440C Explained

440C (UNS designation S44004) is a martensitic 400 series stainless steel,^[1] and has the highest carbon content of the 400 stainless steel series. It can be heat treated to reach hardness of 58 to 60 HRC. It can be used to make rolling contact stainless bearings, e.g. ball bearings and roller bearings. It is also used to make knife blades.

440C has the highest strength, hardness, and wear resistance of all the commonplace 440-series stainless alloys, with high carbon content and moderate corrosion resistance.^[2]

Composition

Chemical Composition (wt%)^[3] !C!Cr!Mn!Si!Mo!P!S!Fe

0.95-1.20

16.0-18.0

1.00

1.00

0.75

0.040

0.030

Balance

Mechanical properties

Typical Mechanical Properties as a Bar ^[4] !Heat Treatment!Young's Modulus (GPa)!0.2% Offset Yield Strength (MPa)!Tensile Strength (MPa)!Elongation (%)!Rockwell Hardness!CTE (0-100 °C) (μm/m)!Thermal Conductivity (at 100 °C) (W/m*K)

Annealed	200	425	760	14	97 HRB	10.2	24.2
Tempered at 315 °C	200	1900	1970	2	57 HRC	10.2	24.2

Notes and References

1. Book: Cramer, Stephen D.. ASM handbook, Volume 13B- Corrosion: Materials. Covino. Bernard S.. ASM International. 2005. 978-1-62708-011-8. Materials Park, OH. 56. 712545628.
2. Web site: 440C Stainless Steel Products and Specifications - Penn Stainless Products Penn Stainless Products . www.pennstainless.com.
3. Web site: AISI 440C Knife Steel Composition Analysis Graph and Information Details. 5 August 2013.
4. Book: ASM International Handbook Committee.. ASM Handbook, Volume 01 - Properties and Selection: Irons, Steels, and High-Performance Alloys. ASM International. 1990. 978-1-61503-160-3. 1117847668.