Types of Seamless Steel Pipes

Date:2024-07-05Tags:Seamless Steel Pipe, steel pipe, ASTM A252
What is a seamless steel pipe? It is a steel pipe without gaps. Because it is more convenient and has more advantages than ordinary steel pipes, the modern construction industry prefers to use seamless steel pipes. Today, the editor will bring you the classification and specifications of seamless steel pipes.Seamless steel pipes are integral to modern construction, industrial, and engineering fields due to their high strength, excellent corrosion resistance, and broad application range. These pipes, which lack any welded seams and are formed as a single piece, can be classified based on their uses, materials, production processes, and shapes. This article will provide a detailed overview of the various types of seamless steel pipes, their characteristics, and their applications across different industries.

Classification of Seamless Steel Pipes

By Use
Hydraulic Pipes: Hydraulic pipes are primarily used in hydraulic systems for conveying fluids and transmitting pressure. Given the high precision and pressure requirements in hydraulic systems, these pipes are typically made from high-strength, high-precision seamless steel.

Boiler Pipes: Boiler pipes are used in both industrial and domestic boilers for high-temperature and high-pressure fluid transport. They can be categorized into low and medium pressure boiler pipes and high-pressure boiler pipes. Low and medium pressure boiler pipes are made from materials such as 10# and 20# steel, while high-pressure boiler pipes, used in power plants and nuclear power plants, are made from materials like 20G, 12Cr1MoVG, and 15CrMoG.

Fluid Pipes: Fluid pipes transport water, oil, gas, and other fluids. The materials used depend on the fluid being transported. For corrosive fluids, stainless steels like 0Cr13 and 0Cr18Ni9 are used. For non-corrosive fluids, carbon steels or low alloy steels like 20# steel and Q345 are commonly used.

Firefighting Pipes: Firefighting pipes are used in firefighting systems to transport water or other extinguishing agents. These pipes must have good pressure resistance and corrosion resistance to ensure reliable performance during emergencies.

Pipeline Pipes: Pipeline pipes transport oil and natural gas over long distances. They require high strength and excellent corrosion resistance. Common materials include X42, X52, and X60.

Structural Pipes: Structural pipes are used in building and mechanical structures, requiring good mechanical properties and corrosion resistance. Common materials include 20#, 45#, 20Cr alloy steel, 40Cr alloy steel, and 42CrMo alloy steel.

Mechanical Pipes: Mechanical pipes are used to manufacture various mechanical parts, such as automotive drive shafts and oil drilling rods. These pipes require high precision and good mechanical properties, with materials like 45#, 40Cr, and 20CrMo being typical choices.

By Material:Seamless steel pipes can be made from various materials, including carbon steel, alloy steel, and stainless steel:

Carbon Steel: Carbon steel seamless pipes are mainly used for general structures and mechanical structures, such as building pipes and mechanical parts. Common grades include 20# and 45# steel.

Alloy Steel: Alloy steel seamless pipes, which add alloying elements to carbon steel, offer better mechanical properties and corrosion resistance. Common grades include Q345, 20Cr, 40Cr, and 42CrMo.

Stainless Steel: Stainless steel seamless pipes are used for transporting corrosive media and in high-temperature, high-pressure environments. They offer excellent corrosion resistance and mechanical properties. Common grades include 0Cr13, 0Cr18Ni9, and 1Cr19Ni11Nb.

By Production Process:Seamless steel pipes can be classified based on their production processes into hot-rolled, cold-rolled, cold-drawn, and extruded seamless pipes:

Hot-Rolled Seamless Pipes: These pipes are formed by rolling steel billets at high temperatures. They offer large dimensions and high production efficiency, with common diameters ranging from 32mm to 600mm.

Cold-Rolled Seamless Pipes: Cold-rolled pipes are formed at room temperature, providing high precision and good surface finish. Their common diameters range from 4mm to 200mm.

Cold-Drawn Seamless Pipes: These pipes are formed by drawing steel billets through a die at room temperature, offering high dimensional accuracy and surface finish. They are used for high-precision mechanical parts.

Extruded Seamless Pipes: Extruded pipes are formed by extruding steel billets through a die under high temperature and pressure, offering high dimensional accuracy and surface finish. They are used for high-precision and high-strength applications.


Seamless Steel Pipes


By Cross-Section Shape:Seamless steel pipes can have various cross-sectional shapes, including round, square, oval, and triangular:

Round Seamless Pipes: Round seamless pipes are the most common shape, offering simple manufacturing processes, high strength, and widespread use.

Square Seamless Pipes: Square seamless pipes have square or rectangular cross-sections, primarily used in building and mechanical structures, offering good bending and compression resistance.

Oval Seamless Pipes: Oval seamless pipes have an oval cross-section, used for decorative and special structures, providing unique appearance and good mechanical properties.

Triangular Seamless Pipes: Triangular seamless pipes have a triangular cross-section, used in special structures and mechanical parts, offering unique appearance and good mechanical properties.

