JP2020157430A - Super hard alloy drill with spiral oil holes - Google Patents

Abstract

To provide a super hard alloy drill with spiral oil holes and a surface-coated super hard alloy drill having an excellent breakage resistance.SOLUTION: There is provided a super hard alloy drill with spiral oil holes, which is made of WC-based super hard alloy having a composition consisting of 6% by mass or more and 15% by mass or less of Co, 0.1% by mass or more and 5% by mass or less in the total amount of one or two or more carbides selected from Ti, Zr, Cr, V, Ta and Nb, and the balance WC and unavoidable impurities. Oil holes for supplying cutting oil to the tip of the drill are formed in a spiral shape inside the drill. A metal-enriched layer containing Co as a main component is formed on the inner wall surface of the oil holes. The Co content of the metal-enriched layer is 1.5 times or more the average Co content of the WC-based super hard alloy. The average thickness of the metal-enriched layer is 0.5 μm or more and 10.0 μm or less. There is also provided a surface-coated super hard alloy drill in which the drill is coated with a hard coating layer.SELECTED DRAWING: Figure 2

Description

The present invention is a cemented carbide drill with a spiral oil hole, and in particular, prevents the drill from breaking due to cracks generated around the oil hole, and the wall thickness of the drill around the oil hole becomes thin. The present invention relates to a cemented carbide drill with a spiral oil hole, which prevents the drill from breaking due to the above and enables high-precision drilling with sufficient tool rigidity.

Conventionally, as a drill used for drilling, it is made of cemented carbide with a spiral oil hole in which oil holes are spirally formed in the axial direction of the drill body for the purpose of improving chip evacuation and cooling the drill edge. Drills are known.
Since it is necessary to further increase the oil discharge amount in order to improve the cutting efficiency, an attempt has been made to increase the oil hole diameter.

For example, Patent Document 1 describes the opening of each oil hole at the end of a shank in a drill with an oil hole provided with a pair of oil holes communicating from a pair of oil holes at the cutting edge of the drill to a pair of oil holes at the end of the shank. In order to increase the area, a pair of inclined surfaces or conical surfaces for cutting each oil hole are provided at the end of the shank, and the inclined surface angle of the inclined surface or conical surface with respect to the drill axis is in a range of more than 15 ° to 75 °. By doing so, a drill with an oil hole that can supply a sufficient amount of coolant to the drill bit edge has been proposed.

Further, in Patent Document 2, a drill with a coolant hole is provided with a coolant hole that opens in the relief surface at the tip of the drill while twisting in parallel with a chip discharge groove extending toward the rear end side in the axial direction while twisting around the drill axis. It has been proposed that the hole shape of the coolant hole be substantially triangular and the corners be rounded. According to this drill with a coolant hole, the amount of coolant supplied can be increased without impairing the strength of the drill body. It is said that it can be made to do.

Further, in Patent Document 3, in a tool with an oil hole such as a drill, a reamer, and an end mill provided with an oil hole, a tool main body made of cemented carbide or cermet is arranged as a core material for forming an oil hole at the time of sintering. It is known that a toughened metal layer can be formed on the inner wall of an oil hole by reacting with or diffusing a pipe-shaped metal material to improve the breakage resistance of a tool.

Japanese Unexamined Patent Publication No. 2008-296327 Japanese Unexamined Patent Publication No. 2011-20254 Japanese Unexamined Patent Publication No. 8-215912

