JPH044104A - Wet-type mold for molding ferrite powder - Google Patents

Abstract

PURPOSE:To enable the moldability of ferrite powders with an excellent mold releasing property at high productivity and without any blinding by the use of molds constituted of borron nitride and other ceramics components. CONSTITUTION:A wet-type mold of ferrite is constituted of borron nitride (B N) and other ceramics components of one or two kinds or more and has gas permeability. In this case, it is preferable to allow the weight ratio of BN to be 10 - 50%, the average pore size to be 0.3 - 3 mum, and the pore rate to be 10 - 50%. And, at the time of manufacturing molds, Si3N4 is made into powders of 0.8 mum in its average particle diameter and 93% in its alpha phase rate and BN is made into powders of 0.2 mum in its average diameter and 97% in its purity as initial raw materials and two kinds of these powders (including a baking assistant of Si3N4) are blended in use of ethanol by a ball mill and after drying, molds are molded by slip casting and the molded substances are baked in N2.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention relates to a wet molding mold for ferrite powder, particularly a mold having water absorption properties due to fine pores, long life, high strength, and good moldability. be.

[Prior art] Wet molding is a type of powder molding technology, and includes slim casting, wet press molding, potter's wheel molding, extrusion molding,
There are injection molding methods, and it has been particularly applied in the ceramics field, and old rice has been used to make sanitary ware and ceramics, but in recent years it has also been applied to ferrite powder, and is expected to be used as a molding technology for industrial parts.

Gypsum molds, which have been known for a long time, are common as wet molding molds. This is due to its excellent water absorption, mold releasability, dimensional accuracy, and the ability to produce large, complex shapes at low cost.

However, on the other hand, it is weak in water resistance, compressive strength, and ITFt abrasion resistance, and has some drawbacks, such as Ca'+ ions in the plaster getting mixed into the base material. It also has Gypsum molds also have the problem that the porosity and pore size distribution vary from mold to mold, and water absorption varies, and molding conditions are not constant. Furthermore, pressure molding to improve productivity is insufficient in strength, and a large number of molds must be used in parallel.
There is also.

Against this background, in order to overcome the drawbacks of plaster molds,
Various molds made of other materials have been developed. Main materials include resin, resin-ceramics, metal-ceramics, and metal.

However, these types have the following drawbacks.

(1) If the pore size is larger than 3 μm and the particles are fine, the mold will become clogged.

(2) The mold releasability between the mold and the base material is poor, and it is necessary to forcefully remove the mold by passing gas, etc., and the molded product is easily damaged. Furthermore, if polyvalent cations such as Ca2+, which are easily exchanged for one ion, are contained on the mold surface in order to improve mold releasability, this will be mixed into the base material.

(3) Since machining of molds is not easy, machining costs are high in order to achieve surface accuracy or to finish complex shapes with extremely thin walls or extremely fine details with good dimensional accuracy.

[Problems to be Solved by the Invention] The purpose of the present invention is to solve the above-mentioned five problems with plaster molds and other molds, and to provide a wet molding mold having the following characteristics. .

■ It has a fine pore size that does not cause clogging even when ultra-fine ferrite powder is used.

■ The mold surface should be water resistant, organic solvent resistant, and long-life with excellent compressive strength so that the mold surface does not deteriorate or wear out even after multiple uses.

■ It must be a high-strength type that can be molded not only under normal pressure but also under pressure.

(4) Furthermore, it must be of a high-performance type that does not easily get wet with the substrate.

Wet molding in the present invention refers to ferrite slurry (
Molding methods include slip casting (casting), in which slurry is poured into a mold, wet press molding, potter's wheel molding, which is a type of plastic molding that molds clay-like clay, extrusion molding, and injection molding1. The wet molding mold of the present invention is suitably used for these moldings.

[Means for Solving the Problem 1] The present inventors compared and studied various materials for a mold for wet molding, which is one of the main molding methods for powder, and found that a mold made of boron nitride and other ceramic components was used. The present invention was completed based on the discovery that a ferrite wet molding mold having extremely excellent properties, which has never been seen before, can be obtained using a composite sintered body.

