440C is a high-carbon martensitic stainless steel that achieves the highest hardness (up to 60 HRC) of all stainless alloys, delivering exceptional wear resistance and razor-sharp edge retention.
Engineering Specifications & Parameters
Density
7.80 g/cm³
Hardness (Annealed)
230 - 260 Brinell (HB)
Hardness (Hardened)
58 - 60 Rockwell C (HRC)
Corrosion Resistance
Moderate (Resists fresh water and mild chemicals)
Machinability (Annealed)
40% (Tough)
Yield Strength (Hardened)
1900 MPa (275,000 psi)
High Carbon Martensitic Metallurgy
With 0.95–1.20% carbon and 16–18% chromium, 440C exhibits extreme hardness and high abrasive wear resistance after quenching and tempering.
Machining Feeds, Speeds & Annealed Strategy
Annealed Machining: In the annealed state (~230 HB), machine at cutting speeds of 60 – 100 m/min using heavy-duty coated carbide tools.
Hard Milling (Post Heat-Treat): When hardened to 58–60 HRC, use CBN inserts or multi-flute ultra-micrograin carbide end mills with mist air coolant.
Frequently Asked Questions
How does 440C compare to 304/316 stainless steel?
440C can be hardened to 60 HRC for extreme wear resistance, whereas 304 and 316 are non-hardenable austenitic grades offering higher corrosion resistance.
What coolant is recommended when roughing 440C in annealed state?
High-pressure sulfur-free synthetic coolant with extreme pressure (EP) additives.
