Thick-walled straight seam steel pipe is a steel pipe made by rolling the long steel strip of the specification into a round pipe through a high-frequency welding unit and welding the straight seam. The shape of the steel pipe can be round, square or irregular, depending 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 with σs≤300N/mm2 and σs≤500N/mm2. The production process of thick-walled straight seam steel pipe is as follows:
1. Plate inspection: After the steel plate used to manufacture large-diameter submerged arc welded thick-walled straight seam steel pipes enters the production line, the first full-plate wave inspection is carried out;
2. Edge milling: double-sided milling on both edges of the steel plate by the edge milling machine to make it meet 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 JCO forming machine, first half of the pre-bent steel plate is stamped into a “J” shape by multiple steps, and then the other half of the steel plate is also bent and pressed into a “C” shape, and finally formed Open “O” shape
5. Pre-welding: make the formed straight seam welded steel pipe seam together and use gas shielded welding (MAG) for continuous welding;
6. Internal welding: use tandem multi-wire submerged arc welding (mostly four wires) to weld on the inner side of thick-walled straight seam steel pipe;
7. External welding: use tandem multi-wire submerged arc welding to weld on the outside of the straight seam submerged arc welded steel pipe;
8. Wave inspection Ⅰ: 100% inspection of the inner and outer 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 TV inspection for internal and external welds, using image processing system to ensure the sensitivity of flaw detection;
10. Diameter expansion: expand the full length of the submerged arc welded thick-walled straight seam steel pipe to improve the dimensional accuracy of the steel pipe and check the distribution of the internal stress of the steel pipe;
11. Hydrostatic test: On the hydrostatic testing machine, inspect the expanded steel pipes one by one 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 qualified steel pipe to meet the required bevel size of the pipe end;
13. Wave test II: Carry out wave test one by one again to check possible defects of straight seam welded steel pipes after diameter expansion and hydraulic pressure;
14. X-ray inspection II: Carry out X-ray industrial TV inspection and filming of pipe end welds on steel pipes after diameter expansion and hydrostatic test;
15. Magnetic particle inspection at the end of the pipe: carry out this inspection to find defects at the end of the pipe;
16. Anti-corrosion and coating: The qualified steel pipes are anti-corrosion and coating according to user requirements.
The development of seamless steel pipes focuses on energy-saving and emission-reduction technologies. 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 expansion is the best way to eliminate residual stress for spiral submerged arc welded pipes. Reasonable plan, straight seam high frequency welded pipe should take advantage of weld heat treatment.
When formulating relevant policies, it is advisable to focus on macro-control and not involve the approval of specific units; it is necessary to eliminate the contradiction of excess capacity and prevent blind comparison of excess functions.
At present, my country’s steel pipe product structure is in the pattern of excess low-end products and insufficient products. Or, but also to prevent homogenization. As a result, the enterprise grasps the correct orientation in the adjustment process of technology structure and product structure.
In view of the characteristics of small, numerous and scattered steel pipe enterprises, especially private enterprises, 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 pipes, and each type has different characteristics. Therefore, in terms of technology and product structure, it is necessary to complement each other’s strengths and avoid weaknesses. Regarding the structural adjustment of the seamless steel pipe industry, energy-saving and environmental protection technologies should be actively adopted, among which technologies such as on-line normalization technology, regenerative heating furnace and annular furnace waste heat utilization have remarkable energy-saving effects; attention should also be paid to the treatment of waste water and waste acid and Comprehensive utilization to realize circular economy.
Thick-wall straight seam steel pipe and spiral steel pipe are a kind of welded steel pipe. They are widely used in national production and construction. Thick-wall straight seam steel pipe and spiral steel pipe have many differences due to different production processes. The following is a detailed discussion of thick-wall steel pipe. The difference between straight seam steel pipe and spiral steel pipe.
The production process of straight seam welded pipe is relatively simple. The main production processes are high-frequency welding thick-wall straight seam steel pipe and submerged arc welding thick-wall straight seam steel pipe. Thick-wall straight seam steel pipe has high production efficiency, low cost and rapid development. The strength of the spiral welded pipe is generally higher than that of the straight seam welded pipe. The main production process is submerged arc welding. The spiral steel pipe can use the blank of the same width to produce welded pipes with different diameters, and can also use narrower blanks 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 30-100%, and the production speed is lower. Therefore, most of the welded pipes with smaller diameters adopt straight seam welding, and most of the large diameter welded pipes adopt spiral welding. T-welding technology is used in the industry to produce large-diameter thick-walled straight-seam steel pipes, that is, short thick-walled straight-seam steel pipes are butt-jointed again to form a length that meets the needs of the project. 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, which increases the possibility of cracks.
Post time: Aug-23-2023