JP6608941B2 - Rod and cutting tool - Google Patents

Description

  The present embodiment relates to a rod-shaped body and a cutting tool such as a drill and an end mill.

  The long rod-shaped body is used as a structural member. For example, a blank made of a long cylindrical rod-like body becomes a cutting tool such as a drill and an end mill by performing a cutting process. A solid drill having a cutting edge located at the tip and a flute groove extending from the cutting edge is known as a drill used for drilling. The drill is used, for example, in drilling a substrate on which electronic components are mounted. As an example of the rod-shaped body, JP 2012-526664 A (Patent Document 1) discloses a blank having a different composition in the radial direction or the longitudinal direction.

  For the blank, a cemented carbide having a structure in which WC particles are bonded with a Co-containing binder phase is generally used. As the composition of the cemented carbide, for example, the one described in JP-A-8-218145 (Patent Document 2) is known. Patent Document 1 describes that the hardness can be increased by reducing the particle size of the WC particles.

  In recent years, blanks are required to have further improved wear resistance and breakage resistance.

This aspect is a long rod-shaped body made of a cemented carbide containing WC particles, Co, Cr, and V, and having a first end and a second end in the longitudinal direction, the first end The Co content in the second end portion is less than the Co content in the second end portion, the V content in the first end portion is less than the V content in the second end portion, and the first end portion toward the end the second end, with the content of Cr is changed in tilt S _Cr, the content of V are changed in inclined S _V, the inclination S _Cr is smaller than the inclination S _V.

FIG. 1 is composed of FIGS. 1A to 1D. FIG. 1A is a side view of a blank which is an example of a rod-shaped body of the present embodiment. FIG. 1B is a diagram showing a distribution of Co content in the blank of FIG. 1A. FIG. 1C is a diagram showing a distribution of Cr content in the blank of FIG. 1A. FIG. 1D is a diagram showing a distribution of V content in the blank of FIG. 1A. It is a transmission electron micrograph about an example of the cemented carbide in the blank of FIG. 1A. It is EDX analysis data which shows the distribution state of Co density | concentration in P of FIG. FIG. 4 is composed of FIGS. 4A and 4B. FIG. 4A is a side view of a variation of the blank of FIG. 1A. FIG. 4B is a diagram showing a distribution of Co content in the blank of FIG. 4A. It is a schematic diagram for demonstrating the structure of a metal mold | die about an example of the manufacturing method of the blank of FIG. It is a side view about an example of the drill of this embodiment.

  The rod-shaped body will be described with reference to the drawings. A blank for a cutting tool in the present embodiment (hereinafter also simply referred to as a blank) is an example of a rod-shaped body. FIG. 1A is a side view of a blank, and FIGS. 1B to 1D are diagrams showing distributions of Co content, Cr content, and V content in the blank, respectively. In addition, the part shown with the dotted line in FIG. 1A has shown an example of the cutting tool (drill 1) formed using a blank.

  A blank 2 used in the drill 1 of FIG. 1 which is an example of a cutting tool has a long cylindrical shape made of a cemented carbide containing WC, Co, Cr and V, and has a first end portion in the longitudinal direction. An end portion (hereinafter referred to as an end portion A) located on the side, and an end portion (hereinafter referred to as an end portion B) located on the second end portion side. When using the blank 2 of this embodiment for the drill 1, the cutting edge 5 is formed in the edge part (henceforth the edge part X) located in the 1st edge part side, and the 2nd edge part in the drill 1 is used. The end B of the blank 2 is joined to the shank 3 located at the end on the side (hereinafter referred to as end Y). The blank 2 may be directly joined to the shank 3 or may be another member.

  In the present embodiment, since the cutting edge 5 is formed by polishing the end A in the blank 2, the end A in the blank 2 is more than the end X where the cutting edge 5 in the drill 1 is formed. It is located on the first end side.

  In addition to WC, Co, Cr, and V, the blank 2 may contain carbides of periodic table 4, 5, and 6 metals except W, Co, Cr, and V. The blank 2 has high corrosion resistance because it contains Cr. Moreover, heat resistance can be improved by containing Co and Cr. Moreover, since Cr and V can suppress abnormal grain growth of WC particles, a cemented carbide with high strength can be stably produced. For example, a cemented carbide having an average WC particle size of less than 1 μm can be used.

According to this embodiment, in the state of blank 2, the content Co _A of Co at the end A is less than the content Co _B of Co at the end B. In the state of the drill 1, the Co content at the end X is less than the Co content at the end Y. As a result, the wear resistance on the side of the end X having the cutting edge 5 can be increased, and the resistance to breakage on the side of the end Y from the center of the cutting tool such as the drill 1 or the end mill, which is easily broken. Can be increased. In addition, the “content” in the present embodiment is not a value indicating an absolute amount but a value indicating a content ratio (mass%).

