TWI748676B - Cemented carbide and cutting tools equipped with it - Google Patents

Abstract

The cemented carbide of the present invention has a first phase containing a plurality of tungsten carbide particles and a second phase containing cobalt. In the case of tungsten carbide particles with a circle equivalent diameter, the ratio of the number of tungsten carbide particles with a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more. When the histogram on the horizontal axis shows the distribution of the circle-equivalent diameters of tungsten carbide particles, the frequency is the number of tungsten carbide particles, and the grade is the above-mentioned circle-equivalent diameter separated by 0.1 μm in ascending order. In the horizontal axis, The range exceeding 0.3 μm and less than 0.6 μm is defined as the first range, and the range exceeding 0.6 μm and less than 1.0 μm is defined as the second range. The first range and the second range have at least one maximum frequency. The first The ratio of the first maximum frequency in the maximum frequency in the range to the total number of tungsten carbide particles is more than 10%, and the ratio of the second maximum frequency in the maximum frequency in the second range to the total number of tungsten carbide particles is More than 10%.

Description

Cemented carbide and cutting tools equipped with it

The present invention relates to a super hard alloy and a cutting tool provided with it.

Among the openings of printed circuit boards, small-diameter openings below ϕ1 mm have become the mainstream. Therefore, as a cemented carbide used in tools such as small-diameter drills, a so-called fine-grained cemented carbide in which the hard phase contains tungsten carbide particles with an average particle diameter of 1 μm or less is used (for example, Japanese Patent Laid-Open No. 2007-92090 (Patent Document) 1), Japanese Patent Laid-Open No. 2012-52237 (Patent Document 2), and Japanese Patent Laid-Open No. 2012-117100 (Patent Document 3)). [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2007-92090 [Patent Document 2] Japanese Patent Laid-Open No. 2012-52237 [Patent Document 3] Japanese Patent Laid-Open No. 2012-117100

The cemented carbide of the present invention has a first phase containing a plurality of tungsten carbide particles and a second phase containing cobalt, and When calculating the circle equivalent diameter of each of the tungsten carbide particles by performing image processing on the image of the cemented carbide taken with a scanning electron microscope, the circle equivalent diameter is 0.3 μm or more and 1.0 μm or less The ratio of the number of tungsten carbide particles mentioned above is more than 50%, When the distribution of the circle-equivalent diameter of the tungsten carbide particles mentioned above is represented by a histogram with frequency as the vertical axis and grade as the horizontal axis, The above frequency is the number of the above tungsten carbide particles, The above grades are separated by the equivalent diameters of the above circles in ascending order at intervals of 0.1 μm, In the above horizontal axis, the range exceeding 0.3 μm and less than 0.6 μm is defined as the first range, and the range exceeding 0.6 μm and less than 1.0 μm is defined as the second range. The first range and the second range each have at least one maximum frequency, The ratio of the largest first maximum frequency among the maximum frequencies existing in the first range to the total number of tungsten carbide particles is 10% or more, The ratio of the largest second maximum frequency among the maximum frequencies existing in the second range to the total number of tungsten carbide particles is 10% or more.

The cutting tool of the present invention is provided with a cutting edge containing the above-mentioned cemented carbide.

[Problems to be solved by the present invention] In recent years, with the expansion of 5G (fifth generation mobile communication system), high-capacity information has been further developed. Therefore, the printed circuit board is required to have better heat resistance. In order to improve the heat resistance of the printed circuit board, technology has been developed to improve the heat resistance of the resin or glass filler constituting the printed circuit board. On the other hand, the degree of difficulty of the printed circuit board becomes greater.

Therefore, the object of the present invention is to provide a cemented carbide and a cutting tool provided with the cemented carbide. When the cemented carbide is used as a tool material, especially in the microfabrication of printed circuit boards, the life of the tool can be extended.

[Effects of the invention] When the cemented carbide of the present invention is used as a tool material, especially in the microfabrication of printed circuit boards, it can also extend the life of the tool.

[Description of the embodiment of the present invention] First, the embodiments of the present invention will be described. (1) The cemented carbide of the present invention has a first phase containing a plurality of tungsten carbide particles and a second phase containing cobalt, and When calculating the circle equivalent diameter of each of the tungsten carbide particles by performing image processing on the image of the cemented carbide taken with a scanning electron microscope, the circle equivalent diameter is 0.3 μm or more and 1.0 μm or less The ratio of the number of tungsten carbide particles mentioned above is more than 50%, When the distribution of the circle-equivalent diameter of the tungsten carbide particles mentioned above is represented by a histogram with frequency as the vertical axis and grade as the horizontal axis, The above frequency is the number of the above tungsten carbide particles, The above grades are separated by the equivalent diameters of the above circles in ascending order at intervals of 0.1 μm, In the above horizontal axis, the range exceeding 0.3 μm and less than 0.6 μm is defined as the first range, and the range exceeding 0.6 μm and less than 1.0 μm is defined as the second range. The first range and the second range each have at least one maximum frequency, The ratio of the largest first maximum frequency among the maximum frequencies existing in the first range to the total number of tungsten carbide particles is 10% or more, The ratio of the largest second maximum frequency among the maximum frequencies existing in the second range to the total number of tungsten carbide particles is 10% or more.

When the cemented carbide of the present invention is used as a tool material, especially in the microfabrication of printed circuit boards, it can also extend the life of the tool.

(2) The above-mentioned cemented carbide preferably contains 75 area% or more and less than 100 area% of the first phase in an image taken by a scanning electron microscope, and includes more than 0 volume% and 20 area% The second phase mentioned below. As a result, the tool life is further extended.

(3) The above-mentioned cemented carbide preferably includes 5 area% or more and 12 area% or less of the second phase in an image taken with a scanning electron microscope. As a result, the tool life is further extended.

(4) The above-mentioned cemented carbide preferably contains chromium, and The ratio of the chromium to the mass standard of the cobalt is 5% or more and 10% or less. As a result, the damage resistance of the cemented carbide is improved, and the tool life is further extended.

(5) When the cemented carbide contains vanadium, the content of vanadium in the cemented carbide is preferably less than 100 ppm on a mass basis. As a result, the strength of the cemented carbide is improved.

(6) The ratio of the number of tungsten carbide particles whose circle equivalent diameter is less than 0.3 μm is preferably 7% or less. As a result, the tool life is further extended.

(7) The ratio of the second maximum frequency to the first maximum frequency is preferably 0.8 or more and 1.2 or less. As a result, the tool life is further extended.

(8) When the above horizontal axis defines the range exceeding 0.4 μm and less than 0.6 μm as the third range and the range exceeding 0.6 μm and less than 0.8 μm as the fourth range, Preferably, the third range has the first maximum frequency, and The above-mentioned fourth range has the above-mentioned second maximum frequency. As a result, the tool life is further extended.

(9) The cutting tool of the present invention is provided with a cutting edge containing the above-mentioned cemented carbide. The cutting tool of the present invention has a longer tool life.

(10) The cutting tool is preferably a rotating tool for processing a printed circuit board. The cutting tool of the present invention is suitable for the micro processing of printed circuit boards.

[Details of the embodiment of the present invention] Hereinafter, specific examples of the cemented carbide and cutting tool of the present invention will be described with reference to the drawings. In the drawings of the present invention, the same reference signs indicate the same part or a corresponding part. In addition, in order to make the drawings clear and simple, the dimensional relationships such as length, width, thickness, and depth have been appropriately changed, and they do not necessarily represent the actual dimensional relationships.