The present invention is a wet molding mold for ferrite that is composed of boron nitride (BN) and one or more other ceramic components and has air permeability. The weight ratio of
0%, average pore diameter M0.1-3 μm, and porosity 10
~50% is preferred.

[Effect 1 The present invention will be explained in detail below.

The inventors first investigated the material of the mold. We chose it among ceramics because of its wear resistance and pressure resistance.

We considered BN as a base because it is difficult to get wet with the substrate (from the point of view of ease of workability).However, BN is difficult to sinter, and is usually used for LJ.
Problems include sintering using the P method and low wear resistance.

Therefore, the present inventors considered combining BN with another ceramic component that is densely sintered by normal pressure or atmospheric pressure firing and has excellent wear resistance and compressive strength. The purpose of this is (1) B to sinter the other ceramics.
N inhibits the formation of pores.

(2j While taking advantage of the benefits of BN, it supplements wear resistance.

This is a combined effect.

In order to ensure sufficient water absorption and drainage of the mold, the pores must be continuous pores connecting the inner and outer surfaces of the mold, and the mold must have air permeability.

Next, the present invention will be explained using Si3N as BN and other ceramics.
The explanation will be based on a specific experiment using 4.

The starting material for Si3N4 is a powder with an average particle size of 0.8 μm and 93% A phase, and BN has an average particle size of 0.2 μm and a purity of 97%.
% powder was used as the starting material.

These two types of powder (including Si3N4 sintering aid) were mixed in a ball mill using ethanol, dried, and then slip casted into 50 mm long, 50 mm wide,
A test piece with a thickness of 10 mm was molded, and the molded product was heated with N2.
It was sintered at 1800'C in 9 atm. Si3N
The weight ratio of 4 and BN is S i3N4 /BN= 100
10.90/10.80/20.70/30.60/4
It was set as 0.50150.40/60.

The physical properties of these sintered bodies were evaluated. Figure 1, Figure 2,
Figure 3 shows the three-point bending strength (σb3) at room temperature,
The dependence of Shore hardness and porosity on BN content is shown. FIG. 4 shows the pore size distribution for a sintered body in which (a) has a BN content of 20% by weight and (bJ has a BN content of 50% by weight).

From the results shown in FIGS. 1 to 4, as the BN content increases, the strength and hardness decrease, but the porosity increases. Also, the pore diameter is BN
It can be seen that regardless of the content, the distribution range is very sharp with an average pore diameter of 0.2 μm. From this,
It is believed that BN inhibits the sintering of S i 3 N 4 and that the degree of inhibition increases as the BN content increases. In addition, the pressure resistance strength is the same as that of plaster molds, 1O ~ 50 kg/cm
It has sufficiently high strength compared to ``, and can be molded not only under normal pressure but also under pressure.

Furthermore, since the pore diameter is very fine and the distribution is sharp, it is judged that the water absorption of the mold is sufficient and uniform. The reason why the pore size becomes smaller is thought to be because the starting material is fine particles.

As described above, by using the mold of the present invention, there is no clogging even with fine particles, good demoldability, and considerably high pressure molding is possible, thereby improving mass productivity. Furthermore, since it has excellent wear resistance, the surface accuracy of the molded product can be maintained constant. This makes it possible to handle products with strict quality requirements, such as automobile parts.

Other ceramic components to be combined with BN are Si3N4
Besides, for example, SiC, 5IALON, ZrO2,
Materials with excellent wear resistance such as Aj2203, AffN, and mullite can be used, and the combined effect with BN is S
It was similar to i3N4. Also AI2203
- The same is true when two or more types are combined depending on the purpose, such as Zr 02.6 Furthermore, since the pore size and porosity can be controlled arbitrarily by the particle size and content of the starting materials, molding The particle size and content of the material to be used may be adjusted. The greater the BN content, the better the mold releasability and processability, but the lower the compressive strength and hardness, so it may be arbitrarily controlled depending on the material to be molded.

The present invention will now be explained based on a concrete experimental example of slip casting.

The present inventors actually made a slurry using ferrite powder. SrCO3 and Fe2O3 were prepared as starting materials, and the molar ratio was 5rCOa/Fe20a=115.9.
Sr0
- A calcined body having a composition of 5.9Fe203 was obtained.

