Description
18CrNi8 Alloy Steel: Comprehensive Overview
18CrNi8 is a low-alloy steel known for its good combination of toughness, strength, and ductility. This steel grade is primarily used in applications requiring high strength and impact resistance, making it suitable for a variety of engineering and structural applications.
18CrNi8 Grade Introduction
18CrNi8 is a low-alloy steel with added chromium and nickel, which enhances its mechanical properties and impact toughness. The steel is known for its good weldability and machinability, as well as its capacity to achieve high strength after heat treatment. Its composition makes it particularly valuable in applications where both toughness and strength are essential.
Chemical Composition
The chemical composition of 18CrNi8 is carefully controlled to provide a balance of strength, toughness, and machinability:
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.18 – 0.22 |
| Manganese (Mn) | 0.60 – 0.90 |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.035 |
| Chromium (Cr) | 1.40 – 1.60 |
| Nickel (Ni) | 1.20 – 1.50 |
| Silicon (Si) | 0.15 – 0.35 |
Mechanical Properties
18CrNi8 provides excellent mechanical properties, suitable for high-stress applications:
| Property | Value |
|---|---|
| Tensile Strength (MPa) | ≥ 800 |
| Yield Strength (MPa) | ≥ 650 |
| Elongation Rate (%) | ≥ 12 |
| Impact Toughness (J/cm²) | ≥ 50 |
| Hardness (HB) | 180 – 220 HB |
Hardness
The typical hardness range for 18CrNi8 is between 180 and 220 HB. This range provides a good balance between hardness and toughness, making it suitable for demanding applications.
Heat Treatment
To achieve the desired properties, 18CrNi8 undergoes several heat treatment processes:
- Hardening:
- Heating: Heat to 850-880°C.
- Quenching: Typically performed in oil or water to achieve high hardness.
- Tempering: Performed at 500-600°C to relieve internal stresses and improve toughness.
Physical Properties
18CrNi8 has the following physical properties:
| Property | Value |
|---|---|
| Modulus of Elasticity (N/mm²) | 210 × 10³ |
| Density (g/cm³) | 7.85 |
| Thermal Conductivity (W/m.K) | 20.0 |
Thermal Properties
- Thermal Conductivity: 20.0 W/m.K
Forging Properties
18CrNi8 can be hot-formed within the temperature range of 1100°C to 850°C.
Stress Relieving
After cold working, stress relief heat treatment is conducted to reduce internal stresses and improve dimensional stability.
Normalizing
Normalizing is carried out at 850-880°C, followed by air cooling to refine the microstructure and enhance mechanical properties.
Annealing
Annealing is performed at 850-880°C, followed by slow furnace cooling to relieve stress and improve machinability.
Welding
18CrNi8 has good weldability, although preheating and post-weld heat treatment are recommended to prevent potential issues such as cracking due to its alloy content.
Equivalent Grades
18CrNi8 is comparable to several other steel grades with similar properties:
| Standard | Equivalent Grade |
|---|---|
| GB | 18CrNi8 |
| JIS | SNCM420 |
| ASTM | 4320 |
| DIN | 1.6523 |
Applications
18CrNi8 is used in various applications due to its strength and toughness:
- Automotive: Components such as gears, shafts, and other parts subjected to high mechanical loads.
- Industrial Machinery: High-strength components that require good impact resistance and toughness.
- Structural Components: Used in construction and engineering applications where high strength is essential.
- Forgings: High-performance forgings requiring excellent mechanical properties.
Supply Cities:
Mumbai Ahmedabad, Amaravathi, Ambattur, Bangalore, Belgaum, Chennai, Chittoor, Coimbatore, Dindigul, Mysore, Nellore, Hyderabad, Kochi, Mangalore, Tirupur, Tuticorin, Madurai, Andhra Pradesh, Karnataka, Puducherry, Kerala, Tamil Nadu, Telangana, Visakhapatnam, Kochi, Kerala, Hubli-Dharwad, Karnataka, Ghaziabad Kolkata.
