Steel 4140
AISI/SAE 4140 · UNS G41400 · EN 1.7225, 42CrMo4 · JIS SCM440 · GB 42CrMo
4140 (42CrMo4 / 42CrMo / SCM440) is the workhorse medium-carbon chromium-molybdenum through-hardening alloy steel, supplied hot rolled, cold drawn or pre-hardened and used for shafts, gears, spindles, tooling holders, hydraulic bodies and oilfield components.
Values for the HR condition
4140 tempers and conditions
4140 is supplied in 14 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
- Annealed
- HR
- Stress Relieved
- Normalized
- CR
- CD
- Q&T 22-26 HRC
- HIP
- Q&T
- Nitrided
- As Printed
- Q&T 34-38 HRC
- Q&T 40-45 HRC
- Q&T 48-52 HRC
Compare all 14 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full/spheroidize annealed (≈815 °C, furnace cooled) | Softest condition — pick for heavy machining, deep cold forming or before final hardening. | 415 | 655 | 25.7 | 197 HB | — |
HRDefault Hot rolled | Cheapest general stock for parts that will be machined and then heat treated by the user. | 480 | 690 | 22 | 210 HB | — |
550–650 °C soak, slow cool | Applied after rough machining, cold work or welding to stabilise dimensions with minimal hardness loss. | 590 | 760 | 18 | 20 HRC | 7.8 % IACS |
870 °C, air cooled | Uniform fine-grain structure with mid strength; used for forgings before machining or as a delivery condition for weldments. | 655 | 1,020 | 17.7 | 31 HRC | — |
Cold rolled | Thin flat product with tight thickness tolerance and smooth surface; choose for stamped blanks to be hardened later. | 660 | 800 | 10 | 22 HRC | 7.8 % IACS |
Cold drawn | Straight, size-accurate bright bar with higher yield than hot rolled; best for machined shafts not requiring later hardening. | 660 | 800 | 15 | 22 HRC | 43 W/m·K |
Sour-service / NACE MR0175 condition | High-temper condition for H₂S / sour oilfield service where hardness must stay ≤22 HRC per NACE MR0175 in the critical section. | 690 | 830 | 20 | 24 HRC | — |
Hot isostatic pressed | Full-density powder or post-AM HIP route giving isotropic, near-wrought properties with closed internal porosity. | 860 | 1,000 | 14 | 31 HRC | — |
Quenched and tempered | The standard pre-hardened stock condition: good strength/toughness balance and still machinable without further heat treatment. | 860 | 965 | 17 | 30 HRC | — |
Q&T core + gas/plasma nitrided case | Pick when a tough core plus a hard, low-distortion wear/fatigue-resistant surface is required (spindles, screws, cylinders). | 860 | 965 | 15 | 58 HRC | 7.8 % IACS |
laser powder-bed fusion (LPBF) 4140 powder, as-built | As-built AM condition: as-quenched martensite, high strength but low ductility and residual stress — normally tempered or HIP'd afterwards. | 950 | 1,300 | 5 | 48 HRC | — |
Medium-high strength temper | For higher-loaded shafts, gears and holders where wear resistance matters more than impact toughness. | 1,080 | 1,180 | 15 | 36 HRC | — |
High strength temper | Choose for high-stress fasteners, torsion bars and dies; machining now needs carbide tooling. | 1,280 | 1,400 | 12 | 43 HRC | — |
Low-temper, maximum strength | Near-maximum hardness for wear parts and punches; very low toughness and high hydrogen-embrittlement risk. | 1,570 | 1,720 | 9 | 50 HRC | — |
What is 4140?
4140 (42CrMo4 / 42CrMo / SCM440) is the workhorse medium-carbon chromium-molybdenum through-hardening alloy steel, supplied hot rolled, cold drawn or pre-hardened and used for shafts, gears, spindles, tooling holders, hydraulic bodies and oilfield components. Its 1 % Cr + 0.2 % Mo gives deep hardenability, high strength-to-cost ratio and good temper-embrittlement resistance, allowing 850–1700 MPa tensile strength by quench and temper. Limits are poor corrosion resistance (must be coated, plated or nitrided), preheat/post-weld heat treatment requirements for welding, and hydrogen-embrittlement / sulfide-stress-cracking sensitivity above about 30 HRC. 4140 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F). 4140 has a yield strength of 480 MPa (69.6 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 59% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
What is 4140 used for?
- CNC machined gears
- Transmission and drive shafts
- Machine tool spindles
- Tool holders and arbors
- Hydraulic cylinder bodies and manifolds
- Oilfield drill collars and subs
- Forged crankshafts
- Die holders and bolsters
4140 properties
Typical room-temperature values for 4140-HR; bars are the position among steel grades.
Physical3
4140 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F).
