Considering the influence of pipe welding quality factors, first the control of raw materials, there are several factors that affect the quality of raw materials are the main disadvantages? Appearance and geometric scale error of steel strip, unstable mechanical properties of big three aspects, therefore, from the three aspects of key control.
1, the mechanical properties of the steel pipe quality, welded steel pipe commonly used for carbon structural steel, the main brands are Q195, Q215, Q235, SPCC, SPHC, SS400 and many other. Because of the high yield point and tensile strength of the steel strip, the forming of the steel belt is difficult. Especially when the pipe wall is thicker, the elasticity of the material is large, and there is a large deformation stress in the welding of the steel pipe, and the weld seam is easy to crack. When the tensile strength of steel strip exceeds 635 MPa and elongation is less than 10%, the weld seam of steel strip is prone to crack during welding. When the tensile strength is less than 30 0MPa, the steel strip in the process of forming because of soft material, the appearance of simple wrinkles. It can be seen that the mechanical properties of the material have great influence on the quality of the steel pipe, and the quality of the steel pipe can be effectively controlled from the strength of the data.
2, the appearance of steel disadvantages on steel pipe quality strip appearance shortcomings see have camber, wavy, slitting edge of camber and wavy, usually presented in cold strip rolling process, is by the amount of pressure control with the formation of. In the process of steel tube forming, the sickle bend and wave shape will lead to the deviation or overturn of the strip, which will make the weld of the steel pipe lap welding and affect the quality of the steel pipe. The edge of the steel strip (that is, the edge of the steel strip appears jagged and uneven) is usually presented on the longitudinal shear band, which is caused by the blunt or non sharp cutting of the disc edge of the slitting machine. Because the steel strip gnawing edge, from time to time showing partial lack of meat, so that the steel strip in welding prone to cracks, cracks and affect the quality of weld stability.
3, the strip geometric scale on the pipe quality when the strip width is less than the promised error, pipe extrusion pressure decreases, the steel pipe weld seam welding is not strong, showing cracks or open tube; when the strip width is greater than the promise when the error of pressure pipe is added, showing pipefish, lapwelded or burrs and welding defect in weld steel pipe. Therefore, the width of the steel belt not only affects the accuracy of the outer diameter of the steel pipe, but also seriously affects the appearance quality of the steel pipe. Requests for the same section of the wall thickness difference does not exceed the specified value of the steel tube wall thickness, which request high degree of uniformity, thickness of strip will be shaken, the same volume of strip thickness difference exceeds the value promised to transfer products of steel pipe wall thickness difference, so that a large number of steel tube thickness beyond the promised error rejection.