ASTM A312 TP310S Stainless Steel Pipe Tube Heat Resistant SS Pipe Alloy 1.4845 SCH40S
ASTM A312 TP310S stainless steel pipe (also designated as Alloy 1.4845 and commonly supplied in SCH40S wall thickness) is a premium heat-resistant austenitic stainless steel product engineered for high-temperature and corrosive industrial environments. Its unique chemical composition and mechanical properties make it a preferred choice for applications requiring long-term stability under extreme thermal stress. Below is a comprehensive overview of its parameters, standards, specifications, features, equivalent grades, and typical applications.
1. Core Chemical Composition (Weight %)
The chemical makeup of TP310S is strictly regulated to ensure heat resistance and corrosion performance, as defined by ASTM standards:
| Element | Minimum (%) | Maximum (%) | Key Function |
| Carbon (C) | - | 0.08 | Reduces carbide precipitation at high temperatures, preventing intergranular corrosion |
| Chromium (Cr) | 24.0 | 26.0 | Forms a dense oxide layer (Cr₂O₃) for oxidation resistance at temperatures up to 1150°C (2102°F) |
| Nickel (Ni) | 19.0 | 22.0 | Stabilizes the austenitic structure, enhancing ductility and resistance to thermal fatigue |
| Manganese (Mn) | - | 2.0 | Improves workability without compromising heat resistance |
| Silicon (Si) | - | 1.5 | Aids in oxide layer formation and enhances high-temperature strength |
| Phosphorus (P) | - | 0.045 | Controlled to minimize brittleness and maintain weldability |
| Sulfur (S) | - | 0.030 | Reduced to prevent hot cracking during fabrication |
| Iron (Fe) | Balance | - | Base metal providing structural integrity |
2. Compliance Standard: ASTM A312
This pipe strictly adheres to ASTM A312, a widely recognized American standard for seamless and welded austenitic stainless steel pipes intended for high-pressure and high-temperature service. Key requirements of ASTM A312 include:
- Uniform chemical composition across the pipe length.
- Rigorous mechanical property testing (tensile, elongation).
- Non-destructive testing (NDT) options: Hydrostatic testing (mandatory) to verify leak tightness; optional ultrasonic testing (UT) or eddy current testing (ECT) for defect detection.
- Weld quality control (for welded pipes) to ensure no internal/external cracks or porosity.
3. Physical & Mechanical Properties
TP310S exhibits excellent mechanical stability at both ambient and elevated temperatures:
| Property | Specification | Test Condition |
| Density | 8.0 g/cm³ | Ambient temperature |
| Melting Point | 1400–1450°C (2552–2642°F) | - |
| Tensile Strength (Minimum) | 515 MPa (74,700 psi) | Room temperature |
| Yield Strength (0.2% Offset, Minimum) | 205 MPa (29,700 psi) | Room temperature |
| Elongation (Minimum) | 35% | Room temperature (50 mm gauge length) |
| Thermal Conductivity | 14.2 W/(m·K) | At 100°C (212°F) |
| Coefficient of Thermal Expansion | 16.0 × 10⁻⁶/°C | 20–100°C (68–212°F) |
| Maximum Service Temperature | 1150°C (2102°F) | Continuous use (oxidizing environments) |
4. Product Specifications (SCH40S & Dimensions)
The "SCH40S" designation refers to the standard wall thickness for stainless steel pipes, designed to balance pressure resistance and weight efficiency. Common dimensional ranges for ASTM A312 TP310S SCH40S pipes include:
| Parameter | Range | Notes |
| Outer Diameter (OD) | 1/2" – 24" (12.7 mm – 609.6 mm) | Complies with ANSI/ASME B36.19 (stainless steel pipe dimensions) |
| Wall Thickness (SCH40S) | 3.91 mm (for 2" OD) – 11.91 mm (for 10" OD) | Thickness varies with OD; exact values follow B36.19 |
| Length | 6 meters (20 ft) – 12 meters (40 ft) | Standard mill lengths; custom lengths available on request |
| Form | Seamless or Welded (ERW/SAW) | Seamless pipes for high-pressure applications; welded for lower-pressure, large-diameter needs |
| Surface Finish | 2B (cold-rolled, smooth), No. 4 (brushed), or Pickled & Passivated | Pickled finish is common for corrosion resistance; 2B for sanitary or aesthetic applications |
5. Key Features
TP310S stainless steel pipe stands out for its combination of heat resistance, corrosion performance, and workability:
- Exceptional Heat Resistance: Sustains structural integrity in continuous service up to 1150°C (2102°F) and intermittent service up to 1200°C (2192°F), making it far more heat-tolerant than common grades like 304 or 316.
- Superior Corrosion Resistance: Resists oxidation, sulfidation, and carburization in high-temperature environments (e.g., furnace flue gases, steam). Also offers good resistance to mild acids (e.g., dilute sulfuric acid) and saltwater.
- Excellent Ductility & Weldability: Can be easily welded using standard methods (TIG, MIG, SMAW) without losing mechanical properties. Its high elongation rate (≥35%) enables bending, forming, and fabrication into complex shapes.
- Low Carbon Content: The 0.08% max carbon limits carbide precipitation at grain boundaries (a common cause of cracking in high-temperature service), ensuring long-term reliability.
6. Equivalent Grades
TP310S is known by different designations globally, depending on regional standards. Below is a list of key equivalent grades for cross-reference:
| Standard | Grade Designation | Region |
| ASTM/ASME | TP310S | North America |
| EN 10216-5 | 1.4845 | Europe |
| JIS G3463 | SUS310S | Japan |
| GB/T 14976 | 06Cr25Ni20 | China |
| UNS | S31008 | International (Unified Numbering System) |
Note: While these grades are chemically and mechanically similar, minor variations may exist in 微量元素 (trace elements) or testing requirements. Always confirm compatibility with specific application standards.
7. Typical Applications
Due to its heat resistance and corrosion performance, ASTM A312 TP310S SCH40S pipe is widely used in high-temperature industrial sectors:
- Heat Treatment Equipment: Furnace tubes, radiant tubes, and heating elements for industrial furnaces (e.g., annealing, hardening furnaces).
- Power Generation: Boiler tubes, superheater tubes, and steam pipelines in coal-fired, gas-fired, or waste-to-energy power plants.
- Petrochemical & Refining: Pipes for catalytic crackers, reformers, and exhaust systems (resists sulfidation from crude oil processing).
- Metallurgical Industry: Pipes for steel mill exhausts, molten metal transfer lines, and sintering plants.
- Other High-Temperature Uses: Incinerator chimneys, thermal oxidizers, and food processing equipment (where heat and corrosion resistance are critical).
