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Weld requirements and quality inspection analysis of straight seam steel pipes
- Aug 28, 2018 -

Weld requirements and quality inspection analysis of straight seam steel pipes

The welds for the intermediate inspection of straight seam steel pipes shall be carried out in accordance with the regulations. Non-destructive testing shall be carried out after the visual inspection has passed. Radiographic and ultrasonic testing shall be carried out after the surface non-destructive testing. The inspected welds may continue to be welded after passing the assessment. . The welded joints of the straight seam steel pipe which are covered by the reinforcing ring or the support pad shall be subjected to 100% ray inspection and shall be covered after passing the test.
First, the basic requirements for the appearance of straight seam steel pipe welds
Before the non-destructive testing of straight seam steel pipes, the inspection of the weld appearance shall meet the requirements. The general requirements for the appearance of straight seam steel welds and the surface quality of welded joints are as follows:
1. No cracks, no fusion, pores, slag inclusions or splashes are not allowed.
2.Straight seam steel pipe is designed to have a temperature of less than -29 degrees, stainless steel and straight seam steel pipe surface with large hardening tendency, and there must be no undercut. Other material pipe weld seam undercut depth should be greater than 0.5 mm, continuous undercut length should be no more than 100 mm, and the total length of the undercut on both sides of the weld is not more than 10% of the total length of the weld.
3.The surface of the weld of straight seam steel pipe shall not be lower than the surface of the pipe. The weld height is not more than 3 mm, which is the larger width of the welded joint group to the rear groove. Straight seam steel pipes that fail to pass the re-inspection results (including those whose initial microstructure results are unqualified and are not allowed to be re-inspected), the supplier may submit the inspections one by one; or re-heat treatment (the number of re-heat treatments shall not exceed two) Accept the acceptance with a new batch.
4.The wrong side of the welded joint should be no more than 10% of the wall thickness and no more than 2 mm. Second, surface non-destructive testing
The principle of non-destructive testing method for the surface of straight seam steel pipe: magnetic powder testing should be used for ferromagnetic material steel pipe; penetration testing should be used for non-ferromagnetic material steel pipe.
For welded joints with a tendency to delay cracking, the surface non-destructive inspection shall be carried out after the welding has been cooled for a certain period of time; for welded joints with a tendency to reheat cracking, the surface non-destructive inspection shall be carried out once after welding and after heat treatment.
The application of surface non-destructive testing is carried out according to the standard requirements. 

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The detection objects and applications are generally as follows:
1. Straight seam steel pipe material quenching tends to be larger than the groove joint of the welded joint.
2. Detection of non-austenitic stainless steel pipe bevels whose design temperature is lower than or equal to minus 29 degrees Celsius.
3, double-sided weldment stipulates the inspection of the roots of the weld after root clearing.
4. When the acetylene flame is used to cut the welding fixture on the alloy pipe with the tendency of hardening, the defect of the grinding part is detected.
5. Inspection of the outer surface quality of straight seam steel pipe materials.
6. Pay attention to the detection of surface defects of butt welds.
7. Pay attention to the detection of surface defects of straight seam steel fillet welds.
8. Pay attention to the surface defect detection of the welded joints of the socket welding and the jumper type three-way branch pipe.
9.Surface defect detection after straight seam steel pipe bending.
Third, straight seam steel pipe ray detection and ultrasonic testing
1. The main object of radiation detection and ultrasonic testing is the butt joint of straight seam steel pipe and the butt joint of butt welded pipe fitting.
2. The non-destructive testing method is selected according to the design documents. For the detection of welded joints of titanium, aluminum and aluminum alloys, copper and copper alloys, nickel and nickel alloys, the radiation detection method should be used.
3. For welds with a tendency to delay cracking, the radiation detection and ultrasonic testing shall be carried out after the welding has been cooled for a certain period of time.
4. When the main pipe in the casing has a ring weld, the weld shall be operated with 100% ray inspection, and the concealed operation may be carried out after the test pressure is passed.