Straight seam steel pipe welding technology attention points and advantages of conveying fluid

The welding current in the swing welding of the straight seam steel pipe is slightly larger than that of the traditional welding method; secondly, the elongation of the tungsten electrode in the swing welding of the straight seam steel pipe is determined according to the pipe wall thickness, usually 4-5mm; the argon flow rate is slightly larger than that of the traditional welding method, about 8-10l/min; after the swing welding of straight seam steel pipe, the swing amplitude is 2mm of the blunt edge of the groove on both sides of the fusion; the left and right hands are flexibly matched, the swing is even, and the wire feeding is even. The swing welding technology of straight seam steel pipe is generally used for the welding of thick wall straight seam steel pipe. Compared with the traditional linear welding method, the welding technical parameters of the swing method straight seam steel pipe are slightly different. First, the end of the porcelain nozzle of the argon arc welding is slightly thicker than the traditional linear welding method. The difference, taking the 00Cr19Ni10 weld of φ89×5 as an example, the gap of the traditional linear welding method is 0~3mm, while the swing method is 4mm, and the welding specifications are also different.

The diameter expansion of straight seam steel pipe is a pressure processing process that uses hydraulic or mechanical means to apply force from the inner wall of the steel pipe to expand the steel pipe radially outward. The mechanical method is simpler and more efficient than the hydraulic method. Several large-diameter straight seam steel pipe pipelines in the world have been used in the expansion process. The block expands in the radial direction so that the tube blank can realize the process of plastic deformation of the whole tube length in a step-by-step manner along the length direction. Divided into 5 stages

1. Preliminary rounding stage. The fan-shaped blocks are opened until all the fan-shaped blocks are in contact with the inner wall of the steel pipe. At this time, the radius of each point in the inner circular pipe of the steel pipe within the range of the step size is almost the same, and the steel pipe is initially rounded.

2. Nominal inner diameter stage. The fan-shaped block starts to reduce the movement speed from the front position until it reaches the required position, which is the required inner circumference position of the finished pipe.

3. Repetition compensation stage. The fan-shaped block starts to further reduce the speed at the position of stage 2 until it reaches the required position, which is the inner circumference position of the steel pipe before the rebound is required by the process design.

4. Stable pressure holding stage. The inner circumference of the steel pipe remains stationary for a while before the sector block is bounced back, which is the pressure-holding and stable stage required by the equipment and the expansion process.

5. Unloading return stage. The fan-shaped block quickly retracts from the inner circumference of the steel pipe before the rebound until it reaches the initial diameter expansion position, which is the small shrinkage diameter of the fan-shaped block required by the expansion process.

What are the advantages of using straight seam steel pipe to transport fluids?

1. The infrastructure cost is low. Compared with railway transportation, the infrastructure cost can be saved by three points, and the transportation volume is twice that of the railway.

2. The construction is simple, the construction speed is fast, and it is generally laid underground, which is reliable and adaptable to various terrains.

3. The transportation operation cost is low, and it can be highly automated. Compared with other transportation methods, the pipeline transportation of straight seam steel pipes is cheap, and the freight is only about 10% of the railway and about 2% of the waterway. At present, the proportion of oil and gas transported by straight seam steel pipes in the world is increasing, accounting for about 75%-95% of the total oil and gas. products, and has been studying the use of straight seam steel pipes to transport solid substances. The development direction of straight seam steel pipe pipeline transportation points to the direction of large diameter and high pressure.