SA-179 seamless steel tubes, also known as heat exchanger tubes under the ASME SA-179M standard, are seamless steel tube products based on ASME (American Society of Mechanical Engineers) standards.
SA-178A is a type of seamless carbon steel tube under the ASME standard, specifically for resistance-welded carbon steel and carbon-manganese steel boiler and superheater tubes.
Chemical Composition Comparison Table (Unit: Mass Percentage, %)
| Element | SA178 (ASTM A178) | SA179 (ASTM A179) | Notes |
|---|---|---|---|
| Carbon (C) | ≤0.18 (Grade A) ≤0.23 (Grade C) ≤0.30 (Grade D) |
≤0.06 | SA178, as a resistance-welded tube, has a broader carbon range; SA179, as a cold-drawn seamless tube, strictly limits carbon to enhance weldability and toughness |
| Manganese (Mn) | ≤0.90 (Grade A) ≤1.00 (Grade C) ≤1.20 (Grade D) |
0.27–0.63 | SA179 maintains tighter manganese control to ensure uniform microstructure after cold drawing |
| Silicon (Si) | ≤0.30 | ≤0.25 | Both limit silicon to minimize adverse effects on weldability |
| Phosphorus (P) | ≤0.035 | ≤0.035 | Strictly controlled to prevent cold brittleness |
| Sulfur (S) | ≤0.035 | ≤0.035 | Both require low sulfur content to maintain ductility |
Mechanical Properties Comparison Table (Minimum Values per ASTM Standard)
| Property | SA178 (ASTM A178) | SA179 (ASTM A179) | Test Method |
|---|---|---|---|
| Tensile Strength | Grade A: ≥310 MPa Grade C: ≥380 MPa Grade D: ≥450 MPa |
≥325 MPa | ASTM E8/E8M |
| Yield Strength | Grade A: ≥195 MPa Grade C: ≥240 MPa Grade D: ≥310 MPa |
≥180 MPa | ASTM E8/E8M |
| Elongation in 50mm | Grade A: ≥25% Grade C: ≥20% Grade D: ≥18% |
≥35% | ASTM E8/E8M |
| Hardness (Rockwell B) | Not specified | ≤72 HRB | ASTM E18 |
Mechanical Performance Comparison Table
| Property | SA178 (ASTM A178) | SA179 (ASTM A179) | Notes |
|---|---|---|---|
| Elastic Modulus | ~200 GPa (typical for carbon steel) | ~200 GPa (typical for carbon steel) | No significant difference; both are low-carbon steels |
| Impact Toughness (Charpy V-Notch) | Not specified in standard | Not specified in standard | Neither standard mandates impact energy requirements; additional testing is required for severe service conditions |
| Fatigue Strength | Not specified in standard | Not specified in standard | Neither standard provides fatigue limits. In engineering design, 40% of tensile strength is commonly used as an estimate (~130 MPa) |
| Heat Treatment Requirement | Post-weld stress relief annealing | Bright annealing (≥650°C) | SA179 requires bright annealing to relieve cold-work stresses and improve corrosion resistance and dimensional stability |