Mechanical16
4140 has a yield strength of 480 MPa (69.6 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 59% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4140 is rated for continuous service to 425°C (797 °F). It conducts heat at 42.6 W/m·K (24.6 BTU/hr·ft·°F), worse than 51% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
4140 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 4140 takes about 32 MJ of energy and emits 2.2 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability7
4140's machinability is good (60/100, better than 83% of steel grades); weldability fair (40/100); formability fair (40/100).
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 steel family
Yield strength against density for every steel grade FabDigit runs. 4140 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4140
Is 4140 easy to machine?
Machines best at 187–235 HB (annealed/HR) or up to 32 HRC pre-hardened; use rigid setups, carbide inserts, ~120–180 m/min in annealed stock and flood coolant — above 40 HRC treat as tool steel or grind.
Can 4140 be welded?
Weldable with low-hydrogen consumables but requires 200–320 °C preheat, controlled interpass and immediate PWHT/temper at 590–675 °C to avoid HAZ martensite cracking; best welded in the annealed/normalized state and re-heat-treated after.
Can 4140 be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold forming only in the annealed condition and with generous bend radii — hardened conditions are essentially non-formable.
Manufacturability
The process limits FabDigit's quote engine applies to 4140. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Good60 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 160 / 190 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 4.5× diameter |
| Best surface (machined / polished) | Ra 1.6 / 0.8 µm |
| Hardenable after machining | Yes |
Sheet metal
| Formability | Good40 / 100 |
|---|---|
| Weldability | Good40 / 100 |
4140 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 |
|---|---|---|
| C42CrMo4 EN: 0.38–0.45 | 0.38 – 0.43 | 0.4 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.75 – 1 | 0.87 |
| P | ≤ 0.04 | |
| Smax; 4140 resulfurized variants (4140H/41L40) differ | ≤ 0.04 | |
| Cr | 0.8 – 1.1 | 0.95 |
| Mo | 0.15 – 0.25 | 0.2 |
| Fe | balance |
What surface finishes work on 4140?
No natural corrosion resistance: use black oxide, manganese phosphate, zinc or hard-chrome plating, nitriding/QPQ or paint; bake after plating to relieve hydrogen embrittlement when above ~30 HRC. Takes a good mechanical polish.
Surface treatments FabDigit runs on 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
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 4140 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does 4140 cost?
4140 is a standard-cost steel ($$), cheaper than about 62% 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.
4140 — frequently asked
What is 4140 used for?
4140 is typically used for CNC machined gears, transmission and drive shafts, machine tool spindles, tool holders and arbors, hydraulic cylinder bodies and manifolds and oilfield drill collars and subs. In short: versatile alloy; tough.
What is the yield strength of 4140?
4140 has a typical yield strength of 480 MPa (69.6 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 59% of steel grades. Strength varies by condition: see the 14 listed tempers.
Is 4140 easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machines best at 187–235 HB (annealed/HR) or up to 32 HRC pre-hardened; use rigid setups, carbide inserts, ~120–180 m/min in annealed stock and flood coolant — above 40 HRC treat as tool steel or grind.
Can 4140 be welded?
With care — weldability is rated fair (40/100). Weldable with low-hydrogen consumables but requires 200–320 °C preheat, controlled interpass and immediate PWHT/temper at 590–675 °C to avoid HAZ martensite cracking; best welded in the annealed/normalized state and re-heat-treated after.
What surface finishes work on 4140?
No natural corrosion resistance: use black oxide, manganese phosphate, zinc or hard-chrome plating, nitriding/QPQ or paint; bake after plating to relieve hydrogen embrittlement when above ~30 HRC. Takes a good mechanical polish.
Can 4140 be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold forming only in the annealed condition and with generous bend radii — hardened conditions are essentially non-formable.
What is the maximum service temperature of 4140?
4140 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.
What is the difference between 4140-HR and 4140-HIP?
HR is the default condition — cheapest general stock for parts that will be machined and then heat treated by the user. HIP: full-density powder or post-AM HIP route giving isotropic, near-wrought properties with closed internal porosity. Yield strength is 480 MPa in HR versus 860 MPa in HIP.
How much does 4140 cost?
4140 is a standard-cost steel ($$), cheaper than about 62% 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 4140?
Yes — 4140 is available for CNC machining, sheet metal and casting & forging with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM International (2020)
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- EN 10083-3 — Heat treatable steels: 42CrMo4 (1.7225) — CEN (2006)
- GB/T 3077 — (42CrMo) — SAC (2015)
- JIS G4053 — Low-alloyed structural steels (SCM440) — JSA (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- Machinery's Handbook, 31st ed. — Industrial Press (2020)
- NACE MR0175 / ISO 15156 — Materials for H2S-containing environments — NACE/ISO (2015)
- Low-alloy Cr-Mo steel bar datasheets — Böhler / Ovako / Nucor supplier data (2023)
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.