RU2533068C1 - Production of iron-chromium-cobalt-system-based magnetically hard alloy powders - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: mix containing powders of iron, chromium, cobalt; alloying additives and up to 15 wt % of iron, chromium, cobalt nanopowders are formed to get the billets. The latter are sintered and heat treated including thermo magnetic processing.

EFFECT: lower sintering temperature and accelerated sintering.

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Description

The invention relates to the field of powder metallurgy in terms of technology for producing permanent magnets from hard alloys of the iron-chromium-cobalt system by powder metallurgy methods.

Known methods for producing magnetically hard alloys of the iron-chromium-cobalt system by powder metallurgy methods, including mixing powders of iron, chromium, cobalt and alloying additives, molding to obtain powder blanks of permanent magnets, their sintering in vacuum (or in a protective atmosphere) at temperatures 1350-1420 ° C, heat treatment, including thermomagnetic, to obtain the final magnetic hysteresis properties.

The method of US patent No. 4401482 (1983) "Fe-Cr-Co magnets by powder metallurgy processing" includes the use of organic binders of a certain class (surfactants) in an amount of 1-3%, which are then removed at temperatures up to 600 ° C in the process of sintering the molded billets. The disadvantage of this method of producing powder magnetically hard materials of the Fe-Cr-Co system is the very use of organic binders, which, when mechanically activated, charge the pollutants of the alloy with carbon, which is a strong γ-forming element, leading to a sharp decrease in the residual induction and the maximum energy product of magnetically hard FeCrCo alloys .

Known patent of the Russian Federation No. 2334589 C2 (2008) "A method of manufacturing magnets from powder materials based on the iron-chromium-cobalt system", which is based on the use of powders of ferroalloys of alloying elements (ferrosilicon and ferromolybdenum), providing liquid-phase sintering and thereby increasing density of the obtained permanent magnets. Unfortunately, this method of manufacturing magnets from powder materials based on an iron-chromium-cobalt system does not provide a reduction in the sintering temperature of the molded powder preforms and thus does not reduce the energy consumption for the production of permanent magnets.

The technology for producing permanent magnets from magnetically solid powder alloys of the Fe-Cr-Co system, described in detail in M.L. Green, R.C. Sherwood and S.S. Wong "Powder metallurgy processing of CrCOFe permanent magnet alloy containing 5-25 wt.% Co" (J. Appl. Phys. 1982, v. 53, No. 3, pp. 2398-2400), indicates that the optimum sintering temperature is 1400-1420 ° C, which is high enough for sintering metal alloys and requires specialized equipment.

The closest to the described invention in technical essence and the achieved result is a method for producing sintered magnetically hard FeCrCo powder alloys of US patent No. 4601876 (1986) "Sintered Fe-Cr-Co type magnetic alloy and method for producing article made thereof, the essence of which is the fact that in order to intensify the sintering process, both the initial charge powders and the precursor alloy powders introduced into the charge are mechanically activated. The disadvantages of this method for producing permanent magnet powders include the need to use Cove precursors and high-chromium alloys vysokokobaltovyh FeCrCo treated for sigma phase, which significantly complicates the entire process for producing the magnet powder.

The problem to which the present invention is directed, is to create a method for producing powder magnetic hard alloys based on the iron-chromium-cobalt system.

The technical result of the invention is to reduce the time and temperature of sintering.

The technical result of the invention is achieved by the fact that in the method for producing powder hard magnetic alloys based on the iron-chromium-cobalt system, including the preparation of a mixture containing powders of iron, chromium, cobalt and alloying elements, molding the resulting mixture, sintering, heat treatment, including thermomagnetic, according to the invention up to 15 wt.% nanodispersed powders of iron, chromium and / or cobalt are introduced into the composition of the charge used.

The essence of the present invention lies in the fact that a similar intensification of the sintering process of FeCrCo alloys is achieved by introducing into the initial powder mixture nanopowders of iron, cobalt and / or chromium in an amount of up to 15 wt.%. With the introduction of nanopowders, not only does the sintering time decrease by 1.5–2 times, but the optimal sintering temperature also decreases by 100–150 ° С due to the more developed surface of the sintering powders. Table 1 shows the magnetic hysteresis properties of the Fe-22Cr-15Co-1Ti magnetically hard alloy powder (22X15KA according to GOST 24897-81) depending on the nanopowder content in the initial powder mixture, sintering time and temperature. From table 1 it is seen that the introduction of nanopowders of the initial elements of the mixture in an amount of more than 15 wt.% Does not lead to a further decrease in temperature and sintering time, but only leads to a rise in the cost of manufactured products.

Table 1 The content of nanopowder in the original powder mixture Sintering temperature and time Residual induction B _r , T Coercive force H _cB , kA / m Max. energy product (HV) _max , kJ / m ³ 0 wt.% 1400 ° C (3 hours) 1.38 49.5 37.8 1430 ° C (4 hours) 1.35 39.6 25.7 1370 ° C (4 hours) 1.06 40.9 19.5 5 wt.% 1400 ° C (3 hours) 1.36 46.2 35.0 1400 ° C (2 hours) 1.37 49.6 38,0 1370 ° C (4 hours) 1.30 44.0 30,0 10 wt.% 1400 ° C (2 hours) 1.36 48.0 36.0 1370 ° C (2 hours) 1.39 49.0 38.7 1350 ° C (4 hours) 1.32 43.5 32.6 1320 ° C (4 hours) 1.30 40.3 29.0 15 wt.% 1370 ° C (2 hours) 1.39 47.0 37.5 1350 ° C (4 hours) 1.40 48.3 40,2 1350 ° C (2 hours) 1.41 48.8 41.2 1300 ° C (4 hours) 1.42 48.6 43,4 1300 ° C (2 hours) 1.44 48,4 45.0 1270 ° C (4 hours) 1.35 44,2 36.0 20 wt.% 1300 ° C (2 hours) 1.45 48.0 44.9 1270 ° C (6 hours) 1.36 45,2 37,4 1270 ° C (4 hours) 1.34 44,4 36.0

Claims (1)

A method for producing powder magnetic hard alloys based on an iron-chromium-cobalt system, including preparing an initial powder mixture containing iron, chromium, cobalt and alloying elements, molding the resulting mixture, sintering, heat treatment, including thermomagnetic, characterized in that the preparation of the initial mixture is introduced nanodispersed powders of iron, chromium and cobalt in an amount up to 15 wt.%.