Further, in the state of the blank 2, the V content V _A at the end _A is less than the V content V _B at the end B. From another viewpoint, in the state of the drill 1, the Co content in the end X is less than the Co content in the end Y. Since the _VA is relatively small at the end A, the grain growth of the WC particles is hardly suppressed on the end A side, and the average particle diameter of the WC particles is increased.

  As a result, the chipping resistance of the cemented carbide is improved on the end A side. On the other hand, on the side of the end portion B, since the content of the V element is relatively large, grain growth of the WC particles is suppressed on the side of the end portion B, and the average particle size of the WC particles is reduced. As a result, the strength of the cemented carbide is increased on the end Y side, and the breakage resistance of the drill 1 is improved.

Blank 2 in the present embodiment has a region in which the content of V is varied in slope S _V with the content of Cr is changed in tilt S _Cr toward the end A to end B. Viewed another way, the drill 1 has a region where the V content is varied in slope S _V with the content of Cr is changed in tilt S _Cr toward the end X to the end Y Yes.

Thus, by tilting S _Cr is smaller than the inclination S _V, the corrosion resistance is improved over the entire blank 2. Moreover, by tilting S _V is greater than the inclination S _Cr, at the side of the end portion A is improved and high and chipping resistance hardness, thereby improving the strength is high and breakage resistance in the side of the end portion B .

  In addition, in this embodiment, although the edge part A and the edge part B point out the edge part of the blank 2, specifically, it points out the range which can analyze the composition of the blank 2 by EPMA analysis. In order to confirm the composition change in the longitudinal direction of the blank 2, the distribution of the content of each metal element in the longitudinal direction of the blank 2 is measured and confirmed by EPMA analysis. In FIG. 1C and FIG. 1D, in the EPMA analysis of the blank 2, the measurement values at the ends where accurate composition measurement is not possible are omitted. In FIG. 4, the description of the distribution of Cr element and V element is omitted.

And in Co content, when Co _A is 0-10 mass% and Co _B is 2-16 mass%, the abrasion resistance and defect resistance of the blank 2 can be maintained highly. More preferable ranges of Co _A and Co _B vary depending on processing conditions. For example, when using a blank 2 as a drill 1 for processing a printed circuit board, Co _A is set to 1 to 4.9% by mass, and Co _{A What} is necessary is just to make _B into 5-10 mass%.

When Co _B is 5% by mass or more, it is easy to densify the end portion B in a normal uniform composition, and it is difficult to form Co agglomerated portions in the blank 2 after firing. Therefore, the Co distribution is less likely to be uneven. This is presumably because when Co _B is 5% by mass or more, Co diffuses due to the Co capillary phenomenon, so that Co agglomerates are difficult to form, and a uniform distribution state is likely to occur. As a result, a dense cemented carbide is obtained on the end A side even if Co _A is relatively small.

Further, when the ratio of Co _A to Co _B (Co _A / Co _B ) is 0.2 to 0.7, the hardness at the end A can be improved, and the breakage resistance of the blank 2 can be improved. Can increase the sex.

Further, the ratio of V _A to V _B (V _A / V _B ) is 0.3 to 0.9, and the ratio of Cr _A to Cr _B (Cr _A / Cr _B ) is 0.8 to 1. In the case of 0.1, the corrosion resistance, heat resistance and strength of the blank 2 can be increased.

In addition, Cr _A which shows content of Cr in the edge part A is 0.05-2 mass%, Cr _B which shows content of Cr in the edge part B is 0.1-3 mass%, and edge part When V _A indicating the content of V in _A is 0 to 1% by mass and V _B indicating the content of V in the end portion _B is 0.05 to 2% by mass, the corrosion resistance of the blank 2, Heat resistance and strength can be further increased.

At least a part of Cr is solid-solved as a metal in the binder phase, and in addition, it exists as a composite carbide with Cr ₃ C ₂ or other metals. V is at least partly dissolved as a metal in the binder phase, and may also be present as a composite carbide with VC or other metals, but V is a solid solution in the binder phase compared to Cr. The amount is small. In this embodiment, Cr _A and Cr _B are values obtained by converting the Cr content into Cr ₃ C ₂ , and V _A and V _B are values obtained by converting the V content into VC.

S _Cr is 0 to 0.1 wt% / mm, when _{S V} is 0.1 to 0.5 mass% / mm, the corrosion resistance of the blank 2, heat resistance, on the side of the end portion A High wear resistance and chipping resistance, and breakage resistance on the end B side.

_{Incidentally,} Co _{A, Co} B, _Cr A, Cr _B, V A, method of measuring _{V B} is in a state of being split in half along the blank 2 in the longitudinal direction, end A and the end B by EPMA analysis It can confirm by measuring the composition in each of these. The composition analysis from the end A to the end B of the blank 2 is measured on a central axis parallel to the longitudinal direction of the cross section. Calculating a distribution of the content and the V content in the longitudinal direction of the Cr of the blank 2 was determined by EPMA analysis, the slope when approximated to a straight line by the least square method for the entire distribution of the blank 2 S _Cr, as S _V To do.

