Steel E4340
GOST E4340
E4340 is the electric-furnace, low phosphorus and sulfur version of 4340 Ni-Cr-Mo medium-carbon alloy steel, often vacuum-arc remelted (VAR, AMS 6414) for aerospace load-bearing parts.
Values for the HR condition
E4340 tempers and conditions
E4340 is supplied in 14 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
- Annealed
- CR
- HR
- N&T
- CD
- Normalized
- Q&T 28-32 HRC
- VAR
- Q&T
- Q&T 32-36 HRC
- Q&T 36-40 HRC
- Q&T 40-44 HRC
- Q&T 44-48 HRC
- Q&T 50-53 HRC
Compare all 14 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full/spheroidize annealed (≈ 800 °C, slow cool) | Softest supply condition for machining, deep hole drilling and cold forming before final Q&T. | 470 | 745 | 22 | 217 HB | 45 W/m·K |
Cold rolled | Thin sheet/strip supply form for blanking and forming before hardening. | 600 | 800 | 15 | 21 HRC | 7 % IACS |
HRDefault Hot rolled | Standard mill stock for re-heat-treating; not for final load-bearing use in as-rolled state. | 620 | 950 | 16 | 30 HRC | — |
Normalized and tempered | Machining-friendly pre-treatment for large aerospace bar/forgings that will be finish heat treated later. | 700 | 930 | 18 | 29 HRC | 7 % IACS |
Cold drawn | Close-tolerance bright bar for shafts and parts machined without further heat treatment. | 720 | 860 | 13 | 25 HRC | — |
870 °C, air cooled | Grain-refining condition used before machining/hardening; high strength but low ductility for a deep-hardening steel. | 862 | 1,279 | 12 | 39 HRC | — |
Tempered ≈620 °C | Toughest Q&T level; for weld-repaired or impact-loaded parts and thick sections. | 880 | 1,000 | 19 | 30 HRC | — |
Vacuum arc remelted premium aircraft quality (AMS 6414), supplied… | Choose when cleanliness-driven fatigue life and transverse toughness are required (landing gear, rotor shafts). | 950 | 1,100 | 15 | 35 HRC | 7 % IACS |
Quenched and tempered | General service condition for shafts, gears and structural parts needing balanced strength and toughness. | 1,035 | 1,150 | 17 | 34 HRC | — |
Tempered ≈580 °C | Most common commercial hardness band for shafts, couplings and machinery components. | 1,035 | 1,150 | 17 | 34 HRC | — |
Tempered ≈500 °C | Higher-strength band for gears, torsion bars and highly loaded shafting. | 1,160 | 1,270 | 15 | 38 HRC | — |
Tempered ≈450 °C | Used for high-strength fasteners, tooling and aircraft fittings needing wear plus strength. | 1,270 | 1,400 | 14 | 42 HRC | — |
Tempered ≈370 °C | Very high strength for landing-gear-class parts; notch sensitivity and hydrogen embrittlement risk rise sharply. | 1,400 | 1,560 | 13 | 46 HRC | — |
Tempered ≈205–260 °C | Maximum-strength aerospace condition (VAR stock only); use where mass is critical and fracture control is engineered. | 1,720 | 1,900 | 11 | 52 HRC | — |
What is E4340?
E4340 is the electric-furnace, low phosphorus and sulfur version of 4340 Ni-Cr-Mo medium-carbon alloy steel, often vacuum-arc remelted (VAR, AMS 6414) for aerospace load-bearing parts. Deep hardenability allows tempering anywhere in the 1000–1900 MPa tensile range with a good strength-to-toughness balance; stock covers hot-rolled, cold-drawn, annealed, normalized and Q&T bar from 28–32 up to 50–53 HRC. Limits are poor corrosion resistance, welding that needs preheat and post-weld temper, and notch sensitivity plus hydrogen-embrittlement risk at high strength. Standard 4340 costs less where melt cleanliness is not specified. E4340 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,427°C (2,601 °F). E4340 has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 78% of steel grades. Elongation at break is 16% and the elastic modulus is 205 GPa (29.7 Msi).
What is E4340 used for?
- Aircraft landing gear components
- Power-transmission shafts
- Gears and pinions
- High-strength bolts and studs
- Torsion bars
- Forging die holders
- Crankshafts
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High strength — 620 MPa (89.9 ksi), better than 78% of steel grades
E4340 properties
Typical room-temperature values for E4340-HR; bars are the position among steel grades.
