In the field of butt welding steel elbows, it looks like a half of the 90 degree elbow.Commonly,the 90 degree elbows can be a seamless elbow or a welded elbow. Bending the two ends of pipe to a angle of 45 degree, it is a 45 degree seamless elbow.
The 45 degree elbows usually are manufactured as LR (Long Radius) elbows.Only in little occasion, for example, very tight place, people use the short radius elbow.Because there is nearly no factory produce such 45 degree short radius elbow, engineers or workers would cut a 90 degree elbow into two 45 degree elbow instead.
As we known in the pipe fitting and elbow standard,the butt welding elbows commonly are 45°,90°,180°. But in the projects,sometimes the engineer or designer may use the elbows which degree are not the standard degree,such as 60°,70°or others.With such elbows,the flow direction in the piping system can be designed as per they need .