JP5393004B2 - Cemented carbide small diameter rod and cutting tool and miniature drill - Google Patents

Description

The present invention relates to a small-diameter rod-shaped body and a cutting tool and miniature drill steel cemented carbide, in particular, end mill, diameter drills relates to a cutting tool or miniature drill such a small diameter punch.

  Tungsten carbide (WC) / cobalt (Co) cemented carbide is used for metal cutting and printed circuit board processing because of its excellent wear resistance, high temperature strength and high elastic modulus. Cemented carbides mainly composed of WC particles, with addition of so-called β phase (β metal carbide) such as titanium, niobium, zirconium, chromium, vanadium, and tantalum, and cobalt as a binder phase are widely used. Yes.

In the above WC / Co cemented carbide, mechanical properties are affected by the amount of Co phase as a binding metal, the size of WC particles, and the distance between WC particles. The finer the WC particles, the greater the mechanical properties, especially the strength. Accordingly, when manufacturing a WC / Co-based cemented carbide, vanadium carbide (VC), chromium carbide (Cr ₃ C ₂ ), tantalum carbide (TaC), and niobium carbide (NbC) are used to suppress particle growth. At least one kind is added as a particle growth inhibitor.

On the other hand, in the WC / Co-based cemented carbide, the amount of carbon in the alloy is a factor that greatly affects the characteristics of the entire alloy, and therefore fine control is performed in production. Generally, this amount of carbon is added in an amount that results in a stoichiometric composition as a carbide of each metal element. When the amount of carbon is large, free carbon precipitates in the alloy, and conversely, when the amount of carbon is small. Is precipitated from cobalt tungsten carbide, Co ₃ W ₃ C, Co ₆ W ₆ C, Co ₂ W ₄ C, and Co ₃ W ₉ C ₄ (hereinafter sometimes collectively referred to as η phase). To do. In general, so-called healthy alloys that do not contain free carbon or η phase as described above are generally used in view of the characteristics of the alloys. This is because free carbon and the η phase are likely to be the origin of fracture and have been considered to reduce the cutting characteristics of cemented carbide.

On the other hand, cemented carbide has been proposed in which the precipitation of Co ₃ W ₃ C is actively promoted, thereby improving the wear resistance when cutting difficult-to-cut materials such as stainless steel ( For example, see Patent Document 1). In addition, a cemented carbide having improved wear resistance and fracture resistance by precipitating and dispersing a small amount of η phase has been proposed (for example, see Patent Document 2).

As cemented carbide materials for miniature drills, those described in Patent Documents 3 and 4 are known.
Japanese Examined Patent Publication No. 63-27421 JP-A-6-65671 JP-A-5-117799 JP 2004-190118 A

  However, the cemented carbide described in Patent Document 1 has a problem that the strength is small although the hardness is high because the ratio of the η phase having high hardness and low strength is large.

  Moreover, although the cemented carbide described in Patent Document 2 improves the hardness and improves the wear resistance by precipitating a small amount of η phase, there is a problem that the strength is about 30% lower than that of a healthy alloy. there were. This is probably because the cemented carbide described in Patent Document 2 has a small amount of η phase, but the strength of the WC particles is reduced due to the large particle size of the WC particles.

  Further, the cemented carbides described in Patent Documents 1 and 2 cannot be used as they are for a very small diameter drill for processing a printed circuit board or the like because the WC particles have a large particle size.

  Furthermore, as shown in Patent Documents 3 and 4, in recent years, miniature drills have been developed, and miniature drills have been reduced in diameter. In recent years, the diameter has been reduced to 300 μm or less, and further to 100 μm or less. Accordingly, the WC particles of cemented carbide for miniature drills are also becoming fine particles of 0.5 μm or less, and further 0.3 μm or less. In order to improve the hardness and strength of such a miniature drill, it is conceivable to disperse and precipitate a small amount of η phase. However, as WC particles are atomized, there are η phase particles exceeding the WC particle size. Thus, there is a problem that the miniature drill is easily broken starting from η phase particles having low strength.

