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How to check the quality of q345b welded pipe?

Q345B welded pipe is a straight seam welded pipe made of q345b steel plate. Generally used to transport low-pressure fluids, it is made of q345b steel; it can also be made of other mild steels that are easy to weld. The q345b welded pipe needs to be subjected to water pressure, bending, flattening and other experiments, and has certain requirements on the surface quality. Usually, the delivery length is 4-10m, and it is often required to deliver to a fixed length (or multiple feet).

Quality inspection method

1) Judging from the surface, that is, in the visual inspection. The appearance inspection of welded joints is a simple, easy and widely used inspection method, and it is an important part of finished product inspection. The inspection is generally carried out by visual inspection, with the help of standard templates, gauges, magnifying glasses and other tools. If the weld surface is defective, there may be a defect inside the weld.

2) Physical method test: The physical test method is to use some physical phenomena to measure or test. The inspection of internal defects of materials or workpieces generally adopts non-destructive testing methods. Non-destructive testing includes ultrasonic testing, radiographic testing, penetrant testing, magnetic testing, etc.

3) Pressure Vessel Strength Test: In addition to the sealing test, the pressure vessel should also be subjected to a strength test. There are two common tests: hydrostatic test and air pressure test. Both methods can check the weld tightness of pressure vessels and pipes. The air pressure test is more sensitive and faster than the water pressure test. At the same time, the tested product does not need drainage treatment, which is especially suitable for products with difficult drainage. However, the risk of the test is greater than that of the hydrostatic test. During the test, the corresponding safety technical measures must be followed to prevent accidents during the test.

4) Densification test: For the welded container storing liquid or gas, through the densification test, it can be found that the weld has non-densification defects such as through cracks, pores, slag inclusions, incomplete penetration, and loose tissue. Densification test methods include kerosene test, water load test, water flushing test, etc.

5) During the hydrostatic test, each q345b welded pipe shall be subjected to a hydrostatic test, and there shall be no leakage. The test pressure is calculated according to P=2st/D (s-hydrostatic pressure test stress MPa), and the hydrostatic pressure test stress takes 60% of the minimum yield value (235mpa for Q235) specified in the corresponding steel strip standard. Stability time: D<508 test pressure holding time is not less than 5 seconds; D≥508 test pressure holding time is not less than 10 seconds; steel pipe repair welding, steel strip butt welding, and girth welds are subjected to 4 non-destructive inspections. 100% SX-ray or ultrasonic flaw detection shall be performed on the spiral weld of steel for conveying flammable ordinary fluids, and X-ray or ultrasonic flaw detection (20%) shall be performed on the spiral weld of steel pipes used for conveying ordinary fluids such as water, sewage, air, and heating steam.

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