RARE-EARTH PERMANENT MAGNETS VACODYM VACOMAX ADVANCED MATERIALS THE KEY TO PROGRESS

Transcription

1 RARE-EARTH PERMANENT MAGNETS VACODYM VACOMAX ADVANCED MATERIALS THE KEY TO PROGRESS

2 CONTENTS page 1. Introduction 4 2. Product Range 6 3. Applications 9 4. Materials and Magnetic Properties Characteristic Properties Material Grades Temperature Dependence and Magnetic Losses Magnetization of RE Magnets 4 5. Corrosion Behaviour, Surface Protection and Coatings Corrosion Behaviour Surface Protection Types of Coating Description of the Coatings Forms of Supply Types of Magnetization Dimensional Tolerances Glueing RE Magnets Integrated Management System Quality Management Technial terms and Conditions of Sale Environmental and Safety Management Safety Guidelines Appendix: Technical Principles and Terms Conversion Table Celsius Fahrenheit Ductile Permanent Magnet alloys and Magnetically Semi-hard Materials 58 2

3 RARE-EARTH PERMANENT MAGNETS VACODYM VACOMAX VACUUMSCHMELZE GmbH & Co. KG (VAC) is one of the world s leading producers of special metallic materials with exceptional physical properties and resulting products. The company has a staff of approximately 3., is represented in 4 countries spread across all continents and currently achieves a turnover of more than 27 million. The headquarters, including operational headquarters of VAC is in Hanau, Germany. The company also has production plants in Slovakia and China. 3

4 1. INTRODUCTION In addition to permanent magnets, the product range includes soft magnetic materials, semi-finished products and parts, inductive components, magnetic shieldings and various other materials with special physical properties. Apart from the rare-earth permanent magnets, the spectrum includes, ductile permanent magnets and magnetically semi-hard materials. The latter are characterized by low-cost forming capabilities and adjustable permanent magnet properties. We have been working on the magnetic properties of special metallic materials and their applications for over 7 years. In 1973 we had already started producing permanent magnets on a rare-earth-cobalt base using powder metallurgical methods. By finding optimum solutions in close cooperation with our customers we have contributed strongly to the widespread use of this new material group available under the trade name VACOMAX. VACODYM * is our trade name for neodymium-iron-boron magnets. VACODYM has been produced on an industrial scale since Our materials have the highest energy density available to date. All processing steps from melting the alloy under vacuum through to coating the finished parts are performed at our works ensuring optimum material properties throughout the entire production process. As market leader in Europe today, we belong to the worldwide top-ranking producers of rare-earth permanent magnets. The magnetic properties are largely determined by the prematerial and the production process. Magnets can be produced in three different ways. These three methods are identified by the letters HR, TP, or AP in the alloy code. HR (high remanence) refers to the isostatically pressed magnets, as in the past. In the die pressed design we differentiate between TP (transverse pressed) and AP (axial pressed). Details on the available forms of supply are given in Section 6. Intensive development work has continually adapted our range of VACODYM alloys to the demands of the market. The focus being on the magnetic properties and especially on improving corrosion resistance, which was realized in the newly developed 8-Series consisting of VACODYM 837, = registered trademark of VACUUMSCHMELZE *) = licensor NEOMAX Co. Ltd. (Japan) 4

5 854, 863, 872 and 89. This new series of alloys and the 6-Series consisting of VACODYM 633, 655, 669, 677 and 688 already successfully launched on the market magnets particularly suitable for use in motor applications are available. These can be used under normal ambient conditions without any extra surface coating. For systems we developed a group of alloys for application temperatures up to 15 C the so-called 7-Series of VACODYM 722, 745, 764 and 776, which are characterized by particularly high remanence in-duction values. If the best possible corrosion resistance is an additional issue the high remanent qualities of VACODYM 837 and 854 from the 8-Series are a further option. Economic production processes, modern inspection techniques and a certified quality management system complying with DIN EN ISO 91, ISO TS and DIN EN ISO 141 are as much a matter of course as staff training sessions and an active environmental protection policy. By continuing to build on our long established foundations, we aim to remain your reliable and competent partner. Fig 1: Development of energy densities (BH) max of permanent magnets and their potential. 8 7 (BH) max [kj/m 3 ] Future possibilities of new materials (BH) max = 485 kj / m 3 (Theoretical limits NdFeB) NdFeB 3 2 Sm 2 Co 17 1 Steel AlNiCo SmCo 5 Ferrite Year 5

6 2. PRODUCT RANGE The product range of our rare-earth magnets covers a carefully balanced program of materials with different magnetic properties. As a result, it is relatively easy to select a material suitable for any specific application. VACODYM is the permanent magnet material offering the highest energy densities currently available. The excellent magnetic properties of this material group can be traced to the strongly magnetic matrix phase Nd 2 Fe 14 B featuring very high saturation polarization and high magnetic anisotropy. A ductile neodymium-rich bonding phase at the grain boundaries provides these magnets with good mechanical properties. Fig. 2 gives an overview of the typical properties of our VACODYM-magnets. VACOMAX is our permanent magnet material of rare-earths and cobalt. These magnets feature especially high coercivities with simultaneously high saturation and excellent temperature and corrosion stability. In Fig. 3 the typical demagnetization curves of VACODYM and VACOMAX are compared with the classical permanent magnet materials AlNiCo and hard ferrite. VACUUMSCHMELZE has many years of experience in the production of permanent magnets and the design of magnetic circuits. Alongside analytical processes, we utilize sophisticated computer programs to analyze and design magnet systems. These include 2D- and 3D-field calculations with finite element methods. Their use has substantially shortened the design phase of assemblies. As a result, besides single magnets, we are supplying an increasing number of finished magnet assemblies to customer s specifications. Detailed information on these is given in our PD-4 leaflet. Fig. 2: 1,5 Remanence B r and coercivity H cj of transverse field pressed VACODYM magnets 1,45 1,4 1, TP 764 TP 837 TP 854 TP VACODYM remanence, Br (T) 1,3 1,25 1,2 633 TP 776 TP 655 TP 863 TP 669 TP 872 TP 89 TP 1, TP 1,1 688 TP 1,5 1, coercivity, H cj (ka/m) 6

