RU2536022C1 - Method for obtaining ferritic items by radiation thermal sintering - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: charge is prepared from synthesised ferritic material and 0.01-0.05 wt % of low-melting additive preliminary mechanoactivated in planetary mill for 25-50 minutes. Obtained press-powder is used for workpieces pressing, heated to sintering temperature by radiation of penetrating electron beam and exposed at sintering temperature under radiation. During heating isothermal exposure is performed for 10-20 min at low-melting additive melting temperature.

EFFECT: reducing sintering time, improving ferrites electromagnetic capabilities.

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Description

The invention relates to powder metallurgy and can be used in the electronic and radio industries in the production of ferrite materials and products based on them.

A known method of radiation-thermal treatment (RTO) of materials, in particular products from ferrites and ceramics, provides sintering of ferrite blanks by irradiation with a penetrating pulsed electron beam (see AS USSR No. 1391808, B22F 3/24, C04B 35/26. : Surzhikov A.P., Annenkov Yu.M., Novikov BC, etc.). The disadvantage is the method is characterized by a long sintering time, does not provide the required quality of the sintering process of soft magnetic ferrite ceramics, does not provide the required quality of soft magnetic ferrites.

There is also a method of producing ferrite products (AS USSR No. 1627324, B22F 3/12, H01F 1/34. Authors: Surzhikov AP, Pritulov AM, Kozhemyakin VA, etc.), which reduces the sintering time , sintering quality.

According to the method, the synthesized ferrite material containing a low-melting additive is formed into preforms, heated by irradiation with a penetrating pulsed electron beam at a speed of 420-520 degrees per minute to the melting point of the low-melting additive, kept under irradiation and at this temperature for 10-20 minutes, after which continues radiation heating of the preforms to sintering temperature and maintain them at sintering temperature and under irradiation.

However, this method does not significantly reduce sintering time with the radiation-thermal method for producing soft magnetic ferrite ceramics, it does not provide the required quality of soft magnetic ferrites.

Fusible additives in the form of metal oxide are known to be used to improve the sintering process of ferrite ceramics (for example, Bi ₂ O ₃ , CdO; see: AS USSR No. 1627324, B22F 3/12, H01F 1/34. Authors: Surzhikov A .P., Pritulov AM, Kozhemyakin V.A. et al.). However, these additives are not without drawbacks, because they do not provide the required quality of the sintering process of ferrite ceramics, do not provide ceramics with high electromagnetic characteristics.

The purpose of the invention is to improve the sintering process of soft magnetic ferrite materials and products based on them by radiation-heat treatment, as well as to reduce sintering time during sintering by the method of radiation-heat treatment, to achieve the required parameters by the characteristics of ferrites.

This goal is achieved by the fact that the proposed method for producing ferrite products by radiation-thermal sintering, including the synthesis of ferrite material, the introduction of a refractory additive, preparation of a press powder, pressing the blanks, heating them to sintering temperature by irradiation with a penetrating electron beam and exposure to sintering temperature under irradiation the implementation of isothermal exposure during heating for 10-20 minutes at the melting temperature of the low-melting additives, characterized in that In order to reduce the sintering time of soft magnetic ferrite ceramics, to use the method for soft magnetic ferrites, as well as to improve the electromagnetic characteristics of the latter before introducing a fusible additive into the synthesized charge, they are mechanically activated in a planetary mill for 25-50 minutes and mechanically activated fusible additive is introduced into the synthesized charge in an amount 0.01-0.05 wt.% Of the total mass of the ferrite mixture.

The mechanical activation of the ferrite material synthesized in a planetary mill provides an increase in its activity during sintering, which increases the density of the material after sintering and the level of electromagnetic properties.

Method implementation examples

Example 1. Bismuth oxide was introduced into manganese-zinc ferrite powders synthesized by oxide technology, followed by preparation of a press powder with polyvinyl alcohol as a binder. K20 × 12 × 6 ring preforms obtained by pressing under a pressure of 200 MPa, after drying to a moisture content of less than 0.5 wt.%, Were subjected to PTO by applying fast electrons with an energy of 4 MeV, the pulse current value was 400 mA, and the pulse repetition rate was 50 Hz. During heating, isothermal exposure was carried out for 10 min at a temperature of 820 ° C. The minimum RT-sintering time was determined on the basis of providing a ferrite density of at least 95% of theoretical density.

We used bismuth oxide Bi ₂ O ₃ GOST 10216-75 of the “chda” grade, initial, as well as mechanically activated by grinding and mechanical activation of the powder in an APF-3 planetary ball mill. The activation time was 20, 25, 35, 50, and 75 minutes. The research results showed that mechanical activation can reduce the time of the magnetic resonance of magnetically soft ferrites by 7% until they are completely ready and increase the level of electromagnetic properties.

