Stainless Steel 431
AISI/SAE 431 · UNS S43100 · EN 1.4057, X17CrNi16-2 · JIS SUS431 · GB 17Cr16Ni2, 1Cr17Ni2
431 is a chromium-nickel martensitic stainless (S43100, 1.4057, X17CrNi16-2) whose ~16% Cr plus nickel addition gives higher toughness and better corrosion resistance than straight-chromium 410/420.
Values for the Hardened & Tempered condition
431 tempers and conditions
431 is supplied in 8 conditions, soft to hard. Hardened & Tempered is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
EN 10088-3 quenched and tempered, Rm 700–850 MPa | Lowest-strength QT class in EN 10088-3; pick for large sections or where machining and toughness matter more than strength. | 540 | 770 | 16 | 22 HRC | 2.4 % IACS |
EN 10088-3 quenched and tempered, Rm 800–950 MPa | Common European bar condition for pump/valve shafts, KV ≥ 20 J with good corrosion resistance. | 650 | 870 | 15 | 27 HRC | 2.4 % IACS |
Condition A / EN +A (soft annealed bar, sheet) | Stock condition for machining and subsequent heat treatment; note 431 is still quite strong when annealed because it air-hardens. | 655 | 830 | 22 | 26 HRC | — |
EN 10088-3 quenched and tempered, Rm 900–1050 MPa | Highest standard EN QT class; use where strength governs and impact requirement is modest (KV ≥ 15 J). | 750 | 970 | 13 | 31 HRC | 2.4 % IACS |
Hardened & TemperedDefault oil/air quench + high temper (~600–650 °C), 28–34 HRC | The normal supply and service condition: best balance of strength, toughness and corrosion resistance for shafts, stems and fasteners. | 760 | 950 | 16 | 31 HRC | — |
Cold Drawn (annealed + cold drawn bar/wire) | Precision-size bar with improved straightness and surface for machined parts that will not be re-heat-treated. | 760 | 930 | 12 | 30 HRC | 2.4 % IACS |
Hardened & low-temper | Maximum-strength/wear condition for stems, bushings and cutlery-type parts; accept low impact toughness and no notches. | 1,080 | 1,330 | 10 | 42 HRC | — |
45–48 HRC | Intermediate state only — must be tempered before use; retained stresses make it crack-prone. | 1,200 | 1,500 | 5 | 46 HRC | 2.3 % IACS |
What is 431?
431 is a chromium-nickel martensitic stainless (S43100, 1.4057, X17CrNi16-2) whose ~16% Cr plus nickel addition gives higher toughness and better corrosion resistance than straight-chromium 410/420. Engineers specify it for high-strength shafting and fasteners, typically as turned or ground bar and cold-drawn bar in annealed, hardened-and-tempered or +QT700/+QT800/+QT900 conditions; the default condition gives 760 MPa yield, 950 MPa tensile, 16% elongation and about 300 HB (31 HRC). Limits are poor weldability from an air-hardening HAZ, a 450 °C service ceiling and only moderate machinability (score 35). Where welding is required, choose a stabilized ferritic or austenitic grade instead. 431 has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,425°C (2,597 °F). 431 has a yield strength of 760 MPa (110 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 94% of stainless steel grades. Elongation at break is 16% and the elastic modulus is 200 GPa (29 Msi).
What is 431 used for?
- Marine propeller and rudder shafts
- Pump and mixer shafts
- High-strength bolts and studs
- Valve stems and spindles
- Steam and gas turbine blades
- Aerospace fittings and linkages
- Gears and shaft couplings
Advantages
- High strength — 760 MPa (110 ksi), better than 94% of stainless steel grades
Limitations
- Difficult to weld — 25/100, worse than 92% of stainless steel grades
- Limited ductility — 16%, worse than 88% of stainless steel grades
- Needs corrosion protection — 48/100, worse than 80% of stainless steel grades
- Low fracture toughness — 80 MPa·√m (72.8 ksi·√in), worse than 79% of stainless steel grades
- Limited formability — 25/100, worse than 78% of stainless steel grades
431 properties
Typical room-temperature values for 431-Hardened & Tempered; bars are the position among stainless steel grades.
Physical3
431 has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
431 has a yield strength of 760 MPa (110 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 94% of stainless steel grades. Elongation at break is 16% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
431 is rated for continuous service to 450°C (842 °F). It conducts heat at 20.2 W/m·K (11.7 BTU/hr·ft·°F), better than 74% of stainless steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
431 conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (48/100), worse than 80% of stainless steel grades.
