The steel coils are unfolded and leveled by the mill equipment. And they are sent to the forming machine in a certain angle. Supplemented by a certain angle, the continual pipes are formed in the principle of three-roll rolling machine. Continual spiral welding is welded by submerged-arc welding machine. When the uncoiling, coil detaching, leveling, steel cutting and welding are working, the host machine needs to stop and wait.