How to indicate the grade of structural steel

The representation method of most grades of structural steel complies with the regulations of the SAE (Society of Automotive Engineers) system, and also uses four digits to represent the grade. The first two digits indicate the type of steel, and the last two digits indicate the average carbon mass fraction in the steel × 10°.

(1) Carbon structural steel rods use 10 to represent carbon structural steel, for example: 1015 represents carbon structural steel with an average carbon mass fraction of 0.15%.

(2) Carbon structural steel bars with higher manganese content use 15 to represent carbon structural steel with higher manganese content. For example: 1513 represents the average carbon mass fraction of 0.13%. Carbon structural steel with higher manganese content.

(3) Free-cutting structural steel 11 means sulfur-based free-cutting structural steel, 12 means sulfur-phosphorus composite free-cutting structural steel, 12L means lead-sulfur composite free-cutting structural steel, such as: 1108, 1211, 12L13, etc.

(4)Alloy structural steel There are many categories and grades of alloy structural steel. For example, the same chromium steel has different grades due to different contents. The chromium steel with a chromium mass fraction of 0.27% to 0.65% is grade 50××, and the chromium steel with a chromium mass fraction of 0.8% to 1.05% is grade 51. ××. The letter B can be inserted between the brand numbers of boron-containing alloy structural steel, such as 50B44.
(5) Spring steel Spring steel can be divided into carbon spring steel and alloy spring steel. For example, 1050 is carbon spring steel, 5160 is alloy spring steel, 51B60 is manganese-containing alloy spring steel, etc.

(6) The brand of structural steel (H steel) with guaranteed purity is added with the suffix letter H at the end of the original brand, such as 1038H, 94B30H, etc., but the chemical composition is slightly different from the original brand.

(7) Bearing steel
1. The grade of high-carbon bearing steel is represented by a five-digit number. The first digit 5 ​​represents chromium steel; the second digit represents the average chromium mass fraction, that is: 0w (Cr) is 0.5%, 1—w (Cr) is 1.0%, 2—w (Cr) is 1.45%, The third, fourth and fifth digits represent the average carbon mass fraction × 10°. For example: Grade 51100 means high carbon medium chromium bearing steel with an average carbon mass fraction of 1.00% and an average chromium mass fraction of 1.00%.

2. The method of expressing the grade of high permeability bearing steel is the same as that of the ISO standard, for example: 100CrMnSi6-4.

structural steel