In Patent Documents 1 and 2, a proposal for increasing the amount of oil discharged has been made for a drill with an oil hole, and the efficiency of drilling is improved by this. However, a small-diameter drill, for example, a cutting edge diameter of 3 mm In a small-diameter drill with a diameter less than that, since the radius of curvature of the oil hole becomes small, cracks are likely to occur around the oil hole, and this crack may cause breakage of the drill.
In addition, when the oil hole diameter is increased, the wall thickness of the drill may become thin around the oil hole, so that sufficient wall thickness and strength cannot be secured, and the drill starting from the oil hole may break. There is a problem.
Further, in Patent Document 3, a pipe-shaped or rod-shaped metal material is used for forming an oil hole, and a toughened metal layer is provided on the inner wall of the oil hole to improve breakage resistance. Since the core material component has a concentration gradient that gradually decreases from the central portion to the outer periphery, it can be seen that the coupling phase component of the entire tool is large and the rigidity is reduced. In a small-diameter drill with a cutting edge diameter of less than 3 mm, since only one oil hole can be formed in the center of the tool, there is a limit to increasing the oil hole area itself, so that the amount of oil discharged is limited. As a result, chip evacuation is low, high-efficiency machining becomes difficult, and the rigidity of the tool itself decreases, so that hole bending becomes noticeable when drilling a steel material, etc., and the desired accuracy is achieved. It may be difficult to drill holes with.

Therefore, from the above viewpoint, the present inventors have prevented the occurrence of cracks around the oil hole and at the same time around the oil hole in a cemented carbide drill with a spiral oil hole, particularly a small-diameter drill having a cutting edge diameter of less than 3 mm. Diligent research to prevent breakage from thin-walled parts, improve breakage resistance of cemented carbide drills with spiral oil holes, and ensure tool rigidity so that hole bending during drilling is minimized. As a result of repeating the above, the following findings were obtained.

The present inventors have found that one of the causes of breakage of a hard alloy drill with a spiral oil hole is the generation and propagation of cracks from around the oil hole, and the generation of cracks around the oil hole is the oil hole. It is predicted that it can be suppressed by improving the strength and toughness of the inner surface, and that if the strength and toughness of the inner surface of the oil hole are improved, the progress of fracture from the thin part around the oil hole can also be suppressed. Based on this, a metal-enriched layer containing Co as a main component was formed on the inner wall surface of the oil hole of a superhard alloy drill with a spiral oil hole to improve strength and toughness. When the thickness is large, the generation and growth of cracks around the oil hole are suppressed, and even when the oil hole diameter is increased in order to secure a sufficient oil discharge amount, the oil hole It has been found that the progress of destruction from the surrounding thin-walled portion can be suppressed, and that the tool rigidity is sufficiently secured, so that the hole accuracy can be prevented from being lowered due to the hole bending during drilling.
Further, according to the cemented carbide drill with a spiral oil hole in which the metal enriched layer having a predetermined thickness is formed on the inner wall surface of the oil hole, a sufficient oil discharge amount can be secured without fear of breakage, and the hole is bent. It was found that high-efficiency and high-precision machining can be performed because it is also suppressed.
In particular, in a small-diameter drill having a cutting edge diameter of less than 3 mm, since the radius of curvature of the oil hole is small, cracks are likely to occur around the oil hole, and breakage is likely to occur due to the progress of the crack. According to the drill made of cemented carbide with holes, it was found that the metal-enriched layer formed on the inner wall surface of the oil hole suppresses the generation and growth of cracks, so that the effect of improving breakage resistance is remarkable. is there.

Further, conventionally, in order to improve the wear resistance of the drill, at least one layer or more of TiN, TiCN, TiAlN, TiAlSiN, TiSiN, TiAlCN, TiAlCrN, AlCrN, AlCrSiN, CrN, etc. is formed on at least the tip of the drill bit. Although the hard coating layer of the above is formed, the tool characteristics of the drill of the present invention can be further improved by forming the hard coating layer at least at the tip of the cutting edge of the drill. ..
If the thickness of the metal-enriched layer formed on the inner wall surface of the oil hole of the drill is within a predetermined thickness range, not only is it excellent in breakage resistance, but also wear resistance without causing peeling of the hard coating layer. Because it is excellent, the life of the tool can be extended.

