1J85 (1J485) Mumetal-Type Soft Magnetic Alloy

1J85 (also designated 1J485) is a Chinese nickel-iron-molybdenum soft-magnetic alloy with very high initial permeability. It saturates readily in weak magnetic fields, has extremely low coercivity and hysteresis loss, and is the Chinese equivalent of international Mumetal / Permalloy 80 / Supermalloy-type Ni79Mo5 alloys. It is widely used for transformer and instrument-transformer cores, magnetic amplifiers, chokes and electromagnetic shielding.

Overview

• Material: 1J85 (1J485) — high-permeability Ni-Fe soft-magnetic alloy
• Type: Ni-Fe-Mo permalloy (Ni ~ 79 %, Mo ~ 5 %)
• Standard: GBn 198-88
• International equivalents: Mumetal / Permalloy 80 / Supermalloy / ASTM A753 Type 4
• Available forms: Strip, sheet, wire, thin tape, bar and custom profiles

Chemical Composition (wt%)

Nickel provides high permeability and corrosion resistance; molybdenum raises permeability, high-temperature stability and corrosion resistance while lowering coercivity; manganese and silicon refine the alloy and tune resistivity and grain structure.

Physical & Magnetic Properties

• Very high initial permeability — saturates rapidly in weak fields;
• Very low coercivity and low hysteresis loss on repeated magnetisation / demagnetisation;
• Stable magnetic properties over a wide temperature range.

Key Features

• High permeability for efficient magnetic-flux conduction;
• Low coercivity for fast response and high efficiency of magnetic devices;
• Good temperature stability of magnetic properties;
• Good workability — readily formed into thin tapes, wire and stampings.

Corrosion Behaviour

• Good resistance to damp, acidic and alkaline environments thanks to high Ni and Mo content;
• Good high-temperature oxidation resistance.

Fabrication & Heat Treatment

• Melting & casting: melted in vacuum or protective atmosphere to prevent oxidation; casting cooling rate carefully controlled to avoid cracking and residual stress.
• Final magnetic heat treatment: performed in dry hydrogen or cracked ammonia (dewpoint below −40 °C): high-temperature anneal typically at 1200 °C, followed by a second anneal at about 500 °C, to relieve residual stress, improve permeability and optimise the microstructure.
• Machining: readily machined on conventional equipment; low hardness and good plasticity suit complex forming.
• Surface treatment: nickel plating, oxide film or protective coating can be applied as required to improve corrosion and wear resistance.

Typical Applications

• Power systems: transformer cores, especially high-frequency transformers, to reduce electromagnetic loss and improve energy-transfer efficiency;
• Electronic equipment: inductors and chokes performing efficiently at high frequency;
• Electromagnetic shielding: shielding layers to suppress EMI between electronic devices and improve stability and reliability;
• Precision sensors: magnetic and position sensors exploiting high sensitivity and good temperature stability.

For detailed datasheets, magnetic-protocol test reports or inquiries on specific sizes and tolerances, please contact our sales & engineering team.