Quick Comparison Table
| Property | EN8 | EN19 | EN24 | EN31 |
|---|---|---|---|---|
| Carbon % | 0.36–0.44 | 0.36–0.44 | 0.36–0.44 | 0.95–1.10 |
| Key Alloying | Mn | Cr + Mo | Ni + Cr + Mo | High Cr |
| Tensile (H&T) | 700–850 MPa | 850–1000 MPa | 1000–1150 MPa | Up to 2000 MPa* |
| Weldability | Fair | Poor (needs pre-heat) | Poor | Not recommended |
| Machinability | Good | Good | Moderate | Moderate (annealed) |
| Wear Resistance | Low | Medium | Medium | Excellent |
| Relative Cost | $ | $$ | $$$ | $$ |
*EN31 hardened — not a typical service tensile; hardness (HRC 60–65) is the primary metric.
EN8 — The General-Purpose Choice
EN8 is the workhorse of the alloy steel family. It's the first step up from mild steel when you need a component that will be machined, carry moderate load, and possibly be case-hardened or surface-hardened. If EN8 has enough tensile strength for your application (up to ~850 MPa normalised), it's the most cost-effective choice.
Choose EN8 for: General shafts, spindles, studs, bolts, keys, and high-volume turned components.
EN19 — The High-Tensile Step Up
EN19 adds chromium and molybdenum to achieve higher tensile strength (850–1000 MPa) and better hardenability — meaning large-diameter bars can be hardened through their full cross-section, not just at the surface. Use EN19 when EN8 isn't strong enough and you need reliable through-hardening.
Choose EN19 for: High-duty shafts, automotive axles, high-strength gears, hydraulic components, and bolting for critical joints.
EN24 — Maximum Toughness and Fatigue Resistance
EN24 adds nickel (in addition to Cr and Mo), giving it superior impact toughness and fatigue resistance on top of high tensile strength (1000–1150 MPa). It's the premium choice for components subject to shock loading, vibration, and repeated stress cycles.
Choose EN24 for: Connecting rods, heavy shafts in mining and steel mills, crane hooks, pins, and aerospace/defence structural components.
EN31 — Maximum Wear Resistance
EN31 is a bearing steel (high carbon, high chromium) — its purpose is not tensile strength but extreme hardness and wear resistance after hardening (HRC 60–65). It's used wherever rolling or sliding contact wear is the primary failure mode.
Choose EN31 for: Ball and roller bearings, cold-work dies and punches, reamers, gauges, and precision wear components.