Cr12MoV Steel Technical Overview

Cr12MoV Steel Technical Overview: Cr12MoV is a high-carbon, high-chromium tool steel, specifically a ledeburitic type. At Aobo Steel, we know this grade well.

1. Cr12MoV tool Steel Chemical Composition

• Carbon (C): 1.45 % – 1.70%
• Silicon (Si): ≤0.40%
• Manganese (Mn): ≤0.40%
• Chromium (Cr): 11.00%- 12.50%
• Vanadium (V): 0.15% – 0.30%
• Molybdenum (Mo): 0.40% – 0.60%
• Sulfur (S): ≤0.030%
• Phosphorus (P): ≤0.030%

2. Key Properties and Advantages

This steel offers excellent hardenability, meaning it can be through-hardened effectively even in large sections up to 300-400mm. Compared to standard Cr12 steel, Cr12MoV delivers superior hardness, strength, and toughness after proper quenching and tempering. It also provides good wear resistance and retains useful hardness up to 300-400°C. A significant benefit is its minimal deformation during heat treatment, which is crucial for precision components. These combined properties make it a go-to material for high-quality cold work dies.

3. Cr12MoV tool Steel Applications

Due to its robust properties, Cr12MoV is widely used for demanding tooling applications, especially those involving large cross-sections, complex shapes, or high impact:

• Complex punching and blanking dies (including for silicon steel sheets)
• Trimming and flanging dies
• Wire drawing dies
• Cold extrusion dies
• Steel plate deep drawing dies
• Thread rolling plates
• Cold cutting shears and circular saws
• Standard tools and gauges
• It’s also a viable option for certain plastic molds, potentially speeding up production and saving costs. For rolling die cold stamping blanks, a hardness under 229HBW is generally specified.

4. Processing Considerations – Carbides and Forging:

As a ledeburitic steel, Cr12MoV naturally contains eutectic carbides in its as-cast state. Proper hot working, like forging, is essential to break down these carbides. Even after mill processing, some carbide segregation can remain, leading to inconsistent mechanical properties (anisotropy) and potentially causing deformation or cracking during heat treatment.

At Aobo Steel, with our extensive forging experience, we understand the importance of refining this structure. For complex dies or larger blanks, applying processes like repeated upsetting and drawing, or axial/radial cross upsetting-drawing, is highly recommended. This helps distribute the carbides more evenly, improving the steel’s overall performance and reducing issues later.

5. Cr12MoV Tool Steel Heat Treatment

The standard heat treatment involves quenching and tempering. The goal is to achieve a tempered martensite structure with fine, dispersed carbides, which gives the best combination of wear resistance and toughness.

However, uneven carbide distribution (banded, networked, or lumpy structures) can cause problems like anisotropic deformation – for example, a round hole might become elliptical after quenching. This happens partly because the carbides and the steel matrix expand and contract at different rates during heating and cooling.

Techniques exist to manage this, such as double-cross forging followed by quenching using residual heat and high-temperature tempering (e.g., 750°C). For large dies unsuitable for forging, a solid solution double refinement treatment can help homogenize the carbides. Controlled annealing is also key to achieving a spheroidized structure, which offers the best cold workability.

6. Potential Issues and Solutions:

• Grinding Cracks: Cr12MoV has relatively low thermal conductivity. This can lead to heat build-up during grinding, increasing stress and the risk of cracks, especially if coarse or networked carbides are present. Overheating during quenching or insufficient tempering can make the steel more brittle and susceptible to grinding cracks.
• Dimensional Changes: If quenching causes excessive shrinkage, cryogenic treatment (cooling to -20 °C, -30 °C, or even -70 °C) can induce expansion to correct it. Chemical etching can also adjust dimensions on internal bores or external profiles.

Cr12MoV is an excellent and versatile cold-work tool steel. However, achieving its full potential and ensuring long service life depend critically on proper processing—particularly forging to refine the carbide structure and careful control over heat treatment parameters. Selecting the right process is key to getting a uniform microstructure that meets the specific demands of the application.