JP3112286B2 - Manufacturing method of dense machinable ceramics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a dense machinable ceramic in which fluorophlogopite (hereinafter abbreviated as FP) microcrystals are dispersed and contained in a vitreous matrix. . More specifically, the present invention relates to a method for producing a dense machinable ceramic having a very small amount of gas adsorbed and desorbed and easy to perform fine processing and precision processing.

(Prior art) As for the FP glass ceramics, a melting method of melting a raw material prepared as disclosed in Japanese Patent Application Laid-Open No. 47-2427 at a high temperature, forming a glass body of a desired shape, and generating and growing FP crystals is known. However, this manufacturing method has problems such as large energy consumption and difficulty in near net shaping. As a solution to these problems, a method capable of producing FP-based glass ceramics by a sintering method has been disclosed (Japanese Patent Application Laid-Open No. 62-7649), which has good workability, enables near-net shaping, and provides machinable ceramics. Of various applications.

However, as a new application of machinable ceramics, fine processing and precision processing are possible, such as jigs for pin grid arrays in the field of electronic components and insulating members for X-ray CT scanners in the field of medical equipment. Applications in fields that require no or very little adsorption and desorption are increasing. However, glass ceramics produced by the conventional sintering method have some pores due to their production method, so that fine processing and precision processing can be performed, but there is a problem in gas adsorption / desorption performance.

(Problems to be solved by the invention) In order to solve the above-mentioned problems, the present invention can perform fine processing and precision processing by a sintering method which is a relatively simple manufacturing method.
The purpose of the present invention is to provide a method for producing a dense machinable ceramic with very little gas adsorption and desorption.

(Means for Solving the Problems) The present inventors have found that even FP-based glass ceramics manufactured by a sintering method have good machinability by performing appropriate post-treatment, and have almost true density. The present inventors have found that close and dense machinable ceramics can be obtained, and have completed the present invention. That is, the present invention is a method for producing dense machinable ceramics, which comprises subjecting a fluorophlogopite glass ceramic produced by a sintering method to hot isostatic pressing. Next, the method of the present invention will be described in detail according to one of its embodiments. This embodiment is disclosed in Japanese Patent Application No. 1-257070.
This method is for subjecting an FP-based glass ceramic produced according to the method described in the above item to HIP treatment, and includes the following steps (1) to (4) in that order.

When kaolin and activated clay are used as main raw materials, Mg, K, and F-containing compounds are used as auxiliary raw materials, and B ₂ O ₃ is used as a sintering aid, the component composition at the time of forming a fired body is represented by oxide weight basis, ₂ 35
6060%, Al ₂ O ₃ 10-20%, MgO 10-25%, K ₂ O 3-1
A fine particle material mixture adjusted to have a composition of 5%, F 2 to 15%, and B ₂ O _{3 to} 1 to 3% has a maximum temperature of 1,000 to 1,100.
A step of calcining under a first heat treatment condition of 30 ° C. to obtain a calcined body containing fluorophlogopite and glass and containing 30 to 60 vol% of crystals of fluorophlogopite.

After the calcined body is pulverized into fine particles, a desired molded body is formed using the calcined body fine particles.
A step of obtaining a fired body by sintering under the second heat treatment condition of 0 to 1,250 ° C.

The maximum temperature of the fired body is 800 to 1,000 ° C and the maximum pressure is 500 to 2,000 by hot isostatic pressing (hereinafter referred to as HIP).
Process of densification by treating under the condition of kg / cm ² .

In this method, kaolin and activated clay are used as main raw materials. The kaolin used here contains mineralogical kaolin minerals, that is, minerals such as kaolinite, dickite, nacrite, halloysite, and metahaloisite, and the content of SiO ₂ and Al ₂ O ₃ is approximately 40 to 50% by weight, respectively. And any type within a range of 30 to 45% by weight. Activated clay is obtained by subjecting minerals containing SiO ₂ such as montmorillonite and halloysite to acid treatment to remove unnecessary components and increase the content of SiO _2.
As long as the content of O ₂ is high, it can be used irrespective of the production method. Preferably, the content of SiO ₂ is 98% by weight or more. Further, the content of Fe ₂ O ₃ contained as an impurity in kaolin or activated clay is preferably 0.3% by weight or less from the viewpoint of coloring the product and electrical properties.

