AISI M2 High-Speed Tool Steel: General-Purpose HSS
ASTM A600 · Updated: 2026-05-25
AISI M2 is the most widely used high-speed steel (HSS) with 0.78-0.88% C, 3.75-4.5% Cr, 4.5-5.5% Mo, 5.5-6.75% W, and 1.6-2.2% V. The balanced Mo-W composition provides excellent hot hardness up to 560°C—enabling cutting speeds 3-4× higher than carbon tool steels. Secondary hardening during triple tempering at 540-560°C precipitates fine Mo-W-V carbides for maximum wear resistance. Used for drill bits, end mills, taps, reamers, broaches, and lathe tools. The molybdenum-based composition (M-series) is tougher and less expensive than T-series (tungsten-based) HSS grades while providing equivalent hot hardness.
Quick Facts
| Category | Tool Steel |
| Standard | ASTM A600 |
| Density | 8.10 g/cm³ |
| Yield Strength | 3,100 MPa (450 ksi) at 64-66 HRC |
| Tensile Strength | 3,800 MPa (551 ksi) at 64-66 HRC |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| EN HS6-5-2C | Compare |
| DIN 1.3343 | Compare |
| SKH51 | Compare |
| W6Mo5Cr4V2 | Compare |
| JIS SKH51 | Compare |
Related Materials
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Frequently Asked Questions
How does M2 compare to M42 high-speed steel?
M42 adds 8% cobalt for superior hot hardness at cutting temperatures above 600°C, making it preferred for machining stainless steels, titanium, and superalloys. M42 also achieves 1-2 HRC higher hardness (66-68 HRC). M2 is the economical general-purpose HSS for carbon steels, alloy steels, and aluminum. M42 costs approximately 2-3× more than M2 due to cobalt content.