Seamless Tube Overview
• Definition: Seamless steel pipe is a steel pipe made by piercing a single round steel bar, with no seam on the surface. Its manufacturing process involves piercing a solid billet or steel ingot into a hollow tube, which is then hot-rolled, cold-rolled, or cold-drawn into a finished steel pipe.
• Characteristics: It possesses advantages such as high strength, good toughness, strong corrosion resistance, high temperature resistance, and high pressure resistance, enabling it to adapt to complex and harsh working environments.
• Application Areas: Widely used in petroleum, natural gas, chemical, power, boiler, machinery manufacturing, automotive, aerospace, and many other fields.
• Grades: 10, 20, Q345, Q390, Q420, Q460
Product Introduction
| Type |
OD (mm) |
Wall Thickness (mm) |
Grade |
Standard |
Application |
| Structural Pipe |
φ38–356 |
3.5–40 |
20, 35, 45, 295, Q345 |
GB/T8162-2018, ASTM A53 |
General structures, mechanical structures |
| Fluid Pipe |
φ38–356 |
3.5–40 |
20, Q295A, Q295B, Q345A, Q345B |
GB/T8163-2018, ASTM A106 |
Transport of oil, natural gas, coal gas, water and some solids |
| Hydraulic Cylinder Pipe |
φ89–356 |
4.5–40 |
20, 35, 45, 27SiMn |
GB/T17396-2009 |
Machinery, mining, hydraulic cylinders and engineering equipment |
| Oil Pipe |
φ60.3–114.3 |
5.49–12.7 |
J55, K55, N80-1 |
API 5CT |
Oil industry tubing |
| Casing Pipe |
φ139.7–339.7 |
6.20–13.84 |
J55, K55, N80-1 |
API 5CT |
Oil industry casing |
| Line Pipe |
φ42.2–355.6 |
4.85–19.05 |
API 5L B–X56 series |
API 5CT |
Oil and gas pipelines |
• Difference between seamless structural pipes and seamless fluid pipes: The main difference is that seamless fluid pipes undergo individual hydraulic testing or ultrasonic, eddy current, and magnetic flux leakage testing.
Hydraulic support pipes are materials used to manufacture hydraulic supports, cylinders, and columns for coal mines, as well as other hydraulic cylinders and columns. They are mainly used in hydraulic equipment in coal mining, such as hydraulic supports, cylinders, and plungers.
• Tubing is used to extract oil or natural gas from oil wells; casing is used as the wellbore for oil and gas wells.
• Major importing countries for oil casing include: Germany, Japan, Romania, Czech Republic, Italy, United Kingdom, Austria, Switzerland, United States, Argentina, and Singapore. Import standards mostly refer to the American Petroleum Institute standards.
• Line pipes: These transport oil, gas, or water extracted from the surface to oil and gas industrial enterprises. Pipe ends include plain ends, threaded ends, and socket ends; connection methods include welding, coupling connections, and socket connections.
Manufacturing process
Hot rolling process:
The billet is heated to above the recrystallization temperature, and then gradually deformed into a seamless tube by the extrusion action of the rolls. It is suitable for large-scale production and can produce large-diameter, thick-walled seamless tubes.
Cold rolling process:
Seamless tubes are rolled at room temperature, which further improves the dimensional accuracy and surface quality of the steel tubes. The resulting steel tubes have the characteristics of high dimensional accuracy, good surface finish, and excellent mechanical properties.
Cold drawing process:
At room temperature, the seamless tube is pulled out of the mold by external force, reducing the diameter and wall thickness of the steel tube to obtain the required size and precision. Cold-drawn steel tubes have high dimensional accuracy and surface quality and are often used to manufacture high-precision, high-strength seamless tubes.
Production process
Walking beam furnace High-speed hot saw Conical piercing Continuous rolling Tube removal
Dust blowing and suction Straightening Pipe cutting to length Cooling Tension reduction Induction heating
Non-destructive testing Manual inspection UV painting Marking Automatic packaging Weighing and warehousing
Quality control
Ø Appearance Quality Inspection: Visual inspection and magnification are used to check the surface of the steel pipe for defects such as cracks, folds, scratches, and pitting. For steel pipes with high surface quality requirements, non-destructive testing methods such as eddy current testing and magnetic particle testing can also be used.
Ø Physical and Chemical Property Testing: The chemical composition, mechanical properties, and metallographic structure of the seamless pipe are tested to ensure that the material of the steel pipe meets the standard requirements, the mechanical properties meet the usage requirements, and the metallographic structure is uniform and fine.
Comparison of seamless pipes and ordinary steel pipes
| Type |
Seamless Pipe |
Ordinary Steel Pipe |
| Manufacturing Process |
Hot rolling, cold rolling, cold drawing and other processes |
Steel strip heating, rolling, cooling and other processes |
| Appearance |
Round or oval shape, smooth surface without weld seam |
Round, rectangular, square, with weld seam |
| Performance |
High strength, good toughness, strong corrosion resistance, high temperature and pressure resistance; suitable for complex and harsh working environments |
Relatively lower strength and toughness |
| Application Fields |
Manufacturing, petroleum, natural gas, chemical industry, power, boilers, automobiles, aerospace and other fields |
Manufacturing, construction, machinery, automobiles and other fields |
In summary, compared with ordinary steel pipes, seamless pipes have advantages such as better appearance, no weld seams on the surface, higher strength and toughness, and wider application range.
Product Advantages-Advantages of seamless pipes
1. High Strength and Wear Resistance
Seamless pipes have uniform material thickness and a smooth surface, giving them very high strength. They can withstand high loads and maintain their strength even under high pressure and high temperature conditions.
2. Corrosion Resistance
Since seamless pipes have no weld seams or joints, their inner and outer surfaces are smooth and free from deposits and impurities. They can effectively resist corrosion from acids, alkalis, salts, and atmospheric environments, helping maintain pipeline integrity and extend service life.
3. Strong Pressure Resistance
Seamless pipes are suitable for high-pressure pipeline systems. Under high pressure, they do not deform or burst, ensuring stable and safe operation.
4. High Temperature & Impact Resistance
They offer excellent resistance to high temperatures, impact, and fatigue. No frequent maintenance is required, and the service life can exceed 15 years.
5. Excellent Mechanical Properties
The tensile strength of seamless pipes is 8–10 times higher than that of ordinary steel. They also have superior elastic modulus, excellent creep resistance, and seismic resistance. In addition, they are easy to machine and meet various engineering requirements.
6. High Elasticity
Seamless pipes have high elasticity and can be repeatedly used in mechanical equipment without deformation or memory effect. They also have antistatic properties, ensuring stable equipment operation.
