JPH07130528A - Manufacture of sintered material of porous soft magnetic ferrite - Google Patents

Abstract

PURPOSE:To enhance density and strength by forming a press molded body after polystyrene fiber is mixed at the time of forming a press molded body of a soft magnetic ferrite powder and then sintering such a molded body at a high temperature after the polystyrene fiber is splashed by the heat processing. CONSTITUTION:The primary molding is carried out into the predetermined shape by adding polystyrene fiber in such a length as longer than the press molding thickness with the diameter of 0.6mm to 0.2mm to particles of an average grain size of 50mum or less formed by adding an organic binder to the fine powder of the soft magnetic Ni-Zn ferrite in the 20wt.% to 5wt.% for the weight of ferrite particles. Next, a molded ferrite is maintained under the pressure of 250MPa/cm<2> or more to carry out the CIP processing and is then graudally cooled up to 500 deg.C to splash the polystyrene fiber. Thereafter, it is sintered at the temperature of 110 deg.C to 1300 deg.C under the atmospheric condition to obtain a porous soft magnetic ferrite sintered body. The porous soft magnetic ferrite sintered body obtained assures porous property and high processing efficiency having improved product strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous soft magnetic ferrite sintered body used in a high gradient magnetic separation device (HGMS) for removing ferromagnetic fine particles and the like in wastewater.

[0002]

2. Description of the Related Art Conventionally, in order to remove fine particles having weak magnetism such as iron rust suspended in a liquid, a non-magnetic container has been used.
For example, a fine wire of iron-based amorphous alloy containing chromium (Cr), which has a high magnetic flux density and good corrosion resistance, is enclosed as a filter material, a liquid containing iron rust is passed through the container, and a magnetic field is applied from outside the container by an electromagnet. High gradient magnetic separation device (HGMS-H) that adsorbs and removes iron rust around fine wires by utilizing the high magnetic field gradient generated around the amorphous alloy.
high Gradient Magnetic Sepa
ratio).

A conventional high gradient magnetic separator is a high-performance device for separating iron rust or the like having weak magnetism such as iron rust generated in cooling water of a nuclear power plant, and is expensive. Is. On the other hand, iron powder etc. ground in general industrial wastewater is removed by using a roll using a permanent magnet, but iron powder remains in the wastewater passing through the device, especially human body. It is necessary to remove the alloy containing elements such as heavy metals which are harmful to the waste liquid, and the present invention can be used as a filter material even if the liquid contains acid, alkali, etc. It is a method for producing a porous soft magnetic ferrite sintered body.

The porous ceramics sintered body such as the porous soft magnetic ferrite sintered body is used as various functional materials such as catalysts and filters, and as the structural material, such as a member which needs to be lighter in weight and requires less raw materials. It is used and is becoming more important due to the recent demand for multifunctional and lightweight materials.

As a method for producing a porous nonmagnetic ceramics sintered body, various proposals have been made as shown in the following (1) and (2). (1) The sintering raw material is kneaded with an organic binder such as polyvinyl alcohol by the method described in JP-A-55-125202, which is a method for manufacturing an electrode for an alkaline battery, and a foamed resin such as urethane and felt. Apply to the resin fiber electrode core material such as
A method of obtaining a porous material by sintering in a non-oxidizing hydrogen gas at 1200 ° C. for 30 minutes. (2) An iron-based powder having an average particle size of 50 μm or less, an organic binder such as polyacrylic acid, or an inorganic binder such as phosphoric acid bond or water glass is treated with water by the method described in JP-A-2-277703. To prepare a slurry-like kneading liquid, pour it into a mold in which polymer spheres made of styrene or the like are regularly arranged, dry and heat to 100 ° C. to 400 ° C. for 15 minutes to 30 minutes, There is a method in which the spheres are extinguished by thermal decomposition and the iron-based powder is sintered at 1000 ° C. to 1200 ° C. to obtain a porous body.

[0006]

However, the manufacturing methods (1) and (2) described above are not excellent in workability and strength for processing into a desired shape after sintering. The present invention is a porous soft magnetic ferrite sintered body having a large number of through holes for separating and recovering a fine powder of a ferromagnetic alloy in an industrial waste liquid, and when processing into a desired shape after sintering. Provided is a method for producing a porous soft magnetic ferrite sintered body having improved workability and strength.

