Carbon steel pipe, a widely used basic material in the industrial sector, plays a key role in industries such as petroleum, chemical engineering, and construction. Common carbon steel pipes are primarily categorized into two types: seamless steel pipe and welded steel pipe.
In terms of production process and structure, seamless steel pipe is formed through integral rolling or extrusion, without welded seams. It offers high overall strength and toughness, can withstand higher pressures and temperatures, and is suitable for applications requiring stringent pipe safety requirements.
Welded steel pipe, on the other hand, is manufactured by coiling and welding steel plates, with one or more welds. While this offers high production efficiency and low cost, its performance under high pressure and extreme environments is slightly inferior to that of seamless pipe.
For seamless steel pipe, Q235 and A36 are popular grades. Q235 steel pipe is a commonly used carbon structural steel grade in China. With a yield strength of 235 MPa, it offers excellent weldability and ductility at an affordable price. It is widely used in building structural support, low-pressure fluid pipelines, and other applications, such as residential water supply pipelines and the steel frame construction of ordinary factory buildings.
A36 carbon steel pipe is a US standard grade. Its yield strength is similar to Q235, but it offers superior tensile strength and impact toughness. It is widely used in low-pressure pipelines in machinery manufacturing and oil production, such as small mechanical parts processing and low-pressure oil pipelines in oil fields.
For welded steel pipe, Q235 welded steel pipe is also a popular grade. Due to its low cost and excellent welding performance, it is often used in city gas transmission and low-pressure water transmission projects. A36 welded pipe, on the other hand, is more commonly used in low-pressure industrial pipelines with certain strength requirements, such as low-pressure material transportation pipelines in small chemical plants.
| Comparison Dimensions | Q235 Steel Pipe | A36 Carbon Steel Pipe |
| Standard System | China National Standard (GB/T 700-2006 "Carbon Structural Steel") | American Society for Testing and Materials (ASTM A36/A36M-22 "Carbon Steel Plate, Shapes, and Bars for Structural Use") |
| Yield Strength (Minimum) | 235 MPa (thickness ≤ 16 mm) | 250 MPa (throughout the full thickness range) |
| Tensile Strength Range | 375-500 MPa | 400-550 MPa |
| Impact Toughness Requirements | A -40°C impact test is only required for certain grades (e.g., Q235D); no mandatory requirement for common grades. | Requirements: -18°C impact test (partial standards); low-temperature toughness slightly better than conventional Q235 grades |
| Main Application Scenarios | Civil construction (steel structures, supports), low-pressure water/gas pipelines, and general mechanical parts | Mechanical manufacturing (small and medium-sized components), oilfield low-pressure pipelines, industrial low-pressure fluid pipelines |
Overall, seamless and welded steel pipes each have their own advantages. When purchasing, customers should consider the pressure and temperature requirements of the specific application, as well as their budget, and choose a suitable grade, such as Q235 or A36, to ensure project quality and safety.
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Post time: Sep-03-2025