Breaking Through Performance Bottlenecks: Why Is JNRF™ High-Magnetic-Induction-Gradient High-Silicon Steel the Ultimate Solution for High-Frequency, High-Speed ​​Motor Cores?

I. Industry Pain Points: The Dilemma in High-Speed Motor Core Materials

At ultra-high rotational speeds (>10,000 rpm), conventional electrical steel grades face severe physical limits:

• Conventional 3% Silicon Steel (e.g., 0.20 mm): Excellent saturation magnetization (~2.0 T) and ease of stamping. However, at high frequencies, eddy current loss increases exponentially, causing severe thermal issues and efficiency drops.
• Conventional 6.5% Silicon Steel (e.g., JNEX™): While uniform 6.5% Si achieves ultra-low core loss and near-zero magnetostriction, its saturation magnetization drops to ~1.8 T. Furthermore, its extreme brittleness makes complex tooth slot stamping or interlocking nearly impossible without severe tool chipping and sheet cracking.

II. Matrix Breakdown: JFE Super Core™ Four Major Series

To address varying frequency and application requirements, JFE Steel developed four distinct Super Core™ series using CVD (Chemical Vapor Deposition) continuous siliconizing technology. Understanding their positioning is essential for material selection:

III. Microstructural Decoupling: Gradient Distribution & Texture Engineering

JFE JNRF™ achieves a dual breakthrough on a single thin sheet through CVD continuous siliconizing and crystallographic texture optimization:

① Thickness-Direction Si Gradient

By controlling the CVD gas-phase reaction and diffusion time, the surface layers reach ~6.5% Si (high electrical resistivity to block eddy currents), while the central core maintains a lower Si concentration (preserving ductility, toughness, and high magnetization).

② Precise Crystallographic Texture Engineering

To overcome the higher hysteresis loss typical of gradient steels in the 50 Hz to 1 kHz range, JNRF™ incorporates texture control technology:

• Suppression of Adverse Grains: Significantly reduces {111} oriented grains, which are detrimental to soft magnetic performance.
• Enhancement of Favorable Grains: Increases the proportion of {100} and {110} oriented grains, which align with the easy magnetization axes.
• Final Result: Saturation magnetization is boosted to 2.0 T (equivalent to conventional 3% Si steel) while maintaining ultra-low core loss under high-frequency operation.

IV. Performance Comparison: JNRF™ in IPM Traction Motors

Based on JFE’s official test data for a 9 kW, 8-pole 48-slot Interior Permanent Magnet (IPM) motor:

Key Takeaway: 10JNRF maintains >95% efficiency at speeds over 10,000 rpm without sacrificing peak torque, delivering the ideal balance of high torque and high efficiency.

5. Manufacturing & Processing Guidelines by Youyou Company

To fully translate raw material properties into superior finished motor cores, Youyou Company recommends the following processing standards:

A. Precision Slitting & Stamping

• Carbide Tooling: Due to the higher surface hardness of Si-gradient steel, premium tungsten carbide dies are mandatory.
• Ultra-Thin Die Gap: For 0.10 mm sheets (10JNRF), the die clearance must be maintained within 5% to 8% of sheet thickness to control burr heights below 0.003 mm.

B. Lamination Methods: Interlocking vs. Backlack (Self-Bonding)

While JNRF™ possesses enough ductility to support conventional interlocking, Backlack (Self-Bonding Varnish) is highly recommended for maximum magnetic efficiency:

1. Zero Magnetic Shorting: Eliminates rivets, welds, and interlocking notches that create local eddy current loops and stress concentration.
2. Enhanced Structural Rigidity: Fully bonded laminations reduce NVH (Noise, Vibration, and Harshness) under high-frequency operation.
3. High Lamination Factor: Maintains a stacking factor above 95% even for 0.10 mm ultra-thin laminations without sheet distortion.

About YouYou Company

As a specialized manufacturer of high-precision motor lamination stacks and high-frequency reactor cores in China, YouYou Company delivers state-of-the-art precision stamping, 0.10mm ultra-thin self-bonding (Backlack) lamination, and gradient high-silicon steel (JNRF/JNHF/JNEX) processing services. We provide global OEMs and Tier-1 suppliers with end-to-end soft magnetic solutions—ranging from material selection and rapid motor stator/rotor or multi-gap block core prototyping (Micro-Wire EDM / Self-Bonding) to high-volume automated production with zero core loss degradation and maximum torque performance.

Developing next-generation EV traction motors, drone propulsion, or precision medical robotics? Contact our engineering team for JNRF™ sample prototyping, Backlack bonding trials, and magnetic core optimization.