JP2013230959A - Manufacturing method of ceramic sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for improving the strength of a ceramic sintered compact used for a cutting tool.SOLUTION: A manufacturing method of a ceramic sintered compact used for a cutting tool includes: a preparation process for preparing slurry that contains raw material powder and a binder having a carbon component; a molding process for molding the dried product of the slurry to obtain a compact; a degreasing process for heating the compact so that carbon may remain therein to obtain a degreased body; an inspection process for inspecting the surface of the degreased body; and a sintering process for calcining the degreased body after the inspection.

Description

  The present invention relates to a method for producing a ceramic sintered body used for a cutting tool.

  Conventionally, a cutting insert using a ceramic sintered body is known as a cutting insert used for a cutting tool for processing a heat-resistant alloy or the like. Various techniques have been disclosed in order to improve the strength and toughness of the ceramic sintered body. For example, a manufacturing method is disclosed in which a mixed powder containing zirconia and alumina is activated by dry pulverization, and then molded and sintered (Patent Document 1). Further, a manufacturing method is disclosed in which the entire pores of the alumina temporary sintered body are impregnated with a solution of a metal salt such as calcium and then sintered (Patent Document 2). Further, a sintered body obtained by adding cobalt and tungsten carbide to alumina powder and sintering it is disclosed (Patent Document 3).

JP-A-1-172262 JP 2001-322865 A JP-A-9-316589

  However, even with the prior art, there has been a problem that, for example, a ceramic sintered body with insufficient strength is produced due to variations in individual differences that occur during the production of the ceramic sintered body. As described above, there is still room for improvement with respect to the technology for improving the strength of the ceramic sintered body used for the cutting tool.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a technique for improving the strength of a ceramic sintered body used for a cutting tool.

  In order to solve at least a part of the above problems, the present invention can be realized as the following aspects or application examples.

[Application Example 1]
A method for producing a ceramic sintered body used for a cutting tool,
A preparation step of preparing a slurry containing raw material powder and a binder having a carbon component;
A molding step of forming a dried product of the slurry to obtain a molded body;
A degreasing step of obtaining a degreased body by heating so that carbon remains in the molded body;
An inspection process for inspecting the surface of the degreased body;
And a firing step of firing the degreased body after the inspection.

  According to this configuration, since the degreased body to be inspected in the inspection process is darkened by the carbon component, it is possible to easily identify the degreased body whose strength is not sufficient after firing due to defects such as cracks and pores. . By specifying a degreased body that does not have sufficient strength after firing before firing, the strength of the ceramic sintered body obtained after firing can be improved.

[Application Example 2]
In the manufacturing method described in Application Example 1,
The inspection step includes a step of sorting the degreased body into either an acceptable product or a rejected product according to the degree of defects on the surface of the degreased body,
The said baking process includes the process of baking the degreased body made into the pass product in the said test | inspection process.

  According to this configuration, since the degreased body that has been accepted in the inspection process is fired, the strength of the ceramic sintered body obtained after firing can be improved.

[Application Example 3]
In the manufacturing method described in Application Example 1 or Application Example 2,
The said degreasing process includes the process of heating so that the carbon which remains in the said molded object may be 0.01 to 0.3 weight%, The manufacturing method characterized by the above-mentioned.

  According to this configuration, the degreased body to be inspected in the inspection process is blackened by containing 0.01 wt% to 0.3 wt% of carbon, and therefore, a degreased body that does not have sufficient strength after firing can be easily obtained. Can be specified.

[Application Example 4]
In the manufacturing method according to any one of Application Example 1 to Application Example 3,
The preparation step includes a step of preparing a slurry containing any one of alumina, zirconia, and silicon nitride as a raw material powder.

  According to this configuration, the strength of the ceramic sintered body containing any one of alumina, zirconia, and silicon nitride can be improved.

[Application Example 5]
In the manufacturing method according to any one of Application Example 1 to Application Example 4,
The preparation method includes a step of preparing a binder containing any of paraffin, polyvinyl alcohol, acrylic resin, polycarboxylic acid, fatty acid, stearic acid, and polyethylene oxide.

  According to this structure, since carbon is contained in the binder, a blackened degreased body can be easily obtained in the degreasing step.

