JPH0159231B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a ceramic sintered body with excellent machinability, which is completely different from conventional ceramic sintered bodies, and a method for manufacturing the same. [Prior art and its problems] Conventional ceramic products, with very few exceptions, generally have high hardness and brittle characteristics. Glass, ceramics, enamel, refractory bricks with some exceptions, carbon products, etc. almost all have the above characteristics, so once the molded product is fired,
It is now very difficult to cut or process it into a free shape. However, if a special tool such as a diamond cutter is used, the purpose of cutting into a somewhat free shape can be achieved. However, a diamond cutter is an expensive tool, and processing using it takes a long time and requires a great deal of effort, so it has the drawback of being extremely uneconomical. In other words, it can be said that, in general, there are no conventional ceramics that can be easily cut. Therefore, what we mean by machinability is a property that is generally accepted as a socially accepted characteristic. We can cut, cut, and drill holes smoothly into any shape without causing damage.
This indicates that trench digging etc. can be done. In addition, as exceptions to some of the above materials, such as insulating bricks and lightweight aggregates, there are materials that can be cut with the above-mentioned tool with a cutting edge made of ordinary carbon steel, but these materials are completely unusable. It is different from machinable ceramics as defined above, as it is made for a different purpose. More specifically, to explain conventional products mainly in terms of machinability, general ceramic sintered bodies, for example hard porcelain, have a main crystalline phase of mullite (3Al ₂ O ₃ .
2SiO ₂ ), quartz (SiO ₂ ), etc. are bonded together by an alkali glass phase, and the raw material crystalline material before sintering is decomposed by heating, reacts and eutectic, and forms another crystalline phase. It has a glass phase and has a Mohs hardness of 7 or higher, making it a hard and brittle material with low toughness, so it has the disadvantage of being almost impossible to process with normal carbon steel tools. Also, so-called oxide ceramics, such as alumina and zirconia porcelain, are microcrystalline sintered bodies and have high strength, but their Mohs hardness is 8 or higher, so they are difficult to use with normal carbon steel tools. . Furthermore, the only prior art that is close to the above-mentioned machinability is Corning's mica glass ceramic under the trade name "Macol", which is said to have some machinability. Yes, but the actual product is
30 to 40% crystallized glass phase of KMg ₃ AlSi ₃ O ₁₀ F ₂
Therefore, carbon steel tools are difficult to sharpen when cutting, are easily broken, and soften and deform at approximately 800°C, and rather have multiple drawbacks as a ceramic product. . [Object of the present invention] The present invention overcomes the various drawbacks of the prior art, while retaining the inherent advantages of ceramics, such as fire resistance and bending strength, to a considerable extent, while also having excellent machinability properties. The purpose of this invention is to provide a ceramic sintered body, in other words, a type of new ceramic material, which is not found in other countries, and also to disclose a method for producing the same. [Summary of the structure of the present invention] (1) The ceramic sintered body with excellent cutting workability according to the present invention contains the above-mentioned element 1, that is, βCaO・SiO ₂ and element 2, that is, mica group mineral, and has a plate shape or a leaf shape. Contains at least 60% by weight of aggregates or crystals, of which at least 30% by weight is βCaO.
It is characterized by being made of SiO ₂ and sintered to a Mohs hardness of 5 or less. (2) The method for producing a ceramic sintered body with excellent machinability according to the present invention uses a raw material containing element 1 or a raw material containing element 2, both of which have a Mohs hardness of 5 or less, as a sintered body base. Blend so that the total of Element 1 and Element 2 is 60% by weight or more, of which at least 30% by weight is βCaO・SiO ₂ , and adjust the crushing and mixing to the extent that the original shape of the elemental piece or crystal, such as a plate, is approximately retained. After being molded, the material is sintered to a Mohs hardness of 5 or less at 1200° C. or less to maintain approximately the original shape. To further explain the requirements of the present invention in detail, βCaO SiO ₂ is a main component of wollastonite, for example, and is an aggregate of well-developed triclinic plate-shaped crystals, and is either natural or artificial. be. Mohs hardness is 4.5 to 5, and if heated below 1200℃, α
Since it does not become a monoclinic granular crystal (with a Mohs hardness of 5 or more) and retains almost its original shape, it can be used as Element 1. Mica group minerals are plate-like fragments or crystals that can be seen with the naked eye, and there are many types such as phlogopite, phosphomica, and sericite. For example, phlogopite is a monoclinic crystal of the chemical component KMg ₃ (Si ₈ Al) O ₁₂ It is a type of plate-shaped crystalline mineral with a Mohs hardness of 2.5 to 3, and it occurs naturally, and is also made into artificial products as a by-product of fertilizer production. Another example of a mica group mineral is vermiculite (MgFe) ₃
