composition
1 Scope
This document specifies the permissible deviations of chemical composition of products (including billets) of non-alloy steel, low-alloy steel, alloy steel, stainless steel, heat-resistant steel, deformation corrosion-resistant alloy and superalloy from the limit value of the specified melting chemical composition, and provides the definitions of related terms.
This document is applicable to product standards of steel and alloy and the provisions of technical agreements on the permissible deviations of product analyzed chemical composition.
2 Normative references
The following documents contain provisions 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 (including any amendments) applies.
GB/T 20066 Steel and iron - Sampling and preparation of samples for the determination of chemical composition
GB/T 20566 Terminology of steel and alloy
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 20566 and the following apply.
3.1
heat analysis; cast analysis; ladle analysis
chemical analysis of the specimens produced from sample ingots of steel and alloy taken during smelting
Note: The analysis results indicate the average chemical composition of steel and alloy in the same furnace.
3.2
product analysis
chemical analysis of samples from processed products (including blanks)
Note: Due to the uneven distribution (segregation) of elements generated in the crystallization process of steel and alloy, the composition values of product analysis are sometimes different from those of melting analysis. Product analysis is mainly used to verify chemical composition, also known as validation analysis.
3.3
permissible deviations of product analyzed chemical composition
permissible deviation value of product analysis (3.2) from the limit value of melting analysis (3.1) specified in the standard
4 Sampling and preparation methods of samples for product analysis
Sampling and preparation of samples for product analysis shall be carried out in accordance with the method specified in GB/T 20066 or other methods specified by both parties through consultation.
5 Permissible deviations of product analyzed chemical composition
5.1 The permissible deviations of product analyzed chemical composition shall meet the requirements of Tables 1~5. Table 1 applies to non-alloy steel and low-alloy steel, Table 2 applies to alloy steel (excluding stainless steel and heat-resistant steel), Table 3 applies to stainless steel and heat-resistant steel, Table 4 applies to deformation corrosion-resistant alloy, and Table 5 applies to high-temperature alloys. The deviation values in Table 1 and Table 2 apply to steel (or billet) with a cross-sectional area of not more than 65000 mm2, and the permissible deviation values of chemical composition of steel (or billet) with a cross-sectional area of more than 65000 mm2 may be appropriately increased. The specific values can be found in Tables A.1 and A.2 in Annex A, and can also be determined by both parties upon mutual agreement.
5.2 The residual elements specified in the product standard are not applicable to the permissible deviations of the products chemical composition specified in Tables 1~5.
5.3 If the requirements on the permissible deviations of one or several elements in the product chemical composition vary from those in Tables 1~5, the product standard shall apply.
5.4 When the product standard adopts the permissible deviation of the product chemical composition specified in this document, only one table, rather than two, can be used for the permissible deviation of the chemical composition of a steel (or alloy).
5.5 The values obtained from product analysis shall not exceed the upper limit plus the positive deviation of the chemical composition (melting analysis) limit value specified in the product standard, nor shall it exceed the lower limit minus the negative deviation of the chemical composition (melting analysis) limit value specified in the product standard; In the product analysis of the same heat number, only a single deviation is allowed for the same element, and the upper deviation and the lower deviation cannot show at the same time. When only the upper limit is specified for an element, only the upper deviation is allowed.
Contents
Foreword I
1 Scope
2 Normative references
3 Terms and definitions
4 Sampling and preparation methods of samples for product analysis
5 Permissible deviations of product analyzed chemical composition
In % (mass fraction)
Annex A (Informative) Permissible deviations of recommended chemical compositions of non-alloy steel, low-alloy steel and alloy steel with large cross-section size