  That is, when the WC particles are large, even though the η phase particles are present, the η phase particles are not much larger than the WC particles, and thus the characteristics of the miniature drill are not so much affected. When the diameter of miniature drills progresses and WC particles become as fine as 0.3 μm or less, η phase particles exceeding the particle size of WC particles exist, and η phase particles with low strength are the starting point. There was a problem that the miniature drill was easily broken.

The present invention has a high strength and high hardness, and an object thereof to provide a super hard alloy small diameter rod-shaped body and a cutting tool and miniature drill Ru can be suppressed breakage.

As a result of studying the above problems, the present inventors have satisfied 0 <I ₁ / I ₂ ≦ 0.05, and the average particle diameter of WC in the WC-Co cemented carbide is 0.2 3 μm. It follows and, surrounding the cobalt tungsten carbide particles and around it in coarse particles, substantially allowed plurality of coarse particles consisting of coarse WC particles binder phase is not present, between the crude large particles, than the average particle size by also made present and a binding phase with a plurality of fine WC grain diameter is small, has excellent mechanical strength and high hardness, and that carbide alloy small diameter rod-shaped body Ru can suppress breakage is obtained As a result, the present invention has been achieved.

That is, carbide alloy small diameter rod-shaped body of the present invention, the WC particles as hard phase comprises Co respectively as binder phase, and _{Co 3 W 3 C, Co 6} W 6 C, Co 2 W 4 C and Co ₃ by weight of at least one cobalt tungsten carbide particles you containing carbide alloy small diameter rod-shaped body selected from W ₉ C, the _Co 3 _{W 3} C in X-ray diffractometry using Cukα line (333) (511) synthetic peak, Co ₆ W ₆ C (333) and (511) synthetic peak, Co ₂ W ₄ C (333) and (511) synthetic peak, and Co ₃ W ₉ C Of the peaks of (301), when the maximum peak intensity is I ₁ and the peak intensity of (001) of WC is I ₂ , 0 <I ₁ / I ₂ ≦ 0.05 is satisfied and after sintering WC grains in The average particle size of the child is not more than 0.23 .mu.m, and the WC particles, the average particle size of coarse WC particle diameter is larger than consists with the average particle size diameter than smaller fine WC particles the average particle size of the WC particles is not more 0.2 3 [mu] m or less, further wherein the coarse WC particles surrounds around the cobalt tungsten carbide particles, constitute the coarse particle group is substantially free of binder phase, The fine WC particles are present together with the binder phase between the coarse particle groups.

In such ultra hard alloy small diameter rod-shaped body, _{0 <while} satisfying _I 1 / I ₂ ≦ 0.05, to atomize the average particle size of the WC particles 0.2 3 [mu] m or less, cobalt tungsten carbide particles A plurality of fine WC particles having a particle diameter smaller than the average particle diameter are present between a plurality of coarse particle groups consisting of coarse WC particles substantially surrounded by coarse particles. Therefore, it has high strength and high hardness and can suppress breakage.

That is, by setting the average particle size of the WC particles and 0.2 3 [mu] m or less, mostly can improve the strength of the alloy, also _{0 <to} satisfy _I 1 / I ₂ ≦ 0.05, high hardness η The presence of a small amount of the phase in the binder phase mainly has a function of increasing the hardness of the binder phase, whereby the wear resistance can be improved. Further, a plurality of fine particles having a particle diameter smaller than the average particle diameter are surrounded by a plurality of coarse particle groups consisting of coarse WC particles which are surrounded by coarse particles with cobalt tungsten carbide particles and substantially no binder phase. By allowing the WC particles to exist, the coarse particle group functions as one hard phase particle, and a cemented carbide having large hard phase particles can be formed, and the hardness can be improved. Furthermore, since the coarse particle group functioning as one hard phase particle includes a plurality of fine WC particles having a particle size smaller than the average particle size therebetween, the fine WC particles further increase the hardness. Can be improved. Moreover, there is also an effect that the progress of cracks can be suppressed by the coarse particle group that functions as one hard phase particle.

