First, S355J2H Seamless Steel Pipe Grades
1. Chemical Composition
- Carbon: The carbon content in S355J2H steel typically does not exceed 0.24%. Carbon is one of the key elements determining steel’s strength. A moderate amount of carbon enhances its hardness and strength. However, excessive carbon content can reduce the steel’s toughness and weldability.
- Silicon: The silicon content is generally around 0.55%. Silicon primarily acts as a deoxidizer, while also increasing the steel’s strength and improving its elastic limit.
- Manganese: The manganese content is approximately 1.60%. Manganese significantly improves the steel’s strength, toughness, and wear resistance, and contributes to grain refinement and optimized internal microstructure, thereby enhancing the steel’s overall performance.
- Phosphorus and Sulfur: Phosphorus and sulfur are impurity elements in this steel. Phosphorus content typically does not exceed 0.035%, and sulfur content does not exceed 0.035%. These can negatively impact the steel’s toughness, weldability, and corrosion resistance, so their content must be strictly controlled.
- Other Alloying Elements: Small amounts of microalloying elements such as niobium, titanium, and vanadium may also be present. These elements can improve the steel’s strength and toughness through grain refinement and precipitation strengthening.
2. Mechanical Properties
- Yield Strength: The minimum yield strength of S355J2H seamless steel pipe is 355 MPa. Yield strength is the stress at which a material begins to undergo significant plastic deformation. This indicator indicates that the steel pipe can maintain relative structural stability under certain pressure and will not easily undergo irreversible plastic deformation, making it suitable for structures bearing large static loads.
- Tensile Strength: The tensile strength typically ranges from 470 to 630 MPa. Tensile strength reflects the material’s ability to resist tensile failure. This means that the steel pipe can withstand a certain degree of axial tension without breaking, ensuring its reliability under tensile loads.
- Elongation: The minimum elongation is 22%. Elongation reflects the steel’s plastic deformation capacity. A high elongation indicates that the steel pipe can undergo a certain degree of plastic deformation without brittle fracture during stress-induced deformation, demonstrating good toughness when handling dynamic loads or structural deformation.
3. Impact Performance: This seamless steel pipe can withstand impact tests at temperatures down to -20°C. Even at this low temperature, it maintains excellent impact performance, meaning it can absorb sufficient energy without breaking. This makes S355J2H seamless steel pipe a significant advantage in structural applications in cold environments, such as building structures and outdoor machinery in northern China.
4. Quality Grade and Application: The “J2″ in the grade designation indicates the impact performance grade, while the “H” generally indicates that the steel is intended for hollow section production. S355J2H seamless steel pipe is a high-strength structural steel primarily used in construction, bridges, machinery manufacturing, petrochemicals, and other fields. In architectural structures, it can be used to create frameworks and support structures for high-rise buildings. In bridge construction, it is suitable for manufacturing key components such as piers and main beams. In machinery manufacturing, it can be used to manufacture parts that withstand heavy loads. In the petrochemical industry, it can be used in pipeline systems for transporting media such as oil and natural gas.
Second, Performance Characteristics of S355J2H Seamless Steel Pipe
1. Excellent Mechanical Properties
- Yield Strength: S275J2H steel grade has a high yield strength. For example, within the specified thickness range, its minimum yield strength reaches approximately 275 MPa. This allows the seamless steel pipe to resist deformation to a certain extent under pressure, making it suitable for structures bearing heavy static loads, such as support components in building frames.
- Tensile Strength: Its tensile strength generally ranges from 410 to 560 MPa. This tensile strength ensures that the steel pipe will not easily break under tensile forces, allowing it to withstand a certain degree of tension, such as in pipeline systems that require axial tension.
- Elongation: The minimum elongation is approximately 23%. This means that when subjected to external tension, the steel pipe exhibits a certain degree of plastic deformation, adapting to deformation without brittle fracture. This is crucial for applications that may encounter dynamic loads or require a certain degree of toughness.
2. Excellent Impact Toughness
S275J2H seamless steel pipe exhibits excellent impact toughness, especially at relatively low temperatures. Its impact test temperature can reach -20°C, maintaining excellent impact performance at this temperature and absorbing significant energy without fracture. This makes it advantageous for structural applications in cold regions or in low-temperature environments subject to impact loads, such as cryogenic liquid pipelines.
3. Stable and Reasonable Chemical Composition
- Carbon Content Control: The carbon content generally does not exceed 0.20%. An appropriate carbon content helps improve the steel’s strength while preventing the brittleness caused by excessive carbon content. This low carbon content ensures excellent weldability, making it easier to weld in applications such as pipeline connections.
- Alloying Combination: In addition to carbon, it also contains alloying elements such as silicon and manganese. The silicon content does not exceed 0.55%, and the manganese content does not exceed 1.50%. The presence of these elements helps improve the steel’s overall properties, including strength and toughness, while also refining the grain size and improving the steel’s microstructure.
4. Better Corrosion Resistance: Compared to ordinary carbon steel pipe, S275J2H seamless steel pipe exhibits a certain degree of corrosion resistance due to its chemical composition and production process. In mildly corrosive environments, such as piping systems within industrial plants with small amounts of moisture or mildly corrosive gases, it can resist corrosion and extend its service life.
5. Excellent Dimensional Accuracy and Appearance
S275J2H seamless steel pipe, produced according to standards, exhibits excellent dimensional accuracy. Dimensional tolerances for outer diameter and wall thickness are controlled within a certain range. For example, the outer diameter tolerance is generally between ±0.5% and ±1%, and the wall thickness tolerance is typically between ±10% and ±15%. This allows it to better match other pipe fittings during piping system installation, ensuring system sealing and stability. At the same time, there are strict requirements for the straightness and roundness of steel pipes. The straightness generally does not exceed 3mm per meter, and the roundness requires that the difference between the maximum outer diameter and the minimum outer diameter on the cross section of the steel pipe does not exceed 80% of the outer diameter tolerance. This can ensure the stability of the steel pipe during installation and use, and the smoothness of fluid transportation.
Post time: Sep-01-2025