| Chemical Composition | |
| Element | Composition (wt%) |
| Carbon (C) | 0.06 – 0.18 |
| Manganese (Mn) | 0.27 – 0.63 |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.035 |
| Silicon (Si) | ≤ 0.25 |
| Mechanical Properties | |
| Property | Requirement (min.) |
| Tensile Strength | ≥ 325 MPa (47 ksi) |
| Yield Strength (0.5% extension under load) | ≥ 180 MPa (26 ksi) |
| Elongation (in 2 in / 50 mm) | ≥ 35% |
| Hardness (Rockwell B) | ≤ 72 HRB |
Differences between standard U-shaped tubes
| Item | U-Tube | Serpentine Tube Bundle |
| Structure | Symmetric U-bend, fixed to one tube sheet | Continuous multi-bend/coiled, no common tube sheet |
| Application Scenario | Shell-and-tube heat exchangers | Boiler flue gas heating surfaces (economizer/superheater) |
| Key Benefit | Thermal stress relief for shell-and-tube units | Maximized heat transfer area & optimal flue duct fit |
Application:
