JP5821088B2 - Cubic boron nitride sintered body tool and manufacturing method thereof - Google Patents

Description

  The present invention relates to a cBN sintered body tool in which a cBN sintered body containing cubic boron nitride (hereinafter also referred to as cBN) particles and a binder phase is directly bonded onto a tool base material via a bonding layer. .

  Conventionally, a sintered body with high hardness using cBN is known. For example, Patent Document 1 discloses a cBN sintered body containing 20 to 80% by volume of cBN and having a Ti ceramic-based binder phase as the balance. However, when this cBN sintered body is used for high-efficiency cutting such as intermittent cutting, heavy cutting and high-speed cutting, the bonding strength between the cBN sintered body and the tool base material is weak, and the cBN sintered body is detached during cutting. There was a problem. For this reason, not only the economic demerit due to the short tool life is pointed out, but also the workpiece may be damaged greatly.

  Thus, efforts have been made to increase the bonding strength between the cBN sintered body and the tool base material. For example, Japanese Patent Application Laid-Open No. 02-274405 (Patent Document 2), Japanese Patent Application Laid-Open No. 07-124804 (Patent Document 3), Japanese Patent Application Laid-Open No. 09-108912 (Patent Document 4), Japanese Patent Application Laid-Open No. 11-188510 (Patent Document). Reference 5) describes a bonding layer (also referred to as a brazing material) for bonding a cBN sintered body to a tool base material by selecting a bonding layer composition having high bonding strength and an active metal layer at the interface between the bonding layer and the sintered body. It has been proposed to increase the bonding strength by forming a film. However, in recent years, there has been a demand for higher efficiency, higher speed machining, and higher load machining in addition to the difficulty of cutting work materials. Such proposals are not sufficiently reliable. There is a need for improvements.

  On the other hand, regarding techniques for joining different materials, for example, International Publication No. 2007/076023 (Patent Document 6), Japanese Patent Application Laid-Open No. 2009-208374 (Patent Document 7), Japanese Patent Application Laid-Open No. 08-336716 (Patent Document 8), Japanese Patent Application Laid-Open No. 2009-226643 (Patent Document 9), Japanese Patent Application Laid-Open No. 59-146986 (Patent Document 10), Japanese Patent Application Laid-Open No. 08-319174 (Patent Document 11), and the like are known. It has been proposed to provide an uneven shape by irradiating and to increase the bonding strength by its anchor effect. In particular, Patent Document 10 proposes to increase the bonding strength by forming a 1 mm deep hole in the bonding surface with a laser, and Patent Document 11 discloses the correlation between the surface roughness of the bonding surface and the bonding strength. It is shown that the stronger the surface roughness, the higher the bonding strength.

JP-A-53-077781 Japanese Patent Laid-Open No. 02-274405 Japanese Patent Laid-Open No. 07-124804 JP 09-108912 A Japanese Patent Laid-Open No. 11-188510 International Publication No. 2007/076023 JP 2009-208374 A JP 08-336716 A JP 2009-226443 A JP 59-146986 A Japanese Patent Laid-Open No. 08-319174

  The present invention has been made in view of the current situation as described above, and its object is to sinter cubic boron nitride even under severe use conditions such as high efficiency, high speed processing, and high load processing. It is an object of the present invention to provide a cubic boron nitride sintered body tool having an excellent bonding strength so that the body does not detach from the tool base material.

  The present inventor considers that it is important to increase the bonding strength between the cBN sintered body and the bonding layer in order to reduce the separation of the cBN sintered body from the tool base material. We continued research to increase the bonding strength between the two by changing the surface condition by laser irradiation. As a result, it has been found that the bonding strength varies greatly depending on the size, spacing, shape, and surface cleaning state of the irregularities on the bonding surface between the cBN sintered body and the bonding layer. Furthermore, we obtained completely new knowledge contrary to the conventional knowledge that the joint strength decreases when the unevenness becomes too large, and we continued further research based on this knowledge. The present inventors have found that the separation of the cBN sintered body from the tool base material during use can be greatly reduced, and the present invention has been completed.

  That is, the cubic boron nitride sintered body tool of the present invention is a cubic boron nitride sintered body joined to a tool base material via a joining layer, and the cubic boron nitride sintered body and joining layer When the cubic boron nitride sintered body tool is cut along a plane perpendicular to the bonding surface having the largest area among the bonded surfaces, the cubic boron nitride sintered body has irregularities on its surface. The surface of the concavo-convex shape is divided into two equal parts, and a straight line parallel to the joint surface between the joining layer and the tool base material is a reference line, and the distance between the reference line and the maximum value of the concavo-convex shape is When the sum of the maximum value and the maximum value of the distance between the reference line and the minimum value of the concavo-convex shape is a and the maximum value of the distance in the reference line direction between adjacent maximum values in the concavo-convex shape is b, a is 0.02 mm or more and 0.2 mm or less, and b is 0.02 mm or more and 1 mm or less. To.

  Among the maximum values of the concavo-convex shape, the point having the maximum distance from the reference line is taken as the maximum point, passes through a point perpendicular to the reference line from the maximum point by 0.02 mm, and is parallel to the reference line When the straight line is a cut line, the ratio C / L of the sum length C of the portion where the cut line passes through the bonding layer to the length L of the cut line is 0.1 or more and 0.6 or less. The ratio b / a of b to a is preferably 1 or more.

  The cubic boron nitride sintered body includes cubic boron nitride particles and a binder phase. When the average particle diameter of the cubic boron nitride particles is x, the ratio a / x to x is 1 or more. Preferably there is.

