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[REPM2025_O1-4_Goto.pdf](https://mdr.nims.go.jp/filesets/cc963a92-0a29-4a37-96ce-b30dbba8f422/download)

## Creator

Ryosuke Goto, Fumiaki Kihara, Takashi Oikawa, Hiroshi Miyawaki

## Rights

[Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International](https://creativecommons.org/licenses/by-nc-nd/4.0/)

## Other metadata

[Fabrication of high-performance HREE-free hot-deformed Nd-Fe-B magnets](https://mdr.nims.go.jp/datasets/e673fbc8-5e3a-42c9-b6b4-06f4707be484)

## Fulltext

Fabrication of high-performance  HREE-free hot-deformed  Nd-Fe-B magnetsREPM2025 | 28.07.2025 | Ryosuke Goto / 16Fabrication of high-performance HREE-free hot-deformed Nd-Fe-B magnets*Ryosuke Goto, Fumiaki Kihara, Takashi Oikawa, Hiroshi MiyawakiCorporate Research & Development Center, Daido Steel Co., Ltd.1O1-4   10:05 AM - 10:20 AM [JST]                                                                                      REPM2025@Tsukuba, Japan REPM2025 | 28.07.2025 | Ryosuke Goto / 16Background: About us2Segment Share of net salesSpecialty steels 38 %High-performance materials &Magnetic materials35 %Parts for automobile & Industrial equipment18 %Engineering 4 %Company name Daido Steel Co., Ltd.Head office location Nagoya, JapanFounded August 19th, 1916Number of employees 12,054 (consolidated)3,347 (non-consolidated)Net sales FY2024:  JPY 574.945 billion (consolidated)JPY 385.260 billion (non-consolidated)Common stock JPY 37,172 millionhttps://www.daido.co.jp/en/Approx. USD3.9 billionUSD2.6 billionREPM2025 | 28.07.2025 | Ryosuke Goto / 16Background: Hot-deformed magnets3Induction melting Melt spinning Cold press Hot press &Hot deformationAnnealingCrushingAvg. 250 μmMachining(Cutting and/or griding)IsotropicMelt spun ribbonsAnisotropicHot-deformed magnets✓ Melt spinning and hot press / hot deformation processes are critical to the performance of the magnets.Conventionalsintered magnetCrystal grains: 200~500 nmCrystal grains3~10 μmNd2Fe14B crystal grainc-axis10 μmTexturedc-axis c-axisProduction process of hot-deformed magnets OptionalREPM2025 | 28.07.2025 | Ryosuke Goto / 16Objective and Experimental procedure 4composition / at.% noteNd13.7Febal.Co1.5Ga0.5B5.6 Aiming for high BrNd14.1Febal.Co1.5Ga0.5B5.6 Aiming for a better balance between Br & HcjNd14.3Febal.Co1.5Ga0.5B5.6 Conventional (for comparison)Induction meltingMelt spinningCrushing / classificationCold pressHot press / hot deformationAnnealingEvaluationdeviceMagnetic properties Pulse magnetometer, DC-BH tracerMicrostructure FE-SEMdeviceMagnetic properties VSMRibbon thickness Coaxial laser displacement gaugeMicrostructure FE-SEM✓ Improve magnetic properties of hot-deformed magnets without heavy rare earth elements.*Forward extrusionREPM2025 | 28.07.2025 | Ryosuke Goto / 16Experiments: Optimization of melt spinning process5[2] K. Miyazawa and T. Choh, J. Japan Inst. Metals, 47, 8 (1983),pp. 717-723𝑯 =𝜋𝒅𝒏24𝒖𝑊𝑐𝑣2𝜟𝑷𝜌+ 2𝑔ℎ⋯(4)From flow balance conservation,where, melt flow rate Q [m3/s] is(Cross-sectional area of orifice, A)×(Velocity of melt, Vn)From equation (1) and (2), Thickness of ribbon H is𝑄 = 𝐻 ∙ 𝑊 ∙ 𝑢 ⋯(1)𝑄 = 𝐴 ∙ 𝑉𝑛 =𝜋𝑑𝑛24∙ 𝑉𝑛 ⋯(2)𝑉𝑛 = 𝑐𝑣2𝛥𝑃𝜌+ 2𝑔ℎ ⋯(3)Q : melt flow rate (m3/s)H    : thickness of ribbon (m)W : width of ribbon (m)u   : wheel speed (m/s)A : cross-sectional area of orifice (m2)Vn : velocity of melt (m/s)         dn : nozzle