Kaolin and activated clay are mainly sources of SiO ₂ and Al ₂ O ₃ , and the ratio of kaolin and activated clay is 0.5 to 5.0, preferably 1.5 to 5.0, by weight (kaolin / activated clay).
In the range such that 2.6, SiO ₂ 35 to 60 wt% in the chemical composition in the calcined body (machinable ceramics), Al ₂
Although O ₃ is used in an amount of 10 to 20% by weight, it does not prevent SiO ₂ or Al ₂ O _{3 from} being mixed from other raw materials. In the present invention, the contribution of the kaolin raw material to the amount of Al ₂ O ₃ component in the fired body is 95% or more, and the total contribution of kaolin and activated clay to the amount of SiO ₂ component is 80%.
% Or more.

In order to generate FP, a compound containing Mg, K, and F as an auxiliary material in addition to kaolin and activated clay is used. The auxiliary materials used here are not particularly limited, and usually available compounds such as MgO, KF, and K ₂ SiF ₆ are arbitrarily added in such an amount that the chemical component composition in the fired body falls within the above range. They can be used in combination.

When the component composition at the time of making each of these raw materials into a fired body is represented by oxide weight basis, SiO ₂ 35 to 60%, Al ₂ O ₃ 10 to 2
0%, MgO 10 to 25%, K ₂ O 3 to 15%, F 2 to 15%, and B ₂ O _{3 to} 1 to 3%. And pulverize so that the particle size is 5 μm or less. If any of the above components deviates from the limited range, the amount of FP crystals deposited and grown changes, and the machinability and sinterability deteriorate. For example, if the amount of SiO ₂ is too large, the amount of glass increases and the amount of FP crystals decreases, so that the machinability and heat resistance deteriorate. Conversely, if the amount of SiO ₂ decreases, the amount of FP crystals increases but the sinterability deteriorates. Also, depending on the component ratio, by-products such as forsterite and leucite are generated, and the physical properties of the obtained glass ceramics are deteriorated.

If the pulverization is insufficient and the average particle size exceeds 5 μm, or if the mixing is insufficient, it is not preferable because mineral phases such as leucite are easily generated during calcination or firing.

The maximum temperature of the obtained fine particle material mixture is 1,000 to 1,100
Calcination is performed under the first heat treatment condition of 30 ° C. to produce FP crystals of 30 to 60 vol%, and this heat treatment step is preferably performed in three stages as follows. That is, first at 350-600 ° C
By holding for 10 hours, dehydration of the bound water of kaolin is mainly performed, then holding at 700-900 ° C. for 1-10 hours to carry out a solid phase reaction at the grain boundaries of each particle, and to remove fine FP crystals. Partial precipitation, and then at 1,000-1100 ° C for 1-1
By holding for 0 hours, FP crystals are deposited and grown. The size of the FP crystal is preferably 1 to 2 μm in consideration of the uniform dispersion of the FP crystal during growth. If the maximum temperature is less than 1,000, FP generation is not sufficient, the amount of FP in the fired body is reduced, and firing shrinkage in a subsequent step is increased. If the maximum temperature exceeds 1,100 ° C., sintering proceeds and the pulverizability of the calcined body and the sinterability of a compact using the pulverized calcined body are deteriorated.

Specific heat treatment conditions are appropriately set such that the amount and size of the FP crystals fall within the above-mentioned ranges according to the type of raw materials used, the mixing ratio, and the like.

Next, the obtained calcined body is pulverized so that the average particle size becomes 5 μm or less, and a desired molded body is obtained using the calcined body fine particles. The molded body is heated at a maximum temperature of 1,100 to 1,250 ° C. Sintering is performed under the second heat treatment condition to obtain a sintered body in which FP crystals having a size of 5 to 20 μm are entangled with each other and the gap is filled with a vitreous matrix. There is no particular limitation on a method for obtaining a desired molded body, and depending on a desired shape, moldability, productivity, etc., for example, a uniaxial pressure molding method, a slip casting method,
Each molding method such as an extrusion molding method and a cold isostatic pressing method may be appropriately applied, and if necessary, an appropriate amount of a molding aid such as a binder or a dispersant may be used.