  In addition, this invention can be implement | achieved in various aspects, for example, the manufacturing method of the cutting insert comprised by the ceramic sintered compact, the manufacturing method of the cutting tool provided with a cutting insert, and inspection of a ceramic sintered compact It can be realized in the form of a method or the like. Moreover, the sialon sintered body according to the present invention can be applied in combination with other members as appropriate.

It is explanatory drawing for demonstrating schematic structure of the cutting insert which concerns on one Embodiment of this invention. It is a flowchart for demonstrating the flow of the manufacturing method of a ceramic sintered compact. It is explanatory drawing which compared the conspicuousness of the defect of the surface of the degreased body which changed to the blackish color, and the white degreased body.

<Embodiment>
Drawing 1 (A) is an explanatory view for explaining a schematic structure of a cutting insert concerning one embodiment of the present invention. Drawing 1 (B) is an explanatory view for explaining a schematic structure of a cutting tool provided with a cutting insert. The cutting insert 1 is a substantially cylindrical cutting edge, and is attached to the cutting tool 10 for use. The cutting tool 10 is a tool used for heat-resistant alloy cutting and the like, and includes a mounting portion 12 called a holder at the distal end portion of the main body portion 11. The cutting insert 1 is detachably attached to the attachment portion 12.

  The cutting insert 1 of this embodiment is comprised by the ceramic sintered compact demonstrated below. The cutting tool refers to all tools that perform turning, milling, grooving, finishing, and the like. The cutting insert is a cutting edge that is detachably attached to the distal end portion of the cutting tool body, and is also called a throw-away tip, a cutting edge replacement tip, or the like.

The ceramic sintered body of the present embodiment is an alumina / zirconia ceramic mainly composed of alumina (Al ₂ O ₃ ) and zirconia (ZrO ₂ ). The ceramic sintered body of the present embodiment is not limited to alumina / zirconia ceramics. For example, alumina ceramics, zirconia ceramics, silicon nitride ceramics, alumina, zirconia, and silicon nitride can be used. The composite ceramic etc. which compounded 2 or more types may be sufficient.

  FIG. 2 is a flowchart for explaining the flow of the method of manufacturing the ceramic sintered body. Below, an example of the manufacturing method of an alumina zirconia ceramic is demonstrated. Various numerical values used in the following explanation (for example, the average particle diameter of powder, mixing time, press pressure, heating time, heating temperature, etc.) are just examples, and values other than these are arbitrarily adopted. Is possible.

In manufacturing the ceramic sintered body of the present embodiment, first, a slurry containing raw material powder of the sintered body is prepared (step S11). As an example of a method for preparing the slurry, a raw material powder containing alumina (Al ₂ O ₃ ) powder, zirconia (ZrO ₂ ) powder, and rare earth oxide (Y ₂ O ₃ ) is prepared. Can be obtained by mixing with ethanol in a ball mill for about 24 hours. There is no particular limitation on the average particle size of each raw material powder contained in the slurry, but examples include about 0.5 μm to 1.0 μm. The amount of zirconia (ZrO ₂₎ contained in the raw material powder can be exemplified about 3 wt% to 40 wt%. You may adjust pH in order to control the dispersion | distribution and aggregation state of the grinding | pulverization particle | grains contained in a slurry.

  A binder is added to the prepared slurry (step S12). The binder added to the slurry is not particularly limited as long as it contains carbon as a component. Examples of the binder containing carbon include emulsions and aqueous solutions containing paraffin, polyvinyl alcohol (PVA), acrylic resin, polycarboxylic acid, fatty acid, stearic acid, polyethylene oxide (PEO), and the like. More specifically, a paraffin wax emulsion, a stearic acid wax emulsion, and a polyethylene oxide aqueous solution can be exemplified. Although the amount of the binder added is not particularly limited, examples of the ratio of the binder in the slurry include about 0.5 wt% to 15 wt%. More specifically, for example, the paraffin wax emulsion can be about 8.5% by weight, the stearic acid wax emulsion can be about 2.5% by weight, and the aqueous polyethylene oxide solution can be about 4.0% by weight. After adding a binder to a slurry, the slurry to which the binder was added can be obtained by stirring.