In this specification, when the form of "A～B" is described in the absence of a special definition, it means the upper and lower limits of the range (that is, above A and below B). When only B describes the unit but A does not describe the unit, The unit of A is the same as the unit of B.

In this specification, when a compound or the like is represented by a chemical formula, if the atomic ratio is not particularly limited, it is deemed to include all previously known atomic ratios, and it is not necessarily limited to the atomic ratio within the stoichiometric range. For example, in the case of "WC", the ratio of the number of atoms constituting WC includes all previously known atomic ratios.

In order to obtain a cemented carbide that can extend the life of the tool, the inventors studied the damage pattern of the tool when a tool containing the previous particulate cemented carbide is used to microfabricate a printed circuit board, and the result is as follows opinion.

Use glass epoxy substrates made by weaving glass fibers into cloth and impregnated with epoxy resin, or glass polyimide substrates made by impregnating glass fabrics with polyimide resin as printing The substrate used in the circuit substrate.

The printed circuit board was micro-processed with a tool containing the previous particulate cemented carbide. As a result, it was confirmed that the cobalt, which is the bonding phase of the cemented carbide, was locally worn due to the resin or glass fiber in the printed circuit board. Tungsten carbide particles (below Also recorded as "WC particles") exposed, causing the WC particles to fall off.

Therefore, the inventors of the present invention speculate that in order to achieve a longer tool life, it is important to reduce the amount of cobalt (Co) exposed on the surface of the tool during processing and to increase the bonding force of the WC particles with each other. In addition, based on the fact that the WC particles in the cemented carbide directly participate in the cutting of the printed circuit board, the inventors speculate that it is also important for the WC particles to continuously and densely appear on the surface of the tool in order to maintain the precision of the microfabrication.

In order to reduce the interface between WC with Co and reduce the amount of cobalt exposed on the surface of the tool during processing, it is considered to increase the particle size of the WC particles in the cemented carbide and reduce the amount of cobalt. However, if the particle size of the WC particles is increased and the amount of cobalt is reduced, the strength is likely to decrease, and damage is likely to occur during processing.

Based on the above insights, the inventors conducted intensive research, and as a result, they newly discovered that by controlling the particle size of the WC particles, the binding force between the WC particles can be increased, thereby completing the cemented carbide of the present invention. The details of the cemented carbide of the present invention and the cutting tool provided with it are described below.

[Embodiment 1: Cemented carbide] The cemented carbide of the present invention has a first phase containing a plurality of tungsten carbide particles and a second phase containing cobalt, and In the case of calculating the circle equivalent diameter of each tungsten carbide particle by image processing on the image of the cemented carbide taken with a scanning electron microscope, the circle equivalent diameter of tungsten carbide particles is 0.3 μm or more and 1.0 μm or less The ratio of the number basis is more than 50%. When the bar graph with frequency as the vertical axis and grade as the horizontal axis shows the distribution of the circle-equivalent diameter of tungsten carbide particles, the frequency is the number of tungsten carbide particles. The number, the grade is the above-mentioned circle equivalent diameter divided by 0.1 μm in ascending order. In the horizontal axis, the range exceeding 0.3 μm and less than 0.6 μm is defined as the first range, and the range exceeding 0.6 μm and less than 1.0 μm is defined as the first range. The range is defined as the second range. The first range and the second range each have at least one maximum frequency. The ratio of the largest first maximum frequency to the total number of tungsten carbide particles in the first range is 10% or more. 2 The ratio of the largest second largest frequency among the largest frequencies present in the range to the total number of tungsten carbide particles is more than 10%.

When the cemented carbide of the present invention is used as a tool material, especially in the microfabrication of printed circuit boards, it can also extend the life of the tool. The reason is not clear, but it can be inferred as follows (i) and (ii).

(i) In the cemented carbide of the present invention, the ratio of the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more. As a result, the structure of the cemented carbide becomes homogeneous, which can prevent the precision of micro-machining from decreasing with use, thereby prolonging the life of the tool.

(ii) In the cemented carbide of the present invention, the circle-equivalent diameter of the WC particles is distributed in the range where the particle size exceeds 0.3 μm and is 0.6 μm or less (the first range) and the range where the particle size exceeds 0.6 μm and is 1.0 μm or less (the first range) 2) each has at least one maximum frequency. The ratio of the largest maximum frequency in the first range (first maximum frequency) and the largest maximum frequency in the second range (second maximum frequency) to the total number of tungsten carbide particles in the cemented carbide is 10% or more.

As a result, the cemented carbide has a structure in which the WC particles with a larger circle equivalent diameter become a skeleton, and the WC particles with a smaller circle equivalent diameter fill the gaps between the WC particles. Since the WC particles in the cemented carbide are bonded to each other, the shedding of the WC particles is suppressed, thereby improving the wear resistance. Furthermore, by suppressing abrasion, the increase in cutting resistance is suppressed, and the breakage resistance is improved. Therefore, the tool life becomes longer.

Furthermore, in this cemented carbide, the amount of cobalt exposed on the surface of the tool during processing is lower than that of the previous particulate cemented carbide. Therefore, cobalt abrasion is less likely to occur during processing, and WC particles can be prevented from falling off, thereby prolonging the tool life.

＜Phase 1＞ (Composition of Phase 1) The first phase contains tungsten carbide particles. Here, tungsten carbide not only includes "pure WC (which does not contain any impurity elements, and also includes WC whose impurity elements do not reach the detection limit)", but also includes "within the scope of not impairing the effects of the present invention. Deliberately or inevitably, WC containing other impurity elements". The concentration of impurities contained in tungsten carbide (when there are two or more elements constituting the impurities, the total concentration of the same) is less than 0.1% by mass relative to the total amount of the tungsten carbide and the impurities. The content of impurity elements in the first phase was measured by ICP (Inductively Coupled Plasma) emission spectroscopy (measurement device: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).

(Distribution of circle equivalent diameter of tungsten carbide particles) Among tungsten carbide particles, the ratio of tungsten carbide particles with a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less based on the number of tungsten carbide particles is 50% or more. As a result, the structure of the cemented carbide becomes homogeneous, which can prevent the precision of micro-machining from decreasing with use, thereby prolonging the life of the tool.

When the amount of cobalt in the cemented carbide is constant, if the ratio of coarse-grained tungsten carbide particles with a circle equivalent diameter of more than 1 μm increases, the hardness will decrease and the wear resistance tends to decrease. If the circle equivalent diameter does not reach 0.3 μm As the ratio of fine tungsten carbide particles increases, the shedding of tungsten carbide particles becomes serious and the wear resistance tends to decrease. In the cemented carbide of the present invention, the ratio of the number of tungsten carbide particles with a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more, so it can have excellent wear resistance.

From the viewpoint of improving the homogeneity of the cemented carbide structure, the ratio of the number of tungsten carbide particles with a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more, preferably 70% or more. The upper limit of the number-based ratio of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is not particularly limited. For example, it may be 100% or less, 90% or less, or 80% or less. The ratio of the number of tungsten carbide particles whose circle equivalent diameter is 0.3 μm or more and 1.0 μm or less can be set to 50% or more and 100% or less, 60% or more and 90% or less, and 70% or more and 80% or less.

The ratio of tungsten carbide particles whose circle equivalent diameter is less than 0.3 μm is preferably 7% or less. Tungsten carbide particles with a circle equivalent diameter of less than 0.3 μm have little effect on increasing the strength of the cemented carbide or reducing the amount of cobalt exposed on the surface of the tool during processing. Therefore, by reducing the ratio of the number of tungsten carbide particles whose circle equivalent diameter is less than 0.3 μm, the tool life becomes longer.

