Seamless carbon steel pipe is a long steel strip with a hollow cross-section, which is widely used as a pipeline for conveying fluids, such as pipelines for conveying oil, natural gas, coal gas, water and some solid materials. Compared with solid steel such as round steel, steel pipe has the same bending and torsional strength but is lighter in weight. It is an economical cross-section steel and is widely used in manufacturing structural parts and mechanical parts, such as oil drill pipes, automobile drive shafts, bicycle frames, and steel scaffolding used in construction.
Dimensional specifications of seamless carbon steel pipes
1. Outer diameter (D)
Range: 6mm～630mm (small diameter tubes are commonly 6-108mm, large diameter tubes can reach 108-630mm).
Precision grade:
Ordinary grade: tolerance ±1%～±1.5% (e.g. outer diameter 100mm, tolerance ±1-1.5mm);
High precision grade: tolerance ±0.5%～±1% (cold rolled/cold drawn tube, used for precision machinery).
2. Wall thickness (t)
Range: 1mm~40mm (thin-wall tube 1-10mm, thick-wall tube 10-40mm).
Representation method:
Single wall thickness: such as "Φ108×4" means outer diameter 108mm, wall thickness 4mm;
Wall thickness coefficient: such as Sch40, Sch80 (American standard system, corresponding to different pressure levels).
3. Length (L)
Fixed length: Commonly 6m, 9m, 12m (for easy transportation and construction);
Variable length: Usually 4-12m (cut according to actual production needs);
Multiple length: Customized according to user requirements (such as 12m=3×4m, need to increase the cutting margin).
Material factors of seamless carbon steel pipe
1. Importance of the structure: For important structures such as heavy industrial building structures, large-span structures, high-rise or super-high-rise civil building structures or structures, good quality seamless steel pipes should be considered. For general industrial and civil building structures, ordinary quality seamless steel pipes can be selected according to the nature of the work.
2. Load conditions: Structures that directly bear dynamic loads and structures in strong earthquake zones should use seamless steel pipes with good comprehensive performance; structures that generally bear static loads can use lower-priced seamless steel pipes.
3. Connection method: The welding process will produce welding deformation, welding stress and other welding defects, which may cause cracks or brittle fractures in the structure. Therefore, the requirements for materials of welded structures should be stricter.
4. Thickness of seamless carbon steel pipe: Thin seamless steel pipes are rolled many times, and the compression ratio of rolling is large. The compression ratio of thick seamless steel pipes is small, so the thickness of precision steel pipes is not only small in strength, but also in plasticity, impact toughness and welding performance. Therefore, thick welded structures should use seamless steel pipes with better materials.
Advantages of Seamless Carbon Steel Pipes
1. High strength: Seamless carbon steel pipes have high strength and hardness, can withstand greater pressure and weight, and are suitable for high-pressure, high-temperature, and high-strength working environments, such as oil and natural gas pipelines, transmission shafts in machinery manufacturing, etc.
2. Good processing performance: easy to cut, weld, bend and other processing operations, can be made into pipes of various shapes and sizes according to different engineering requirements, the manufacturing process is relatively simple, the production cost is low, and it can meet the needs of large-scale production.
3. Economical and affordable: Compared with seamless tubes made of stainless steel, alloy steel and other materials, seamless carbon steel pipes are relatively cheap and have a higher cost-effectiveness. In some occasions where corrosion resistance is not required, the use of seamless carbon steel pipes can effectively reduce engineering costs.
4. Good thermal conductivity: Carbon steel has a high thermal conductivity, which makes it advantageous in some applications that require good thermal conductivity, such as pipes in heat exchangers, boilers and other equipment, which can effectively transfer heat and improve energy efficiency.
Read more: Selection Principles of Seamless Carbon Steel Pipes
