Steel elbows are metal pipe fittings used to change the direction of pipeline on carbon steel pipes. The connection methods include threaded and welded. In terms of angles, there are three commonly used ones: 45°, 90°, and 180°, as well as other non-standard angles like 60° according to engineering requirements. The materials for elbows include cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metals, and plastics. Connection methods to pipes include direct welding (commonly used), flange connection, hot melt connection, electric fusion connection, threaded connection, and socket-weld connection, etc. They can be categorized by production process into: welded elbows, stamped elbows, extruded elbows, cast elbows, etc. Other names include 90-degree elbow, right-angle bend, and ell bend, etc.