An elbow (also known as a 90-degree bend or right-angle bend) is a pipe fitting used in piping systems to change the direction of pipes, primarily in plumbing installations. These fittings are commonly available in 45°, 90°, and 180° angles, with additional non-standard angles such as 60° for special engineering requirements. An elbow is defined as having a bending radius less than or equal to 1.5 times the pipe diameter.
Elbows are made from a variety of materials, including cast iron, malleable cast iron, stainless steel, alloy steel, carbon steel, non-ferrous metals, and plastics. Connection methods include direct welding, flange connection, hot-melt connection, electrofusion connection, threaded connection, socket connection, and clamp connection. They are also categorized by manufacturing process, such as welded elbows, stamped elbows, push-formed elbows, and cast elbows. The main standards followed are GB/T12459-2017 "Steel Butt-Welded Pipe Fittings" and ASME B16.9.
The main production processes include hot pushing forming, stamping forming, and medium plate welding. Among them, the hot pushing process, characterized by uniform wall thickness and continuous operation, has become the main production method for carbon steel elbows. Modern processes have introduced intelligent temperature control systems and multi-station collaborative forming technology to improve processing accuracy and efficiency. The products need to undergo surface shot peening treatment, pre-applied anti-corrosion layer with fiber cloth, and rotary spraying process to ensure that the coating thickness deviation does not exceed ±0.2mm.