  The cubic boron nitride sintered body preferably contains 75% by volume or more of cubic boron nitride particles. The bonding layer preferably contains Ti, Zr, and Cu. The tool base material is preferably made of cemented carbide, cermet, or ceramics.

  The present invention is also a method for manufacturing the above-described cubic boron nitride sintered body tool, and a laser processing apparatus using a water column as an optical path with respect to a joint surface having the largest area among the surfaces of the cubic boron nitride sintered body. A laser nozzle comprising: forming a concavo-convex shape on the joining surface by irradiating a laser beam; and joining a cubic boron nitride sintered body to a tool base material via a joining layer. The diameter is 30 to 100 μm, the wavelength of the laser beam is 500 to 1100 nm, the pulse width of the laser beam is 10 to 300 ns, the output of the laser beam is 1 to 100 W, and the repetition of the laser beam The frequency is 1 to 100 kHz, and the processing speed of the laser beam is 100 to 3000 mm / s.

  It is preferable to include a step of lapping the bonding surface irradiated with the laser beam with a diamond abrasive brush.

  The present invention is also a method for manufacturing the above-described cubic boron nitride sintered body tool, using a dry laser processing apparatus on the joining surface having the largest area among the surfaces of the cubic boron nitride sintered body. Forming a concavo-convex shape on the joint surface by irradiating light; wrapping the joint surface irradiated with the laser light with a diamond abrasive brush; and a cubic boron nitride sintered body Bonding to a tool base material through a bonding layer.

  The cubic boron nitride sintered body tool of the present invention has the above-described configuration, so that the cubic boron nitride sintered body can be used even under severe usage conditions such as high efficiency, high speed machining, and high load machining. It has excellent bonding strength that does not detach from the material.

(A) is typical sectional drawing of the cubic boron nitride sintered compact tool of this invention, (b) is typical sectional which expanded the interface of a cubic boron nitride sintered compact and a joining layer. FIG. FIG. 4 is a schematic cross-sectional view in which an interface between a cubic boron nitride sintered body and a bonding layer is enlarged.

Hereinafter, the cubic boron nitride sintered body tool of the present invention will be further described.
<Cubic boron nitride sintered body tool>
Fig.1 (a) is typical sectional drawing of the cubic boron nitride sintered compact tool of this invention. A cubic boron nitride sintered body tool 1 of the present invention is a cubic boron nitride sintered body 2 bonded to a tool base material 4 via a bonding layer 3 as shown in FIG. The surface of the cubic boron nitride sintered body 2 has an uneven shape as shown in FIG. 1B.

  That is, an arbitrary cut surface when the cubic boron nitride sintered body tool 1 is cut along a plane perpendicular to the bonding surface having the largest area among the bonding surfaces of the cubic boron nitride sintered body 2 and the bonding layer 3. The cubic boron nitride sintered body 2 has a concavo-convex shape on the surface thereof, and the area of the concavo-convex shape is divided into two equal parts, and parallel to the joining surface between the joining layer 3 and the tool base material 4. Using a straight line as a reference line, a is the sum of the maximum distance between the reference line and the maximum value of the uneven shape and the maximum value of the distance between the reference line and the minimum value of the uneven shape, When the maximum value of the distance in the reference line direction between the maximum values is b, a is 0.02 mm to 0.2 mm, and b is 0.02 mm to 1 mm.

  Here, “the bonding surface having the largest area among the bonding surfaces of the cubic boron nitride sintered body and the bonding layer” refers to the cubic boron nitride sintered body 2 in the cubic boron nitride sintered body tool 1. In general, there are a plurality of bonding surfaces between the bonding layer 3 and the bonding layer 3, but the bonding surface has the largest area. For example, the cubic boron nitride sintered body tool 1 has a quadrangular prism shape whose bottom surface is rhombus, and the cubic boron nitride sintered body 2 is joined to the tool base material 4 at the corner portion of the square column. For example, a cubic boron nitride sintered body usually has a triangular prism shape whose bottom surface is an isosceles triangle, and the tool mother is formed by two surfaces of one of the three side surfaces and the bottom surface. The joining surface that is joined to the material 4 and has a larger area among the side surface and the bottom surface corresponds to the joining surface having the maximum area. This is because when the tool base material 4 and the cubic boron nitride sintered body 2 are joined, the joining layer 3 always exists on the joining surface.

  In addition, “dividing the area of the concavo-convex shape vertically into two” means that the area of the portion existing above the reference line when the concavo-convex shape is divided vertically by the reference line in the cut surface. The sum is equal to the sum of the areas of the portions existing below the reference line. Such a reference line can be obtained by analyzing a micrograph of the cut surface with an image analysis using a computer.

  In addition, “a straight line parallel to the joining surface between the joining layer and the tool base material” means that the joining surface between the joining layer and the tool base material is a plane (that is, this is regarded as a straight line in the cut surface). A straight line parallel to a straight line.

  In addition, the “maximum value of the concavo-convex shape” and the “minimum value of the concavo-convex shape” are a wavy line composed of “mountains” and “valleys” when the concavo-convex shape on the cut surface is viewed from the cubic boron nitride sintered body side. Assuming that the top of the “mountain” is the “maximum value”, the bottom of the “valley” is the “minimum value”. The “distance from the local maximum” indicates the shortest distance between the local maximum and the reference line, and the “distance from the local minimum” similarly indicates the shortest distance between the local minimum and the reference line. Since there are a plurality of “mountains” and “valleys”, the one with the maximum distance is selected as the “maximum value”. In FIG. 1, since the upper side is a cubic boron nitride sintered body, it seems that the maximum value, maximum value, minimum value, and the like are upside down in form.

