Introduction of domestic large diameter straight seam welded pipe production process Straight seam welded pipes are formed by bending a steel plate or a steel strip and then welded. According to the weld form, it is divided into straight welded pipe and spiral welded pipe. According to the purpose, it is divided into general welded pipe, galvanized welded pipe, blown oxygen welded pipe, wire casing, metric welded pipe, idler pipe, deep well pump pipe, automobile pipe, transformer pipe, electric welding thin wall pipe, electric welding special pipe and spiral welded pipe. First, the main production process description of large diameter straight seam welded pipe: 1. Panel inspection: After the steel plate used to manufacture the large-diameter submerged arc welded straight seam steel pipe enters the production line, the whole board ultrasonic inspection is first carried out; 2. Milling edge: double-sided milling the two edges of the steel plate by the edge milling machine to achieve the required plate width, edge parallelism and groove shape; 3. Pre-bend: use the pre-bending machine to pre-bend the edge of the board so that the edge of the board has the required curvature; 4. Molding: On the JCO molding machine, half of the pre-bent steel plate is first stepped and pressed into a "J" shape, and the other half of the steel plate is also bent and pressed into a "C" shape, and finally an opening is formed. "O" shape 5. Pre-welding: joints of straight seam welded steel pipes after forming and continuous welding by gas shielded welding (MAG); 6. Internal welding: welding by longitudinal multi-wire submerged arc welding (up to four wires) on the inside of a straight seam steel pipe; 7. External welding: welding by longitudinal multi-wire submerged arc welding on the outside of straight seam submerged arc welded steel pipe; 8. Ultrasonic inspection I: 100% inspection of the inner and outer welds of straight seam welded steel pipes and the base metal on both sides of the weld; 9. X-ray inspection I: 100% X-ray industrial TV inspection of internal and external welds, using image processing system to ensure the sensitivity of flaw detection; 10. Expanding diameter: Expanding the full length of the submerged arc welded straight seam steel pipe to improve the dimensional accuracy of the steel pipe and improve the distribution of stress in the steel pipe; 11. Hydraulic test: The steel pipe after diameter expansion is tested on the hydraulic testing machine to ensure that the steel pipe meets the test pressure required by the standard. The machine has automatic recording and storage functions; 12. Chamfering: The steel pipe after passing the inspection shall be processed at the end of the pipe to achieve the required pipe end groove size; 13. Ultrasonic inspection II: Ultrasonic inspection is carried out again and again to check for defects that may occur after straightening and water pressure of straight seam welded steel pipes; 14. X-ray inspection II: X-ray industrial TV inspection and tube end weld filming of the steel pipe after the expansion and hydrostatic test; 15. Tube End Magnetic Particle Inspection: Perform this inspection to find tube end defects; 16. Anti-corrosion and coating: The qualified steel pipe is preserved and coated according to user requirements. Second, the analysis of dry welding technology of large diameter thick-walled welded pipe: Fully welded large-diameter, thick-walled (greater than 21mm) pipelines often use U-shaped groove or composite groove. Due to the time-consuming and labor-intensive processing of U-shaped groove and composite groove, the welding efficiency of the pipeline is restricted. The V-shaped groove is simple to process, saving time and labor. However, when the V-groove of large-diameter and thick-walled pipelines is fully welded, if the welding process parameters are improperly selected, welding defects will occur. The welding method uses STT root welding + CRC-P260 automatic welding machine for heat welding, filling and covering. Welding equipment: Lincoln STT welder, Lincoln DC-400, CRC-P260 automatic welder. Protective gas: STT root welding protection gas 100% CO2, fully automatic welding shielding gas is 80% Ar + 20% CO2. Automatic welding commonly used composite groove or U-shaped groove, V-shaped groove can also be used in small wall thickness pipelines, their common feature is that the upper gap of the groove is small. The second-line pipeline of the West-East Gas Pipeline has a wall thickness of 21.0 mm, and the upper mouth of the V-shaped groove has a width of about 22 mm. This width is close to the CRC-P260 welding gun swing limit. Such a groove type is a huge challenge for automatic welding. According to past experience, the welding process parameters of the automatic welding test were determined. The above parameters were used for the automatic welding test. In the test welding, the automatic welds were found to be prone to defects such as unmelted between layers, unfused side walls, dense pores, and excessive height of the overhead weld. In order to ensure a good cover forming effect, the cover welding is less preferred. At the same time of welding speed, the welding gun swing frequency is minimized, so that the cover surface weld seam is thin and wide, thereby reducing the existence time of the molten pool and achieving the purpose of reducing the remaining position of the overhead welding position. According to the test welding results and analysis, the STT root welding + CRC automatic welding filling and capping process parameters of the second-line tie line of the West-East Gas Pipeline were finalized. According to the welding parameters of Table 3, the welds are tested without defects such as porosity, cracks, and unfusion, and the surface of the weld is molded, and the macroscopic metallurgy is good. The mechanical properties of the welds have been tested by the Welding Technology Center of the China Petroleum and Natural Gas Pipeline Science Research Institute. The indicators meet the construction requirements of the second line of the West-East Gas Pipeline. The successful application of STT root welding + CRC-P260 automatic welding on large diameter and thick wall (V-groove) pipelines fully demonstrates the characteristics of automatic welding technology with high quality, high efficiency and low labor intensity. Third, the technical requirements and quality inspection of straight seam welded pipe: According to the standard of GB3092 "welded steel pipe for low-pressure fluid transportation", the nominal diameter of the welded pipe is 6~150mm, the nominal wall thickness is 2.0~6.0mm, and the length of the welded pipe is usually 4~10m, which can be fixed length or multiple length. Factory. The surface quality of the steel pipe should be smooth, and defects such as folding, cracking, delamination and lap welding are not allowed. The surface of the steel pipe is allowed to have slight defects such as scribes, scratches, misalignment of the weld, burns and scars that do not exceed the negative deviation of the wall thickness. Allows thickening of the wall thickness at the weld and the presence of internal weld beads. Welded steel pipes shall be subjected to mechanical performance tests, flattening tests and flare tests, and shall meet the requirements specified in the standard. The steel pipe should be able to withstand a certain internal pressure, and if necessary, carry out a pressure test of 2.5Mpa to maintain no leakage for one minute. It is allowed to replace the hydrostatic test by means of eddy current testing. Eddy current testing is carried out according to GB7735 "Steel Flow Test Method for Steel Tubes". The eddy current testing method is to fix the probe on the frame, and the flaw detection and the weld seam are kept at a distance of 3~5mm. The weld is fully scanned by the rapid movement of the steel pipe, and the flaw detection signal is automatically processed and automatically sorted by the eddy current flaw detector. To achieve the purpose of testing. The welded pipe after the flaw detection is cut with a flying saw according to the specified length, and is turned off the frame by the flip frame. Both ends of the steel pipe should be chamfered with flat heads, printed with marks, and the finished pipe is packaged with hexagonal packaging and shipped. Oak Flooring,Oak Engineered Wooden Flooring,Oak Wood Floor,Engineered Flooring Jiangsu Zhenrui Furniture Material Co., Ltd. , https://www.zrfloors.com