The present invention has been made based on the above findings and has the following features.
(1) Co is 6% by mass or more and 15% by mass or less, and the total amount of one or two or more kinds of carbides selected from Ti, Zr, Cr, V, Ta and Nb is 0.1% by mass or more and 5% by mass or less. In a cemented carbide drill with a spiral oil hole composed of a WC-based cemented carbide having a composition consisting of the balance WC and unavoidable impurities.
An oil hole for supplying cutting oil to the tip of the drill is formed in a spiral shape inside the drill along the flute groove of the drill, and the inner wall surface of the oil hole is enriched with metal containing Co as a main component. The layer is formed, and the Co content of the metal-enriched layer is 1.5 times or more the average Co content of the WC-based cemented carbide, and the average thickness of the metal-enriched layer is 0.5 μm or more. A cemented carbide drill with a spiral oil hole, characterized by a diameter of 0.0 μm or less.
(2) The cemented carbide drill with a spiral oil hole according to (1) above, wherein the cutting edge diameter of the drill tip of the drill is less than 3 mm.
(3) In the cemented carbide drill with a spiral oil hole according to (1) or (2), at least the surface of the tip of the drill is covered with a hard coating layer. Carbide alloy drill with oil holes.
(4) The hard coating layer is one or more layers selected from TiN layer, TiAlN layer, TiAlSiN layer, TiSiN layer, TiAlCN layer, TiAlCrN layer, AlCrN layer, AlCrSiN layer and CrN layer. The hard alloy drill with a surface-coated spiral oil hole according to (3) above.

In the cemented carbide drill with a spiral oil hole of the present invention, a metal-enriched layer containing Co as a main component is formed on the inner wall surface of the oil hole, so that the generation and growth of cracks around the oil hole are suppressed. Even when the oil hole is enlarged, the progress of destruction from the thin part around the oil hole is suppressed, so the amount of oil discharged during drill cutting can be increased, and the amount of feed during cutting can be increased. However, since the drill is less likely to break and the tool rigidity is secured, hole bending is suppressed, and high-efficiency and high-precision machining can be performed.
In particular, in a small-diameter drill having a cutting edge diameter of less than 3 mm at the tip of the drill, the effect of improving breakage resistance is remarkable.

Further, in the surface-coated cemented carbide drill of the present invention in which a hard coating layer is coated on at least the tip of the cemented carbide drill with a spiral oil hole, the breakage resistance of the drill should be lowered. Not only is there no peeling of the hard coating layer, so it has excellent wear resistance and the tool characteristics are further improved.

The external schematic diagram of the cemented carbide drill with a spiral oil hole of this invention is shown. (A) shows a schematic cross-sectional view of the cemented carbide drill with a spiral oil hole of the present invention cut in a cross section perpendicular to the drill axis, and (b) shows an oil hole inner wall along the direction of the drill axis. An enlarged schematic view of the part is shown.

The present invention will be described in more detail with reference to the drawings.

FIG. 1 is a schematic external view of the cemented carbide drill with a spiral oil hole of the present invention, and FIG. 2A is a cross section of the cemented carbide drill with a spiral oil hole of the present invention perpendicular to the axis. FIG. 2 (b) shows an enlarged schematic view of an oil hole inner wall portion along the direction of the center of the drill axis.
As shown in FIG. 1, the cemented carbide drill with a spiral oil hole of the present invention (hereinafter referred to as “the drill of the present invention”) has an oil hole for discharging cutting oil into the drill tip 2 of the drill body 1. The oil hole 3 is formed in a spiral shape inside the drill body 1 along the flute groove 4 of the drill body 1.

Further, as shown in FIG. 2B, a metal enrichment layer 5 containing Co as a main component is formed on the inner wall surface of the oil hole 3.
Although not shown, in order to improve the wear resistance of the drill of the present invention, at least the surface of the drill tip 2 can be coated with a hard coating layer by, for example, the PVD method. The drill is coated with a hard coating layer (for example, one layer or two or more layers selected from TiN layer, TiAlN layer, TiAlSiN layer, TiSiN layer, TiAlCN layer, TiAlCrN layer, AlCrN layer, AlCrSiN layer and CrN layer) by the PVD method. The formed drill is a cemented carbide drill with a surface-coated spiral oil hole (hereinafter referred to as "the coated drill of the present invention").

In the drill of the present invention and the coated drill of the present invention, the drill body 1 contains 6% by mass or more and 15% by mass or less of Co, and is the total of one or more carbides selected from Ti, Zr, Cr, V, Ta and Nb. It is composed of a WC-based cemented carbide having a composition of 0.1% by mass or more and 5% by mass or less, the balance WC, and unavoidable impurities.

