Chrome Moly EN24 Alloy Steel Bars

Product Description

EN24 (defined under the British standard BS 970 as 817M40) is a highly popular, high-tensile alloy steel. While often grouped broadly under "chrome-moly" due to its chromium and molybdenum content, it is more accurately classified as a Nickel-Chromium-Molybdenum (Ni-Cr-Mo) steel.

The addition of nickel gives it significantly better through-hardening properties and core toughness compared to standard chrome-moly grades like 4140 (EN19), making it the go-to choice for heavy-duty components operating under severe stress.

Global Equivalents

When cross-referencing across international material tracking systems, EN24 lines up closely with these major specifications:

• USA (AISI/SAE): 4340

• Germany (DIN / WNr): 34CrNiMo6 / 1.6582

• Europe (EN): 34CrNiMo6 or 817M40

• Japan (JIS): SNCM439

• France (AFNOR): 35NCD6

Chemical Composition (Typical %)

The balanced chemistry of EN24 allows it to retain high shock resistance and ductility even at high tensile strengths.

Mechanical Properties (Condition T)

EN24 bars are most commonly supplied in the "Condition T" heat-treated state (hardened and tempered to a tensile range of 850–1000 MPa), offering an optimal blend of strength and machinability.

• Tensile Strength: 850 – 1000 MPa (N/mm²)

• Yield Strength: ≥ 650 MPa

• Elongation: ≥ 13%

• Impact Strength (Izod): ≥ 47 J

• Hardness: 248 – 302 HB

Key Technical Characteristics

• Through-Hardening: Due to the nickel content, large section sizes can be hardened uniformly to the core via oil quenching, avoiding the soft centers common in lower alloy steels.

• Machinability: In its pre-hardened state (Condition T), it machines relatively well with standard carbide tooling.

• Nitridation/Induction: Excellent response to surface hardening techniques if you need an incredibly wear-resistant skin (reaching up to 60-65 HRC) while maintaining a tough, flexible core.

Common Industrial Applications

Because it handles combinations of high load, wear, and shock beautifully, you will typically find EN24 bars used for:

• High-torque crankshafts, axles, and steering knuckles.

• Heavy-duty power transmission gears, pinions, and splined shafts.

• Structural bolts, specialized high-tensile fasteners, and heavy clamping hardware.

• Drill stems and retaining blocks for oil and gas tooling.