Carbon & alloy steel · EN 10083-3
34CrNiMo6 (4340) Q&T
Overview
34CrNiMo6 (4340) Q&T is a carbon/alloy engineering steel (EN 10083-3) for shafts, gears, and heat-treated machine parts.
Typical supply: Bars, forgings, plate, tube
Mechanical Properties
Young's modulus E210 GPa
Shear modulus G80.8 GPa
Yield / proof Re900 MPa
Ultimate Rm1e+3 MPa
Poisson's ratio ν0.3
Hardness330 HB
Shear strength660 MPa
Bearing strength2e+3 MPa
Thermal Properties
Thermal expansion α12 µm/(m·K)
For temperature derating, open Temperature Properties.
Physical Properties
Density ρ8e+3 kg/m³
Specific strength Sy/ρ1.15e+5 Pa·m³/kg
Specific stiffness E/ρ2.68e+7 Pa·m³/kg
Typical supply: Bars, forgings, plate, tube
Density typically ~7800–7850 kg/m³. Bar and forging forms dominate machine design.
Applications
- Shafts and axles
- Machine components under fatigue
- Gears and pinions (with heat treatment)
- High-strength fasteners and couplings
Advantages
- Higher strength and hardenability than mild structural steel
- Responds well to quench and temper for tailored properties
- Good fatigue performance when heat-treated correctly
Limitations
- Often needs heat treatment to reach published strengths
- Weldability may require preheat / post-weld heat treatment
- Corrosion resistance similar to carbon steel unless coated
Standards
- EN 10083-3
Equivalent Materials
Electrical Properties
Not published for this grade.
Chemical Composition
Not published for this grade.
Machinability
Machinability depends on condition; annealed stock machines more easily than QT.
Cost
Low-to-moderate premium over mild steel depending on alloy content.
Corrosion
Protect like carbon steel; oil, plating, or paint for service parts.
- Oil-lubricated machineryfair
- Outdoor uncoatedpoor
For allowance / life screening, open Corrosion Allowance.