[0007]

The present invention provides a porous soft ferrite sintered body having a large number of through holes for separating ferromagnetic fine powder contained in a liquid of industrial wastewater in a high gradient magnetic separator. When forming a soft magnetic ferrite powder compact, a polystyrene compact is mixed to form a compact, which is gradually heated to 500 ° C. to scatter the polystyrene fiber.
It is then subjected to high-temperature sintering to obtain a porous soft ferrite sintered body, and a material excellent in strength and workability despite having innumerable through holes. In the present invention, in order to improve strength and workability, cold isostatic pressing (CIP-Cold Isotropi) is performed before high temperature sintering.
c Press) or after high temperature sintering, further high temperature isostatic heat treatment (HIP-Hot Isotropic).
Press). Despite being a porous ferrite sintered body having innumerable through holes by this method,
The density and strength of the material can be improved and the above problems can be solved.

As the first method for producing a porous soft magnetic ferrite sintered body according to the present invention, N having an average particle diameter of 1 μm or less is used.
A solution of 5% polyvinyl alcohol (PVA) or the like as an organic binder was added to i-Zn ferrite or Mn-Zn ferrite, and the average particle size was 5 with a spray dryer.
A granule having a diameter of 0 μm or less is prepared, and a polystyrene fiber having a diameter of 0.6 mm to 0.2 mm and a length of 10 mm to 20 mm is added to the weight of the ferrite granule in a weight ratio of 5% to 20% and stirred to form a molding material. obtain. Then 120
Primary molding at pressure of MPa / cm ² , then 250MP
CIP treatment for 1 minute at a / cm ² and 500 in air
Gradually heat up to ℃ and raise the temperature to scatter polystyrene resin.
High temperature sintering is performed at 100 ° C. to 1300 ° C. to obtain a sintered body.

As a method for producing the second porous soft magnetic ferrite sintered body according to the present invention by using the same raw material powder as in the CIP method, Ni-Zn ferrite or Mn-Zn ferrite having an average particle diameter of 1 μm or less is obtained. 5 as an organic binder
% Polyvinyl alcohol (PVA) and other solutions are added, and granules with an average particle size of 50 μm or less are produced with a spray dryer, and the average diameter is 0.6 mm to 0.2 m.
5% to 20% by weight of polystyrene fiber having a length of 10 mm to 20 mm and a weight of ferrite granules.
A molding material is obtained by adding and stirring. Then 120 MPa / c
After primary molding at a pressure of m ^2, the temperature was gradually raised to 500 ° C. in the atmosphere to scatter polystyrene fibers, and in the atmosphere for the later Ni—Zn ferrite, in the atmosphere for a Mn—Zn ferrite, a nitrogen gas atmosphere with a small amount of oxygen added. In 1100 ℃ to 13
The temperature is maintained at 00 ° C. for about 2 hours to perform the first high-temperature sintering, and further the HIP treatment is performed at 1200 ° C. under the condition of 100 MPa / cm ² for about 3 hours in an Ar gas atmosphere to obtain a sintered body.

That is, the present invention is as follows. Granules having an average particle size of 50 μm or less formed by adding an organic binder to fine powder of soft magnetic Ni—Zn ferrite, and polystyrene fibers having a diameter of 0.6 mm to 0.2 mm and a length of not less than the powder compacting thickness. , 20% by weight to 5% by weight of ferrite granules
After adding 50% by weight and performing primary molding into a desired shape, 250
CIP treatment is carried out by holding at a pressure of MPa / cm ² or more, and the polystyrene fibers are scattered by gradually heating to 500 ° C. in the atmosphere, then 1100 ° C. to 1300 ° C. in the atmosphere.
The method for producing a porous soft magnetic ferrite sintered body is characterized in that sintering is performed at a temperature of.

