A pipe in which the weld is spirally distributed with respect to the axis of the pipe. Mainly used as conveying pipes, pipe piles and some structural pipes. Product specifications: outer diameter 300 ~ 3660mm, wall thickness 3.2 ~ 25.4mm. The low carbon carbon structural steel or the low alloy structural steel strip is rolled into a tube blank at a certain angle of the helix (called a forming angle), and then the pipe joint is welded, which can be produced by using a narrow strip steel. Large diameter steel pipe. Spiral welded pipe is mainly used for oil and natural gas transmission pipelines, and its specifications are expressed by outer diameter * wall thickness. Spiral welded pipes are single-sided welded and double-sided welded. The welded pipe shall ensure that the hydraulic test and the tensile strength and cold bending performance of the weld are in compliance with the regulations.
Spiral welded pipe type:
Steel belt butt weld: Steel belt butt weld is the weld of the steel plate or steel strip on the spiral seam steel pipe.
Butt weld: It is a ring weld formed by joining two steel pipes together.
Positioning Weld: It is the weld used to fix the butt edge before final welding.
The characteristics of spiral welded pipe production are:
(1) A variety of outer diameter pipes can be produced from strips of the same width;
(2) The flatness of the pipe is good and the size is relatively accurate. The inner and outer spiral welds increase the rigidity of the pipe body, so there is no need for sizing and straightening after welding;
(3) Easy to realize mechanization, automation and continuous production;
(4) Compared with other equipment of similar scale, the size is small, the land occupation and investment are small, and the construction is fast;
(5) Compared with the straight seam welded pipe of the same size, the weld length per unit length of the pipe is long, so the productivity is low.
Spiral welded pipe is made by rolling a low carbon carbon structural steel or a low alloy structural steel strip into a tube blank at a certain angle of a helix (called a forming angle), and then welding the pipe seam, which can be used with a narrow belt. Steel produces large diameter steel pipes. Spiral welded pipes are mainly used for oil and natural gas transmission pipelines. Their specifications are expressed by outer diameter * wall thickness. Spiral welded pipes are single-sided welded and double-sided welded. The welded pipes are to be hydraulically tested and welded. The tensile strength and cold bending performance of the joint are to comply with the regulations.
Execution standards for spiral welded pipes:
National standard: CB/T9711.1 - 1997;
Industry Standard of the Ministry of Petroleum Industry: SY/T5037-2000;
United States: APISPEC 5L welded steel pipe standard;
Spiral welded pipe process:
The process is as follows:
Unwinding - winding - leveling - butt welding - external welding - pipe cutting - breaking - subsequent welding - hydraulic test;
The inspection process is as follows:
Raw material inspection - leveling inspection - butt welding inspection - forming inspection - internal welding inspection - ultrasonic inspection - groove inspection - dimensional inspection - X-ray inspection - final inspection;
The anti-corrosion requirements of this project are quite different from those of other domestic projects. The main differences are:
·Inner anti-corrosion materials generally use cement mortar in China. This project uses non-toxic epoxy paint (thickness 0.4mm).
· The external anti-corrosion coating EDM test voltage is generally 3000 volts in China, the maximum is not more than 5000 volts, and the project is 10 kV. In response to the above requirements, we focus on the following two aspects:
· Strict sanding work procedures to ensure the quality of derusting, and the spraying of the inner and outer primers within one hour, which is the basis for ensuring the quality of anti-corrosion.
· When formulating the anti-corrosion process, we specifically require that the glass cloth be first impregnated with the epoxy coal bitumen paint, semi-mechanically rolled, and the glass cloth is operated by the manual roller to ensure the uniformity and fineness of the outer coating.
·The inner and outer anti-corrosion pipes are placed in the open storage yard for 4 months, the inner coating has no yellow pitting, and the external anti-corrosion layer electric discharge test can still reach the requirement of 10 kV.
2008-2009 China spiral welded pipe market status research and development trend report is provided by the market monitoring center and market research center researchers according to the national statistical agencies, market monitoring database, import and export statistics department and other institutions to provide or publish data, information, use Scientific statistical methods and research methods are produced. It is the market information of investors and business managers who understand the current situation of the spiral welded pipe industry, market competition, regional market distribution, and analysis of key industry enterprises.
