45 Degree Elbow

45 degree elbow and 90 ° elbow ,  90 degree elbow forming a right angle and 45 degrees is an obtuse angle. Two 45-degree elbows can not be welded into a 90-degree bend to use, because the stress concentration area is the elbow pipe, expansion and most of the stress deformation during cooling are released at the elbow. Also weld itself to be the weak link, fatigue deformation will soon cause cracking damage, which planted a lot of hidden dangers, so do not at immediate convenience, eventually leading to huge losses.