Co, which is a constituent component of the WC-based cemented carbide, has the effect of improving the sinterability, forming a bonded phase, and improving the strength of the drill made of the WC-based cemented carbide. If the content is less than 6% by mass, the desired strength cannot be secured, while if the content ratio exceeds 15% by mass, the wear progresses rapidly. Therefore, the Co content is 6% by mass or more and 15%. It was set to mass% or less.

Further, one or more carbides selected from Ti, Zr, Cr, V, Ta and Nb are dispersed as solid-dissolved or metal composite carbides in the Co-based bonding phase at the time of sintering as in the case of the WC component. Although it has an action of improving the high temperature strength and hardness of a cemented carbide drill, if the total content of the carbides is less than 0.1% by mass, the desired improvement effect cannot be obtained in the action, while the carbides. If the total content of the carbide exceeds 5% by mass, the toughness is lowered and defects are likely to occur. Therefore, the total of one or more carbides selected from Ti, Zr, Cr, V, Ta and Nb. The content was determined to be 0.1% by mass or more and 5% by mass or less.
The contents of Ti, Zr, Cr, V, Ta, and Nb are all carbide conversion values.

The drill of the present invention and the coated drill of the present invention contain Co as a main component on the inner wall surface of the oil hole 3 exposed to the drill tip 2 and the inner wall surface of the oil hole 3 spirally formed inside the drill body 1. The metal enriched layer 5 is formed.
Since the metal-enriched layer 5 containing Co as a main component is formed on the inner wall surface of the oil hole 3, the generation and growth of cracks around the oil hole 3 are suppressed. In particular, in a small-diameter drill having a cutting edge diameter of less than 3 mm, since the radius of curvature of the oil hole 3 is small, cracks are usually likely to occur around the oil hole 3, but a metal enrichment layer 5 is formed. By doing so, the generation and growth of cracks are suppressed.
Further, when the diameter of the oil hole 3 is expanded in order to secure a sufficient oil discharge amount for high-efficiency machining, as a result, the circumference of the oil hole 3 becomes a thin wall portion, but on the inner wall surface of the oil hole 3. By forming the metal-enriched layer 5, the progress of fracture from the thin-walled portion is suppressed.

In addition, since the average thickness of the metal-enriched layer is 0.5 μm to 10.0 μm, the rigidity of the drill itself is maintained, so that hole bending is minimized even when high-efficiency machining is performed, and high accuracy is achieved. Processing can also be realized.
However, if the average thickness of the metal-enriched layer 5 containing Co as a main component formed on the inner wall surface of the oil hole 3 is less than 0.5 μm, the effect of preventing the occurrence of cracks around the oil hole 3 is not sufficient, and as a result. On the other hand, if the average thickness of the metal enrichment layer 5 exceeds 10.0 μm, cracks may occur in the circumferential direction of the oil hole 3 or the hard coating layer may peel off. It may occur.
Therefore, the average thickness of the metal-enriched layer 5 containing Co as a main component formed on the inner wall surface of the oil hole 3 is set to 0.5 μm or more and 10.0 μm or less. The preferable average thickness is 0.5 μm or more and 5.0 μm or less, and the more preferable average thickness is 0.5 μm or more and 3.0 μm or less.

The "metal-enriched layer 5 containing Co as a main component" in the present invention means that the Co content in the metal-enriched layer 5 is the average Co content of the WC-based cemented carbide (substantially more than WC-based). A region that is 1.5 times or more the average Co content inside the cemented carbide).
The "metal-enriched layer 5 containing Co as a main component" contains Ti, Zr, Cr, V, Ta, and Nb in addition to the W component, but the other component elements other than W are Co. Since it is a very small amount, it is expressed as "Co is the main component ...".
The Co content in the metal-enriched layer 5 was determined as described above because the Co content in the metal-enriched layer 5 was less than 1.5 times the average Co content of the WC-based cemented carbide. This is because the effect of improving the strength and toughness of the inner wall surface of the oil hole 3 is not sufficient, so that the generation and growth of cracks cannot be sufficiently suppressed.
The Co content in the metal enriched layer 5 is more preferably 1.8 times or more, and further preferably 2.0 times or more, the average Co content of the WC-based cemented carbide.

