The standard refers to and adopts ISO4948/1 First Part of Steels-Classification: Steel can be classified into Alloy Steel and Non-alloy Steel on the Chemical Composition and Second Part of Steels-Classification: Steel can be classified into Alloy Steel and Non-alloy Steel on Chief Quality Grade, Performance and Characteristics
Part I Steel-Classification on Chemical Composition
1. Subject content and application scope
The standard specifies the ground rule of steel-classification on chemical composition in the first part, and indicates the basic threshold value of alloying element in non-alloy steel, low-alloy steel and the alloy steel.
The first part of standard is applicable to classify steel on the chemical composition.
2. Terms
2.1 Steel
Steel indicates the material, which is mainly composed of iron with carbon content lower than 2%.
Note: maybe there are more than 2% carbon contents in the chrome steel; which is the dividing line between steel and cast-iron.
3. Classification
3.1 Steel-classification on chemical composition:
Non-alloy steel;
Low-alloy steel;
Alloy steel.
3.1.1 Non-alloy steel, low-alloy steel and alloy steel is classified on chemical composition, and the alloying element content should conform to the following provisions;
3.1.1.2 When the standard, technical requirement and order offer the minima of the chemical composition during steel smelting, then the minima of chemical composition should be taken as the specified content to classify the steel.
3.1.1.3 When the standard, technical condition and order offers no chemical composition of the steel, then the manufacturer's smelting value can be regarded as the specified content to classify the steel; in special case, when only assay value of the finished steel product is provided, it can be regarded as specified content to classify the steel; however, when it is in the critical condition, then the permissible variation of the chemical composition should be taken into consideration, and the original steel-classification should be reconfirmed.
3.1.1.4 Those residual elements adding to the steel as non-alloying elements, which is specified or existed in the standard, technical requirement and order in the real steel, shouldn't be considered as the specified content to classify steel.
3.1.2 According to the specified element content percentage in Clause 3.1.1, if any element is within relevant threshold value, then the steel can be classified as non-alloy steel, low-alloy steel and alloy steel. According to the specified element content percentage in Clause 3.1.1, if any element is within relevant threshold value, then the steel can be classified as non-alloy steel, low-alloy steel and alloy steel.
Approved by China State Bureau of Quality & Technical Supervision on Dec.13,1991; and implemented on Oct.1, 1992.
GB/T 13304-1991 The following standards are cited：