The slurry to which the binder has been added is dried with a spray dryer to produce granules (step S13). Thereby, granules (spray granules) containing the raw material powder and the binder can be obtained. The obtained granule is press-molded into the shape of a cutting insert (step S14). Although there is no limitation in particular also about a press pressure, about 2000 kgf / cm < ² > can be illustrated. By this press molding, a ceramic molded body (also simply referred to as a “formed body”) molded into the shape of the cutting insert can be obtained.

  The obtained molded body is degreased (step S15). In general, degreasing of a molded product refers to removing the binder component from the molded product by heating or the like. The degreasing in this step is not to completely remove the binder component from the molded body but to heat so that carbon of the binder decomposition product remains in the molded body after degreasing (hereinafter also referred to as “degreasing body”). It is a feature. Such degreasing by heating is also referred to as “temporary sintering”. By leaving carbon in the degreased body, the degreased body can be changed to a blackish color (including black). In addition, although there is no limitation in particular about the ratio of carbon contained in a defatted body, it is preferable to set it as about 0.01 weight%-0.3 weight%. The reason why the surface of the degreased body is changed to a blackish color is to facilitate the discovery of defects on the surface of the degreased body in the visual inspection in step S16 described later. For this reason, if the proportion of carbon contained in the degreased body is less than 0.01% by weight, the blackness of the degreased body is weakened, and the effect of facilitating defect detection may be reduced. On the other hand, if the carbon content is more than 0.3% by weight, the blackness becomes too strong, and the effect of facilitating defect detection may be reduced. The degreasing in this step is not particularly limited with respect to the heating temperature, the heating time, and the like. For example, a degreased body (temporarily sintered body) with a blackish color can be obtained by heating at 800 ° C. for 30 minutes in an atmosphere of an inert gas (for example, nitrogen) of 30 kPa.

  Next, the obtained degreased body is visually inspected (step S16). The visual inspection is a step of visually confirming whether or not defects such as cracks and pores are generated on the surface of the degreased body. Since the surface of the degreased body to be inspected is blackened through the degreasing of step S15, the surface cracks are compared with the case of visually inspecting the sintered body that has become white through the firing step of step S17 described later. And it is easy to find pores. Further, the degreased body may have blacker cracks and pores than the periphery due to carbon soot entering the cracks and pores. Therefore, cracks and pores are easily noticeable and can be easily found. In the present embodiment, after the visual inspection, the degreased body is sorted into an acceptable product and an unacceptable product depending on the presence or absence of defects, and only the acceptable product is advanced to the next firing step. The selection criteria for the acceptable product and the rejected product can be arbitrarily set. For example, a degreased body having a defect may be selected as a pass product or a reject product depending on whether the degree of the defect exceeds a predetermined standard.

  Subsequently, the degreased body of the accepted product is fired (step S17). By this firing, carbon in the degreased body is removed from the degreased body, and a sintered body having a whitish color (including white) substantially free of carbon can be obtained. The firing in this step is not particularly limited with respect to the firing temperature, firing time, and the like. For example, a sintered body can be obtained by firing at 1800 ° C. for 2 hours in an inert gas (for example, argon) atmosphere of 65 kPa.

  Subsequently, the sintered body obtained through the firing process is polished (step S18). By performing polishing using a diamond grindstone or the like and adjusting the shape of the cutting insert, a cutting insert composed of a sintered body can be obtained.

  According to the method for manufacturing a ceramic sintered body of the present embodiment described above, in the degreasing step (step S15), the degreased body is changed to a blackish color. Defects such as cracks and pores can be easily found. Thereby, since the degreased body whose strength is not sufficient after firing can be selected, only a sintered body having high strength after firing can be obtained. When a high-strength sintered body is used as a cutting tool, there are almost no surface defects, and a long life can be stably exhibited.

  FIG. 3 is an explanatory diagram comparing the conspicuousness of defects on the surface of a degreased body that has changed to a blackish color and a white degreased body. The degreased body shown on the left side of each of FIGS. 3A to 3C is obtained by the manufacturing method of the present embodiment, and the surface is changed to a blackish color. On the other hand, the degreased body shown on the right side of each figure is one in which the binder component is substantially removed in the degreasing step, and the surface is white. In each of FIGS. 3A to 3C, the degreased body shown on the left side and the degreased body shown on the right side are taken under the same conditions (presence / absence of flash, photographing angle, etc.). Note that FIG. 3B and FIG. 3C differ in the presence or absence of a flash at the time of shooting, FIG. 3B uses a flash, and FIG. 3C does not use a flash. Is. Moreover, in each figure of Fig.3 (a)-(c), the defect (crack etc.) part on the surface of a degreased body is circled and shown. 3 (a) to 3 (c), it can be seen that the surface of the degreased body that has changed to a blackish color is more conspicuous than the white degreased body, and it is easier to find the defects visually.