2. Granules having an average particle size of 50 μm or less formed by adding an organic binder to fine powder of soft magnetic Ni—Zn ferrite, and polystyrene fibers having a diameter of 0.6 mm to 0.2 mm and a length of not less than the powder compacting thickness. 20% to 5% by weight relative to the weight of the ferrite granules was added to perform primary molding into a desired shape, and the polystyrene fiber was scattered by gradually heating to 500 ° C in the atmosphere, and then 1100 in the atmosphere.
Sintered at a temperature of ℃ to 1300 ℃, then 1200 ℃
The method for producing a porous soft magnetic ferrite sintered body is characterized in that the HIP treatment is carried out by maintaining the pressure at 100 MPa / cm ² or more in argon gas at the above temperature.

3. Granules having an average particle size of 50 μm or less formed by adding an organic binder to fine powder of soft magnetic Mn-Zn ferrite, and polystyrene fibers having a diameter of 0.6 mm to 0.2 mm and a length of not less than the compacting thickness. After adding 20 wt% to 5 wt% to the weight of the ferrite granules and performing primary molding to a desired shape, CIP treatment is performed by holding at a pressure of 250 MPa / cm ² or more and 500 ° C. in the atmosphere.
The polystyrene fibers are scattered by being slowly heated to 1100 ° C. to 130 ° C. in nitrogen gas containing a slight amount of oxygen.
A method for producing a porous soft magnetic ferrite sintered body, which is characterized in that sintering is performed at a temperature of 0 ° C.

4. Granules having an average particle size of 50 μm or less formed by adding an organic binder to fine powder of soft magnetic Mn-Zn ferrite, and polystyrene fibers having a diameter of 0.6 mm to 0.2 mm and a length of not less than the compacting thickness. 20 wt% to 5 wt% of the weight of the ferrite granules was added to perform primary molding into a desired shape, and the polystyrene fibers were scattered by gradually heating to 500 ° C. in the atmosphere and then at 1100 ° C. to 1300 ° C. Sintered in nitrogen gas to which a slight amount of oxygen was added at a temperature, and then kept at a temperature of 1200 ° C. or higher in argon gas at a pressure of 100 MPa / cm ² or higher to obtain HI
A method for producing a porous soft magnetic ferrite sintered body, which is characterized in that P treatment is performed.

[0014]

In the method for producing a porous soft magnetic ferrite sintered body according to the present invention, Ni-Zn ferrite and Mn-
The polystyrene fibers added to the Zn ferrite granules are
The weight ratio is preferably in the range of 20% by weight to 5% by weight with respect to the weight of the ferrite powder. If the amount of polystyrene fiber added exceeds 20% by weight, the polystyrene fibers will spring back when the powder compact is formed and the pressure will be reduced. The powder compact will be damaged, and the strength of the ferrite sintered body will be weak so that it cannot be used. On the other hand, if it is 5% by weight or less, the proportion of the through holes formed in the ferrite sintered body will be small, and as a filter, 20% by weight due to poor performance of
The preferred range is from 5 to 5% by weight.

Further, the diameter of the polystyrene fiber mixed in the powder compact for forming the innumerable through-holes is such that if the diameter of the polystyrene fiber is 0.6 mm or more, the powder is compacted by powder compaction. When the body is molded, the polystyrene fiber springs back and destroys the green compact, and the diameter is 0.2 mm.
In the following, when the HIP process is performed, the through holes formed in the sintered body are crushed and some of the through holes are closed. The length of polystyrene is 10 mm or 20 mm, which is longer than the thickness of the green compact, because the thickness of the sintered body is 6 mm (the thickness of the green compact is 8 mm) in the embodiment of the present invention. The length of the polystyrene fiber used may be appropriately selected depending on the thickness of the sintered body.

The degreasing temperature for removing the polystyrene fiber from the green compact was raised from room temperature to 500 ° C. in the air at a rate of about 20 ° C./hour. The speed may be such that the polystyrene fibers are scattered and sufficiently removed during the sintering at 1100 ° C. to 1300 ° C. for forming the next sintered body.