  Furthermore, even if the cobalt tungsten carbide particles become large to some extent, since the coarse WC particles surround the cobalt tungsten carbide particles, breakage starting from the cobalt tungsten carbide particles can be suppressed. Moreover, since the coarse WC particles surround the cobalt tungsten carbide particles, the detachment of the cobalt tungsten carbide particles can be suppressed and the wear resistance can be improved.

As raw material powders, using a coarse WC powder, it is possible to produce a large cemented carbide products, unless cemented carbide satisfies the configuration of the present invention, it is difficult to produce a small-diameter rod-shaped body . In the present invention, using a fine WC powder, by which though having a single coarse particle group serving as a hard phase particles, can produce a small-diameter rod-shaped body, to that prepared products with large particles Similar effects can be obtained.

Cutting tool of the present invention is characterized by having upper Symbol cemented alloy small diameter rod-shaped body. Thereby, the cutting tool which is excellent in intensity | strength and hardness, and can suppress breakage can be obtained.

Miniature drill of the present invention is characterized by having upper Symbol cemented alloy small diameter rod-shaped body. Thereby, the miniature drill which is excellent in strength and hardness and can suppress breakage can be obtained.

In cemented carbide made small rod-shaped body of the present invention, the average particle size of WC particles With 0.2 3 [mu] m or less, can mainly improve the strength of the alloy, _{also, 0 <I 1 / I 2} ≦ 0 .05 is satisfied, and a high hardness η phase is present in a small amount in the binder phase, thereby mainly having a function of increasing the hardness of the binder phase, thereby improving the wear resistance. Further, a plurality of fine WC particles having a particle size smaller than the average particle size are surrounded by a plurality of coarse particle groups consisting of cobalt tungsten carbide particles and coarse particles surrounding the cobalt tungsten carbide particles and substantially no binder phase. by made present the particles, functions as a coarse particle group as if one of the hard phase particles, it is possible to configure the cemented carbide with greater hard phase particles, can be improved hardness. Further, since the coarse particle group functioning as one hard phase particle includes a fine particle group composed of a plurality of fine WC particles having a particle diameter smaller than the average particle diameter , the fine particle group. Thus, the hardness can be further improved.

  Furthermore, even if the cobalt tungsten carbide particles become large to some extent, since the coarse WC particles surround the cobalt tungsten carbide particles, breakage starting from the cobalt tungsten carbide particles can be suppressed.

Such cemented carbide made small rod-shaped body of the cutting tool, by using a miniature drill, excellent strength and hardness, breakage can be suppressed, it is possible to improve the cutting performance, as well as the cutting tool can achieve long life, for example, printing A miniature drill excellent in wiring board processing can be obtained.

The present invention is described in detail below. As shown in FIG. 1, the cemented carbide small-diameter rod-shaped body of the present invention is composed of a hard phase 3 and a binder phase 5, the hard phase 3 is made of WC, and the binder phase 5 is mainly composed of Co. Therefore, Co is contained in a total amount of 5 to 15% by mass.

Further, in terms of strengthening the binder phase 5, vanadium contained in the cemented carbide is 0.1 to 1.5% by mass in terms of carbide (VC), and chromium is 0.1 in terms of carbide (Cr ₃ C ₂ ). It is desirable to contain 1 to 2.5 mass%.

  These vanadium (V) and chromium (Cr) function as an intermediate at the interface between WC and Co, and have an effect of strengthening the bond between WC and Co. Vanadium and chromium also have a function as a grain growth inhibitor for WC and Co. These grain growth inhibitors are dissolved in Co in the binder phase 5.

FIG. 1 is a scanning electron microscope (SEM) photograph of 30000 times the cross section of a small-diameter rod-shaped body made of cemented carbide. The average particle size of the WC particles is hard phase is a 0.2 3 [mu] m or less, particularly from the viewpoint of strengthening is desirably 0.2μm or less. The average particle diameter of the WC particles is preferably 0.1 μm or more from the viewpoint that the raw material powder can be mixed. The WC particles have a triangular prism shape, and look like a triangle or a square depending on the viewing angle. The average particle diameter of such WC particles is calculated by measuring the area occupied by the WC particles in a scanning electron microscope (SEM) photograph, calculating the average value, and converting to the diameter when the WC particles are assumed to be spherical, An average particle size can be obtained. The area occupied by the WC particles can be measured by, for example, image software (Nippon Roper: ImagePro Plus).

