elbow在管路系统中，弯头是改变管路方向的管件。按角度分，有45°及90°180°三种最常用的，另外根据工程需要还包括60°等其他非正常角度弯头。弯头的材料有铸铁、不锈钢、合金钢、可锻铸铁、碳钢、有色金属及塑料等。与管子连接的方式有：直接焊接（最常用的方式）法兰连接、热熔连接、电熔连接、螺纹连接及承插式连接等。按照生产工艺可分为：焊接弯头、冲压弯头、推制弯头、铸造弯头、对焊弯头等。其他名称：90度弯头、直角弯、爱而弯等。
Elbow in the pipeline system, elbow is a pipe fittings to change the direction of the pipeline. According to the angle, 45 degrees and 90 degrees 180 degrees are the most commonly used, and other abnormal angle elbows such as 60 degrees are also included according to the engineering requirements. Elbows are made of cast iron, stainless steel, alloy steel, malleable iron, carbon steel, non-ferrous metals and plastics. The ways to connect with pipes are: direct welding (the most commonly used way) flange connection, hot melt connection, electric melt connection, threaded connection and socket connection. According to the production process, it can be divided into welding elbow, punching elbow, pushing elbow, casting elbow, butt welding elbow and so on. Other names: 90 degree elbow, right angle bend, love and bend, etc.