The Co content in the metal enriched layer formed on the inner wall surface of the oil hole 3 can be measured by using an Auger electron spectrophotometer (AES) for a cross section perpendicular to the drill axis of the drill of the present invention. ..
For example, as shown in FIG. 2, using an Auger electron spectroscopic analyzer (AES), in a cross section perpendicular to the drill axis, Co content is contained in an area of 0.1 μm in length × 10 μm in width in the normal direction of the inner wall of the oil hole. The amount was measured sequentially starting from the inner wall of the oil hole, and the Co content in each measurement area was the average Co content of the WC-based cemented carbide (this is substantially the average Co content inside the WC-based cemented carbide). A region having a content of 1.5 times or more is specified as the metal-enriched layer 5 containing Co as a main component, and the areas are totaled to obtain the thickness of the metal-enriched layer 5. Further, such measurements are performed at a plurality of places, and the average value of the thickness of the metal-enriched layer calculated for each is obtained as the average thickness of the metal-enriched layer 5.
At the same time, the Co content of the region belonging to the specified metal enriched layer 5 is averaged, and this value is divided by the average Co content inside the WC-based cemented carbide to divide the Co content in the metal enriched layer 5. The concentration ratio of the amount (the ratio of the Co content in the metal enriched layer 5 to the average Co content of the WC-based cemented carbide) can be determined.

Further, for example, by the PVD method, a TiN layer, a TiAlN layer, a TiSiN layer, a TiAlSiN layer, etc. are formed on the surface of the metal enrichment layer 5 formed on the inner wall surface of the oil hole 3 exposed at least on the drill tip portion 2 of the drill 1. When the coating drill of the present invention is prepared by coating one or two or more hard coating layers selected from TiAlCN layer, TiAlCrN layer, AlCrN layer, AlCrSiN layer and CrN layer, the average thickness of the metal enrichment layer 5 is 10 μm. If it exceeds, the adhesion between the metal enrichment layer 5 formed on the inner wall surface of the oil hole 3 exposed on the drill tip 2 and the hard coating layer is lowered, and the hard coating layer is peeled off during cutting. Therefore, from this point of view, the maximum average thickness of the metal enrichment layer is set to 10 μm.

In the drill of the present invention, first, a press-formed body with oil holes of a cemented carbide having a predetermined composition is prepared, and this is calcined and sintered under predetermined conditions, and the outer periphery of the sintered body is formed by a predetermined drill. It can be produced by processing it into a shape.
Further, after that, the coating drill of the present invention can be produced by forming a hard coating layer by vapor deposition by the PVD method.
In the above-mentioned production method, production of a press-formed body with an oil hole has already been known before the application of the present application, as shown in, for example, Japanese Patent Application Laid-Open No. 11-293303.
Therefore, in the present invention, a press-formed body made of a cemented carbide with a spiral oil hole is produced according to a conventionally known production process (for example, the production process shown in JP-A-11-293303).
Then, after calcining this press-formed body, it is sintered under the following conditions to prepare a cemented carbide sintered body with a spiral oil hole.
First, the press-molded body is charged into a furnace and calcined, and then, for example, the calcined press-molded body is heated up to 1250 ° C. at a heating rate of 10 ° C./min, and further at 1400 ° C. The temperature was raised at a heating rate of 1.5 ° C./min, held at 1400 ° C. for about 60 minutes, and then energized in an Ar atmosphere in the temperature range of 1400 ° C. to 1250 ° C. until the liquid phase solidified. By cooling, the mixture is slowly cooled to 1250 ° C. at a cooling rate of 1.0 ° C./min, and then cooled to room temperature.
By sintering under the above sintering conditions, a cemented carbide sintered body with a spiral oil hole in which a metal-enriched layer containing Co as a main component is formed on the inner wall of the oil hole at the same time as the press-formed body is sintered. To make.
Then, by processing the outer circumference of this sintered body, a main cutting edge, a rake face, etc. are formed and adjusted to a predetermined drill shape and size, and a cemented carbide drill with a spiral oil hole of the present invention (drill of the present invention). ) Can be produced.
In the drill produced by the method for manufacturing a drill shown in Patent Document 3, a toughened metal layer is formed on the inner wall of the oil hole by reaction or diffusion with a pipe-shaped metal material arranged as a core material for forming an oil hole. The thickness corresponding to the metal-enriched layer of the tool of the present invention is at least 100 μm or more, and in that case, the tool rigidity is lowered, so that the hole bending becomes remarkable and the drilled hole is formed. Since the accuracy is lowered and only one oil hole can be formed in the center, the oil discharge amount cannot be increased as compared with the tool of the present invention, and as a result, the high efficiency realized by the tool of the present invention is achieved. Moreover, high-precision machining cannot be performed.

