Steel 40Cr
GB 40Cr
40Cr is the Chinese GB/T 3077 medium-carbon chromium engineering steel (close analogue of AISI/SAE 5140 and EN 41Cr4), used for shafts, gears, bolts, spindles and other quenched-and-tempered machine parts up to roughly 60–80 mm section.
Values for the HR condition
40Cr tempers and conditions
40Cr is supplied in 10 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Temper | Softest condition (≤207 HB per GB/T 3077) for deep machining, cold forming or before final hardening. | 400 | 680 | 22 | 187 HB | — |
HRDefault Hot rolled | Standard stocked as-rolled bar; buy this and heat treat after rough machining. | 430 | 720 | 16 | 210 HB | — |
Heat Treat State | Air-cooled from ~860 °C for uniform fine pearlitic structure and predictable machining before Q&T. | 500 | 800 | 18 | 20 HRC | 8 % IACS |
Cold rolled | Cold-rolled strip/sheet for stamped and formed parts that will be hardened later. | 620 | 800 | 10 | 22 HRC | 8 % IACS |
Cold drawn | Cold-drawn bright bar: tighter tolerance, better surface and free-er chip than hot rolled. | 650 | 790 | 12 | 229 HB | — |
Q&T to 28–32 HRC | Toughness-first condition for large shafts and parts still to be machined after heat treatment. | 790 | 950 | 14 | 30 HRC | — |
Quenched and tempered | Standard GB/T 3077 delivery-condition property set; the usual choice for shafts, gears and high-strength bolts. | 830 | 1,020 | 12 | 31 HRC | — |
Induction hardened | Choose when only the running surface (journal, spline, gear tooth) needs 50+ HRC wear resistance over a tough core. | 830 | 1,020 | 12 | 55 HRC | 7 % IACS |
Gas/ion nitrided (after Q&T) | Use for low-distortion wear and scuffing resistance on already-finished Q&T parts; case is thin (0.2–0.4 mm). | 830 | 1,020 | 11 | 57 HRC | 8 % IACS |
Q&T to 35–40 HRC | Higher-strength temper for gears, couplings and wear-loaded parts; toughness and machinability drop. | 1,050 | 1,200 | 10 | 38 HRC | — |
What is 40Cr?
40Cr is the Chinese GB/T 3077 medium-carbon chromium engineering steel (close analogue of AISI/SAE 5140 and EN 41Cr4), used for shafts, gears, bolts, spindles and other quenched-and-tempered machine parts up to roughly 60–80 mm section. Chromium raises hardenability and tempering resistance over plain 40 steel, giving ~980 MPa tensile with good toughness after oil quench and 500–550 °C temper, and it responds well to induction hardening and nitriding. Limits are poor corrosion resistance (needs plating/oiling), moderate weldability (preheat plus post-weld temper required), and temper-embrittlement/low toughness if tempered near 300 °C. 40Cr has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). 40Cr has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 720 MPa (104 ksi) — weaker than 51% of steel grades. Elongation at break is 16% and the elastic modulus is 211 GPa (30.6 Msi).
What is 40Cr used for?
- Drive shafts
- Industrial bolts
- Crankshafts
Limitations
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 82% of steel grades
40Cr properties
Typical room-temperature values for 40Cr-HR; bars are the position among steel grades.
Physical3
40Cr has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
40Cr has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 720 MPa (104 ksi) — weaker than 51% of steel grades. Elongation at break is 16% and the elastic modulus is 211 GPa (30.6 Msi).
Thermal6
40Cr is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.5 µm/m·K (6.94 µin/in·°F).
Electrical3
40Cr conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 40Cr takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 35%.
Manufacturability7
40Cr's machinability is good (55/100, better than 62% of steel grades); weldability fair (45/100); 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. 40Cr is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 40Cr
Is 40Cr easy to machine?
Best machined annealed or normalized at 180–230 HB with carbide tooling (~120–180 m/min); above 35 HRC switch to coated carbide/CBN and reduce feed.
Can 40Cr be welded?
Weldable with care only — preheat 200–300 °C, low-hydrogen consumables, and temper immediately after welding; avoid welding fully hardened parts.
Can 40Cr be formed, bent or molded?
Hot forge 1150–850 °C then normalize; cold bending only in the annealed condition with generous radii (≥3t).
Manufacturability
The process limits FabDigit's quote engine applies to 40Cr. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Better55 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Fair40 / 100 |
|---|---|
| Weldability | Better45 / 100 |
40Cr 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 |
|---|---|---|
| C | 0.37 – 0.44 | 0.4 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.5 – 0.8 | 0.65 |
| Cr | 0.8 – 1.1 | 0.95 |
| Niresidual | ≤ 0.3 | |
| Curesidual | ≤ 0.25 | |
| Moresidual, not intentionally added | ≤ 0.1 | |
| P0.025 max for high-grade quality | ≤ 0.04 | |
| S0.025 max for high-grade quality | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on 40Cr?
No native corrosion protection: use black oxide, manganese phosphate, zinc or hard chrome plating (bake to de-embrittle above ~1000 MPa); polishes well after Q&T.
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 40Cr in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Other
- 5140
How much does 40Cr cost?
40Cr is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
40Cr — frequently asked
What is 40Cr used for?
40Cr is typically used for drive shafts, industrial bolts and crankshafts. In short: chrome alloy machining bar.
What is the yield strength of 40Cr?
40Cr has a typical yield strength of 430 MPa (62.4 ksi) and a tensile strength of 720 MPa (104 ksi) — weaker than 51% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 40Cr easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Best machined annealed or normalized at 180–230 HB with carbide tooling (~120–180 m/min); above 35 HRC switch to coated carbide/CBN and reduce feed.
Can 40Cr be welded?
With care — weldability is rated fair (45/100). Weldable with care only — preheat 200–300 °C, low-hydrogen consumables, and temper immediately after welding; avoid welding fully hardened parts.
What surface finishes work on 40Cr?
No native corrosion protection: use black oxide, manganese phosphate, zinc or hard chrome plating (bake to de-embrittle above ~1000 MPa); polishes well after Q&T.
Can 40Cr be formed, bent or molded?
Hot forge 1150–850 °C then normalize; cold bending only in the annealed condition with generous radii (≥3t).
What is the maximum service temperature of 40Cr?
40Cr is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 40Cr-HR and 40Cr-IH?
HR is the default condition — standard stocked as-rolled bar; buy this and heat treat after rough machining. IH: choose when only the running surface (journal, spline, gear tooth) needs 50+ HRC wear resistance over a tough core. Yield strength is 430 MPa in HR versus 830 MPa in IH.
How much does 40Cr cost?
40Cr is a standard-cost steel ($$), cheaper than about 71% 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 40Cr?
Yes — 40Cr is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- GB/T 3077 Alloy structural steels (2015)
- SAE J404 Chemical Compositions of SAE Alloy Steels (5140) — SAE International (2018)
- EN 10083-3 (41Cr4 / 1.7035) — CEN (2006)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
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.