The super hard alloy small diameter rod-shaped body of the present invention, as shown in FIG. 1, the above hard phase 3, it is a significant feature that there is η phase 7 in addition to binding phase 5. The η phase 7 includes cobalt tungsten carbide selected from Co ₃ W ₃ C, Co ₆ W ₆ C, Co ₂ W ₄ C, and Co ₃ W ₉ C. The maximum peaks in the X-ray diffraction pattern (Cuk α-ray) of these η phases 7 are the combined peaks of (333) and (511) of Co ₃ W ₃ C, and (333) and (511) of Co ₆ W ₆ C. The synthesis peak, the synthesis peak of (333) and (511) of Co ₂ W ₄ C, and the peak of (301) of Co ₃ W ₉ C, according to the present invention, when the largest peak height intensity of WC is the largest peak of the _I 1, WC peak height of (001) was _{I 2,} the peak intensity ratio represented by I 1 / _{I 2} is greater than 0, 0.05 or less. FIG. 2 shows an X-ray diffraction pattern. In FIG. 2, η-phase peaks appear in the vicinity of 2θ = 40 ° and 42.5 °, and I ₁ / I _{2 in} this case is 0.03.

The reason why the peak intensity ratio I ₁ / I _{2 is set} to 0 <I ₁ / I ₂ ≦ 0.05 is that the hardness of the binder phase can be mainly increased by making a small amount of η phase present in the alloy. . On the other hand, when this strength ratio is 0, there is no precipitation of η phase in the alloy, and the hardness of the alloy cannot be increased due to the increased hardness of the binder phase, and the wear resistance decreases and the tool wear increases. In addition, since the bond between the hard phase and the binder phase becomes weak, the bending strength is lowered. On the other hand, when I ₁ / I ₂ exceeds 0.05, the bending strength is reduced due to excessive η phase precipitation. From the viewpoint of improving the bending strength, I ₁ / I ₂ is desirably 0.005 to 0.02.

Note that the synthetic peak of _Co 3 _{W 3} C and (333) (511), the X-ray diffractometry using Cukα line, 2 [Theta] = 42.5 near °, the _Co 6 _{W 6} C and (333) About the synthetic peak of (511), about 2θ = 43 °, about the synthetic peak of (333) and (511) of Co ₂ W ₄ C, about 2θ = 42 °, about the peak of (301) of Co ₃ W ₉ C Occurs near 2θ = 41 °.

In the present invention, enclose taken as η phase particles 7 around its at coarse WC particles 3a, substantially binder phase multiple nonexistent coarse particles 9 are present, between the crude large particles 9, coarse There are a plurality of minute WC particles 3b having a particle diameter smaller than that of the WC particles 3a. The binder phase 5 exists between the minute WC particles 3b. In other words, the coarse particle group 9 including the η phase particles 7 and the coarse WC particles 3a surrounding the η phase particles 7 exists in the structure in which the fine WC particles 3b exist.

a plurality of coarse WC particles 3a of η phase particles 7 that surrounds around it is turned into integrally joined, also the binding of η phase grains 7 coarse WC particles 3a are firm, though one hard Functions as phase particles. In the coarse particle group 9, the binder phase 5 is not substantially present, and if any, it is very little.

  The WC particles are composed of coarse WC particles 3a and fine WC particles 3b, and the average particle diameter of the WC particles is the average particle diameter of these coarse WC particles 3a and fine WC particles 3b. Such an average particle size can be obtained by image analysis of a 30000 times photograph of a scanning electron microscope (SEM). In addition, a plurality of coarse particle groups 9 can be usually confirmed in one SEM photograph of 30000 times.

In producing the ultra-hard alloy small diameter rod-shaped body of the present invention, WC powder fine as the raw material, Co powder, and VC powder and Cr ₃ C ₂ powder as grain growth inhibitors, for carbon content adjustment, carbon Black (C) is used. As the grain growth inhibitors may be used either VC powder or Cr ₃ C ₂ powder. Here, WC powder and Co powder are WC-Co composites produced by dissolving water-soluble salt of W and Co in water, drying, heat treatment and carbonization for atomization of WC and uniform dispersion of Co. It is desirable to use a powder.

