ASTM A437 B4B W 1.4938 AISI 422
Material 1.4938 is a martensitic stainless steel with high mechanical properties and corrosion resistance, often used in critical applications such as turbines and aerospace components. The A437 B4B designation refers to the ASTM A437 standard classification, which applies to steels intended for high-temperature and high-pressure applications, such as boiler and turbine bolts.
Chemical Composition
| Element | Minimum (%) | Maximum (%) |
|---|---|---|
| Ni | 3.8 | 4.8 |
| Cr | 11.5 | 13.5 |
| P | 0.020 | |
| Mo | 1.0 | 1.5 |
| C | 0.12 | 0.18 |
| Mn | 1.0 | 1.5 |
| Yes | 0.50 | |
| V | 0.20 | 0.50 |
| S | 0.015 |
Mechanical Characteristics
| Material | Rm min (MPa) | Rp 0.2 min (MPa) | Elongation (%) | Hardness max (HRC) |
|---|---|---|---|---|
| Werkstoff 1.4938 A437 B4B | 850 – 1100 | 650-800 | 12-15 | 25 – 35 |
Physical Properties
- Density: 7.7 to 7.8 g/cm³
- Modulus of elasticity: 210 GPa
- Coefficient of thermal expansion (20-100°C): 11.5 x 10^-6 K^-1
- Thermal conductivity (at 100°C): 23 W/m-K
- Specific heat capacity: 460 J/kg-K
Heat Treatments
- Tempering: The material is tempered in oil or air at a temperature of about 1000°C followed by rapid cooling.
- Tempering: Usually performed at a temperature between 650°C and 750°C to improve toughness and reduce internal stresses.
Corrosion Resistance
1.4938 offers good corrosion resistance in high temperature environments due to the presence of chromium and molybdenum. However, compared to austenitic stainless steels, it has slightly lower corrosion resistance in highly aggressive environments (e.g., with high levels of chlorides).
Correspondence and Specifications
- EN: 10269
- ASTM: A437