  The “distance in the reference line direction between adjacent maximum values” is a distance obtained by directly connecting adjacent maximum values with a straight line in the “maximum value” defined above (ie, the shortest distance between both points). Instead, the intersection of the perpendicular line passing through each local maximum value and the reference line with respect to the reference line is taken, and the distance between these intersection points is meant.

  In the present invention, the sum of the maximum value of the distance between the reference line and the maximum value of the uneven shape and the maximum value of the distance between the reference line and the minimum value of the uneven shape is a, If the maximum value of the distance in the reference line direction between the local maximum values is b, a is 0.02 mm or more and 0.2 mm or less, and b is 0.02 mm or more and 1 mm or less. Found that the bonding strength between the cubic boron nitride sintered body and the bonding layer was dramatically increased, and the bonding strength between the cubic boron nitride sintered body and the tool base material was dramatically increased. It is. Although this detailed mechanism has not yet been fully elucidated, it is thought that it is probably due to a synergistic effect of the adhesion area expansion effect and the anchor effect by increasing the surface area of the bonding interface. In addition, it is assumed that the thermal stress is made uniform by controlling the uneven state as described above.

  Since the surface shape of the cubic boron nitride sintered body defined in the present invention focuses on the maximum value of the surface roughness in a certain section and the distance in the reference line direction between adjacent maximum values, it is conventionally known. Such as Rz, Ra, Sm, etc., which are technically irrelevant to those that focus only on the maximum and average values of the surface roughness in a certain section, such as Rz, Ra, Sm. It is impossible to define the surface shape of the cubic boron nitride sintered body of the present invention by such parameters. That is, according to the present invention, it is impossible to define the surface shape of the cubic boron nitride sintered body for significantly increasing the bonding strength between the cubic boron nitride sintered body and the bonding layer by a conventionally known parameter. Therefore, the surface shape of the cubic boron nitride sintered body that can remarkably improve the adhesion with the bonding layer is defined by a new parameter that replaces the conventionally known parameter.

  The a is more preferably 0.05 mm or more and 0.15 mm or less, the b is more preferably 0.05 mm or more and 0.5 mm or less, and the ratio b / a is preferably 1 or more. More preferably, it is 1.5 or more and 5 or less. If a is less than 0.02 mm, the anchor effect due to the concavo-convex shape and the effect of improving the bonding force due to the increase in the bonding area cannot be obtained, and if it exceeds 0.2 mm, the bonding layer becomes relatively thick, There is a problem that the frequency with which gaps are generated in the bonding layer increases and the bonding layer is easily broken. If b is less than 0.02 mm, the brazing material is unlikely to enter the valleys of the cubic boron nitride sintered body, and gaps are likely to occur in the bonding layer, resulting in variations in bonding strength. On the other hand, if b exceeds 1 mm, there is a problem in that it is impossible to improve the bonding strength due to the anchor effect. If b / a is less than 1, the brazing material is less likely to enter the valleys of the cubic boron nitride sintered body and gaps are likely to occur in the bonding layer. Since the unevenness of the body has a relatively pointed shape, stress concentrates on the pointed shape portion, and defects are likely to occur during cutting.

  Further, as shown in FIG. 2, the present invention sets the maximum point of the concavo-convex shape as a maximum point that is the distance to the reference line, and sets the maximum point to 0 in the vertical direction from the maximum point to the reference line. When a straight line passing through a point 0.02 mm apart and parallel to the reference line is a cut line, the ratio of the length C of the sum of the part where the cut line passes through the bonding layer to the length L of the cut line C / L is preferably 0.1 or more and 0.6 or less. This can relieve stress concentration at the bonding interface between the cubic boron nitride sintered body and the bonding layer, and can reduce non-uniform bonding strength at the bonding interface, greatly extending tool life. Can do. The ratio C / L is more preferably 0.3 or more and 0.5 or less. If C / L is less than 0.1, only the peak having the maximum point protrudes and is high, and the other peaks do not have an appropriate height, so stress is concentrated on the peak having the maximum point. In addition, since the peak having the maximum point has a pointed shape, cracks are likely to occur in the cubic boron nitride sintered body due to stress concentration, and the uniformity of strength at the joint interface is impaired. On the other hand, if it exceeds 0.6, it does not protrude and does not have a high peak, and there is a possibility that the effect of improving the bonding strength by the anchor effect cannot be obtained sufficiently.

  The cubic boron nitride sintered body tool of the present invention having the above-mentioned characteristics can be used particularly effectively in high-efficiency roughing of high-hardness quenched steel, sintered alloy and difficult-to-cut cast iron, and in addition to these It can also be suitably used in various general metal processing.

  When the cubic boron nitride sintered body tool of the present invention is used for cutting applications, for example, drills, end mills, milling or turning edge cutting type cutting tips, metal saws, gear cutting tools, reamers, taps, or cranks. It can be used very effectively as a pin for pin milling processing of a shaft.

  In FIG. 1 (a), the cubic boron nitride sintered body 2 is joined to one portion of the cutting edge of the cubic boron nitride sintered body tool 1, but the cubic nitride of the present invention is illustrated. The boron sintered body tool is not limited to such an embodiment. For example, when there are a plurality of cutting edges, a cubic boron nitride sintered body may be bonded to each cutting edge, or a cubic boron nitride sintered body may be bonded to a portion that does not constitute the cutting edge. Good. In addition, the joining interface between the cubic boron nitride sintered body and the tool base material is joined on only one side, such as joining a flat plate-shaped cubic boron nitride sintered body on one side or both sides of the tool base material. Also good.