Physical3
E4340 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,427°C (2,601 °F).
Mechanical16
E4340 has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 78% of steel grades. Elongation at break is 16% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
E4340 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 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
E4340 conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of E4340 takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 40%.
Manufacturability8
E4340's machinability is fair (42/100, worse than 73% of steel grades); weldability poor (30/100); formability fair (35/100).
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. E4340 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with E4340
Is E4340 easy to machine?
Machine in annealed or ≤32 HRC condition with rigid setups, carbide tooling and flood coolant; above 45 HRC use CBN/ceramic or grinding.
Can E4340 be welded?
Weldable only with preheat 200–320 °C, low-hydrogen or matching filler, and immediate post-weld temper below the part's tempering temperature; avoid welding at high-strength tempers.
Can E4340 be formed, bent or molded?
Cold form only in the annealed state with generous radii; hot forge 1050–1200 °C, finish above 900 °C, then normalize before hardening.
Manufacturability
The process limits FabDigit applies to E4340. Every E4340 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better42 / 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 | Fair35 / 100 |
|---|---|
| Weldability | Better30 / 100 |
E4340 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 | 0.38 – 0.43 | 0.4 |
| Mn | 0.65 – 0.85 | 0.75 |
| Si | 0.15 – 0.35 | 0.25 |
| Ni | 1.65 – 2 | 1.8 |
| Cr | 0.7 – 0.9 | 0.8 |
| Mo | 0.2 – 0.3 | 0.25 |
| PE-prefix electric-furnace limit; AMS 6414 VAR restricts to 0.010 max | ≤ 0.03 | 0.01 |
| SAMS 6414 VAR restricts to 0.010 max | ≤ 0.03 | 0.01 |
| Curesidual | ≤ 0.35 | 0.1 |
| Fe | balance |
What surface finishes work on E4340?
No anodizing (ferrous): use Cd or Zn-Ni plating, hard chrome, black oxide, phosphate or shot peening; bake 190 °C ≥23 h after plating to relieve hydrogen at strengths above ~1240 MPa.
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
How much does E4340 cost?
E4340 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.
E4340 — frequently asked
What is E4340 used for?
E4340 is typically used for aircraft landing gear components, power-transmission shafts, gears and pinions, high-strength bolts and studs, torsion bars and forging die holders. In short: aerospace high-strength bar.
What is the yield strength of E4340?
E4340 has a typical yield strength of 620 MPa (89.9 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 78% of steel grades. Strength varies by condition: see the 14 listed tempers.
Is E4340 easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Machine in annealed or ≤32 HRC condition with rigid setups, carbide tooling and flood coolant; above 45 HRC use CBN/ceramic or grinding.
Can E4340 be welded?
Not readily — weldability is rated poor (30/100). Weldable only with preheat 200–320 °C, low-hydrogen or matching filler, and immediate post-weld temper below the part's tempering temperature; avoid welding at high-strength tempers.
What surface finishes work on E4340?
No anodizing (ferrous): use Cd or Zn-Ni plating, hard chrome, black oxide, phosphate or shot peening; bake 190 °C ≥23 h after plating to relieve hydrogen at strengths above ~1240 MPa.
Can E4340 be formed, bent or molded?
Cold form only in the annealed state with generous radii; hot forge 1050–1200 °C, finish above 900 °C, then normalize before hardening.
What is the maximum service temperature of E4340?
E4340 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 E4340-HR and E4340-VAR?
HR is the default condition — standard mill stock for re-heat-treating; not for final load-bearing use in as-rolled state. VAR: choose when cleanliness-driven fatigue life and transverse toughness are required (landing gear, rotor shafts). Yield strength is 620 MPa in HR versus 950 MPa in VAR.
How much does E4340 cost?
E4340 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 E4340?
Yes — E4340 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
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- AMS 6414 — Steel Bars, Forgings, Tubing 0.80Cr-1.8Ni-0.25Mo, Consumable Electrode Vacuum Melted — SAE International (2019)
- AMS 6415 — Steel Bars, Forgings and Tubing 4340 — SAE International (2019)
- GB/T 3077 (40CrNiMoA) — SAC (2015)
- 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)
- MMPDS-17 (4340 and 4340 VAR allowables) — Battelle/FAA (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.