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Quality Control of Magnetic Powders and Magnets


The Quality Control of Magnetic Powders and Permanent Magnets Produced with use of a Technology and Equipment Formerly Applied for the Manufacturing of Nuclear Weapons

Tech Area / Field

  • INS-MEA/Measuring Instruments/Instrumentation

3 Approved without Funding

Registration date

Leading Institute
GO Spetzmagnit, Russia, Moscow

Supporting institutes

  • All-Russian Scientific Research Institute of Non-Organic Materials named after A. Bochvar, Russia, Moscow


  • Gorham / Intertech Consulting Company, USA, CT, Sanday Hook\nPioneer Metals and Technology, Inc., USA, MA, Boston\nNational Instruments, USA, TX, Austin\nPurdue University Calumet, USA, IN, Hammond\nMagnetic Instrumentation, Inc., USA, IN, Indianapolis\nLDJ Electronics Corporation, USA, MI, Troy\nWalker Scientific Inc., USA, MA, Worcester

Project summary

The global production of Nd-Fe-B bonded magnets (BM) on the base of fast quenched magnet powders (FQMP) with a binder is in rapid progress and, according to estimations of experts, will increase three times as much by 2006 and reach in cost expression 7 milliards of US dollars [1].

The Nd-Fe-B FQMP and BM manufacturing method is complicated and intensive. An achievement of a high and stable quality of the production is a priority trend in the market strategics of large-scale BM producers [2].

An assurance of a flawless production can be achieved only thanks to a quality control by the every technological operation. Introduction into practice such criteria as homogeneity or specified distribution of magnetic properties over the BM volume takes on special significance. These are additional BM characteristics, which any deflections can not be revealed by means of conventional methods for BM testing.

The control of the manufacturing method for the assurance of the homogeneity of BM properties can ensure a diminution of economical losses by 3 to 4 %, i.e. up to $3,000 per metric ton of BM at the price of $80 per kg. The rejection of Nd-Fe-B BM with a heightened inhomogeneity of magnetic properties in proper time before the complete setting and assembling of articles can result in a diminution of economical losses of the user up to $10,000 per metric ton of BM.

The Project as a whole is intended at an achievement of a high and stable quality by Nd-Fe-B FQMP and BM and particularly at the creation of a modern System of quality control by their manufacturing according to requirements of international standards ISO series 9000.

The Nd-Fe-B FQMP and BM have substantial magnetic, physical and technological properties [3]. They call for the original theoretical and experimental researches and new technical solutions by development of new techniques and appropriate instruments for their testing and the quality control.

A consideration of the available quality control of cast magnetic alloys and FQMP in the Nd-Fe-B system was revealed an insufficiency of the chemical composition control . On the Phase One of the Project the technique for the quantitative phase analysis of three-component and complex Nd-Fe-B magnetic alloys with the application of the method of nuclear gamma resonance (NGR) was elaborated.

It was shown that for securing of a reliable control of the phase composition of complex Nd-Fe-B magnetic alloys the application of the X-ray diffraction method would be expedient. However by Nd-Fe-B magnetic alloys it calls for elaboration of a new approach and algorithm, realized by means of modern computer technologies.

At the same time, it was revealed a necessity of a search of new criteria enabling to determine properties of Nd-Fe-B magnetic alloys with the most completeness and to estimate their suitability for manufacturing of permanent magnets.

A conventional quantitative analysis of the crystal texture formed in sintered magnets made of Nd-Fe-B alloys is extremely labour-intensive and protracted. Therefore, on the Phase Two of the Project one supposes to elaborate new technique for the quality control of the texture in sintered magnets by use of the X-ray diffraction method, ensuring a sufficient precision and efficiency of the analysis in the same time.

The temperature coefficients of the magnetic induction (TCB) of BM and other permanent magnets apply to important magnetic parameters that determine conditions for production usage. They depend both on physical properties of magnetically hard materials and structural features of articles and determine in many respects their quality, reliability and applicability. The available techniques for TCB measuring do not ensure a necessary precision by measurements, particularly by testing of new BM with small values of TCB (for instance on the base of Nd-Fe-B magnetic alloys with additions).

On the Phase Two of the Project it is stipulated the development of a technique of precision measurements of TCB of BM and other permanent magnets by raised temperatures on the base of magnetic comparators with the use of the method of the nuclear magnetic resonance.

The measurements of the magnetic induction of sharply inhomogeneous magnetic fields are urgent in connection with an increasing output of BM and other permanent magnets of complex forms or with a complex magnetic texture, particularly by multipole rotor and stator magnets. The latest achievements in the area of the technology of growing of semiconductor crystals and the creation of high-sensitive Hall microsensors for measurement of magnetic field parameters (State University “Lvovskaya Politechnika”, Ukraine) enable to produce multicomponent units of magnetic sensors. Their application in combination with the hardware and software of modern personal computers enables the creation of new technique for measurements of inhomogeneous magnetic fields.

Based on the elaborated on the Phase One of the Project conception of the advanced standardization and the measurement assurance of the testing of magnetically hard materials and permanent magnets [4], the certification standards and reference specimens of the composition of Nd-Fe-B FQMP and BM are intended to be developed on the Phase Two of the Project.


1. W.G.Hart, Market Forecast Trends and Structure of Bonded Magnets, Bonded Magnets’99 Symposium, Tokyo, Japan, December, 1999.

2. Мaterials of International Conference of Manufacturers and Consumers of Permanent Magnets, Atlanta, USA, 1996.

3. A.S.Lileev, V.P. Menushenkov, A.M. Gabay, J.Magn. Magn. Materials, 1992.

4. P.A. Kurbatov, A.S. Lileev, I.D. Podolsky, The Actual Problems of the Standardization of Magnetically Hard Materials and Permanent Magnets, 15th Int. Workshop on RE Magnets and their Application, Dresden, Germany, 1998.