Square Galvanized Steel Pipe

The production process of square galvanized steel pipe is mainly divided into two steps:

• 1.1

Raw material preparation: Select hot-rolled or cold-rolled galvanized strip steel and galvanized coil to ensure that the mechanical properties and surface quality of the materials meet the requirements, and conduct strict physical and chemical inspections.

• 1.2

Strip steel processing: The strip steel is butt-jointed head and tail, and single-wire or double-wire submerged arc welding is adopted; before forming, it is leveled, trimmed, planed, cleaned and pre-bent to ensure that the strip steel is flat, accurate in size and clean on the surface.

• 1.3

Forming: Through external control or internal control roller forming and other methods, the electric contact pressure gauge is used to control the pressure of the cylinder on both sides of the conveyor, so that the strip steel is smoothly conveyed and rolled into a square tube blank. At the same time, the weld gap control device is used to strictly control the pipe diameter, misalignment and weld gap.

• 1.4

Welding: Both internal and external welding adopt single-wire or double-wire submerged arc welding to obtain stable welding specifications. After welding, the weld is checked with an online continuous ultrasonic automatic flaw detector. If there is a defect, it will automatically alarm and spray mark. The worker can adjust the parameters in time to eliminate the defect.

• 1.5

Cutting: Use an air plasma cutting machine to cut the welded long tube into a single square tube.

• 1.6

Pipe end processing: Mechanically process the pipe end to accurately control the end face verticality, groove angle and blunt edge.

• 2.1

Hot-dip galvanizing preparation: Clean and remove rust, remove oxide scale, oil and impurities on the surface of the square tube, generally using pickling, sandblasting and other methods.

• 2.2

Hot-dip galvanizing: Soak the square tube in molten zinc liquid at about 450-480℃, and make the zinc liquid adhere to the surface of the steel pipe through heat conduction to form a dense galvanized layer.

• 2.3

Cooling and polishing: Natural cooling or forced cooling to reduce the temperature of the square tube; mechanical polishing or chemical polishing to remove surface defects and burrs and improve appearance quality.

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