European Standard: EN 10083-3 (equivalent to German DIN standard)

US Equivalent: AISI 4340 (similar composition, slightly different performance)

Chinese Equivalent: 40CrNiMoA (GB/T 3077)

Designation Meaning:

“34” represents a carbon content of approximately 0.34% (actual range 0.30–0.38%)

“Cr/Ni/Mo” indicates the presence of Chromium, Nickel, and Molybdenum

“6” reflects the alloy content classification (medium to high range)

2. Chemical Composition (Typical Values)

C (%):0.30–0.38%

Si (%):≤0.40%

Mn (%):0.50–0.80%

Cr (%):1.30–1.70%

Ni (%):1.30–1.70%

Mo (%):0.15–0.30%

P/S (≤):0.025%

Alloy Design Characteristics:

Cr (Chromium): Enhances hardenability, corrosion resistance, and wear resistance

Ni (Nickel): Improves toughness and low-temperature performance

Mo (Molybdenum): Reduces temper brittleness and refines grain size

3. Mechanical Properties (After Quenching and Tempering)

Tensile Strength: 900–1200 MPa

Yield Strength: ≥700 MPa

Elongation: ≥12%

Impact Energy (Charpy V-notch, room temp): ≥40 J

Hardness: 280–320 HBW

4. Heat Treatment Process

Quenching and Tempering (Q&T):

Quenching: 850–880°C, oil quenching to obtain martensitic structure

Tempering: 540–680°C, adjusted according to strength requirements—higher tempering temperatures increase toughness but slightly reduce strength

Surface Treatments:

Carburizing, nitriding, or induction hardening can be applied to improve surface hardness (e.g., gear teeth requiring ≥60 HRC surface hardness).

Annealing:

Performed at around 650°C with slow cooling to soften the material for improved machinability.

5. Key Characteristics

Strength-Toughness Balance: Especially suitable for components subject to impact or alternating loads

Superior Fatigue Performance: Ideal for cyclic stress applications like drive shafts and crankshafts

Excellent Low-Temperature Properties: Nickel content ensures good toughness even at –40°C

Limited Weldability: Preheating (200–300°C) and low-hydrogen electrodes are required for welding.

6. Typical Applications

Heavy-duty gears (wind turbine gearboxes, marine transmissions)

Aircraft landing gears, engine shafts

Oil drilling rods, hydraulic piston rods

Mold cores, high-strength bolts (e.g., for wind turbine applications)

7. Comparison with Other Materials

（1）34CrNiMo6

Carbon Content: Medium (0.34%)

Toughness: Superior (due to high Ni)

Cost: Higher

Application: Extreme loads

（2）42CrMo4 (Similar Grade)

Carbon Content: Medium-high (0.42%)

Toughness: Moderate

Cost: Lower

Application: General heavy-duty use

（3）AISI 4340

Carbon Content: Similar (0.38–0.43%)

Toughness: Slightly lower

Cost: High (in US market)

Application: Aerospace/Military

8. Considerations

Machining: Stress-relief annealing is recommended after rough machining

Corrosive Environments: Surface chrome plating or protective coatings are advised

Alternative Choice: For budget-sensitive projects with slightly lower requirements, 30CrNiMo8 can be considered for higher strength applications.

9. Conclusion

With its remarkable balance of strength and toughness, excellent hardenability, outstanding fatigue resistance, and reliable low-temperature performance, 34CrNiMo6 is the material of choice for various high-load, long-life critical components. By applying scientific heat treatment processes, precise machining control, and necessary surface protection, its full material potential can be realized, ensuring long-term safety and reliability under extreme service conditions.

10. About Suzhou Bolaibao Metal

Suzhou Bolaibao Metal specializes in providing high-performance alloy steels, non-ferrous metals, and specialty material solutions to global manufacturing industries. We serve aerospace, energy, automotive, mold-making, and heavy machinery sectors with dedication to:

✔ Professional material selection advice and technical support
✔ Strict quality control and international standards compliance
✔ Flexible supply of forgings, bars, plates, and precision machined parts
✔ Responsive service to boost customer competitiveness

Feel free to contact us for technical support, product information, or tailored solutions.

Website: www.blbszmetal.com
Email: sale@bolaibao1.com

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