© N

PL M

anag

emen

t Lim

ited,

201

7.

119

55/0

2/17

DID YOU KNOW…

In 2010 the worldwide rare-earth materials market was more than 62,200 tons; with Europe having a market share of only 3%

ABSTRACT

INTRODUCTION Rare-earth (RE) magnets are ubiquitous within our everyday lives. They are found in electrical motors, sensors, loudspeakers, headphones, computers…the list goes on. These materials however, are subject to monopolies and price fluctuations, as can be seen in Figure 1.

The Horizon 2020 project, Resource Efficient Production of Magnets (REProMag) addresses the problem of the sustainability of RE magnets by developing an innovative automated manufacturing route.

ADDITIVE MANUFACTURINGThe Shaping, Debinding and Sintering (SDS) process being developed allows economically efficient production of net shape magnetic parts with complex structures and geometries, whilst being 100% waste free using fully-recycled raw material. The complexity of shapes that can readily be produced are shown in Figure 3.

This project is utilising three manufacturing methods (shaping): Fused Filament Fabrication, Metal Injection Molding and Lithography Ceramic Manufacturing. The processes require a feedstock where the RE material is in a multi component binding system, which must be removed (debinding). The final stage in the process involves sintering to achieve the finished fully-dense high performance magnet.

MATERIAL DEVELOPMENTThe manufactured materials are complex and the metallurgy is non-trivial. Significant efforts went into improving the material composition, to reduce the oxygen and carbon content during filament/feedstock production. As Figure 4 shows, the magnetic properties have greatly improved during the project.

COMPONENT VALIDATIONTraditional magnetic characterisation techniques cannot be used for complex components due to geometric limitations, field limits or measurement artefact complications. NPL are developing upon the pulsed field magnetometry (PFM) method to deliver component measurements. PFM is a method that allows for large scale component measurements with rapid evaluation potential. This convenience comes at the cost of two significant correction factors (self-demagnetisation and magnetic viscosity) which are being investigated and corrected for as part of this project. Figures 5 and 6 illustrate the phenomena.

ADDITIVE MANUFACTURE OF RECYCLED PERMANENT MAGNETS:

THE REALISATION OF A GREENER FUTURENicholas Hillier1

Figure 1: The cost of seven RE materials in US $/kg [1].

Figure 4: JH curves for different feedstocks during the project. The Carbon content for P2-F05 and P2-F06 was 0.11 wt% and 0.096 wt% respectively. Oxygen content was 1.18 wt% and 0.62 wt% respectively. P2-F14 is still to be analysed.

Figure 5: Graph illustrating the differences between measured demagnetisation factors and the calculated values as used by commercial PFM instruments.

Figure 6: Graph showing how the rate at which you perform the measurement effects the overall answer. This discrepancy is known as magnetic viscosity.

THE SDSPROCESS

Application

Debinding Recy

cling

Sintering

Shaping

Figure 2: A graphic illustrating the ethos of the REProMag Project.

Figure 3: Net-shaped geometries produced by REProMag.

Measured vs Theoretical DemagnetisationValues for a Range of Aspect Ratios

Theoretical

0.05

0.1

0.15

0.2

0.25

0.3

0.35

1 1.5 2 2.5

Nm

Aspect Ratio

Measured

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

–1360 –1340 –1320 –1300 –1280 –1260 –1240 –1220 –1200

Pola

risa

tion

, J (T

)

Magnetic Field, H (kA/m)

PRT 4 seconds dH/dt = 1.5 kA/m/s

PRT 24 seconds dH/dt = 0.12 kA/m/s

PRT 152 seconds dH/dt = 0.002 kA/m/s

Nicholas Hillier1, Stuart Harmon1, Peter Freigassner2, Stefan Hampel2, Christian Kukla3, Joamin Gonzalez-Gutierrez4, Oxana Weber5, Carlo Burkhardt5

1 National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, United Kingdom 2 HAGE Sondermaschinenbau GmbH & Co KG, Hauptstraße 52, 8742 Obdach, Austria3 Montanuniversitaet Leoben, Industrial Liaison Department, Peter Tunner Strasse 27, 8700 Leoben, Austria4 Montanuniversitaet Leoben, Department of Polymer Engineering and Science, Chair of Polymer Processing,

Otto Gloeckel-Strasse 2, 8700 Leoben, Austria5 OBE Ohnmacht & Baumgärtner GmbH & Co KG, Turnstraße 22, 75228 Ispringen, Germany

Acknowledgment:This work was supported by the UK government’s Department for Business, Energy and Industrial Strategy. Research has been done as part of the project “Resource Efficient Production for Magnets – REProMag” financed by the European Commission under the Horizon 2020 FoF-Framework under grant agreement 636881.

References:M. Humphries, “Rare Earth Elements: The Global Supply Chain”, CRS Report for Congress, 2012.

IMPACT• The use of recycled material will reduce Europe’s dependency on foreign materials

and mitigate the risk posed by these critical raw materials.

• The developed shaping technologies will improve production efficiency, reducing material waste, offering design freedom and providing rapid prototyping.

• Improved material characterisation techniques will enable component manufacturers a better understanding of their final product.

• NPL’s work on pulsed field magnetometry will give UK industry (i.e. automotive and green energy) a step advantage.

Lanthanum3.1

7.8

53

66.5

2.5

4.4

50

59.3

29

27

80

244.2

85

555

650

605

7

15

56

n/a

300

475

625

3,800

2,973.9

110

295

2,032.1

Cerium

Neodymium

Dysprosium

Terbium

Yttrium

Europium

0 500 1,000 1,500 2,000 2,500 3,000 3,500 $4,000/kg

2007

2008

2010 4th quarter

2011 4th quarter