Spiral steel pipe weld gap as too large, then reductions constitute vicinity effect, eddy current lack of heat, poor weld crystal indirect co-occurrence of incomplete fusion or cracking; if the gap is too small, the effect is increased near constitute, excessive heat welding to form welding seam burning;

Spiral steel pipe is hot-rolled coil production. Unit hot strip rolling process has a series of advantages of having access to production quality pipeline steel metallurgy process capability.

Submerged arc welding molding process is the use of a large welding current carcass liner on the back by way of the molding conditions, the weldment welded thoroughly to thereby obtain double-sided weld.

With China's sustained economic development, the state vigorously develop the energy sector, long-distance oil pipeline and gas pipeline are an important way of energy security in the oil and gas pipeline corrosion in the construction process, the surface of the steel pipe processing is to determine the service life of critical pipeline anti-corrosion First, it is a solid combination of anti-corrosion layer with steel pipe premise.

Tubing is important to oil drilling equipment, and its main equipment includes drill, core pipe and casing, drill collars and drilling small diameter steel pipe and so on. Mainly used for oil well drilling and completion during drilling after wall support, in order to ensure the conduct and completion of the drilling process of the wells after the regular oil casing normal operation.

The countrywide energy sector security specifications demand the app of essential oil,the API standard and fuel transmission pipeline so welded steel pipe is vital.

Three-layer coating of steel tubes is the three-layer structure of polyole fin pipe external corrosion coating, is commonly used as a preservative pipeline. There are other IPN8710, FBE epoxy powder, such as coal tar epoxy anti-corrosive way. Generally refers to a pipe wall corrosion.

Three-roll rolling tube technology is the most advanced seamless steel tube rolling technology in the world today, firstly developed in Italy's Innse company in the 1990 s, and 168 units applied successfully for the first time by Tianjin steel tube co., LTD in 2003

TIG welding (Tungsten Inert Gas arc Welding), also known as tungsten inert gas welding. TIG welding is also used for thicker sections root pass welding, the main welds surfacing. The heat source is a DC TIG welding arc, the working voltage of 10 to 15 volts, but the current up to 300 A, the workpiece as the positive electrode, the tungsten electrode welding torch as the cathode. The inert gas is usually argon.

After cold expansion for lsaw steel pipe, steel tube and pipe end diameter will increase by about one percent difference in diameter of the diameter, roundness, and the pipe ends are greatly improved, also have greatly improved the straightness of the steel pipe, steel pipea length of about 0.5% reduction in wall thickness decreases by about 0.8%.

After welding, the weld slag residue called slag, slag impact on the performance of the joint is relatively large. Slag because most irregular shape, will reduce the weld ductility and toughness, it will cause a lot of stress in sharp focus, sharp apex often leads to cracks, weld needle phosphide oxides and slag will weld metal brittle, reducing mechanical properties, easy slag iron oxide and sulfide iron clamp weld brittle.

Steel unload means: steel construction projects, with the overall lifting, overall improvement, slip and other programs, in the whole structure does not form a stable framework for temporary use as a tower or steel columns supporting the member or structure fixed at the completion of the installation and welding work interface, complete the overall structure of the force, the removal of the temporary support uninstall process is called steel.