Definition of straight seam welded pipe and spiral welded pipe

Welded pipes are common pipes in gas pipelines. Pipes with a diameter greater than 426 mm (or 508 mm) are generally referred to as large-diameter welded pipes. According to the method of welding into pipes, they can be divided into spiral welded pipes and straight welded pipes.

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 (also called a forming angle), and then welding the pipe joint to make it narrower. Strip steel produces large diameter steel pipes. Spiral welded pipe is mainly spiral submerged arc welded pipe (SSAW), which is widely used in the construction of various gas pipelines in China. Its specifications are expressed by the 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.

The straight seam welded pipe is formed by forming a hot rolled coil through a molding machine to deform the steel coil into a smooth cylindrical shape, and welding by using the skin effect of the high frequency current and the adjacent effect or the arc under the solder layer to make the blank The edge is heated and melted, and is fused under a certain pressing force, and finally cooled to form. The high-frequency straight seam welded pipe (ERW) in which the edge of the pipe blank is melted by high-frequency current is called a straight seam submerged arc welded pipe (LSAW).

The main raw materials for straight seam welded pipes are low carbon steel hot rolled coils and hot rolled strips. They are widely used in petroleum, metallurgy, construction, coal, port, machinery and other industries for oil and gas transportation, low pressure water gas transportation, mining fluid transportation, belt type. Conveyor rollers, automotive drive shafts, etc.

Seamless steel pipe|Seamless steel pipe knowledge|Seamless steel pipe specifications

The seamless steel pipe is a long strip of steel having a hollow section and no seams around it. Steel pipes have a hollow section and are used in large quantities as pipes for transporting fluids, such as pipes for transporting oil, natural gas, gas, water and certain solid materials. Compared with solid steel such as round steel, the steel pipe is lighter in weight when it has the same bending and torsional strength. It is an economical section steel and is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile transmission shafts, bicycles. Shelf and steel scaffolding used in construction. The use of steel pipes to manufacture ring-shaped parts can improve material utilization, simplify manufacturing processes, save materials and processing man-hours, such as rolling bearing rings, jacks, etc., and have been widely used in steel pipes. Steel pipes are also indispensable materials for various conventional weapons, and barrels, barrels, etc. are all made of steel pipes. Steel pipes can be divided into round pipes and shaped pipes according to the shape of the cross-sectional area. Since the area of ​​the circle is the largest under the condition of equal circumference, more fluid can be transported by the circular tube. In addition, the circular section is subjected to a relatively uniform force when subjected to internal or external radial pressure, and therefore, most of the steel pipes are round pipes.

However, the round pipe also has certain limitations. For example, under the condition of being bent by the plane, the round pipe is not as strong as the square and rectangular pipe, and some agricultural machinery skeletons, steel wood furniture, etc. are commonly used square and rectangular pipes. Shaped steel pipes of other cross-section shapes are also required depending on the application.

At present, there are more than 5,100 production plants under the 1,450 companies in more than 110 countries producing steel pipes, including more than 260 plants under 170 companies in 44 countries. In 2000, the national apparent consumption of seamless steel pipes was 4.18 million tons, of which 3.821 million tons were domestically supplied, accounting for 91.4% of total domestic demand. Imports were 359,000 tons, accounting for 8.59% of total domestic demand. In the same year, the consumption of oil pipes was about 910,000 tons. Imports are about 252,000 tons. Imported pipes account for about 70% of total domestic consumption, of which import pipes account for 27.69% of total domestic consumption, and oil pipe imports account for about 70% of total imports of seamless steel pipes. Oil pipes imported from Japan account for more than half of the total imports. China's largest oil casing production base - Tianjin Steel Pipe Co., Ltd. in 2000, the steel pipe products out of 522,000 tons, of which the production of oil casing is 364,100 tons. Casings account for more than half of the country's oil production. It ranks first in the Chinese casing market in both production and sales.

From the perspective of both international and domestic markets, the existing production capacity of seamless steel pipes (including oil-specific pipes) has exceeded demand. Therefore, the focus in the future should be to give full play to the capabilities of existing units and develop products such as high-strength grades, high-resistance, high-corrosion-resistant oil pipes, high-pressure boiler tubes and gas cylinders. It is also the content of the country to optimize the product structure for the current steel market in China. This is also the key to increasing the competitiveness of domestic and foreign products and expanding market share. That is to say, improving the market competitiveness of domestic steel pipe enterprises is the key to the long-term mission and successful development of domestic enterprises after the WTO.