7 Fig. 3: Typical demagnetization curves of VACODYM and VACOMAX in comparison with AlNiCo and Ferrite at room temperature The use of soft magnetic materials as system components, e.g. VACOFLUX and VACOFER, enables us to meet customers specifications at a high quality level. In many cases optimum assembly and magnetization of the systems is only possible when the magnets and the other system components are sourced and put together at the magnet producer. by strong magnetic fields parallel (axial field for AP-grades) or perpendicular (transverse fields for TP-grades) to the direction of pressing depending on the geometry of the part. Isostatically or transverse-field pressed parts have an approximately 5 8% higher remanence compared to axial-field pressed magnets. Magnets made of VACODYM and VACOMAX are produced powder metallurgically by sintering. The main processing steps are given in Fig. 4. Depending on size, shape, tolerances, batch size and magnetic requirements, the parts are either cut from isostatically pressed blocks or are diepressed. When diepressing, the powder particles are aligned 7

8 Melting of the Alloy under Vacuum Crushing Milling Alignment in Magnetic Field isostatic Pressing die pressed Transverse Field (TP) Axial Field (AP) Sintering, Annealing Machining, Coating Magnetizing Fig. 4: Production steps of rare-earth magnets 8

9 3. APPLICATIONS Compared to conventional magnet materials, such as AlNiCo or hard ferrite, magnets of VACODYM and VACOMAX display a number of excellent magnetic properties. Users benefit immensely from their merits: Energy densities up to tenfold those of AlNiCo and hard ferrite not only enable a reduction in magnet volume (see Fig. 5), but also the miniaturization of systems and whole subassemblies, saving the costs for return paths, coils etc. Existing magnet systems can be improved in many cases. In general, when using VACODYM or VACOMAX we recommend the previous systems to be re-designed. New design ideas can be utilized and new fields of applications are opened: MOTORS AND GENERATORS Servomotors, DC motors, linear motors and heavy-duty motors (e.g. motors for ships propulsion and wind turbine generator systems) utilize predominantly VACODYM magnets. In the case of high temperatures VACOMAX is the material of choice. A further important application is small power and fractional horsepower motors, e.g. bell type armature and dental motors. Assemblies for motors Rotor of a servomotor Fig. 5: Example illustrating the volume reduction achieved with VACODYM and VACOMAX: each magnet is designed to produce a field of 1 mt at the reference point P = 5 mm from the surface of the pole 9

10 AUTOMOTIVE ENGINEERING AND SENSORS Sensors to measure engine, gear and wheel rotary speed (e.g. ABS systems), accelerations (e.g. ESP, airbag) or positions (e.g. throttle valve, injection systems, camshaft, crankshaft, fuel gauges) are equipped with VACOMAX or VACODYM magnets, depending on the requirements for temperature and corrosion stability. Sensor for electronic vehicle stabilization program (ESP) Sensor (module in plastic housing with customer specific connectors) module cap: inner (with magnet) and outer view Producer: Robert Bosch GmbH VACODYM magnets, in particular, should be considered for actuators in engine management, small motors (e.g. steering boost), generators and for noise reduction. Synchronous motors as main drives in electro and hybrid vehicles are also equipped with VACODYM magnets. MRI (MAGNET RESONANCE IMAGING) In precise analysis equipment in medical engineering more and more permanent magnet systems with high remanent VACODYM grades are used besides superconducting and other electrically excited systems. The main advantages are the very low energy consumption, savings in weight and a maintenance-free construction. Synchronous coupling with VACODYM-magnets MAGNETIC COUPLINGS Magnetic couplings are preferred in automation and chemical processing technology as they ensure a permanent hermetic separation of different media. Owing to increased temperature requirements, VACOMAX magnets are used for numerous applications. VACODYM is recommended for lower application temperatures. Field line characteristic (Finite elements calculation) 1

11 A dipole with a diameter of 1.5 m is the heart of a particle detector named Alpha Magnetic Spectrometer (AMS). It is manufactured from approx. 5 rectangular magnets made of VACODYM 51 HR and operates successfully aboard the ISS space station since

12 BEAM GUIDING SYSTEMS, WIGGLERS AND UNDULATORS Permanent magnetic beam guiding systems require very little maintenance and no power supply. Systems using VACODYM or VACOMAX magnets have proved imperative in all applications where high field strengths have to be achieved in special reaction chambers, e.g. in sputtering devices, travelling wave tubes, wigglers, undulators and multi-pole devices as well as particle detectors. To meet these requirements, we produce defined and carefully balanced compatible sets of magnets exhibiting magnetic properties to tight tolerances, such as the angle between the preferred magnetic direction and the geometry of the parts. Economic manufacturing processes are available to produce parts with a large volume, in particular, we can produce large magnet cross sections with pole surfaces up to approx. 11 cm m long undulator system with magnets of VACODYM and polepieces of VACOFLUX for the TESLA Test Facility at DESY in Hamburg. 12

13 PERMANENT MAGNET BEARINGS Different magnetic bearing principles have been developed for turbo-molecular pumps, centrifuges etc. These employ ring magnets magnetized in either axial or radial direction. The material is selected according to customer s specifications. HOLDING SYSTEMS Clamping plates and vibration dampers for machine tools are one of the main fields of application for holding systems. These normally require maximum holding forces and call for VACODYM. We supply ready-to-use holding assemblies with pot-shaped iron return passes as well as single magnets. MEASURING INSTRUMENTS In this field the applications range from electronic scales through pulse meters to NMR-analysis equipment. Depending on the construction principle systems using armatures or rotors fitted with VACODYM or VACOMAX magnets are selected. SWITCHES AND RELAYS For the widely varying designs of Hall switches, polarized relays, revolution counters etc., magnets or magnet assemblies incorporating VACODYM or VACOMAX are used depending on the specification. Mass spectrometer from INFICON GmbH with magnet assembly made of VACOMAX 13