<Cubic boron nitride sintered body>
The cubic boron nitride sintered body of the present invention includes cubic boron nitride particles and a binder phase. As long as these two components are included, unavoidable impurities and other components may be included.

  When the average particle diameter of the cubic boron nitride particles is x, the ratio a / x of a to x is preferably 1 or more. As a result, theoretically, one or more cubic boron nitride sintered body particles are present in the convex portion (the portion where the cubic boron nitride sintered body projects to the bonding layer side) in the concave and convex shapes. Therefore, there is always an interface between the cubic boron nitride sintered particles and the binder phase. As a result, the interface portion acts as a stress buffer region, which is considered to contribute to further improvement in the bonding strength of the cubic boron nitride sintered body to the tool base material. The ratio a / x is more preferably 10 or more and 60 or less.

  The cubic boron nitride sintered body of the present invention preferably contains 75% by volume or more of cubic boron nitride particles. Thereby, the joint strength to the tool base material of a cubic boron nitride sintered compact can further be improved. This is because, as described above, the concave / convex shape of the bonding interface between the cubic boron nitride sintered body and the bonding layer is defined as described above. It is considered that the bonding strength with the bonding layer was improved, and a synergistic effect between the characteristics such as the high hardness inherent in the cubic boron nitride sintered particles and the improved bonding strength was developed. The content of the cubic boron nitride sintered particles is more preferably 85% by volume to 98% by volume. If the cubic boron nitride particles are less than 75% by volume, the high hardness characteristics of the cubic boron nitride sintered body cannot be obtained sufficiently, which is not preferable.

  The shape and size of such a cubic boron nitride sintered body is not particularly limited, and a conventionally known shape and size can be employed without particular limitation.

<Binder phase>
In the present invention, the binder phase contained in the cubic boron nitride sintered body has an action of binding cubic boron nitride particles to each other, and is 25% by mass or less in the cubic boron nitride sintered body, preferably It is preferable that it is contained in an amount of 2 to 15% by mass.

  Such a binder phase is selected from the group consisting of at least one element selected from the group consisting of group IVa elements, group Va elements, and group VIa elements of the periodic table, and nitrogen, carbon, boron, and oxygen. A compound comprising at least one element, or a solid solution of the compound, and a carbide, boride, carbonitride, or oxidation of at least one element selected from the group consisting of W, Co, Al, Zr, and Cr And at least one selected from these solid solutions.

<Junction layer>
The bonding layer 3 of the present invention plays a role for bonding the cubic boron nitride sintered body 2 and the tool base material 4 and is sometimes called a brazing material. Although such a joining layer can employ | adopt without specifically limiting the thing of a conventionally well-known composition, it is preferable that Ti, Zr, and Cu are included. This is because the inclusion of Ti, Zr, and Cu is excellent in high-temperature strength, so that it is difficult to soften even when exposed to high temperatures by high-efficiency cutting or the like, and damage to the bonding layer itself can be prevented.

  Such a bonding layer 3 contains 5% by mass or more of Ti and 5% by mass or more of Zr with respect to the whole, and the total of Ti and Zr is 90% by mass or less, and the balance is Cu. It is preferable to contain. Since Cu has the effect of lowering the melting point of the material constituting the bonding layer mainly composed of Ti and Zr, bonding processing at a low temperature is possible. Also, since Cu has a high elastic modulus, when Cu is contained, when the processing heat generated during processing flows into the tool base material 4 through the cubic boron nitride sintered body 2, the cubic boron nitride sintered body 2 and the tool base material 4 have an effect of absorbing distortion due to a difference in thermal expansion. When Cu is less than 10% by mass, those effects cannot be obtained, and when it exceeds 90% by mass, the contents of Ti and Zr are relatively lowered, and the bonding strength is lowered.

  In addition to Cu having a high high-temperature strength, Ti and Zr described above significantly improve the wettability of the material constituting the bonding layer, and the cubic boron nitride sintered body 2 and the bonding layer 3 There is an effect of increasing the bonding strength. When Ti or Zr is less than 5% by mass, the effect of improving the strength at high temperatures and the bonding strength cannot be obtained. Conversely, when the total of both Ti and Zr exceeds 90% by mass, the melting point increases. This is not preferable because it induces distortion and cracking during bonding. A preferable range of the total content of Ti and Zr is 10% by mass or more and 90% by mass or less, and the combined strength is particularly preferable when used in combination with the preferable range of the Cu content.

  In particular, if the content of Ti contained in the bonding layer 3 is 20% by mass or more and 30% by mass or less and the content of Zr is 20% by mass or more and 30% by mass or less, 3 of Ti, Zr and Cu. A melting point drop due to the original eutectic appears remarkably, and bonding at a lower melting point becomes possible, which is preferable.

  Such a bonding layer exists at the bonding interface between the cubic boron nitride sintered body and the tool base material, and the cubic boron nitride sintered body and the tool base material are bonded via this bonding layer. The In this case, the thickness of the bonding layer is not particularly limited, but can usually be 10 μm or more and 200 μm or less.

<Tool base material>
In the present invention, the tool base material to which the cubic boron nitride sintered body is joined may be any conventionally known material known as this type of tool base material, and in particular, It is not limited. For example, those made of cemented carbide, cermet, or ceramics can be suitably used.

