The difference between seamless pipe and welded pipe

1. Classification according to production method

(1) Seamless pipe - hot-rolled pipe, cold-rolled pipe, cold-drawn pipe, extruded pipe, pipe jacking

(2) Welded pipes

(a) According to the process - arc welded pipe, resistance welded pipe (high frequency, low frequency), gas welded pipe, furnace welded pipe (b) According to weld seam - straight seam welded pipe, spiral welded pipe

2. Classify according to the shape of the section

(1) Simple section steel pipe - round steel pipe, square steel pipe, oval steel pipe, triangular steel pipe, hexagonal steel pipe, diamond steel pipe, octagonal steel pipe, semicircular steel circle, etc

(2) Complex section steel pipes - unequal sides hexagonal steel pipes, five-petal plum blossom shaped steel pipes, double convex steel pipes, double concave steel pipes, melon seed shaped steel pipes, conical steel pipes, corrugated steel pipes, case steel pipes, and others

3. Classification according to wall thickness - thin-walled steel pipe, thick-walled steel pipe

4. Classification by use - steel pipes for pipelines, steel pipes for thermal equipment, steel pipes for machinery industry, steel pipes for petroleum and geological drilling, steel pipes for containers, steel pipes for chemical industry, steel pipes for special purposes, and others

2. Seamless steel pipe

It is a long strip of steel with a hollow section and no seams around the perimeter. Steel pipes have a hollow section and are widely used as pipelines for transporting fluids, such as pipelines for transporting oil, natural gas, gas, water and certain solid materials. Compared with solid steel such as round steel, steel pipe has the same bending and torsional strength, lighter weight, and is an economical cross-sectional steel, which is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile drive shafts, bicycle racks, and steel scaffolding used in building construction. The manufacture of ring parts from steel pipes can improve material utilization, simplify the manufacturing process, save materials and processing time, such as rolling bearing ferrules, jack sleeves, etc., and have been widely manufactured by steel pipes. Steel pipes are also indispensable materials for various conventional weapons, and barrels, barrels, etc. must be made by steel pipes. Steel pipes can be divided into round pipes and special-shaped pipes according to different cross-sectional area shapes. Since the circle area is the largest under the condition of equal circumference, more fluid can be transported with a circular tube. In addition, the torus section is subjected to uniform force when subjected to internal or external radial pressure, so the vast majority of steel pipes are round pipes. However, round pipes also have certain limitations, such as under the condition of plane bending, round pipes are not as strong as square and rectangular pipes, and some agricultural machinery skeletons, steel and wood furniture are commonly used square and rectangular pipes. According to different uses, there are also special-shaped steel pipes with other cross-sectional shapes.

1. Seamless steel pipe for structure (GB/T8162-1999) is a seamless steel pipe used for general structure and mechanical structure.

2. Seamless steel pipe for fluid transportation (GB/T8163-1999) is a general seamless steel pipe used to transport water, oil, gas and other fluids.

3. Seamless steel pipe for low and medium pressure boilers (GB3087-1999) is a high-quality carbon structural steel hot-rolled and cold-drawn (rolled) seamless steel pipe for the manufacture of superheated steam pipes, boiling water pipes and superheated steam pipes, large smoke pipes, small smoke pipes and arch brick pipes for locomotive boilers of various structures.

4. Seamless steel pipe for high-pressure boiler (GB5310-1995) is a high-quality carbon steel, alloy steel and stainless heat-resistant steel seamless steel pipe for the heating surface of water tube boilers with high pressure and above pressure.

5. High-pressure seamless steel pipe for fertilizer equipment (GB6479-86) is a high-quality carbon structural steel and alloy steel seamless steel pipe suitable for chemical equipment and pipelines with a working temperature of -40~400°C and a working pressure of 10~30Ma.

6. Seamless steel pipe for petroleum cracking (GB9948-88) is a seamless steel pipe suitable for furnace tubes, heat exchangers and pipelines in petroleum refineries.

7. Steel pipe for geological drilling (YB235-70) is a steel pipe used by geological departments for core drilling, which can be divided into drill pipe, drill collar, core pipe, casing and sedimentation pipe according to the purpose.

8. Seamless steel pipe for diamond core drilling (GB3423-82) is a seamless steel pipe for drill pipe, core rod and casing used for diamond core drilling.

9. Oil drilling pipe (YB528-65) is a seamless steel pipe used for thickening inside or outside at both ends of oil drilling. Steel pipes are divided into two types: wire and non-wire, wire pipes are connected by joints, and wire pipes are connected with tool joints by butt welding.

