In a piping system, the elbow is a pipe that changes the direction of the pipe. According to the angle, there are 45 ° and 90 ° 180 ° three kinds of the most commonly used, according to the project also includes 60 ° and other non-normal angle elbow. Elbow materials are cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, nonferrous metals and plastics. The way to connect with the pipe is: direct welding (the most commonly used way) flange connection, hot melt connection, fused connection, threaded connection and socket connection. According to the production process can be divided into: welding elbow, stamping elbow, pushing elbow, casting elbow, butt welding and so on. Other names: 90 degrees elbow, right angle bend, love and so on.