  The end portion A in the present embodiment has an outer peripheral portion and a central portion positioned at least 100 μm from the outer peripheral portion. At this time, when the content of Cr in the outer peripheral portion is larger than the content of Cr in the central portion, the corrosion resistance of the blank 2 can be further improved. In addition, an outer peripheral part refers to the range which can analyze the composition of the blank 2 by EPMA analysis in an outer periphery. Moreover, in this embodiment, the corner | angular part by the side of the edge part A in the cross section which divided | segmented the blank 2 in half along the longitudinal direction was made into A outer peripheral part, and content of Cr in this A outer peripheral part was measured. Yes.

When the average particle diameter a _A of the WC particles at the end _A is larger than the average particle diameter a _B of the WC particles at the end B, the wear resistance of the end A where the hardness is high and defects are likely to occur. Can be improved. Further, since the rigidity of the end portion B is increased, the rod-shaped body is not easily bent. Therefore, when the blank 2 is a cutting tool having the cutting edge 5 on the end X side and the shank 3 on the end Y side, the wear resistance of the cutting edge 5 and the chipping resistance at the end A are provided. Is further improved, and the breakage resistance at the end B is further improved.

  The average particle diameter of the WC particles is calculated by a Luzex analysis method from a scanning electron microscope (SEM) photograph. Moreover, you may use the following method as another method of confirming the average particle diameter of WC particle | grains.

  First, about the cross section of the blank 2, the orientation direction of WC particle | grains is observed by the electron beam backscattering diffraction (EBSD) method by SEM with a backscattering electron diffraction image system. The outline of each WC particle is specified by confirming the orientation direction of each WC particle. Then, the area of each WC particle is calculated based on the outline of each WC particle, and the diameter when this area is converted into a circle is taken as the particle diameter. And let the average value of the particle size of each WC particle be an average particle size.

The average particle size _{a A} of WC grains at the ends A, for example, can be set to 0.3 to 1.5 .mu.m, The average particle size _{a B} of the WC grains at the end B are 0.1~0.9μm Can be set. When the average particle size a _A and the average particle size a _B is the above described values, as well as chipping of the edge portion A is further improved, breakage of the end portion B is further improved. When the blank 2 is used for the drill 1, the desirable range of the average particle diameter of the WC particles at the end A is 0.4 to 0.7 μm, and the desirable range of the average particle diameter of the WC particles at the end B is 0. 15 to 0.5 μm.

The blank 2 is positioned closer to the end B than the first region 11 and the first region 11 in which the Co content changes with the slope _{S1Co as} it goes from the end A to the end B. You may have 2nd area _| region 12 from which content of Co changes with inclination _{S2Co as} it goes to the edge part B from the part A. As _shown in FIG. At this time, when the slope S 1 _Co is larger than the slope S 2 _Co, the toughness in the wide area on the end B side can be increased while maintaining the wear resistance on the end A side high, and the blank 2 Breakage resistance can be improved.

In the first region 11, the Cr content may change with the slope S _1Cr , and the V content may change with the slope S _1V . In addition, in the second region 12, the Cr content may change with the slope S _2Cr , and the V content may change with the slope S _2V .

Note that the inclination (S _1Co , S _2Co , S _1Cr , S _2Cr , S _1V , S _2V ) indicates the rate of change in the content of each metal element (Co, Cr, V) in the longitudinal direction of the blank 2. The presence of the first region 11 and the second region 12 can be confirmed by the distribution of Co content in the longitudinal direction of the blank 2. Then, the Cr content and the V content in the first region 11 and the second region 12 are measured, and the slopes when the distribution in each region is approximated by the least square method are expressed as S _1Co , S _1Cr , S _1V , _{S 2Co,} S 2Cr, calculated as _{S 2V.} In addition, as for inclination, the direction which becomes low toward the edge part B from the edge part A is made into plus, and the direction which becomes high toward the edge part B from the edge part A is made into minus.

When the slope S _1Co is 0.2 to 1% by mass / mm and the slope S _2Co is ₀ to _0.2 % by mass / mm, the hardness on the end A side can be improved, and the blank 2 Breakage resistance can be improved. Note that the slope S _1Co in the first region 11 may not be constant within the region. In particular, in the first region 11, when the inclination on the end portion A side becomes large, the wear resistance at the end portion A is high and the breakage resistance of the blank 2 becomes higher.

  In addition, when coating the surface of the blank 2 with a diamond coating layer (not shown), if the content of Co contained in the second region 12 is small, the content of Co that hinders the growth of diamond crystals. Therefore, in the second region 12, the degree of crystallinity of the diamond coating layer is increased, so that the hardness and adhesion of the diamond coating layer are improved.

  As shown in the transmission electron microscope (TEM) photograph of FIG. 2, the blank 2 of FIG. 1A has a plurality of WC particles 25 as the composition of the cemented carbide. Between these two WC particles 25 adjacent to each other, a grain boundary 27 containing Co exists. Adjacent WC particles 25 can be bound by the grain boundaries 27.