The ratio of tungsten carbide particles whose circle equivalent diameter is less than 0.3 μm is preferably 0% or more and 7% or less, and more preferably 0% or more and 5% or less. In addition, the ratio of the number of tungsten carbide particles whose circle equivalent diameter is less than 0.2 μm is preferably from 0% to 3%.

Measure the circle equivalent diameter of tungsten carbide particles according to the following steps (A1) to (C1). (A1) Mirror processing any surface or any cross section of the cemented carbide. As a method of mirror surface processing, for example, a method using diamond paste for polishing, a method using a focused ion beam device (FIB device), a method using a cross-section polisher device (CP device), and a combination of these methods Methods etc.

(B1) Use a scanning electron microscope to photograph the processed surface of the cemented carbide. The observation magnification is set to 5000 times. An example of an image of the cemented carbide of the present invention taken by a scanning electron microscope is shown in FIG. 1. In the scale at the bottom right of Figure 1, 1 scale means 1 μm.

(C1) Input the captured image obtained in (B1) above into the computer, and use the image analysis software (ImageJ: https://imagej.nih.gov/ij/) for image processing to calculate the tungsten carbide particles Circle equivalent diameter (Heywood diameter: equal area circle diameter). The first phase containing tungsten carbide particles and the second phase containing cobalt can be identified by the color shade in the above-mentioned captured image. The image obtained by performing image processing on the captured image of FIG. 1 is shown in FIG. 2. In Figure 2, the black area is the first phase, and the white area is the second phase. The white line represents the grain boundary. In the scale at the bottom right of Figure 2, 1 scale means 1 μm.

In this manual, the following steps (D1) and (E1) are used to calculate the ratio based on the number of tungsten carbide particles with a circle equivalent diameter of 0.3 μm to 1.0 μm in cemented carbide. (D1) Perform the above-mentioned (C1) image processing in three measurement fields of view. The size of a measurement field is a rectangle with a length of 25.3 μm × a width of 17.6 μm.

(E1) Calculate the ratio of tungsten carbide particles with a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less to the number basis of all tungsten carbide particles in the measurement field in the three measurement fields. The average value of these is regarded as the ratio based on the number of tungsten carbide particles with a circle-equivalent diameter of 0.3 μm or more and 1.0 μm or less in the cemented carbide.

According to the measurement performed by the applicant, when it is confirmed that the measurement is performed on the same sample, even if the selected position of the measurement field is changed and the circle equivalent diameter in the cemented carbide is measured multiple times, the tungsten carbide whose diameter is 0.3 μm or more and 1.0 μm or less Based on the ratio of the number of particles, the deviation of the measurement result is also less. Even if the measurement field of view is set arbitrarily, the result will not become random.

The distribution of the circle-equivalent diameter of the tungsten carbide particles contained in the cemented carbide of the present invention satisfies the following (a). Furthermore, when the distribution of the circle-equivalent diameter of the tungsten carbide particles contained in the cemented carbide of the present invention is represented by a histogram with frequency on the vertical axis and grade on the horizontal axis, the following (b) and (c). Here, the frequency is the number of tungsten carbide particles, and the grade is the above-mentioned circle equivalent diameter separated by 0.1 μm in ascending order.

(a) The ratio of tungsten carbide particles with a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more.

(b) When the range exceeding 0.3 μm and less than 0.6 μm is defined as the first range on the horizontal axis, and the range exceeding 0.6 μm and less than 1.0 μm is defined as the second range, the first range and the second range The 2 ranges each have at least one maximum frequency.

(c) The ratio of the largest first largest frequency in the first range to the total number of tungsten carbide particles is 10% or more, and the largest second largest frequency in the second range is relative to tungsten carbide The ratio of the total number of particles is more than 10%.

In this manual, follow the steps (A2) and (B2) below to make a histogram.

(A2) Calculate the circle-equivalent diameter of tungsten carbide particles according to the steps (A1) to (C1) described in the above-mentioned method for measuring the circle-equivalent diameter of tungsten carbide particles. The circle equivalent diameter of tungsten carbide particles was measured in three measurement fields.

(B2) Based on the circle-equivalent diameters of all tungsten carbide particles measured in the three measurement fields, a histogram with frequency as the vertical axis and grade as the horizontal axis is created. The frequency is the number of tungsten carbide particles, and the grade is the circle equivalent diameter separated by 0.1 μm in ascending order.

In this specification, the maximum frequency means that the frequency is greater than the level one below the level of the frequency (the side with the smaller diameter of the circle), and the level above the level (the side with the larger the circle is the larger diameter) above the level to which the frequency belongs Any one of the frequency.

Furthermore, the level below the level to which the extreme frequency belongs and the level above the level to which the extreme frequency belongs can also be a level outside the first range or outside the second range. Specifically, when the class to which the maximum frequency in the first range belongs is more than 0.3 μm and less than 0.4 μm, the next class is more than 0.2 μm and less than 0.3 μm, which is outside the first range. When the maximum frequency in the second range belongs to a level exceeding 0.9 μm and less than 1.0 μm, the previous level is more than 1.0 μm and less than 1.1 μm, which is outside the second range.

By satisfying the above (a) to (c), the precision of microfabrication can be suppressed from decreasing with use, the strength and breakage resistance can be improved, the falling of WC particles can be suppressed, and the tool life can be prolonged.

The above (a) to (c) will be described with reference to Figs. 3 to 6. FIGS. 3 to 6 are respectively an example of a diagram showing the distribution of the circle-equivalent diameter of tungsten carbide particles in the cemented carbide of the present invention. In Figures 3 to 6, the horizontal axis represents the grades divided by the circle equivalent diameters in ascending order at intervals of 0.1 μm, and the vertical axis represents the ratio (%) of tungsten particles belonging to each grade to the number basis of all tungsten particles.

In FIGS. 3 to 6, the description of the form of "C to D" means that it exceeds C and is less than D. Specifically, the description of "0 to 0.1" on the horizontal axis of FIGS. 3 to 6 means more than 0 μm and 0.1 μm or less, and the description of "0.1 to 0.2" means more than 0.1 μm and 0.2 μm or less.

The shape of Fig. 3 to Fig. 6 can be regarded as the shape of the histogram when the horizontal axis has the same level and the frequency on the vertical axis is set as the number of tungsten carbide particles. Therefore, the above-mentioned (a) to (c) can be described using the shapes of FIGS. 3 to 6. In Figures 3 to 6, the vertical axis represents the ratio (%) of tungsten particles belonging to each grade to the number basis of all tungsten particles. In the following, for convenience of explanation, the vertical axis of Figures 3 to 6 may be denoted as Frequency.

(image 3) In Figure 3, the ratio of tungsten carbide particles with a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more (about 72%). Therefore, the circle-equivalent diameter distribution of the tungsten carbide particles shown in FIG. 3 satisfies the above (a).

In Figure 3, the frequency of the class with a circle equivalent diameter exceeding 0.4 μm and less than 0.5 μm is greater than the frequency of the class below the class (circle equivalent diameter exceeding 0.3 μm and less than 0.4 μm), and the frequency of the class to which the frequency belongs The frequency of the previous level (the circle equivalent diameter exceeds 0.5 μm and is less than 0.6 μm). That is, in FIG. 3, the first range (the circle equivalent diameter exceeds 0.3 μm and is 0.6 μm or less) has a maximum frequency.