14 4. MATERIALS AND MAGNETIC PROPERTIES 4.1 CHARACTERISTIC PROPERTIES Table 1: CHARACTERISTIC PROPERTIES OF VACODYM AT ROOM TEMPERATURE (2 C) Pressing Material Code 1 ) Remanence Coercivity direction 1) Coding based on IEC , the magnetic values usually exceed the IEC values B r B r H cb H cb typ. min. typ. min. Tesla kg Tesla kg ka/m koe ka/m koe HR VACODYM 722 HR 38/87,5 1,47 14,7 1,42 14, , ,5 VACODYM 745 HR 37/111,5 1,44 14,4 1,4 14, , ,4 VACODYM 51 HR 36/95,5 1,41 14,1 1,38 13, , ,5 VACODYM 633 HR 315/127,5 1,35 13,5 1,29 12, , ,3 VACODYM 655 HR 28/167 1,28 12,8 1,22 12, , ,6 VACODYM 677 HR 24/223 1,18 11,8 1,12 11, ,5 85 1,7 TP VACODYM 745 TP 355/111,5 1,41 14,1 1,37 13, , , VACODYM 764 TP 335/127,5 1,37 13,7 1,33 13, , ,6 VACODYM 776 TP 35/167 1,32 13,2 1,28 12, , ,2 VACODYM 837 TP 335/127,5 1,37 13,7 1,33 13, , ,7 VACODYM 854 TP 31/167 1,32 13,2 1,28 12, , ,2 VACODYM 863 TP 295/2 1,29 12,9 1,25 12, , ,9 VACODYM 872 TP 28/223 1,25 12,5 1,21 12, , ,5 VACODYM 89 TP 25/263 1,19 11,9 1,15 11, , ,9 VACODYM 633 TP 35/127,5 1,32 13,2 1,28 12, , ,2 VACODYM 655 TP 28/167 1,26 12,6 1,22 12, , ,6 VACODYM 669 TP 255/2 1,22 12,2 1,17 11, , , VACODYM 677 TP 24/223 1,18 11,8 1,13 11, ,5 86 1,8 VACODYM 688 TP 225/262,5 1,14 11,4 1,9 1, ,1 83 1,4 AP VACODYM 745 AP 325/111,5 1,34 13,4 1,31 13, , ,2 VACODYM 764 AP 35/135,5 1,3 13, 1,27 12, , , VACODYM 776 AP 28/167 1,26 12,6 1,22 12, , ,5 VACODYM 837 AP 3/135,5 1,3 13, 1,26 12, , ,9 VACODYM 854 AP 275/167 1,26 12,6 1,21 12, , ,4 VACODYM 863 AP 25/2 1,21 12,1 1,17 11, , , VACODYM 872 AP 235/223 1,17 11,7 1,13 11, , ,6 VACODYM 89 AP 21/263 1,11 11,1 1,7 1, , , VACODYM 633 AP 28/135,5 1,26 12,6 1,22 12, , ,5 VACODYM 655 AP 255/167 1,2 12, 1,16 11, , ,9 VACODYM 669 AP 225/2 1,16 11,6 1,12 11, ,1 82 1,3 VACODYM 677 AP 215/223 1,13 11,3 1,8 1,8 86 1,8 85 1,1 VACODYM 688 AP 2/262,5 1,8 1,8 1,3 1,3 83 1,4 77 9,7 14

15 Energy density Temperature coefficient Density Max. 2-1 C 2-15 C continuous Temperature H cj (BH) max (BH) max TK (B r ) TK (H cj ) TK (B r ) TK(H cj ) T max 2) min. typ. min. typ. typ. typ. typ. typ. ka/m koe kj/m 3 MGOe kj/m 3 MGOe %/ C %/ C %/ C %/ C g/cm 3 C F ,115,77 7, ,115,73 7, ,115,79 7, ,95,65,15,55 7, ,9,61,1,55 7, ,85,55,95,5 7, ,115,73 7, ,115,7,125,59 7, ,11,61,12,55 7, ,11,62,12,54 7, ,15,6,115,53 7, ,1,56,11,51 7, ,95,53,15,49 7, ,9,5,1,46 7, ,95,65,15,57 7, ,9,61,1,55 7, ,85,57,95,51 7, ,85,55,95,5 7, ,8,51,9,46 7, ,115,73 7, ,115,69,125,58 7, ,11,61,12,55 7, ,11,62,12,54 7, ,15,6,115,53 7, ,1,56,11,51 7, ,95,53,15,49 7, ,9,5,1,46 7, ,95,64,15,57 7, ,9,61,1,55 7, ,85,57,95,51 7, ,85,55,95,5 7, ,8,51,9,46 7, ) The maximum application temperature is governed by the layout of the system. The approx. values given refer to magnets operating in working points of B/μ o H = -1 (max. energy product). Users are recommended to consult VAC on any application of VACODYM involving temperatures above 15 C. 15

