Grade Designations.
| BS EN 10083-3:2006 | 42CrMo4 / 1.7225 |
| BS 970:1991 (withdrawn) | 708M40 / 709M40 |
| AISI/SAE | 4140 / 4142 |
| DIN | 42CrMo4 / 1.7225 |
| JIS | SCM440 |
Parkside also stocks the higher-molybdenum EN19 variant 709M40 (0.25–0.35% Mo) for deeper hardenability in larger sections. The two grades are identical apart from molybdenum — see 708M40 vs 709M40.
Availability & Supply Condition.
Bright Rounds: 8–100mm | Black Rounds: 25–500mm | T-condition (Q+T): 25–150mm selected sizes
Supply condition: Bright Drawn, Hot Rolled Black, or Quenched & Tempered (T condition). Normalised or annealed also available.
Cut to length from 1 piece — −0/+2mm standard tolerance — 2–3 day turnaround — Cutting service details ›
Chemical Analysis.
Values shown as percentages by weight (% wt). Values are ranges unless stated as maxima.
| Designation | C | Si | Mn | P max | S max | Cr | Mo |
|---|---|---|---|---|---|---|---|
| 708M40 | 0.36–0.44 | 0.10–0.35 | 0.70–1.00 | 0.035 | 0.040 | 0.90–1.20 | 0.15–0.25 |
| 42CrMo4 | 0.38–0.45 | 0.17–0.37 | 0.60–0.90 | 0.035 | 0.035 | 0.90–1.20 | 0.15–0.30 |
For full chemical analysis with heat number, request an EN 10204 3.1 material test certificate when ordering — available on all alloy grades. Certificate types explained ›
Mechanical Properties.
Values shown for standard supply condition. Properties vary by section size and heat treatment condition.
| Condition | Size (mm) | Tensile Rm (N/mm²) | Yield Re (N/mm²) | A% min | HB approx |
|---|---|---|---|---|---|
| H&T (T) | ≤16 / >16–40 / >40–63 / >63–100 | 1000–1200 / 900–1100 / 800–1000 / 750–950 | ≥800 / ≥650 / ≥550 / ≥500 | 10 / 11 / 12 / 13 | 295–350 |
| Normalised | All | ~850 | ~550 | ~14 | ~248 |
Hardness values: see our hardness conversion table to convert between HRC, HB, HV and tensile strength.
Typical Applications.
- High-tensile shafts and axles
- Gears and pinions (medium to high duty)
- Spindles and crankshafts
- High-tensile bolts and studs
- Oil and gas drilling components
- Automotive driveline and transmission
- Hydraulic and pneumatic cylinders
Key Benefits.
- Excellent hardenability — through-hardening in sections to ~65mm
- High tensile and yield strength after Q+T
- Good wear resistance and fatigue strength
- No nickel content — more cost-effective than EN24
- Widely stocked in comprehensive size range
- Recognised globally as 42CrMo4 / AISI 4140
Remarks & Guidance.
Preheat to 200–300°C before welding. Post-weld stress relief at 600–650°C strongly recommended for stressed components. Avoid welding in T (Q+T) condition without specialist procedure. Hardening: oil quench from 840–870°C. Tempering: 550–660°C to achieve required tensile range. Higher tempering temperature gives better toughness at reduced strength.
Relevant Heat Treatment Processes.
This grade responds to the following heat treatment processes. Click any card for temperatures, cooling methods and expected hardness values.
Normalising refines grain structure and relieves stress after forging or machining.
This grade responds to quench hardening — oil or water quench from austenitising temperature.
Temper after hardening to achieve the required tensile range and reduce brittleness.