  When two adjacent WC particles 25 and a grain boundary 27 located between these WC particles 25 are set as one set, the blank 2 of this embodiment has a region where a plurality of such sets are positioned. doing. When this region is measured in each of 10 or more sets in one field of view as shown in FIG. 2, the Co concentration at the grain boundary 27 and the Co concentration in the WC particles 25 adjacent through the grain boundary are measured. The group in which the Co content is 1 to 7% by mass and the Co concentration in the grain boundary 27 is 1.2 times or more the Co concentration in the adjacent WC particles 25 is 50% or more.

  When the blank 2 has the above-described region, the drill 1 having excellent hardness and strength can be obtained even when the Co content is as low as 1 to 7% by mass. This is presumably because Co as a binder phase is diffused and present in the grain boundaries 27 and the WC particles 25 can be bound. In other words, the percentage of the set in which the Co concentration in the grain boundary 27 is 1.2 times or more that in the grain of the WC grain 25 confirms the degree of dispersion of Co constituting the binder phase in the grain boundary 27. .

  FIG. 3 shows a change in the Co concentration distribution in a portion straddling two adjacent WC particles 25 and a grain boundary 27 located between these particles, which is indicated by a line P in FIG. In FIG. 3, the portion rising within the dotted line is a portion corresponding to the grain boundary 27, and the grain boundary 27 in the line P has a Co concentration 1.2 times or more that of the WC particles 25.

  In order to specify the presence of the region 29, observation is performed with a TEM in one field of view in which ten or more WC particles 25 can be confirmed. Within this single field of view, the concentration distribution of Co is confirmed from within the grain of one WC particle 25 to across the grain boundary 27 and into the grain of the adjacent WC particle 25. In setting the “set” described above, the “set” can be set if the combination of adjacent WC particles 25 is different.

  For example, when 10 WC particles 25a to 25j are observed, 25a and 25b, 25a and 25c, 25a and 25h, 25a and 25f, 25b and 25c, 25b and 25d, 25c and 25e, 25f and 25g, 25i and Ten or more “sets” are set with the grain boundaries 27 between 25h, 25i and 25j, and 25h and 25j.

  In each group, first, the average value Coa of the Co content in the WC particles 25 is calculated from the Co concentration distribution. Next, the maximum value Comax of the Co content at the grain boundary 27 is confirmed. The existence of the region 29 can be confirmed by checking whether the pair having Comax / Coa of 1.2 or more is 50% or more. The region 29 may exist over the entire blank 2, but at least a specific position may be configured by the region 29.

  Further, in the region 29, when the average particle size of the WC particles 25 is 0.1 to 1.5 μm, the WC particles 25 are firmly bonded while being fine particles. Toughness and strength are further increased.

  Further, in the region 29, when the standard deviation in the particle size distribution of the WC particles 25 is 0.5 μm or less, the variation of the WC particles 25 is small, so that the strength of the blank 2 can be further increased.

Further, when the ratio of Co _A to Co _B (Co _A / Co _B ) is 0.2 to 0.7, the hardness at the end A can be improved, and the breakage resistance of the blank 2 can be improved. Can increase the sex.

When the intermediate portion between the position having an intermediate value between Co _A and Co _B is an intermediate portion and the cemented carbide constituting the intermediate portion and the end portion A is composed of the region 29, the wear resistance of the cutting edge 5 in the drill 1 In addition, the chipping resistance can be increased.

Between the 1st area _| region 11 and the 2nd area _| region 12, the 3rd area _| region 13 where content of Co changes with inclination _{S3Co as} it goes to the edge part B from the edge part A may be located. At this time, when the inclination of the inclined _{S 3Co} is greater than the slope _{S 2Co} is inclined _S 1co of the first region 11 and the second region _12, it is easy to control the _{S 2Co,} breakage prone end The breakage resistance on the part B side can be further increased. If the slope _S3Co is 2 to 50 mass% / mm, both the wear resistance on the end A side and the breakage resistance on the end B side can be improved.

FIG. 1D shows a change in the content of the V element so as to correspond to the change in the content of the Co element. That is, in FIG. 1D, the slope S _1V of the V element in the first region 11 is larger than the slope S _2V of the V element in the second region 12. Further, the slope S _3V of the V element in the third region 13 is larger than the slope S _1V of the V element in the first region 11.

  On the other hand, in FIG. 1C, the change in the content of Cr element does not correspond to the change in the content of Co element, and the reason is unknown, but the value of Cr content at adjacent positions varies greatly. On the other hand, the overall change is small.

Blank 2 includes, as shown in FIG. 4, on the side of the end A than the first region 11 may have a fourth region 14 in which the content of Co is changed in tilt S _4CO. At this time, when the inclination of the inclined S _4CO is smaller than the inclination of the inclined S _1co it is likely to widen the range of high wear resistance in the side of the end portion A.