The holding time at the maximum temperature of the second heat treatment condition is preferably 3 to 12 hours, and if it is less than 3 hours, unevenness occurs due to a delay in temperature rise inside the fired body, and if it exceeds 12 hours,
FP crystals grow too much and the strength of the fired body decreases.

The fired body obtained here is SiO ₂ 35
6060%, Al ₂ O ₃ 10-20%, MgO 10-25%, K ₂ O 3-1
A glass ceramic having a component composition of 5%, F 2 to 15%, and B ₂ O _{3 to} 1 to 3%, and containing 30 to 60% by volume of FP crystals, and having a size of 5 to 20 μm in a vitreous matrix. FP crystals are uniformly dispersed and entangled with each other. The bulk density of this product is 2.48 to 2.55 g / cm
^{3. The} true density is 2.66 to 2.68 g / cm ³ and the porosity is 4 to 7%.

Next, the obtained fired body is subjected to HIP treatment for 30 minutes to 5 hours at a maximum temperature of 800 to 1,000 ° C. and a maximum pressure of 500 to 2,000 kg / cm ² .

The conditions may be appropriately set depending on the shape, size, and the like of the fired body to be HIPed.

If the temperature and pressure setting conditions deviate from the lower limits of the above ranges, it is difficult to densify, and if the temperature exceeds the upper limit, in the case of temperature, decomposition of crystals, deformation due to softening of glass may occur, which is not preferable. In such a case, productivity decreases because the volume in the container becomes small.

By this treatment, the pores in the fired body are reduced, and 2.66 to 2.68
A densified machinable ceramics having a bulk density of about g / cm ³ which is close to the true density can be obtained. The workability is HI
Although slightly reduced by the P treatment, it still has better machinability than glass ceramics obtained by the glass melting method, and the gas absorption / desorption performance measured by the test method described later is 10 ^-9 atm · cc / sec. It is a base and shows excellent characteristic values. In addition, the bending strength increases accompanying densification, and increases by about 50% before and after HIP treatment.

Further, as another embodiment of the present invention, SiO ₂ is prepared on the basis of oxidized weight by sintering a raw material powder obtained from a raw material mainly comprising a metal alkoxide compound according to the method described in JP-A-62-7649. 35-60%, Al ₂ O ₃ 10-20%, MgO
There is a method of performing HIP treatment on FP glass ceramics having a composition of 10 to 25%, K ₂ O 3 to 15%, and F 2 to 15%.

In this case, although the machinability is slightly low due to the difference in the composition and crystal state of the FP-based glass ceramic, it has sufficient characteristics as a machinable ceramic. Further, the method of the present invention can be carried out using FP-based glass ceramics manufactured by various methods, and the glass ceramics shown in the first embodiment exhibits particularly good effects.

(Examples) Hereinafter, the method of the present invention will be described more specifically with reference to examples.

Note that the machinability of the fired body and the fired body after HIP were evaluated by the ease of cutting with a drill. In other words, using a carbide drill with a diameter of 5 mm, with a load of 5 kg and a rotation speed of 435 rpm
The evaluation is based on the time required for cutting to a depth of 10 mm, and the shorter this time is, the better the machinability is judged.

The gas adsorption and desorption properties were determined using MIL-STD-
202E In accordance with Test Method C IIIa for electronic and electrical parts, place a sample in a pressurized tank and set the He gas pressure to 4 to 6 kg / cm.
^2. After adsorbing gas under the condition of pressurization time about 4 hours,
The sample was taken out, and the sample obtained by removing the He gas adhering to the sample surface using hot air from a hair dryer was put into a vacuum tank, and the outgassing He gas was detected by a leak detector to evaluate the sample.

(Example 1) By weight percentage, kaolin 40.8%, activated clay 22.9%,
MgO 16.0%, K ₂ SiF ₆ 11.5%, KF 6.8%, B ₂ O ₃ 2.0
%, Mixed and pulverized using a wet ball mill to an average particle diameter of 3.7 μm, dried with a spray drier, then at 380 to 420 ° C. for 4 hours, at 730 to 770 ° C. for 6 hours, and further
Calcination was performed at 1,060 to 1,090 ° C for 3 hours. In the obtained calcined body
The amount of FP crystals was about 50 vol% and the size was about 1 μm.