Also, the VC powder and / or Cr ₃ C ₂ powder, using two types of raw material powders of coarse powder and fine powder as described later. The oxygen content of the VC powder and the Cr ₃ C ₂ powder is desirably 0.5% by mass or less. For the WC powder, the average particle size is 0. It is desirable that it is less than 2 μm and the oxygen content is 0.2 mass% or less. To reduce the oxygen content, WC powder, VC powder, the Cr ₃ C ₂ powder, and more can be achieved to strongly example carbonization atmosphere during carbonization. The oxygen content can be measured by an infrared absorption method.

  As the grain growth inhibitor, tantalum carbide (TaC) and / or niobium carbide (NbC) can also be used. Also in this case, it is desirable to use two kinds of raw material powders, coarse particles and fine particles, and the oxygen content is 0.5 mass% or less.

The above powder is weighed, wet mixed and pulverized using an organic solvent such as acetone or propanol, dried, molded by a known molding method such as press molding, fired, and then subjected to pressure (HIP ) Firing. As for the organic solvent, acetone or propanol having a low oxygen content is desirable. It is also desirable to minimize the number of wet-mixing pulverizations using an organic solvent and to minimize the time for immersion in the organic solvent. Firing is performed at a vacuum of 10 ⁻¹ to 10 ⁻³ Torr in the firing furnace for 10 minutes to 2 hours in the range of 1300 to 1390 ° C., and subsequently the inside of the firing furnace is set to a pressure of 1 to 10 MPa in an Ar atmosphere. And firing at 1290 to 1380 ° C.

Incidentally, V C, Cr ₃ C ₂ powder was added to the possible firing just before, even mixed and ground by adding an organic solvent, and select the low solvent having OH group, the co-grinding time is short, moreover, VC By reducing the number of times the organic solvent is added to Cr ₃ C ₂ as much as possible, the oxygen content can be reduced.

In this way, the amount of oxygen in the VC powder, Cr ₃ C ₂ powder, and WC powder is reduced, and a solvent having a small amount of OH groups is selected and wet-mixed and pulverized. The amount of η phase can be controlled by the amount of carbon black (C) added.

Further, when the oxygen content of the VC powder or Cr ₃ C ₂ powder is 0.5 mass% or more, coarse η phase particles are precipitated during firing. This is because VC and Cr ₃ C ₂ are more easily oxidized than WC, so that the surface is oxidized by reacting with OH adsorbed on the surface of the raw material during firing, and in the final stage of firing, VC or Cr ₃ C ₂ It is considered that oxygen on the powder surface reacts with surrounding carbon or C of WC to escape as CO, so that the amount of surrounding carbon becomes insufficient and a large η phase is formed.

In particular, in the present invention, two types of raw material powders, coarse powder and fine powder, are used as the VC powder and / or Cr ₃ C ₂ powder. For example, when coarse powder having a particle diameter of 1 μm is used as the VC powder, the coarse powder contains a lot of oxygen, and after molding, for example, around such coarse VC powder, It is in a state where a plurality of WC powders, which are fine powders of about 0.2 μm, are attached, and during firing, V and Cr are dissolved in the binder phase and try to suppress WC grain growth. A large amount of oxygen reacts with the surrounding carbon or WC C to form CO, the carbon amount becomes insufficient, and W and C of WC are dissolved in the binder phase to promote sintering of WC powder. As a result, the coarse WC particles 3a are formed, and the η phase particles 7 composed of Co and WC W and C in the binder phase are formed at the position where the coarse particles of the VC powder existed. A coarse particle group 9 is formed. Furthermore, between the coarse particle groups 9, fine η phase of fine particles of VC powder, Cr ₃ C ₂ powder, and a large number of fine WC having a smaller particle size than the coarse WC particles 3a that did not grow so much. There will be particles 3b.