The through-holes formed during the primary high-temperature sintering during the HIP treatment are maintained at 1200 ° C. during the HIP treatment and maintained for 3 hours while applying a pressure of 100 MPa / cm ² in argon gas. Even if the binding is performed, in the pressurized high temperature sintering state in argon gas during HIP processing,
Even if the holes existing at the grain boundaries in the material are crushed, the holes of the through holes are not crushed. Therefore, the high-temperature sintered material having innumerable through-holes further increases the material strength of the sintered body by the HIP treatment and prevents the occurrence of chipping during surface processing.

When HGMS is used, the ferrite material used is preferably a material having a high magnetic flux density, while the value of the magnetic characteristics of the material is such that the through holes formed in the ferrite when the magnetic field applied to the ferrite is removed and a liquid is made to flow. Any value may be sufficient as long as it guarantees the coercive force of the strength with which the ferromagnetic fine particles adhered inside are removed from the through-hole, and the value of the relative magnetic permeability relative to the coercive force may be 100 to 1000. . Therefore, in the soft magnetic ferrite material of the present invention, in Ni—Zn ferrite, Fe ₂ O ₃ is 49 mol% to 49.9 mol%,
NiO is 16 mol% to 20 mol%, and the material having the composition range of residual ZnO, Mn-Zn ferrite has Fe ₂ O ₃ of 55.
Mol% to 58 mol%, MnO 26 mol% to 3
A material having a composition range of 0 mol% and residual ZnO is used.

[0019]

EXAMPLES Next, examples of the present invention will be described. (Example 1) As a raw material powder for a sintered body, the average particle size is 1 μm.
Following Ni-Zn ferrite (Fe ₂ O ₃ 55 mol%, M
nO 28 mol%, ZnO residue) was used as a pre-calcined powder, and polyvinyl alcohol (PVA) # 170 was added to the pre-calcined powder.
20% by weight of 0 in a 5% aqueous solution is added, mixed by a ball mill, and granulated into particles of 50 μm or less by a spray dryer to produce a mother powder. The diameter is 0.6 mm to 0.2 mm and the length is 10 m with respect to the above mother powder.
20% by weight of m to 20 mm polystyrene resin fiber
(The maximum amount of polystyrene fiber added) was added and dry mixing was performed to obtain a raw material powder. Next, using a mold of 50 mm × 50 mm, a primary powder compact having a thickness of 8 mm was obtained at a pressure of 120 MPa / cm ² .

Here, in the molding by the cold isostatic pressing (CIP), the primary powder compact is vacuum-packed in a polystyrene vinyl bag, and the wet compact CIP apparatus is used for 25
The CIP treatment was performed under the condition of maintaining the pressure at 0 MPa / cm ² for about 1 minute. Then, the green compact is
The polystyrene resin fiber was decomposed and scattered by raising the temperature to 500 ° C. at a temperature rising rate of ° C./hour. The obtained porous body is 1200
Ni-Zn
A sintered body of ferrite according to the invention was obtained.

(Example 2) In the method of performing hot isostatic pressing (HIP) of Ni-Zn ferrite, N of Example 1 was used.
The i-Zn ferrite primary green compact was gradually heated to 500 ° C and the polystyrene resin fiber was decomposed and scattered.
A primary high temperature sintered body is produced by holding it in the atmosphere at 0 ° C. for about 2 hours, and further subjected to HIP treatment in an argon gas atmosphere under the condition of holding it for 3 hours while applying a pressure of 100 MPa / cm ² at 1200 ° C. It was

(Embodiment 3) Mn-Zn ferrite (Fe ₂ O ₃ 56) having an average particle diameter of 1 μm or less was used as a raw material powder for a sintered body.
Mol%, MnO 28 mol%, ZnO residue) was used as a pre-baked powder, and polyvinyl alcohol (PVA) # 1 was added to this powder.
20% by weight of 5% aqueous solution of 700 was added, mixed by a ball mill, and 50 μ by a spray dryer.
Granules of m or less were granulated to obtain a mother powder. The diameter of the mother powder is 0.6 mm to 0.2 mm, and the length is 10 m.
A polystyrene resin fiber of m to 20 mm was added at a maximum addition amount of 20% by weight, and dry mixing was performed to obtain a raw material powder. Next, 120MP using a 50mm x 50mm die
A pressure of a / cm ² was applied to carry out primary molding to a thickness of 8 mm.