10. Carbon steel seamless steel pipe for ships (GB5213-85) is a carbon steel seamless steel pipe for manufacturing ship Class I pressure-resistant pipe system, Class II pressure-resistant pipe system, boiler and superheater. The working temperature of carbon steel seamless steel pipe wall does not exceed 450 °C, and the working temperature of alloy steel seamless steel pipe wall exceeds 450 °C.

11. Seamless steel pipe for automobile half shaft casing (GB3088-82) is a high-quality carbon structural steel and alloy structural steel hot-rolled seamless steel pipe for manufacturing automobile half shaft bushings and drive axle axle shell shaft pipes.

12. High-pressure oil pipe for diesel engine (GB3093-86) is a cold-drawn seamless steel pipe for manufacturing high-pressure pipe for diesel engine injection system.

13. Precision inner diameter seamless steel pipe for hydraulic and pneumatic cylinder barrel (GB8713-88) is a cold-drawn or cold-rolled precision seamless steel pipe with precise inner diameter size for manufacturing hydraulic and pneumatic cylinder barrels.

14. Cold-drawn or cold-rolled precision seamless steel pipe (GB3639-83) is a cold-drawn or cold-rolled precision seamless steel pipe with high dimensional accuracy and good surface finish for mechanical structures and hydraulic equipment. The selection of precision seamless steel pipes to manufacture mechanical structures or hydraulic equipment can greatly save machining man-hours, improve material utilization, and help improve product quality.

15. Structural stainless steel seamless steel pipe (GB/T14975-1994) is a hot-rolled (extrusion, expansion) and cold-drawn (rolled) seamless steel pipe made of stainless steel widely used in corrosion-resistant pipes and structural parts and parts of chemical, petroleum, textile, medical, food, machinery and other industries.

16. Stainless steel seamless steel pipe for fluid conveying (GB/T14976-1994) is a hot-rolled (extrusion, expansion) and cold-drawn (rolled) seamless steel pipe made of stainless steel for transporting fluids.

17. Special-shaped seamless steel pipe is a general term for seamless steel pipes with other cross-sectional shapes except round pipes. According to the different shapes and sizes of steel pipes, they can be divided into equal wall thickness special-shaped seamless steel pipes (code name D), unequal wall thickness special-shaped seamless steel pipes (code name BD), and variable diameter special-shaped seamless steel pipes (code name BJ). Special-shaped seamless steel pipes are widely used in various structural parts, tools and mechanical parts. Compared with round pipes, special-shaped pipes generally have a larger moment of inertia and cross-sectional modulus, and have greater bending and torsion resistance, which can greatly reduce the weight of the structure and save steel.

3. Welded steel pipe Welded steel pipe, also known as welded pipe, is a steel pipe made of steel plate or steel strip after crimping and forming. The production process of welded steel pipes is simple, the production efficiency is high, there are many varieties and specifications, and the equipment capital is less, but the general strength is lower than that of seamless steel pipes. Since the 30s of the 20th century, with the rapid development of high-quality strip continuous rolling production and the progress 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 have replaced seamless steel pipes in more and more fields. Welded steel pipes are divided into straight seam welded pipes and spiral welded pipes according to the form of welds. The production process of straight seam welded pipe is simple, with high production efficiency, low cost and rapid development. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes, and can produce welded pipes with larger pipe diameters from narrower billets, and can also produce welded pipes with different pipe diameters from billets of the same width. However, compared with the same length of straight seam pipe, the weld length is increased by 30~100%, and the production speed is lower. Therefore, most of the smaller diameter welded pipes are straight seam welding, and most of the large diameter welded pipes are spiral welded.

1. Welded steel pipe for low-pressure fluid transportation (GB/T3092-1993) is also known as general welded pipe, commonly known as black pipe. It is a welded steel pipe used to transport general lower pressure fluids such as water, gas, air, oil and heating steam and other uses. The thickness of the steel pipe is divided into ordinary steel pipe and thickened steel pipe; The pipe end form is divided into unthreaded steel pipe (fluorescent pipe) and threaded steel pipe. The specifications of steel pipes are expressed in nominal diameter (mm), which is an approximation of the inner diameter. It is customary to use inches to express it, such as 11/2, etc. In addition to being directly used for transporting 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 known as galvanized welded steel pipe, commonly known as white pipe. It is a hot-dip galvanized welded (furnace welding or electric welding) steel pipe used for transporting water, gas, air oil, heating steam, warm water and other general low-pressure fluids or other purposes. The thickness of the steel pipe joints is divided into ordinary galvanized steel pipes and thickened galvanized steel pipes; The pipe end form is divided into unthreaded galvanized steel pipe and threaded galvanized steel pipe. The specifications of steel pipes are expressed in nominal diameter (mm), which is an approximation of the inner diameter. It is customary to use inches to express it, such as 11/2, etc.

