JP2000203949A - Processing method of ceramics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for processing a ceramic, which is comprised of precisely processing a green body comprising a source powder of the ceramic and a binder, having low strength and being not yet sintered or a calcined body and by which a high accuracy ceramic article can be easily produced through precise processing. SOLUTION: The ceramic green body obtained by mixing a source powder for a ceramic and a binder and compacting or a calcined body obtained by calcining the ceramic green body at a temp. lower by 20-30% of the sintering temp. than the sintering temp. is fixed and then the surface layer of the green body or the like is subjected to cutting processing while rotating a tool at high speed, to which one or a plurality of cutting blade parts 5 are attached. Thereafter, the green body or the calcined body is sintered. The ceramic green body or the calcined body may be moved or rotated at low speed, or the tool can be moved. The ceramic green body formed by any of mold pressing, isostatic pressing, extrusion molding, slip casting or injection molding can be utilized to this method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dry processing method for obtaining high-precision ceramics.

[0002]

2. Description of the Related Art In order to make ceramics into parts or products, it is necessary to finish them to predetermined shapes, dimensions and accuracy. However, since sintered ceramics are generally hard and brittle materials, it is extremely difficult to cut them by mechanical processing or to plastically deform them like metals and the like. In addition, the cost tends to be high even when processing, so it is desirable to reduce the processing amount as much as possible.

Therefore, in general, it is necessary to predict the amount of shrinkage and deformation during sintering of ceramics at the molding stage of the material before sintering so that the ceramics have a predetermined shape, size and accuracy. Usually, ceramics are manufactured by the following method.

[0004] First, a molding raw material composed of a mixed powder raw material of a ceramic main raw material, a sintering aid, and an organic binder is subjected to a dry pressing method using a mold, a hydrostatic pressure method, an injection molding method, a casting method or an extrusion molding method. And the like.

When molding is insufficient, the molded body is processed so as to be close to a predetermined shape. Furthermore, in the case of a product requiring high dimensional accuracy in a hole or groove, or a complicated shape, etc., after calcination for 1 to 4 hours at a temperature 20 to 30% lower than the temperature at which the molded body is sintered, In some cases, a processing method is used.

[0006] In this way, after the sintering is processed into a shape close to the final product, sintering is performed. In order to further improve the accuracy, after sintering, processing such as polishing has been performed to finish to predetermined dimensions.

[0007]

The processing of the compact or calcined body is, for example, if the product is cylindrical, fix the compact on a lathe and rotate it to form a cylindrical compact. There is a method in which the inner and outer peripheries are ground with a fixed cutting tool.

At this time, if the rotation speed of the workpiece is low, the cutting speed of the cutting tool is relatively high, so that the cutting resistance is large, the processing surface is rough, and the processing time is long. Conversely, if the number of rotations is increased, the compact may be broken because centrifugal force acts on the compact. Further, the chucking force on the lathe must be increased, and the molded body may be deformed by the force.

[0009] In the processing of a shaped article or a block-like shaped article, a plane, a groove or a side face is processed by a rotating tool having a large number of blades, which is fixed to a table surface by a milling machine or the like.

At this time, the conventional rotation speed of 1000 revolutions / minute (hereinafter, referred to as “revolution speed”)
At rotation speeds less than (rpm), cutting powder tends to accumulate between the workpiece and the blade, and the cutting resistance is large.
It was easy for dropping or splintering of the processed end.

Although the strength of the molded body can be obtained by the organic binder added to the ceramic raw material, the strength of the molded body that can be added is limited, and it is difficult to obtain a material strength that can withstand cutting. For these reasons, in the processing of the molded body, the material strength is weak, and there is a difficulty in handling properties and workability.

Therefore, as described above, in order to increase the strength of the molded body, there is a method in which the molded body is calcined at a temperature 20 to 30% lower than the firing temperature for 1 to 4 hours and then processed. However, in this method, there is a problem that the number of calcining steps is increased, and that the workpiece is hardened by the calcining, and the hardness is not stable depending on the raw material, the molding lot, and the calcining lot. Further, since the hardness increases by calcination, heat generation and wear of a tool such as a fixed cutting tool are significantly increased, and workability is reduced.

[0013] Therefore, in the case of the calcined product, it is difficult to perform machining with a blade, and therefore, in many cases, grinding is performed using a grindstone instead of the blade. However, in the grinding process, the processing amount is small, and clogging easily occurs on the surface of the grindstone, so that the processing time becomes long. Further, heat generated by processing friction is large, which causes cracking of the workpiece.

