Thick-walled straight-seam steel pipes are made by rolling long strips of steel strips into round tubes through high-frequency welding units and welding straight seams. The shape of the steel pipe can be round, square, or special-shaped, which depends on the sizing and rolling after welding. The main materials of welded steel pipes are low carbon steel and low alloy steel or other steel materials with σs≤300N/mm2, and σs≤500N/mm2. The production process of thick-walled straight seam steel pipe is as follows:
1. Plate detection: After the steel plates used to manufacture large-diameter submerged arc welded thick-walled straight seam steel pipes enter the production line, they undergo full plate wave inspection for the first time;
2. Edge milling: Use an edge milling machine to perform double-sided milling on both edges of the steel plate to achieve the required plate width, plate edge parallelism, and bevel shape;
3. Pre-bending edge: Use a pre-bending machine to pre-bend the edge of the board so that the edge of the board has a curvature that meets the requirements;
4. Forming: On the JCO forming machine, the first half of the pre-bent steel plate is stamped into a “J” shape through multiple steps, and then the other half of the steel plate is similarly bent into a “C” shape, and finally formed into a “J” shape. Open “O” shape
5. Pre-welding: join the formed straight seam welded steel pipes and use gas-shielded welding (MAG) for continuous welding;
6. Internal welding: Use longitudinal multi-wire submerged arc welding (mostly four wires) to weld the inside of thick-walled straight seam steel pipes;
7. External welding: tandem multi-wire submerged arc welding is used to weld the outside of the longitudinal submerged arc welded steel pipe;
8. Wave inspection I: 100% inspection of the internal and external welds of the straight seam welded steel pipe and the base metal on both sides of the weld;
9. X-ray inspection I: 100% X-ray industrial television inspection of internal and external welds, using an image processing system to ensure the sensitivity of flaw detection;
10. Diameter expansion: The entire length of the submerged arc welded thick-walled straight seam steel pipe is expanded to improve the dimensional accuracy of the steel pipe and the distribution of stress within the steel pipe;
11. Hydraulic pressure test: The expanded steel pipes are inspected one by one on the hydraulic pressure testing machine to ensure that the steel pipes meet the test pressure required by the standard. The machine has automatic recording and storage functions;
12. Chamfering: Process the pipe end of the steel pipe that has passed the inspection to achieve the required pipe end bevel size;
13. Wave inspection II: Carry out wave inspection again one by one to check the defects that may occur after diameter expansion and hydraulic pressure of the straight seam welded steel pipe;
14. X-ray inspection II: Conduct X-ray industrial television inspection and pipe end weld photography on the steel pipe after diameter expansion and hydraulic pressure test;
15. Magnetic particle inspection of pipe ends: This inspection is performed to find defects at pipe ends;
16. Anti-corrosion and coating: Qualified steel pipes will be anti-corrosion and coated according to user requirements.
The development of seamless steel pipes focuses on energy-saving and emission-reduction technology. Thick-walled straight seam steel pipes focus on the development of high-grade (X100) and large-wall thickness (≥60mm) products. The use of overall pipe diameter expansion is the best way to eliminate residual stress in spiral-submerged arc-welded pipes. A reasonable solution, straight seam high frequency welded pipe should take advantage of the weld heat treatment.
When formulating relevant policies, it is advisable to focus on macro-control rather than involving the approval of specific units; it is necessary to eliminate the contradiction of overcapacity and prevent blind comparisons with overcapacity. At present, my country’s steel pipe product structure is characterized by a surplus of low-end products and a shortage of products. However, this does not mean that all enterprises must develop in the direction of products. Instead, each enterprise should determine its market positioning according to local conditions, either specialized, personalized, or Orization, while also preventing homogenization. As a result, enterprises can grasp the correct direction in the process of adjusting their technical structure and product structure.
Given the characteristics of steel pipe enterprises, especially private enterprises, which are small, numerous, and scattered, enterprises can be integrated into industrial groups according to production process characteristics, product scale, technical equipment, and other conditions. There are many types of steel pipe machines, each with different characteristics. Therefore, the advantages should be complementary in terms of technology and product structure, and strengths should be maximized while avoiding weaknesses. Regarding the structural adjustment of the seamless steel pipe industry, energy-saving and environmentally friendly technologies should be actively adopted. Among them, online normalization technology, regenerative heating furnaces, and annular furnace waste heat utilization technologies have significant energy-saving effects; attention should also be paid to the treatment and treatment of wastewater and waste acid. Comprehensive utilization and realization of the circular economy.
Thick-walled straight-seam steel pipes and spiral steel pipes are both types of welded steel pipes. They are widely used in national production and construction. Thick-walled straight-seam steel pipes and spiral steel pipes have many differences due to different production processes. The thick-walled steel pipes are discussed in detail below. The difference between straight seam steel pipe and spiral steel pipe. The production process of straight seam welded pipes is relatively simple. The main production processes include high-frequency welding of thick-walled straight seam steel pipes and submerged arc welding of thick-walled straight seam steel pipes. Thick-walled straight seam steel pipes have high production efficiency, low cost, and rapid development. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. The main production process is submerged arc welding. Spiral steel pipes can use billets of the same width to produce welded pipes with different diameters, and narrow billets can also be used to produce welded pipes with larger diameters. However, compared with thick-walled straight seam steel pipes of the same length, the weld length is increased by 30 to 100%, and the production speed is lower. Therefore, smaller-diameter welded pipes mostly use straight seam welding, while large diameter welded pipes mostly use spiral welding. In the industry, T-welding technology is used when producing larger-diameter thick-walled straight-seam steel pipes. That is, short sections of thick-walled straight-seam steel pipes are butted together to a length that meets the needs of the project. The probability of T-weld thick-walled straight-seam steel pipe defects is It is also greatly improved, and the welding residual stress at the T-shaped weld is relatively large, and the weld metal is often in a three-dimensional stress state, increasing the possibility of cracks.
Post time: Jan-26-2024