ASTM A181 Class 70
ASTM A181 Class 70 Carbon Steel Forgings
ASTM A181 Class 70 is a carbon steel forging grade designed for high-strength, high-temperature, and pressure service applications. It is commonly used in the manufacture of flanges, fittings, valves, and pressure components in industries such as oil & gas, power generation, petrochemical, and process engineering.
ASTM A181 Cl 70 provides excellent tensile strength, toughness, and ductility, along with good weldability and machinability. Its balanced chemical composition allows it to perform reliably under moderate to elevated temperature conditions while maintaining structural integrity and dimensional accuracy.
Key Features
High tensile and yield strength for demanding pressure service
Excellent forgeability and machinability
Superior weldability with all standard welding methods
Reliable performance at moderate to high temperatures
Good ductility and impact strength
Suitable for flanges, fittings, and pressure-retaining components
ASTM A181 Class 70 Specification
| Standard | Specification |
|---|---|
| Product Form | Forged flanges, fittings, valves, and pressure parts |
| Material Type | Carbon Steel |
| Grade | ASTM A181 Class 70 |
| Manufacturing Process | Open die or closed die forging |
| Heat Treatment | Normalized or annealed as required |
| Service Temperature | Ambient to moderately high temperature service |
Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| ASTM / ASME | A181 Cl 70 / SA181 Cl 70 |
| EN | C50E (1.1206) |
| DIN | C50 |
| BS | 1501-161-440B |
Available Sizes
| Form | Size Range |
|---|---|
| Forged Flanges | ½” to 24” NB |
| Forged Fittings | ½” to 4” NB |
| Custom Forged Components | As per client specifications |
Chemical Composition
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.38 – 0.48 |
| Manganese (Mn) | 0.60 – 1.00 |
| Phosphorus (P) | 0.035 max |
| Sulphur (S) | 0.040 max |
| Silicon (Si) | 0.10 – 0.35 |
Mechanical Properties
| Property | Unit | Value |
|---|---|---|
| Tensile Strength | MPa | 485 – 655 |
| Yield Strength | MPa | 275 min |
| Elongation | % | 18 min |
| Reduction of Area | % | 30 min |
| Hardness | HB | 180 – 207 |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1425 – 1540°C |
| Modulus of Elasticity | 200 GPa |
| Thermal Conductivity | 51 W/m·K |
| Electrical Resistivity | 0.1 µΩ·m |
Type of ASTM A181 Class 70 Flanges
Corrosion Resistance
ASTM A181 Class 70 offers moderate corrosion resistance in standard industrial environments. While it performs well under atmospheric and mild chemical exposure, additional protection like galvanizing, painting, or coating is recommended for corrosive or marine conditions.
Heat Resistance
ASTM A181 Cl 70 exhibits excellent mechanical performance up to 450°C. It retains strength and dimensional stability under moderate thermal stress and cyclic temperature operations. However, it is not recommended for prolonged use at elevated temperatures exceeding its limit.
Heat Treatment
Normalizing: 890°C – 950°C followed by air cooling
Annealing: 850°C – 900°C followed by slow furnace cooling
Proper heat treatment enhances toughness, machinability, and grain refinement, ensuring consistent performance in service.
Welding
This grade can be easily welded using SMAW, GMAW, GTAW, or SAW processes. For thick sections, preheating to around 150–200°C is recommended to prevent cracking. Post-weld stress relief can be performed to enhance joint strength and reduce residual stresses.
Fabrication
ASTM A181 Class 70 is highly machinable and easily forged between 900°C and 1200°C. After forging, the material should undergo suitable heat treatment to restore its mechanical strength. It can be formed, drilled, and machined to precise tolerances, making it ideal for high-performance industrial components.
Applications
Pressure vessels and forged flanges
Industrial valves and pipe fittings
Pumps, shafts, and mechanical assemblies
Power generation and petrochemical industries
Oil & gas transmission systems
General-purpose high-pressure components