Welded steel pipe, also known as welded pipe, is a steel pipe made of steel plate or steel strip after crimping and welding. Welded steel pipe has simple production process, high production efficiency, many varieties and specifications, and less equipment investment, but its general strength is lower than that of seamless steel pipe. Since the 1930s, with the rapid development of continuous rolling production of high-quality strip steel and the advancement of welding and inspection technology, the quality of welds has been continuously improved, and the varieties and specifications of welded steel pipes have increased day by day, and replaced seamless steel pipes in more and more fields. Seam steel pipe. Welded steel pipes are divided into straight seam welded pipes and spiral welded pipes according to the form of the weld seam.
The production process of straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is rapid. The strength of the spiral welded pipe is generally higher than that of the straight seam welded pipe, and the welded pipe with a larger diameter can be produced with a narrower billet, and welded pipes with different diameters can be produced with the same width billet. But compared with the straight seam pipe 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.
1. Welded steel pipes for low-pressure fluid transportation (GB/T3092-1993) are also called general welded pipes, commonly known as clarinet pipes. It is a welded steel pipe used for conveying water, gas, air, oil and heating steam and other general lower pressure fluids and other purposes. The wall thickness of the steel pipe is divided into ordinary steel pipe and thickened steel pipe; the form of the pipe end is divided into unthreaded 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 express in inches, such as 11/2 and so on. In addition to being directly used to transport fluids, welded steel pipes for low-pressure fluid transportation are also widely used as raw pipes for galvanized welded steel pipes for low-pressure fluid transportation.
2. Galvanized welded steel pipe for low-pressure fluid transportation (GB/T3091-1993) is also called galvanized electric welded steel pipe, commonly known as white pipe. It is a hot-dip galvanized welded (furnace welded or electric welded) steel pipe used for conveying water, gas, air oil, heating steam, warm water and other general lower pressure fluids or other purposes. The wall thickness of the steel pipe is divided into ordinary galvanized steel pipe and thickened galvanized steel pipe; the form of the pipe end is divided into non-threaded 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. It is customary to express in inches, such as 11/2 and so on.
3. Ordinary carbon steel wire casing (GB3640-88) is a steel pipe used to protect wires in electrical installation projects such as industrial and civil buildings, and installation of machinery and equipment.
4. Straight seam electric welded steel pipe (YB242-63) is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. It is usually divided into metric electric welded steel pipe, electric welded thin-walled pipe, transformer cooling oil pipe and so on.
5. The spiral seam submerged arc welded steel pipe for pressurized fluid transportation (SY5036-83) is made of hot-rolled steel strip coils, spirally formed at constant temperature, welded by double-sided submerged arc welding, and used for pressurized fluid transportation. Spiral seam steel pipe. The steel pipe has strong pressure bearing capacity and good welding performance. After various strict scientific inspections and tests, it is safe and reliable to use. The diameter of the steel pipe is large, the transmission efficiency is high, and the investment in laying pipelines can be saved. It is mainly used for pipelines transporting oil and natural gas.
6. Spiral seam high-frequency welded steel pipe for pressure fluid transportation (SY5038-83) is made of hot-rolled steel strip coils, spirally formed at constant temperature, welded by high-frequency lap welding, and used for pressure fluid transportation Spiral seam high frequency welded steel pipe. The steel pipe has strong pressure bearing capacity, good plasticity, and is convenient for welding and processing; after various strict and scientific inspections and tests, it is safe and reliable to use, the diameter of the steel pipe is large, the transmission efficiency is high, and the investment in laying pipelines can be saved. It is mainly used for laying pipelines for transporting oil and natural gas.
7. The spiral seam submerged arc welded steel pipe (SY5037-83) for general low-pressure fluid transportation is made of hot-rolled steel strip coils, spirally formed at constant temperature, and made by double-sided automatic submerged arc welding or single-sided welding. Submerged arc welded steel pipes for general low-pressure fluid transportation such as water, gas, air and steam.
8. Spiral seam high-frequency welded steel pipe for general low-pressure fluid transportation (SY5039-83) is made of hot-rolled steel strip coils, spirally formed at constant temperature, and welded by high-frequency lap welding for general low-pressure fluid transportation. Seam high frequency welded steel pipe.
9. Spiral welded steel pipe for piles (SY5040-83) is made of hot-rolled steel strip coils, spirally formed at constant temperature, and made by double-sided submerged arc welding or high-frequency welding. It is used for civil and architectural structures, docks, and bridges. Steel pipes for foundation piles.
Steel-plastic composite pipe, large-diameter coated steel pipe
The steel-plastic composite pipe is made of hot-dip galvanized steel pipe as the substrate, and the inner wall (or outer wall if necessary) is coated with plastic by powder fusion spraying technology, with excellent performance. Compared with galvanized pipe, it has the advantages of anti-corrosion, no rust, no fouling, smooth and smooth, clean and non-toxic, and long service life. According to tests, the service life of the steel-plastic composite pipe is more than three times that of the galvanized pipe. Compared with plastic pipes, it has the advantages of high mechanical strength, good pressure resistance and heat resistance. Since the substrate is a steel pipe, there is no problem of embrittlement or aging. It can be widely used in fluid transportation and heating projects such as tap water, gas, and chemical products. It is an upgraded product of galvanized pipes. Because its installation method is basically the same as that of the traditional galvanized pipe, and the form of the pipe fittings is also exactly the same, and it can replace the aluminum-plastic composite pipe to play a role in large-diameter tap water transportation. It is very popular among users and has become the most competitive pipe in the pipeline market. One of the new products.
Coated steel pipes are formed by coating plastic on the basis of large-diameter spiral welded pipes and high-frequency welded pipes. Resin (EPOZY) and other plastic coatings with different properties, good adhesion, strong corrosion resistance, strong acid, alkali and other chemical corrosion resistance, non-toxic, non-rusting, wear-resistant, impact resistance, strong penetration resistance , The surface of the pipeline is smooth and does not adhere to any substance, which can reduce the resistance during transportation, improve the flow rate and transportation efficiency, and reduce the loss of transportation pressure. There is no solvent and no exudable substances in the coating, so it will not pollute the conveyed medium, thus ensuring the purity and hygiene of the fluid. It can be used alternately in cold and hot cycles in the range of -40°C to +80°C, without aging, It does not crack, so it can be used in harsh environments such as cold regions.
Large-diameter coated steel pipes are widely used in tap water, natural gas, petroleum, chemical industry, medicine, communication, electric power, marine and other engineering fields.
