Steel square tube top bending processing In the pipeline system, the elbow is a pipe fitting that changes the direction of the pipeline. It is often connected with two pipes with the same or different nominal diameters to make the pipeline turn at a certain angle. According to the angle, there is 45°. And 90 °, 180 ° three super-common, in addition to engineering needs, including 60 ° and other abnormal angle elbow.