Steel 4340-CR (Cold rolled)
Supply condition
AISI/SAE 4340 · UNS G43400 · EN 1.6582, 34CrNiMo6 · JIS SNCM439 · GB 40CrNiMoA
Thin sheet/strip form for blanked parts that will be heat treated after forming.
Values for the CR condition
Other 4340 tempers and conditions
4340 is listed in 13 conditions; see the grade overview at 4340.
- Annealed
- HR
- CR
- CD
- Normalized
- Q&T 28-32 HRC
- Q&T
- Q&T 32-36 HRC
- Q&T+Nitrided
- Q&T 36-40 HRC
- Q&T 40-44 HRC
- Q&T 46-50 HRC
- Q&T 50-54 HRC
Compare all 13 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full/spheroidize annealed (≈815 °C, slow cool) | Softest and most machinable condition; used as the supply state for parts that will be finish heat treated. | 470 | 745 | 22 | 217 HB | 45 W/m·K |
HRDefault Hot rolled | Cheapest stock form for parts that will be rough-machined and then heat treated by the customer. | 620 | 950 | 18 | 29 HRC | — |
CRThis page Cold rolled | Thin sheet/strip form for blanked parts that will be heat treated after forming. | 620 | 800 | 15 | 22 HRC | 7 % IACS |
Cold drawn | Choose for close-tolerance, bright-finish shafting used without further heat treatment. | 830 | 965 | 12 | 29 HRC | 44 W/m·K |
870 °C, air cooled | Uniform fine-grained structure with high as-cooled strength; usually a preparatory step before machining and Q&T. | 860 | 1,280 | 12 | 39 HRC | — |
Tempered ~600 °C | Toughest useful Q&T level; for shafts and machine parts needing impact resistance and easy finishing. | 860 | 1,020 | 20 | 30 HRC | — |
Quenched and tempered | Standard commercial heat-treated stock ("4340HT"): high strength with good toughness and still machinable. | 880 | 1,030 | 18 | 31 HRC | 43 W/m·K |
Tempered ~565 °C | Balanced strength/toughness for gears, couplings and heavy-duty shafting. | 1,010 | 1,130 | 18 | 34 HRC | — |
Q&T + gas/ion nitrided case | Pick when a Q&T core (typically 32–36 HRC) needs a hard, wear- and fatigue-resistant 0.2–0.5 mm case without distortion. | 1,010 | 1,130 | 15 | 58 HRC | 7 % IACS |
Tempered ~525 °C | Higher strength for torsion bars, tool holders and mid-strength aerospace fittings still needing decent toughness. | 1,160 | 1,240 | 17 | 38 HRC | — |
Tempered ~450 °C | High-strength condition for aircraft structural fittings and highly stressed pins; machining requires carbide tooling. | 1,360 | 1,500 | 14 | 42 HRC | — |
Tempered ~315 °C | Very high strength for landing-gear and heavy-section tooling; toughness and hydrogen tolerance drop sharply. | 1,620 | 1,760 | 12 | 48 HRC | — |
Tempered ~205 °C | Maximum-strength condition; only for wear/strength-critical parts where low toughness and embrittlement risk are acceptable. | 1,860 | 1,980 | 11 | 52 HRC | — |
What is 4340-CR?
4340-CR is 4340 supplied in the CR condition — thin sheet/strip form for blanked parts that will be heat treated after forming. 4340-CR has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 78% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi). 4340-CR 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). HR is the default condition FabDigit quotes; CR is available on request or by drawing note.
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
- Tough — resists crack growth — 115 MPa·√m (104.7 ksi·√in), better than 77% of steel grades
4340-CR properties
Typical room-temperature values for 4340-CR; 23 are specific to this condition. Other listed values are 4340 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4340-CR 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).
Mechanical17
4340-CR has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 78% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4340-CR is rated for continuous service to 400°C (752 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 66% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
4340-CR conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 4340-CR takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability7
4340-CR's machinability is fair (50/100, worse than 53% of steel grades); weldability fair (38/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4340-CR
Is 4340 easy to machine?
Machine in the annealed or ≤34 HRC condition with rigid setups; above 40 HRC use coated carbide/CBN, low speeds and heavy positive feed, and finish-grind critical surfaces.
Can 4340 be welded?
Weldable only with 250–350 °C preheat, low-hydrogen or matching Ni-Cr-Mo filler and immediate post-weld temper below the part's tempering temperature; avoid welding fully hardened parts.
Can 4340 be formed, bent or molded?
Hot forge/roll at 1050–1200 °C and always normalize afterwards; cold bending is limited to the annealed state with generous radii.
What surface finishes work on 4340?
Requires protection — zinc/cadmium or Cr plating, phosphate + oil, or paint; bake at 190 °C after plating to relieve hydrogen, and shot-peen highly loaded fillets to restore fatigue life.
4340 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 |
|---|---|---|
| CASTM A29 / SAE J404 | 0.38 – 0.43 | 0.4 |
| Mn | 0.6 – 0.8 | 0.7 |
| 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 |
| Pmax; aircraft quality (AMS 6414) ≤0.010 | ≤ 0.04 | — |
| Smax; aircraft quality ≤0.010 | ≤ 0.04 | — |
| Fe | balance | — |
4340-CR — frequently asked
What is 4340-CR used for?
4340-CR is typically used for landing gear components, drive shafts, heavy-duty gears, crankshafts, machine tool spindles and tool holders and arbors. In short: ultra-high fatigue strength.
What is the yield strength of 4340-CR?
4340-CR has a typical yield strength of 620 MPa (89.9 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 78% of steel grades. Strength varies by condition: see the 13 listed tempers.
Is 4340-CR easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Machine in the annealed or ≤34 HRC condition with rigid setups; above 40 HRC use coated carbide/CBN, low speeds and heavy positive feed, and finish-grind critical surfaces.
Can 4340-CR be welded?
With care — weldability is rated fair (38/100). Weldable only with 250–350 °C preheat, low-hydrogen or matching Ni-Cr-Mo filler and immediate post-weld temper below the part's tempering temperature; avoid welding fully hardened parts.
What surface finishes work on 4340-CR?
Requires protection — zinc/cadmium or Cr plating, phosphate + oil, or paint; bake at 190 °C after plating to relieve hydrogen, and shot-peen highly loaded fillets to restore fatigue life.
Can 4340-CR be formed, bent or molded?
Hot forge/roll at 1050–1200 °C and always normalize afterwards; cold bending is limited to the annealed state with generous radii.
What is the maximum service temperature of 4340-CR?
4340-CR 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 4340-HR and 4340-CD?
HR is the default condition — cheapest stock form for parts that will be rough-machined and then heat treated by the customer. CD: choose for close-tolerance, bright-finish shafting used without further heat treatment. Yield strength is 620 MPa in HR versus 830 MPa in CD.
Can FabDigit make parts in 4340-CR?
Yes — 4340-CR 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
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- AMS 6414 — Steel Bars, Forgings, Tubing 4340 (Vacuum Consumable Electrode Remelted) — SAE Aerospace (2019)
- GB/T 3077 — (40CrNiMoA) — SAC (2015)
- EN 10083-3 — 34CrNiMo6 (1.6582) — CEN (2006)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- MMPDS-2023 typical low-alloy steel data — Battelle/FAA (2023)
- Machinery's Handbook, 31st ed. (machinability ratings) — Industrial Press (2020)
- Mysteel / SMM (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.