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Classification of steel
Steel according to the chemical composition is divided into carbon steel (carbon steel) and alloy steel two categories. Carbon steel is an alloy obtained from pig iron smelting. In addition to iron and carbon as its main components, it also contains a small amount of manganese, silicon, sulfur, phosphorus and other impurities. Carbon steel has certain mechanical properties, good process performance, and low price. Therefore, carbon steel has been widely used. However, with the rapid development of modern industry and science and technology, the performance of carbon steel can not fully meet the needs, so people have developed a variety of alloy steel.
Steel is an alloy with iron and carbon as the main components, and its carbon content is generally less than 2.11 percent. Steel is an extremely important metal material in economic construction.
Steel according to the chemical composition is divided into carbon steel (carbon steel) and alloy steel two categories. Carbon steel is an alloy obtained from pig iron smelting. In addition to iron and carbon as its main components, it also contains a small amount of manganese, silicon, sulfur, phosphorus and other impurities. Carbon steel has certain mechanical properties, good process performance, and low price. Therefore, carbon steel has been widely used. However, with the rapid development of modern industry and science and technology, the performance of carbon steel can not fully meet the needs, so people have developed a variety of alloy steel. Alloy steel is a multi-component alloy obtained by purposefully adding certain elements (called alloying elements) on the basis of carbon steel. Compared with carbon steel, the performance of alloy steel has been significantly improved, so it is widely used.
Due to the wide variety of steel, in order to facilitate the production, storage, selection and research, the steel to be classified. According to the use, chemical composition and quality of steel, steel can be divided into many categories:
One. Classification by use
According to the use of steel can be divided into structural steel, tool steel, special performance steel three categories.
Structural steel: 1. Steel used as various machine parts. It includes carburized steel, tempered steel, spring steel and rolling bearing steel.
2. Steel used as engineering structure. It includes carbon steel in A, B, special class steel and ordinary low alloy steel.
Tool steel: Steel used to make various tools. According to the use of different tools can be divided into cutting tool steel, die steel and gauge steel.
Special performance steel: steel with special physical and chemical properties. Can be divided into stainless steel, heat-resistant steel, wear-resistant steel, magnetic steel and so on.
II. Classification by chemical composition
According to the chemical composition of steel can be divided into carbon steel and alloy steel two categories.
Carbon steel: according to the carbon content can be divided into low carbon steel (carbon content ≤ 0.25); medium carbon steel (0.25 <carbon content <0.6); high carbon steel (carbon content ≥ 0.6).
Alloy steel: according to the content of alloy elements, it can be divided into low alloy steel (total content of alloy elements ≤ 5%); Medium alloy steel (total content of alloy elements = 5%-10%); High alloy steel (total content of alloy elements> 10%). In addition, according to the different types of main alloying elements contained in steel, it can also be divided into manganese steel, chromium steel, chromium nickel steel, chromium manganese titanium steel and so on.
Three. Classification by quality
According to the content of harmful impurities of phosphorus and sulfur in steel, it can be divided into ordinary steel (phosphorus content ≤ 0.045, sulfur content ≤ 0.055; Or phosphorus and sulfur content ≤ 0.050); High quality steel (phosphorus and sulfur content ≤ 0.040); High quality steel (phosphorus content ≤ 0.035, sulfur content ≤ 0.030).
In addition, according to the type of smelting furnace, the steel is divided into open hearth steel (acid open hearth, alkaline open hearth), air converter steel (acid converter, alkaline converter, oxygen top blown converter steel) and electric furnace steel. According to the degree of deoxidation during smelting, the steel is divided into rimmed steel (incomplete deoxidation), killed steel (relatively complete deoxidation) and semi-killed steel.
When naming steel products, steel mills often combine the three classification methods of use, composition and quality. Such as the steel is called ordinary carbon structural steel, high quality carbon structural steel, carbon tool steel, high quality carbon tool steel, alloy structural steel, alloy tool steel and so on.
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