In addition, when the gradient S 4 _Co is 0 to 0.5 mass% / mm and the Co content in the fourth region 14 is 0 to 0.6 mass%, a diamond coating layer is formed on the surface of the blank 2. When coating is performed, the content of Co contained in the fourth region 14 is reduced, so that the crystallinity of the diamond coating layer on the surface of the fourth region 14 can be further increased. Therefore, the hardness and adhesion of the diamond coating layer are improved. An inflection point in the distribution of Co content may exist at the boundary between the first region 11 and the fourth region 14.

When the length of the first region 11 is L ₁ , the length of the second region 12 is L ₂ , the length of the third region 13 is L ₃ , and the length of the fourth region 14 is L ₄ , L ₁ / when L 2 ₌ 0.3 to 3, as well as can improve the hardness of the end portion a, it is possible to enhance the breakage resistance of the blank 2. When L ₃ / L ₂ = 0.01 to 0.1, it is easy to adjust the Co content in the second region 12 and the first region 11. When L ₄ / L ₂ = is 0 to 0.05, densification of the cemented carbide at the end A can be more stably promoted. When L ₄ / L ₂ = is larger than 0.05 and there is a non-densified portion in the fourth region 14, a part of the fourth region 14 is polished and removed when the drill 1 is manufactured. May be.

  In addition, what is necessary is just to measure the composition of the 1st area | region 11, the 2nd area | region 12, the 3rd area | region 13, and the 4th area | region 14 in the center part of the width direction of the blank 2, respectively.

Content Co _AO of Co in the outer peripheral portion of the end portion A, if less than the content Co _A of Co at the center of the end portion A, in the rotary tool drill or end mill, among the cutting edge 5 Abrasion resistance in the outer peripheral portion that is most easily worn can be increased.

In FIGS. 1 and 4, the blank 2 has a protrusion 15 located at the end A. The protrusion 15 has a smaller diameter than the portion located on the second end side of the protrusion 15. That is, the diameter d _c of the projection 15 is smaller than the diameter d _A at the portion located on the second end side of the projection 15. Although the protrusion 15 can be easily formed and is not shown, the tip of the drill 1 that has been bladed can be formed on the protrusion 15, so that the processing cost is not wasted.

  As shown in FIGS. 1 and 4, when the protrusion 15 is hemispherical, the protrusion 15 may be lost even if the blanks 2 collide with each other when the blank 2 is randomly inserted into the bonding apparatus. It is suppressed, and it can also be controlled that other blank 2 is damaged by projection part 15. Moreover, in this embodiment, the base part side which the projection part 15 connects to the edge part A is connected by the R surface in the cross sectional view. Accordingly, it is possible to suppress the load from being concentrated on the end portion of the lower punch 23 during the molding of the molded body 35 and the lower punch 23 from being chipped.

In this case, the at both 2mm or less diameter _{d B} of diameter _{d A} and B of the end A, when the longitudinal length is L, the ratio of L to _{d A} (L / _{d A)} is 3 or more In some cases, it is easy to adjust Co _A and Co _B to predetermined values in the blank 2 after firing. That is, when the ratio (L / d _A ) is a large value, even if Co diffuses during firing, it is easy to ensure a sufficient difference between Co _A and Co _{B in} the blank 2. _A more desirable range of the ratio (L / d _A ) is 4 to 10.

  The blank 2 may be in a state where it is not polished after firing, but in order to increase the positional accuracy of the blank 2 when gripping the blank 2 in the step of joining the blank 2 to the shank 3, the outer periphery of the blank 2 after firing The surface may be centerless processed.

Incidentally, the preferred dimensions of the blank 2, when used as a drill 1 for a printed board _machining, d A, is _{d B} 0.2 to 2 mm, the length L is 3 to 20 mm. _A particularly desirable range of dA is 0.3 to 1.7 mm. In other applications, d _A may exceed 2 mm, in which case the preferred range for d _A is 0.2-20 mm and L = 3-50 mm.

  In the present embodiment, the drill 1 used for drilling a printed circuit board is illustrated as a cutting tool. However, the present invention is not limited to this, and the drill 1 may have a long main body. That's fine. For example, the present invention can be applied as a cutting tool for turning such as a drill for metal processing, a medical drill, an end mill, and a throw-away tip for inner diameter processing. Further, the rod-like body such as the blank 2 can be used as an anti-wear material and a sliding member other than the cutting tool. Even when the rod-like body is used as a tool other than a cutting tool, the rod-like body is suitably used for an application in which the region including the end A is used in contact with the mating member in a state where the end B is fixed and processed. It is done.

(Blank manufacturing method)
As an example of a method for manufacturing the blank, a method for manufacturing the blank 2 having the protrusions 15 will be described. First, raw material powders, such as WC powder for producing the cemented carbide forming the blank 2 and the cutting tool (drill 1), are prepared. In this embodiment, two types of raw material powders are prepared.