In Figure 3, the frequency of the class with a circle equivalent diameter exceeding 0.7 μm and below 0.8 μm is greater than the frequency of the class below that frequency (the circle equivalent diameter exceeds 0.6 μm and is less than 0.7 μm), and the frequency of the class to which the frequency belongs The frequency of the previous level (the circle equivalent diameter exceeds 0.8 μm and is less than 0.9 μm). That is, in FIG. 3, the second range (the circle equivalent diameter exceeds 0.6 μm and is 1.0 μm or less) has a maximum frequency.

From this, it can be seen that the circle-equivalent diameter distribution of the tungsten carbide particles shown in FIG. 3 satisfies the above (b).

In Fig. 3, the first maximum frequency, which is the largest maximum frequency existing in the first range, is the frequency of the level whose circle equivalent diameter exceeds 0.4 μm and is 0.5 μm or less. The ratio of the first maximum frequency to the total number of tungsten carbide particles is 10% or more (approximately 14.3%).

In Fig. 3, the second maximum frequency, which is the largest maximum frequency existing in the second range, is the frequency at the level where the circle equivalent diameter exceeds 0.7 μm and is below 0.8 μm. The ratio of the second maximum frequency to the total number of tungsten carbide particles is 10% or more (about 12.6%).

From this, it can be seen that the circle-equivalent diameter distribution of the tungsten carbide particles shown in Fig. 3 satisfies the above (c).

(Figure 4) In Figure 4, the ratio of tungsten carbide particles with a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more (approximately 72.1%). Therefore, the circle-equivalent diameter distribution of the tungsten carbide particles shown in FIG. 4 satisfies the above (a).

In Figure 4, the frequency of a class with a circle equivalent diameter exceeding 0.5 μm and below 0.6 μm is greater than the frequency of a class below the class of the frequency (circle equivalent diameter exceeding 0.4 μm and less than 0.5 μm), and the frequency of the class to which the frequency belongs The frequency of the previous level (the circle equivalent diameter exceeds 0.6 μm and is less than 0.7 μm). That is, in FIG. 4, the first range (the circle equivalent diameter exceeds 0.3 μm and is 0.6 μm or less) has a maximum frequency.

In Figure 4, the frequency of the class with a circle equivalent diameter exceeding 0.7 μm and below 0.8 μm is greater than the frequency of the class below the class of the frequency (the circle equivalent diameter exceeds 0.6 μm and is less than 0.7 μm), and the frequency of the class to which the frequency belongs The frequency of the previous level (the circle equivalent diameter exceeds 0.8 μm and is less than 0.9 μm). In addition, in Figure 4, the frequency of a class with a circle equivalent diameter exceeding 0.9 μm and below 1.0 μm is greater than the frequency of a class below the class to which the frequency belongs (circle equivalent diameter exceeding 0.8 μm and less than 0.9 μm), and the frequency to which the frequency belongs The frequency of one level above the level (the equivalent diameter of a circle exceeds 1.0 μm and is less than 1.1 μm). That is, in FIG. 4, the second range (the circle equivalent diameter exceeds 0.6 μm and is 1.0 μm or less) has two maximum frequencies.

From this, it can be seen that the distribution of the circle-equivalent diameter of the tungsten carbide particles shown in Fig. 4 satisfies the above (b).

In Fig. 4, the first maximum frequency, which is the largest maximum frequency existing in the first range, is the frequency at the level where the circle equivalent diameter exceeds 0.5 μm and is less than 0.6 μm. The ratio of the first maximum frequency to the total number of tungsten carbide particles is 10% or more (about 13.4%).

In Fig. 4, the second maximum frequency, which is the largest maximum frequency existing in the second range, is a frequency of a level where the circle equivalent diameter exceeds 0.7 μm and is below 0.8 μm. The ratio of the second maximum frequency to the total number of tungsten carbide particles is 10% or more (about 12.7%).

It can be seen that the distribution of the circle-equivalent diameter of the tungsten carbide particles shown in Fig. 4 satisfies the above (c).

(Figure 5) In Figure 5, the ratio of tungsten carbide particles with a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more (about 73.5%). Therefore, the circle-equivalent diameter distribution of the tungsten carbide particles shown in FIG. 5 satisfies the above (a).

In Figure 5, the frequency of a class with a circle equivalent diameter exceeding 0.3 μm and below 0.4 μm is greater than the frequency of a class below the class of the frequency (circle equivalent diameter exceeding 0.2 μm and less than 0.3 μm), and the frequency of the class to which the frequency belongs The frequency of the previous level (the equivalent diameter of a circle exceeds 0.4 μm and is less than 0.5 μm). That is, in FIG. 5, the first range (the circle equivalent diameter exceeds 0.3 μm and is 0.6 μm or less) has a maximum frequency.

In Figure 5, the frequency of a class with a circle equivalent diameter exceeding 0.7 μm and below 0.8 μm is greater than the frequency of a class below the class to which the frequency belongs (the circle equivalent diameter exceeds 0.6 μm and is less than 0.7 μm), and the frequency of the class to which the frequency belongs The frequency of the previous level (the circle equivalent diameter exceeds 0.8 μm and is less than 0.9 μm). In addition, in Fig. 5, the frequency of a class with a circle equivalent diameter exceeding 0.9 μm and less than 1.0 μm is greater than the frequency of a class below the class to which the frequency belongs (circle equivalent diameter exceeding 0.8 μm and less than 0.9 μm), and the frequency to which the frequency belongs The frequency of one level above the level (the equivalent diameter of a circle exceeds 1.0 μm and is less than 1.1 μm). That is, in FIG. 5, the second range (the circle equivalent diameter exceeds 0.6 μm and is 1.0 μm or less) has two maximum frequencies.

From this, it can be seen that the circle-equivalent diameter distribution of the tungsten carbide particles shown in FIG. 5 satisfies the above (b).

In Fig. 5, the first maximum frequency, which is the largest maximum frequency existing in the first range, is the frequency at the level where the circle equivalent diameter exceeds 0.3 μm and is less than 0.4 μm. The ratio of the first maximum frequency to the total number of tungsten carbide particles is 10% or more (about 11.8%).

In Fig. 5, the second maximum frequency, which is the largest maximum frequency existing in the second range, is the frequency at the level where the circle equivalent diameter exceeds 0.7 μm and is below 0.8 μm. The ratio of the second maximum frequency to the total number of tungsten carbide particles is 10% or more (about 12.2%).

It can be seen that the distribution of the circle-equivalent diameter of the tungsten carbide particles shown in FIG. 5 satisfies the above (c).

(Image 6) In Figure 6, the ratio of tungsten carbide particles with a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more (about 72.6%). Therefore, the circle-equivalent diameter distribution of the tungsten carbide particles shown in FIG. 6 satisfies the above (a).

In Figure 6, the frequency of a class with a circle equivalent diameter exceeding 0.4 μm and less than 0.5 μm is greater than the frequency of a class below the class of the frequency (circle equivalent diameter exceeding 0.3 μm and less than 0.4 μm), and the frequency of the class to which the frequency belongs The frequency of the previous level (the circle equivalent diameter exceeds 0.5 μm and is less than 0.6 μm). That is, in FIG. 6, the first range (the circle equivalent diameter exceeds 0.3 μm and is 0.6 μm or less) has a maximum frequency.

In Figure 6, the frequency of a class with a circle equivalent diameter exceeding 0.6 μm and less than 0.7 μm is greater than the frequency of a class below the class of the frequency (circle equivalent diameter exceeding 0.5 μm and less than 0.6 μm), and the frequency of the class to which the frequency belongs The frequency of the previous level (the circle equivalent diameter exceeds 0.7 μm and is less than 0.8 μm). That is, in FIG. 6, the second range (the circle equivalent diameter exceeds 0.6 μm and is 1.0 μm or less) has a maximum frequency.