(AlSi) ₄ O ₁₀ (OH) ₂ is a monoclinic leaf-shaped crystal with a chemical composition of 1.5 on the Mohs hardness and dehydrates and expands when heated above 750°C, so it has traditionally been used as a raw material for lightweight aggregate. This is what I was looking for. Next, talc is a monoclinic leaf-shaped mineral with a chemical composition of Mg ₃ (Si ₄ O ₁₀ ) (OH) ₂ , which is the softest with a Mohs hardness of around 1, and has traditionally been used as a raw material for electrically insulating ceramics. It is used after being fired at temperatures exceeding 1200℃. Furthermore, artificial synthetic mica can be produced by electrofusion and can be used as element 2 of the structure of the present invention. A requirement for the above-mentioned main raw materials used as raw materials in the present invention is that they have a plate-like or leaf-like shape. It is desirable that the value obtained by dividing the dimension by the thickness (hereinafter referred to as aspect ratio) is 5 or more. The reason for this is that stones with this value of less than 5 are similar to normal stone blocks, and even if they are used, the characteristic effects of the product of the present invention are not obvious. The ceramic sintered body with excellent machinability according to the present invention is made from a raw material containing the above-mentioned elements 1 and 2 and has a material structure that retains or retains these elements in their original shape, and the sum of the above-mentioned two elements is is at least 60% by weight, of which at least 30% by weight is of Element 1. As shown in Example 1 and Table 1, the ceramic sintered body according to the present invention has a Mohs hardness of 4.9 when the sum of the above elements is 60% based on the sintered body.
It is about 5, and if the content of the element is increased, it becomes 100.
This is because the Mohs hardness decreases up to around 4%, and conversely, as the content decreases, the Mohs hardness gradually increases, so to speak, there is an inversely proportional relationship. Furthermore, the ceramic sintered body according to the present invention is sintered at a relatively low temperature (below 1200°C) for ceramics, and during molding, the compound is in close contact with the plate-shaped sliding surface with orientation. Regarding the sintering,
Plate-like crystals that are bonded by mutual solid-state reactions and retain their original shapes are brought into close contact by Van der Vuard's force at the plane interface, and the part of the close contact is partially formed by solid solution or eutectic crystals. It is presumed that this is due to the material structure. For this reason, although it is a shaped sintered product as a whole, it retains elements 1 and 2 almost as they are, so the cutting edge is made of ordinary carbon steel as defined in the prior art section. The cutting workability of the tools used is excellent based on conventional wisdom. Next, a method for manufacturing a ceramic sintered body having excellent machinability according to the present invention will be explained. To do this, first, the purity of the raw material containing the above-mentioned Element 1 and/or Element 2 used in each case is confirmed by conventional chemical analysis or X-ray analysis. Also, from the results obtained in this way, the sintered body base is calculated from the moisture content and the loss on ignition at about 1000°C. Since these pre-processing parts are normal methods, the details will be omitted. Therefore, based on the sintered body, the total of element 1 and element 2 is 60
% by weight or more, of which at least 30% by weight
The raw materials are mixed so that βCaO・SiO ₂ is obtained. By the way, the sintering reaction of ceramics at industrial sites is not very precise, so from experience the yield to reach the above 60% is approximately 1.
You need to take a close look. This is for example element 1
This is because a small amount of βCaO・SiO ₂ may partially transform into α. Therefore, the composition calculation should be performed assuming that the sum of Element 1 and Element 2 is about 66 to 67% or more based on the sintered body. In particular, in cases where the sintering operation can be carried out in a furnace that allows very precise temperature and time control, the yield is
Depending on the accuracy, it is necessary to look a little. When using vermiculite, it should be fired in advance at a temperature of about 800℃ to 1200℃ because it will expand. Further, as another example of element 2, one containing crystals such as ZnO, TiO ₂ , BaO, MgO, etc. may be used. Further, in order to facilitate the shaping of the raw material, it may be better to add a shaping aid and/or a sintering reaction accelerator. For this purpose, it is preferable to use plastic clay such as Frog's eye clay and/or glue material such as silica sol in an amount of about 3 to 5% of the total amount. These raw materials are dried and blended to form element 1,
The material is crushed and/or coarsely pulverized to the extent that the shape characteristics of element 2 are approximately maintained, and further estimated from the properties of the material.
At an appropriate temperature of 1200℃ or lower and 800℃ or higher, element 1 and element 2.
Sintered to the extent that it retains its original shape. Through such operations, as described above, the plate-like material becomes layered due to the orientation during raw material preparation, and a sintered product with a closely-adhered material structure is obtained due to the van der Vuar force. Since the sintering temperature of these sintered products is relatively low, the content of glassy substances is extremely small, and they contain Element 1 and Element 2 in a form close to their original form. In addition, since these elements have a Mohs hardness of approximately 5 or less, almost all of the ceramic sintered products have a Mohs hardness of 5 or less, and are excellent in workability with a tool having a cutting edge of carbon steel. The present invention will be explained in more detail with reference to Examples below. Example 1 A raw material containing equal amounts of βCaO/SiO ₂ and phlogopite is prepared using the above-described conventional method, and the total of the two is increased from 30% to 100 (%) on a sintered product basis.
(%) Blended at intervals of 1100 to 1200℃
Sintered with Next, using X-rays and an electron microscope, it was confirmed that the total amount of Element 1 and Element 2 was approximately as shown in Table 1, and the Mohs hardness was measured. The Mohs hardness of Element 1 and Element 2 relative to the total weight (%) is as shown in Table 1 below, and in order to obtain a sintered product with a Mohs hardness of 5 or less, the total of Element 1 and Element 2 must be approximately It was found that it is sufficient to have a weight (%) of 60% or more.