<Method for Manufacturing Cubic Boron Nitride Sintered Tool>
The manufacturing method of the cubic boron nitride sintered compact tool of this invention can include the following processes. That is, the manufacturing method irradiates a laser beam using a laser processing apparatus having a water column as an optical path to the bonding surface having the largest area among the surfaces of the cubic boron nitride sintered body. Forming a concavo-convex shape on the surface, and joining a cubic boron nitride sintered body to a tool base material via a joining layer, wherein the laser nozzle diameter is 30 to 100 μm, and the laser beam The wavelength of the laser beam is 500 to 1100 nm, the pulse width of the laser beam is 10 to 300 ns, the output of the laser beam is 1 to 100 W, and the repetition frequency of the laser beam is 1 to 100 kHz The processing speed of the laser beam is preferably 100 to 3000 mm / s.

  Moreover, it is preferable that said manufacturing method further includes the step of lapping with a diamond abrasive brush with respect to the joint surface irradiated with the laser beam.

  Further, another manufacturing method of the cubic boron nitride sintered body tool according to the present invention uses a dry laser processing apparatus on a bonding surface having the largest area among the surfaces of the cubic boron nitride sintered body, and uses a laser. Forming a concavo-convex shape on the joint surface by irradiating light; wrapping the joint surface irradiated with the laser light with a diamond abrasive brush; and a cubic boron nitride sintered body Bonding to the tool base via a bonding layer.

  The manufacturing method of the cubic boron nitride sintered body tool of the present invention can include other arbitrary steps as long as the above steps are included. Examples of such other optional steps include a step of preparing a cubic boron nitride sintered body. This will be further described below.

<Step of preparing a cubic boron nitride sintered body>
The cubic boron nitride sintered body used in the present invention can be prepared by manufacturing as follows. First, the cubic boron nitride particles and the raw material powder constituting the binder phase are introduced into an ultrahigh pressure apparatus, and these powders are subjected to ultrahigh pressure sintering to produce a bulk sintered body. Here, the pressure during the ultrahigh pressure sintering is preferably 3 GPa or more and 7 GPa or less. Further, the temperature at the time of ultra-high temperature sintering is preferably 1100 ° C. or more and 1900 ° C. or less, and the treatment time for ultra-high temperature sintering is preferably 10 minutes or more and 180 minutes or less.

  Next, after setting the bulk sintered body obtained above in an electric discharge machine, it is cut into a desired shape using a brass wire to obtain a cubic boron nitride sintered body. The cutting using a brass wire is preferably performed in water from the viewpoint of production efficiency. The bulk sintered body may be cut using a laser cutting machine. Since it can cut | disconnect highly efficiently by cut | disconnecting using a laser cutter, it is more preferable.

  The cubic boron nitride sintered body formed by cutting the bulk sintered body is not particularly limited as long as it has a shape that can be used by being bonded to a tool base material. For example, a rectangular parallelepiped, a triangular prism, a triangle A shape such as a cone, a prism, or a column can be used. And the cubic boron nitride sintered compact can be obtained by grind | polishing the surface of the surface cut with said brass wire.

<Step of forming an uneven shape on the joint surface>
This step is performed by irradiating a laser beam using a laser processing apparatus having a water column as an optical path, with respect to the joint surface having the largest area among the surfaces of the cubic boron nitride sintered body prepared above. This is a step of forming an uneven shape on the joint surface. By using the laser processing apparatus using the water column as the optical path in this way, the surface of the cubic boron nitride sintered body is hardly oxidized, and a damage layer is not easily formed on the surface. For this reason, the reactivity between the surface of the cubic boron nitride sintered body and the material constituting the bonding layer is increased, and the bonding strength between the cubic boron nitride sintered body and the bonding layer can be increased.

  Various conditions of the laser processing apparatus using the water column used in this step as the optical path are as follows. That is, the nozzle diameter of the laser is 30 to 100 μm, the wavelength of the laser light is 500 to 1100 nm, the pulse width of the laser light is 10 to 300 ns, and the output of the laser light is 1 It is -100W, The repetition frequency of this laser beam is 1-100 kHz, and it is preferable that the processing speed of this laser beam shall be 100-3000 mm / s. By processing the joint surface of the cubic boron nitride sintered body under such conditions, the uneven shape as defined above can be formed.

  In addition, as a laser processing apparatus, the dry laser processing apparatus can also be used instead of the laser processing apparatus which uses the above water columns as an optical path. As conditions in this case, substantially the same conditions as described above can be employed.

<Step of lapping processing>
This step is a step of lapping the bonding surface irradiated with laser light as described above with a diamond abrasive brush. This step is optional when a laser processing device using a water column as an optical path is used as the laser processing device, but when a dry laser processing device is used, the bonding strength can be further increased by incorporating this step. If the damaged layer or the oxide layer on the processed surface by the laser is removed in the lapping process, the reactivity between the cubic boron nitride sintered body and the bonding layer is increased, and the bonding strength can be increased. Further, since the laser-processed surface has sharp convex portions, stress tends to concentrate. However, by rounding the convex portions by lapping, an effect of suppressing stress concentration can be expected.

  As such a diamond abrasive brush, for example, a paste in which a paste containing diamond abrasive grains having a particle diameter of 6 μm is kneaded into the brush can be employed. A processing time of about 1 to 10 minutes can be employed at 500 rpm.

