A139 Gr.B is a specially designed low-yield carbon-manganese steel for spiral welded pipe. Its core characteristics and application highlights are as follows:
Material Properties and Chemical Composition
Composition Design
The use of a C-Mn-Ca composite strengthening system replaces traditional alloying elements such as Nb, V, and Ti, significantly reducing costs while improving steel purity.
The low carbon content (the carbon content is not specified, but falls within the scope of low-carbon steel) ensures excellent weldability and cold formability.
Core Performance
| index | Required characteristics |
|---|---|
| Yield-to-strength ratio | Low yield strength ratio (≤0.85) to improve deformation resistance |
| Toughness | Balanced high and low temperature toughness and strong impact resistance |
| Cold bending performance | Meet strict cold bending no cracking standards |
| Welding performance | Adapt to spiral welding process, stable weld quality |
Mechanical Performance Advantages
Strength and Plasticity Balance: Tensile strength ≥485 MPa, yield strength ≥290 MPa, and elongation ≥28%, with ample margin to ensure pipeline service safety.
Low Yield Ratio: Reduces the risk of localized buckling, making it particularly suitable for pipelines in areas of frequent geological activity.
Applications
Energy Pipelines: Medium- and low-pressure oil and natural gas pipelines (design pressure typically ≤10 MPa).
Structural Support Components: Bridge and culvert support, construction machinery frames, and other applications requiring high formability.
Use Limitations and Precautions
Corrosion Resistance Limitations: As a carbon-manganese steel, long-term exposure to humid or corrosive environments requires an anti-corrosion coating (such as epoxy resin).
Temperature Limitations: Applicable temperature range: -20°C to 350°C. For applications exceeding this temperature, alloy steel pipe (such as chrome-molybdenum steel) should be used.