From this, it can be seen that the distribution of the circle-equivalent diameter of the tungsten carbide particles shown in FIG. 6 satisfies the above (b).

In Fig. 6, the first maximum frequency, which is the largest maximum frequency existing in the first range, is a frequency of a level whose circle equivalent diameter exceeds 0.4 μm and is 0.5 μm or less. The ratio of the first maximum frequency to the total number of tungsten carbide particles is 10% or more (about 14.2%).

In Fig. 6, the second maximum frequency, which is the largest maximum frequency existing in the second range, is the frequency at the level where the circle equivalent diameter exceeds 0.6 μm and is less than 0.7 μm. The ratio of the second maximum frequency to the total number of tungsten carbide particles is 10% or more (about 12.4%).

From this, it can be seen that the circle-equivalent diameter distribution of the tungsten carbide particles shown in FIG. 6 satisfies the above (c).

In the horizontal axis of the histogram representing the distribution of the circle-equivalent diameter of the tungsten carbide particles of the present invention, the range exceeding 0.4 μm and less than 0.6 μm is defined as the third range, and the range exceeding 0.6 μm and less than 0.8 μm is defined When the range is defined as the fourth range, it is preferable that the third range has the first maximum frequency and the fourth range has the second maximum frequency. As a result, the tool life is further extended.

The ratio of the second maximum frequency to the first maximum frequency is preferably 0.8 or more and 1.2 or less. As a result, the tool life is further extended. It is speculated that the reason is that the combination of tungsten carbide particles is more important in contact with each other. If the difference between the maximum frequency in the first range and the maximum frequency in the second range becomes larger, the result is the tungsten carbide in the cemented carbide The particles have less contact with each other.

＜Phase 2＞ The second phase contains cobalt. The second phase is a bonding phase in which tungsten carbide particles constituting the first phase are bonded to each other.

Here, "the second phase contains cobalt (Co)" means that the main component of the second phase is Co. "The main component of the second phase is Co" means that the mass ratio of cobalt in the second phase is 90% by mass to 100% by mass. The mass ratio of cobalt in the second phase can be measured by ICP emission spectrometry (machine used: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).

In addition to cobalt, the second phase may also contain iron group elements such as nickel, and dissolved substances in alloys (Cr, W, etc.).

＜The composition of cemented carbide＞ (composition) The cemented carbide has a first phase containing a plurality of tungsten carbide particles and a second phase containing cobalt. The cemented carbide preferably includes the first phase with 75 area% or more and less than 100 area% in the image taken by the scanning electron microscope, and the second phase with more than 0 area% and 20 area% or less. .

If the ratio of the second phase in the cemented carbide is 20 area% or less, it is possible to suppress the dissolution of fine tungsten carbide particles with a circle-equivalent diameter of 0.6 μm or less in the cobalt of the second phase, and it can prevent the circle-equivalent diameter from exceeding 0.3 μm and It is the reduction of tungsten carbide particles below 0.6 μm. In addition, the amount of cobalt exposed on the surface of the tool during processing is further reduced. Therefore, the tool life is further extended.

The cemented carbide preferably contains the second phase of 5 area% or more and 12 area% or less in an image taken by a scanning electron microscope. Thereby, the hardness and wear resistance necessary for the processing of the printed circuit board can be exerted, and the deviation of the tool life can be suppressed.

The lower limit of the ratio of the first phase in the cemented carbide can be set to 75 area% or more and 85% area or more. The upper limit of the ratio of the first phase in the cemented carbide can be set to less than 100 area% and 95 area% or less. The ratio of the first phase in the cemented carbide can be set to 75 area% or more and less than 100 area%, and 85 area% or more and 95 area% or less.

The lower limit of the ratio of the second phase in the cemented carbide can be set to be more than 0 area% or more than 5 area%. The upper limit of the ratio of the second phase in the cemented carbide can be set to 20 area% or less and 12 area% or less. The ratio of the second phase in the cemented carbide can be set to exceed 0 area% and be 20 area% or less, 5 area% or more and 12 area% or less.

Measure the area ratio of each of the first phase and the second phase in the cemented carbide according to the following steps (A3) to (C3).

(A3) Follow the same steps as (A1) and (B1) described in the above-mentioned method for measuring the circle-equivalent diameter of tungsten carbide particles to obtain a photographed image of the cross section of the cemented carbide.

(B3) Input the captured image obtained in (A3) above into the computer, and use the image analysis software (ImageJ: https://imagej.nih.gov/ij/) to perform image processing, and the entire measurement field of view ( A rectangle with a length of 25.3 μm × a width of 17.6 μm) was used as the denominator to measure the area ratio of the first phase and the second phase. The first phase and the second phase can be identified by the color shade in the above-mentioned captured image.

(C3) Perform the image processing of (B3) above in five measurement fields. The average value of the area ratio of the first phase obtained in the five measurement fields is taken as the area ratio of the first phase in the cemented carbide. The average value of the area ratio of the second phase obtained in the five measurement fields is taken as the area ratio of the second phase in the cemented carbide.

(Chromium content) The cemented carbide preferably contains chromium (Cr), and the ratio of chromium to cobalt on a mass basis is 5% or more and 10% or less. Chromium has the effect of inhibiting the grain growth of tungsten carbide particles. Furthermore, by solid-dissolving in cobalt, cobalt is promoted to generate lattice strain. Therefore, if the cemented carbide contains chromium in the above-mentioned ratio, the breakage resistance is further improved.

On the other hand, if the amount of chromium is excessive, chromium may precipitate in the form of carbides and become the source of damage. If the ratio of chromium to the mass standard of cobalt is 5% or more and 10% or less, the precipitation of chromium carbides is unlikely to occur, and the effect of improving the damage resistance can be obtained.

In addition, if the ratio of chromium to cobalt is 10% or less on the basis of mass, the degree of the grain growth inhibitory effect becomes moderate, and it is possible to suppress the excessive amount of tungsten carbide particles whose circle equivalent diameter exceeds 1.0 μm in the cemented carbide.

The lower limit of the mass standard ratio of chromium to cobalt is preferably 5% or more, more preferably 7% or more. The ratio of chromium to the mass basis of cobalt is preferably 10% or less, more preferably 9% or less. The quality standard of chromium relative to cobalt can be set at 5% or more and 10% or less, and 7% or more and 9% or less.

The content of cobalt and chromium in the cemented carbide is determined by ICP emission spectrometry.

(vanadium) When the cemented carbide contains vanadium, the content of vanadium on the basis of mass of the cemented carbide is preferably less than 100 ppm.

Because vanadium has a grain growth inhibitory effect, vanadium was used in the manufacture of the previous ultrafine super-hard alloy. It is believed that if vanadium is present when the grains of tungsten carbide particles grow, vanadium will be precipitated on the surface of tungsten carbide particles, or vanadium will be interspersed on the growth surface of tungsten carbide particles in a short period of time, thereby inhibiting the growth of tungsten carbide particles.

Therefore, if vanadium is added, the grain growth inhibitory effect can be obtained. However, since tungsten carbide exists on the interface between tungsten carbide particles and cobalt or the interface between tungsten carbide particles, the wettability or strength tends to decrease. Therefore, the lower the content of vanadium in tungsten carbide, the higher the affinity between tungsten carbide particles and cobalt, or the affinity between tungsten carbide particles, can be maintained higher, thereby increasing the strength of the cemented carbide.

