Chrome Moly DIN 1.6565 Alloy Steel Bars

Product Description

DIN 1.6565 (standardized as 40NiCrMo6) is a premier, ultra-high-strength Nickel-Chromium-Molybdenum alloy steel. While frequently grouped broadly into the "Chrome Moly" family due to its chromium and molybdenum content, it is more accurately classified as a heavy-duty Ni-Cr-Mo triple-alloy steel.

When ordered in bar form (round, flat, or forged), DIN 1.6565 is the material engineers turn to when standard chrome-moly steels (like 42CrMo4 / AISI 4140) hit their performance limits—specifically regarding deep through-hardening capability and extreme shock absorption.

1. The Power of the Triple-Alloy: Why Choose 1.6565?

Compared to standard chrome-moly grades, DIN 1.6565 introduces a significant dose of Nickel ($\sim$1.40% to 2.00%). This makes a massive physical difference:

• Massive Hardenability (Through-Hardening): In standard chrome moly, large diameter bars (e.g., over 100mm) suffer from "slack quenching"—the core doesn't cool fast enough to fully harden, leaving a soft center. The nickel and molybdenum in 1.6565 delay transformation, allowing bars up to 250mm to achieve uniform, ultra-high strength from the outer skin straight to the dead center.

• Extreme Fracture Toughness: Nickel dramatically lowers the ductile-to-brittle transition temperature. This means 1.6565 bars can absorb massive, violent shock loads at freezing temperatures without fracturing.

2. Chemical Composition Breakdown

The exceptional mechanical properties of DIN 1.6565 bars are derived from this precise chemical formulation:

3. Typical Supply Conditions & Mechanical Values

Depending on your production workflow, DIN 1.6565 alloy steel bars are generally supplied in two states:

Soft Annealed State (+A)

• Hardness: $\le$ 260 HB (Brinell)

• Usage: Recommended if your components require complex CNC milling, deep drilling, or spline cutting. Machining in this state maximizes tool life and keeps residual stresses low before final heat treatment.

Quenched & Tempered State (+QT)

Most critical engineering applications purchase bars pre-treated to the Quenched and Tempered condition. The yield values remain high even across large bar diameters:

4. Key Industrial Applications

DIN 1.6565 bars are manufactured into massive, safety-critical components operating under high-stress environments:

• Aerospace & Defense: Structural landing gear assemblies, high-load bomb racks, propeller hubs, and airframe fasteners.

• Heavy Machinery & Automotive: Heavy-duty crankshafts, connection rods, highly-stressed transmission gears, pinion shafts, and steering knuckles.

• Power Transmission: Large industrial turbine rotors, primary drive shafts, and high-torque gearboxes.

5. Global Material Equivalents

When reading international blueprints or sourcing material globally, DIN 1.6565 aligns tightly with these premium grades:

• USA: AISI 4340 / SAE 4340 (The closest and most widely recognized equivalent)

• International Standards: 40NiCrMo6

• France (AFNOR): 40NCD3 / 40NCD7

• UK (BS): 817M40 (often associated with the classic EN24 capability)

• Russia (GOST): 40KhN2MA (40ХН2МА)

Welding Caution: Due to the high carbon equivalent and significant alloy content, welding DIN 1.6565 is highly restricted. If welding is mandatory, rigorous pre-heating ($\sim$ 250°C to 300°C), specialized low-hydrogen filler metals, and immediate post-weld heat treatment (PWHT) are vital to prevent hydrogen-induced cracking.