Stainless Steel SUS440C
JIS SUS440C · UNS S44004
SUS440C (S44004) is the JIS high-carbon martensitic stainless equivalent to AISI 440C, quench-and-temper hardened for bearings and blades that need maximum hardness with useful corrosion resistance.
Reference datasheet — SUS440C is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the A condition
SUS440C tempers and conditions
SUS440C is supplied in 7 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard stocking condition of bar/plate: machine and form parts, then harden and temper. | 450 | 760 | 14 | 22 HRC | — |
Annealed + cold drawn / centreless ground bar | Pick for close-tolerance shafting and screw-machine stock that will be hardened later. | 620 | 860 | 10 | 28 HRC | — |
Hardened + tempered 540–600 °C | Choose only for parts that must run warm (up to ~480 °C) or need lower hardness with dimensional stability; corrosion resistance is clearly degraded. | 1,550 | 1,700 | 5 | 52 HRC | 2.8 % IACS |
Hardened + tempered 425–480 °C | Used only when elevated-temperature hardness retention matters; temper embrittlement and reduced corrosion resistance make it a poor default. | 1,700 | 1,830 | 3 | 55 HRC | 2.8 % IACS |
Hardened + tempered 260–320 °C | Slightly tougher than the 180 °C temper for shock-loaded tooling and cutlery; corrosion resistance begins to fall. | 1,740 | 1,860 | 3 | 56 HRC | — |
Hardened | Maximum attainable hardness for wear tests or as an intermediate state; must be tempered before service to avoid quench cracking. | 1,900 | 2,030 | 1 | 61 HRC | — |
Hardened + tempered 150–200 °C | The standard service condition for bearings, valve balls and knife blades: peak hardness, wear resistance and best corrosion behaviour. | 1,900 | 1,970 | 2 | 59 HRC | — |
What is SUS440C?
SUS440C (S44004) is the JIS high-carbon martensitic stainless equivalent to AISI 440C, quench-and-temper hardened for bearings and blades that need maximum hardness with useful corrosion resistance. It is on file annealed (A), annealed cold-drawn (A-CD), hardened (H) and in QT180–QT540 tempers; the default condition gives 450 MPa yield, 760 MPa tensile, 14 % elongation and 240 HB (22 HRC), with service to 600 °C. Machinability (35), formability (20) and weldability (15) are all low, and corrosion resistance (42) depends on proper passivation. 4Cr13 is the cheaper, easier-to-process alternative when peak hardness is not required. SUS440C has a density of 7.68 g/cm³ (0.277 lb/in³), lighter than 94% of stainless steel grades. It melts at 1,370°C (2,498 °F). SUS440C has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 70% of stainless steel grades. Elongation at break is 14% and the elastic modulus is 200 GPa (29 Msi).
What is SUS440C used for?
- bearings
- blades
- precision tooling
Advantages
- Polishes to a fine finish — 85/100, better than 97% of stainless steel grades
- High electrical conductivity — 2.9 % IACS, better than 87% of stainless steel grades
- Conducts heat well — 24.2 W/m·K (14 BTU/hr·ft·°F), better than 83% of stainless steel grades
Limitations
- Difficult to weld — 15/100, worse than 98% of stainless steel grades
- Limited ductility — 14%, worse than 91% of stainless steel grades
- Needs corrosion protection — 42/100, worse than 90% of stainless steel grades
- Limited formability — 20/100, worse than 86% of stainless steel grades
SUS440C properties
Typical room-temperature values for SUS440C-A; bars are the position among stainless steel grades.
Physical3
SUS440C has a density of 7.68 g/cm³ (0.277 lb/in³), lighter than 94% of stainless steel grades. It melts at 1,370°C (2,498 °F).
Mechanical15
SUS440C has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 70% of stainless steel grades. Elongation at break is 14% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
SUS440C is rated for continuous service to 600°C (1,112 °F). It conducts heat at 24.2 W/m·K (14 BTU/hr·ft·°F), better than 83% of stainless steel grades. Thermal expansion is 10.2 µm/m·K (5.67 µin/in·°F).