Further, with respect to the drill of the present invention, at least on the surface of the tip of the drill, for example, by PVD method, it is selected from TiN layer, TiAlN layer, TiSiN layer, TiAlSiN layer, TiAlCN layer, TiAlCrN layer, AlCrN layer and CrN layer. A cemented carbide drill with a surface-coated spiral oil hole of the present invention (the coated drill of the present invention) can be produced by depositing and forming one or two or more hard coating layers.

Next, the present invention will be specifically described with reference to Examples.

[Example 1]
(A) a press-molding material powder, both having an average particle diameter of 0.4 to 2.0 .mu.m (d50), Co powder, TiC powder, ZrC powder, _Cr 3 _{C 2} powder, VC powder, TaC powder, NbC powder and WC powder were prepared, and these raw material powders were blended into the blending composition shown in Table 1, and this was mixed and kneaded with a petroleum wax and an organic solvent in a kneading device to prepare a press raw material.
Next, the press raw material was supplied to the extrusion press device and extruded from the mold of the holder attached to the other end of the extrusion press device by the extrusion screw to prepare an extrusion press molded body.
The press-molded body to be extruded during extrusion from the mold was rotated and extruded by a spiral groove formed on the inner peripheral surface of the mold so as to be twisted in the direction of the spiral of the groove.
In the press-molded body that has been extruded and press-molded, a large number of spiral ridges are formed on the outer periphery of the press-molded body by the grooves of the mold, and inside the press-molded body, a twisted pin of a core attached to the mold A pair of spiral twisted holes (finally, spiral oil holes) were formed symmetrically with respect to the central axis of the press-formed body.

(B) Temporary firing and molding (cutting) of the press-formed body
Then, the press-formed body was placed in a sintering furnace, and for example, in a vacuum of 100 Pa or less, the temperature was raised at a temperature rising rate of 10 ° C./min for 2 hours at 80 ° C. and 45 minutes at 150 ° C. After holding at 450 ° C. for 2 hours each, the temperature was raised to 750 ° C. and held for 1 hour by calcining.
Then, this calcined body was cut into a predetermined length and formed into a predetermined shape.

(C) Cemented Carbide Alloy Sintered Body Then, the calcined press-formed body was placed in a sintering furnace and sintered under the conditions shown in Table 2 to prepare a cemented carbide sintered body with spiral oil holes. did.
An example of sintering conditions is as follows, for example.
The temperature was raised from room temperature to 1250 ° C. at a temperature rise rate of 10 ° C./min, and in an atmosphere of Ar partial pressure of 2667 Pa, the temperature was raised to a temperature range of 1250 ° C. to 1400 ° C. at a temperature rise rate of 1.5 ° C./min. After that, the mixture was held at a temperature of 1400 ° C. for 60 minutes in an atmosphere of Ar partial pressure of 3997 Pa, and then the temperature range of 1400 ° C. to 1250 ° C. until the liquid phase solidified in an atmosphere of Ar partial pressure of 3997 Pa was 1.0 ° C. By energizing and cooling to a slow cooling rate of / min and then furnace-cooling in the temperature range from 1250 ° C to room temperature, the press-formed body is sintered and at the same time, a metal containing Co as a main component is formed on the inner wall of the oil hole. An enriched layer was formed.

