Stainless Steel 420F
AISI/SAE 420F · UNS S42020 · ASTM A582 · JIS SUS420F · GB Y3Cr13
420F (SUS420F, S42020, X29CrS13) is a high-carbon martensitic stainless with a sulfur addition for free machining, covered by ASTM A582 and hardenable to 40–45 HRC.
Values for the Annealed condition
420F tempers and conditions
420F 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 condition A, soft annealed bar | Standard stock condition for screw-machine work; machine here, then harden the finished part. | 380 | 690 | 20 | 220 HB | — |
CD bar, ground and polished sizes | Pick for tight-tolerance turned parts needing better surface finish, straightness and chip control than hot-rolled annealed bar. | 620 | 800 | 12 | 25 HRC | — |
Oil quench, high temper ≈650 °C | Tough, machinable heat-treated condition for shafts and stems where hardness is secondary; corrosion resistance is the lowest of all conditions. | 800 | 1,000 | 16 | 30 HRC | — |
Oil quench, temper ≈500 °C | Use when a little more toughness than the 50 HRC condition is required and corrosion exposure is mild. | 1,180 | 1,400 | 11 | 43 HRC | — |
oil quench 1010 °C, temper 200 °C (≈50 HRC) | Default hardened condition for cutting edges, valve stems and wear surfaces where maximum hardness and best corrosion behaviour of the hardened states are needed. | 1,480 | 1,720 | 8 | 50 HRC | — |
What is 420F?
420F (SUS420F, S42020, X29CrS13) is a high-carbon martensitic stainless with a sulfur addition for free machining, covered by ASTM A582 and hardenable to 40–45 HRC. It is machined from annealed or cold drawn bar and then heat treated, giving 380 MPa yield, 690 MPa tensile, 20% elongation and 220 HB in the default condition with a machinability score of 58. The sulfides reduce corrosion resistance (score 35), prevent sound welding and limit continuous service to 400 °C. Use 420J2 where a defect-free polish or slightly better corrosion resistance is required. 420F has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,450°C (2,642 °F). 420F has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 52% of stainless steel grades. Elongation at break is 20% and the elastic modulus is 200 GPa (29 Msi).
What is 420F used for?
- Cutlery blanks
- Dental and surgical instruments
- Scissor and shear blades
- Valve stems and seats
- Spindles and shafts
- Wear pins and bushings
- Machined tool holders
Advantages
- High electrical conductivity — 3.1 % IACS, better than 99% of stainless steel grades
- Easy to machine — 58/100, better than 97% of stainless steel grades
- Low embodied carbon — 3.4 kg CO₂/kg, better than 91% of stainless steel grades
- Conducts heat well — 24.9 W/m·K (14.4 BTU/hr·ft·°F), better than 87% of stainless steel grades
Limitations
- Difficult to weld — 12/100, worse than 99% of stainless steel grades
- Needs corrosion protection — 35/100, worse than 97% of stainless steel grades
- Hard to polish — 50/100, worse than 93% of stainless steel grades
- Limited ductility — 20%, worse than 79% of stainless steel grades
- Limited service temperature — 400°C (752 °F), worse than 78% of stainless steel grades
420F properties
Typical room-temperature values for 420F-Annealed; bars are the position among stainless steel grades.
Physical3
420F has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,450°C (2,642 °F).
Mechanical13
420F has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 52% of stainless steel grades. Elongation at break is 20% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
420F is rated for continuous service to 400°C (752 °F). It conducts heat at 24.9 W/m·K (14.4 BTU/hr·ft·°F), better than 87% of stainless steel grades. Thermal expansion is 10.3 µm/m·K (5.72 µin/in·°F).
Electrical3
420F conducts electricity at 3.1 % IACS, better than 99% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (35/100), worse than 97% of stainless steel grades.
Sustainability4
Producing a kilogram of 420F takes about 45 MJ of energy and emits 3.4 kg of CO₂ — less than 91% of stainless steel grades. Typical recycled content is 65%.
Manufacturability8
420F's machinability is good (58/100, better than 97% of stainless steel grades); weldability not recommended (12/100); 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. 420F is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 420F
Is 420F easy to machine?
Excellent for a martensitic stainless — sulfides break chips; use sharp carbide, ~60–80 % of 12L14 speeds, and machine in the annealed state before hardening.
Can 420F be welded?
Not recommended: high carbon plus sulfur gives hot cracking and brittle martensite; if unavoidable, preheat 200–300 °C, use 309/410NiMo filler and temper immediately.
Can 420F be formed, bent or molded?
Cold forming limited to light heading or straightening in the annealed condition; hot work 1150–900 °C followed by slow cool and full anneal at 840–900 °C.
Manufacturability
The process limits FabDigit applies to 420F. Every 420F part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Excellent58 / 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 |
420F 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 SUS420F allows 0.26–0.40 | 0.3 – 0.4 | 0.35 |
| Cr | 12 – 14 | 13 |
| Mn | ≤ 1.25 | 0.8 |
| Si | ≤ 1 | 0.5 |
| Sfree-machining addition; forms MnS stringers | ≥ 0.15 | 0.22 |
| P | ≤ 0.06 | 0.03 |
| Mooptional, at producer's discretion | ≤ 0.6 | |
| Fe | balance |
What surface finishes work on 420F?
Passivate per ASTM A967 (citric preferred, nitric can attack sulfides); accepts hard chrome, black oxide and PVD, but sulfide stringers prevent a defect-free mirror polish.
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 420F in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S42020
- ASTM
- A582
- GB (China)
- Y3Cr13
- JIS
- SUS420F
- Similar grades
- X29CrS13
How much does 420F cost?
420F is a standard-cost stainless steel ($$), cheaper than about 60% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
420F — frequently asked
What is 420F used for?
420F is typically used for cutlery blanks, dental and surgical instruments, scissor and shear blades, valve stems and seats, spindles and shafts and wear pins and bushings. In short: free-machining martensitic stainless.
What is the yield strength of 420F?
420F has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 52% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is 420F easy to machine?
Reasonably — machinability is rated good (58/100, better than 97% of stainless steel grades). Excellent for a martensitic stainless — sulfides break chips; use sharp carbide, ~60–80 % of 12L14 speeds, and machine in the annealed state before hardening.
Can 420F be welded?
Not readily — weldability is rated not recommended (12/100). Not recommended: high carbon plus sulfur gives hot cracking and brittle martensite; if unavoidable, preheat 200–300 °C, use 309/410NiMo filler and temper immediately.
What surface finishes work on 420F?
Passivate per ASTM A967 (citric preferred, nitric can attack sulfides); accepts hard chrome, black oxide and PVD, but sulfide stringers prevent a defect-free mirror polish.
Can 420F be formed, bent or molded?
Cold forming limited to light heading or straightening in the annealed condition; hot work 1150–900 °C followed by slow cool and full anneal at 840–900 °C.
What is the maximum service temperature of 420F?
420F is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 420F cost?
420F is a standard-cost stainless steel ($$), cheaper than about 60% 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 420F?
Yes — 420F 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 A582/A582M — Free-Machining Stainless Steel Bars — ASTM International (2021)
- JIS G 4303 — Stainless Steel Bars (SUS420F) — JSA (2021)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASTM A967/A967M — Chemical Passivation Treatments for Stainless Steel Parts — ASTM International (2017)
- Martensitic free-machining stainless bar datasheets (Sandvik / Ugitech / Outokumpu 4028-type) — various producers (2023)
- (SMM / Mysteel / 1688 ) — SMM / Mysteel (2025)
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.