The content of vanadium in the cemented carbide is preferably 100 ppm or less, more preferably 10 ppm or less. The lower the content of vanadium in the cemented carbide, the better, so the lower limit is preferably 0 ppm. Furthermore, there are cases where several ppm of vanadium is detected inadvertently due to manufacturing steps. The content of vanadium in the cemented carbide can be set from 0 ppm to 100 ppm, 0 ppm to 10 ppm.

The content of vanadium in the cemented carbide is determined by ICP emission spectrometry.

＜Manufacturing method of cemented carbide＞ Representatively, the cemented carbide of the present embodiment can be manufactured by sequentially performing the preparation step, mixing step, forming step, sintering step, and cooling step of the raw material powder. Hereinafter, each step will be described.

"Preparation Steps" The preparation step is the step of preparing all the raw material powders that constitute the material of the cemented carbide. As the raw material powder, tungsten carbide powder, which is the raw material of the first phase, and cobalt (Co) powder, which is the raw material of the second phase, can be cited as essential raw material powders. In addition, if necessary, chromium carbide (Cr ₃ C ₂ ) powder can be prepared as a grain growth inhibitor. In addition, as long as the effects of the present invention are exhibited, vanadium carbide (VC) powder may be prepared. Commercially available products can be used for tungsten carbide powder, cobalt powder, chromium carbide powder, and vanadium carbide powder.

For tungsten carbide powder, prepare (a) tungsten carbide powder with an average particle diameter of 0.4 μm or more and 1.2 μm or less (hereinafter also referred to as "the first tungsten carbide powder"), and (b) an average particle diameter of 0.8 μm or more and 1.2 μm The following tungsten carbide powder (hereinafter also referred to as "second tungsten carbide powder"). Regarding the first tungsten carbide powder, an average particle size smaller than that of the second tungsten carbide powder is prepared. In this specification, the average particle diameter of the raw material powder means the median diameter d50 of the circle equivalent diameter. The average particle size is measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.

The average particle size of the cobalt powder can be set to 0.8 μm or more and 1.2 μm or less. The average particle size of the chromium carbide powder can be set to 1.0 μm or more and 2.0 μm or less. The average particle size of vanadium carbide powder can be set to 0.5 μm or more and 1.0 μm or less.

"Mixed Steps" The mixing step is a step of mixing the raw material powders prepared in the preparation step. Through the mixing step, a mixed powder obtained by mixing each raw material powder is obtained.

The ratio of the first tungsten carbide powder in the mixed powder can be set to 30% by mass or more and 94.6% by mass or less, for example.

The ratio of the second tungsten carbide powder in the mixed powder can be set to 30% by mass or more and 64.6% by mass or less, for example.

The mixing ratio of the first tungsten carbide powder and the second tungsten carbide powder can be set to, for example, the first tungsten carbide powder: the second tungsten carbide powder=2:1 to 1:2 on a mass basis.

The ratio of the cobalt powder in the mixed powder can be set to, for example, 2.8% by mass or more and 10% by mass or less.

The ratio of the chromium carbide powder in the mixed powder can be set to, for example, 0.2% by mass or more and 1.2% by mass or less.

The ratio of the vanadium carbide powder in the mixed powder can be set to, for example, 0% by mass or more and 0.2% by mass or less.

Use a ball mill to mix the mixed powders. The mixing time can be set to 20 hours or more and 48 hours or less.

After the mixing step, the mixed powder can also be granulated if necessary. By granulating the mixed powder, it is easy to fill the mixed powder into the die nozzle or mold during the following forming steps. For granulation, a known granulation method can be applied. For example, a commercially available granulator such as a spray dryer can be used.

"Forming Steps" The forming step is a step of forming the mixed powder obtained by the mixing step into a specific shape to obtain a formed body. The forming method and forming conditions in the forming step may be general methods and conditions, and are not particularly limited. As the specific shape, for example, the shape of a cutting tool (for example, the shape of a small-diameter drill) can be cited.

"Sintering Steps" The sintering step is a step of sintering the formed body obtained by the forming step to obtain a cemented carbide. In the manufacturing method of the cemented carbide of the present invention, the sintering temperature can be set to the sintering temperature of the usual cemented carbide (1350-1500°C).

Cemented carbide is usually sintered at 1350 to 1500°C. Because of its large surface area, the particulate tungsten carbide particles are easy to dissolve in cobalt, so they are likely to produce abnormal structures due to dissolution and precipitation. Therefore, in the sintering of fine tungsten carbide particles, in order to suppress dissolution and re-precipitation, sintering is performed in a low temperature region of 1350 to 1380°C where the solid solubility limit of tungsten carbide to cobalt is relatively low. However, in the cemented carbide obtained by sintering in a low temperature region, the tungsten carbide particles have not undergone grain growth. Therefore, the surface of the tungsten carbide particles is broken due to the pulverization or mixing in the previous step. Therefore, the interface between the tungsten carbide particles and the cobalt or the interface between the tungsten carbide particles has a low binding force, and there is a tendency for wear resistance and breakage resistance to decrease.

On the other hand, in the manufacturing method of the cemented carbide of the present invention, the generation of the fragments of the ultrafine tungsten carbide particles generated by the crushing or mixing of the raw materials is suppressed, and the chromium grain growth suppressing effect is maximized. Furthermore, it was found that the distribution of coarse particles and fine particles with similar grain sizes and peaks in the fine structure can suppress abnormal grain growth even in a temperature region where grain growth usually occurs. Therefore, in the manufacturing method of the cemented carbide of the present invention, even if the tungsten carbide particles are sintered at a higher temperature than the previous temperature, the generation of abnormal structures can be suppressed, by making the interface between the tungsten carbide particles and the cobalt, or carbonizing The improvement of the bonding force of the interface between the tungsten particles can improve the wear resistance and breakage resistance of the cemented carbide. This is a new discovery obtained by the inventors after intensive research.

"Cooling Steps" The cooling step is a step of cooling the cemented carbide after sintering. The cooling conditions may be ordinary conditions, and are not particularly limited.

[Embodiment 2: Cutting tool] The cutting tool of the present invention includes a tip including the above-mentioned cemented carbide. In this specification, the tip of the tool refers to the part involved in cutting, which means that in the cemented carbide, the distance from the edge of the tool and the perpendicular from the edge of the tool to the side of the cemented carbide along the tangent of the edge of the tool is The area enclosed by an imaginary surface of 2 mm.

Examples of cutting tools include: cutting tools, drills, end mills, tip-changing cutting inserts for milling processing, tip-changing cutting inserts for turning processing, metal saws, gear cutting tools, reamers, or screws Attack and wait. When the cutting tool of the present invention is a small-diameter drill for processing a printed circuit board, it can particularly exhibit excellent effects.

The cemented carbide of this embodiment can constitute the whole or a part of these tools. Here, “constitute a part of it” means that the cemented carbide of the present embodiment is brazed to a specific position of an arbitrary base material to form a cutting edge.

"Hard Film" The cutting tool of this embodiment may further include a hard film that coats at least a part of the surface of the base material containing cemented carbide. As the hard film, for example, diamond-like carbon or diamond can be used. [Example]

This embodiment will be described in more detail with examples. However, this embodiment is not limited by these examples.

[Example 1] In Example 1, the types and blending ratios of the raw material powders were changed to produce cemented carbides of sample 1 to sample 24. Produce a small diameter drill with a tip containing the cemented carbide, and evaluate it.