In view of such a situation, an object of the present invention is to enable a precision processing to be easily performed even on a molded body or a calcined body having a low material strength before sintering comprising a ceramic powder raw material and a binder. Accordingly, it is an object of the present invention to provide a ceramic processing method capable of manufacturing a high-precision ceramic product.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a ceramic molded body obtained by mixing and molding a ceramic powder material and a binder, or a ceramic molded body having a temperature lower by 20 to 30% than a firing temperature. The calcined body calcined in the above is held, and its surface layer is cut by a tool having a blade part rotating at high speed, and then calcined. The ceramic molded body and the calcined body may be moved or rotated at a low speed, or the tool may be moved while fixing the ceramic molded body and the calcined body. The formed body of the ceramic may be formed by any of die press molding, isostatic press molding, extrusion molding, injection molding.

If one or several processing blades are mounted around the rotating shaft and rotated at a high speed for cutting, the cutting amount cut by the blade at one time is small, so that the cutting resistance is reduced and the cutting part is reduced. The force applied to other areas is small. Even a workpiece having a low bonding strength, such as a molded article, can be processed without giving a destructive force to the workpiece.

Although the amount of cutting per rotation is small,
Since the rotation speed is high, the amount of cutting per unit time increases, and the feed speed for cutting can be increased,
Cutting time can be shortened.

When the blade rotates at a high speed, an airflow is generated around the blade, and the airflow removes cutting chips from the cutting surface, so that the cutting resistance is constantly reduced. In addition, the airflow also has the effect of cooling the blade and suppressing a rise in the temperature of the blade. Rotation speed of compact and calcined body is 1000rp
If it is less than m, the centrifugal force can be small, so that even a workpiece having a low bonding strength will not be deformed.

The ceramic bodies, calcined body than any soft ceramics, for example, the Vickers hardness is less than 800H _V, machinable ceramics, etc. In the porous ceramics, by cutting with a tool rotating at a high speed, since the cutting resistance is reduced Can be processed.

The rotation speed of the rotating tool is preferably 2000 rpm or more. When the rotation speed is 2000 rpm or more, the cutting resistance is reduced, so that the processing speed can be increased. For example, the relative speed between the rotating tool and the workpiece is 50 mm / mi.
What can be set to n or more is as described in the examples below.

[0021]

Embodiments of the present invention will be described below. In addition, the ratio of the content is set to mass% unless otherwise specified. [Embodiment 1] This embodiment will be described with an alumina ceramic material.

First, an alumina ceramic of 85 to 100% containing silicon oxide (SiO ₂ ), magnesium oxide (MgO) and calcium oxide (CaO) is prepared, and polyvinyl alcohol (hereinafter referred to as P) is used as a binder.
VA), a softener and the like were added, and wet pulverization was performed, followed by granulation and drying with a spray drier to obtain a forming raw material.

The molding raw material is press-molded with a mold,
An angular annular molded body 11a having the cross-sectional shape of FIG. 2A was obtained. The dimensions of the molded body 11a are an outer dimension of 163 × 163, an inner dimension of 142 × 142, and a height of 30 mm. The molded body 11a in FIG. 2A was pressed and fixed to a table of a milling machine from above and below, and the outer peripheral portion of the molded body 11a was cut into a corrugated shape by the tool in FIG.

FIG. 1 is an external view of a tool 13 used for the machining. A blank having a corrugated polycrystalline artificial diamond layer was prepared and brazed to a steel table to obtain a cutting tip 15. Two of the cutting tips 15 were mounted on a diagonal line of the milling holder 14 with fixing screws 16. The outer diameter of the tool 13 after the attachment is 50 mm. The tool 13 was mounted on a spindle of a milling machine capable of rotating at 10,000 rpm or more, and was rotated for processing.

FIG. 2B is a sectional view of the formed body 11b after processing. The outer peripheral portion was formed into a rectangular ring with three folds 12 having a corrugated shape. The thickness of the fold 12 is 2.5
mm, length 6 mm, interval 2.5 mm.

In this machining, the rotation speed of the tool 13 is set to 1
When the feed speed of the molded body is 30 mm / min and the cutting depth is 6 mm, the fold 12 is cracked.
Dropped from the molded body. When the feeding amount is 3 mm,
6mm processing was completed by two processings. Of course, it could be processed three or more times.

When the number of revolutions is increased to 2000 rpm, cracks and falling off of the folds 12 are eliminated at a feed rate of the compact of 30 mm / min and a cutting depth of 6 mm. However, when the processing feed speed was set to 200 mm / min, the fold 12 was cracked and dropped from the molded body.

Further, when the molding was processed under the same conditions of a rotation speed of 4000 rpm, a feed speed of the molded body of 30 mm / min or more, and a cutting depth of 6 mm, no cracking or falling off occurred. The maximum feed rate that can be processed was about 500 mm / min. When the number of revolutions was set to 10000 rpm, the cutting amount was 6 mm,
The maximum feed rate that could be processed was 1000 mm / min, and there was no cracking or falling off during processing.

