1.4872, X25CrMnNiN25-9-7

Yield Strength: ~400–450 MPa

Ultimate Tensile Strength (UTS): ~700–800 MPa

Elongation at Break: ~40%

Hardness: Approximately 200–250 HB

X25CrMnNiN25-9-7 is a high-nitrogen austenitic stainless steel, and its physical properties reflect its robust composition, making it suitable for demanding applications. Below are the key physical characteristics:

Density: Value: ~7.8 g/cm³ (7800 kg/m³)
This density is typical of austenitic stainless steels, ensuring good strength-to-weight ratio for structural applications.

Thermal Conductivity: Value: ~15–20 W/m·K (at room temperature, ~20°C or 68°F)
Moderate thermal conductivity compared to other stainless steels, due to its austenitic microstructure and nitrogen content.
Suitable for environments where heat transfer is not the primary concern.

Specific Heat Capacity: Value: ~500 J/kg·K (at room temperature)

Thermal Expansion: Coefficient: ~16–17 × 10⁻⁶ /K (in the range of 20–300°C or 68–572°F)

Electrical Resistivity: Value: ~0.8–0.9 μΩ·m (at room temperature)

Modulus of Elasticity: Value: ~200 GPa (29 × 10⁶ psi)

Melting Range: Range: ~1375–1450°C (2507–2642°F)

X25CrMnNiN25-9-7 is a high-nitrogen austenitic stainless steel known for its excellent strength, toughness, and corrosion resistance. The heat treatment of this grade aims to optimize its mechanical properties and corrosion resistance. Below are the typical heat treatment steps:

Solution Annealing

• Temperature Range: 1050–1100°C (1922–2012°F)
• Soaking Time: Based on the thickness of the material, generally 1–2 minutes per mm, with a minimum of 30 minutes.
• Cooling Method: Rapid water quenching or air cooling to avoid carbide precipitation.

Note: Rapid cooling is crucial to prevent sensitization (chromium carbide precipitation leading to intergranular corrosion).

Stress Relieving

Stress relieving helps to reduce residual stresses from machining or cold working without significantly altering the material’s microstructure.

• Temperature Range: 300–400°C (572–752°F)
• Soaking Time: 1–2 hours.
• Cooling Method: Slow air cooling.

Note: While stress relieving does not eliminate all residual stress, it reduces the risk of stress-corrosion cracking.

Post-Weld Heat Treatment (PWHT)

Post-weld heat treatment is essential for restoring the material’s properties after welding, especially for components used in high-stress environments.

• Temperature Range: 1050–1100°C (1922–2012°F) for full solution annealing.
• Soaking Time: Adjust based on the thickness of the weld and the component.
• Cooling Method: Rapid water quenching or air cooling.

Note: PWHT ensures the weld heat-affected zone (HAZ) regains its uniform mechanical and corrosion-resistant properties.