Spiral pipe forming methods and causes internal stress

Spiral welded steel tube in the petrochemical, heat pipe network and urban water supply and drainage engineering and other fields have a wide range of applications, especially in the long-distance transportation of oil pipeline and natural gas pipelines and construction piling is more widely used. Oil, gas pipe spiral welded steel pipe almost all, in addition, used in building piling pipe well. With high security, durability and economic rationality. Since the diameter of the spiral welded steel sheet width generally not limited, by a variety of different specifications of the plate width coil manufacture, so no wide plate width of the plate. This gives plate manufacturing, transportation convenience, the use of flat steel strip ratio much lower price, suitable for China's actual situation. Spiral welded steel pipe there is a problem produce elastic recovery after welding steel pipe, steel pipe previously exposed to the equivalent one circumferential tensile stress, the stress will produce stress corrosion and reduced ability of the pressure tube.

Spiral welded steel pipe using a continuous forming, welding fabrication method, is now widely used within and outside deck holds two kinds of molding method.

And the inner forming roll carrier roller (or external brake rollers) is composed of a molded plate along the direction shown by the arrows into the forming device, while forming the side weld. Molding can be obtained by adjusting the different sizes of the pipe. In order to prevent excessive bending, forming rolls three points of contact with the plate height is generally not much difference, manufacturers have adopted an insufficient amount molding, pipe made ​​within the radius of curvature is to rely on roll (or external hold rolls) formed by the radius of curvature that in within each roll (or external hold rolls) in the elastic and plastic plates are actually mixed deformation. Spiral welded steel pipe cut open along the generatrix direction, there must be a certain amount of circumferential openings, namely the existence of certain steel pipe bomb complex quantity, steel residual stress exists. Since the existence of internal stress, steel external tensile stress, so this will reduce the ability of the pressure tube, increasing the external pipe corrosion, to adversely affect the use of steel.