A first raw material powder 30 for producing a part including the end A where the protrusion 15 is located in the blank 2 and a second raw material powder 33 for producing a part on the end B side are prepared. The first raw material powder 30, as raw material powder, _Cr 3 _{C 2} powder, VC powder, may contain a Co powder.

The second raw material powder 33 contains WC powder, Cr ₃ C ₂ powder, VC powder, and Co powder as raw material powder. The content of Cr ₃ C ₂ powder, VC powder and Co powder in the first raw material powder 30 is less than the content of Cr ₃ C ₂ powder, VC powder and Co powder in the second raw material powder 33. The content of the Co powder in the first raw material powder 30 is a mass ratio with respect to the content of the Co powder in the second raw material powder 33 and is 0 to 0.5, particularly 0 to 0.3.

In addition to the above powders, the first raw material powder 30 and the second raw material powder 33 are carbides, nitrides, and carbonitrides of periodic tables 4, 5, and 6 metals other than WC, Cr ₃ C ₂ , and VC, respectively. Any additive of the product powder may be contained.

  For example, the amount of WC powder in the first raw material powder 30 is 90 to 100% by mass, the amount of Co powder is 0 to 8% by mass, and the amount of additives is 0 to 5% by mass in total. . The amount of WC powder in the second raw material powder 33 is 65 to 95% by mass, the amount of Co powder is 5 to 30% by mass, and the amount of additives is 0 to 10% by mass in total. . Further, the average particle size of the WC powder in the first raw material powder 30 and the average particle size of the WC powder in the second raw material powder 33 are made different from each other, so that the end portion A to the end portion B of the blank 2 after firing. It is also possible to adjust the distribution characteristics, hardness, toughness, and the like of Co, Cr, and V.

  A slurry is prepared by adding a binder and a solvent to the prepared powder. This slurry is granulated into granules and formed into molding powder.

  As shown in FIG. 5, a press molding die (hereinafter simply abbreviated as a die) 20 is prepared, and the above granules are put into a cavity 22 of a die 21 of the die 20. Then, the upper punch 24 is lowered from above the granules put into the cavity 22 of the die 21 and pressed to produce a molded body. In the present embodiment, the upper surface serving as the pressing surface of the lower punch 23 that is the bottom of the cavity 22 has a recess 25 for forming the protrusion 15.

  The molding method according to the present embodiment includes a step of putting the first raw material powder 30 into a region including the recess 25 in the cavity 22, a step of putting the second raw material powder 33 into the cavity 22, and lowering the upper punch 24 from above. The step of pressurizing the laminated body of the first raw material powder 30 and the second raw material powder 33 introduced into the cavity 22 of the die 21 and the step of taking out the molded body 35 made of this laminated body from the mold 20 are performed. It has.

  The molded body 35 has a cylindrical shape, and the Co content at the end A is less than the Co content at the end B. As a result, it becomes easy to adjust the distribution of the predetermined Co content in the blank 2.

  Moreover, when the bottom face of the recessed part 25 is a curved surface, in the molded object 35, while the chip | tip of the raw projection part 32 can be suppressed, the variation in Co content in the projection part 15 in the blank 2 after baking can be suppressed. For this reason, local sintering defects are easily avoided. Note that the recess 25 and the protrusion 15 may be omitted.

  In the case of obtaining a sintered body having a diameter of 2 mm or less, for example, the position of the upper punch 24 from the holding position of the upper punch 24 at the time of pressurization is 0.1 mm to 2 mm, 0.1 to the length of the molded body. An additional load may be applied to the upper punch 24 and the load on the lower punch 23 may be reduced so as to descend downward by the length of% to 20%. When the molding conditions are as described above, unevenness in pressure applied to the molded body 35 is improved, so that it is easy to avoid breakage when the molded body 35 is extracted, and the blank 2 after firing the molded body 35 is easy to avoid. The shape can be a predetermined shape.

In this case, FIG. 5 as shown in the may be smaller than the diameter D _B of the diameter D _A of the lower punch 23 side of the molded body 35 upper punch 24 side. _A desirable range of the ratio D _A / D _B in the present embodiment is 0.8 to 0.99.

  Although not particularly illustrated, for example, between the first raw material powder 30 and the second raw material powder 33, the Co powder content in the second raw material powder 33 is smaller than the Co powder content in the first raw material powder 30. Other raw material powders such as a third raw material powder having a Co powder content higher than the content of Co may be present.

  The pressure-molded molded body is taken out from the mold, fired at 1300-1500 ° C. for 0.5-2 hours, and then subjected to sinter HIP treatment to become a blank 2. The firing temperature is adjusted by the Co content and the average particle size of the WC particles. At this time, in this embodiment, the rate of temperature increase from 1000 ° C. during firing to the firing temperature is 4 to 7 ° C./min, and the reduced pressure at the firing temperature is 50 to 200 Pa. Then, the sinter HIP is processed at a temperature 5 to 20 ° C. lower than the sintering temperature and a pressure of 5 to 10 MPa. Accordingly, the Co content in the end A, the end B, the second region 12, the first region 11, the third region 13, and the fourth region 14 can be easily adjusted.

