The welding current in rocking welding of straight seam steel pipes is slightly larger than the traditional welding method; secondly, the extension length of the tungsten electrode in rocking welding of straight seam steel pipes is determined according to the pipe wall thickness, usually 4-5mm; the argon gas flow rate is slightly larger than the traditional welding method, about 8-10l/min; in swing welding of straight seam steel pipes, the swing amplitude is 2mm where the blunt edges of the grooves on both sides are fused; the left and right hands cooperate flexibly, swing evenly, and feed wire evenly. The swing welding technology of straight seam steel pipes is generally used for the welding of thick-walled straight seam steel pipes. The technical parameters of the swing method for welding straight seam steel pipes are slightly different from the traditional linear welding method. First, the end of the porcelain nozzle of argon arc welding is slightly thicker than that of the traditional linear welding method. Secondly, the gap between the welding joints is also smaller. The difference, taking the φ89×5 00Cr19Ni10 welding joint as an example, the gap of the traditional linear welding method is 0~3mm, while the gap of the swing method is 4mm, and the welding specifications are also different.

The diameter expansion of straight seam welded pipe is a pressure processing technology that uses hydraulic or mechanical means to apply force from the inner wall of the steel pipe to expand the steel pipe outward in the radial direction. The mechanical method is simpler and more efficient than the hydraulic method. The diameter expansion process of several large-diameter straight seam welded pipe pipelines in the world has been adopted. The process is:
Mechanical diameter expansion uses the segmented sector block at the end of the diameter expander to expand in the radial direction so that the pipe blank can achieve plastic deformation of the entire pipe length in a step-by-step manner along the length direction. Divided into 5 stages.
1. Preliminary rounding stage. The sector blocks are opened until all the sector blocks are in contact with the inner wall of the steel pipe. At this time, the radius of each point in the inner circular tube of the steel pipe within the step range is almost the same, and the steel pipe is initially rounded.
2. Nominal inner diameter stage. The sector block starts to reduce its movement speed from the front position until it reaches the required position, which is the required inner circumferential position of the finished pipe.
3. Rebound compensation stage. The sector block starts from the second stage position and further reduces the speed until it reaches the required position. This position is the inner circumferential position of the steel pipe before rebound is required by the process design.
4. Pressure stabilization stage. The sector-shaped block remains stationary in the inner circumferential position of the steel pipe for a period of time before springing back. This is the pressure-maintaining and stable stage required by the equipment and diameter expansion process.
5. Unloading return stage. The sector-shaped block rapidly retracts from the inner circumferential position of the steel pipe before rebounding until it reaches the initial diameter expansion position, which is the minimum contraction diameter of the sector-shaped block required by the diameter expansion process.

What are the advantages of using straight seam welded pipes to transport fluids?
1. The infrastructure cost is low. Compared with railway transportation, the infrastructure cost can be saved by three points, while the transportation volume is twice that of the railway.
2. The construction is simple and fast. It is generally laid underground, reliable, and adaptable to various terrains.
3. The transportation operating cost is low and a high degree of automation can be achieved. Compared with other transportation methods, straight seam welded pipe transportation is cheap, and its freight is only 10% of the railway and about 20% of the waterway.

At present, the proportion of oil and gas transported by straight seam welded pipes in the world is increasing, accounting for about 75%-95% of the total oil and gas. The range of transportation varieties is gradually expanding, not only oil and gas, but also various chemical raw materials and Products, and the use of straight seam welded pipes to transport solid materials has been studied.

The development direction of straight seam welded pipe pipeline transportation points to the direction of large diameter and high pressure.

What are the characteristics of welded pipes compared with seamless steel pipes?
1. The production process is simple.
2. Less equipment, simple structure, lightweight, easy to realize continuous, automated, and mechanized production.
3. Product cost is low.
4. Suitable for a wide range of varieties and specifications, diameter 6-3100mm, wall thickness 0.3-35mm.

Forming and welding are the basic processes of welded pipe production, and welded pipe production methods are classified according to the characteristics of these two processes. The welding method can be divided into four types: furnace welding, electric welding, gas welding, and gas-electric welding. Furnace welding is divided into lap welding and butt welding according to the weld form. The forming methods of butt welding are divided into two types: drawing and rolling. There are two types of equipment used in drawing: chain furnace welding machines and continuous furnace welding machines. Roll forming uses a continuous roll machine.

Electric welding is further divided into three types: contact welding, induction welding, and arc welding. Contact welding is further divided into resistance welding and flash welding. Arc welding is further divided into open arc welding, submerged arc welding, and shielded arc welding. Submerged arc welding is further divided into There are two types straight seam and spiral seam. Gas welding is divided into acetylene welding and water gas welding. Water gas welding equipment is divided into roller-type pipe welding machines and forging-type pipe welding machines. Gas welding is hydrogen atomic welding.