Naming rules for seven commonly used types of steel

Thread Content

Steel is a general term for iron-carbon alloys whose carbon content ranges from 0.02% to 2.11% by mass. In actual production, steel often contains different alloying elements depending on its intended use, such as manganese, nickel, vanadium, etc. Today, steel has become one of the most widely used materials in the world, thanks to its low cost and reliable performance. So, does everyone know the naming rules for steel? Today, I’d like to introduce that in our country, the classification of steel is based on its intended uses. 1. Carbon structural steel. Notation method: Q + number + (quality grade symbol) + (deoxidation method symbol) + (symbol indicating special use). ① The letter “Q” at the beginning of the steel grade designation represents the yield point of the steel. ② The number following “Q” indicates the value of the yield point, measured in MPa. For example, Q235 indicates a carbon structural steel with a yield point (σs) of 235 MPa; ③ When necessary, symbols indicating the quality grade and deoxidation method can be added after the steel grade. The quality grade symbols are A, B, C, and D respectively. Symbols for deoxidation methods: F denotes rimmed steel; b indicates semi-killed steel; Z represents killed steel; TZ stands for special killed steel. For killed steel, no symbol is required; thus, neither Z nor TZ needs to be indicated. For example, Q235-AF indicates grade A rimmed steel. Special-purpose carbon steels: Examples include bridge steel and shipbuilding steel. Basically, the designation method for carbon structural steels is used; however, letters indicating the purpose are added at the end of the steel grade designation. II. High-quality carbon structural steel. Notation: digits + (element symbol) + (deoxidation method symbol) + (symbol indicating special用途). ① The first two digits of the steel grade indicate the carbon content in the steel, expressed as a percentage of ten-thousandths of the average carbon content. For example, for steel with an average carbon content of 0.45%, the steel grade is “45”. This is not a serial number; therefore, it should not be referred to as “Grade 45 steel”. ②For high-quality carbon structural steel with a relatively high manganese content, the manganese element should be indicated, such as 50Mn. ③Killed steel, semi-killed steel, and high-quality carbon structural steel for special purposes shall be specifically indicated at the end of the steel grade designation. For example, a semi-killed steel with an average carbon content of 0.1% has the steel grade designation 10b. III. Carbon tool steels
Notation method: Letter T + number + (element symbol) + (quality grade symbol). ① The steel grade is prefixed with “T” to prevent confusion with other types of steels. ②The numbers in the steel grade indicate the carbon content, expressed as a percentage of thousandths of the average carbon content. For example, “T8” indicates that the average carbon content is 0.8%. ③For steels with a relatively high manganese content, “Mn” is indicated at the end of the steel grade designation; for example, “T8Mn”. ④The phosphorus and sulfur contents in high-grade premium carbon tool steel are lower than those in ordinary premium carbon tool steel. The letter “A” is added at the end of the steel grade designation to distinguish it; for example, “T8MnA”. 4) Free-cutting steel. Notation: Letter Y + number + (element symbol). ① The steel grade is prefixed with “Y” to distinguish it from high-quality carbon structural steel. ②The number following the letter “Y” indicates the carbon content, expressed as parts per ten thousand of the average carbon content. For example, free-cutting steel with an average carbon content of 0.3% is designated as “Y30”. ③For steels with a relatively high manganese content, “Mn” is also indicated after the steel grade, such as “Y40Mn”. V. Alloy structural steels
Notation method: (symbol for special purpose) + digit(s) + symbol(s) and digit(s) of main alloying elements + symbol(s) of trace alloying elements + (symbol for quality grade) + (symbol for special purpose).
① The first two digits at the beginning of the steel grade indicate the carbon content in the steel, expressed as a percentage of ten-thousandths of the average carbon content; for example, 40Cr. ②The main alloying elements in steel, except for certain microalloying elements, are generally expressed as percentages. When the average alloy content