  Moreover, since the sinterability of the first raw material powder 30 and the second raw material powder 33 is different, the shrinkage rate of the end A and the end B is different during firing, and the molded body is deformed, and the shrinkage rate of the end B Becomes larger than the contraction rate of the end portion A. That is, a part of Co at the end portion B diffuses toward the end portion A by firing, so that the end portion B contracts more than the end portion A. Accordingly, the diameter of the end portion B tends to be smaller than the diameter of the end portion A in the shape of the sintered body.

Here, when the heating rate is faster than 4 ° C./min, it is possible to avoid excessive diffusion of Co during firing. Therefore, the difference in Co concentration in the blank 2 after sintering can be increased, and S _V the easily greater than _{S Cr,} also prone to less than the Co _a Co _B. When heating rate is slower than 7 ° C. / minute, easily and S _Cr smaller than S _V, it becomes easier to densify the WC grains at the ends A.

In addition, when the reduced pressure at the firing temperature is 50 Pa or more, it is possible to avoid excessive diffusion of Co during firing, so that the difference in Co concentration in the sintered blank 2 can be increased. Further, it is easy to be larger than the _{S V S Cr,} a Co _A less than Co _B easily. If decompression pressure is less than 200Pa _is easily the _{S Cr} smaller than _{S V,} it becomes easier to densify the WC grains at the ends A. In addition, when the region 29 is formed, the reduced pressure is 50 to 200 Pa, so that the diffusion of Co is likely to be uniform, and thus the region 29 is easily formed.

Further, if the difference is greater than 5 ° C. and the processing temperature and the sintering temperature of the sinter HIP is easily greater than the _{S V S Cr,} a Co _A less than Co _B easily. At this time, in the case of forming the region 29, since the difference from the above sintering temperature is larger than 5 ° C., it is easy to avoid the diffusion of Co during the firing. Co is less likely to agglomerate and the region 29 is more easily formed.

Further, when the difference between the processing temperature and the sintering temperature of the sinter HIP is 20 ° C. or less, likely to be smaller than the S _Cr S _V, becomes easier to densify the WC grains at the ends A. Here, when the region 29 is formed, the difference between the above-described sintering temperature is 20 ° C. or less, and the shrinkage of the blank 2 is likely to proceed, so that Co can be diffused satisfactorily.

  In addition, the shaping | molding process in this invention is not limited to the press molding shown in the said embodiment, It can also shape | mold by cold isostatic pressing, dry bag shaping, injection molding, etc.

(Manufacturing method of cutting tool)
An example of a method for producing a drill 1 for processing a printed circuit board using the blank 2 obtained by the above process will be described. Dozens or hundreds of blanks 2 are randomly placed in the bonding apparatus. The blank 2 is aligned in a state where the longitudinal direction is aligned in the bonding apparatus. When the projection 15 is provided, the projection 11 is confirmed by image data or the like, and the end A and the end B of the blank 2 are specified. Based on this specification, the end A and the end B can be automatically arranged in a certain direction.

  The arranged blanks 2 are automatically brought into contact with a member constituted by a separately prepared shank 3 and neck 7 and then joined by a laser or the like. Thereafter, blade joining is performed on the joined blank 2. At this time, as shown in FIG. 1, the drill 1 is configured such that the end X is on the cutting blade 5 side of the drill 1 and the end Y is on the shank 3 side of the drill 1.

(Cutting tools)
A cutting tool such as a drill 1 is produced by cutting the blank 2. The drill 1 in FIG. 6 includes a blank 2 (machined portion) that has been subjected to blade machining, a neck portion 7 joined to the machined portion, and a shank 3 that is positioned on the rear end side (upper side in FIG. 6) of the neck portion 7. Has been. The processing portion includes a cutting edge 5 located at the end X, and has a groove 6 following the cutting edge 5. A body 8 is constituted by the processed portion and the neck portion 7. Therefore, it can be said that the shank 3 is located on the rear end side of the body 8. The maximum diameter of the processed part is set to 2 mm or less, for example.

  The cutting edge 5 is a portion that first contacts the work material while rotating around a central axis, and is required to have high chipping resistance and wear resistance. The groove 6 has a function of discharging chips generated by processing backward, and the neck portion 7 is a connecting portion that connects the processing portion and the shank 3 having different diameters. The maximum diameter of the processed part is set to 2 mm or less, for example. The shank 3 can be used as a part for fixing the drill 1 to the processing machine.

  Although not particularly illustrated, a coating layer may be positioned on the surface of the drill 1. Examples of the coating layer include TiN, TiCN, TiAlN, diamond, diamond-like carbon, and diamond formed by the CVD method, which are formed by the PVD method.