Table 1-4 shows the results of the dependence of the PTO time required for the complete readiness of the developed soft magnetic ferrites containing 0.03 wt.% Bismuth oxide on the time of mechanical activation in the APF-3 planetary mill. The average particle size after mechanical activation was evaluated on an LHM-8MD gas chromatograph. The values of the electromagnetic parameters were obtained from averaged data on 5 samples.

Table 1 Effect of mechanical activation time t of Bi ₂ O ₃ additive in the APF-3 planetary mill on the PTO process and saturation induction of ferrite ceramics Mn _0.603 Zn _0.274 Fe _0.124 Fe ₂ O ₄ (T _cn = 1200 ° C) t min 0 twenty 25 35 fifty 75 The average particle size of Bi ₂ O ₃ , nm 425 362 251 194 141 139 Minimum RT-sintering time required for complete ferrite readiness, min 125-130 118-121 110-114 105-112 108-117 110-119 Saturation induction in the field 240 A / m Vm, T 0.30 0.31 0.33 0.34 0.34 0.32 Note Prototype Going beyond According to the invention According to the invention According to the invention Going beyond

table 2 Effect of mechanical activation time t of Bi ₂ O ₃ additive in the APF-3 planetary mill on the PTO process and the initial magnetic permeability of ferrite ceramics Mn _0.743 Zn _0.219 Fe _0.038 Fe ₂ O ₄ (T _cn = 1200 ° C) t min 0 twenty 25 35 fifty 75 The average particle size of Bi ₂ O ₃ , nm 425 362 251 194 141 139 Minimum RT-sintering time required for complete ferrite readiness, min 120-130 118-126 111-116 105-112 108-115 112-117 The initial magnetic permeability, µ 1962 1996 2014 2211 2204 2103 Note Prototype Going beyond According to the invention According to the invention According to the invention Going beyond

Table 3 Influence of the mechanical activation time t of the Bi ₂ O ₃ additive in the APF-3 planetary mill on the PTO process and the initial magnetic permeability of ferrite ceramics Ni _0.29 Zn _0.63 Fe _2.08 O ₄ (T _cn = 1200 ° C) t min 0 twenty 25 35 fifty 75 The average particle size of Bi ₂ O ₃ , nm 425 362 251 194 141 139 Minimum RT-sintering time required for complete ferrite readiness, min 115-119 112-116 108-111 101-104 105-108 109-112 The initial magnetic permeability, µ 1843 1915 2001 2101 2084 1993 Note Prototype Going beyond According to the invention According to the invention According to the invention Going beyond

Table 4 Effect of mechanical activation time t of Bi ₂ O ₃ additive in the APF-3 planetary mill on the PTO process and the initial magnetic permeability of ferrite ceramics Mg _0.404 Mn _0.160 Zn _0.448 Fe ₂ O ₄ (T _cn = 1200 ° C) t min 0 twenty 25 35 fifty 75 The average particle size of Bi ₂ O ₃ , nm 425 362 251 194 141 139 Minimum RT-sintering time required for complete ferrite readiness, min 110-114 108-111 107-109 97-100 102-105 106-108 The initial magnetic permeability, µ 578 596 614 627 621 599 Note Prototype Going beyond According to the invention According to the invention According to the invention Going beyond

As can be seen from the data presented in Tables 1-4, the best results for PTO and the level of parameters of soft magnetic ferrite ceramics are exerted by Bi ₂ O ₃ oxide (as an alloying additive) after mechanical activation at the APF-3 planetary mill for 35 minutes. When going beyond the scope of the invention for less than 25 minutes, the PTO time increases markedly, and an increase in processing time of more than 50 minutes does not lead to a noticeable change in sintering parameters. The mechanism for improving the sintering process of ferrite ceramics in the presence of Bi ₂ O ₃ oxide is as follows. Bismuth oxide is a low-melting additive and melts even at a temperature slightly above 800 ° C. In this case, the process of sintering of ferrite with the participation of the liquid phase takes place. With the participation of the liquid phase, the sintering process proceeds more intensively. The process of mechanical activation and nanoscale state reduce the melting point of bismuth oxide, increase the contact area and chemical activity of the reaction participants in the sintering process, provide an increase in the level of electromagnetic properties.

Example 2. In synthesized by oxide technology, manganese-zinc ferrite powders, bismuth oxide was introduced, followed by preparation of a press powder with polyvinyl alcohol as a binder. K20 × 12 × 6 ring billets obtained by pressing under a pressure of 200 MPa, after drying to a moisture content of less than 0.5 wt.%, Were subjected to PTO by exposure to fast electrons of 6 MeV, the current value per pulse was 500 mA, and the pulse repetition rate was 250 Hz. During heating, isothermal exposure was carried out for 20 min at a temperature of 820 ° C. The minimum RT-sintering time was determined on the basis of providing a ferrite density of at least 95% of theoretical density.

