① The grades of alloy structural steel are indicated by Arabic numerals and standard chemical element symbols.
Use two Arabic numerals to represent the average carbon content (in tens of thousands) and put it at the head of the brand.
The expression method of alloy element content is: when the average content is less than 1.50%, only elements are indicated in the brand, and generally the content is not indicated; When the average alloy content is 1.50% ～ 2.49%, 2.50% ～ 3.49%, 3.50% ～ 4.49%, 4.50% ～ 5.49%,… Write 2, 3, 4, 5… After the alloy element.
For example, when the average content of carbon, chromium, manganese and silicon is 0.30%, 0.95%, 0.85% and 1.05% respectively, the brand of alloy structural steel is “30CrMnSi” when the content of S and P is ≤ 0.035% respectively.
High grade and high-quality alloy structural steel (s and P contents ≤ 0.025% respectively), and the symbol “a” is added at the end of the brand
For example: “30CrMnSiA”.
Special grade high-quality alloy structural steel (s ≤ 0.015%, P ≤ 0.025%), add the symbol “e” at the end of the brand, for example: “30crm nsie”.
For the special alloy structural steel brand, the symbol representing the purpose of the product specified in Table 1 shall be added to the head (or tail) of the brand. For example, the steel grade of 30CrMnSi steel for riveting screw is ml30crmnsi.
② The designation of alloy spring steel is the same as that of alloy structural steel.
For example, the grade of spring steel with the average content of carbon, silicon and manganese of 0.60%, 1.75% and 0.75% respectively is expressed as “60Si2Mn”. For high-grade high-quality spring steel, the symbol “a” is added at the end of the brand, and its brand is expressed as “60Si2MnA”.