<Step of Joining Cubic Boron Nitride Sinter to Tool Base Material via Joining Layer>
This step is a step of bonding the cubic boron nitride sintered body whose bonding surface is processed as described above to the tool base material through the bonding layer. In this step, the material constituting the bonding layer is sandwiched between the cubic boron nitride sintered body whose bonding surface has been treated as described above and the tool base material, and is placed in a vacuum furnace. Then, the pressure in the vacuum furnace is reduced to 2 × 10 ⁻² Pa or lower, and the temperature in the furnace is set to 750 ° C. or higher to dissolve the material constituting the bonding layer, so that the cubic boron nitride sintered body is obtained. And the tool base material.

  Next, the material forming the bonded layer is solidified by slowly cooling the bonded cubic boron nitride sintered body and the tool base material in a vacuum furnace (the material that forms the bonded layer by this cooling). Solidifies to become a bonding layer). Then, by polishing the joint surface between the cubic boron nitride sintered body and the tool base material, the joint surface between the cubic boron nitride sintered body and the tool base material is smoothed, and the cubic boron nitride of the present invention is obtained. A sintered tool can be obtained.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
A sample for a shear test was produced as follows.

<Step of preparing a cubic boron nitride sintered body>
First, TiN powder and Al powder were mixed at a mass ratio of TiN: Al = 4: 1. The mixture was then heat-treated at 1250 ° C. for 30 minutes in a vacuum. The mixture obtained by the heat treatment was pulverized using a cemented carbide ball having a diameter of 4 mm and a cemented carbide pot to obtain a raw material powder constituting the binder phase.

  The raw material powder constituting the binder phase obtained above and cubic boron nitride particles having an average particle size of 4 μm were blended so that the cubic boron nitride content was 90% by volume. These powders were put in a vacuum furnace, heated to 950 ° C., and held for 30 minutes to degas these powders.

  Next, these degassed powders were laminated on a cemented carbide support plate and filled into Nb capsules. Then, the capsule was installed in an ultrahigh pressure apparatus, the pressure in the ultrahigh pressure apparatus was 6 GPa, and sintering was performed at a temperature of 1500 ° C. for 20 minutes. Subsequently, the sintered body was taken out from the Mo capsule, the sintered body was ground, and further polished to prepare a shape, and a disc-shaped bulk sintered body having a diameter of 60 mm and a thickness of 1.2 mm was produced.

<Step of forming an uneven shape on the joint surface>
The bulk sintered body was set in a laser processing apparatus using a water column (water jet) as an optical path, and laser light was irradiated to one surface of the front and back of the bulk sintered body. The wavelength of the laser beam is 1064 nm, the laser beam pulse width is 100 ns, the laser beam output is 60 W, the laser repetition frequency is 6 kHz, the laser beam processing speed is 1000 mm / s, and the pitch width is 0.1 mm. It was 4 mm.

  Then, the bulk sintered body is cut by an electric discharge machine to form a square-bottomed cubic boron nitride sintered body having a square bottom surface with two sides of 2.5 mm × 2.5 mm and a thickness of 1.2 mm. A ligature was obtained.

<Step of bonding cubic boron nitride sintered body to cemented carbide through bonding layer>
Next, a rod-shaped cemented carbide having a rectangular shape with a longitudinal direction of 10 mm and a cross section of 2.5 × 2.5 mm was prepared. The mass ratio of one surface of 2.5 × 2.5 mm of the cemented carbide to the surface of the cubic boron nitride sintered body treated with laser is 50 mass% Cu, 25 mass% Zr, and 25 mass. A material constituting a bonding layer made of% Ti was placed and then placed in a vacuum furnace. Then, the pressure in the vacuum furnace is set to 1 × 10 ⁻⁵ Pa, the internal temperature is raised to 900 ° C., and the material constituting the bonding layer is melted, so that the cubic boron nitride sintered body is increased. Bonded to hard alloy.

  Then, the cemented carbide bonded with the cubic boron nitride sintered body was taken out of the reactor and allowed to cool. Next, the side surface of the square columnar sample joined with the cubic boron nitride sintered body and the cemented carbide was ground to prepare a sample for a shear test. The sample for the shear test is a finish processed into a rectangular parallelepiped having a 2 mm × 2 mm square on the bottom surface.

<Examples 2-5, Comparative Examples 1-2>
The shear test samples of Examples 2 to 5 were made in the same manner as in Example 1 except that the conditions for laser treatment were changed as shown in Table 1 below with respect to the sample for shear test of Example 1. A sample of was prepared. On the other hand, in Comparative Example 1, the bulk sintered body was lapped without performing laser treatment, and the surface was mirror-finished to obtain a cubic boron nitride sintered body, which was used for a shear test. A sample was made. In Comparative Example 2, a cubic boron nitride sintered body was produced on the bulk sintered body without performing laser treatment on the polished surface, and a sample for a shear test was produced using the cubic boron nitride sintered body.

<Example 6>
The cubic boron nitride sintered body tool of this example was produced as follows.

<Step of preparing a cubic boron nitride sintered body>
First, a WC powder having an average particle size of 2.0 μm, a Co powder having an average particle size of 1.5 μm, and an Al powder having an average particle size of 4 μm are mixed at a mass ratio of WC: Co: Al = 20: 70: 10, and vacuum Heat treatment was performed at 1000 ° C. for 30 minutes. The compound heat-treated above was pulverized using a φ4 mm cemented carbide ball to obtain a raw material powder constituting the binder phase.

