spiral welded pipeIt is a spiral seam steel pipe with steel coil as raw material, often warm extrusion, bending and forming into a spiral shape, and using automatic double-line double-sided submerged arc welding technology for inner seam and outer seam welding. The raw materials are strip coiling, welding wire and flux. The quality and performance of spiral welded pipe shall be determined according to the needs, and different element contents and types shall be matched according to the needs. So, the following together to understand the characteristics of spiral welded pipe!

1) Carbon: The more carbon content, the higher the rigidity, but the worse the plasticity and toughness.

2) Sulfur: It is a harmful impurity in steel. Steel with high sulfur content is easy to crack when stamping at high temperature, which is usually called hot brittleness.

3) Phosphorus: Significantly reduces the plasticity and toughness of steel, especially the serious phenomenon at low temperatures is called cold brittleness. Steel requires strict control of sulfur and phosphorus, and low-carbon steel contains higher sulfur and phosphorus, which is convenient for cutting and helps to improve the machinability of steel.

4) can improve the strength of manganese steel, weaken and eliminate the adverse effects of sulfur, improve the hardenability of steel, high manganese content of high alloy steel (high manganese steel) has excellent wear resistance and other physical properties.

5) Silicon: It can improve the hardness of steel, but the plasticity and toughness are reduced. Electrical steel contains a certain amount of silicon, which can improve the soft magnetic properties.

6) Tungsten: It can improve the red hardness and hot strength of steel and improve the wear resistance of steel.

7) Chromium: It can improve the hardenability and wear resistance of steel, and improve the corrosion resistance and oxidation resistance of steel.

8) Vanadium: It can refine the grain structure of steel and improve the strength, toughness and wear resistance of steel. At high temperatures into the austenite, can improve the steel hardenability; on the contrary, in the form of carbide will reduce the hardenability.

9) It can significantly improve the hardenability and thermal strength of molybdenum: steel, prevent temper brittleness, and improve remanence and coercivity.

10) Titanium can refine the grain structure of steel and improve the strength and toughness of steel.

11) can improve the strength and toughness of nickel steel, improve hardenability. When the content is high, it can significantly change some physical properties of steel and alloys and improve the corrosion resistance of steel.

The roll shall undergo strict physical and chemical inspection before being put into operation. Head and tail butt joint of strip steel, single wire or two submerged arc welding shall be adopted, and automatic submerged arc welding shall be adopted after spiral welded pipe. Before forming, the strip steel is straightened, cut, scraped, surface cleaning, conveying and bending. The electric contact pressure gauge is used to control the pressure of the cylinders on both sides of the pressure belt, which ensures the smooth transportation of the strip steel. The weld is evenly distributed on the circumference of the spiral pipe, and the spiral welded pipe has high dimensional accuracy and strong strength. The same size of the wall thickness, the screw steel pipe can withstand a lot of pressure. Moreover, since it is continuously bent and formed, the size of the spiral tube is not limited, and the length can be freely determined.

After the welding is completed, the spiral welded pipe welding and spiral welded cross joints are examined by radiation. Each steel pipe must undergo corresponding hydrostatic pressure test. The pressure is radially sealed. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device, and the test parameters are printed.

The welding defect of spiral welded pipe is "tilt defect". In use, the main stress direction of the steel pipe, that is, the equivalent defect length of the steel pipe axis direction is less than the seamless pipe, and secondly, the pipeline steel is rolled steel plate, so the impact toughness has a large anisotropy, and the CVN value along the rolling direction is 3 times higher than the CVN value perpendicular to the rolling direction.

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