IS G3445 STKM11A is the standard material of carbon seamless steel pipe for mechanical parts in Japan.


High quality carbon structural steels are carbon steels with carbon content less than 0.8%. Compared with carbon structural steel, the steel contains less sulphur, phosphorus and non-metallic inclusions, and has excellent mechanical properties.


In addition to carbon (C) and deoxidation, JIS G3445 STKM11A steel also contains a certain amount of silicon (Si) (usually not more than 0.40%) and manganese (Mn) (usually not more than 0.80%, up to 1.20%). It contains no other alloying elements except alloy elements (except residual elements). This steel must ensure chemical composition and mechanical properties. The content of sulfur (S) and phosphorus (P) impurities is usually controlled below 0.035%. If it is controlled below 0.030%, it is called high-quality steel, and its grade should be "A", such as 20A; if P is controlled below 0.025% and S is controlled below 0.020%, it is called high-quality steel, and its grade should be added after the grade. "E" means difference. The content of other residual alloy elements such as chromium (Cr), nickel (Ni), copper (Cu) introduced into steel by raw materials is usually controlled to be less than 0.25% of chromium, 0.30% of nickel and 0.25% of copper. Some brands of manganese (Mn) content of 1.40%, known as manganese steel.


This kind of steel has a large output and is widely used. Usually, it is rolled (forged) into round, square and flat sections, plates and seamless steel tubes. It is mainly used for manufacturing general structural and mechanical structural parts, components and building structural parts, as well as pipelines for conveying fluids.  According to the application requirements, heat treatment (normalizing or quenching) is sometimes required.