a. The cutting length for thick-walled steel tube blanks is calculated as follows: (Unit: millimeters) Cutting Length = Pi × (Outer Diameter - Wall Thickness) - Experience Adjustment Value. The experience adjustment value is generally 2mm. The cutting is performed using a shearing machine, or a semi-automatic oxygen-acetylene cutting machine can be used. If the latter is chosen, it should be performed by a skilled welder and gas welder in coordination. Before cutting, the steel plate dimensions should be checked for standard rectangular shape using the Pythagorean theorem. If not, adjustments should be made, using the same cutting method: a semi-automatic oxygen-acetylene cutting machine, ensuring the track remains straight. The cutting length deviation of the steel plate should not exceed 2mm.

b. After slope cutting and steel plate sizing, all four sides must be processed with a semi-automatic oxygen-flame cutting machine. During slope cutting, the nozzle should be rotated at an angle, typically around 25-30°. Pay attention to leave a blunt edge of 2-3mm during slope cutting.

Before the rolling and coiling process begins, prepare upper and lower dies that match the tube curvature, with a width of approximately 30-40cm. The dies should be as precise as possible and possess sufficient rigidity to ensure they do not deform after multiple compressions. The dies should be rigidly mounted on the press machine, aligned vertically. During operation, insert the pre-cut and beveled steel plate parallel into the die, about 15-20cm deep, start the press machine, lift the jack, raise the lower die to force the cold bending deformation of the steel plate ends. Once the ends of the steel plate are fully in contact with the upper and lower dies, operate the press machine to lower the lower die to release, pull out the steel plate, completing one end of the compression. The same process is applied to the other end.

d. Heavy Wall Tube Rolling. Insert the steel plate between the upper and lower rolls of the three-roll tube roller, aligning the plate end line with the roll axis. Start the tube roller, allowing the upper roll to slowly descend and gently press against the steel plate. Then, rotate the upper and lower rolls to gradually curve and deform the steel plate. Pay attention not to lower the upper roll too much at once to avoid overrolling. Let the upper roll descend gradually in increments, reducing the curvature radius of the steel plate incrementally until the ends of the plate meet.

e. The thick-walled pipe rolling group alignment and welding. The welds during the pipe rolling construction mainly include longitudinal welds and circumferential welds, and their alignment requirements should comply with the relevant provisions of GB50235-97 specifications. Spot welding during alignment is done manually with an electric arc welder, while the formal welding is performed using submerged arc automatic welding. Welders using manual electric arc welding and operators of submerged arc automatic welding machines must hold valid qualifications. The surface quality and inherent quality of the welds must meet the relevant provisions of GB50235-97 and GB50236-97 specifications, and must pass a 100% oil penetration test. If the owner or supervisor requests, ultrasonic non-destructive testing can be conducted. Welds that do not meet the standards must be repaired, but no more than two repairs are allowed on the same weld. If further repairs fail, the entire weld must be cut open, re-prepared, aligned, and welded. The quality requirements for steel plate rolling pipes are the same as those for the previous material acceptance requirements.