16 Table 2: CHARACTERISTIC PROPERTIES OF VACOMAX AT ROOM TEMPERATURE (2 C) Material Remanence Coercivity Code 1 ) B r B r H cb H cb H cj typ. min. typ. min. min. Tesla kg Tesla kg ka/m koe ka/m koe ka/m koe VACOMAX 24 HR 1,12 11,2 1,5 1,5 73 9,2 6 7,5 64 8, 2/64 VACOMAX 225 HR 1,1 11, 1,3 1,3 82 1,3 72 9, 159 2, 19/159 VACOMAX 225 TP 1,7 1,7 1,3 1,3 79 9,9 72 9, 159 2, 19/159 VACOMAX 225 AP 1,4 1,4,97 9,7 76 9,6 68 8, , 17/159 VACOMAX 2 HR 1,1 1,1,98 9, ,5 71 8, ,5 18/1 VACOMAX 17,95 9,5,9 9, 72 9, 66 8, , 16/12 VACOMAX 145 S,9 9,,85 8,5 66 8,3 6 7, , 14/2 1 ) Coding based on IEC , the magnetic values usually exceed the IEC values Table 3: CHARACTERISTIC PROPERTIES OF VACODYM AND VACOMAX AT ROOM TEMPERATURE (2 C) Material Curie- Specific Specific Thermal Coefficient of thermal Young s Bending Compressive Vickers- Stress temp. electr. heat con- expansion modulus strength strength hardness crack resistance ductivity 2-1 C resistance II c c K IC C mm 2 /m J/(kg K) W/(m K) 1-6 /K 1-6 /K kn/mm 2 N/mm 2 N/mm 2 HV N/mm 3/2 VACODYM ,1 1, VACOMAX Sm 2 Co ,65, VACOMAX SmCo ,4,

17 Energy density Temperature coefficient Density Max. 2-1 C 2-15 C continuous temperature (BH) max (BH) max TK (B r ) TK(H cj ) TK (B r ) TK(H cj ) T 2 ) max typ. min. typ. typ. typ. typ. typ. kj/m 3 MGOe kj/m 3 MGOe %/ C %/ C %/ C %/ C g/cm 3 C F ,3,15,35,16 8, ,3,18,35,19 8, ,3,18,35,19 8, ,3,18,35,19 8, ,4,21,45,22 8, ,4,21,45,22 8, ,4,14,45,15 8, ) Prior to using VACOMAX above 2 C we recommend customers contact VAC. Table 4: Material INNER MAGNETIZING FIELD STRENGTH OF VACODYM AND VACOMAX ka/m H mag min. koe VACODYM VACOMAX VACOMAX VACOMAX 145/17/

18 4.2 MATERIAL GRADES VACODYM and VACOMAX are anisotropic materials with a reversible permeability µ rev < 1.1 at the working point. The exact value depends on the material grade and the magnet geometry. VACODYM and VACOMAX do not feature open porosity, i.e. the pores are not connected to one another. Therefore both materials can be utilized for vacuum applications. The following pages show demagnetization curves of different grades at various temperatures. Additionally, the typical irreversible losses are given as a function of temperature at different loadlines. These charts are based on HR- or TP-grades. Axial field pressed magnets have slightly reduced losses under comparable conditions. The measured curves refer to magnets whose minimum dimensions are >1 mm perpendicular to the direction of magnetization and > 5 mm parallel to it. Smaller dimensions may deviate from the curves shown. 18

19 4.2.1 SINTERED MAGNETS ON A Nd-Fe-B BASE VACODYM 722 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 722 HR -1, -1,5-2, -4, T 1,6 1,4 kg ,5 2 C 6 C 8 C 1 C 12 C 1,2 1,,8, J,B,4 4,2 2, -,2-2 -,4-4 -,6-6 -,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature 19

20 VACODYM 745 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 745 HR -,5-1, -1,5-2, -4, 2 C 6 C 8 C 1 C T 1,6 1,4 1,2 1,,8 kg J,B 12 C,6,4 6 4,2 2, -,2-2 -,4-4 -,6-6 -,8-2 koe ka/m H -8 B/ μ o H VACODYM 745 AP -1, -1,5-2, -4, T 1,6 1,4 kg ,5 2 C 6 C 8 C 1 C 1,2 1,, J,B 12 C,6,4,2, -,2 -,4 -, ,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature 2

21 VACODYM 764 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 764 TP -1, -1,5-2, -4, T 1,6 1,4 kg ,2 12 J,B -,5 2 C 6 C 8 C 1 C 12 C 1,, C,6,4 6 4,2 2, -,2-2 -,4-4 -,6-6 -,8-2 koe ka/m H -8 B/ μ o H VACODYM 764 AP -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 2 C 6 C 8 C 1 C 12 C 1,, C,6,4,2, -,2 -,4 -, ,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature 21

22 VACODYM 776 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 776 TP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 6 C 8 C 1 C 12 C 15 C 1,,8 1 8, C,4,2, -,2 -,4 -, ,8-2 koe ka/m H -8 B/ μ o H VACODYM 776 AP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 6 C 8 C 1 C 12 C 15 C 1,,8 1 8, C,4,2, -,2 -,4 -, ,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature irreversible losses (%) Temperature C 2 VACODYM 776 TP -5 B/μ H = -,

23 VACODYM 51 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 51 HR -1, -1,5-2, -4, T 1,6 1,4 kg ,5 2 C 6 C 8 C 1 C 1,2 1,, J,B, C,4,2 4 2, -,2-2 -,4-4 -,6-6 -,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature 23

24 VACODYM 633 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 633 HR -1, -1,5-2, -4, T 1,6 1,4 kg ,2 12 J,B -,5 2 C 6 C 8 C 1 C 12 C 1,, C,6,4 6 4,2 2, -,2-2 -,4-4 -,6-6 -,8-2 koe ka/m H -8 B/ μ o H VACODYM 633 AP -1, -1,5-2, -4, -,5 2 C 6 C 8 C 1 C C T 1,6 1,4 1,2 1,,8,6,4,2, -,2 -,4 -,6 kg J,B -,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature 24

25 VACODYM 655 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 655 HR 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 6 C 8 C 1 C 12 C 15 C 1,,8 1 8, C,4,2, -,2 -,4 -, ,8-2 koe ka/m H -8 B/ μ o H VACODYM 655 AP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 6 C 8 C 1 C 12 C 15 C 1,,8 1 8, C,4,2, -,2 -,4 -, ,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature 25