Straight seam steel pipe knowledge Welded steel pipe, also called welded pipe, is a steel pipe made by welding a steel plate or a steel strip after being crimped. The welded steel pipe has simple production process, high production efficiency, many varieties and specifications, and less equipment, but the general strength is lower than that of seamless steel pipe. Since the 1930s, with the rapid development of high-quality strip continuous rolling production and the advancement of welding and inspection technology, the quality of welded joints has been continuously improved, the variety specifications of welded steel pipes have been increasing, and more and more fields have replaced Seam steel pipe. Welded steel pipes are divided into straight welded pipes and spiral welded pipes in the form of welds. 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.

Welded steel pipe Standard low-pressure fluid transmission welded steel pipe (GB/T3092-1993) is also called general welded pipe, commonly known as black pipe. It is a welded steel pipe used for conveying general lower pressure fluids such as water, gas, air, oil and heating steam and other purposes. The thickness of the steel pipe is divided into ordinary steel pipe and thick steel pipe; the pipe end form is divided into non-threaded steel pipe (light pipe) and threaded steel pipe. The specification of the steel pipe is expressed by the nominal diameter (mm), and the nominal diameter is an approximate value of the inner diameter. It is customary to use inches, such as 11/2. The welded steel pipe for low-pressure fluid transportation is mainly used as a raw pipe for galvanized welded steel pipe for low-pressure fluid transportation, in addition to being directly used for conveying fluid.

Galvanized welded steel pipe Standard galvanized welded steel pipe for low-pressure fluid transportation (GB/T3091-1993) is also called galvanized electric welded steel pipe, commonly known as white tube. It is a hot dip galvanizing (furnace welding or electric welding) steel pipe for transporting water, gas, air oil, heating steam, warm water and other general lower pressure fluids or other purposes. The thickness of the steel pipe is divided into ordinary galvanized steel pipe and thick galvanized steel pipe; the connection end form is divided into non-thread galvanized steel pipe and threaded galvanized steel pipe. The specification of the steel pipe is expressed by the nominal diameter (mm), and the nominal diameter is an approximate value of the inner diameter.

Welded steel pipe use ordinary carbon steel wire casing (GB3640-88) is a steel pipe used to protect electric wires in electrical installation projects such as industrial and civil construction, installation machinery and equipment. Straight seam electric welded steel pipe (YB242-63) is a steel pipe whose weld is parallel to the longitudinal direction of the steel pipe. Usually divided into metric electric welded steel pipe, welded thin-walled pipe, transformer cooling oil pipe and so on. Spiral submerged arc welded steel pipe (SY5036-83) for pressure fluid conveying is a hot rolled steel strip coil for tube blank, which is often spirally formed by a double-sided submerged arc welding method and used for spiral conveying of pressurized fluid. Steel Pipe. The steel pipe has strong pressure bearing capacity and good welding performance. It is safe and reliable after various strict scientific tests and tests. The steel pipe has a large caliber, high conveying efficiency, and can save investment in laying pipelines.

It is mainly used to transport oil and natural gas pipelines. Spiral seam high-frequency welded steel pipe (SY5038-83) for pressurized fluid conveying is a spiral of hot-rolled steel strip, which is often spiral-formed by high-frequency lap welding and used for the conveying of pressurized fluid. High-frequency welded steel pipe. The steel pipe has strong pressure bearing capacity and good plasticity, which is convenient for welding and processing. After various strict and scientific inspections and tests, the use is safe and reliable, the steel pipe has large caliber, high conveying efficiency, and can save investment in laying pipelines. It is mainly used for laying pipelines for transporting oil and natural gas.

Generally, the spiral submerged arc welded steel pipe (SY5037-83) for low-pressure fluid transportation is made of hot-rolled steel strip as a tube blank, which is often spiral-formed by a double-sided automatic submerged arc welding or single-sided welding method for water. Submerged arc welded steel pipe for general low pressure fluid transportation such as gas, air and steam. Generally, spiral high-frequency welded steel pipe (SY5039-83) for low-pressure fluid transportation is a hot-rolled steel strip coil for tube blank, which is often spiral-formed by high-frequency lap welding and used for high-pressure fluid conveying. Frequency welded steel pipe. Spiral welded steel pipe (SY5040-83) for piles is made of hot-rolled steel strip coils, often spiral-formed by double-sided submerged arc welding or high-frequency welding, used for civil engineering structures, wharfs and bridges. Wait for the foundation pile.

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