W.Nr. 40NiCrMo6 Chrome Moly Alloy Steel Bars

Product Description

W.Nr. 1.6565 (standardized across Europe as 40NiCrMo6 under EN 10083-3) is the exact Werkstoffnummer designation for the premium Nickel-Chromium-Molybdenum alloy steel we discussed.

When you order bar stock under the formal W.Nr. 40NiCrMo6 designation, you are sourcing a high-end, triple-alloy engineering steel designed for extreme stress. Because it contains significant amounts of Nickel, Chromium, and Molybdenum working together, it eliminates the "soft core" problem (slack quenching) that compromises large-diameter bars made from simpler chrome-moly grades like 42CrMo4 (1.7225).

1. Dimensional Hardenability (The True Value of 40NiCrMo6)

The biggest trap when buying alloy steel bars is assuming a material's strength properties apply uniformly to all sizes. Standard chrome-moly steels drop in core strength drastically as the bar diameter grows past 50 mm.

W.Nr. 40NiCrMo6 solves this. The addition of Carbon (C)

3. Standard Delivery Conditions

When ordering W.Nr. 40NiCrMo6 bars, they are typically specified in one of two major supply conditions depending on your processing pipeline:

Soft Annealed (+A)

• Hardness: $\le$ 260 HBW (Brinell)

• When to use: Choose this if you are performing heavy material removal, such as deep gundrilling, cutting internal splines, or machining complex gear teeth. It ensures maximum tool life and minimal residual internal stress before you send it to final heat treatment.

Quenched & Tempered (+QT)

• Hardness: Typically ranges between 280 and 340 HBW ($\sim$ 29 to 36 HRC).

• When to use: Choose this if you want to machine your components directly to final dimensions and put them straight into service without risking the dimensional warping or scaling that can occur during post-machining heat treatment.

4. Key Cross-References for Global Procurement

If you are coordinating manufacturing across different international facilities, W.Nr. 40NiCrMo6 maps directly to these major global standards:

• USA: AISI 4340 / SAE 4340

• Japan: JIS SNCM439

• United Kingdom: BS 817M40 / EN24

• China: GB 40CrNiMoA

• Russia: GOST 40KhN2MA (40ХН2МА)

5. Critical Fabrication Guidelines

⚠️ Welding & Thermal Processing Warning

Due to its high alloy content and carbon equivalent, W.Nr. 40NiCrMo6 is highly susceptible to cold cracking caused by hydrogen entrapment.

• Welding: Structural welding should be avoided. If it is absolutely mandatory for a repair or build-up, you must preheat the bar to 250°C–300°C, use strictly controlled low-hydrogen electrodes, and perform immediate Post-Weld Heat Treatment (PWHT) / stress relief.

• Flame/Laser Cutting: If bars are thermally cut rather than sawed, the cut edges will instantly air-harden into brittle martensite. These edges must be ground down or locally annealed before any subsequent machining to protect your cutting tools.