(D) Cemented Carbide Drill with Spiral Oil Holes After scraping off the spiral ridges on the outer circumference of the cemented carbide sintered body with spiral oil holes obtained above, a pair of scraped outer circumferences The flute groove is formed so as to spirally twist between the spiral-shaped twisted holes (spiral oil holes) in the circumferential direction, and the tip of the drill is formed by sharpening the cutting edge at the tip of the sintered body. On the other hand, by providing a shank portion at the rear end of the sintered body, the drills 1 to 6 of the present invention made of cemented carbide with spiral oil holes shown in Table 4 were produced.
An example of the cemented carbide drill with a spiral oil hole created above is a twist drill having an oil hole diameter of 0.35 mm and a cutting edge diameter of 2.0 mm at the tip of the drill.

For comparison, comparative example drills 1 to 4 made of cemented carbide with spiral oil holes were produced by the following procedure.
The press-formed body was prepared in the steps (a) and (b), and after calcining the press-molded body, the press-molded body was sintered under the conditions shown in Table 3, and then the step (d) was performed. Comparative example drills 1 to 6 made of cemented carbide with spiral oil holes shown in Table 5 were produced.

With respect to the drills 1 to 6 of the present invention and the drills 1 to 4 of Comparative Examples, the composition of the components constituting the drills 1 to 6 was measured, and the average thickness (μm) of the metal-enriched layer containing Co as the main component and the metal on the inner wall of the oil hole The concentration rate of the Co content in the enriched layer was measured and calculated.
Specifically, the composition of each component (excluding Co) is measured at a plurality of points in the cross-sectional direction perpendicular to the drill axis using an Auger electron spectroscopic analyzer (AES), and each drill is used. The composition of the constituent cemented carbide (however, the composition in terms of carbide) was used.
Regarding Co, first, the Co content inside the WC-based cemented carbide (the central portion of the wall thickness of each part of the drill) was measured at a plurality of places, and these were averaged to obtain the average Co content.
On the other hand, the Co content is measured in the cross-sectional direction perpendicular to the drill axis, and the region where the Co content at the measurement point is 1.5 times or more the average Co content is the metal richness containing Co as the main component. It is specified as the chemical layer 5, and the area is totaled to obtain the thickness of the metal-enriched layer 5. Further, such measurements were performed at a plurality of places, and the average value of the thickness of the metal-enriched layer calculated for each was obtained as the average thickness of the metal-enriched layer 5.
At the same time, the Co content of the region belonging to the specified metal enriched layer 5 is averaged, and this value is divided by the average Co content inside the WC-based cemented carbide to divide the Co content of the metal enriched layer 5 by the average Co content. The concentration ratio of the amount (the concentration ratio of the Co content in the metal enriched layer 5 with respect to the average Co content of the WC-based cemented carbide) was determined.
Tables 4 and 5 show these values.

Next, the following drilling and cutting tests were carried out for the drills 1 to 6 of the present invention, the drills 1 to 4 of Comparative Example, and the drill 1 of Reference Example.

≪Drilling cutting test 1≫
Work material-planar dimensions: JIS A6061 plate material,
Cutting speed (vc): 180 m / min. ,
Feed (f): 0.25 mm / rev,
Drilling depth (Id): 20 mm (through hole),
Internal refueling (oil-based) Supply pressure: 3.0 MPa
Drilling and cutting test of aluminum alloy under the conditions of.

≪Drilling cutting test 2≫
Work material-planar dimensions: JIS / AC4B plate material,
Cutting speed (vc): 150 m / min. ,
Feed (f): 0.28 mm / rev,
Drilling depth (Id): 20 mm (through hole),
Internal refueling (oil-based) Supply pressure: 3.0 MPa,
Drilling and cutting test of aluminum alloy under the conditions of.

In both the drilling cutting test 1 and the drilling cutting test 2, the number of drilling operations until the flank wear width of the cutting edge surface of the drill tip reaches 0.3 mm is measured, and the presence or absence of breakage of the drill is measured. investigated.
Further, the drilling accuracy (3σ) of the work material was measured by the following method.
The hole positions on the inlet side and outlet side of the hole drilled by drilling were measured, the deviation of the hole position was calculated from the result, and the standard deviation (σ) was calculated by statistical processing, and the machining accuracy was set to 3σ. ..
Tables 6 and 7 show the test results.

