Submerged arc steel pipe is stable in use. The diameter of the steel pipe is large, the transmission rate is high, and the investment of laying the pipeline can be saved. A pipeline is often used for transporting oil or natural gas. Spiral seam high-frequency welded steel tubes for pressurized fluid transport. The spiral seam submerged arc welded steel pipe for low-pressure fluid transportation is made of hot rolled steel strip as tube billet, and is spirally formed at a constant temperature. It is made by double-sided automatic submerged arc welding or single-sided welding method and used for water, gas, air, steam and other basic submerged arc welded steel pipe. After the two edges of the tube blank are heated to the welding temperature, the common metal grains are interpenetrating and crystallizing under the extrusion roll, and a firm weld is formed in the later stage. If the extrusion pressure of the spiral steel pipe is too small, the number of common crystals will be small, the strength of the weld metal will decrease, and cracking will occur after the stress. If the extrusion pressure is too large, the molten metal will be extruded from the weld, which not only reduces the strength of the weld, but also produces a large number of internal and external burrs, and even causes welding joints and other defects.

What are the methods of judging the qualification of submerged arc steel pipe?

1, pressure container strength test: pressure container, in addition to tightness test, but also strength test. There are two common hydraulic tests and air pressure tests. They can test the weld density of vessels and pipes working under pressure. The pneumatic test is more sensitive and faster than the hydraulic test. At the same time, the products after the test do not need drainage treatment. It is especially suitable for products with difficult drainage. But the test is more dangerous than the hydrostatic test. During the test, the corresponding stabilization technical measures should be observed to prevent accidents during the test.

2. Hydrostatic test: Each steel pipe should do the hydrostatic test without leakage. The test pressure should be calculated according to the test stress Mpa of the S-hydrostatic test in P=2ST/D, and the test stress of the hydrostatic test should be selected according to 60% of the smaller yield value specified in the corresponding steel belt standard.

3, the test of physical methods: the physical test method is the use of some physical phenomena to determine or test the method. Nondestructive testing is generally used in the inspection of internal defects of materials or workpieces. Nondestructive testing includes acoustic detection, ray detection, penetration detection, magnetic detection, and so on.

4, density test: storage of liquid or gas welding container, the welding seam of the non-dense defects, such as penetrating cracks, pores, slag, not welded through, and loose tissue, can be found by density test. Densification test methods include kerosene tests, water load tests, water flush tests, etc.

5, stable pressure 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.

6, judging from the surface, that is, inspection in appearance. The appearance inspection of welded joints is a simple and widely used inspection method, which is an important part of the finished product inspection. It is mainly to find the defects and size deviations of the weld surface. It is usually inspected by the naked eye, with the aid of standard templates, gauges, and magnifying glasses. If there are defects on the surface of the weld, there is a possibility of defects inside the weld.

7. Non-destructive testing: X-ray or special wave inspection should be carried out on the repair welding seam of steel pipe, the butt weld, and the circumferential seam of the steel strip. Sx-ray or acoustic wave inspection should be carried out on the spiral welds of steel pipes used for the transportation of combustible common fluids, and X-ray or special wave inspection should be carried out on the spiral welds of steel pipes used for the transportation of common fluids such as water, sewage, air, and heating steam.

Cangzhou Shenlong Pipe is specialized in the production of direct-seam submerged arc welding steel pipe, the product range is 406-3000mm, the maximum wall thickness of 60mm, product quality control is strict, fast delivery is the qualified supplier of PetroChina, BP oil.