Since its inception, High-Speed Steel (HSS) has remained the fundamental material for machining. Even with the rise of carbides, HSS still dominates the market for precision and complex tools like hobs and broaches due to its unique combination of toughness and hardness.
To ensure peak performance, it is critical to establish the relationship between “Chemical Composition – Microstructure – Mechanical Properties.”
| Category | Main Grade | Composition Characteristics and Characteristics | Suitable Tool Varieties | Hardness HRC |
| No Co | W6Mo5Cr4V2Al(M2Al) / W9Mo3Cr4VAl(W9Al) / W6Mo5Cr4V2 S i (M2Si) | The carbon content is high, the balance carbon difference is small, the carbon saturation is high, it is easy to mix crystals, and the quenching range is narrow. | End mills, reamers, turning tools, sheet mills, broaches | 65～67 |
| Have Co | W6Mo5Cr4V2Co8(M36,C8) / W9Co5、M35、M42 | High redness and hardness, strong resistance to tempering and softening, good workability, and good overall performance. | Gear hobs, insert milling cutter teeth, shaving cutters, various broaches | >64 |
| High V | W6Mo5Cr4V3(M3、S607) / W9V3 、W6Mo5Cr4V4(M4) / W12Mo3Cr4V3N(V3N) | High carbon content, good wear resistance, poor grindability. | Taps, reamers, high-strength drills, hobs, gear shaper cutters, wheel groove milling cutters | >65 |
| Have Co and High V | W12Cr4V5Co5(T15) / W12Mo3Cr4V3Co5Si（Co5Si ） | High carbon content, high hardness, good wear resistance and poor toughness. | High-strength turning tools, various gear tools, precision milling cutters | 66～69 |
1. Classification and Tool Selection for High-Performance HSS
High-performance HSS refers to grades where heat-treated hardness, temper-softening resistance, and wear resistance are significantly superior to general-purpose grades (like M2).
- Cobalt-Bearing HSS: Examples include M42 (W2Mo9Cr4V2Co8). The addition of 8% Cobalt significantly boosts red hardness.
- Applications: Machining of aerospace components, high-strength quenched steel, stainless steel, and heat-resistant alloys.
- Hardness: Typically controlled between 66–68 HRC.
- High-Vanadium HSS: Examples include M4 (W6Mo5Cr4V4). A high carbon-to-vanadium ratio forms dense, high-hardness carbides for extreme wear resistance.
- Applications: Taps, reamers, high-strength drills, and gear-shaping cutters.
- Aluminum-Bearing HSS: Examples include M2Al. Using aluminum as a cost-effective alternative to cobalt while maintaining high hardness.
- Applications: End mills, form milling cutters, and broaches.
2. The Revolution of Powder Metallurgy HSS (PM HSS)
The PM process eliminates the carbide segregation issues found in traditional cast/forged HSS.
- Core Advantages: It provides a highly uniform microstructure with drastically improved strength and toughness. It enables the production of ultra-high alloy grades (like ASP2060, reaching 67–70 HRC) that are impossible to manufacture via traditional smelting.
- Applications: Ideal for high-speed cutting and precision tools used in high-volume automated production lines.
| Code | Compare grades | Main ingredients and grades similar to traditional smelted steel | Tool features | Hardness HRC |
| ASP2015 (Sweden) | CPM Rex T15 (USA) | W12Cr4V5Co5(T15) | Precision and complexity, high-speed cutting tools, high heat resistance. | 67～69 |
| ASP2023 | S790PM Austria S690PM | W6Mo5Cr4V3(M3) / W6Mo5Cr4V4(M4) | High toughness, high compression resistance, high wear resistance | >65 |
| ASP2023 | S590PM / CPM Rex 76 | W6o5Cr4V3Co8(M36) / W10Mo5Cr4V3Co9(M48) | High wear resistance, high toughness, high thermal hardness | >66 |
| ASP2052 | S390PM | W10Mo2Cr4V5 Co8 | High wear resistance, high toughness | 66～68 |
| ASP2053 | P4M3φ8-MΠ Former Soviet Union | W4Mo3Cr4V8 | High wear resistance, high toughness | 66～68 |
| ASP2060 | P6M7φ6K10-MΠ | W6Mo7Cr4V6Co10 | High wear resistance, high thermal hardness | 66～70 |
3. Critical Heat Treatment Process Selection
Heat treatment is the process that gives an HSS tool its “soul,” with Quenching Temperature being the most vital parameter.
- Selecting Quenching Temperature:
- For High Red Hardness: Choose the upper limit of the heating range to ensure alloy carbides are fully dissolved into the matrix.
- For High Toughness/Complex Shapes: Choose the lower limit to prevent grain coarsening or cracking in delicate sections.
- Grain Size Control: Quenched grain size is generally required to be between levels 9.5 and 12, with overheating levels strictly below level 2.
- Tempering Strategy: Usually requires three rounds of tempering to ensure the complete transformation of retained austenite and to achieve the “secondary hardening” effect.
| Product Name | Specification | Quenching Heating Temperature / ℃ | Quenched Grain Size | Degree of Overheating |
| Gear hobs, disc gear milling cutters, straight shank end mills, etc. buried in salt bath heating products | All | 1170～1180 | 9～10.5 | ≤1 level |
| Taper shank end mills, taper shank keyway milling cutters and other locally heated products | All | 1175～1185 | 9～10.5 | ≤1 level |
| Various drill bits, reamer | ≥Φ15 All | 1165～1175 | 9.5～10.5 | ≤1 level |
| Various broaches, push knives | Middle | 1170～1180 | 9.5～11 | ≤1 level |
📊 Comparison: Common High-Performance HSS Grades
| Category | Representative Grade | Core Characteristics | Recommended Hardness (HRC) | Typical Tools |
|---|---|---|---|---|
| General Purpose | M2 | Excellent toughness and grindability | 63 – 65 | Standard drills, taps |
| Super Hard | M42 | Extreme red hardness; high wear resistance | 66 – 68 | Aerospace & stainless steel tools |
| Tough/Hard | M35 | Balanced strength and toughness | 65 – 67 | Gear hobs, gear shaper cutters |
| Ultra-PM | ASP2060 | Extreme wear & thermal stability | 67 – 70 |
💡 Expert Advice: How to Match the Right HSS Material?
- Workpiece Hardness: If the workpiece exceeds 280 HBW, prioritize high-performance grades like M42 or M35.
- Tool Complexity: For large, thin-walled, or complex-shaped tools, toughness is more critical than raw hardness. PM HSS is recommended to prevent catastrophic chipping during use.
- Operation Environment: In continuous, heavy-duty cutting where high heat is generated, higher cobalt content leads to more stable tool life.
Keywords
- Primary Keywords: High-Performance HSS, High-Speed Steel Materials, Tool Heat Treatment, M42 Steel.
- Secondary Keywords: Powder Metallurgy HSS (PM HSS), Quenching temperature, Tool material selection, Red hardness.
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