鑄鋼 (低中高碳鋼、雙向鋼)
Ni-Cr-Mo Alloy Steel is a type of low-alloy high-strength steel enhanced by the addition of Nickel (Ni), Chromium (Cr), and Molybdenum (Mo). This category of steel combines high strength, toughness, hardenability, and wear resistance, making it widely used in mechanical components, high-stress structural parts, and the aerospace industry.
🔧 Main Alloying Elements and Their Roles
|
Element |
Meaning |
Function |
|
Ni (Nickel) |
Enhances toughness and ductility |
Improves low-temperature performance and impact resistance |
|
Cr (Chromium) |
Increases hardness and corrosion resistance |
Boosts oxidation resistance, surface hardness, and hardenability |
|
Mo (Molybdenum) |
Improves high-temperature strength and temper resistance |
Enhances thermal stability and fatigue resistance |
🛠️ Common Ni-Cr-Mo Alloy Steel Grades
|
JIS (Japanese Standard) |
AISI/SAE (US Standard) |
Common Name (CN) |
Features |
|
SNCM220 |
8620 |
Carburizing Steel |
Low carbon, high toughness, suitable for carburizing |
|
SNCM240 |
8640 |
Structural Steel |
Medium carbon, good strength-toughness balance |
|
SNCM439 |
4340 |
High-strength Steel |
High strength and toughness for heavy-duty parts |
🧪 Heat Treatment Characteristics
- Carburizing: Commonly used for low-carbon grades like SNCM220 to improve surface hardness.
- Quenching + Tempering: Applied to SNCM240 and SNCM439 for optimal strength-toughness balance.
- Normalizing / Annealing: Improves microstructure and workability.
📦 Applications
|
Industry |
Typical Uses |
|
Mechanical Engineering |
Gears, shafts, piston pins, connecting rods, bushings |
|
Automotive |
Drive shafts, crankshafts, camshafts, differential gears |
|
Aerospace |
Landing gear, high-strength bolts, connectors |
|
Military & Heavy Industry |
High-stress structures, hydraulic parts |
|
Grade |
Strength |
Toughness |
Workability |
Heat Treatment |
Main Applications |
|
SNCM220 |
★★ |
★★★ |
★★★ |
Carburizing |
Medium/low-load gears, shafts |
|
SNCM240 |
★★★ |
★★☆ |
★★☆ |
Tempering |
Medium/high-load gears, connecting rods |
|
SNCM439 |
★★★★ |
★★★ |
★★ |
Tempering |
Heavy-load structural parts, aerospace components |
🧩 Did You Know?
- The mechanical properties of Ni-Cr-Mo steels are highly dependent on heat treatment methods. The same grade can show large differences in strength and toughness depending on whether it’s carburized, normalized, or tempered.
- For improved corrosion resistance in high-temperature or corrosive environments, consider stainless types of Ni-Cr-Mo alloys such as Inconel 625 and Hastelloy C (classified as superalloys).