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Chemical composition and mechanical properties of Cr12MoV
Cr12MoV is a high-performance alloy tool steel known for its excellent hardenability, wear resistance, and toughness. It can be fully hardened across cross-sections up to 300–400 mm, maintaining good hardness and strength even at elevated temperatures of 300–400°C. Compared to other similar steels like Cr12, Cr12MoV exhibits higher impact toughness and minimal volume change during quenching, making it ideal for applications requiring precision and durability.
This steel is widely used in the manufacturing of large, complex molds and tools that are subjected to heavy loads. Common applications include punching dies with intricate shapes, inserts in complex molds, deep drawing dies for steel plates, wire drawing dies, thread rolling dies, cold extrusion tools, and cutting tools such as circular saws and standard cutters. Its versatility makes it a preferred choice in industries where performance and longevity are critical.
Cr12MoV conforms to the Chinese national standard GB/T 1299-1985 and is produced by various manufacturers, including Shanggang Plant No. 5. As a cold work die steel, it offers superior hardenability, quenching and tempering hardness, wear resistance, and mechanical strength compared to Cr12. This makes it suitable for manufacturing molds and tools that operate under harsh conditions, such as trimming dies, piping dies, and measuring instruments.
Chemical composition of Cr12MoV includes:
- Carbon (C): 1.45–1.70%
- Silicon (Si): ≤ 0.40%
- Manganese (Mn): ≤ 0.40%
- Sulfur (S): ≤ 0.030%
- Phosphorus (P): ≤ 0.030%
- Chromium (Cr): 11.00–12.50%
- Nickel (Ni): ≤ 0.25% (residual)
- Copper (Cu): ≤ 0.30% (residual)
- Vanadium (V): 0.15–0.30%
- Molybdenum (Mo): 0.40–0.60%
Mechanical properties include:
- Annealed hardness: 255–207 HB (indentation diameter 3.8–4.2 mm)
- Quenched hardness: ≥ 58 HRC
After quenching and tempering, Cr12MoV exhibits higher hardness, strength, and toughness than Cr12. It can be fully hardened for parts with diameters below 300–400 mm, with minimal distortion during quenching. However, its high-temperature plasticity is relatively low.
Heat treatment specifications typically involve:
1. Quenching at 950–1000°C followed by oil cooling.
2. Tempering at 1020°C, followed by 2 hours of tempering at 200°C.
The microstructure consists of fine pearlite and carbides, and the steel is delivered in an annealed condition. Cryogenic treatment is often applied to further enhance the material’s properties. This process promotes the precipitation of ultrafine carbides within the martensite, improving wear resistance and dimensional stability. After low-temperature tempering at 200°C, the structure becomes more stable, offering better performance in demanding environments.
Low-temperature chemical heat treatments such as ion nitriding, gas nitrocarburizing, and salt bath thiocyanate are commonly used to improve surface properties while maintaining the high hardness and wear resistance of Cr12MoV. These treatments significantly increase the adhesion resistance and impact resistance of the steel, especially when using salt bath thiocyanate.
For example, stainless steel vessels manufactured with Cr12MoV and treated with gas nitrocarburizing have shown a service life exceeding 30,000 cycles, which is over ten times longer than those treated with conventional quenching and tempering methods.
In summary, Cr12MoV is a highly versatile and durable tool steel that plays a crucial role in the production of high-quality molds and cutting tools. Its unique combination of properties makes it a popular choice in industrial applications where reliability and performance are essential.
Editor: Hardware Business Network Information Center
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