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, installation machinery and equipment.

4. Straight seam welded steel pipe (YB242-63) is a steel pipe with a longitudinal parallel weld and steel pipe. It is usually divided into metric welded steel pipe, welded thin-walled pipe, and transformer cooling oiltubes and so on.

5. Spiral seam submerged arc welded steel pipe (SY5036-83) for pressure-bearing fluid transportation is a spiral seam steel pipe used for pressure-bearing fluid transportation using hot-rolled steel strip coil as pipe blank, often spiral forming, and welding by double-sided submerged arc welding method. The steel pipe has strong pressure bearing capacity, good welding performance, and has undergone various strict scientific inspections and tests, making it safe and reliable to use. The diameter of the steel pipe is large, the conveying efficiency is high, and the investment in laying pipelines can be saved. It is mainly used for pipelines that transport oil and natural gas.

6. Spiral seam high-frequency welded steel pipe (SY5038-83) for pressure-bearing fluid transportation is made of hot-rolled steel strip coil as pipe blank, often spirally formed, welded by high-frequency lap welding method, spiral seam high-frequency welded steel pipe for pressure-bearing fluid transportation. The steel pipe has strong pressure bearing capacity and good plasticity, which is easy to weld and process. After all kinds of strict and scientific inspection and testing, it is safe and reliable to use, with large steel pipe diameter, high conveying efficiency, and can save investment in laying pipelines. It is mainly used for laying pipelines for transporting oil, natural gas, etc.

7. The spiral seam submerged arc welded steel pipe (SY5037-83) for general low-pressure fluid transportation is made of hot-rolled steel strip coil as the pipe blank, often spirally formed, and is made of double-sided automatic submerged arc welding or single-sided welding method for general low-pressure fluid transportation such as water, gas, air and steam.

8. General spiral seam high-frequency welded steel pipe for low-pressure fluid transportation (SY5039-83) is made of hot-rolled steel strip coil as pipe blank, often spirally formed, and welded by high-frequency lap welding method for general low-pressure fluid transportation spiral seam high-frequency welded steel pipe.

9. Spiral welded steel pipe for piles (SY5040-83) is made of hot-rolled steel strip coil as pipe blank, often spiral formed, double-sided submerged arc welding or high-frequency welding, used for civil building structures, docks, bridges and other foundation pile steel pipes.

4. Steel-plastic composite pipes and large-diameter coated steel pipes

The steel-plastic composite pipe is made of hot-dip galvanized steel pipe as the matrix, and the inner wall (the outer wall can also be coated with plastic) by powder melt spraying technology, with excellent performance. Compared with galvanized pipes, it has the advantages of anti-corrosion, no rust, no scale, 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 pipes, it has the advantages of high mechanical strength, pressure resistance, and good heat resistance. Since the matrix is steel pipe, there is no problem of embrittlement and aging. It can be widely used in fluid transportation and heating projects such as tap water, gas, and chemical products, and is an upgraded product of galvanized pipe. Because its installation and use method is basically the same as that of traditional galvanized pipes, the form of pipe fittings is also exactly the same, and it can replace aluminum-plastic composite pipes to play a role in large-diameter tap water transportation, which is very popular with users and has become one of the most competitive new products in the pipeline market. Coated steel pipe is coated with plastic on the basis of large-diameter spiral welded pipe and high-frequency welded pipe, the maximum pipe mouth diameter is up to 1200mm, and can be coated with polyvinyl chloride (PVC), polyethylene (PE), epoxy resin (EPOZY) and other plastic coatings with different properties according to different needs, good adhesion, strong corrosion resistance, strong resistance to strong acid, strong alkali and other chemical corrosion, non-toxic, non-rust, wear-resistant, impact resistant, strong penetration resistance, smooth pipeline surface, do not adhere to any substance, can reduce the resistance during transportation, Improve flow and conveying efficiency, and reduce conveying pressure loss. There is no solvent in the coating, no leachable substances, so it will not pollute the conveyed medium, so as to ensure the purity and hygiene of the fluid, and can be used alternately in the range of -40°C to +80°C with hot and cold cycles, without aging or cracking, 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, medicine, communications, electric power, marine and other engineering fields.