By Wall Thickness
Seamless steel pipes can be classified by wall thickness into thick-walled and thin-walled seamless pipes:

Thick-Walled Seamless Pipes: These pipes have a large wall thickness, offering high strength and good pressure resistance. They are used in high-pressure and high-strength environments, such as high-pressure boiler pipes and oil well pipes.

Thin-Walled Seamless Pipes: Thin-walled pipes have a small wall thickness, offering lightweight and easy processing, mainly used for general structures and fluid transport, such as low and medium pressure boiler pipes and fluid pipes.

Applications of Seamless Steel Pipes
Due to their excellent mechanical properties and wide range of applications, seamless steel pipes are used in various fields.

Construction
In the construction field, seamless steel pipes are used for structural support, steel structure buildings, bridges, and more. Their high strength and excellent corrosion resistance make them indispensable in construction structures.

Mechanical Manufacturing
Seamless steel pipes are widely used in mechanical manufacturing to make various mechanical parts and equipment, such as automotive drive shafts, oil drilling rods, and bearings. Their high precision and good mechanical properties make them essential in mechanical manufacturing.

Oil and Gas
In the oil and gas field, seamless steel pipes are used for oil well pipes, oil pipelines, and gas pipelines. Their high strength and excellent corrosion resistance enable them to be used in harsh environments for long periods, ensuring safe and efficient oil and gas transport.

Chemical and Pharmaceutical
In the chemical and pharmaceutical fields, seamless steel pipes are used for transporting corrosive media and high-temperature, high-pressure fluids. Their excellent corrosion resistance and high strength allow them to be used in harsh chemical environments for long periods, ensuring safe and efficient fluid transport.

Boilers and Pressure Vessels
In the boiler and pressure vessel fields, seamless steel pipes are used for transporting high-temperature, high-pressure fluids. Their high strength and excellent corrosion resistance allow them to be used in high-temperature, high-pressure environments for long periods, ensuring safe and efficient operation of boilers and pressure vessels.

Shipbuilding
In the shipbuilding field, seamless steel pipes are used for ship boilers and superheaters. Their high strength and excellent corrosion resistance allow them to be used in marine environments for long periods, ensuring the safe and efficient operation of ships.

Manufacturing Process of Seamless Steel Pipes
The manufacturing process of seamless steel pipes includes the following steps:

Raw Material Inspection: Inspect the composition and performance of the hot-rolled coils to ensure the quality of the raw materials meets the requirements.

Uncoiling and Welding: Uncoil the steel strip, level it, and use submerged arc welding to weld the tail of the previous coil to the head of the next coil, feeding it into the accumulator.

Accumulator Storage: Use an external-internal, bottom-in-top-out spiral accumulator to ensure continuous production.

Edge Milling: Mill the edges of the steel strip to a width of 1884mm to ensure high-quality forming and welding.

Pipe Forming: Bend the steel strip into a circular pipe through a series of rollers.

Pipe Welding: Use argon protection welding, supplying gas uniformly above the welding area to suppress oxidation of the metal in the welding zone. Control welding power within 1000KW, welding speed at 7±2m/min, welding opening angle at 5°, and extrusion amount at 10mm to ensure weld quality.

Weld Heat Treatment: Heat treat the weld at 950℃ to 1050℃ to ensure fine microstructure, enhancing strength and toughness.

Air and Water Cooling: Air cool the weld over a 60-meter air cooling section, keeping the temperature below 80℃ after the water cooling tank to ensure dimensional stability.

Sizing: Control the reduction amount in the sizing section between 2-4mm to ensure pipe dimensions and ovality meet the requirements.

Ultrasonic Testing: Perform manual ultrasonic testing on the weld and the area 50mm above and below the weld to ensure weld quality.

Advantages of Seamless Steel Pipes
Compared to other types of steel pipes, seamless steel pipes offer several advantages:

Lightweight: Seamless steel pipes are lightweight, making them easier to transport and install, reducing construction costs.

Excellent Corrosion Resistance: Seamless steel pipes have excellent corrosion resistance, suitable for transporting various corrosive media.

High Temperature Resistance: Seamless steel pipes have good high-temperature resistance, suitable for transporting fluids in high-temperature environments.

Good Impact Resistance: Seamless steel pipes have good impact resistance, allowing them to be used for long periods in harsh environments.

High Tensile Strength: Seamless steel pipes have high tensile strength, suitable for use in high-strength environments.

Good Seismic Performance: Seamless steel pipes have good seismic performance, maintaining structural stability during earthquakes and other natural disasters.

Long Service Life: Seamless steel pipes have a long service life, reducing replacement and maintenance costs.

Ease of Processing: Seamless steel pipes are easy to process, suitable for manufacturing parts with complex shapes.

Conclusion
There are many types of seamless steel pipes, which are not listed here one by one. It should be noted that when choosing seamless steel pipes, you should pay attention to choosing the right ones and choose them in the right channels. The preservation of seamless steel pipes also needs attention. In order to avoid damage to the material, I hope everyone will handle it properly.

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