Structural design features of straight seam steel pipe

(1) good geometric properties of the pipe section, the wall is generally thin, the pipe section material distribution around the center of mass, the pipe section turning radius, torsional stiffness; as compression, bending and two-way bending members, its high load-bearing capacity, and cold-formed pipe straightness and cross-sectional dimensions more accurate than the cross-section of the hot-rolled openings.

(2) In terms of resistance to hydrodynamic properties, the cross-section of round tubes is the best, and the effects of wind and water currents are greatly reduced. Rectangular tube sections are similar to other open sections in this respect.

(3) The tubes are of closed section; the exposed surface area is about 50% to 60% of that of the open section for the same average thickness and cross-sectional area, which helps prevent corrosion and saves paint.

(4) The connection of nodes is suitable for direct welding, which can save labor and material without going through corner gussets or other connecting parts.

(5) The appearance is more beautiful, especially the pipe frame composed of steel pipes without redundant node connections, which has a strong modern sense.

(6) If necessary, concrete can be poured into the pipe to form a composite member.

Welding method of straight seam steel pipe

The welding of straight seam steel pipe is done by milling. In addition to the traditional JCO and UO techniques, some manufacturers use the more advanced progressive forming (PFP) technology, roll bending and forming (RBE) technology. Welding is performed with argon or CO2 gas protection, using automatic pre-welding machines as well as special multi-wire (4 and 5-wire) internal and external submerged arc welding equipment, using square wave power sources and electrical power. As for the increase in diameter, the entire length of the pipe is mechanically increased. In order to carry out inspections, the plates must be tested online and the pipes must be subjected to automatic beam automatic ultrasonic testing, hydraulic testing and ultrasonic testing after welding.

The second is the control of the welding temperature. The welding temperature of straight seam steel pipe is mainly influenced by the high frequency eddy current heat power. When the heat input is not enough, the heated edge of the weld will not reach the welding temperature. Finally, adjust the position of the high frequency induction ring. The farther the induction ring is from the pressure roller, the longer the effective heating time and the larger the area affected by heat. Agents of enamel reactors point out that when welding straight seam pipes, a certain degree of adjustment of voltage and welding speed is required, and no adjustment of parameters is necessary after modification.

Welding standards of straight seam steel pipes

1.Surface defects of longitudinally welded steel pipes must be completely eliminated.

2.The total length of the repair weld of each longitudinally welded steel pipe should be less than or equal to 5% of the total length of the longitudinally welded steel pipe.

3.Length less than 100mm longitudinal welded steel pipe with multiple weld defects should be repaired as a continuous single weld. Longitudinal welded steel pipe should be repaired at least twice for a single weld, and the length of the repaired weld should be at least 50 mm.

4.The number of repair welds of longitudinally welded steel pipe shall not exceed twice each time.