Basic requirements for the appearance of
straight seam steel pipe welds
1. Surface of welded joints: A. No cracks, unfused, pores, slag inclusions, and splashes are allowed. B. The welding seam surface of pipelines with design temperature lower than -29 degrees, stainless steel and alloy steel pipelines with greater hardening tendency shall not have undercut. The undercut depth of the welding seam of other materials shall be greater than 0.5mm, the length of the continuous undercut shall not be greater than 100mm, and the total length of the undercut on both sides of the weld shall not be greater than 10% of the total length of the weld. C. The surface of the weld shall not be lower than the surface of the pipe. The excess height of the welding seam shall not be greater than 3mm, (the maximum width of the rear groove of the welded joint group). D. The wrong side of the welded joint should be no more than 10% of the wall thickness and no more than 2mm.
2. Surface non-destructive testing: Principles for selection of surface non-destructive testing methods for
straight seam steel pipes: Magnetic particle testing should be used for ferromagnetic steel pipes; penetration testing should be used for non-ferromagnetic steel pipes. For welded joints prone to delayed cracking, the surface NDT shall be carried out after the welding cooling time; for welded joints prone to reheat cracks, the surface NDT shall be carried out once after welding and after heat treatment. The application of surface non-destructive testing is carried out by the standard requirements. The detection objects and applications are generally as follows: A. Inspection of the outer surface of the pipe material. B. Detection of surface defects of important butt welds. C. Detection of surface defects of important fillet welds. D. Surface defect detection of welded joints of important socket welding and bridging tee branch pipes. E. Surface defect detection after pipe bending. F. Groove detection of welded joints with large quenching tendency of materials. G. Detection of non-austenitic stainless steel pipe grooves whose design temperature is lower than or equal to minus 29 degrees Celsius. H. Double-sided weldments require the root-cleaning weld to be tested after root-cleaning. H. When the oxyacetylene flame is used to cut the welding fixture on the alloy pipe with the tendency to harden, the defect detection of the grinding part.
3. Radiographic inspection and inspection: The main objects of radiographic inspection and inspection are the butt joints of
straight seam steel pipes and the butt joints of butt welded pipe fittings. The non-destructive testing method is selected according to the provisions of the design documents. For the inspection of welded joints of titanium, aluminum, and aluminum alloys, copper and copper alloys, nickel, and nickel alloys, the radiographic inspection method should be selected. For welds prone to delayed cracking, the radiographic inspection and inspection shall be carried out after the welding cooling time. When there is a girth weld in the main pipe in the jacket, the weld should be tested by 100% radiography, and the concealed operation can only be carried out after passing the pressure test. The welded joints on the pipeline covered by the reinforcement ring or the support pad shall be 100% radiographically inspected, and can be covered again after passing the test. For the welds specified for intermediate welding inspection, the non-destructive testing shall be carried out after the visual inspection is passed, and the radiographic and wave testing shall be carried out after the surface non-destructive testing. The inspected welds shall be qualified before continuing welding.
The production temperature of
straight seam steel pipe is very important:
In the process of producing
straight seam steel pipes, it is necessary to strictly control the temperature, to ensure the reliability of welding. If the temperature is too low, the welding position may not reach the temperature required for welding. When most of the metal structure is still solid, it is difficult for the metals at both ends to penetrate and bond together. At that time, when the temperature was too high, a lot of metal in the welding position was in a molten state. The texture of these parts was very soft, and some of them were fluid, and they might have molten droplets. When such metal drips, the same There is not enough metal to interpenetrate. And when welding, there will be some unevenness with the weld to form a hole. Therefore, the manufacturer of integrated sewage treatment equipment reminds us that the temperature must be strictly controlled in the production process of the straight seam welded pipe. Regular manufacturers have very good control technology, so the temperature control requirements can be achieved in the production, and the products are guaranteed, so we need to buy
straight seam welded pipes from regular manufacturers.