diameter (m)cv : velocity constant (-)ΔP : differential pressure (Pa)ρ : melt density (kg/m3)g : gravitational acceleration (m/s2)h : height of melt surface (m)meltpuddlewheelwheelvelocity boundary layer uHuudn/2WdnVnlnrhnozzle✓ Nozzle diameter (dn), wheel speed (u) and differential pressure (ΔP) were optimized.Fig . Schematic image of melt spinningREPM2025 | 28.07.2025 | Ryosuke Goto / 16Results: Magnetic properties of Nd-Fe-B melt spun ribbons6✓ Quenching state was changed by melt spinning conditionsFig . Demagnetization curves of melt spun ribbons Fig .Thickness of melt spun ribbonsMax.Min.Median75%25%N=60N=60Over quenchedUnder quenchedThickness and its deviation can be controlled by optimized melt spinning➢ Optimized : finer and more homogeneous grains➢ Over quenched : Partially amorphous➢ Under quenched : Coarse grainsNd 13.7 at%REPM2025 | 28.07.2025 | Ryosuke Goto / 16Left edge Left center Center Right center Right edgeFree sideB68610Wheel sideResults: Microstructure of Nd-Fe-B melt spun ribbons7Grain size measurement of melt spun ribbons✓ Photos of 10 positions in fractured surface✓ Grain identification by CNN (U-Net)✓ Calculate the circle equivalent diameter of grainsConventional100 nm100 nm100 nm100 nm100 nm100 nm 100 nm 100 nm100 nm100 nmREPM2025 | 28.07.2025 | Ryosuke Goto / 16Left edge Left center Center Right center Right edgeFree sideB68610Wheel sideResults: Microstructure of Nd-Fe-B melt spun ribbons8Grain size measurement of melt spun ribbons✓ Photos of 10 positions in fractured surface✓ Grain identification by CNN (U-Net)✓ Calculate the circle equivalent diameter of grainsConventional100 nm100 nm100 nm100 nm100 nm100 nm 100 nm 100 nm100 nm100 nmREPM2025 | 28.07.2025 | Ryosuke Goto / 16Left edge Left center Center Right center Right edgeFree sideRQB5307Wheel sideResults: Microstructure of Nd-Fe-B melt spun ribbons9OptimizedGrain size measurement of melt spun ribbons✓ Photos of 10 positions in fractured surface✓ Grain identification by CNN (U-Net)✓ Calculate the circle equivalent diameter of grains100 nm100 nm100 nm100 nm100 nm100 nm 100 nm 100 nm100 nm100 nmREPM2025 | 28.07.2025 | Ryosuke Goto / 16Left edge Left center Center Right center Right edgeFree sideRQB5307Wheel sideResults: Microstructure of Nd-Fe-B melt spun ribbons10OptimizedGrain size measurement of melt spun ribbons✓ Photos of 10 positions in fractured surface✓ Grain identification by CNN (U-Net)✓ Calculate the circle equivalent diameter of grains100 nm100 nm100 nm100 nm100 nm100 nm 100 nm 100 nm100 nm100 nmREPM2025 | 28.07.2025 | Ryosuke Goto / 16Results: Microstructure of Nd-Fe-B melt spun ribbons11✓ The grain size was finer on both the wheel and free side of the optimized ribbon.✓ Average grain size of the ribbons was 45nm in conventional ribbons, and 37 nm in optimized one.Fig. SEM images of fractured surface of melt spun ribbons (center)Table. Average grains size of melt spun ribbonsConventional Optimized Average grain size 45 nm 37 nmStandard deviation, σ 15.1 11.8020406080Grain size / nm(a) ConventionalFree sideWheel sideLeft                                         Right020406080Grain size / nm(b) OptimizedFree sideWheel sideLeft                                         RightFig . Grain size of melt spun ribbons (a) conventional and (b) optimized ribbonREPM2025 | 28.07.2025 | Ryosuke Goto / 16Results: Magnetic properties of hot-deformed Nd-Fe-B magnets12𝛽 =𝐻𝑐𝑗 23℃ −𝐻𝑐𝑗(150℃)(23℃− 150℃)×100𝐻𝑐𝑗(23℃)Hcj [kA/m] β [%/K]Temp.