  Then, the raw material powder constituting the binder phase obtained above and cubic boron nitride particles having an average particle diameter of 8 μm were blended so that the content of cubic boron nitride particles was 90% by volume. The powder obtained here was degassed by putting it in a vacuum furnace and raising the temperature to 950 ° C. and holding it for 30 minutes.

  Next, these degassed powders were laminated on a cemented carbide support plate and filled into Nb capsules. Then, the capsule was placed in an ultrahigh pressure apparatus, the pressure in the ultrahigh pressure apparatus was set to 7 GPa, and sintering was performed at a temperature of 1700 ° C. for 20 minutes. Subsequently, the sintered body was taken out from the Mo capsule, the sintered body was ground, and further polished to prepare a shape, and a disc-shaped bulk sintered body having a diameter of 60 mm and a thickness of 1.2 mm was produced.

<Step of forming an uneven shape on the joint surface>
The bulk sintered body was set in a dry laser processing apparatus, and one side of the front and back surfaces of the bulk sintered body was irradiated with laser light. The wavelength of the laser beam is 1064 nm, the laser beam pulse width is 100 ns, the laser beam output is 55 W, the laser repetition frequency is 6 kHz, the laser beam processing speed is 1100 mm / s, and the pitch width is 0.4 mm. It was.

  The bulk sintered body was cut to a thickness of 1.2 mm on the bottom surface of an isosceles triangle having two sides of 3.5 mm and an apex angle of 80 °. The cemented carbide base metal having a predetermined shape is subjected to counterboring for joining the cubic boron nitride sintered body cut as described above, with the laser-machined surface as the joining surface, Cu: 50% by mass, Zr: 25% by mass. %, Ti: Joined in a vacuum furnace using the material constituting the bonding layer having a mass ratio of 25% by mass. And after joining the cubic boron nitride sintered compact and the cemented carbide through the joining layer, it grind | polished and adjusted to the tool shape of CNGA120408.

<Examples 7 to 10 and Comparative Examples 3 to 4>
In Examples 7 to 10, after performing laser treatment under the same conditions as in Example 6, the processed surface subjected to the laser treatment is subjected to lapping for 60 to 300 seconds with a diamond abrasive brush. The values of a and c of the cubic boron nitride sintered body were adjusted. In Comparative Example 3, lapping treatment was performed without laser treatment, the surface was mirror-finished, and then joined to the tool base material using a joining layer. In Comparative Example 4, a groove having a depth of 0.5 mm and a groove width of 0.5 mm was formed on the bottom surface of the cubic boron nitride sintered body by using a grindstone at intervals of 1 mm.

<Characteristic measurement of cubic boron nitride sintered tool>
In the shear test samples of Examples 1 to 5 and Comparative Examples 1 and 2 prepared above, the laser-processed surface is used as the bonding surface, and the length of the straight portion is observed from one side of the surface perpendicular to the bonding surface A and b were measured using a stereomicroscope (product name: Leica MZ16 (manufactured by Leica Microsystem)) for a 2 mm region. The results are shown in the columns “a”, “b”, and “b / a” in Table 1.

  Further, in the cubic boron nitride sintered body tools of Examples 6 to 10 and Comparative Examples 3 to 4, both sides of the tool base material that are perpendicular to the laser machined surface that is the bonding surface having the largest area. Observed from the surface, a and b were measured using a device similar to the device used in Examples 1 to 5 above for a region having a straight line length of 1.5 mm. The results are shown in the “a”, “b”, and “b / a” columns of Table 2.

  Moreover, in the cubic boron nitride sintered body tools of Examples 6 to 10 and Comparative Examples 3 to 4, the maximum point is the point where the distance from the reference line is the maximum among the maximum values of the uneven shape, and the maximum A cut line passing through a point 0.02 mm in the vertical direction from the point toward the reference line and parallel to the reference line was drawn. And ratio C / L of the sum length C of the part through which a cutting line passes a joining layer with respect to length L = 1.5mm of this cutting line was computed. The results are shown in the column “C / L” in Table 2.

  Further, in each example and each comparative example, the ratio a / x of x to x when the average particle diameter of the cubic boron nitride sintered body particles constituting the cubic boron nitride sintered body is x is shown in Table 1. And in the column “a / x” in Table 2.

<Evaluation of cubic boron nitride sintered body tool>
For the shear test samples of Examples 1 to 5 and Comparative Examples 1 and 2, using a compression fracture tester (product name: Autograph (manufactured by Shimadzu Corporation)), shear strength at a load speed of 1 mm / min. (Kgf / mm ² ) was measured.

  From the results of the shear test shown in Table 1, it is clear that the cubic boron nitride sintered body tools of Examples 1 to 5 have a shear strength of 3 times or more compared with that of Comparative Examples 1 and 2. became. When the fracture surfaces of Examples 1 to 5 and Comparative Examples 1 and 2 were confirmed, the cubic boron nitride sintered body tools of Examples 1 to 5 were all interfaces between the cubic boron nitride sintered body and the bonding layer. The cubic boron nitride sintered body or the tool base material was broken without shear fracture. On the other hand, the cubic boron nitride sintered body tools of Comparative Examples 1 and 2 were peeled off at the interface between the cubic boron nitride sintered body and the bonding layer.

  As described above, the bonding strengths of the cubic boron nitride sintered body tools of Examples 1 to 5 and Comparative Examples 1 and 2 are different from each other in that the bonding surfaces of the cubic boron nitride sintered bodies of Examples 1 to 5 are uneven. Is not formed on the joint surfaces of the cubic boron nitride sintered bodies of Comparative Examples 1 and 2, or even if the unevenness is formed, the shape is small. It is considered a thing.