26 VACODYM 669 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 669 TP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 8 C 1 C 12 C 15 C 18 C 1,, C,6,4,2, -,2 -,4 -, ,8-2 koe ka/m H -8 B/ μ o H VACODYM 669 AP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 8 C 1 C 12 C 15 C 18 C 21 C 1,,8,6, ,2 2, -,2-2 -,4-4 -,6-6 -,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature 26

27 VACODYM 677 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 677 HR 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 1 C 12 C 15 C 18 C 1,,8, C,4,2, -,2 -,4 -, ,8-2 koe ka/m H -8 B/ μ o H VACODYM 677 AP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 1 C 12 C 15 C 18 C 1,,8, , C,2, -,2 -,4 -, ,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature 27

28 VACODYM 688 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 688 TP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 12 C 15 C 18 C 21 C 1,,8, C,4,2, -,2 -,4 -, ,8-2 koe ka/m H -8 B/ μ o H VACODYM 688 AP -,5 2 C -1, -1,5-2, -4, 12 C 15 C 18 C 21 C 24 C T 1,6 1,4 1,2 1,,8,6,4,2, -,2 -,4 -,6 kg J,B -,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature 28

29 VACODYM 837 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 837 TP -1, -1,5-2, -4, T 1,6 1,4 kg ,2 12 J,B -,5 2 C 6 C 8 C 1 C 12 C 15 C 1,,8 1 8,6 6,4 4,2 2, -,2-2 -,4-4 -,6-6 -,8-2 koe ka/m H -8 B/ μ o H VACODYM 837 AP -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 2 C 6 C 8 C 1 C 12 C 15 C 1,,8 1 8,6 6,4 4,2 2, -,2-2 -,4-4 -,6-6 -,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature irreversible losses (%) Temperature C 25 VACODYM 837 TP -5 B/µ H = -,

30 VACODYM 854 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 854 TP -1, -1,5-2, -4, T 1,6 1,4 kg C 1,2 12 J,B -,5 6 C 8 C 1 C 12 C 15 C 18 C 1,,8 1 8,6 6,4 4,2 2, -,2-2 -,4-4 -,6-6 -,8-2 koe ka/m H -8 B/ μ o H VACODYM 854 AP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 6 C 8 C 1 C 12 C 15 C 18 C 1,,8 1 8,6 6,4 4,2 2, -,2-2 -,4-4 -,6-6 -,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature irreversible losses (%) Temperature C 25 VACODYM 854 TP -5 B/µ H = -,

31 VACODYM 863 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 863 TP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 8 C 1 C C 18 C 1,, C,6,4,2, -,2 -,4 -, koe ,8-8 ka/m H B/ μ o H VACODYM 863 AP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 8 C 1 C 12 C 15 C 18 C 1,, C,6,4,2, -,2 -,4 -, koe ,8-8 ka/m H Typical irreversible losses at different working points as a function of temperature irreversible losses (%) Temperature C 25 VACODYM 863 TP -5 B/ H = -,

32 VACODYM 872 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 872 TP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 1 C C 18 C 1,,8, , C,2, -,2 -,4 -, ,8-2 koe ka/m H -8 B/ μ o H VACODYM 872 AP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 kg J,B -,5 1 C C 18 C 1,,8, , C,2, -,2 -,4 -, ,8-2 koe ka/m H -8 Typical irreversible losses at different working points as a function of temperature irreversible losses (%) Temperature C 25 VACODYM 872 TP -5 B/ H = -,

33 VACODYM 89 Typical demagnetization curves B(H) and J(H) at different temperatures B/ μ o H VACODYM 89 TP -1, -1,5-2, -4, T 1,6 1,4 kg C 1,2 12 J,B -, C 18 C 21 C 1,,8 1 8,6 6, C,2, -,2 -,4 -, ,8-2 koe ka/m H B/ μ o H VACODYM 89 AP 2 C -1, -1,5-2, -4, T 1,6 1,4 1,2 1,,8 kg J,B C 18 C 21 C,6 6, C,2, -,2 -,4 -, ,8-2 koe ka/m H Typical irreversible losses at different working points as a function of temperature irreversible losses (%) Temperature C 25 VACODYM 89 TP -5 B/ H = -,

34 4.2.2 SINTERED MAGNETS ON A Sm 2 Co 17 BASE VACOMAX 24 Typical demagnetization curves B(H) and J(H) at different temperatures Typical irreversible losses at different working points as a function of temperature 34

35 VACOMAX 225 Typical demagnetization curves B(H) and J(H) at different temperatures AP Typical irreversible losses at different working points as a function of temperature 35

36 4.2.3 SINTERED MAGNETS ON A SmCo 5 BASE VACOMAX 2 Typical demagnetization curves B(H) and J(H) at different temperatures HR Typical irreversible losses at different working points as a function of temperature 36

37 VACOMAX 17 Typical demagnetization curves B(H) and J(H) at different temperatures Typical irreversible losses at different working points as a function of temperature 37

38 VACOMAX 145 Typical demagnetization curves B(H) and J(H) at different temperatures Typical irreversible losses at different working points as a function of temperature 38