We used bismuth oxide Bi ₂ O ₃ GOST 10216-75 of the “chda” grade, initial, as well as mechanically activated by grinding and mechanical activation of the powder in an APF-3 planetary ball mill. The activation time was 35 minutes. The research results showed that the use of the method allows 12% to reduce the time of the PTO of soft magnetic ferrites to their full readiness, to increase the level of electromagnetic properties.

Table 5-8 presents the results of the dependence of the PTO time required for the complete readiness of the developed soft magnetic ferrites containing mechanically activated bismuth oxide on its amount. The values of the electromagnetic parameters were obtained from averaged data on 5 samples.

Table 5 Effect number mechanically activated in a planetary mill additives ACE-3 Bi ₂ O ₃ in the process of the PTO and ferrite ceramics saturation induction Mn Zn _{0.603 0.274 0.124} Fe Fe ₂ O ₄ (T _cn = 1200 ° C) The content of Bi ₂ O ₃ , wt.% 0 0.008 0.01 0,03 0.05 0.06 Minimum RT-sintering time required for complete ferrite readiness, min 125-130 117-120 110-113 105-112 105-111 107-111 Saturation induction in the field 240 A / m Vm, T 0.30 0.32 0.33 0.34 0.33 0.32 Note Prototype Going beyond According to the invention According to the invention According to the invention Going beyond

Table 6 Effect number mechanically activated in a planetary mill additives ACE-3 Bi ₂ O ₃ and the process of RTO initial permeability ferrite ceramics Mn Zn _{0.743 0.219 0.038} Fe Fe ₂ O ₄ (T _cn = 1200 ° C) The content of Bi ₂ O ₃ , wt.% 0 0.008 0.01 0,03 0.05 0.06 Minimum RT-sintering time required for complete ferrite readiness, min 120-130 117-124 110-114 105-112 105-114 106-114 The initial magnetic permeability, µ 1962 1990 2006 2211 2207 2090 Note Prototype Going beyond According to the invention According to the invention According to the invention Going beyond

Table 7 Effect number mechanically activated in a planetary mill additives ACE-3 Bi ₂ O ₃ and the process of RTO initial permeability ferrite ceramics Ni _0.29 Zn _0.63 Fe _2.08 O ₄ (T _cn = 1200 ° C) The content of Bi ₂ O ₃ , wt.% 0 0.008 0.01 0,03 0.05 0.06 Minimum RT-sintering time required for complete ferrite readiness, min 115-119 110-114 106-110 101-104 101-104 101-105 The initial magnetic permeability, µ 1843 1919 2012 2101 2087 1998 Note Prototype Going beyond According to the invention According to the invention According to the invention Going beyond

Table 8 Effect number mechanically activated in a planetary mill additives ACE-3 Bi ₂ O ₃ and the process of RTO initial permeability ferrite ceramics Mg _0.404 Zn _0.160 Mn _0.448 O _4, Fe ₂ (T _cn = 1200 ° C) The content of Bi ₂ O ₃ , wt.% 0 0.008 0.01 0,03 0.05 0.06 Minimum RT-sintering time required for complete ferrite readiness, min 110-114 106-110 99-104 97-100 97-100 97-101 The initial magnetic permeability, µ 578 598 618 627 620 591 Note Prototype Going beyond According to the invention According to the invention According to the invention Going beyond

As can be seen from the data presented in Tables 5-8, the best results for PTO of magnetically soft ferrite ceramics are demonstrated with the introduction of mechanically activated oxide Bi ₂ O ₃ (as a dopant) in an amount of 0.03 wt.% When going beyond the scope of the invention less than 0.008 wt. % PTO time increases markedly, and an increase in the content of more than 0.05% does not lead to a noticeable change in sintering parameters, but can reduce the level of electromagnetic parameters. The process of mechanical activation and nanoscale state reduce the melting point of bismuth oxide, increase the contact area and the chemical activity of the reaction participants in the sintering process, which ensures an increase in the level of electromagnetic properties.

Claims (1)

A method of producing ferrite products by radiation-thermal sintering, including the synthesis of ferrite material, the introduction of a low-melting additive in the form of bismuth oxide Bi ₂ O ₃ , preparation of a press powder, pressing of blanks, heating them to a sintering temperature by irradiation with a penetrating electron beam and holding at a sintering temperature under irradiation, the implementation of isothermal exposure during heating for 10-20 minutes at the melting temperature of the low-melting additives, characterized in that before introduction into the synthesis The batch charge of the low-melting additive is mechanically activated in the planetary mill for 25-50 minutes and the mechanically activated low-melting additive is introduced into the charge in an amount of 0.01-0.05 wt.% of the total mass of the ferrite charge.