  With respect to the cubic boron nitride sintered body tools of Examples 6 to 10 and Comparative Examples 3 to 4, the blank removal life (minutes) when cutting under the following cutting conditions was calculated.

(Cutting conditions)
Work material: SUJ2 (HRC64)
Cutting conditions: Vc = 150 m / min
f = 0.5mm / rev
a _p = 0.3 mm
From the result of the blank cutting life shown in Table 2, C / L is 5 and Example 6 has a peak with a peak having a maximum value. It is considered that cracks occurred in the sintered body, and the blank removal life was shorter than in Examples 7-9. On the other hand, in Example 10, since C / L is 80 and the shape of the peak having the maximum value is small, the effect of improving the bonding strength by the anchor effect cannot be sufficiently obtained, which is compared with Examples 7-9. Thus, it is considered that the blank removal life was short.

  Further, in Comparative Example 3, since the unevenness was not formed on the joint surface of the cubic boron nitride sintered body, the blank removal life was remarkably short. In Comparative Example 4, it is presumed that the blank removal life was remarkably short because the value of a indicating the height of the peak was small.

  Although the embodiments and examples of the present invention have been described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 Cubic boron nitride sintered body tool, 2 Cubic boron nitride sintered body, 3 bonding layer, 4 tool base material.

Claims (6)

A cubic boron nitride sintered body tool in which a cubic boron nitride sintered body is bonded to a tool base material via a bonding layer,
The cubic boron nitride sintered body contains 75% by volume or more of cubic boron nitride particles,
The bonding layer includes Ti, Zr, and Cu,
In an arbitrary cut surface when the cubic boron nitride sintered body tool is cut by a plane perpendicular to the bonding surface having the largest area among the bonding surfaces of the cubic boron nitride sintered body and the bonding layer, The cubic boron nitride sintered body has an uneven shape on its surface,
Dividing the area of the uneven shape into two equal parts, and using a straight line parallel to the joining surface of the joining layer and the tool base material as a reference line,
The sum of the maximum value of the distance between the reference line and the maximum value of the uneven shape and the maximum value of the distance between the reference line and the minimum value of the uneven shape is a,
In the uneven shape, if the maximum value of the distance in the reference line direction between adjacent maximum values is b,
A is 0.02 mm or more and 0.2 mm or less,
Said b is 0.02 mm or more and 1 mm or less,
Among the maximum values of the concavo-convex shape, the point having the maximum distance from the reference line is taken as the maximum point, passes through a point 0.02 mm away from the maximum point in the vertical direction toward the reference line, and the reference If a straight line parallel to the line is a cut line,
The ratio C / L of the sum length C of the portion where the cut line passes through the bonding layer with respect to the length L of the cut line is 0 or more and 0.6 or less, and the ratio of b to the a The cubic boron nitride sintered body tool , wherein b / a is 1 or more . The cubic boron nitride sintered body includes cubic boron nitride particles and a binder phase,
The cubic boron nitride sintered body tool according to claim 1 , wherein a ratio a / x of a to x is 1 or more, where x is an average particle diameter of the cubic boron nitride particles. The cubic boron nitride sintered body tool according to claim 1 or 2 , wherein the tool base material is made of cemented carbide, cermet, or ceramics. It is a manufacturing method of the cubic boron nitride sintered compact tool according to any one of claims 1 to 3 ,
By irradiating a laser beam using a laser processing apparatus having a water column as an optical path for the bonding surface having the largest area among the surfaces of the cubic boron nitride sintered body, the a is applied to the bonding surface . A step of forming a concavo-convex shape that is 0.02 mm to 0.2 mm, and b is 0.02 mm to 1 mm ;
Bonding the cubic boron nitride sintered body to a tool base material through a bonding layer,
The laser nozzle diameter is 30-100 μm,
The wavelength of the laser beam is 500 to 1100 nm,
The pulse width of the laser light is 10 to 300 ns,
The output of the laser beam is 3 to 100 W,
The repetition frequency of the laser light is 1 to 100 kHz,
The processing speed of the laser beam is 100 to 3000 mm / s,
A method for manufacturing a cubic boron nitride sintered body tool, wherein the pitch width of the laser is 0.02 mm to 1 mm . The manufacturing method of the cubic boron nitride sintered compact tool of Claim 4 including the step of lapping with a diamond abrasive brush with respect to the said joint surface irradiated with the said laser beam. It is a manufacturing method of the cubic boron nitride sintered compact tool according to any one of claims 1 to 3 ,
By irradiating a laser beam using a dry laser processing apparatus to the bonding surface having the largest area among the surfaces of the cubic boron nitride sintered body, the a is 0.02 mm or more. A step of forming a concavo-convex shape that is 0.2 mm or less and b is 0.02 mm or more and 1 mm or less ;
A step of lapping with a diamond abrasive brush on the joint surface irradiated with the laser beam;
Bonding the cubic boron nitride sintered body to a tool base material through a bonding layer,
The laser nozzle diameter is 30-100 μm,
The wavelength of the laser beam is 500 to 1100 nm,
The pulse width of the laser light is 10 to 300 ns,
The output of the laser beam is 3 to 100 W,
The repetition frequency of the laser light is 1 to 100 kHz,
The processing speed of the laser beam is 100 to 3000 mm / s,
A method for manufacturing a cubic boron nitride sintered body tool, wherein the pitch width of the laser is 0.02 mm to 1 mm .

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