POS-Progress

Magnetically hard materials based on REM alloys with cobalt

In 1966-67, reports appeared in the press about fundamentally new high-energy hard magnetic materials based on rare-earth metal alloys ( REM ) with cobalt, which, in terms of basic magnetic characteristics, significantly exceeded the properties of known alnico magnets.

The use of rare-earth permanent magnets opened up great opportunities for reducing the size of existing magnetic systems and developing fundamentally new device designs.

These publications served as an impetus for the beginning of research on new materials in the USSR and, in particular, for conducting joint research work by the Permanent Magnet Problem Laboratory of the Ural State University and the Pyshminsky Pilot Plant, which at that time possessed technologies for producing pure rare-earth metals and smelting alloys of a given composition.

During 1968, laboratory technology was developed, and since 1969, a pilot site for the production of permanent magnets (PM) was organized at the plant.

The first magnets were compacted, not sintered, fine powders. These magnets possessed:

• energy (HV) max = 8 ÷ 9 MGs × E,
• coercive force 14 ÷ 16 kOe,
• residual induction of 0.55 ÷ 0.65 T,
• stability of properties in the range from minus 70 to plus 150 ° C,

but had low mechanical strength, and their shelf life was only 1-2 years.

In this regard, since the beginning of 1970, the plant’s specialists, scientists from the Ural State University and the Institute of Physics and Mathematics of the Ural Branch of the Academy of Sciences of the USSR conducted intensive studies to search for sintering modes for PM blanks. As a result, in August 1971, it was possible to develop an original method for sintering PM billets, and already in September 1971, POP began supplying mechanically strong magnets with a maximum magnetic energy above 15 MGs × E and an operating temperature of up to 150 ° C.

Magnets were supplied to customers in various configurations - a plate, a disk, a ring, and later on, products of a more complex shape were required - with a spherical surface, trapezoidal, sectors, etc. Therefore, various mold designs were developed at the plant that allow pressing at high pressures (up to 16 tf / cm2).

In addition, customers formulated requirements for a class of dimensional accuracy and surface finish. For machining workpieces in 1972-1973. a separate section of PM machining was organized. The first grinding machines were purchased and put into operation, grinding wheels, equipment were selected and grinding modes worked out.

The development of technology and the supply of experimental batches of magnets allowed the designers and developers of magnetic systems and devices to carry out the necessary studies on magnets that they had never encountered before, to determine their behavior under the influence of various physical influences, to optimize the parameters of magnetic systems using rare-earth PM .

To fulfill the requirements put forward by consumers, the plant entered into agreements with dozens of organizations, expanded the pilot industrial site for manufacturing PM, organized a site for the production of accessories for the manufacture of magnets (molds, non-standard equipment, etc.), which made it possible to bring the volume of manufactured magnets in 1972 to 500 kg .

In the period from 1969 to 1973 a large number of research works were carried out, many of which are protected by copyright certificates. The studies carried out significantly improved the magnetic characteristics of the products, and the introduction of the developed technologies into production led to a significant increase in the yield of products, increase in productivity and quality.

At the beginning of production, only direct (uniaxial) pressing in a metal matrix was used to form the molds of the PM (the direction of the texturing magnetic field and the pressing force coincided). However, it is known that the use of isostatic pressing (in a metal matrix with an elastic element) increases the degree of texture by 10-15%, and the magnetic energy increases by 20-25%. In this regard, equipment was developed, modes worked out, equipment was selected for “isostatic” pressing. As a result, this technology has been successfully introduced into production and is used to this day.

Magnetic Measurement Tools

One of the most important production issues is the measurement of magnetic characteristics and product certification. The first measurements were carried out using a vibromagnetometer on spherical samples made from pieces of sintered magnets. The measurement process was inefficient and rather laborious.

The plant’s specialists, in collaboration with MPEI , created an automatic hysteresis static loop recorder (ARSPG-4), which made it possible to provide more reliable and efficient certification of produced magnets. In addition, teslameters were equipped with which magnetic induction was measured on the surface of the magnets and in the center of the ring magnets. After the introduction of installations for measuring the magnitude of the flux linkage of the magnet field with Helmholtz coils, the produced magnets began to undergo reliable 100% control.

