42CrMo4
Chromium-molybdenum machine steel: quenched and tempered Rp0.2 900 MPa and Rm 1 100–1 300 MPa up to 16 mm, still 500 MPa at 250 mm.
The workhorse for highly loaded shafts, axles, gears, connecting rods and high-strength bolts. Molybdenum lets it harden through much larger sections than C45. Welds only with preheat and care: the heat-affected zone hardens.
- Yield strength Re / Rp0.2
- ≥ 900 MPa3guaranteed minimum · quenched and tempered (+QT)
- Tensile strength Rm
- 1 100–1 300 MPa3guaranteed range · quenched and tempered (+QT)
- Elongation after fracture A
- ≥ 10 %2guaranteed minimum · quenched and tempered (+QT)
- Brinell hardness HB
- ≤ 255 HB2guaranteed maximum · treated for cold shearability (+S)
- ≤ 241 HB2guaranteed maximum · soft annealed (+A)
How we know these values · 40 values from 3 sources
- Confirmed
- 2
- Corroborated
- 24
- Single source
- 14
- Disagreements explained
- 1
- Click any value under “All values” to see the sources that state it, with dates.
- 1 disagreement between sources, each explained under its value.
- How we rate evidence
What to watch
- Guaranteed yield strength depends on thickness: 900 MPa for ≤ 16 mm, down to 500 MPa for 160–250 mm.
- Sources disagree on impact energy (charpy v); the reason is given under the value.
All values
- Identity and composition 7
- Mechanical 28
- Physical 1
- Thermal 3
- Electrical and magnetic 1
- Chemical and durability not yet
Mechanical
Elastic
Modulus of elasticity E
Young's modulus for design.
| Condition | Value | Evidence |
|---|---|---|
| ≈ 212 000MPatypical | Single source |
Strength
Yield strength Re / Rp0.2
Minimum yield strength, or 0.2 % proof strength when there is no marked yield point.
| Condition | Value | Evidence |
|---|---|---|
| ≥ 900MPa | Confirmed | |
| ≥ 750MPa | Corroborated | |
| ≥ 650MPa | Corroborated | |
| ≥ 550MPa | Corroborated | |
| ≥ 500MPa | Corroborated |
Tensile strength Rm
Ultimate tensile strength. Product standards give a range or a minimum.
| Condition | Value | Evidence |
|---|---|---|
| 1 100–1 300MPa | Confirmed | |
| 1 000–1 200MPa | Corroborated | |
| 900–1 100MPa | Corroborated | |
| 800–950MPa | Corroborated | |
| 750–900MPa | Corroborated |
Brinell hardness HB
Resistance to indentation by a hard ball; for castings and bearings.
| Condition | Value | Evidence |
|---|---|---|
| ≤ 255HB | Corroborated | |
| ≤ 241HB | Corroborated |
Ductility
Elongation after fracture A
Minimum elongation; depends on gauge length and test direction.
| Condition | Value | Evidence |
|---|---|---|
| ≥ 10% | Corroborated | |
| ≥ 11% | Corroborated | |
| ≥ 12% | Corroborated | |
| ≥ 13% | Corroborated | |
| ≥ 14% | Corroborated |
Reduction of area Z
Minimum necking at fracture of a tensile test piece, relative to its cross-section.
| Condition | Value | Evidence |
|---|---|---|
| ≥ 40% | Corroborated | |
| ≥ 45% | Corroborated | |
| ≥ 50% | Corroborated | |
| ≥ 50% | Corroborated | |
| ≥ 55% | Corroborated |
Toughness
Impact energy (Charpy V) KV
Minimum absorbed energy at the stated test temperature.
| Condition | Value | Evidence |
|---|---|---|
| ≥ 30J | Single source1 | |
| ≥ 35J | Corroborated | |
| ≥ 35J | Corroborated | |
| ≥ 35J | Corroborated | |
| ≥ 35J | Corroborated |
Physical
Density ρ
Mass per unit volume.
| Condition | Value | Evidence |
|---|---|---|
| 7 850kg/m³ | Single source |
Thermal
Coefficient of thermal expansion α
Linear, near room temperature.
| Condition | Value | Evidence |
|---|---|---|
| ≈ 12.1×10⁻⁶ /Ktypical | Single source |
Specific heat capacity cp
Heat needed to warm 1 kg by 1 K.
| Condition | Value | Evidence |
|---|---|---|
| ≈ 461J/(kg·K)typical | Single source |
Thermal conductivity λ
Heat flow through 1 m of material per kelvin of temperature difference.
| Condition | Value | Evidence |
|---|---|---|
| ≈ 45.1W/(m·K)typical | Single source |
Electrical and magnetic
Electrical resistivity ρe
Resistance of a 1 m cube between opposite faces.
| Condition | Value | Evidence |
|---|---|---|
| ≈ 2.31 × 10⁻⁷Ω·mtypical | Single source |
Chemical composition
Show on the periodic tableCast analysis, %
| Element | Applies to | Range % | Evidence |
|---|---|---|---|
| C | all thicknesses | 0.38–0.45 | Single source |
| Si | all thicknesses | 0.40 | Single source |
| Mn | all thicknesses | 0.6–0.9 | Single source |
| P | all thicknesses | 0.025 | Single source |
| S | all thicknesses | 0.035 | Single source |
| Cr | all thicknesses | 0.9–1.2 | Single source |
| Mo | all thicknesses | 0.15–0.3 | Single source |
42CrMoS4 (1.7227) has S 0.020–0.040 % for machining. Saarstahl's typical analysis: C 0.42, Cr 1.10, Mo 0.22.
Compare side by side
With any other gradeSources here are public pages that reproduce EN 10083-3. For design and acceptance, the standard edition named in your specification and the inspection certificate (EN 10204 3.1) of the delivered product take precedence. Design factors are recommended values; your National Annex may set others.