Naming rules for steel materials

Thread Content

Steel is an iron-carbon alloy with a carbon content of 0.0218% to 2.11%. To ensure its toughness and ductility, the carbon content generally does not exceed 1.7%. The main elements of steel, in addition to iron and carbon, include silicon, manganese, sulfur, and phosphorus. There are various methods for classifying steel, and today we will take a look at the naming rules for steel materials. 01 Carbon structural steel: Notation: Q+number+ (quality grade symbol) + (deoxidation method symbol) + (special purpose symbol). ①The steel grade is prefixed with “Q”, which denotes the yield strength of the steel. ②“The number following “Q” indicates the yield strength value, in MPa. For example, Q235 denotes a carbon structural steel with a yield strength (σs) of 235 MPa. ③If necessary, symbols indicating the quality grade and deoxidation method can be indicated after the steel grade. The quality grade symbols are A, B, C, and D respectively. Deoxidation method symbol: F denotes boiling steel ； b denotes semi-dull steel ； Z denotes calm steel ； TZ denotes special calm steel; calm steel does not require a symbol, meaning neither Z nor TZ needs to be indicated. For example, Q235-AF denotes grade A boiling steel. Special-purpose carbon steel: such as bridge steel and marine steel, basically uses the designation method for carbon structural steel, but letters indicating the purpose are added at the end of the steel grade. 02 High-quality carbon structural steel. Notation: digits + (element symbol) + (deoxidation method symbol) + (symbol indicating special用途). ①The first two digits of the steel grade indicate the carbon content of the steel, expressed as a fraction of per ten thousand of the average carbon content. For example, steel with an average carbon content of 0.45% has the grade “45”; this is not a sequential number, so it should not be referred to as ‘steel grade 45’. ②For high-quality carbon structural steel with a high manganese content, the manganese element should be specified, such as 50Mn. ③Boiled steel, semi-killed steel, and high-quality carbon structural steels for special purposes should be specifically indicated at the end of their grade designation; for example, semi-killed steel with an average carbon content of 0.1% has a grade designation of 10b. 03 Carbon tool steel: Notation method: letter T + number + (element symbol) + (quality grade symbol). ①The steel grade is prefixed with “T” to avoid confusion with other types of steel. ②The digits in the steel grade indicate the carbon content, expressed as a percentage of the average carbon content. For example, “T8” indicates an average carbon content of 0.8%. ③For grades with a higher manganese content, “Mn” is indicated at the end of the steel grade, such as “T8Mn”. ④The phosphorus and sulfur contents in high-grade high-quality carbon tool steels are lower than those in ordinary high-quality carbon tool steels; the letter “A” is added at the end of the steel grade to indicate this difference, such as “T8MnA”. 04 Free-cutting steel: Notation: letter Y + number + (element symbol). ①Steel grades are prefixed with “Y” to distinguish them from high-quality carbon structural steel. ②The number following the letter “Y” indicates the carbon content, expressed as a fraction of ten thousand of the average carbon content. For example, a free-cutting steel with an average carbon content of 0.3% has the designation “Y30”. ③For those with a higher manganese content, “Mn” is also indicated after the steel grade, such as “Y40Mn”. 05 alloy structural steel – Notation: (special purpose symbol) + number + symbols and numbers of major alloying elements + symbols of trace alloying elements + (quality grade symbol) + (special purpose symbol). ①The first two digits of the steel grade indicate the carbon content of the steel, expressed as a fraction of ten thousand of the average carbon content; for example, 40Cr. ②The main alloying elements in steel, with the exception of a few micro-alloying elements, are generally expressed as percentages. When the average alloy content