In the present invention, even if the WC powder is atomized and the grain growth inhibitor such as VC powder and Cr ₃ C ₂ powder is also atomized, the amount of oxygen in these raw material powders is reduced and mixed as described above. By reducing the number of pulverization steps and time, and using a solvent with a low oxygen content, the amount of η phase satisfies 0 <I ₁ / I ₂ ≦ 0.05, depending on the amount of carbon black (C) added. it is possible to reliably control the amount of the average grain size of WC can with 0.2 3 [mu] m or less, moreover, VC powder, a Cr ₃ C ₂ powder, by using a coarse powder in addition to fine powder, eta phase There are a plurality of coarse particle groups 9 composed of the particles 7 and the coarse WC particles 3a surrounding the particles 7, and a plurality of fine WC particles 3b having a particle diameter smaller than the coarse WC particles 3a are present between the coarse particle groups 9. Can form an organization.

Cutting tool of the present invention is made of a top Symbol cemented alloy small diameter rod-shaped body, for example, end mill, diameter drills, high hardness and high strength, such as small-diameter punches, cutting tools breakage resistance is required, particularly It can be suitably used for a miniature drill. In particular, a diameter of 300μm or less, particularly 200μm or less, more in the case of 100μm or less, it becomes easier to breakage, it is possible to use a super hard alloy small diameter rod-shaped body of the present invention suitably. Furthermore, the present invention can be suitably used when the small-diameter rod-like portion (diameter is 300 μm or less) is 1 mm or longer.

A water-soluble tungsten raw material (ammonium tungstate) and a cobalt raw material (cobalt nitrate) were dissolved in a ratio of 500 ml of water to 100 g of the raw material, and dried with a spray dryer. 100 g of the obtained spray-dried powder was subjected to thermal decomposition treatment at 500 ° C. in a nitrogen atmosphere to obtain a WO ₃ —CoO composite oxide powder. These composite oxide powders were carburized at a temperature of 700 to 900 ° C. in a CO / H ₂ atmosphere to obtain WC—Co composite carbide powders (WC 92 mass%, Co 8 mass%). This WC-Co composite carbide powder has a structure in which Co adheres around the WC powder. The average particle diameter of WC is obtained by image analysis of an SEM image and is shown in Table 1.

100 parts by weight of WC-Co composite carbide, 0.15 parts by weight (total 0.3 parts by weight) of two types of VC powder having an average particle diameter of 0.5 μm and 1 μm, and Cr ₃ C ₂ powder having an average particle diameter of 1 μm 0 .6 parts by mass and further adjusting the amount of carbon in the sintered body, after adding a small amount of carbon slurry so that the total amount of carbon in the mixed powder becomes the amount shown in Table 1, Acetone was added as a solvent, and wet mixing was performed in a ball mill for 72 hours. Incidentally, WC powder, VC powder, for _Cr 3 _{C 2} powder, oxygen content, respectively, 0.15% by mass WC powder, 0.4 wt% in VC powder, 0.45% by weight _Cr 3 _{C 2} powder It was.

  The raw material slurry mixed in the ball mill is added with paraffin wax, granulated and dried by spray drying, press-molded, vacuum fired, hot isostatically treated (HIP), and cemented carbide sintered body. Obtained. The rate of temperature rise until vacuum firing was 5 ° C./min, the vacuum firing conditions were time: 1 hour, temperature: 1350 ° C., and the hot isostatic pressure treatment was performed at a temperature of 1340 ° C. and 6 MPa with argon gas.

After polishing the surface of the obtained sintered body, subjected to X-ray diffractometry using Cukα line, the peak height of the peak of the η-phase and the height _{I 1 WC (001) I 2} (2θ = around 48 ° Intensity ratio) was calculated, and the WC grain size in the sintered body and the average grain size of the η phase were evaluated by a 30000 times photograph of a scanning electron microscope (SEM). The evaluation was performed with image analysis software (manufactured by Nippon Roper: ImagePro Plus). Furthermore, the Vickers hardness was evaluated under the condition of a load of 9.8 N, and the bending strength was evaluated by a span of 20 mm and a three-point bending. The sample shape was a cylindrical shape with a diameter of 2 mm and a length of 30 mm.

