AISI M2 High Speed Steel: Tungsten-Molybdenum — Cutting Tools, Drills & End Mills
ASTM A600 / ISO HS6-5-2C / DIN 1.3343 · Published: 2026-05-31 · Updated: 2026-05-31
AISI M2 is the most widely used high-speed steel (HSS) globally, accounting for over 50% of annual HSS tonnage. It is a tungsten-molybdenum grade (6% W, 5% Mo, 4% Cr, 2% V) that achieves secondary hardening during tempering at 550-560°C through...
AISI M2 is the most widely used high-speed steel (HSS) globally, accounting for over 50% of annual HSS tonnage. It is a tungsten-molybdenum grade (6% W, 5% Mo, 4% Cr, 2% V) that achieves secondary hardening during tempering at 550-560°C through precipitation of M₂C and MC carbides — this is what gives HSS its defining ability to maintain hardness and cutting ability at temperatures up to 540°C (1000°F), hence 'high speed' (cutting speeds that generate red-heat at the tool edge without softening). M2 competes against cemented carbide and ceramic tooling in many applications; it remains cost-effective for drills, taps, broaches, gear cutters, and milling cutters where carbide's brittleness or cost is a barrier.
Quick Facts
| Category | Tool Steel |
| Standard | ASTM A600 / ISO HS6-5-2C / DIN 1.3343 |
| Density | 8.14 g/cm³ |
| Yield Strength | Compressive yield ~3000 MPa at 64 HRC |
| Tensile Strength | 2000-2500 MPa depending on tempering |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| EN HS6-5-2C | Compare |
| DIN 1.3343 | Compare |
| JIS SKH51 | Compare |
| GB W6Mo5Cr4V2 | Compare |
| Böhler S600 | Compare |
Related Materials
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Frequently Asked Questions
How does M2 compare to M42 cobalt HSS?
M42 adds 8% cobalt which raises the hot hardness — the temperature at which the tool loses cutting ability. M2 retains ~60 HRC to 540°C (1000°F); M42 retains ~62 HRC to 595°C (1100°F). For general machining of carbon and low-alloy steels, M2 is fully adequate. Specify M42 for: (1) machining austenitic stainless steels (304/316 — work-hardening demands higher hot hardness); (2) nickel-based superalloys (Inconel 718 — cutting temperatures easily exceed 600°C at the tool edge); (3) high-speed dry machining where coolant cannot extract heat fast enough. M42 costs approximately 3-5× M2 — the premium is only justified when the M2 tool fails from thermal softening, not wear.
References & International Standards
- ASTM International. Standard Specifications for Steel & Metal Alloys. astm.org
- International Organization for Standardization (ISO). Metallic Materials — Cross-Reference Database. iso.org
- American Iron and Steel Institute (AISI). Steel Grade Designations & Equivalents. steel.org
- European Committee for Standardization (CEN). EN Steel Standards & Numbering System. cencenelec.eu