According to the results of Tables 6 and 7, in the drills 1 to 6 of the present invention, not only the drilling accuracy was not lowered, but also the occurrence of breakage in a short time was not observed.
However, all of the comparative example drills 1 to 4 had a short life due to the occurrence of breakage.

[Example 2]
Various hard coating layers shown in Table 8 are formed on the drills 1 to 6 of the present invention, the drills 1 to 4 of Comparative Examples, and the drill 1 of Reference Example produced in Example 1 by using an arc ion plating apparatus. As a result, the coated drills 11 to 16 of the present invention, the coated drills 11 to 14 of the comparative example, and the coated drill 11 of the reference example were produced.

A drilling cutting test 3 and a drilling cutting test 4 were carried out for the coated drills 11 to 16 of the present invention, the coated drills 11 to 14 of the comparative example, and the coated drill 11 of the reference example.

≪Drilling cutting test 3≫
Work Material-Plane Dimension: JIS / SUS304 Plate Material,
Cutting speed (vc): 80 m / min. ,
Feed (f): 0.24 mm / rev,
Drilling depth (Id): 20 mm (through hole),
Internal refueling (oil-based) Supply pressure: 3.0 MPa,
Drilling and cutting test of stainless steel under the conditions of.

≪Drilling cutting test 4≫
Work Material-Plane Dimension: JIS / SCM440 Plate Material,
Cutting speed (vc): 120 m / min. ,
Feed (f): 0.25 mm / rev,
Drilling depth (Id): 20 mm (through hole),
Internal refueling (oil-based) Supply pressure: 3.0 MPa,
Drilling and cutting test of alloy steel under the conditions of.
Tables 9 and 10 show the test results.

According to the results of Tables 9 and 10, in the coated drills 11 to 16 of the present invention, peeling of the hard coating layer and occurrence of breakage in a short time were not observed, and the drilling accuracy was not lowered.
On the other hand, the coated drill tools 11 to 14 of the comparative example have reached the end of their life due to breakage in a short time.

The drill of the present invention and the coated drill of the present invention exhibit excellent breakage resistance and stable machining accuracy in drilling of work materials such as aluminum alloys, stainless steels, and alloy steels, and have excellent cutting performance over a long period of time. Therefore, it is possible to fully and satisfactorily cope with high performance of the cutting machine, labor saving and energy saving of the cutting process, and cost reduction.

Claims (4)

Co is 6% by mass or more and 15% by mass or less, the total amount of one or two or more kinds of carbides selected from Ti, Zr, Cr, V, Ta and Nb is 0.1% by mass or more and 5% by mass or less, and the balance WC. And in a cemented carbide drill with a spiral oil hole composed of a WC-based cemented carbide having a composition of unavoidable impurities.
An oil hole for supplying cutting oil to the tip of the drill is formed in a spiral shape inside the drill along the flute groove of the drill, and the inner wall surface of the oil hole is enriched with metal containing Co as a main component. The layer is formed, and the Co content of the metal-enriched layer is 1.5 times or more the average Co content of the WC-based cemented carbide, and the average thickness of the metal-enriched layer is 0.5 μm or more. A cemented carbide drill with a spiral oil hole, characterized by a diameter of 0.0 μm or less. The cemented carbide drill with a spiral oil hole according to claim 1, wherein the cutting edge diameter of the drill tip of the drill is less than 3 mm. The cemented carbide drill with a spiral oil hole according to claim 1 or 2, wherein at least the surface of the tip of the drill is coated with a hard coating layer. Drill made. The hard coating layer is one or more layers selected from TiN layer, TiAlN layer, TiAlSiN layer, TiSiN layer, TiAlCN layer, TiAlCrN layer, AlCrN layer, AlCrSiN layer and CrN layer. The hard alloy drill with a surface-coated spiral oil hole according to 3.