4Cr5MoSiV (H11) hot work mold steel is an alloy tool steel with outstanding comprehensive properties, and its features can be summarized as follows:
1. Excellent Thermal Strength and Thermal Fatigue Resistance
High-Temperature Stability: 4Cr5MoSiV steel maintains relatively high strength and hardness at elevated temperatures (400°C–500°C). Its tensile strength, yield strength, and hardness exhibit minimal decline with increasing temperature, making it suitable for manufacturing molds subjected to high-temperature cyclic loading.
Thermal Fatigue Resistance: The addition of chromium (Cr), molybdenum (Mo), and silicon (Si) forms stable carbides that effectively suppress softening and thermal crack propagation at high temperatures, significantly enhancing the mold's thermal fatigue resistance and extending its service life.
2. Good Toughness and Impact Resistance
High Toughness: With a moderate carbon content (0.33%–0.43%) and the inclusion of silicon (0.80%–1.20%) and manganese (0.20%–0.50%), 4Cr5MoSiV steel achieves a uniform tempered martensite structure through proper heat treatment (e.g., quenching + tempering), providing excellent toughness.
Impact Resistance: The steel is resistant to brittle fracture under impact loading, making it ideal for molds requiring high impact resistance, such as hammer forging dies and die-casting dies.
3. Superior Wear Resistance and Corrosion Resistance
Wear Resistance: The addition of molybdenum (1.10%–1.60%) and vanadium (0.30%–0.60%) forms hard carbides (e.g., MoC, VC), significantly improving the steel's wear resistance and reducing mold wear under high-pressure, high-speed friction conditions.
Corrosion Resistance: By controlling sulfur (S) and phosphorus (P) contents (both ≤0.030%), the steel's impurity levels are reduced, minimizing corrosion susceptibility. Additionally, chromium forms a dense oxide layer on the surface, further enhancing corrosion resistance.
4. Excellent Heat Treatment Processability
Hardenability: 4Cr5MoSiV steel exhibits high hardenability, allowing uniform martensite formation through oil or air cooling even in large cross-sections, reducing the risk of quenching distortion and cracking.
Tempering Stability: During tempering, hardness decreases slowly, enabling tempering at higher temperatures to eliminate internal stresses and improve toughness while maintaining relatively high hardness (typically 48–52 HRC after tempering).
Dimensional Stability: Minimal dimensional changes occur during heat treatment, making it suitable for manufacturing high-precision molds and reducing the need for subsequent machining and adjustments.