As described above, by increasing the number of rotations of the blade rotating at a high speed, the amount of cutting per rotation is small, but the amount of cutting per unit time is increased. And cutting time can be shortened. In addition, since the cutting amount that the blade cuts is small, the cutting force is small and the force applied to the periphery other than the cut portion is small, so even if the work has a weak bonding strength such as a molded body, the work may break. It can be processed without giving force.

When the blade rotates at a high speed, an airflow is generated around the blade, and the airflow removes cuttings from the cutting surface, so that the cutting resistance is always reduced. The airflow also has the effect of cooling the blade and suppressing a rise in the temperature of the blade.

Further, the processed molded body 11b shown in FIG.
Was fired at 1600 ° C. for 2 hours. It was shrunk by about 20% during the firing. In this way,
A precise ceramic square ring was obtained. [Example 2] The outer shape of the molded product obtained in Example 1 (external size 16
3 × 163, inner size 142 × 142, height 30mm)
Heat treatment was performed in air at 50 ° C. for 1 hour to form a calcined body, and after improving the material strength, processing was performed with a milling machine using the cutting tool of FIG. In addition, there is almost no dimensional change in the calcination under the above conditions.

Since the calcined body is a material that is considerably harder than the molded body, the amount of cutting is smaller than the processing of the molded body.
The rotation of the tool is set to 1000 rpm and the machining feed rate is set to 30 mm.
When the cutting depth was 6 mm / min and the cutting depth was 6 mm, the cutting resistance was high, and the cutting tool could be damaged.

When the cut amount was set to 2 mm or less, the processing could be performed by performing the processing at least three times while changing the feed amount. However, processing required more than 20 minutes. The cutting speed was set to 6 mm, and the machining was performed at a higher rotation speed in order to perform one machining.

At a rotation speed of 2,000 rpm, the cutting resistance was still high even at a processing feed rate of 30 mm / min, and the folds 12 were cracked or dropped, so that processing was not possible. 4000 rpm
m, cutting depth 6mm, machining feed rate 30mm / mi
When processed under the conditions of n, there was no cracking or falling off. Further, it was possible to set the processing feed rate to 100 mm / min. When the rotation speed is set to 10000 rpm, the maximum feed rate that can be processed without cracking or falling off during processing is about 500
mm / min.

As described above, even in the calcined body obtained by calcining the formed body, the feed speed at the time of working can be increased by increasing the rotation speed. However, the speed was about half that of the compact. Further, the calcined body was fired at 1600 ° C. for 2 hours to obtain a precise ceramic square ring. It should be noted that also in this case, it shrank by about 20% during firing.

Example 3 In the same manner as in Example 1, a raw material for forming an alumina ceramic of 85 to 100% was prepared, and the forming raw material was pressure-formed using a mold.
A circular annular molded body having an outer diameter of 150 mm / inner diameter of 125 mm and a height of 30 mm was prepared.

As the working tool, a blank having a polycrystalline artificial diamond layer was prepared in the same manner as in Example 1, and the blank was brazed to a super steel table to prepare a cutting tip. The two chips were mounted diagonally on a rotary holder to make the cutter outer diameter 50 mm. This tool was mounted on a tool holder capable of rotating at 10,000 rpm or more on a tool holder of a lathe and rotated.

The annular molded body is fixed to a chuck of a lathe,
The rotation speed was 250 rpm, and the tool was rotated in the same rotation direction as the rotation direction of the tool. That is, the traveling direction of the surface portion of the molded body in the processing portion of the molded body is opposite to the traveling direction of the tool portion. As for the processing shape, a thickness of 2.5 mm and a depth of 6 m are provided outside the annular molded body as in FIG.
Three steps of creases were performed with a length of 2.5 mm and an interval of 2.5 mm. In the case of this processing, since the tool moves toward the center of the compact, the speed is referred to as a cutting speed.

In this machining, the rotational speed of the tool is set to 100
When 0 rpm and the cutting speed are 100 mm / min,
Cracks appeared in the folds and dropped from the molded body. By increasing the rotation speed of the processing tool to 4000rpm, the cutting speed 1
At 00 mm / min, cracks did not fall off, and the maximum cutting speed that could be processed was 1000 mm / min.

In this processing, the processing speed of the compact is as low as 250 rpm, so that the chucking pressure on the lathe may be low. Accordingly, since the fixing force, the centrifugal force, and the working resistance at the time of working are small, cracking and deformation at the time of working are eliminated. The compact was fired at 1600 ° C. for 2 hours to obtain a precise ceramic circular ring. It should be noted that also in this case, it shrank by about 20% during firing.

