ASTM A753 is an international standard that covers wrought nickel-iron soft magnetic alloys used primarily for magnetic cores and shields requiring high permeability, high electrical resistivity, low coercivity, and minimal core loss. Within this family, the alloy designated under material number 2.4530 (FeNi77CuMo) is distinguished by the highest initial and maximum permeability among the group, as well as the lowest coercive field strength. This combination of properties makes it essential for fault-current circuit breakers, magnetic amplifiers, magnetic heads, relays, shields, measurement devices, inductors, and transducers.
Specifications & AvailableFeNi77CuMo (2.4530) is a nickel-iron based soft magnetic alloy alloyed with copper and molybdenum. These additions refine the magnetic domain behavior, optimize the magnetocrystalline anisotropy, and increase electrical resistivity, which reduces eddy current losses. The alloy is typically delivered in the form of strip, sheet, or bar and achieves its optimum magnetic properties through a controlled hydrogen annealing process. Available Forms: Strip, sheet, bar, wire, and laminated cores Specifications: ASTM A753 (Alloy Type 4 or similar high-permeability Ni-Fe type), UNS K94430 (comparable grade), Werkstoff Nr. 2.4530
Magnetic Performance & Operating ConditionsFeNi77CuMo (2.4530) is selected for components that require the highest sensitivity to weak magnetic fields and the lowest possible energy loss. Highest Permeability, Lowest Coercivity: Compared to other ASTM A753 nickel-iron alloys, this grade delivers the highest initial and maximum permeability and the lowest coercivity. This ensures extremely low hysteresis loss and rapid magnetic reversal, which is critical for high-precision measuring and sensing applications. High Resistivity: The addition of molybdenum increases electrical resistivity (0.55–0.60 µΩ·m) compared to standard 80% Ni permalloys. This reduces eddy current losses, making the alloy suitable for AC applications up to moderate frequencies. Temperature Stability: The alloy exhibits stable magnetic properties within its specified operating range (typically up to 150-200°C), provided it stays well below its Curie temperature (approx. 450°C). Annealing Sensitivity: Optimum soft magnetic properties are achieved only after a specific annealing cycle, typically performed in a hydrogen atmosphere at 1100-1200°C (2000-2200°F), followed by controlled cooling. This treatment relieves internal stresses and optimizes the crystal structure for maximum permeability.
Fabrication Annealing (Critical Step): To achieve the specified high permeability and low coercivity, finished cores or stamped parts must be annealed at approximately 1150°C (2100°F) in a pure, dry hydrogen atmosphere. This process removes impurities and relieves stresses introduced during stamping or winding. Cold Working: The alloy is ductile and can be stamped, slit, or wound into toroidal cores in the soft state. Any severe cold work will degrade magnetic properties, mandating a final anneal. Machining: Machinability is fair; the alloy is relatively soft and can gall. Sharp tooling is essential.
For inquiries, technical datasheets, or a competitive quote, contact our sales team. We are ready to support your project with certified ASTM A753 2.4530 (FeNi77CuMo) soft magnetic alloy for fault-current breakers, magnetic amplifiers, and precision measurement devices. Contact Us 📧 Email: daisy@zytcsteel.com
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