Stainless Steel 440A Hardened
Heat-treated state
AISI/SAE 440A · UNS S44002 · EN 1.4109 · JIS SUS440A · GB 68Cr17, 7Cr17
As-quenched maximum hardness; must be tempered promptly to avoid cracking.
Values for the Hardened condition
Other 440A tempers and conditions
440A is listed in 7 conditions; see the grade overview at 440A.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault full/subcritical annealed, soft machinable condition | Stock condition for machining, blanking and grinding before hardening. | 415 | 725 | 20 | 195 HB | — |
annealed then cold-drawn/turned-ground-polished bar | Pick for close-tolerance bright bar going straight to screw-machine work. | 620 | 830 | 12 | 24 HRC | 2.9 % IACS |
quenched and high-temperature tempered (~40 HRC) | Use only when higher toughness or elevated-temperature stability is needed; corrosion resistance drops. | 1,080 | 1,280 | 9 | 40 HRC | — |
quenched and tempered, typical service condition (~50–52 HRC) | General service condition for blades, valve parts and wear components. | 1,650 | 1,790 | 5 | 51 HRC | — |
quenched and tempered at 315 °C (~51 HRC) | Standard published H&T condition — balanced hardness, strength and toughness. | 1,650 | 1,790 | 5 | 51 HRC | — |
quenched and low-temperature tempered (~55–56 HRC) | Maximum hardness and edge retention with best corrosion resistance; lowest toughness. | 1,720 | 1,860 | 4 | 56 HRC | — |
HardenedThis page austenitized 1010–1065 °C, quenched, untempered | As-quenched maximum hardness; must be tempered promptly to avoid cracking. | 1,900 | 2,000 | 1 | 57 HRC | 2.7 % IACS |
What is 440A Hardened?
440A Hardened is 440A heat treated to Hardened — as-quenched maximum hardness; must be tempered promptly to avoid cracking. 440A Hardened has a yield strength of 1,900 MPa (276 ksi) and a tensile strength of 2,000 MPa (290 ksi) — stronger than 100% of stainless steel grades. Elongation at break is 1% and the elastic modulus is 200 GPa (29 Msi). 440A Hardened 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). Annealed is the default condition FabDigit quotes; Hardened is available on request or by drawing note.
Advantages
- High strength — 1,900 MPa (276 ksi), better than 100% 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 — 2.7 % IACS, better than 78% of stainless steel grades
Limitations
- Limited ductility — 1%, worse than 100% of stainless steel grades
- Limited service temperature — 150°C (302 °F), worse than 100% of stainless steel grades
- Difficult to machine — 5/100, worse than 100% of stainless steel grades
- Difficult to weld — 5/100, worse than 100% of stainless steel grades
- Limited formability — 2/100, worse than 100% of stainless steel grades
440A Hardened properties
Typical room-temperature values for 440A Hardened; 22 are specific to this condition. Other listed values are 440A reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
440A Hardened 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).
Mechanical14
440A Hardened has a yield strength of 1,900 MPa (276 ksi) and a tensile strength of 2,000 MPa (290 ksi) — stronger than 100% of stainless steel grades. Elongation at break is 1% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
440A Hardened is rated for continuous service to 150°C (302 °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
440A Hardened conducts electricity at 2.7 % IACS, better than 78% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (55/100), worse than 71% of stainless steel grades.
Sustainability4
Producing a kilogram of 440A Hardened takes about 55 MJ of energy and emits 5.5 kg of CO₂ — more than 50% of stainless steel grades. Typical recycled content is 45%.
Manufacturability7
440A Hardened's machinability is not recommended (5/100, worse than 100% of stainless steel grades); weldability not recommended (5/100); formability not recommended (2/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 440A Hardened
Is 440A easy to machine?
Machine only in the annealed condition with sharp, rigid, positive-rake carbide tooling and heavy coolant; hardened parts require grinding or EDM.
Can 440A be welded?
Poor weldability — preheat 200–315 °C, use matching or austenitic filler, and temper/anneal immediately after welding to avoid cracking.
Can 440A be formed, bent or molded?
Limited cold forming in the annealed state (simple bends with generous radii); hot work 1050–1150 °C and cool slowly to prevent cracking.
What surface finishes work on 440A?
Passivate (citric or nitric per ASTM A967) after hardening for full corrosion resistance; takes a fine mirror polish, and hard chrome or black oxide are common wear/cosmetic options.
440A 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 |
|---|---|---|
| Chigh carbon for martensite + Cr carbides | 0.6 – 0.75 | 0.68 |
| Cr | 16 – 18 | 17 |
| Mn | ≤ 1 | 0.4 |
| Si | ≤ 1 | 0.4 |
| Mooptional | ≤ 0.75 | 0.3 |
| P | ≤ 0.04 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
440A Hardened — frequently asked
What is 440A Hardened used for?
440A Hardened is typically used for diving and utility knife blades, cutlery blades, shear and slitting blades, valve components and seats, bearing races and surgical and medical instruments. In short: tough cutting stainless.
What is the yield strength of 440A Hardened?
440A Hardened has a typical yield strength of 1,900 MPa (276 ksi) and a tensile strength of 2,000 MPa (290 ksi) — stronger than 100% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is 440A Hardened easy to machine?
Not especially — machinability is rated not recommended (5/100, worse than 100% of stainless steel grades). Machine only in the annealed condition with sharp, rigid, positive-rake carbide tooling and heavy coolant; hardened parts require grinding or EDM.
Can 440A Hardened be welded?
Not readily — weldability is rated not recommended (5/100). Poor weldability — preheat 200–315 °C, use matching or austenitic filler, and temper/anneal immediately after welding to avoid cracking.
What surface finishes work on 440A Hardened?
Passivate (citric or nitric per ASTM A967) after hardening for full corrosion resistance; takes a fine mirror polish, and hard chrome or black oxide are common wear/cosmetic options.
Can 440A Hardened be formed, bent or molded?
Limited cold forming in the annealed state (simple bends with generous radii); hot work 1050–1150 °C and cool slowly to prevent cracking.
What is the maximum service temperature of 440A Hardened?
440A Hardened is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in 440A Hardened?
Yes — 440A Hardened is available for CNC machining; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A276/A276M — Stainless Steel Bars and Shapes — ASTM International (2023)
- JIS G 4303 — Stainless Steel Bars (SUS440A) — JSA (2021)
- EN 10088-3 (X70CrMo15, 1.4109) — CEN (2014)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- 440A/440B/440C Stainless Steel Product Data Sheet — AK Steel / Cleveland-Cliffs (2016)
- GB/T 1220 (9Cr18) — SAC (2007)
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.