Stainless Steel 420F · hardness band

Stainless Steel 420F Q&T 40-45 HRC

Properties of the Q&T 40-45 HRC condition, compared with the other 420F tempers.

Use when a little more toughness than the 50 HRC condition is required and corrosion exposure is mild.

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What is 420F Q&T 40-45 HRC?

420F Q&T 40-45 HRC is 420F heat treated to Q&T 40-45 HRC — use when a little more toughness than the 50 HRC condition is required and corrosion exposure is mild. 420F Q&T 40-45 HRC has a yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 11% and the elastic modulus is 200 GPa (29 Msi). 420F Q&T 40-45 HRC has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 66% of stainless steel grades. It melts at 1,450°C (2,642 °F). Annealed is the default condition FabDigit quotes; Q&T 40-45 HRC is available on request or by drawing note.

Advantages

High electrical conductivity — 3.1 % IACS, better than 99% of stainless steel grades
High strength — 1,180 MPa (171 ksi), better than 98% 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 88% of stainless steel grades

Limitations

Needs corrosion protection — 30/100, worse than 99% of stainless steel grades
Difficult to weld — 12/100, worse than 99% of stainless steel grades
Limited ductility — 11%, worse than 96% of stainless steel grades
Hard to polish — 50/100, worse than 94% of stainless steel grades
Limited formability — 25/100, worse than 79% of stainless steel grades

420F Q&T 40-45 HRC properties

Typical room-temperature values for 420F Q&T 40-45 HRC — 11 properties are specific to this condition; the rest are grade-level values shared by every 420F temper. Each bar shows where the value sits among the stainless steel grades in FabDigit's library — further right is higher.

Physical3

420F Q&T 40-45 HRC has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 66% of stainless steel grades. It melts at 1,450°C (2,642 °F).

Density7.75 g/cm³0.28 lb/in³

Melting Point (Solidus)1,450°C2,642 °F

Liquidus Temperature1,510°C2,750 °F

Mechanical13

420F Q&T 40-45 HRC has a yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 11% and the elastic modulus is 200 GPa (29 Msi).

Elastic (Young's) Modulus200 GPa29 Msi

Shear Modulus78 GPa11.3 Msi

Bulk Modulus160 GPa23.2 Msi

Poisson's Ratio0.28

Tensile Strength (Ultimate)1,400 MPa203 ksi

Yield Strength (0.2% offset)1,180 MPa171 ksi

Elongation at Break11%

Reduction in Area30%

Shear Strength430 MPa62.4 ksi

Fatigue Strength (Endurance Limit)470 MPa68.2 ksi

Charpy V-Notch Impact (RT)10 J7.4 ft·lbf

Hardness, Brinell220 HB

Hardness, Rockwell B97 HRB

Thermal6

420F Q&T 40-45 HRC is rated for continuous service to 450°C (842 °F). It conducts heat at 24.9 W/m·K (14.4 BTU/hr·ft·°F), better than 88% of stainless steel grades. Thermal expansion is 10.3 µm/m·K (5.72 µin/in·°F).

Thermal Conductivity24.9 W/m·K14.4 BTU/hr·ft·°F

Specific Heat Capacity460 J/kg·K0.11 BTU/lb·°F

Thermal Expansion (CTE, 20–100 °C)10.3 µm/m·K5.7 µin/in·°F

Latent Heat of Fusion270 J/g116 BTU/lb

Max Service Temperature (continuous)450°C842 °F

Min Service Temperature-30°C-22 °F

Electrical3

420F Q&T 40-45 HRC conducts electricity at 3.1 % IACS, better than 99% of stainless steel grades.

Electrical Conductivity3.1 % IACS

Electrical Resistivity5.5×10⁻⁷ Ω·m21.7 µΩ·in

Magnetic Responseferromagnetic

Chemical & Environmental3

Corrosion resistance is poor (30/100), worse than 99% of stainless steel grades.

Galvanic Potential (seawater, vs SCE)-0.3 V

Corrosion ResistancePoor30/100

Chemical Resistance SummaryAdequate in mild atmospheres, fresh water, steam, dilute organics and food acids when hardened, tempered low and passivated; the MnS stringers are pit-initiation sites, so it is unsuitable for chlorides, seawater, or oxidising/reducing acids. Best corrosion behaviour is in the hardened + polished + passivated state.

Sustainability4

Producing a kilogram of 420F Q&T 40-45 HRC 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%.

Embodied Energy (primary production)45 MJ/kg19,347 BTU/lb

Embodied Carbon (primary production)3.4 kg CO₂/kg

Embodied Water130 L/kg15.6 gal/lb

Typical Recycled Content65%

Manufacturability8

420F Q&T 40-45 HRC's machinability is poor (28/100, worse than 80% of stainless steel grades); weldability not recommended (12/100); formability poor (25/100).

MachinabilityPoor28/100

Machinability Rating (AISI 1212 = 100 %)65%

WeldabilityNot recommended12/100

Formability (cold)Poor25/100

CastabilityFair35/100

Brazeability / SolderabilityFair35/100

PolishabilityFair50/100

Anodizing Responsen/a — ferrous alloy; use passivation (ASTM A967 nitric/citric), black oxide or hard chrome instead

Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.

Other 420F tempers and conditions

420F is also supplied in 4 other conditions. The full side-by-side table is on the 420F overview.

AnnealedDefaultStandard stock condition for screw-machine work; machine here, then harden the finished part.380 MPa yield · 220 HB
Hardened & TemperedDefault 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 MPa yield · 50 HRC
Q&T 40-45 HRCUse when a little more toughness than the 50 HRC condition is required and corrosion exposure is mild.1,180 MPa yield · 43 HRC
Q&T 28-32 HRCTough, machinable heat-treated condition for shafts and stems where hardness is secondary; corrosion resistance is the lowest of all conditions.800 MPa yield · 30 HRC
Annealed Cold DrawnPick for tight-tolerance turned parts needing better surface finish, straightness and chip control than hot-rolled annealed bar.620 MPa yield · 25 HRC

Working with 420F Q&T 40-45 HRC

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.

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.

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	—

420F Q&T 40-45 HRC — frequently asked

What is 420F Q&T 40-45 HRC used for?

420F Q&T 40-45 HRC 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 Q&T 40-45 HRC?

420F Q&T 40-45 HRC has a typical yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 98% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.

Is 420F Q&T 40-45 HRC easy to machine?

Not especially — machinability is rated poor (28/100, worse than 80% 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 Q&T 40-45 HRC 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 Q&T 40-45 HRC?

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 Q&T 40-45 HRC 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 Q&T 40-45 HRC?

420F Q&T 40-45 HRC 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.

Can FabDigit make parts in 420F Q&T 40-45 HRC?

Yes — 420F Q&T 40-45 HRC is available for CNC machining with instant online pricing. 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.