SAE 8620, 21NiCrMo2 Material Number: 1.6523 Special Case Hardening Steels
PRODUCT DESCRIPTION
21NiCrMo2 is a durable steel offering high strength, hardness, and weldability, used in automotive, aerospace, and heavy machinery. It is suitable for high-stress components.PRODUCT TYPES
- Stock is available for Special Case Hardening Steels with diameter between 22 mm and 820 mm.
21NiCrMo2: Overview
21NiCrMo2 is a low-alloy steel that is primarily used in high-strength applications where toughness and hardenability are required. It is an excellent material for producing gears, shafts, and other mechanical components that need to withstand high stress and extreme conditions. This steel is commonly used in the automotive, aerospace, and heavy machinery industries due to its excellent combination of strength, toughness, and machinability.
Chemical Composition (in %)
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.18 – 0.23 |
| Silicon (Si) | 0.20 – 0.35 |
| Manganese (Mn) | 0.50 – 0.80 |
| Phosphorus (P) | 0.025 max |
| Sulfur (S) | 0.025 max |
| Chromium (Cr) | 0.90 – 1.10 |
| Nickel (Ni) | 1.50 – 1.80 |
| Molybdenum (Mo) | 0.20 – 0.30 |
| Copper (Cu) | 0.35 max |
Physical Properties
- Density: 7.85 g/cm³ (or 7850 kg/m³)
- Tensile Strength (Rm): 850–1000 MPa
- Yield Strength (Rp0.2): 700 MPa (min)
- Elongation (A): ≥ 12% (for thickness up to 20 mm)
- Hardness (HB): 190–230
Machinability
21NiCrMo2 steel offers excellent machinability, especially in normalized and tempered conditions. Its alloy content allows for easy cutting and shaping, making it suitable for processes like turning, drilling, milling, and grinding. However, its relatively high hardenability means that care must be taken when machining at higher hardness levels.
Tips for Machining:
- Use carbide tools for improved surface finish and longevity.
- Moderate cutting speeds should be maintained to reduce tool wear and improve productivity.
- Use cutting fluids to prevent excessive heat buildup and reduce friction during machining.
Weldability
21NiCrMo2 steel has good weldability, but like many alloy steels, preheating is recommended for thicker sections. It can be welded by common methods such as MIG, TIG, and arc welding. Post-weld heat treatment (PWHT) may be required to maintain the material's mechanical properties and relieve stresses.
Welding Guidelines:
- Preheating is recommended for sections thicker than 30 mm.
- Use low-hydrogen electrodes to avoid cracking and ensure high-quality welds.
- Post-weld heat treatment is necessary for thicker sections to avoid distortion and to restore the steel's toughness.
Usage Areas
21NiCrMo2 is used in applications where high strength and durability are required, such as:
- Automotive Industry: Gears, shafts, crankshafts, and other components in high-performance vehicles.
- Aerospace Industry: Aircraft components such as turbine shafts and structural parts.
- Heavy Machinery: High-load parts like gears and shafts for heavy equipment.
- Tool Manufacturing: Tools subjected to high wear and tear.
- Energy Sector: Components for turbines, compressors, and other machinery exposed to high stresses.
Industries Using 21NiCrMo2 Steel
- Automotive Industry: Gearbox components, engine parts, and high-performance shafts.
- Aerospace: High-strength structural components and turbine shafts.
- Heavy Equipment: Gears, shafts, and other high-stress components.
- Energy Sector: Components for turbines and other energy-producing machinery.
- Tool Manufacturing: Tools exposed to high mechanical stresses and wear.
Key Advantages of 21NiCrMo2
- High Strength: Ideal for heavy-duty and load-bearing applications.
- Good Hardenability: Can be hardened for wear-resistant components.
- Good Weldability: Easily welded with standard techniques, though preheating is recommended.
- Durability and Toughness: Suitable for use in extreme conditions and high-stress environments.
- Versatility: Used across various industries, including automotive, aerospace, and heavy machinery.