[Table] Example 2 Natural wollastonite from India crushed to 40 (metsushi) or less, Chinese phlogopite crushed to 20 (metsushi) or less,
Talc and clay were powders with a particle size of 80 (metsushi) or less, and samples were prepared according to the following blending ratio. Wollastonite 50% by weight Phlogopite 10 Talc 10 Frog's eye clay 30 This mixture was processed by wet extrusion molding.
That is, kneaded clay with a moisture content of 23 (%) was extracted using a vacuum clay kneading machine into a cylindrical shape with a diameter of 200 (mm) and a wall thickness of 25 mm, and rolled and rolled to have a width of 300 (mm), a length of 600 (mm), and a thickness of 10 mm. (mm)
A large number of plate-shaped bodies were molded, dried, and fired in a roller hearth kiln at 1150 (°C) for 1 hour. Ten (sheets) of these sintered bodies were randomly selected and their properties were tested, and the results are shown in Table 2.

[Table] The total of Element 1 and Element 2 was tested by X-ray etc. and the result was 69 (%). These sintered bodies can be easily drilled with a carbon steel drill, cut with a wood saw, and do not soften and deform even at a fire resistance of 1230 degrees Celsius. Furthermore, a 1 (Kg) steel ball is lifted from a height of 30 (cm).
It was found that the material has such toughness that it will not break even if it is dropped onto the center of the board surface. Example 3 The degree of pulverization depending on the type of raw materials was the same as in Example 1, and samples were prepared using the following blending ratios. Wollastonite 47 weight (%) Calcined vermiculite (calcined at 800℃) 30 〃 Lepidolite 10 〃 Murakami clay (sericite) 10 〃 Silica sol 3 〃 These mixtures were made into powdered clay with a moisture content of 10% and processed by dry process. By pressure forming method, 200 (Kg/
cm ² ) pressure into a plate shape of 100 (mm) x 200 (mm) x 10 (mm). After drying, it was heated in a roller hearth kiln at 1100°C.
After firing for 1 hour, the following sintered body was obtained. Of these
Ten sheets were randomly selected and tested. The result is the third
As shown in the table.

〔Effect of the invention〕

(1) The ceramic sintered body according to the present invention is made by blending plate-shaped, leaf-shaped, etc. elemental pieces or crystals contained in the raw materials while keeping substantially their original shapes, or by containing the original shapes. Since they are sintered and their original form has a Mohs hardness of 5 or less, this sintered product also has a Mohs hardness of 5 or less. As a result, the ceramic product according to the present invention is soft and has high toughness, and its bending strength is as strong as that of conventional ceramics.It retains the good qualities of conventional ceramics, eliminates the disadvantage of brittleness, and provides toughness. This is an extremely interesting and promising ceramic product that has never been seen before. (2) Ceramics with such novel properties create new uses or new modes of use for conventional ceramic products. For example, if the properties of conventional ceramics are maintained, tiles and the like are made by firing a large number of small-sized pieces and pasting them on the exterior walls of buildings, which is a time-consuming process.However, the ceramic products according to the present invention have particularly high toughness. Because it is large, it is possible to manufacture large-sized products, and when it comes to pasting and using it, it saves many times more effort than when considering the same area, and productivity is greatly improved. (3) The ceramic product according to the present invention eliminates the hard and brittle defects of conventional ceramic products,
Since it is soft with a Mohs hardness of 5 or less, it has particularly excellent machinability, and from that aspect, it can be applied to a wide range of new fields such as electroceramics or engineering ceramics, and has a wide range of future prospects. It can be said that it is extremely large.

Claims (1)

[Claims] 1 A total of 60 plate-like or leaf-like pieces or crystals containing βCaO・SiO ₂ and natural mica group minerals.
A ceramic sintered body having excellent machinability, characterized in that it contains at least 30% by weight of βCaO·SiO ₂ and is sintered to a Mohs hardness of 5 or less. (Hereinafter, βCaO SiO ₂ will be referred to as element 1, and plate-shaped or leaf-shaped fragments or crystals containing mica group minerals will be referred to as element 2.) 2. Raw materials containing the above element 1 and having a Mohs hardness of 5 or less; One or more of the raw materials containing Element 2 and having a Mohs hardness of 5 or less, the total of Element 1 and Element 2 is 60% by weight or more based on the sintered body, of which at least 30% by weight is βCaO・SiO ₂ After mixing and crushing to the extent that the original shape of the plate-like or leaf-like elements or crystals is approximately retained, and after molding, the mixture is heated at 1200°C to the extent that the original shape is approximately retained.
A method for producing a ceramic sintered body having excellent machinability, which comprises sintering to a Mohs hardness of 5 or less.