"Production of Samples" (Preparatory steps) Prepare the powder of the composition shown in the "Raw Material" column of Table 1 as the raw material powder. Regarding tungsten carbide (WC) powder, a plurality of types with different average particle diameters are prepared. The average particle size of the carbonized WC powder is shown in the "average particle size (μm)" column of the "1st WC powder" in Table 1.

The average particle size of cobalt (Co) powder is 1 μm, the average particle size of vanadium carbide (VC) powder is 0.8 μm, and the average particle size of chromium carbide (Cr ₃ C ₂ ) powder is 1 μm. Co powder, VC powder, and Cr ₃ C ₂ powder are commercially available products. The average particle size of the raw material powder is a value measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.

(Mixing step) The raw material powders were mixed according to the blending amounts shown in Table 1 to produce mixed powders. The "mass%" in the "raw material" column of Table 1 represents the ratio of each raw material powder to the total mass of the raw material powder. The mixing system uses a ball mill for 20 hours. The resultant mixed powder is spray-dried to prepare granulated powder.

(Forming step) The obtained granulated powder is press-molded to produce a molded body in the shape of a ϕ3.4 mm round rod.

(Sintering step) The compact was placed in a sintering furnace and maintained at 1400° C. for 1 hour in a vacuum to perform sintering.

(Cooling step) After the sintering is completed, it is slowly cooled in an argon (Ar) atmosphere to obtain a cemented carbide.

[Table 1] Table 1 Sample No. raw material Cemented carbide Cutting test 1stWC powder 2ndWC powder Co powder Cr ₃ C ₂ powder VC powder WC particles Phase 1 Phase 2 Cr/Co V Abrasion (μm) Tool tip state Average particle size (μm) quality% Average particle size (μm) quality% quality% quality% quality% Circle equivalent diameter 0.3-1.0 μm 1st maximum frequency 2nd maximum frequency 2nd maximum frequency / 1st maximum frequency area% area% % ppm ratio(%) Grade (μm) ratio(%) Grade (μm) ratio(%) 1 0.5 94.6 - - 5 0.4 - 74 0.4-0.5 20.1 - - - 89.1 10.9 6.9 0 19.3 Normal wear 2 0.3 47.3 0.8 47.3 5 0.4 - 76 (0.2-0.3) 10.1 0.6-0.7 12.1 1.20 89.3 10.7 6.9 0 18.3 Normal wear 3 0.6 47.3 1.2 47.3 5 0.4 - 76 0.5-0.6 14 0.9-1.0 11.8 0.84 89.1 10.9 6.9 0 14.3 Normal wear 4 0.7 94.6 - - 5 0.4 - 75 0.5-0.6 18.4 - - - 89.3 10.7 6.9 0 18.9 Normal wear 5 0.6 64.6 0.8 30.0 5 0.4 - 72 0.4-0.5 14.3 0.6-0.7 10.8 0.76 89.5 10.5 6.9 0 13.2 Normal wear 6 0.6 47.3 0.8 47.3 5 0.4 - 70 0.4-0.5 13.2 0.6-0.7 12.1 0.92 89.5 10.5 6.9 0 12.8 Normal wear 7 0.4 47.3 1.0 47.3 5 0.4 - 73 0.3-0.4 11.2 0.8-0.9 14.3 1.28 89.1 10.9 6.9 0 15.1 Normal wear 8 0.6 30 0.8 64.6 5 0.4 - 75 0.4-0.5 10.3 0.6-0.7 13.4 1.30 89.5 10.5 6.9 2 13.8 Normal wear 9 0.7 47.3 1.2 47.3 5 0.4 - 76 0.5-0.6 13.4 0.7-0.8 12.3 0.92 88.9 11.1 6.9 1 12.4 Normal wear 10 0.8 94.6 - - 5 0.4 - 73 - - 0.6-0.7 18.5 - 89.3 10.7 6.9 0 17.8 Normal wear 11 1.2 94.6 - - 5 0.4 - 43 - - 0.9-1.0 19.3 - 89.2 10.8 6.9 0 - 3 broken 12 0.6 47.3 1.5 47.3 5 0.4 - 72 0.4-0.5 11.8 (1.0-1.1) - - 89.2 10.8 6.9 2 18.1 1 broken 13 0.6 48.5 0.8 48.5 2.8 0.2 - 75 0.4-0.5 13.4 0.6-0.7 12.4 0.93 94.5 5.5 6.2 0 13.2 Tiny debris 14 0.6 48.4 0.8 48.5 3.0 0.3 - 75 0.4-0.5 14.2 0.6-0.7 12.3 0.87 93.8 6.2 8.7 0 14.2 Normal wear 15 0.6 46.7 0.8 46.8 6.0 0.5 - 74 0.4-0.5 13.8 0.7-0.8 12.5 0.91 87.1 12.9 7.2 0 13.5 Normal wear 16 0.6 46.2 0.8 46.2 7 0.6 - 72 0.5-0.6 14.1 0.7-0.8 13 0.92 85.0 15.0 7.4 1 14.5 Normal wear 17 0.6 45.1 0.8 45.2 9 0.7 - 73 0.5-0.6 13.8 0.7-0.8 12.2 0.88 80.2 19.8 6.7 0 15.2 Normal wear 18 0.6 44.6 0.8 44.6 10 0.8 - 72 0.5-0.6 11.4 0.7-0.8 10.8 0.95 78.5 21.5 6.9 0 17.2 Normal wear 19 0.6 47.4 0.8 47.4 5 0.2 - 72 0.5-0.6 12.2 0.7-0.8 14.5 1.19 89.2 10.8 3.5 1 16.8 Normal wear 20 0.6 47.4 0.8 47.3 5 0.3 - 71 0.4-0.5 14.8 0.6-0.7 11.9 0.80 89.1 10.9 5.2 0 14.5 Normal wear twenty one 0.6 47.2 0.8 47.3 5 0.5 - 70 0.4-0.5 14.2 0.6-0.7 12.5 0.88 88.9 11.1 8.7 0 13.8 Normal wear twenty two 0.6 47.2 0.8 47.2 5 0.6 - 74 0.4-0.5 13.9 0.6-0.7 12.8 0.92 89.5 10.5 10.4 0 14.8 Tiny debris twenty three 0.6 47.3 0.8 47.3 5 0.4 0.1 75 0.4-0.5 12.1 0.6-0.7 11 0.91 89.6 10.4 6.9 100 13.8 Tiny debris twenty four 0.6 47.3 0.8 47.3 5 0.4 0.2 76 0.3-0.4 16.6 0.6-0.7 10.3 0.62 89.6 10.4 6.9 200 16.7 Tiny debris

＜Evaluation＞ For the cemented carbide of each sample, the distribution of the circle-equivalent diameter of tungsten carbide particles, the area ratio of the first phase and the second phase, the ratio of chromium to cobalt on the basis of mass, and the content of vanadium on the basis of mass were measured.

(Distribution of circle equivalent diameter of tungsten carbide particles) For the cemented carbide of each sample, the distribution of the circle-equivalent diameter of the tungsten carbide particles was measured, and the ratio of the number of tungsten carbide particles with the circle-equivalent diameter of 0.3 μm to 1.0 μm was calculated, and the level with the first maximum frequency was calculated. The ratio of the first maximum frequency to the total number of tungsten carbide particles, the level where the second maximum frequency exists, the ratio of the second maximum frequency to the total number of tungsten carbide particles, and the ratio of the second maximum frequency to the first maximum frequency. The specific measurement method and calculation method are described in the first embodiment, so the description thereof will not be repeated.