39 4.3 TEMPERATURE DEPENDENCE AND MAGNETIC LOSSES The magnetic properties of permanent magnets are governed by the application temperature. The typical demagnetization curves of VACODYM and VACOMAX at different temperatures are shown on the relevant alloy pages (see pages 19-38). When selecting a material and the dimensions of a magnet, the characteristic magnetic values and the temperature dependence must be considered (see section 1.1 of appendix Technical Principles and Terms ). The temperature dependence of the demagnetization curves causes changes in the flux density, commonly referred to as magnetic losses. These losses fall into two main categories: Reversible losses and irreversible losses. The latter result from demagnetization of small areas of the magnet in opposing fields and/or a rise in temperature, as well as changes in the micro-structure. Reversible changes in the flux density are attributed to the temperature dependence of the saturation polarization and are solely a function of alloy composition. They are described by the temperature coefficient of the remanence; the mean value for each material is given in Table 1 and 2, resp. If an application calls for temperature compensation, we recommend the use of a magnetic shunt made of THERMOFLUX. This achieves temperature coefficients l TC l <.1%/K in systems with slightly reduced flux values in the range from 2 to 1 C. Irreversible losses owing to demagnetization processes are dependent on the load line of the magnet and the maximum application temperature. The typical irreversible losses to be expected for the various material types at different load lines B/µ o H are given in the applicable data sheets. Irreversible changes can largely be avoided by means of a stabilization process (aging). To obtain the optimum stabilization conditions for each application users should contact VAC. As a rule, it is adequate to heat the magnets to slightly above the maximum application temperature for approximately one hour. This pre-treatment achieves good stabilization but at the expense of the flux density which is reduced accordingly by the irreversible changes. The losses caused by magnetization reversal in small areas of the magnet can be eliminated by remagnetization. The maximum continuous application temperatures are primarily restricted by the reduction in the magnetic properties (see Tables 1 and 2). To avoid undesired irreversible changes in the microstructure which cannot be remedied by remagnetization, VACODYM magnets must not be heated to above 35 C and VACOMAX magnets not above 4 C. Chemical reactions with the immediate atmosphere or contact materials (e.g. glues) must be prevented. This applies especially to reactions with potential hydrogen production (see section 5.1). Radioactive radiation for a longer time can cause irreversible magnetic losses. VACOMAX can be used at temperatures down to that of liquid helium. When using VACODYM below approx. 15 K our technical staff should be consulted. 39

40 4.4 MAGNETIZATION Full magnetization is the precondition for achieving the typical magnetic values that are listed in Table 1 resp. 2 for the various materials. The required minimum field strengths of the inner magnetizing field H mag are obtained from the magnetization behaviour of the material in question. They are shown in Table 4, page 17, and in Fig. 6. To achieve the internal magnetizing field H mag, the given external field H ext must be increased by the value of the demagnetizing field H a which is determined by the working point: l H ext l = l H mag l + l H a l (See Section 1.1 of appendix Technical Principles and Terms.) Due to the high coercivities of VACODYM and VACOMAX the magnets can also be magnetized outside the system. As a result, handling the magnets and assembly of systems is more difficult but the actual magnetization is far easier. With VACODYM 51, 722/745 and also VACOMAX 24, care must be taken to ensure that the working point of the magnet is sufficiently above the knee of the B(H) -demagnetization curve (see section 1.1 of appendix Technical Principles and Terms ). Prior to magnetizing VACODYM and VACOMAX in a system we advise users to contact VAC. Magnets made of VACODYM and especially of VACOMAX can only be completely reversed in exceptionally high magnetic fields (> approx. 12 koe). Fig. 6: Demagnetization curves of VACODYM and VACOMAX as a function of magnetization field strenght H mag. The magnetization behaviour of VACODYM and VACOMAX of the SmCo 5 type (Figs. a and b) is based on the so-called nucleation mechanism. This easy magnetization is only possible from the thermally demagnetized state. The pinning mechanism is characteristic for the VACOMAX type Sm 2 Co 17 (Figs. c and d). VACOMAX 24 is very easy to magnetize compared with VACOMAX 225. This is achieved by a special heat treatment. a) Magnetizing field strength (ka/m) 4

41 Magnetizing field strength (ka/m) Magnetizing field strength (ka/m) Magnetizing field strength (ka/m) 41

42 5. CORROSION BEHAVIOUR, SURFACE PROTECTION AND COATINGS 5.1 CORROSION BEHAVIOUR Due to their strongly negative electrochemical standard potential (E = 2.2 to 2.5 V) rare-earth (RE) elements belong to the group of non-precious and thus highly reactive elements. Their chemical reactivity is similar to that of alkaline earth metals, like magnesium. Under normal conditions, the RE metals react slowly. Under conditions at higher temperatures and the presence of water or humidity, the reaction is more rapid, RE-hydroxide is formed and hydrogen is set free. The released hydrogen can then react with the free RE metal forming RE metal hydrides. By adding an adequate amount of more noble elements such as, for example, cobalt, the reaction with water can be almost suppressed. The reaction rate is negligible. This is the back-ground to VACOMAX (SmCo 5 or Sm 2 Co 17 ) only exhibiting a slight surface discolouration when exposed to high humidity (e.g. >8 % relative humidity) and increased temperature (e.g. >8 C). No significant amount of corrosion products was measured even after long exposure (e.g. >1 h). 95 % humidity and 2.6 bar). This in turn leads to a high corrosion rate and debris, which is neodymium hydroxide, and also to magnet dust (loose Nd-Fe-B grains). Sections 5.2 to 5.4 describe means of protecting these materials effectively in corrosive operating conditions. The second generation of VACODYM materials such as for example the 6-series and 8-series alloys no longer feature this corrosion mechanism. Additions of carefully selected suitable materials (including cobalt) to the neodymium-rich phase have improved their corrosion behaviour and systematically stopped intergranular corrosion in a warm, humid atmosphere. The corrosion behaviour of such VACODYM alloys is similar to that of pure iron materials (steel). In the HAST test even after several weeks exposure the corrosion rate can hardly be measured. There is merely a dark grey shimmer to the material surface. In cases where the humidity turns to condensation, VACO- DYM materials gradually begin to rust, similarly to parts made of iron (red rust). Here the corrosion products are mainly non-magnetic metal oxides or hydroxide. In applications where dew formation occurs regularly (condensation), and/or the parts are to be used in water or other corrosive media, we recommend coating. The situation is in general different with Nd-Fe-B magnets. The individual magnet grains are held together mechanically and fixed to each other by the so-called neodymium-rich phase. This phase represents up to 5 % of the total volume of the material and from a chemical point of view behaves like pure neodymium. As a result, a relatively rapid intergranular decomposition of the magnet (see Fig. 7) sets in under high humidity and temperature (e.g., in the so-called HAST Highly Accelerated Stress Test acc. IEC at 13 C / 42

