Classification of special steel products
Carbon steel, also called carbon steel, is an iron carbon alloy with a carbon content of less than 2% wc. Carbon steel, in addition to carbon, usually contains a small amount of silicon, manganese, sulfur and phosphorus.Carbon steels can be divided into three categories: carbon structural steel, carbon tool steel and free cutting structural steel by use. Carbon structural steel can be divided into two kinds of structural steel and machine building steel.
According to the carbon content of the steel can be divided into low carbon steel (WC = 0.25%), steel (0.25% WC 0.6%) and high carbon steel (wc>0.6%) according to the content of phosphorus and sulfur can be divided into ordinary carbon steel (carbon steel with phosphorus, sulfur, high quality carbon steel (P), low sulfur and high quality (steel) phosphorus, sulfur lower).In general, the higher carbon content in carbon steel, the higher hardness and higher strength, but lower plasticity. This kind of steel is mainly carbon steel to ensure mechanical properties, so the brand reflects its mechanical properties, represented by the Q+ number, "Q" to "yield point bend" word Pinyin prefix, a digital representation of the yield point value, such as Q275 said the yield point is 275MPa. If the grades are marked with letters A, B, C and D, the quality grade of steel is different. The quantity of S and P is reduced, and the quality of steel is improved. If the letter "F" is marked behind the grade, it is "boiling steel". The label "B" is a semi killed steel, and no "F" or "B" is used as a killed steel. For example, Q235-A = F indicates a yield point of 235MPa for grade a rimmed steel, and Q235-c represents a C grade killed steel with a yield point of 235MPa.
Carbon structural steels are normally used directly under heat supply without heat treatment. The mass fraction of Q195, Q215, Q235 are usually of low carbon steel, good welding performance, good plasticity and toughness, a certain strength, often rolled into a sheet, steel, welded steel pipe, used for bridges, buildings and general manufacturing rivet, screw and nut parts etc.. Q255 and Q275 mass fraction of carbon steel is slightly high, high strength, good plasticity and toughness, can be welded steel, steel rolling, usually forming and plate structure and simple manufacturing machinery, connecting rod, gear coupling, pins and other parts. Plain carbon steel high carbon steel is basically contains alloy elements, the carbon content in the range of 0.65% ~ 1.35%, the production of low cost, easy to obtain raw materials, good machinability, after treatment can obtain high hardness and high wear resistance, so the steel is widely used to manufacture various. Cutting tool, mold, measuring tools.But the red hardness difference of this kind of steel, that is, when the working temperature is greater than 250 degrees, the hardness and wear resistance of steel will decline rapidly, and lose their ability to work. In addition, if carbon tools steel is made into larger parts, it is difficult to harden, and deformation and crack are easy to occur. This kind of steel must ensure both chemical composition and mechanical properties. The number is two digits by the average mass fraction of carbon steel in the 000 fraction (W C * 10000). For example, steel 45 shows the average mass fraction of carbon in steel is 0.45%; 08 steel indicates the average mass fraction of carbon in steel is 0.08%.
