Stainless Steel 440B
AISI/SAE 440B · UNS S44003 · EN 1.4112 · JIS SUS440B · GB 78Cr17, 8Cr17
440B is a mid-carbon 440-series martensitic stainless (S44003, 78Cr17, 8Cr17, SUS440B) that sits between 440A and 440C, trading some attainable hardness for toughness.
Values for the Annealed condition
440B tempers and conditions
440B is supplied in 5 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault fully/subcritically annealed (soft, machinable) | Standard stock condition for bar, strip and blanks that will be machined and then hardened by the user. | 425 | 740 | 18 | 220 HB | — |
Cold-drawn/ground bar and wire | Pick for close-tolerance bar, wire and shafting where slightly higher as-supplied strength and a better surface are needed before hardening. | 640 | 880 | 10 | 26 HRC | 2.9 % IACS |
Hardened & Tempered | Slightly tougher/lower-hardness option for shafts and highly stressed parts; corrosion resistance drops because of carbide precipitation, so avoid in wet chloride service. | 1,500 | 1,720 | 4 | 51 HRC | — |
1010–1065 °C quench + 150–200 °C temper (55–57 HRC) | The standard service condition for blades, valve seats and wear parts: maximum hardness, wear resistance and best corrosion resistance of the hardened states. | 1,620 | 1,860 | 3 | 56 HRC | — |
Hardened + sub-zero treated + double tempered | Choose for gauge-stable, maximum-hardness parts (bearing balls, precision cutlery) where retained austenite must be transformed. | 1,700 | 1,930 | 2 | 58 HRC | 2.8 % IACS |
What is 440B?
440B is a mid-carbon 440-series martensitic stainless (S44003, 78Cr17, 8Cr17, SUS440B) that sits between 440A and 440C, trading some attainable hardness for toughness. It is bought as annealed or annealed-plus-cold-drawn bar and strip, or supplied hardened and tempered, including H&T 50–52 HRC and hardened-plus-cryo-plus-double-temper routes for blade and wear parts; annealed properties are 425 MPa yield, 740 MPa tensile, 18% elongation and 220 HB. Limits are poor weldability, low formability (score 30), a 425 °C service ceiling and corrosion resistance (score 40) that depends on being fully hardened and passivated. Choose 440C for maximum hardness or 440F for easier machining. 440B has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,370°C (2,498 °F). 440B has a yield strength of 425 MPa (61.6 ksi) and a tensile strength of 740 MPa (107 ksi) — stronger than 66% of stainless steel grades. Elongation at break is 18% and the elastic modulus is 200 GPa (29 Msi).
What is 440B used for?
- Kitchen knife blades
- Pocket knife and folder blades
- Scissors and shear blades
- Valve seats and wear plates
- Bearing balls and races
- Surgical and dental instruments
- Wear bushings and pivot pins
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
- Low fracture toughness — 40 MPa·√m (36.4 ksi·√in), worse than 97% of stainless steel grades
- Difficult to weld — 20/100, worse than 95% of stainless steel grades
- Needs corrosion protection — 40/100, worse than 93% of stainless steel grades
- Limited ductility — 18%, worse than 83% of stainless steel grades
440B properties
Typical room-temperature values for 440B-Annealed; bars are the position among stainless steel grades.
Physical3
440B has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,370°C (2,498 °F).
Mechanical16
440B has a yield strength of 425 MPa (61.6 ksi) and a tensile strength of 740 MPa (107 ksi) — stronger than 66% of stainless steel grades. Elongation at break is 18% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
440B is rated for continuous service to 425°C (797 °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
440B conducts electricity at 2.9 % IACS, better than 87% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (40/100), worse than 93% of stainless steel grades.
Sustainability4
Producing a kilogram of 440B takes about 53 MJ of energy and emits 4.2 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 50%.
Manufacturability7
440B's machinability is fair (38/100, better than 63% of stainless steel grades); weldability poor (20/100); formability poor (30/100).
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. 440B is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 440B
Is 440B easy to machine?
Machine only in the annealed condition with rigid setups, sharp positive-rake carbide, low speed/heavy feed and flood coolant; hardened parts require grinding or EDM.
Can 440B be welded?
Poor weldability — preheat 200–300 °C, use matching or austenitic filler, and follow with a full anneal or hardening cycle to avoid HAZ cracking.
Can 440B be formed, bent or molded?
Only mild cold forming of annealed strip is practical; hot work at 1000–1150 °C with slow cooling and immediate anneal to prevent quench cracks.
Manufacturability
The process limits FabDigit applies to 440B. Every 440B part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Fair38 / 100 |
|---|---|
| ISO material group | M.4 |
| Cutting speed (rough / finish) | 140 / 170 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1.5 mm |
| Drill depth limit | 4× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
440B 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 |
|---|---|---|
| Cdistinguishes 440B from 440A (0.60–0.75) and 440C (0.95–1.20) | 0.75 – 0.95 | 0.85 |
| Cr | 16 – 18 | 17 |
| Mn | ≤ 1 | 0.4 |
| Si | ≤ 1 | 0.4 |
| Momax; optional, aids hardenability | ≤ 0.75 | 0.4 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Fe | balance |
What surface finishes work on 440B?
Harden, then grind and polish before final passivation; hardened surfaces take a mirror/edge finish, and hard chrome or nitriding is used only where extra wear life is needed.
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).
Plating
Organic Coating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel 440B in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S44003
- EN / DIN / Werkstoff-Nr.
- 1.4112
- GB (China)
- 78Cr178Cr17
- JIS
- SUS440B
How much does 440B cost?
440B is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
440B — frequently asked
What is 440B used for?
440B is typically used for kitchen knife blades, pocket knife and folder blades, scissors and shear blades, valve seats and wear plates, bearing balls and races and surgical and dental instruments. In short: cutlery-grade hardenable stainless.
What is the yield strength of 440B?
440B has a typical yield strength of 425 MPa (61.6 ksi) and a tensile strength of 740 MPa (107 ksi) — stronger than 66% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is 440B easy to machine?
Not especially — machinability is rated fair (38/100, better than 63% of stainless steel grades). Machine only in the annealed condition with rigid setups, sharp positive-rake carbide, low speed/heavy feed and flood coolant; hardened parts require grinding or EDM.
Can 440B be welded?
Not readily — weldability is rated poor (20/100). Poor weldability — preheat 200–300 °C, use matching or austenitic filler, and follow with a full anneal or hardening cycle to avoid HAZ cracking.
What surface finishes work on 440B?
Harden, then grind and polish before final passivation; hardened surfaces take a mirror/edge finish, and hard chrome or nitriding is used only where extra wear life is needed.
Can 440B be formed, bent or molded?
Only mild cold forming of annealed strip is practical; hot work at 1000–1150 °C with slow cooling and immediate anneal to prevent quench cracks.
What is the maximum service temperature of 440B?
440B is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 440B cost?
440B is a premium-cost stainless steel ($$$), 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.
Can FabDigit make parts in 440B?
Yes — 440B 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 (2023)
- EN 10088-3 (X90CrMoV18, 1.4112) — CEN (2014)
- JIS G 4303 (SUS440B) — JSA (2021)
- ASM Handbook Vol. 1: Properties and Selection — Irons, Steels — 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; 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.