[℃] 23 150 150Hot-deformed HRE Free 1725 720 -0.458Sinteredw/ Dy 1873 648 -0.515w/ Tb 1935 668 -0.516Hot-deformed(HREE-free)Optimized#2Sintered, with DySintered, with Tb✓ Optimized hot-deformed magnets show a good temperature coefficient of coercivity β.✓ Remanence +6% or Coercivity +14% due to the optimization of melt spinning.Fig. Demagnetization curves of Nd-Fe-B hot-deformed magnetsNd -1.0 wt.% Nd -0.4 wt.%40060080010001200140016001800200022000 50 100 150 200Coercivity, HcJ/ kA・m-1Temperature, T / ℃Fig. Temperature dependence of coercivityREPM2025 | 28.07.2025 | Ryosuke Goto / 16Results: Magnetic properties of hot-deformed Nd-Fe-B magnets13𝛽 =𝐻𝑐𝑗 23℃ −𝐻𝑐𝑗(150℃)(23℃− 150℃)×100𝐻𝑐𝑗(23℃)Hcj [kA/m] β [%/K]Temp.[℃] 23 150 150Hot-deformed HRE Free 1725 720 -0.458Sinteredw/ Dy 1873 648 -0.515w/ Tb 1935 668 -0.516Hot-deformed(HREE-free)Optimized#2Sintered, with DySintered, with Tb✓ Optimized hot-deformed magnets show a good temperature coefficient of coercivity β.✓ Remanence +6% or Coercivity +14% due to the optimization of melt spinning.Fig. Demagnetization curves of Nd-Fe-B hot-deformed magnetsNd -1.0 wt.% Nd -0.4 wt.%40060080010001200140016001800200022000 50 100 150 200Coercivity, HcJ/ kA・m-1Temperature, T / ℃Fig. Temperature dependence of coercivityNd (0.6) at%(1.0) wt%Nd (0.2) at%(0.4) wt%Fig. Magnetic property map of Nd-Fe-B hot-deformed magnetsTb-GDB, SinteredREPM2025 | 28.07.2025 | Ryosuke Goto / 16Results: Microstructure of hot-deformed Nd-Fe-B magnets14✓ Optimized hot-deformed magnets have a finer and more textured grains than the conventional one.Equiaxed grainsMixture of equiaxed and textured grains20μm500nm500nm500nmTextured grains500nm500nmFiner and textured grainsFiner and textured grains20μmFig. Schematic image of cross section of conventional ribbonFig. Schematic image of cross sectionof optimized ribbonFree sideWheel sideFree sideWheel sidePartially amorphousConventional Optimizedc-axis c-axisAfter etching After etchingCoarse grainsREPM2025 | 28.07.2025 | Ryosuke Goto / 16Conclusion➢High-performance hot-deformed magnets without Heavy Rare Earth Elementswere obtained by optimization of melt spinning process.➢Although the RE content is low, hot deformed magnets with higher performance than conventional ones were obtained.Remanence +6% and Nd can be reduced by 1.0 wt.%or Coercivity +14% and Nd can be reduced by 0.4 wt.%15REPM2025 | 28.07.2025 | Ryosuke Goto / 1616Thank you for your attention ! presentation スライド 1: Fabrication of high-performance  HREE-free hot-deformed  Nd-Fe-B magnets スライド 2: Background: About us スライド 3: Background: Hot-deformed magnets スライド 4: Objective and Experimental procedure  スライド 5: Experiments: Optimization of melt spinning process スライド 6: Results: Magnetic properties of Nd-Fe-B melt spun ribbons スライド 7: Results: Microstructure of Nd-Fe-B melt spun ribbons スライド 8: Results: Microstructure of Nd-Fe-B melt spun ribbons スライド 9: Results: Microstructure of Nd-Fe-B melt spun ribbons スライド 10: Results: Microstructure of Nd-Fe-B melt spun ribbons スライド 11: Results: Microstructure of Nd-Fe-B melt spun ribbons スライド 12: Results: Magnetic properties of hot-deformed Nd-Fe-B magnets スライド 13: Results: Magnetic properties of hot-deformed Nd-Fe-B magnets スライド 14: Results: Microstructure of hot-deformed Nd-Fe-B magnets スライド 15: Conclusion スライド 16