1.0% by weight of PVA-based binder as a molding aid in the calcined body
And water were added, and the mixture was pulverized to an average particle size of 3.5 μm by wet pulverization, and then dried and granulated with a spray drier.
Using the obtained granules, it was uniaxially pressed at a pressure of 700 kg / cm ² to obtain a plate-like molded body of 260 mm × 260 × 20 mm, which was baked at 1,200 to 1,250 ° C. for 5 hours through a degreasing process according to a conventional method. . The average component composition of the obtained fired body is based on the weight of the oxide.
SiO ₂ 45.7%, Al ₂ O ₃ 16.1%, MgO 16.7%, K ₂ O 10.
9%, F 8.5%, B ₂ O ₃ 2.0%, containing about 50 vol% of FP crystals having a length of 5 to 15 μm in a vitreous matrix, bulk density 2.50 g / cm ³ , machinability 30 sec / cm , Bending strength
It was 1,100 kg / cm ² and the He gas adsorption / desorption amount was 2.3 × 10 ⁻⁷ atm.cc/sec.

Next, the fired body was pressed at a pressure of 1,000 kg / cm ² and a maximum temperature of 900 kg / cm ^2.
HIP treatment was performed at 2 ° C. for 2 hours. The physical properties of the obtained fired body after HIP are as follows: bulk density 2.67 g / cm ³ , true density 2.68 g / cm ³ , He
Gas adsorption / desorption amount 7.6 × 10 ^-9 atm.cc/sec, machinability 36sec / c
m, and the bending strength was 1,630 kg / cm ² .

Further, using the fired body produced by the above method, HIP
The average bulk density before and after HIP and its variation (standard deviation: σ) when the maximum pressure is 1,000 kg / cm ² and the maximum temperature is changed are shown below. This shows that a product of stable quality can be obtained.

(Example 2) Raw material powder obtained from the raw materials according to the method described in JP 62-7649 discloses mainly a metal alkoxide compound was prepared by sintering, SiO ₂ 48.8% on an oxide weight basis ,
Al ₂ O ₃ 18.3%, MgO 17.8%, K ₂ O 10.9%, F 4.2%
Machinable ceramics with the composition of
The result of HIP treatment at 000 kg / cm ² is shown below.

The maximum temperature of gas adsorption and desorption is 900 ° C due to HIP treatment.
5.8 × 10 ^-7 atm ・ cc / sec to 6.4 × 10 ^-8 atm ・ cc / sec
It became.

(Effects of the Invention) The effects of the present invention are listed as follows.

(1) A material having a bulk density almost equal to the true density can be obtained by a sintering method which is a simpler process without using the glass melting method.

(2) The gas adsorption / desorption amount is on the order of 10 ^-9 atm.cc/sec, and is sufficiently applicable to applications under a vacuum atmosphere.

(3) Since it has extremely good machinability, fine processing and precision processing can be easily performed.

(4) Stable quality products can be manufactured.

(5) Unlike the glass melting method, a material having a shape close to the intended product can be obtained, so that material loss is small.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-143869 (JP, A) JP-A-1-197358 (JP, A) JP-A-2-233554 (JP, A) JP-A-56-143 69272 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/00-35/22

Claims (1)

(57) [Claims] 1. A method for producing dense machinable ceramics, comprising the following steps in the order mentioned. When kaolin and activated clay are used as main raw materials, Mg, K, and F-containing compounds are used as auxiliary raw materials, and B ₂ O ₃ is used as a sintering aid, and the component composition at the time of forming a fired body is expressed by oxide weight basis, ₂ 35-
_{60%, Al 2 O 3 10~20} %, 10~25% MgO, K 2 O 3~15
%, F 2-15%, and B ₂ O ₃ 1-3%. The maximum temperature of the fine particle raw material mixture was adjusted to 1,000-1,100 ° C.
Calcined under the first heat treatment condition of
A step of obtaining a calcined body containing fluorophlogopite and glass containing 30 to 60 vol%. After pulverizing the calcined body into fine particles, a desired molded body is formed using the calcined body fine particles, and the maximum temperature of the molded body is 1,100.
A step of sintering under a second heat treatment condition of ~ 1,250 ° C to obtain a fired body. The maximum temperature of the fired body is 800 by hot isostatic pressing.
~ 1000 ° C., the step of highest pressure is densified by treatment under conditions of 500~2,000kg / cm ^2.