Here, in the molding by cold isostatic pressing (CIP), the primary compact is enclosed in a polyethylene vinyl bag and vacuum packed, and the wet compact CIP apparatus is used for 2
C under a pressure condition of holding at 50 MPa / cm ² for about 1 minute
IP treatment was performed. Then, this molded body is subjected to 20
The polystyrene resin fiber was decomposed and scattered by gradually raising the temperature to 500 ° C. at a temperature rising rate of ° C./hour. The obtained porous body is 12
About 2 in a nitrogen gas atmosphere with a slight amount of oxygen added at 00 ° C
After sintering for a time, a sintered body of the present invention made of Mn-Zn ferrite was obtained.

(Example 4) In the method of performing hot isostatic pressing (HIP) of Mn-Zn ferrite, M of Example 3 was used.
The n-Zn ferrite primary molded body was gradually heated to 500 ° C and the polystyrene resin fiber was decomposed and scattered to 1200 ° C.
And hold it in a nitrogen gas atmosphere containing a small amount of oxygen for 2 hours to create a primary sintered body, and further to 100 MPa at 1200 ° C.
/ Cm ² HIP treatment was performed for 3 hours in an argon gas atmosphere.

(Comparative Example 1) CI of Ni-Zn ferrite
Using the same mother powder as the P-processed sintered body and the HIP-processed sintered body, the powder was compacted into a size of 50 mm × 50 mm × 8 mm at a pressure of 120 MPa / cm ^2. Furthermore, it is gradually heated at a temperature rising rate of 20 ° C / hour to 500 ° C.
The strength and workability were evaluated by using as a comparative example 1 a sintered body obtained by holding the polystyrene resin fiber decomposed and scattered at 1200 ° C. for 2 hours in the air.

(Comparative Example 2) CI of Mn-Zn ferrite
120 MPa in a size of 50 mm × 50 mm × 8 mm using the same mother powder that has been subjected to P treatment and HIP treatment
1200 ° C is obtained by decomposing and scattering polystyrene resin fibers by gradually heating to 500 ° C at a temperature rising rate of 20 ° C / hour to obtain a powder compact, which is molded by applying a pressure of / cm ²
The sintered body was obtained by holding in a nitrogen gas atmosphere to which a small amount of oxygen was added for 2 hours, and as Comparative Example 2, strength and workability were evaluated.

The samples according to the examples 1 and 3 by the CIP treatment obtained by the above steps, the samples according to the examples 2 and 4 by the HIP treatment, and the 6 conditions prepared as the comparative example 1 and the comparative example 2. The bending strength and chipping occurrence rate of the sample were measured. The bending strength is 2mm × 2mm × 25m
Measured with a load cell tester using the one processed to m, and for chipping, use a diamond grindstone with a grain size of # 800 and a width of 0.8 mm, and rotate at 1000 rpm.
Grooving was performed with an outer peripheral blade cutting machine under the conditions of rpm, feed rate 10 mm / min, and groove depth 2.0 mm, and the chipping depth was measured with an optical microscope.

The results are shown in Table 1. The length of groove processing at the time of chipping measurement is 30 mm.

[Table 1]

As is clear from the results shown in Table 1, the manufacturing method of the present invention has made it possible to obtain porous soft magnetic ferrite for HGMS, which has improved workability and strength.

The Ni--Zn used in the examples of the present invention
Ferrite is a material of 55 mol% of Fe ₂ O ₃ , 28 mol% of MnO, and ZnO residue, and Mn-Zn ferrite is Fe.
₂ O ₃ 56 mol%, MnO 28 mol%, residual ZnO,
20% by weight of polystyrene fiber for forming through holes
Although only the method for producing the added porous soft magnetic ferrite has been described, regarding Ni—Zn ferrite, Fe ₂ O ₃ is 49 mol% to 49.9 mol% and NiO is 16 mol% to 20 because of the magnetic properties of the material. Mol%, balance Zn
O is a soft magnetic material, and in the case of Mn-Zn ferrite, a soft magnetic material having a composition range of 55 mol% to 58 mol% Fe ₂ O ₃ , 26 mol% to 30 mol% MnO, and residual ZnO is suitable.

