Classification of steel pipes part 2

Third, welded steel pipe

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. Therefore, most of the smaller diameter welded pipes are straight seam welded, and the large diameter welded pipes are mostly spiral welded.

1. Straight seam welded steel pipe for low pressure fluid transportation (GB/T 3092-2008) 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.

2. Welded steel pipe for low-pressure fluid transportation (GB/T 3091-2015) 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. It is customary to use inches, such as 11/2.

3. Ordinary carbon steel wire casing (GB 3640-88) is a steel pipe used to protect electric wires in electrical installation projects such as industrial and civil construction, installation machinery and equipment.

4. Straight seam electric welded steel pipe (GB/T 13793-2016) 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.

5. Spiral submerged arc welded steel pipe (SY 5036-83) for pressure fluid conveying is a hot rolled steel strip coil for tube blank, which is often spirally formed by double-sided submerged arc welding for pressure fluid transport. Spiral seam 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.

6. Spiral seam high-frequency welded steel pipe (SY 5038-83) for pressurized fluid conveying is a hot-rolled steel strip coil for tube blank, which is often spiral-formed by high-frequency lap welding for pressure-bearing fluid. Spiral seam high frequency welded steel pipe for conveying. 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.

7. General spiral spiral submerged arc welded steel pipe (SY5037-83) for low-pressure fluid transportation is made of hot-rolled steel strip coil for tube blank, regular temperature spiral forming, double-sided automatic submerged arc welding or single-sided welding method. Submerged arc welded steel pipes for general low-pressure fluid transportation such as water, gas, air and steam.

8. General spiral spiral high-frequency welded steel pipe (SY 5039-83) 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 for general low-pressure fluid transportation. Spiral seam high frequency welded steel pipe.

9. Spiral-welded steel pipe for piles (SY 5040-83) is made of hot-rolled steel strip coils, which is often spiral-formed by double-sided submerged arc welding or high-frequency welding. It is used for civil engineering structures. Steel pipes for foundation piles such as wharfs and bridges.

Fourth, steel-plastic composite pipe, large diameter coated steel pipe

The steel-plastic composite pipe is made of hot-dip galvanized steel pipe as a base material, and is coated with plastic on the inner wall (if necessary, the outer wall is required) by powder melt-spraying technology, and the performance is excellent. Compared with galvanized pipe, it has the advantages of corrosion resistance, no rust, no fouling, smooth and smooth, clean and non-toxic, and long service life. According to tests, the service life of steel-plastic composite pipes is more than three times that of galvanized pipes. Compared with plastic tubes, 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, chemical products, etc. It is an upgraded product of galvanized pipe. Because the installation method is basically the same as that of the traditional galvanized pipe, the pipe form is also the same, and it can replace the aluminum-plastic composite pipe to play a role in the large-diameter tap water transportation. It has been welcomed by users and has become the most competitive in the pipeline market. One of the new products.

The coated steel pipe is made of plastic coated on the basis of large diameter spiral welded pipe and high frequency welded pipe. The maximum pipe diameter is up to 1200mm. It can be coated with polyvinyl chloride (PVC), polyethylene (PE) and epoxy according to different needs. 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-corrosive, wear-resistant, impact-resistant, high-permeability The surface of the pipe is smooth and does not adhere to any substance, which can reduce the resistance during transportation, increase the flow rate and transportation efficiency, and reduce the loss of transmission pressure. The coating has no solvent and no exudable substances, so it will not pollute the medium to be transported, thus ensuring the purity and hygienicity of the fluid. It can be used alternately in the range of -40 to +80, without aging or turtle. Cracked, so it can be used in harsh environments such as cold areas.

Large diameter coated steel pipes are widely used in tap water, natural gas, petroleum, chemical, pharmaceutical, telecommunications, electric power, marine and other engineering fields.

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