Electrical3
SUS440C conducts electricity at 2.9 % IACS, better than 87% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (42/100), worse than 90% of stainless steel grades.
Sustainability4
Producing a kilogram of SUS440C takes about 53 MJ of energy and emits 5 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 45%.
Manufacturability7
SUS440C's machinability is fair (35/100, better than 51% of stainless steel grades); weldability poor (15/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. SUS440C is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SUS440C
Is SUS440C easy to machine?
Machine only in the annealed condition with rigid setups, sharp carbide tooling, low speed (~40–70 m/min) and heavy coolant; the ~1% C plus chromium carbides are abrasive, and hardened parts must be ground or EDM'd.
Can SUS440C be welded?
Essentially not recommended — very high carbon gives brittle, crack-prone welds; if unavoidable, preheat 250–300 °C, use 410NiMo/309 filler and full post-weld anneal.
Can SUS440C be formed, bent or molded?
Cold forming limited to gentle bending of thin annealed stock; hot work 1100–850 °C followed by slow cool and full anneal to avoid quench cracks.
SUS440C chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CJIS G4303 SUS440C / UNS S44004 | 0.95 – 1.2 | 1.05 |
| Si | ≤ 1 | 0.4 |
| Mn | ≤ 1 | 0.45 |
| P | ≤ 0.04 | 0.03 |
| S | ≤ 0.03 | 0.01 |
| Nipermitted residual in JIS | ≤ 0.6 | 0.25 |
| Cr | 16 – 18 | 17 |
| Mo | ≤ 0.75 | 0.45 |
| Fe | balance |
What surface finishes work on SUS440C?
Passivate per ASTM A967 (citric or nitric) after hardening; takes a high mirror polish, and PVD (TiN/CrN) or hard chrome can be applied below the tempering temperature.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel SUS440C in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S44004
- Other
- 440C
How much does SUS440C cost?
SUS440C is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
SUS440C — frequently asked
What is SUS440C used for?
SUS440C is typically used for bearings, blades and precision tooling. In short: JIS 440C for maximum hardness; hardest common stainless; effectively non-weldable.
What is the yield strength of SUS440C?
SUS440C has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 70% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is SUS440C easy to machine?
Not especially — machinability is rated fair (35/100, better than 51% of stainless steel grades). Machine only in the annealed condition with rigid setups, sharp carbide tooling, low speed (~40–70 m/min) and heavy coolant; the ~1% C plus chromium carbides are abrasive, and hardened parts must be ground or EDM'd.
Can SUS440C be welded?
Not readily — weldability is rated poor (15/100). Essentially not recommended — very high carbon gives brittle, crack-prone welds; if unavoidable, preheat 250–300 °C, use 410NiMo/309 filler and full post-weld anneal.
What surface finishes work on SUS440C?
Passivate per ASTM A967 (citric or nitric) after hardening; takes a high mirror polish, and PVD (TiN/CrN) or hard chrome can be applied below the tempering temperature.
Can SUS440C be formed, bent or molded?
Cold forming limited to gentle bending of thin annealed stock; hot work 1100–850 °C followed by slow cool and full anneal to avoid quench cracks.
What is the maximum service temperature of SUS440C?
SUS440C is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SUS440C-A and SUS440C-H?
A is the default condition — standard stocking condition of bar/plate: machine and form parts, then harden and temper. H: maximum attainable hardness for wear tests or as an intermediate state; must be tempered before service to avoid quench cracking. Yield strength is 450 MPa in A versus 1,900 MPa in H.
How much does SUS440C cost?
SUS440C is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- JIS G 4303 — Stainless steel bars — JSA (2021)
- ASTM A276/A276M — Stainless Steel Bars and Shapes — ASTM (2017)
- GB/T 1220 — (9Cr18Mo) — SAC (2007)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- 440C Stainless Steel product data bulletin — AK Steel / Cleveland-Cliffs (2019)
- Machinery's Handbook — machinability ratings — Industrial Press (2020)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.