Introduction to Cr12Mo1V1 Tool Steel

Cr12Mo1V1, commonly referred to as D2 tool steel (AISI standard), 1.2379 (German DIN standard), or SKD11 (Japanese JIS standard), is a high-carbon, high-chromium cold-work mold steel widely used in industrial applications. Known for its high hardness, wear resistance, machinability, and dimensional stability, it is ideal for cold-work molds, hot-work molds, cutting tools, and precision components.

Key Properties

  1. High Hardness: After proper heat treatment and tempering, Cr12Mo1V1 achieves a hardness of 60–62 HRC, ensuring excellent wear resistance and cutting performance.
  2. Superior Wear Resistance: Its high hardness and optimized composition make it suitable for long-term or high-speed machining applications.
  3. Strength and Rigidity: The steel maintains shape stability under stress, resisting deformation or cracking, making it ideal for molds with strict dimensional requirements.
  4. Machinability: High carbon and chromium content enhance its machinability, allowing efficient cutting, milling, and drilling operations.
  5. Thermal Stability: Exhibits strong resistance to thermal fatigue and retains stability in high-temperature environments, suitable for hot-work molds and tools.

Cr12Mo1V1 | D2 tool steel Chemical Composition (%)

ASTM A681 C Mn P S Si Cr V Mo
D2 1.4 1.6 0.1 0.6 0.03 0.03 0.1 0.6 11 13 0.5 1.1 0.7 1.2
JIS G4404 C Mn P S Si Cr V Mo
SKD11 1.4 1.6 0.6 0.03 0.03 0.4 11 13 0.2 0.5 0.8 1.2
DIN ISO 4957 C Mn P S Si Cr V Mo
1.2379/X153CrMo12 1.45 1.6 0.2 0.6 0.03 0.03 0.15 1.6 11 13 0.7 1.0 0.7 1
Cr12Mo1V1 1.40 1.60 0.60Max 0.03 Max 0.03Max 0.60Max 11.0 13.0 0.70 1.0 0.70 1.10

Heat Treatment Processes

1. Annealing

  • Heat to 800–850°C, hold, and slowly cool to room temperature to relieve stress and improve machinability.

2. Solution Treatment

  • Heat to 980–1050°C to transform the microstructure into austenite.

3. Quenching

  • Rapidly cool using air, oil, or salt bath to achieve high hardness (up to 50–52 HRC).

4. Tempering

  • Heat to 150–550°C twice to eliminate internal stresses and enhance toughness and wear resistance.

5. Cryogenic Treatment

  • Cool to -70°C post-quenching to precipitate ultra-fine carbides, further improving hardness and wear resistance.

Advanced Surface Treatments

  1. Salt Bath Vanadizing
    • Forms a dense vanadium carbide (VC) layer on the surface, significantly enhancing hardness, wear resistance, and anti-adhesion properties.
  2. Low-Temperature Thermochemical Treatments
    • Methods like gas nitrocarburizing or sulfur-carbonitriding improve surface adhesion resistance. For example, nitrocarburized molds exhibit 10x longer service life compared to conventional treatments.

Forging and Microstructure Optimization

Cr12Mo1V1 is a ledeburitic steel with ~20% carbides, which often form uneven banded or networked structures. To mitigate carbide segregation:

  • Multi-Directional Forging: Use a “two-light, one-heavy” approach: light strikes initially to prevent cracking, heavy strikes at 980–1020°C to crush carbides, and light strikes again.
  • Solution Refinement: Double-stage preheating (500°C and 800°C), solution treatment at 1100–1150°C, followed by isothermal oil quenching and high-temperature tempering at 750°C.

Applications

  • Stamping Dies: Punching dies, shearing blades.
  • Cutting Tools: Blades, inserts, milling cutters.
  • Plastic Molds: Injection molds, extrusion dies.
  • Hot-Work Molds: Heat-resistant forming dies and hot-press tools.

Physical Properties

  • Elastic Modulus: 219 GPa (approximate).
  • Specific Heat Capacity (Cp): 461 J/(kg·K).
  • Critical Temperatures:
    Ac1 Acm Ar1 Arcm Ms
    790°C 835°C 710°C 765°C 190°C

Softening and Spheroidizing Annealing

  • Cold Extrusion Pre-Treatment: Heat to 760°C under iron chip protection for 10h, furnace-cool to achieve ≤196 HBW.
  • Spheroidizing Annealing: Heat to 860±10°C for 2–4h, cool to 740±10°C for 4–6h, then slow-cool to 500°C. Final hardness ≤241 HBW.

Conclusion

Cr12Mo1V1 tool steel is indispensable for high-performance molds and tools due to its exceptional hardness, wear resistance, and thermal stability. Proper heat treatment, forging, and surface enhancement techniques ensure optimal performance in demanding industrial applications, extending service life and reducing operational costs.