The first PMs were magnetized in an electromagnet, which often led to incomplete magnetization of products. Therefore, in accordance with the increasing requirements of production, the plant’s specialists developed a design, and then fabricated and mounted a device for magnetizing PM with a pulsed magnetic field, the value of which reached 60 kOe.

As a result, by the beginning of the 80s, a stably working production was formed, located on an area of ​​more than 1,000 m2, producing several tons of permanent magnets based on the SmCo5 (KS-37) alloy with a magnetic energy of 14-23 MGs × E per year.

The beginning of the second stage in the development of the production of permanent magnets dates back to 1980-1983. During this period, the plant’s specialists, in close collaboration with USU scientists, conducted research on the development of a technology for producing magnets based on the Sm2Co17 alloy (KS25DC) with alloying additives.

This alloy turned out to be more profitable both from an economic point of view and from the point of view of magnetic characteristics: the samarium content in it is 32%, and cobalt is 21% less than in the KS-37 alloy, and the magnets from this alloy had greater magnetic energy and temperature stability.

Between 1981 and 1984 work was carried out to optimize the technological regimes for producing magnets at all stages of production: smelting alloys, grinding, sintering and heat treatment, production was launched with a magnitude (HV) of max up to 32 MGs × E.

Mastering the production technology of PM based on Nd-Fe-B alloy

Another important stage in the development of production was the development of PM production technology based on the Nd-Fe-B alloy.

The absence of cobalt in the composition can reduce the price of rare earth magnets by 2-3 times and significantly expand their scope.

Based on publications in the press and research carried out in the Permanent Magnet Problem Laboratory of the Ural State University under the direction of A. V. Deryagin , for the first time in the country, the plant’s specialists made magnets from Nd-Fe-B alloy.

In a relatively short period of time, the technology was developed and in 1985 the production of PM for consumer goods began, in particular, for speakers and microelectric motors.

The proven technology served as the basis for the production of magnets at the Mayak Chemical Plant ( Ozersk ) and the Siberian Chemical Plant ( Seversk ).

An essential step in expanding the assortment was the production of PM with a low temperature coefficient of induction, both on the basis of KS-37 alloy and on the basis of KS25DC (TKI = | - 0.02% / С ° |). The use of such PMs in the magnetic systems of devices made it possible to significantly reduce their overall dimensions.

The production of new types of products has always been accompanied by the development and design of technical conditions.

In 1991, the permanent magnets section of the Pyshminsky Pilot Plant was set aside as an independent enterprise with the name "POS-Progress" ^[3] .

The company is constantly updating equipment and improving technology. In particular, in 2005-2006, two imported sintering furnaces were purchased and put into operation. Dry powder grinding plant was commissioned. A cutting section for press billets and a section for preparing raw materials for smelting alloys were organized, which made it possible to increase productivity.

Improving the technology has allowed to increase the operating temperature of magnets from the Nd-Fe-B alloy to 180 ° С and to 450 ° С КС25ДЦ.

The production of ring magnets with a radial texture has been mastered.

In addition to the production of magnets, he is engaged in the development and manufacture of devices and mechanisms using them, for example, magnetic separators.

Magnet systems with a field strength of up to 26 kOe have been obtained on the basis of in-house magnets.

• Vyacheslav Nikolaevich Beketov (1950-2017) - from 1988 to 2017 he worked as a technologist, deputy. shop manager, chief technologist ^[4] .

The production of high-temperature permanent magnets (HTSC) up to 500 ° С based on Sm-Co-Fe-Cu-Zr ^[5]

Together with Spetsmagnet LLC it produces about 12 tons of permanent magnets per year. In 2012, the State Program "Technology of rare and rare-earth metals" was adopted, the main task of which is to develop deposits of such metals and implement new technologies for their application, including to increase the production of magnets ^[6]

•   POS-Progress
• Market review of rare earth magnets in Russia (neopr.) . Infomine Research Group (2015). Date of appeal September 15, 2019.