  Moreover, according to the manufacturing method of this embodiment, since there exists an inspection process (step S16) before a baking process (step S17), the baking of the degreased body whose intensity | strength is not enough after baking can be stopped, and manufacture Cost can be reduced.

  Conventionally, the inspection process has been performed after the firing process. Therefore, the object to be inspected was a white sintered body, and it was not easy to find surface defects. If it is considered to color the sintered body to be inspected, there is a problem that a separate coloring process is required for coloring, resulting in an increase in man-hours and an increase in material costs. On the other hand, according to the manufacturing method of the present embodiment, the degreased body to be inspected can be colored with the carbon component contained in the binder, and then the carbon can be removed by firing. Inspection accuracy can be improved without increasing the cost.

  Conventionally, for the purpose of improving the strength and toughness of ceramic sintered bodies, the raw powder is pulverized to improve the sinterability, or the sintered body is impregnated with a metal salt solution and homogeneous without coarse particles. Improvements have been made by various methods, such as making a sintered body or combining different materials. The present invention differs from these in that it aims to obtain a high-strength ceramic sintered body by increasing the accuracy of removing rejected products that are defective during manufacturing.

<Modification>
In addition, this invention is not restricted to said embodiment, In the range which does not deviate from the summary, it can be implemented in a various aspect, For example, the following deformation | transformation is also possible.

(1) Modification 1:
In the said embodiment, it demonstrated as a manufacturing method of the cutting insert. However, the manufacturing method according to the present invention is not limited to the cutting insert, and can be applied as a method for manufacturing other tools and product members.

(2) Modification 2:
In the said embodiment, it demonstrated as a manufacturing method of an alumina zirconia-type ceramic. However, the manufacturing method according to the present invention is not limited to alumina-based ceramics, zirconia-based ceramics, and silicon nitride-based ceramics, but also as a method for manufacturing composite ceramics that are a composite of alumina, zirconia, and silicon nitride. Can be applied. That is, it can be applied as a method for producing various types of ceramics by changing the content of the raw material powder to be prepared. For example, if it is applied as a method for producing a silicon nitride ceramic, a raw material powder containing silicon nitride (Si ₃ N ₄ ) powder may be prepared. In addition, when applied as a method for producing an alumina-based ceramic, a raw material powder containing alumina (Al ₂ O ₃ ) powder may be prepared. If it is applied as a method for producing a zirconia-based ceramic, a raw material powder containing zirconia (ZrO ₂ ) powder may be prepared.

DESCRIPTION OF SYMBOLS 1 ... Cutting insert 10 ... Cutting tool 11 ... Main-body part 12 ... Mounting part

Claims (5)

A method for producing a ceramic sintered body used for a cutting tool,
A preparation step of preparing a slurry containing raw material powder and a binder having a carbon component;
A molding step of forming a dried product of the slurry to obtain a molded body;
A degreasing step of obtaining a degreased body by heating so that carbon remains in the molded body;
An inspection process for inspecting the surface of the degreased body;
And a firing step of firing the degreased body after the inspection. The manufacturing method according to claim 1,
The inspection step includes a step of sorting the degreased body into either an acceptable product or a rejected product according to the degree of defects on the surface of the degreased body,
The said baking process includes the process of baking the degreased body made into the pass product in the said test | inspection process. In the manufacturing method of Claim 1 or Claim 2,
The said degreasing process includes the process of heating so that the carbon which remains in the said molded object may be 0.01 to 0.3 weight%, The manufacturing method characterized by the above-mentioned. In the manufacturing method in any one of Claims 1 thru | or 3,
The preparation step includes a step of preparing a slurry containing any one of alumina, zirconia, and silicon nitride as a raw material powder. In the manufacturing method in any one of Claims 1 thru | or 4,
The preparation method includes a step of preparing a binder containing any of paraffin, polyvinyl alcohol, acrylic resin, polycarboxylic acid, fatty acid, stearic acid, and polyethylene oxide.