Further, the temperature generated by the heat generated due to the cutting friction may increase the cutting performance of the tool, but since the tool rotates at a high speed during machining, the tool is cooled and Is removed from the cutting surface, so that the cutting tool is less worn than in the case of processing with a fixed cutting tool, the life of the cutting tool is extended, and processing can be performed for ten times or more.

Example 4 After forming an annular molded body in the same manner as in Example 3, the molded body was heat-treated at 1250 ° C. × 1 h in air to obtain a calcined body.

The same processing as in Example 3 was performed on the calcined body. When the rotational speed of the tool was set to 1000 rpm and the cutting speed was set to 50 mm / min, the fold 12 was cracked and dropped from the calcined body.

By increasing the rotational speed of the processing tool to 4000 rpm, even at a cutting speed of 50 mm / min, cracks and falling are eliminated, and the maximum cutting speed that can be processed is 500 mm / min.
/ Min.

Also in this case, by increasing the rotation speed,
The maximum cutting speed can be increased. However, the calcined body was about half of the molded body.

Example 5 The graphite was rotated at 400 rpm using a milling machine in the same manner as in Example 1.
A 50 × 50 mm surface was cut under the conditions of 0 rpm and a cutting depth of 0.3 mm.

Conventionally, at a rotational speed of 2000 rpm or less, 2
A machine that requires a processing time of 0 min or more has a rotation speed of 4000
With rpm, it could be shortened to 5min and 1/4. Therefore, even in these materials, an increase in the number of revolutions has made it possible to improve the machinability.

The same processing was performed on a porous body of machinable ceramics, mullite and a porous body of steatite.

[0049] graphite, the Vickers hardness of the machine fashionable ceramic is a 400~800H _V, mullite,
Vickers hardness of the steatite porous material is 100 to 5
It is a 00H _V. Therefore, the Vickers hardness is 800H _V
If it is the following, it is considered that cutting by the high-speed rotating tool according to the present invention is possible.

[0050]

As described above, according to the present invention, in the cutting of a ceramic molded body and a calcined body, their surface layers are cut by a tool having a blade portion which rotates at a high speed, so that the cutting resistance is reduced. And the cutting performance was improved, the cutting time was shortened, and the occurrence of cracks in the workpiece was reduced.

And, since it became possible to manufacture a high-precision molded body and a calcined body, it was possible to provide a high-precision ceramic product by firing it. Cutting time for soft ceramics was also reduced to about 1/4 of the conventional time.

From these, the present method has an extremely large industrial value as a method for producing a ceramic product with high precision.

[Brief description of the drawings]

FIG. 1 is an external view of a tool having a blade portion.

FIG. 2A is a cross-sectional view of a rectangular ring of Example 1 before processing.
(B) is a sectional view after processing.

[Explanation of symbols]

 11a molded body 11b molded body 12 fold 13 holder 14 chip 15 fixing screw

Claims (10)

[Claims] 1. A ceramic molded body obtained by mixing and molding a ceramic powder raw material and a binder and holding the ceramic molded body, and cutting a surface layer thereof with a tool having a blade part rotating at a high speed.
A ceramic processing method characterized by firing. 2. A ceramic molded body obtained by mixing and molding a ceramic powder raw material and a binder is heated to a firing temperature of 20 to 3 times.
A ceramic processing method characterized by calcining at a temperature lower by 0%, holding the calcined body, cutting the surface layer with a tool having a blade part rotating at high speed, and then firing. 3. A ceramic molded body obtained by mixing and molding a ceramic powder raw material and a binder, is rotated, and its surface layer is cut by a tool having a blade part that rotates at a high speed.
A ceramic processing method characterized by firing. 4. A ceramic molded body obtained by mixing and molding a ceramic powder raw material and a binder is heated to a firing temperature of 20 to 3 times.
A method for processing ceramics, comprising calcining at a temperature lower by 0%, rotating the calcined body, cutting the surface layer with a tool having a blade portion rotating at high speed, and then calcining. 5. The rotational speed of the compact or calcined body is 1000 rp.
The method for processing ceramics according to claim 3 or 4, wherein the value is not more than m. 6. The ceramic body according to claim 1, wherein the ceramic body is formed by any one of a mold press molding, an isostatic press molding, an extrusion molding, and an injection molding. The processing method of the ceramics described. 7. Vickers hardness fixes the following soft ceramic 800H _v, machining method of the ceramic, characterized in that the cutting by the tool having a cutting portion at a high speed rotating the surface layer. 8. The method according to claim 7, wherein the soft ceramic is any one of a carbonaceous material, a machinable ceramic, and a porous ceramic. 9. The method according to claim 1, wherein the rotating speed of the rotating tool is 2000 rpm or more. 10. A rotating tool and a workpiece are set at 50 mm /
The method for processing ceramics according to claim 9, wherein the ceramics is moved at a relative speed of min or more.