43 8XX 6XX Weight loss VACODYM 7XX Exposure time (days) Fig. 7: Weight loss of VACODYM magnets in a HAST-Test similar to IEC (13 C; 95 % relative humidity; 2.6 bar in vapour) 5.2 SURFACE PROTECTION Permanent magnets made of VACODYM and VACOMAX can be used in normal ambient conditions (such as room temperature, humidity up to 5 %, no condensation) without special additional surface protection. However, the magnet surface has to be coated for many applications. There are three main reasons for this: CORROSION PROTECTION RE-permanent magnets are frequently exposed to chemically aggressive media such as acids, alkaline solutions, salts, cooling lubricants or harmful gases and have to be protected. In the case of VACODYM high humidity, dew formation or sweat is already sufficient to cause corrosion. We therefore recommend to handle VACODYM-magnets with suited gloves on principle. PROTECTION AGAINST MAGNETIC PARTICLES VACODYM and VACOMAX are sintered materials, thus it cannot be excluded that magnetic particles are found on the surface. In certain applications (e.g. systems with small working air gaps) loose magnetic particles may affect the function and/or destroy the magnet assembly. Coating ensures that the magnets can be cleaned thoroughly and will be free of all deposits. HANDLING PROTECTION Magnets are frequently mechanically stressed during assembly or operation in an assembly. In some circumstances, this may lead to chipping, sharp edges are a particular risk. Each application of VACODYM and VACOMAX must be chekked as to whether coating is necessary and how the surface is to be protected. We have tested the behaviour of our permanent magnets under widely varying conditions and will be pleased to advise you on the appropriate coating for your application. 43

44 5.3 TYPES OF COATINGS The coatings can be divided into two basic groups: metallic and organic. To meet special requirements and on request, double coatings of metal/metal & metal/varnish and a number of special coatings are available. METALLIC COATINGS As a rule, galvanic processes are used for metallic coating. Apart from our standard nickel or tin coating, on request we offer double coating nickel + tin. In addition IVD (Ion Vapour Deposition)-Aluminium coating is also possible. When selecting the type of metallic coating, the possibility of galvanic element formation in the assembly must be taken into account, as long as dew formation cannot be excluded. ORGANIC COATINGS For this case we offer different spray coatings with excellent corrosion protection characteristics. Cost-effective alternatives to metallic coatings are especially aluminium spray coatings as well as the newly developed VACCOAT epoxy resin coating. 5.4 DESCRIPTION OF THE COATINGS The majority of all applications are covered by our coatings galvanic tin, galvanic nickel, electro-painting and IVD aluminium coating as well as the recently introduced VACCOAT spray coatings introduced. The properties of the coatings complement one another. All galvanic coating processes and the spray coatings are applied at VACUUMSCHMELZE. The described properties can only be achieved in a carefully controlled system which takes into consideration the microstructure of the magnets, the mechanical processing/machining, cleaning and coating. IVD aluminium coating is performed by a subcontractor selected and qualified by VAC with great care. Appropriate quality assurance measures ensure continuity of quality in series production. Using the latest automating technology, all other coatings are applied by VAC in-house cost-effectively and with high reproducibility as well as quality. GALVANIC TIN Galvanic tin coating provides good corrosion protection against atmospheric influences, humidity as well as weak acids and alkaline solutions. The tin coating applied at VAC is dense and free of interconnected pores. The typical coating thickness range for magnets is 15 3 µm. The finish of tin coating is silvery-white and slightly glossy. No phase transitions occur between 4 C and the melting point of 232 C. The deposition process is optimized by VAC for RE magnets especially to preclude hydrogen damage to the surface of the magnet during coating positively. Small parts can be coated economically in a barrel. Larger parts are galvanized in a rack. The decision on which method to use is governed by the weight of the part and/or the geometry (typical nominal values: <25 g barrel; >25 g rack). The special merits of tin coatings are their high resistance to environmental influences (e.g. 85 C/85 % relative humidity) as generally specified for electronic applications. Tin is highly ductile and is almost free of internal stresses over a wide coating thickness range, moreover the process is highly reliable. There is no risk of cracking or flaking. Mechanical stress does not lead to chipping but merely to deformation of the tin coating so that the magnetic material is still protected safely. After thorough cleaning the tin coating is free of all residues and thus provides an ideal surface for many adhesives. 44