The results are shown in Table 1 "Ratio of circle equivalent diameter 0.3-1.0 μm (%)", "Level (μm)" and "Ratio (%)" of "First maximum frequency", and "Second maximum frequency" "Level (μm)" and "Ratio (%)", "2nd maximum frequency / 1st maximum frequency" column.

When the maximum frequency does not exist in the first range (over 0.3 μm and less than 0.6 μm) or the second range (over 0.6 μm and less than 1.0 μm), it is recorded as "-". Also, when the maximum frequency exists outside the first range (over 0.3 μm and less than 0.6 μm) or the second range (over 0.6 μm and less than 1.0 μm), the level of the maximum frequency is shown in parentheses ()Inside.

(Volume ratio of phase 1 and phase 2) For the cemented carbide of each sample, the area ratio of the first phase and the second phase in the image taken by the scanning electron microscope was measured. The specific measurement method is described in the first embodiment, so the description will not be repeated. The results are shown in Table 1 in the "Phase 1 (Area %)" and "Phase 2 (Area %)" columns.

(The ratio of chromium to the quality standard of cobalt, the content of the quality standard of vanadium) For the cemented carbide of each sample, the ratio of chromium to cobalt and the content of vanadium were measured. The specific measurement method is described in the first embodiment, so the description will not be repeated. The results are shown in the "Cr/Co (%)" and "V (ppm)" columns of Table 1.

＜Cutting test＞ Process the round rods of each sample to produce small-diameter drills with a blade diameter of ϕ0.35 mm. The current mainstream is to press the blade into the stainless steel shank to form a drill bit. For evaluation, the drill bit is manufactured by cutting the front end of a φ 3.4 mm round rod. Use this drill to drill holes for printed circuit boards for vehicles on the market. The conditions for drilling holes are set at a speed of 155 krpm and a feed speed of 2.5 m/min. Calculate the wear amount of the drill bit after 10,000 holes are opened according to the decrease in the diameter of the drill bit. Use 3 drills to drill holes. The average value of the abrasion of the three drill bits is shown in the "Abrasion Amount (μm)" column of Table 1. Also, observe the state of the tool tip after drilling. The results are shown in Table 1 in the "Tool Point State" column.

The smaller the wear, the longer the tool life of the drill. When the column of "Abrasion Amount (μm)" is marked as "-", it means that the 3 drills are damaged just after the start of processing, and the amount of abrasion cannot be measured. In addition, in the case where the "tool tip state" column is recorded as "1 broken", the average value of the abrasion of the two undamaged drill bits is shown in the "abrasion (μm)" column of Table 1. When it is marked as "micro chip" in the "tool tip status" column, it means that the tool tip produces small chips.

＜Discussion＞ Samples 3, 5-9, and 13-24 correspond to Examples.

Samples 1, 4, and 12 have no maximum frequency (second maximum frequency) in the second range, which corresponds to a comparative example. In addition, in the sample 12, there is an extremely high frequency in the level exceeding 1.0 μm and less than 1.1 μm.

Samples 2, 10, and 11 have no maximum frequency (first maximum frequency) in the first range, which corresponds to a comparative example. Sample 2 has a maximum frequency in the level exceeding 0.2 μm and less than 0.3 μm, and the ratio of the number basis of the maximum frequency is 10.1%.

It was confirmed that the wear amount of samples 3, 5-9, and 13-24 (examples) was smaller than that of samples 1, 2, 4, 10, and 12 (comparative examples), and the tool life was longer. In addition, in sample 11 (comparative example), all three drills were damaged immediately after the start, and the amount of wear could not be measured.

As described above, the embodiments and examples of the present invention have been described, but it is also stipulated at the beginning that the configurations of the above-mentioned embodiments and examples can be appropriately combined or variously modified.

It should be considered that the embodiments and examples disclosed in the text are illustrative in all aspects and not restrictive. The scope of the present invention is disclosed by the scope of the patent application, rather than the above-mentioned embodiments and examples, and is intended to include the meaning equivalent to the scope of the patent application, and all changes within the scope.

Fig. 1 is an example of an image of the cemented carbide of the present invention taken with a scanning electron microscope. Figure 2 is an image obtained by performing image processing on the captured image of Figure 1. Fig. 3 is a diagram showing an example of the distribution of the circle-equivalent diameter of tungsten carbide particles in the cemented carbide of the present invention. 4 is a diagram showing another example of the distribution of the circle-equivalent diameter of tungsten carbide particles in the cemented carbide of the present invention. Fig. 5 is a diagram showing another example of the distribution of the circle-equivalent diameter of tungsten carbide particles in the cemented carbide of the present invention. Fig. 6 is a diagram showing another example of the distribution of the circle-equivalent diameter of the tungsten carbide particles in the cemented carbide of the present invention.

Claims (10)

A cemented carbide having a first phase containing a plurality of tungsten carbide particles and a second phase containing cobalt, and In the case of calculating the circle equivalent diameter of each of the tungsten carbide particles by performing image processing on the image of the cemented carbide taken by a scanning electron microscope, the circle equivalent diameter is 0.3 μm or more and 1.0 μm or less. The ratio of the number of tungsten carbide particles mentioned above is 50% or more, When using a histogram with frequency as the vertical axis and grade as the horizontal axis to show the distribution of the circle-equivalent diameter of the tungsten carbide particles, The aforementioned frequency is the number of the aforementioned tungsten carbide particles, The above grade is divided by 0.1 μm in ascending order of the equivalent diameter of the above circle, In the above horizontal axis, the range exceeding 0.3 μm and less than 0.6 μm is defined as the first range, and the range exceeding 0.6 μm and less than 1.0 μm is defined as the second range. The first range and the second range each have at least one maximum frequency, The ratio of the largest first maximum frequency among the maximum frequencies existing in the first range to the total number of tungsten carbide particles is 10% or more, The ratio of the largest second maximum frequency among the maximum frequencies existing in the second range to the total number of tungsten carbide particles is 10% or more. Such as the cemented carbide of claim 1, wherein the cemented carbide in the image taken with a scanning electron microscope contains the first phase above 75 area% and less than 100 area%, and contains more than 0 area% and It is the above-mentioned second phase less than 20% by area. The cemented carbide of claim 1 or 2, wherein the cemented carbide in the image taken with a scanning electron microscope contains the above-mentioned second phase at 5 area% or more and 12 area% or less. Such as the cemented carbide of claim 1 or 2, wherein the above cemented carbide contains chromium, and The ratio of the chromium to the mass standard of the cobalt is 5% or more and 10% or less. Such as the cemented carbide of claim 1 or 2, wherein when the cemented carbide contains vanadium, the content of the vanadium in the cemented carbide on a mass basis does not reach 100 ppm. Such as the cemented carbide of claim 1 or 2, wherein the ratio of the number of tungsten carbide particles with the circle equivalent diameter of 0.3 μm or less is 7% or less. Such as the cemented carbide of claim 1 or 2, wherein the ratio of the second maximum frequency to the first maximum frequency is 0.8 or more and 1.2 or less. For the cemented carbide of claim 1 or 2, in the above horizontal axis, the range exceeding 0.4 μm and less than 0.6 μm is specified as the third range, and the range exceeding 0.6 μm and less than 0.8 μm is specified as the fourth In the case of scope, The above-mentioned third range has the above-mentioned first maximum frequency, and The above-mentioned fourth range has the above-mentioned second maximum frequency. A cutting tool provided with a tool tip containing the cemented carbide as claimed in any one of claims 1 to 8. The cutting tool according to claim 9, wherein the cutting tool is a rotary tool for processing a printed circuit board.

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