It was confirmed whether or not it has a structure in which fine WC particles exist between coarse particle groups in an electron micrograph of 30000 times of an arbitrary cross section of the sintered body, and is shown in Table 1. Sample No. Reference numerals 3 , 4 and 9 are reference examples.

  Further, the tip of each sample was processed into a drill shape having a diameter of 0.120 mm and a length of 2.0 mm, and the wear resistance and breakage resistance were evaluated under the following conditions. For wear resistance, hole position accuracy was used as an index. Regarding the hole position accuracy, the value of X + 3σ when 4000 holes were drilled was used as an index, and the feed rate in the substrate thickness direction was 3 m / min. The breakage resistance is shown in Tables 1 and 2 using as an index the maximum feed rate at which the drill breaks when the feed rate in the substrate thickness direction is gradually increased for each hole. Describe the processing conditions.

Drill rotation speed 300krpm
Feeding speed 2-20m / min
Evaluation board Hitachi 679G (0.4mm three-layer) and entry sheet (LE
800 1)

  According to Tables 1 and 2, Sample No. No. 5 has a large WC raw material particle size, so the average particle size of the WC particles is large. Since the WC raw material particle size is about the same as that of the VC powder, a plurality of WC powders are attached around the VC powder. The coarse WC particles are present so as to surround the η phase particles, and the structure in which the fine WC particles are present between the coarse particle groups cannot be obtained, and the Vickers hardness is low and the wear resistance is low. I know it ’s bad.

Sample No. 6 shows that the total amount of carbon is small, and thus the η phase ratio (I ₁ / I ₂ ) is as high as 0.08 and the η phase is excessive, the bending strength is low, and the fracture resistance is poor. . Furthermore, sample no. In No. 10, since the amount of added carbon is set to be large, there is no η phase, but carbon is too much to precipitate free carbon, low Vickers hardness and flexural strength, wear resistance and fracture resistance. I know it ’s bad. Furthermore, sample no. 11 shows that the average particle diameter of the WC particles is large, the Vickers hardness is low, and the wear resistance is poor.

On the other hand, sample no. 1 , 2 , 7 , and 8 , the Vickers hardness is 203 MPa or more, the bending strength is 4140 MPa or more, the hole position accuracy indicating wear resistance is 21 μm or less, and the maximum feed speed indicating breakage resistance is 6.4 m / min or more. It can be seen that these characteristics are exhibited.

Is a SEM photograph of ultra-hard alloy small diameter rod-shaped body of the present invention. It is an X-ray diffraction pattern of the carbide alloy small diameter rod-shaped body of the present invention.

Explanation of symbols

3: Hard phase 3a: Coarse WC particles 3b: Fine WC particles 5: Bond phase 7: η phase particles 9: Coarse particles

Claims (3)

WC particles as a hard phase, Co as a binder phase, and at least one cobalt tungsten carbide particle selected from Co ₃ W ₃ C, Co ₆ W ₆ C, Co ₂ W ₄ C, and Co ₃ W ₉ C a super hard alloy small diameter rod-shaped body you contain, the _Co 3 _{W 3} C in X-ray diffractometry using Cukα line (333) and synthetic peak of the _Co 6 _{W 6} C of (511) The maximum peak intensity of the synthetic peak of (333) and (511), the synthetic peak of (333) and (511) of the Co ₂ W ₄ C, and the peak of (301) of the Co ₃ W ₉ C is I ₁ When the peak intensity of (001) of WC is I ₂ , 0 <I ₁ / I ₂ ≦ 0.05 is satisfied, and the average particle diameter of the WC particles after sintering is 0.23 μm or less. Yes, One the WC particles, the average particle size of coarse WC particle diameter is larger than the particle diameter than the average particle size is made smaller fine WC particles, the coarse WC particles to the La said cobalt tungsten carbide surrounds around the particles, constitute the coarse particles do not exist substantially the binding phase, the fine WC particles cemented steel alloy you being present together with the binder phase between the coarse particles Small diameter rod-shaped body . A cutting tool characterized by comprising the cemented carbide made small rod-shaped body of claim 1, wherein. Miniature drill, comprising the cemented carbide made small rod-shaped body of claim 1, wherein.