JPS60239204A - Wet type molding method of ferrite powder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

Go to 11” Jiang

[Industrial application field]

The present invention relates to a method for wet molding ferrite powder.
This method is particularly significant when applied to the manufacturing process of sintered ferrite magnets.

[Conventional technology]

In the production of ferrite magnets, when molding a powder compact to be sintered using a wet method, a slurry of ferrite powder is generally fed into a mold with a filter sheet placed on the surface having water permeable holes, and then filtered and pressed. A method of molding is used. Conventionally, woven fabrics (usually twill weave) of natural or synthetic fibers have been used as filter sheets. - In order to manufacture high-performance magnets, it is first necessary to create a powder compact with a high bulk density, which requires - several hundred
The filtration press must be carried out at a high pressure of ka/CIl+2. However, the pressure of the filtration press is 400 to 500 kQ/
If the temperature is increased above 0.012, the filter sheet will become clogged with ferrite particles in the slurry, the amount of water removed will decrease, and the packing density of the molded body will become lower, and the slurry will leak out from the filter seal. A problem arises, which defeats the purpose of obtaining a powder compact with a high bulk density. This leads to the occurrence of cracks when the molded body is sintered in the subsequent process, resulting in a disadvantage that the product yield is reduced.

[Problems to be solved by the invention]

The purpose of the present invention is to wet mold ferrite powder,
It is an object of the present invention to provide a molding method that avoids clogging of the filter sheet and obtains the result of pressing at high pressure.
As a result, it is also possible to manufacture a ferrite magnet in which the occurrence of cracks is suppressed to zero or to a minimum during sintering of a powder compact. 11 starvation 1

[ [Means to solve the problem]

The wet molding method of ferrite powder of the present invention comprises supplying a slurry of ferrite powder into a mold cavity in which a filter sheet is laid on the surface of the water permeable hole, and performing filtration press molding. It is characterized by the use of non-woven felt.

[Effect]

When we investigated the cause of clogging in conventional filter sheets, we discovered that the bundles of threads woven into the cloth are crushed due to high cavity pressure, and the inter-thread porosity, or the area of the unit area that is not occupied by threads, is reduced. This was thought to be due to the decrease in water content, making it difficult for water to pass through the slurry. Therefore, if a synthetic fiber non-woven felt is used as a filter sheet according to the present invention, the fibers are not bundles of thin threads but single Ila fibers, so even if the fibers are crushed to some extent by the high pressure inside the cavity, the gaps between the threads can be reduced. The decrease in void area is of little concern. It is understood that this enables a filtration press that does not cause filter clogging, provides a powder compact with a high bulk density, and reduces the incidence of cracks in the sintered product. [Example] Nonwoven felts made of various synthetic fibers can be used. Typical materials include nylon, polyester, and polypropylene. Ferrite powder often used for manufacturing wet ferrite magnets has an average particle size of about 0.7 to 1.5 μm. The slurry has a concentration ranging from 40% to 70%,
It is convenient for handling. In addition, the pressure inside the cavity during the filtration press is 400 to 5
I want to increase it to 00 ko/cm2. Under such operating conditions, a ferrite powder compact was produced using the following nonwoven felt as a filter. This molded body has a shape in which a cylinder is vertically divided to be sintered to form a permanent magnet for a stator of a motor. Capital Material Thickness of yarn Weight of cloth Fiber volume - Kori Unik
2 630 6902 Polypropylene 2 315
3503 Polyamide 2-6 660 5804 Polypropylene 2.5 800 8805 Polyester 3 800 5806 Polyester 3' 70
0 5007 Polypropylene 3 1200' 13
208 Polyester 3 1200 8709 Polyester 2 800 580 The obtained molded bodies were sintered and examined for cracks. When the results are organized and shown in terms of fiber volume (cm3) per 11112 of the filter, the graph shown in the drawing is shown. In the graph,
A white circle indicates a good result, a black circle indicates a poor result, an IC triangle indicates a possible implementation, and a number next to the plot indicates a filter NO. From this result, the volume of the fiber is 400-800C1
113/' river 2, preferably 450-700 Cl11
It can be seen that non-woven felt of 3/m2 should be used. It has been experienced that if the fiber volume value is too small, the ferrite powder in the slurry passes through the filter. Furthermore, if the volume value is too large, clogging of the filter is observed, and a good powder compact cannot be obtained due to a decrease in the dehydration rate. According to the wet molding method of ferrite powder of the present invention, high mold cavity pressure can be used without clogging the filter,
A good powder compact can be obtained. As a result, the occurrence of cracks in the subsequent tying process is reduced to substantially zero or a level close to it, and the yield of non-defective products is significantly improved.

[Brief explanation of drawings]

The drawings show the volume per unit area of the filter (cm3/m2>) and the crack occurrence rate when ferrite powder is wet-molded using various non-woven felts as filters and the resulting powder compacts are sintered. This is a graph plotting the relationship between patent applicant Daido Steel Co., Ltd. and patent attorney Souo Suga.

Claims (3)

[Claims] (1) In a wet molding method for ferrite powder, which consists of supplying a slurry of ferrite powder into a mold cavity in which a filter sheet is spread on the surface having water permeable holes, and performing filtration press molding, a nonwoven felt made of synthetic fibers is used as the filter sheet. A method characterized by using. (2) The volume of fibers per area 1112 is 400 to 8
The method according to claim 1, using a non-woven felt having the composition No. 0001113. (3) According to claim 2, the process is carried out using ferrite powder with an average particle size of 0.7 to 1.5 μ as a slurry with a concentration of 40 to 70% by weight, and a cavity internal pressure of 400 to 500 kg1012. the method of.