The amount of polystyrene fibers added to the granular powder for forming the porosity can be added up to 20% at the maximum weight ratio, and the minimum addition amount is 5% by weight from the amount of the through holes forming the porosity. It should be about the same.

The wet process CIP treatment and the HIP process used in the present invention have different pressurizing abilities depending on the apparatus used, but in the apparatus used in this embodiment, the pressure applied by the wet method CIP processing apparatus is 450 MPa / The condition of cm ² is possible,
With HIP treatment, up to 120 MPa / cm ² is possible.

Sintering after the treatment of decomposing and scattering polystyrene resin fibers was carried out at 1200 ° C. in this embodiment, but it is usually within a sintering temperature range of 1100 ° C. to 1300 ° C. for sintering soft magnetic ferrite. For example, a ferrite material having characteristics similar to those of the present invention can be obtained.

[0034]

By the method for producing a porous soft magnetic ferrite according to the present invention, a soft magnetic Ni-Zn ferrite or Mn-Zn ferrite used in a high gradient magnetic separator for industrial wastewater is porous and has good workability. Now, it is possible to provide a porous soft magnetic ferrite sintered body having improved product strength.

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Claims (4)

[Claims] 1. Granules having an average particle size of 50 μm or less formed by adding an organic binder to a fine powder of soft magnetic Ni—Zn ferrite, and having a diameter of 0.6 mm to 0.2 mm and a length of at least the compacting thickness. 20% to 5% by weight based on the weight of the ferrite granules of polystyrene fiber is added to perform primary molding into a desired shape, and then CIP treatment is performed by holding at a pressure of 250 MPa / cm ² or more and in the atmosphere. At 500 ° C
A method for producing a porous soft magnetic ferrite sintered body, characterized in that the polystyrene fiber is scattered to be gradually heated until it is sintered at a temperature of 1100 ° C. to 1300 ° C. in the atmosphere. 2. Granules having an average particle size of 50 μm or less formed by adding an organic binder to a fine powder of soft magnetic Ni—Zn ferrite, and having a diameter of 0.6 mm to 0.2 mm and a length of at least the compacting thickness. 20% to 5% by weight with respect to the weight of ferrite granules is added to the polystyrene granules to perform primary molding into a desired shape, and the polystyrene fibers are scattered by gradually heating to 500 ° C. in the air, and then in the air. 1100 ° C
To 1300 ° C., and then HIP treatment is carried out by holding at a temperature of 1200 ° C. or higher in argon gas at a pressure of 100 MPa / cm ² or higher, and then performing a HIP treatment. Body manufacturing method. 3. Granules having an average particle size of 50 μm or less formed by adding an organic binder to fine powder of soft magnetic Mn—Zn ferrite, and having a diameter of 0.6 mm to 0.2 mm and a length of at least the powder compacting thickness. 20% to 5% by weight based on the weight of the ferrite granules of polystyrene fiber is added to perform primary molding into a desired shape, and then CIP treatment is performed by holding at a pressure of 250 MPa / cm ² or more and in the atmosphere. At 500 ° C
The polystyrene fibers are scattered by being slowly heated to 1100 ° C. to 130 ° C. in nitrogen gas containing a slight amount of oxygen.
A method for producing a porous soft magnetic ferrite sintered body, which comprises sintering at a temperature of 0 ° C. 4. Granules having an average particle diameter of 50 μm or less formed by adding an organic binder to a fine powder of soft magnetic Mn—Zn ferrite, and having a diameter of 0.6 mm to 0.2 mm and a length not less than the powder compacting thickness. 20% by weight to 5% by weight based on the weight of the ferrite granules is added, primary molding is performed to a desired shape, and the polystyrene fibers are scattered by gradually heating to 500 ° C. in the air, and then at 1100 ° C. 1
Characterized by sintering at a temperature of 300 ° C. in nitrogen gas to which a small amount of oxygen is added, and then performing HIP treatment at a temperature of 1200 ° C. or higher in argon gas at a pressure of 100 MPa / cm ² or higher. And a method for producing a porous soft magnetic ferrite sintered body.