This calcined body was dry-milled and then wet-milled, and the average particle size was 1.
It was made into ferrite powder of 2 μm. This ferrite powder 1
00 parts by weight, 45 parts by weight of 0.5% aqueous ammonium polycarboxylate as a binder and 0.6 parts by weight of ammonium polyacrylate as a dispersant, and mixed in a ball mill for 5 hours to produce approximately 2000 cps.
of slurry was obtained.

This slip was sintered in the same manner as described above.
Using an N4-BN mold (bottomed cylindrical shape with inner diameter 40 mm, E 100 mm, and wall thickness 40 mm), normal pressure (P = Ok
g/c rri″) and under pressure (P=10.20
The samples were molded by slip casting at a temperature of 1 kg/c rn'') and evaluated for moldability such as ink deposition speed.The various test results are shown in Table 1.

Mold wear is the amount of wear after 50 tests.

Further, molds of the present invention in which the S j 3N4/BN weight ratio was 70/30 and the BN particle size was varied were similarly tested, and the results are shown in Table 2.

From these results, it was found that the N content should be selected to ensure that the mold does not become clogged, mass productivity is significantly improved by pressurization, and the mold releasability and abrasion resistance are optimal. Further pressurization also improves mass productivity.

The higher the BNN content, the higher the porosity, which improves mass productivity.

Note that when the weight ratio of BN is less than 10%, it becomes difficult to release from the mold, and when it exceeds 50%, the wear resistance becomes poor.

Furthermore, if the average pore diameter is less than 0.1 LLm, the molding speed will be too low, and if it exceeds 3 μm, clogging may occur. Furthermore, if the porosity is less than 10%, the molding speed will be too low, and if it exceeds 50%, the strength of the mold will be insufficient.

Although slip casting has been explained here as an example, this effect is similar in other wet molding methods, such as IR press molding, extrusion molding, injection molding, and the like. Therefore, in these molding methods as well, the characteristics of the mold may be appropriately controlled using the same concept as above.

[Example] Examples of the present invention will be described below regarding slip casting.

As the mold according to the invention, 3 BN was added in a weight ratio, respectively.
5iC-BN, Zr0zBN, Aff20 containing 0%
3-BN, MUYIT-BN, 5IALON-BN, A
-j2203-Zr02-BN (A 42203 /
Z r 02 weight ratio = 80/20) was prepared, and a plaster mold and an epoxy resin mold were prepared as comparative examples. The shape of the mold is the same as described above.

Slip casting is performed using the slip of the ferrite powder mentioned above under normal pressure and 10.20 kg/c.
The test was carried out under pressure of rn'. The test was repeated 50 times,
The results are shown in Table 3.

As is clear from the results in Table 3, the mold of the present invention was good in all items. On the other hand, epoxy resin molds clog quickly and have a short lifespan. Furthermore, the molding pressure of plaster molds is limited to 10 kg/crn', which makes them difficult to mass produce and causes rapid wear.

Although slip casting has been explained here as an example, the present invention is not limited to this, and can be applied to all types of wet molding such as potter's wheel molding, wet press molding, extrusion molding, and injection molding. be.

[Effects of the Invention] According to the present invention, by using a mold made of boron nitride and other ceramic components, wet molding of ferrite powder is much superior to conventional stone molds and resin molds. By obtaining a mold and performing wet molding using the mold, it is possible to mold ferrite powder with high productivity, no clogging, and good mold releasability.

[Brief explanation of drawings]

Figure 1 is a diagram showing the dependence of the three-point bending strength at room temperature on the BN content of the Si3N4-BN composite sintered body of the present invention, and Figure 2 is the Shore hardness of the sintered body. FIG. 3 is a diagram showing the dependence of the porosity of the sintered body on the BN content, and FIG. 4 (a) and (b)
) are 5i with BN content of 20 and 50% by weight, respectively.
FIG. 3 is a diagram showing the pore size distribution of a 3N4-BN composite sintered body. Kawasaki

Claims (1)

[Claims] 1 Consisting of boron nitride and one or more other ceramic components, the weight ratio of boron nitride to the total weight of boron nitride and the other ceramic components is 10 to 50.
%, average pore diameter 0.1-3 μm, porosity 10-50
% and has air permeability.