Stainless Steel SUS440C-QT450
Heat-treated state
JIS SUS440C · UNS S44004
QT450 = hardened + tempered 425–480 °C
Used only when elevated-temperature hardness retention matters; temper embrittlement and reduced corrosion resistance make it a poor default.
Values for the QT450 condition
Other SUS440C tempers and conditions
SUS440C is listed in 7 conditions; see the grade overview at SUS440C.
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 |
QT450This page 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-QT450?
SUS440C-QT450 is SUS440C heat treated to QT450 — used only when elevated-temperature hardness retention matters; temper embrittlement and reduced corrosion resistance make it a poor default. SUS440C-QT450 has a yield strength of 1,700 MPa (247 ksi) and a tensile strength of 1,830 MPa (265 ksi) — stronger than 100% of stainless steel grades. Elongation at break is 3% and the elastic modulus is 200 GPa (29 Msi). SUS440C-QT450 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). A is the default condition FabDigit quotes; QT450 is available on request or by drawing note.
Advantages
- High strength — 1,700 MPa (247 ksi), better than 100% of stainless steel grades
- Polishes to a fine finish — 85/100, better than 97% of stainless steel grades
- Conducts heat well — 24 W/m·K (13.9 BTU/hr·ft·°F), better than 81% of stainless steel grades
- High electrical conductivity — 2.8 % IACS, better than 79% of stainless steel grades
Limitations
- Limited ductility — 3%, worse than 100% of stainless steel grades
- Difficult to machine — 10/100, worse than 100% of stainless steel grades
- Difficult to weld — 5/100, worse than 100% of stainless steel grades
- Limited formability — 3/100, worse than 100% of stainless steel grades
- Needs corrosion protection — 32/100, worse than 99% of stainless steel grades
SUS440C-QT450 properties
Typical room-temperature values for SUS440C-QT450; 22 are specific to this condition. Other listed values are SUS440C reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
SUS440C-QT450 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-QT450 has a yield strength of 1,700 MPa (247 ksi) and a tensile strength of 1,830 MPa (265 ksi) — stronger than 100% of stainless steel grades. Elongation at break is 3% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
SUS440C-QT450 is rated for continuous service to 400°C (752 °F). It conducts heat at 24 W/m·K (13.9 BTU/hr·ft·°F), better than 81% of stainless steel grades. Thermal expansion is 10.2 µm/m·K (5.67 µin/in·°F).
Electrical3
SUS440C-QT450 conducts electricity at 2.8 % IACS, better than 79% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is poor (32/100), worse than 99% of stainless steel grades.
Sustainability4
Producing a kilogram of SUS440C-QT450 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-QT450's machinability is not recommended (10/100, worse than 100% of stainless steel grades); weldability not recommended (5/100); formability not recommended (3/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SUS440C-QT450
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.
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.
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 | — |
SUS440C-QT450 — frequently asked
What is SUS440C-QT450 used for?
SUS440C-QT450 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-QT450?
SUS440C-QT450 has a typical yield strength of 1,700 MPa (247 ksi) and a tensile strength of 1,830 MPa (265 ksi) — stronger than 100% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is SUS440C-QT450 easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 100% 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-QT450 be welded?
Not readily — weldability is rated not recommended (5/100). 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-QT450?
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-QT450 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-QT450?
SUS440C-QT450 is rated for continuous use to about 400°C (752 °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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.