1J50 Alloy

1J50 is a high-performance iron-nickel (Fe-Ni) based soft magnetic alloy, belonging to the Permalloy family, specifically engineered for low-frequency magnetic applications requiring exceptional magnetic permeability, low coercivity, and stable magnetic properties. Unlike high-temperature superalloys (e.g., GH series, L-605) that prioritize thermal resistance and strength, 1J50 achieves its core soft magnetic performance through precise control of nickel content (≈50%), grain refinement, and stress-relief annealing — the nickel element forms a homogeneous austenitic structure with iron, which is critical for optimizing magnetic domain movement. This alloy excels in low-frequency (50-400Hz) magnetic environments, making it a preferred material for magnetic shielding, transformer cores, and precision magnetic components.

Notably, 1J50 exhibits excellent magnetic stability over a wide temperature range (typically -50℃ to 150℃) and maintains low magnetic hysteresis loss, ensuring high energy efficiency in magnetic circuits. Its good cold workability allows for manufacturing of ultra-thin strips (down to 0.01mm) and complex-shaped components, while its corrosion resistance (superior to plain carbon steel) extends service life in mild corrosive environments. It is widely used in electronics, telecommunications, instrumentation, and aerospace fields where high-performance soft magnetic properties are essential. The following is a comprehensive breakdown of its chemical composition, physical properties, magnetic properties, and application products.

1. Chemical Composition (Mass Fraction, %)

2. Key Magnetic Properties (After Standard Heat Treatment: 900-950℃ annealing for 3-4h, furnace cooling to 600℃, then air cooling)

Magnetic properties are the core performance indicators of 1J50, directly determining its applicability in magnetic components:

Key Notes on Magnetic Properties:

• High Initial Permeability (μᵢ ≥25,000μ₀): Enables the alloy to respond sensitively to weak magnetic fields, making it ideal for low-field applications (e.g., magnetic sensors, weak-signal transformers);
• Low Coercivity (Hc ≤5.0A/m): Reduces magnetic hysteresis loss, ensuring high energy efficiency in AC magnetic circuits (e.g., power transformers, inductors);
• Saturation 磁感应强度 (Bs ≥1.45T): Provides sufficient magnetic flux density for high-power magnetic components (e.g., audio transformers);
• Curie Temperature (Tc ≥490℃): Ensures magnetic stability at elevated temperatures (up to 150℃ in practical use), avoiding magnetic property degradation under thermal stress.
• Density: Approximately 8.20g/cm³ at room temperature (25℃), higher than plain carbon steel (7.85g/cm³) due to nickel addition, but lower than Fe-Ni-Cr superalloys (e.g., 1537 alloy: 7.85g/cm³ is consistent, 1J50 is slightly higher). This moderate density balances structural lightweighting and magnetic performance for precision components (e.g., small transformer cores).
• Melting Temperature Range: 1430-1480℃ (liquidus: ~1480℃; solidus: ~1430℃). The narrow melting range ensures uniform composition during casting, critical for avoiding segregation (which causes magnetic property inhomogeneity).
• Thermal Expansion Coefficient (CTE):

3. Physical Properties

3.1 Basic Physical Parameters

◦ 20-100℃: ~12.5×10⁻⁶/℃

◦ 20-300℃: ~13.5×10⁻⁶/℃

◦ 20-500℃: ~14.5×10⁻⁶/℃

The gradual CTE increase minimizes thermal stress during temperature cycling (e.g., electronic device heating/cooling), reducing deformation of magnetic components (e.g., transformer cores) and maintaining magnetic circuit stability.

• Thermal Conductivity (λ):

◦ 100℃: ~19.0W/(m·K)

◦ 300℃: ~22.0W/(m·K)

◦ 500℃: ~25.0W/(m·K)

Moderate thermal conductivity helps dissipate heat generated by magnetic hysteresis loss in AC applications, preventing overheating of high-power transformers.

3.2 Mechanical Properties (After Cold Rolling + Stress-Relief Annealing)

Key Notes:

• The high elongation (δ₅ ≥25%) and reduction of area (ψ ≥60%) indicate excellent cold workability, allowing the alloy to be rolled into ultra-thin strips (0.01-0.5mm) or drawn into wires (0.1-2.0mm) for miniaturized magnetic components;
• The moderate hardness (HV 120-150) simplifies post-processing (e.g., punching, bending) of complex-shaped parts (e.g., magnetic shielding cans) without requiring expensive hard machining tools;
• After cold rolling (with 30-50% deformation), the tensile strength can increase to 600-700MPa, but this will slightly reduce magnetic permeability — stress-relief annealing is therefore essential to restore optimal magnetic properties.

