Introduction
When rough machining 16MnCrS5 after heat treatment, understanding the material’s core properties is essential. Post quench-and-temper or carburizing, the hardness typically ranges between HB220–280 (HRC20–25), placing it in the medium-to-low hardness category.
With roughing operations involving the removal of 3–5 mm of material, tools must offer excellent impact resistance, cost efficiency, and cutting stability. This article compares CBN and cemented carbide tools to help you select the best option for machining 16MnCrS5.
1. Differences Between CBN and Cemented Carbide Tools
1.1 Material Hardness Compatibility
CBN (cubic boron nitride) tools perform best on materials with hardness above HRC45, such as hardened or high-speed steels. However, in the HRC20–25 range typical of heat-treated 16MnCrS5, CBN cutting edges are prone to material adhesion due to higher workpiece plasticity. This increases cutting resistance and can lead to premature wear.
By contrast, ultrafine-grained cemented carbide (e.g., WC-Co-TiC) offers a hardness of HV1600–1800, which matches well with 16MnCrS5. This ensures consistent material removal and minimizes abnormal tool wear.
1.2 Impact Resistance
Rough machining often involves fluctuating material allowances (±0.5 mm), requiring tools with high impact resistance. CBN tools, with a bending strength of only 1200–1500 MPa, are relatively brittle and susceptible to chipping under variable loads.
Ultrafine-grained cemented carbide offers a bending strength of ≥2300 MPa. Combined with a reinforced cutting edge (R0.2–R0.3 mm radius), it delivers superior resistance to impact, ensuring reliable performance during continuous roughing operations.
1.3 Cost and Versatility
CBN tools are significantly more expensive—typically 5–8 times the cost of comparable cemented carbide tools. They also often require specialized toolholders.
Cemented carbide tools are not only more affordable but also compatible with standard CNC lathes and milling machines, making them ideal for high-volume production. In most cases, roughing with cemented carbide accounts for less than 30% of total machining costs.
2. Recommended Tool for Rough Machining 16MnCrS5
Based on the above analysis, ultrafine-grained cemented carbide tools are the optimal choice for rough machining 16MnCrS5 after heat treatment.
Tool Selection Guidelines:
- Material: WC-Co-TiC alloy with 8–10% cobalt content. The TiC additive improves anti-adhesion properties and reduces abrasive wear caused by chromium in 16MnCrS5.
- Geometry:
- Lead angle: 90°–100° (reduces radial cutting force)
- Rake angle: 8°–12° (lowers cutting resistance)
- Edge preparation: R0.2–R0.3 mm hone (boosts impact resistance)
- Cutting Parameters:
- Cutting speed: 80–100 m/min
- Feed rate: 0.2–0.3 mm/rev
- Depth of cut: 3–5 mm
- High-pressure internal coolant: 6–8 MPa
Using these parameters, tool life can reach 240–280 minutes, 2 to 3 times longer than CBN under the same conditions.
3. Special Machining Scenarios
If localized heat treatment (e.g., spot hardening) raises hardness above HRC35 in certain areas, a hybrid tooling approach is recommended:
- Use cemented carbide for the majority of the workpiece (medium-low hardness zones).
- Apply CBN tools only for localized high-hardness areas (covering less than 10% of the total surface), using reduced parameters:
- Depth of cut: 0.5–1 mm
- Feed rate: 0.1–0.15 mm/rev
Prior hardness testing and marking of high-hardness zones are essential to prevent unnecessary tool wear and cost.
Conclusion
For rough machining 16MnCrS5 in the HRC20–25 hardness range, ultrafine-grained cemented carbide tools provide the best balance of performance, durability, and cost-effectiveness. Their superior impact resistance and material compatibility make them the logical choice for high-productivity machining. Reserve CBN tools only for localized high-hardness areas to optimize tooling strategy and control costs.
