The starting material for fifittings shall be fully killed steel, consisting of forgings, bars, plates, sheet, and seamless or fusion-welded tubular products with fifiller metal added and shall conform to the chemical requirements Carbon steel elbow is a metal pipe fitting that changes the direction of the carbon steel pipe.Connection mode: wire buckle and welding.According to the Angle points, there are 45° and 90°180° three more commonly used, in addition, according to the needs of the project also includes 60° and other abnormal Angle elbow.Elbow materials are cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metal and plastic, etc.The ways of connecting with the pipe are: direct welding (the more common way) flange connection, hot melt connection, electric melt connection, thread connection and socket connection, etc.According to the production process can be divided into: welding elbow, stamping elbow, push elbow, casting elbow and so on.Other names: 90 degree bend, right Angle bend, etcCarbon steel elbow can be divided into long radius elbow and short radius elbow according to its radius of curvature.Long radius elbow refers to the outer diameter of the pipe whose radius of curvature is equal to 1.5 times, i.e., R= 1.5d.A short radius elbow means that its radius of curvature is equal to the outside diameter of the pipe, i.e. R= 1.0d.(D is elbow diameter, R is radius of curvature.D can also be expressed in multiples.)According to the pressure grade, there are about 17 kinds of pipes, which are the same as the American standard. They are Sch5s, Sch10s, Sch10, Sch20, Sch30, Sch40s, STD, Sch40, Sch60, Sch80s, XS.Sch80, Sch100, Sch120, Sch140, Sch160 and XXS, among which STD and XS are the two most commonly used ones.According to the Angle of the elbow, there are 45° elbows, 90° elbows and 180° elbows.