What makes steel light pole curved into banana shape after welding?

   Many steel light column (steel light pole) customers may meet pole bending problem after welding. some one even meet welding seam twist. some of them can't understand and company us that the steel pole welding machine has problem. following article will give problem explanation and solutions. Please tell us your comments and we can discuss on solution and improvement. 

https://www.goldball.cc/what-makes-steel-light-pole-curved-into-banana-shape-after-welding/