Due to the increasing bearing pressure of the pipeline, the use conditions are increasingly demanding, and the service life of the pipeline should be extended as much as possible. Therefore, the main development directions of the spiral welded pipe are:
(1) Producing large-diameter thick-walled tubes to improve pressure resistance;
(2) Design and production of new-structured steel pipes, such as double-layer spiral welded pipes, which are welded into a double-layer pipe with a strip of half the thickness of the pipe wall, which is not only stronger than the single-layer pipe of the same thickness, and does not exhibit brittle failure;
(3) Develop new steel grades, improve the technical level of smelting process, widely adopt controlled rolling and post-rolling residual heat treatment processes to continuously improve the toughness and welding performance of the pipe;
(4) Vigorously develop coated tubes, such as coating the inner wall of the tube with anti-corrosion layer, which not only prolongs the service life, but also improves the smoothness of the inner wall, reduces the frictional resistance of the fluid, reduces the wax and dirt, reduces the number of pigging, and reduces maintenance. cost.
Spiral welded pipe production process:
The raw materials of the spiral welded pipe are strip and plate, and the thickness is 19 mm or more. When the strip is used to ensure the continuous feeding of the front and rear coils during the first and last butt welding, the looper device can also be used for the butt welding connection. As shown in the figure, the flying soldering trolley can be used for the entire preparation from unwinding to butt welding. The operation is completed during its movement along the track. When the tail of the current coiled steel strip is bitten by the rear clamp of the butt welder, the trolley is pulled forward at a synchronous speed with the forming of a pre-welding machine. After the butt welding is finished, the rear clamp is released, and the trolley returns by itself. To the original position. When using the sheet, it is necessary to first weld a single sheet of steel to the slats outside the line, and then send the line to the welding line for the welding line. The butt welding is performed by automatic submerged arc welding, which is carried out on the inner surface of the pipe. After the forming and pre-welding, the surface of the pipe is repaired and welded, and then the inner and outer welding of the spiral weld is carried out. Before the strip enters the forming machine, the edge of the plate must be pre-bent according to the pipe diameter, wall thickness and forming angle, so that the deformation curvature of the formed edge and the middle portion is consistent, and the "bamboo" defect of the protrusion in the weld zone is prevented. After pre-bending, it enters the spiral former to form (see spiral forming) and pre-weld. In order to improve productivity, a forming one pre-welding wire is used in combination with a plurality of inner and outer welding wires. This will improve the quality of the weld and increase the output significantly. Pre-welding generally uses welding gas arc welding or high-frequency resistance welding with fast welding speed, full-length welding, and multi-pole automatic submerged arc welding.
Schematic diagram of spiral welded pipe
The main development direction of spiral welded pipe production: Due to the increasing bearing pressure of pipelines, the use conditions are increasingly demanding, and the service life of pipelines should be extended as much as possible. Therefore, the main development directions of spiral welded pipes are:
(1) Producing large-diameter thick-walled tubes to improve pressure resistance;
(2) Design and production of new-structured steel pipes, such as double-layer spiral welded pipes, which are welded into a double-layer pipe with a strip of half the thickness of the pipe wall, which is not only stronger than the single-layer pipe of the same thickness, and does not exhibit brittle failure;
(3) Develop new steel grades, improve the technical level of smelting process, widely adopt controlled rolling and post-rolling residual heat treatment processes to continuously improve the toughness and welding performance of the pipe;
(4) Vigorously develop coated tubes, such as coating the inner wall of the tube with anti-corrosion layer, which not only prolongs the service life, but also improves the smoothness of the inner wall, reduces the frictional resistance of the fluid, reduces the wax and dirt, reduces the number of pigging, and reduces maintenance. cost.
Spiral tube: Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development. The strength of the spiral welded pipe is generally higher than that of the straight welded pipe. It is possible to produce a welded pipe with a large diameter by using a narrow blank, and it is also possible to produce a welded pipe having a different pipe diameter by using a blank of the same width. However, compared with the straight pipe of the same length, the weld length is increased by 30 to 100%, and the production speed is low. Therefore, most of the smaller diameter welded pipes are straight seam welded, and the large diameter welded pipes are mostly spiral welded;
Spiral tube and its standard classification: spiral seam submerged arc welded steel pipe (SY5036-83) for pressure fluid transportation is mainly used for conveying oil and natural gas pipelines; spiral seam high frequency welded steel pipe (SY5038-83) for pressure fluid transportation, Spiral seam high-frequency welded steel pipe welded by high-frequency lap welding for pressure fluid transportation. The steel pipe has strong pressure bearing capacity and good plasticity, which is convenient for welding and processing. Generally, the spiral submerged arc welded steel pipe (SY5037-83) for low-pressure fluid transportation is made of water by double-sided automatic submerged arc welding or single-sided welding. Submerged arc welded steel pipe for general low pressure fluid transportation such as gas, air and steam.
Spiral tube material: Q235A, Q23b, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb.
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