Analysis On The Technological Process Of Straight Seam Square Rectangular Pipe

When we produce straight seam square tubes, we generally go through the following process steps:

(1) Plate inspection: After the steel plate used to manufacture large-diameter submerged arc welded straight seam square tubes enter the production line, the entire plate must be ultrasonically inspected.

(2) Edge milling: The two edges of the steel plate are milled on both sides by the edge milling machine to achieve the required plate width, plate edge parallelism, and groove shape.

(3) Pre-bending: Use a pre-bending machine to pre-bend the edge of the plate so that the edge of the plate has a curvature that meets the requirements.

(4) Forming: On the forming machine, half of the pre-bent steel plate is first stamped in multiple steps.

(5) Pre-welding: The formed straight seam welded pipes are joined together and continuously welded by gas-shielded welding.

(6) Internal welding: Tandem multi-wire submerged arc welding is used to weld the inside of the straight seam square tube.

(7) External welding: Tandem multi-wire submerged arc welding is used to weld the outside of the straight seam square tube.

(8) Ultrasonic inspection: 100% inspection of the inner and outer welds of the welded pipe and the base metal on both sides of the weld.

(9) X-ray inspection: 100% X-ray industrial TV inspection is carried out on the internal and external welds, and an image processing system is used to ensure the sensitivity of flaw detection.

(10) Diameter expansion: expand the full length of the straight seam pipe to improve the dimensional accuracy and improve the distribution of internal stress in the square rectangular pipe.

（11）Hydrostatic test: On the hydrostatic testing machine, inspect the expanded steel pipes one by one to ensure that the test pressure required by the standard is met. The machine has automatic recording and storage functions.

(12) Chamfering: Process the pipe end of the square and rectangular pipe that has passed the inspection to meet the required bevel size of the pipe end.

(13) Second ultrasonic inspection: conduct ultrasonic inspection one by one again to check possible defects of straight seam pipes after diameter expansion and water pressure.

(14) Secondary X-ray inspection: X-ray industrial TV inspection and filming of pipe end welds shall be carried out on the rectangular pipe after diameter expansion and hydrostatic test.

(15) Magnetic particle inspection at the end of the pipe: This inspection is carried out to find defects at the end of the pipe.

(16) Anti-corrosion and coating: After passing the inspection, the square and rectangular tubes are anti-corrosion and coating according to user requirements.