Residual stress in spiral welded pipe

Spiral welded pipe for its manufacturing processes mature and lower cost, which is mainly for fluid pipeline.

Commonly used continuous molding manufacturing spiral welded pipe using submerged arc welding method. Molding method within the deck and outside hold two kinds. As these two molding methods are generally insufficient amount of molding, after the kind of the control steel, has a great residual stress, reduces the ability of the pressure of the steel pipe.

Spiral welded steel pipe widely used in the field of petrochemical, heat pipe network and urban water supply and drainage works, million more commonly used in the oil pipeline and natural gas pipeline in the long-distance transmission. Oil and gas field pipeline network almost all spiral steel pipe, with high security, durability and economic rationality. Spiral welded steel pipe diameter is generally not limited to the width of the plate, by a variety of different specifications of the plate width coil manufacturing, transportation convenience, with steel pipe used to be much lower than the flat steel price for our actual situation. There is a problem of the spiral welded steel pipe after welding steel elastic recovery, equivalent to the pipe pre withstand a circumferential tensile stress, the stress will produce stress corrosion and to reduce the bearing capacity of the steel pipe.

Spiral welded steel using continuous molding, welding method of manufacture, which is currently widely used within the deck and outer replaceable molding method.

Forming rolls and the inner carrier roller to hold roller is composed of a forming device, while forming and welding. Different size can be obtained by adjusting type steel pipe. In order to prevent excessive bending, the height of the three forming roller and steel plate contact points are generally not that much difference, manufacturers are using less than the amount of molding, pipe radius of curvature radius of curvature is relying on to hold the roll formed within the Order of the roll or guarantee, including hold outside the Order of the roll or roll steel tube international elastic and plastic mixed deformation. Along the generatrix direction of the spiral steel pipe after welding Paokai, there must be a certain peripheral to the amount of opening, i.e. the steel pipe there is a certain amount of elastic recovery, the existence of residual internal stress steel pipe. Due to the existence of internal stress, the steel pipe external tensile stress, and therefore, this will reduce the bearing capacity of the steel pipe to exacerbate stress corrosion of the steel pipe external to adversely affect the use of the steel pipe.

Weled steel pipe specification, Standard and identification

Welded steel pipe (steel pipe manufactured with a weld) is a tubular product made out of flat plates, known as skelp, that are formed, bent and prepared for welding.