JPH06305813A - Production of non-magnetic material - Google Patents

Abstract

PURPOSE:To produce a non-magnetic material improved in abrasion resistance by mixing an alumina raw material as a sintering auxiliary with other calcined raw materials without calcining a part or all of the alumina raw material, molding the mixture ant subsequently calcining the molded product. CONSTITUTION:Starting raw materials containing CoO fine powder and NiO fine powder as basic components, respectively, are compounded in a prescribed CoO/NiO molar ratio and sufficiently mixed with each other by the use of a ball mill, etc. The mixed powder is calcined at approximately 850 deg.C in a N2 atmosphere, ground with a ball mill, etc., mixed with >=0.2wt.% of alumina fine powder having an average particle diameter of <=0.1mum. and further ground. The prepared composition is press-molded with a CIP, etc., and subsequently sintered at a prescribed temperature to provide a non-woven material having a relative density of >=99% and an average crystal particle diameter of <=5mum and improved in abrasion resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-magnetic material containing alumina as a sintering aid, and particularly for a magnetic head having excellent wear resistance, a small crystal grain size and high transverse rupture strength. The present invention relates to a non-magnetic substrate.

[0002]

2. Description of the Related Art In order to use ceramics for a non-magnetic substrate for a magnetic head, the relative density of the sintered body is 99% or more and the average crystal grain size is 5 μm or less in terms of wear resistance and machinability. Is desired.

However, a non-magnetic material is mixed with a starting material,
In the method of manufacturing through the steps of calcination, crushing, molding, and sintering, in the conventional method of mixing starting materials of all components from the beginning, when the sintering temperature is raised to increase the relative density of the sintered body, the crystal When the grain size becomes large and the sintering temperature is lowered in order to reduce the crystal grain size, the relative density of the sintered body becomes low, and it is impossible to satisfy the requirements for both the relative density of the sintered body and the crystal grain size. There was a problem.

In the prior art, even if the relative density is 99% or more by performing HIP treatment after sintering, the crystal grain size is 5.5.
The limit was μm.

[0005]

DISCLOSURE OF THE INVENTION The present invention has solved the above-mentioned problems, and an object of the present invention is to provide a sintered body having a relative density of 99% or more only without sintering, and with an average crystal grain. The purpose is to produce a non-magnetic material having a diameter of 5 μm or less.

[0006]

In order to solve the above problems, the present inventors have studied the manufacturing process in detail, and as a result, in the conventional method, the added alumina undergoes a heat history due to calcination. As a result, they found that the function as a sintering aid was weakened, and the present invention was accomplished.

That is, according to the present invention, a non-magnetic material containing alumina as a sintering aid is mixed with a starting material, calcined,
In the method of manufacturing through the steps of crushing, molding, and sintering, a part or all of the alumina raw material is not calcined, but is mixed with other raw materials that have undergone the above calcining step, and then the above-mentioned molding and firing are performed. The present invention provides a method for producing a non-magnetic material, which comprises performing a binding step.

Further, the present invention provides a method for producing a non-magnetic material in which the amount of alumina raw material that is not calcined is 0.2 wt% or more of the total raw material. Further, the present invention provides a method for producing a non-magnetic material in which the amount of alumina raw material that is not calcined is 0.2 wt% or more of all raw materials and the amount of alumina raw material that is calcined is 0.1 wt% or more of all raw materials. . The nonmagnetic material can be suitably applied to cobalt oxide and nickel oxide, or a material having a basic composition of nickel oxide.

Alumina that does not undergo a thermal history due to calcination by performing a molding and sintering process after mixing a part or all of the alumina raw material with another raw material that has undergone the calcination process, without calcination Effectively acts as a sintering aid, and the relative density of the sintered body can be increased without increasing the sintering temperature. The amount of alumina that does not undergo the heat history due to calcination is 0.2 wt% or more of the total raw material, and more preferably 0.1.
If it is 4 wt% or more, the above effect can be obtained.

Alumina added before calcination has the effect of reducing the average particle size of the agglomerated particles of the powder pulverized after calcination, whereas it is 1.0 to 1.5 μm when not added. 0.1 wt% or more of the total raw material, more preferably 0.1.
When it is added in an amount of 4 wt% or more, the thickness can be 0.3 to 0.6 μm, and the average crystal grain size after sintering can be further reduced.

[0011]

Example 1 CoO having an average particle size of 4 μm and an average particle size of 0.6
CoO / NiO (molar ratio) = 35 using μm NiO as a raw material
A total of 2 kg was mixed for 20 hours using a wet ball mill so that the composition became / 65. This mixed powder is calcined in an N ₂ atmosphere at a temperature of 850 ° C., and then mixed with a wet ball mill to 3
Crushed for 6 hours. Thereafter, 2 wt% of alumina having an average particle size of 0.1 μm or less was added to the same wet ball mill with the above composition as 100, and further mixed and pulverized for 2 hours.

CIP this powder at a pressure of 1500 kg / cm ^2.
It was molded, sintered at 1230 ° C. for 10 hours, and subjected to HIP treatment. The relative apparent density, average crystal grain size, Vickers hardness of the sintered body after sintering according to this example, and the relative density and average crystal grain size of the sintered body after HIP treatment were measured. The results are shown in Table 1.

[Table 1]

[0013]

Example 2 The same treatment as in Example 1 was performed except that 1 wt% of alumina was added first and the remaining 1 wt% was added after calcination. The physical properties after sintering and after HIP treatment according to the second embodiment are shown in Table 1 together with the first embodiment.

[0014]

[Comparative Example 1] The same treatment as in Example 1 was carried out except that 2 wt% of alumina was first added and not added after calcination. The physical properties after sintering and after HIP treatment according to this comparative example are shown in Table 1 together with Examples 1 and 2. As is clear from Table 1, in the present invention, it is possible to obtain a higher relative density and a smaller crystal grain size than those obtained by the conventional HIP treatment only by sintering.

[0015]

As described above, the steps which conventionally required the HIP step after pressureless sintering are the relative densities of 99% or more and the average crystal grain size of 5 μm which is the target of the present invention only by sintering.
It was possible to obtain a sintered body of m or less. As a result, the Vickers hardness, which is a measure of wear resistance required as a magnetic head material, was improved, and a non-magnetic material superior in quality to the conventional method could be obtained.

Claims (4)

[Claims] 1. A method for producing a non-magnetic material containing alumina as a sintering aid through the steps of mixing starting materials, calcination, crushing, molding, and sintering, and part or all of the alumina raw material. A method for producing a non-magnetic material, characterized in that the material is mixed with another raw material that has been subjected to the above-mentioned calcination step without being calcinated, and then the above-mentioned forming and sintering steps are performed. 2. The method for producing a non-magnetic material according to claim 1, wherein the amount of the alumina raw material that is not calcined is 0.2 wt% or more of the total raw material. 3. The method for producing a non-magnetic material according to claim 2, wherein the amount of the alumina raw material to be calcined is 0.1 wt% or more of the total raw material. 4. The method for producing a non-magnetic material according to claim 1, 2 or 3, wherein the non-magnetic material is a material having a basic composition of cobalt oxide and nickel oxide or nickel oxide.