40NiMoCr10-4 Alloy Steel Bar 40NiMoCr10-4 Round Bars & Rods

Product Description

40NiMoCr10-4 is an elite, high-tensile, ultra-high-hardenability nickel-chromium-molybdenum alloy steel.

Technically grouped as a 2.5% Nickel-Cr-Mo engineering grade, it is closely related to the 40NiMoCr10-5 (1.6745) standard. In global procurement networks, this specific alloy composition is most famously recognized under the legacy British aerospace designation BS 970 EN26 (and its modern equivalent 826M40).

Because of its heavy concentration of nickel and molybdenum, 40NiMoCr10-4 is engineered to combat temper brittleness and achieve deep, completely uniform through-hardening in massive cross-sections (up to 6 inches or $150text{ mm}$ thick) where other high-strength steels like AISI 4140 or 4340 might drop in core strength.

Chemical Composition (%)

The micro-architecture of this alloy utilizes a high nickel concentration to maximize core impact toughness, balanced by chromium and molybdenum to achieve elevated surface hardness and fatigue resistance.

Element	Min (%)	Max (%)
Carbon (C)	0.36	0.44
Nickel (Ni)	2.30	2.80
Molybdenum (Mo)	0.45	0.65
Chromium (Cr)	0.50	0.80
Manganese (Mn)	0.45	0.70
Silicon (Si)	0.10	0.40
Phosphorus (P)		0.035
Sulfur (S)		0.035

International Cross-Reference & Equivalents

When cross-referencing design documents or engineering bills of materials, 40NiMoCr10-4 matches or tightly substitutes for:

• British Standards (UK): BS S98, BS S99,EN26,826M40

• German / WNr Designation: 40NiMoCr10-4 / 1.6745 (often designated as 40NiMoCr10-5 depending on historical standard updates)

• Australian Standard: AS 1444-1996 X9940

• USA / AISI: Heavily modified AISI 4340 variant (but with higher Nickel and Molybdenum for superior deep section strength).

Mechanical Properties (Typical in Quenched & Tempered Condition)

When supplied pre-hardened and tempered (+QT), 40NiMoCr10-4 displays extreme mechanical robustness:

• Tensile Strength ($R_m$):$1000 - 1250 text{ MPa}$ (Can be heat-treated to exceed $1400text{ MPa}$ for specific aerospace limits)

• Yield Strength ($R_e$):$ge 725 - 900 text{ MPa}$

• Elongation ($A_5$):$ge 12%$

• Typical Hardness Range:270 340 HB (Brinell) or roughly 31 38 HRC (Rockwell C).

• Low-Temperature Integrity: Maintains high structural notch toughness and ductility in freezing environments or deep sub-sea applications.

  High-Stress Applications

Because of its exceptional load-bearing stability and fatigue strength under cyclic twist and vibration, 40NiMoCr10-4 round bars are selected for high-integrity mechanical components:

• Heavy Power Transmission: High-torque turbine shafts, drive pinions, main power axes, and high-vibration motor spindles.

• Aerospace & Defense: Structural airframe landing gear rods, engine mounts, high-tensile aerospace struts, and pressure-retaining housings.

• Oil & Gas / Drilling: Extra-heavy duty hydraulic shafts, subsea valve bodies, high-pressure tool holders, and deep-hole drilling rods.

• Premium Fasteners: Industrial 12-point flange bolts, heavy structural tie rods, and specialized high-torque double-bolted clamping systems.

Machining & Tooling Tips for Shop Production

• Machinability State: If your project involves intricate, heavy stock removal (like gun-drilling or fine milling), it is highly recommended to source the bars in the Soft Annealed (+A) condition ($le 250text{ HB}$). If purchased in the Quenched and Tempered (+QT) state, ensure your CNC setup utilizes rigid tool geometries, high-pressure coolant, and premium carbide tooling inserts to manage heat accumulation.

• Surface Hardening Upgrades: Finished components made from 40NiMoCr10-4 can easily be surface-optimized via induction hardening, flame hardening, or gas nitriding to achieve a hard exterior layer for extreme wear surfaces without sacrificing the tough core.

• Welding Boundary Conditions: Welding is strongly discouraged for this grade in its pre-hardened state, as the rapid thermal cycle creates a highly brittle, crack-sensitive martensitic structure in the heat-affected zone. If joining is mandatory, preheating the bar to $300^circtext{C} - 400^circtext{C}$ is required, immediately followed by a controlled post-weld stress-relief or re-tempering cycle.

Exceptional Strength and Toughness

40NiMoCr10-4 Alloy Steel Bars are engineered to deliver high yield and tensile strengths after heat treatment, meeting the stringent requirements for components under heavy mechanical stress. Their structure ensures durability, making them suitable for applications such as gears, shafts, and fasteners in critical industries.


Versatile Processing and Finishing

The bars and rods can be supplied in a range of surface conditions including bright, black, peeled, or polished finishes. Available processing methods include annealing, hardening & tempering, and quenching, giving manufacturers flexibility to customize properties according to the end-use requirements.


Wide Range of Sizes and Lengths

With diameters from 6 mm up to 300 mm and lengths of 3 m, 6 m, or as cut to specification, 40NiMoCr10-4 Alloy Steel Bars accommodate varying project scales, minimizing waste and enhancing productivity in fabrication processes.