Sustainability4
Producing a kilogram of 431 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
431's machinability is fair (35/100, better than 51% of stainless steel grades); weldability poor (25/100); formability poor (25/100).
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. 431 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 431
Is 431 easy to machine?
Machine in the annealed or ≤32 HRC condition with rigid setups, sharp carbide, positive rake, heavy flood coolant and constant feed to avoid work hardening; expect ~40 % of 1212 and use ground/turned bar for finish-critical diameters.
Can 431 be welded?
Best avoided — air-hardening HAZ cracks readily; if required, preheat 200–300 °C, use 309/310 or matching 431 filler, weld hot and immediately post-weld temper at 620–650 °C, then slow cool.
Can 431 be formed, bent or molded?
Hot work 1150–900 °C then slow cool/anneal; cold forming is limited to gentle bends in the annealed state, and all forming should be done before hardening.
Manufacturability
The process limits FabDigit applies to 431. Every 431 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Fair35 / 100 |
|---|---|
| ISO material group | M.1 |
| Cutting speed (rough / finish) | 150 / 180 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 |
Sheet metal
| Formability | Fair25 / 100 |
|---|---|
| Weldability | Poor25 / 100 |
431 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 |
|---|---|---|
| CASTM A276 S43100: 0.20 max; EN 1.4057: 0.12–0.22 | 0.12 – 0.2 | 0.17 |
| Si | ≤ 1 | 0.5 |
| Mn | ≤ 1 | 0.6 |
| P | ≤ 0.04 | 0.03 |
| SEN 1.4057 S ≤ 0.015; free-machining sulphurised versions (BS 431S29 type) run higher | ≤ 0.03 | 0.02 |
| Cr | 15 – 17 | 16 |
| NiEN 1.4057: 1.5–2.5 | 1.25 – 2.5 | 2 |
| Monot specified in ASTM; EN permits residual Mo ≤ 0.8 | ≤ 0.8 | |
| Fe | balance |
What surface finishes work on 431?
Passivate per ASTM A967 after machining/grinding; polishes to a bright finish and takes hard chrome, electroless nickel or nitriding — do not bake or plate-relieve in the 370–570 °C embrittlement window.
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 431 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does 431 cost?
431 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.
431 — frequently asked
What is 431 used for?
431 is typically used for marine propeller and rudder shafts, pump and mixer shafts, high-strength bolts and studs, valve stems and spindles, steam and gas turbine blades and aerospace fittings and linkages. In short: high-strength martensitic shafting.
What is the yield strength of 431?
431 has a typical yield strength of 760 MPa (110 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 94% of stainless steel grades. Strength varies by condition: see the 8 listed tempers.
Is 431 easy to machine?
Not especially — machinability is rated fair (35/100, better than 51% of stainless steel grades). Machine in the annealed or ≤32 HRC condition with rigid setups, sharp carbide, positive rake, heavy flood coolant and constant feed to avoid work hardening; expect ~40 % of 1212 and use ground/turned bar for finish-critical diameters.
Can 431 be welded?
Not readily — weldability is rated poor (25/100). Best avoided — air-hardening HAZ cracks readily; if required, preheat 200–300 °C, use 309/310 or matching 431 filler, weld hot and immediately post-weld temper at 620–650 °C, then slow cool.
What surface finishes work on 431?
Passivate per ASTM A967 after machining/grinding; polishes to a bright finish and takes hard chrome, electroless nickel or nitriding — do not bake or plate-relieve in the 370–570 °C embrittlement window.
Can 431 be formed, bent or molded?
Hot work 1150–900 °C then slow cool/anneal; cold forming is limited to gentle bends in the annealed state, and all forming should be done before hardening.
What is the maximum service temperature of 431?
431 is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 431 cost?
431 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 431?
Yes — 431 is available for CNC machining and sheet metal; 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)
- ASTM A582/A582M — Free-Machining Stainless Steel Bars — ASTM International (2021)
- EN 10088-3 — Stainless steels: semi-finished products, bars, rods (X17CrNi16-2, 1.4057) — CEN (2014)
- AMS 5628 — Steel Bars, Forgings, 16Cr–2.0Ni — SAE International (2018)
- GB/T 1220 — (14Cr17Ni2) — SAC (2007)
- ASM Handbook Vol. 1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- Martensitic stainless steel 1.4057/431 bar datasheet — European long-product mill (typical values) (2022)
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.