4. Application Products & Industry Scenarios

4.1 Electronics & Power Field

As a core soft magnetic material in electronics and power systems, 1J50 is used for:

• Low-Frequency Transformers: Cores of power transformers (50/60Hz), audio transformers, and instrument transformers (e.g., current transformers, voltage transformers), leveraging low hysteresis loss (P₁.₅/50 ≤3.0W/kg) to improve energy efficiency (up to 98% for high-quality audio transformers);
• Inductors & Chokes: Cores of power inductors, filter chokes, and common-mode chokes in power supplies (e.g., switching power supplies for computers, smartphones), where high magnetic permeability ensures effective electromagnetic interference (EMI) suppression;
• Magnetic Amplifiers: Cores of magnetic amplifiers in voltage regulators and power controllers, utilizing the alloy’s stable magnetic properties to achieve precise voltage regulation (error ≤±0.5%).

4.2 Telecommunications & Instrumentation Field

In telecommunications and precision instrumentation, 1J50 is applied to:

• Magnetic Shielding Components: Shielding cans, shielding sheets, and shielding sleeves for sensitive electronic devices (e.g., GPS modules, communication antennas, medical sensors), blocking external low-frequency magnetic interference (≤400Hz) and improving signal-to-noise ratio (SNR) by 20-30%;
• Magnetic Heads: Core components of tape recorders, magnetic card readers, and data storage devices (e.g., legacy floppy disk drives), where low coercivity (Hc ≤5.0A/m) ensures smooth magnetic domain reversal and high data read/write accuracy;
• Precision Magnetic Sensors: Cores of Hall effect sensors, fluxgate sensors, and magnetometers (used in navigation, geological exploration), leveraging high initial permeability (μᵢ ≥25,000μ₀) to detect weak magnetic fields (down to 10⁻⁷T).

4.3 Aerospace & Defense Field

In aerospace and defense systems requiring stable magnetic performance under harsh conditions, 1J50 is used for:

• Aerospace Magnetic Shielding: Shielding for avionics (e.g., flight control systems, radar receivers) and satellite communication modules, resisting temperature fluctuations (-50℃ to 120℃) and maintaining magnetic shielding effectiveness (≥40dB at 50Hz);
• Military Communication Equipment: Cores of low-frequency communication transformers and inductors in military radios and secure communication systems, ensuring reliable signal transmission in electromagnetic interference environments;
• Magnetic Actuators: Cores of solenoid valves and magnetic actuators in aircraft hydraulic systems, where fast magnetic domain response (enabled by low coercivity) ensures precise control of actuator movement.

4.4 Medical & Consumer Electronics Field

In medical devices and consumer electronics, 1J50 is used for:

• Medical Instrumentation: Magnetic shielding for MRI (Magnetic Resonance Imaging) accessories (e.g., patient monitoring sensors) and magnetic therapy equipment, preventing external magnetic fields from interfering with device operation;
• Consumer Electronics: Cores of wireless charging coils (e.g., for smartphones, smartwatches) and audio equipment (e.g., headphones, speakers), improving energy transfer efficiency (up to 85% for wireless charging) and audio quality (low distortion ≤1%);
• Household Appliances: Cores of transformers and inductors in refrigerators, air conditioners, and washing machines, reducing energy consumption by 5-10% compared to transformers using ordinary silicon steel.
• Smelting: Vacuum induction melting (VIM) is recommended to reduce impurity content (C, P, S) and ensure composition uniformity — air melting may lead to oxide inclusions that degrade magnetic properties;
• Cold Working: Cold rolling is the primary processing method for thin strips:

5. Processing & Heat Treatment Recommendations

◦ For strips ≤0.1mm: Use multi-pass rolling with intermediate annealing (700-750℃, 1h) after every 15-20% deformation to avoid cracking;

◦ For strips >0.1mm: Single-pass rolling with 30-40% deformation is feasible, followed by final stress-relief annealing;

• Heat Treatment:

◦ Magnetic Property Optimization Annealing: 900-950℃ for 3-4h, furnace cooling to 600℃ (cooling rate ≤50℃/h), then air cooling — this process eliminates internal stress, refines grains, and maximizes magnetic permeability;

◦ Stress-Relief Annealing After Cold Working: 750-800℃ for 1-2h, air cooling — used to restore magnetic properties after stamping or bending (avoids magnetic permeability reduction by 10-20%);

• Welding: Welding is not recommended for magnetic core components (as it causes local grain coarsening and magnetic property inhomogeneity); for structural parts (e.g., shielding cans), laser welding with post-weld annealing (700℃, 1h) is acceptable.

This comprehensive performance and application profile makes 1J50 a versatile and high-performance soft magnetic alloy for low-frequency magnetic applications, perfectly balancing magnetic properties, processability, and cost-effectiveness for the most demanding electronic, communication, and aerospace magnetic components.