45 GALVANIC NICKEL Galvanic nickel coatings can be used as an alternative to tin or as double coating in combination with tin. On VACODYM, its protection is superior to a comparable coating thickness of tin. The minimum coating thickness that we recommend for protection against corrosion is 1 µm for nickel coating in comparison with 15 µm for tin coating. Galvanic nickel coatings are hard, abrasion-proof and can be cleaned without difficulty and without residues. Therefore these coatings have prevailed today, especially for clean room applications. VAC has a special nickel coating process which supplies optically attractive semibright coatings. Compared with customary bright nickel methods, such as are frequently used for rare earth magnets, our process has the following advantages: a) The coatings have high ductility and therefore show a clearly lower tendency to mechanical damage in the edge area on impact of shock. This leads to more reliable production both in the plating process and during assembly. Even parts of 5 g in weight can still be coated by barrel plating with suitable geometry. Coating in a rack is possible for heavier parts. b) When glued, clearly better adhesive strengths are achieved than with bright nickel coating because of the increased surface roughness. c) The process exhibits a very homogenous coating thickness distribution over a wide current density range, so that the so-called dog-bone-effect (excessive coating build-up in the edge/corner area) is minimized. Dimensional tolerances for thin flat parts of ±5 µm (including machining) can thus be achieved reliably in production (comparable with galvanic tin coating). d) The risk of stress cracks under thermal loading is low. The reasons for this are the better ductility as well as the extremely low internal stresses of the coating. All these properties make galvanic nickel a universal coating for RE permanent magnets covering many applications. DOUBLE COATING NICKEL + TIN Especially high corrosion resistance is attained when tin coating is applied on top of a layer of nickel. The lifetime of this double coating under environmental test conditions (e.g. 85/85 test) is twice that of nickel or tin coatings of the same thickness. The surface properties are equivalent to those of tin coating. IVD ALUMINIUM IVD (= ion vapour deposition) aluminum ensures excellent corrosion protection both in a humid climate and in exposure to salt spray. The cathodic protection by the aluminum coating enables, for example, continuous use in water. Further, owing to the electrochemical protection provided by the aluminium small imperfactions in the coating do not affect the corrosion resistance in any perceivable way. Since aluminum can be used in principle up to approx. 5 C, all applications of RE permanent magnets are thus covered. The corrosion resistance of this coating is improved further by subsequent surface passivation. Because of the high ductility of the coating, mechanical loads only cause deformation of the coating similar to that with tin, without the protective effect being impaired by damage to the coating. In comparison to electroplated zinc layers, which are also used as cathodic protection for Nd-Fe-B, the IVD-aluminium has the following advantages: extremely high temperature resistance no hydrogen embrittlement during coating process no formation of loose white rust in corrosive atmosphere very good HAST resistance. Small parts (up to 25 g) are coated in a cost effective barrel process. Heavy parts are handled as rack goods. Processincluded contact marks are prevented by special handling. 45

46 ALUMINIUM SPRAY COATING VACCOAT The stove-enamel finish filled with aluminium flakes shows similar resistance to climatic or salt spray tests like IVD aluminium. Even magnets with a coating thickness of only 5 µm withstand longterm autoclave and salt spray tests. Compared to other spray coatings our new coating provides a superior edge protection. The coating is suitable for applications up to utilization temperatures of up to 18 C in continuous application. Due to the excellent hardness of this stove enamel finish (typical 6-8 H pencil hardness) Al-spray coating is not sensitive to mechanical damage. For parts > 1 g the coating is applied in an automatic spray coating machine which ensures high reproducibility and process safety as well compliance with strict dimensional tolerances. An automatically controlled and very cost-effective barrel-plating process is available for small parts. cured it can be a high-strength adhesive. A high-strength adhesive bond forms during stoving giving a shear strength of typically >15 N/mm 2. At the same time the system is protected effectively from corrosion by the coating. The attained corrosion protection is comparable to aluminium spray coating. The stoved coating has a pencil hardness of at least 4H and can be thermally stressed to approx. 2 C. Optically high-quality finish layers of between 5 µm and 4 µm can be applied in one operation. The coating colour is selectable (the standard colour is black). The coating is abrasion-resistant and exhibits very good electrical insulation behaviour. Similarly to aluminium spray coating the layers can be applied to the magnets either in a continuous automatic process or in a barrel-plating process. The Aluminium spray coating is also of great benefit in the coating of complete magnet systems. As a rule, any residual adhesive can be permanently covered by our spray coating. In contrast to IVD aluminium coating this coating is not electrically conductive. EPOXY SPRAY COATING VACCOAT This coating recently developed in-house sets new standards regarding corrosion protection, temperature resistance, coating application and the subsequent processing of coated magnets into systems. When cured VACCOAT 211 provides high-grade corrosion protection on VACODYM. At the same time when the coating film is not yet Micrograph of coverage with VACCOAT 147 at the edge of a magnet 46

47 TEMPORARY CORROSION PROTECTION/ SURFACE PASSIVATION To protect uncoated magnets temporarily, e.g. during transport or storage, we have developed a passivation method. This protects our RE-magnets, including the more corrosion sensitive VACODYM, sufficiently against temporary environmental influences such as a rise in humidity. With this standard procedure our magnets can be stored under normal ambient conditions providing condensation can be excluded. PROPERTY PROFILE OF DIFFERENT COATINGS Table 5 compares the properties of the most important coatings and should be used as a guideline when selecting surface protection for an application. It gives the minimum layer thickness of the various coatings and ensures adequate corrosion protection in the majority of applications. To meet more stringent requirements on corrosion protection, the layer thickness must be adjusted accordingly. Please note that improper handling may well harm the coating. Table 5: SURFACE COATINGS Surface Method Min. layer Colour Hardness Resistance Temperature Typical thickness for to range application corrosion examples protection tin (Sn) galvanic > 15 µm silver HV 1 1 ) humid atmosphere, < 16 C electric motors, bright solvents sensor technology mechanical engineering nickel (Ni) galvanic > 1 µm silver HV 35 1 ) humid atmosphere, < 2 C clean-rooms, semibright solvents, small-sized motors, cooling lubricants linear motors, UHV undulators Ni +Sn galvanisch Ni > 5 µm silver HV 1 1 ) humid atmosphere, < 16 C hot water meters, Sn > 1 µm bright solvents, use in fuel (biodiesel) cooling lubricants, salt spray test Aluminium IVD > 5 µm silver semibright HV 2 1 ) humid atmosphere, < 5 C electric motors, passivated (chromium VI salt spray test, sensor technology, free), yellow solvents aeronautic semibright applications (yellow chromated) aluminium automatic > 5 µm yellow > 4H 2 ) humid atmosphere, < 18 C electric motors, spray coating spray coating semibright spray test, generators, VACCOAT toxic gas test, sensor technology, 147 solvents linear motors, motorcars epoxy automatic > 1 µm black 3 ) 4H 2 ) humid atmosphere, < 2 C segmented magnet spray coating spray coating salt spray test, systems, electric motors, VACCOAT toxic gas test, linear motors, 211 solvents motorcars 1) Vickers hardness (nominal values) 2) Pencil hardness 3) other colours possible 47