  The drill 1 may have a structure in which the neck 7 and the shank 3 are made of an inexpensive material such as steel, alloy steel, or stainless steel, and the blank 2 is joined to the tip of the neck 7. Further, the entire drill 1 may be constituted by the blank 2. Moreover, the neck 7 is not essential, and the drill 1 may have a configuration in which the blank 2 and the shank 3 are directly joined.

Metal cobalt (Co) powder, chromium carbide (Cr ₃ C ₂ ) powder, vanadium carbide (VC) powder, and the balance of tungsten carbide (WC) powder having an average particle size of 0.3 μm as shown in Table 1, Two kinds of mixed powders of the first raw material powder and the second raw material powder shown in Table 1 were prepared. To each mixed powder, a binder and a solvent were added and mixed to prepare a slurry, and granules having an average particle diameter of 70 μm were prepared with a spray dryer.

A mold shown in FIG. 5 provided with a die having 144 through holes was prepared. The first raw material powder of Table 1 was charged, and then the second raw material powder of Table 1 was filled and press-molded. A molded body in which the first raw material powder and the second raw material powder were laminated was molded by press molding and taken out of the mold. At this time, the diameter of the lower punch side is D _A , the diameter of the upper punch side is D _B , the length of the lower part of the molded body is H _A , and the length of the upper part of the molded body is H _B. Indicated.

  The molded body was heated from 1000 ° C. at the rate of temperature increase shown in Table 2 and fired for 1 hour in the atmosphere and firing temperature shown in Table 2. Then, the sintered HIP (shown as HIP in Table 2) temperature shown in Table 2 was obtained. Instead, a sinter HIP process was performed at a pressure of 5 MPa for 30 minutes, the temperature lowering rate to 1200 ° C. or lower was cooled at 10 ° C./min, and then cooled to 200 ° C. or lower as it was to obtain a blank.

The obtained blank shown in Table 2 to measure the diameter d _A, and the diameter d _B. Further, the blank was divided in half along the longitudinal direction, and changes in Co content, Cr content, and V content from end A to end B were measured by EPMA analysis. The presence, inclination, and length of the fourth region were confirmed from the region. Furthermore, about the edge part A of a blank, content of Co in an outer peripheral part was measured. The results are shown in Tables 2-5. Moreover, the average particle diameter of the WC particle | grains in A center part, A outer peripheral part, and B center part was measured by EBSD method.

  Furthermore, about the part of obtained blank, the surface is grind | polished and a grinding | polishing surface is created, The position used as the content of Co in the middle of Co content in the edge part A and Co content in B part is intermediate As a part, it observed in the visual field which can confirm 10 or more of WC particles.

  First, the Co content in this visual field was determined using TEM. Within this field of view, the concentration distribution of Co across the grain boundary from one WC particle to the inside of the adjacent WC particle was confirmed by EDX. Then, two adjacent WC particles and a grain boundary located between them are taken as one set, and from the distribution diagram of Co concentration in each set, first, an average value Coa of Co content in the WC particle grains, The maximum Co content Comax at the boundary was calculated.

  And the group which has a grain boundary in which Comax / Coa is 1.2 or more was specified, and the percentage of the group in which the Co concentration of the grain boundary was 1.2 times or more in the grain of the WC particle was obtained. Sample No. No measurement was performed on 22 because there was no position where the Co content was 1 to 7% by mass.

  And after centerless-processing the outer peripheral part of this blank, it throws in in a joining apparatus at random, recognizes the direction of the protrusion part of a blank in a joining apparatus, and the edge part A and edge part B of each blank are the same A drill was produced by aligning the ends, bringing the end B of the blank into contact with the shank, joining them, and applying a cutting process to the portion including the end A of the blank.

About the obtained drill, the drilling test was done on the following conditions. The results are shown in Table 5.
(Drilling test conditions)
Work material: FR4, 0.8mm thickness, 3-ply drill shape: φ0.25mm
Rotation speed: 160krpm
Feed rate: 3.2 m / min Evaluation item: Number of drilled products (pieces) and drill flank wear width after testing (μm)

From Tables 1 to 5, Sample No. with Co _A equal to Co _B was obtained. In I-13, the flank wear width was large. In I-15, initial chipping occurred at the first hole due to insufficient sintering. _{Further, S Cr} is the same as _{S V, or} the sample _{S Cr} is greater than _{S V} No. In I-15 to I-21, the heat resistance and breakage resistance were low, and the number of processed parts decreased.

In contrast, Co _A and _{V A} is less than Co _B and _{V B, respectively,} smaller samples than _{S Cr} is _{S V} No. In I-1 to I-12, the flank wear width was small and the number of workpieces increased.

In particular, Sample No. with a ratio (Co _A / Co _B ) of 0.2 to 0.7. In I-1, I-2, I-6, I-7, and I-9 to I-12, the number of processed parts increased. In addition, while the ratio (V _A / V _B ) is 0.3 to 0.9 and the ratio (Cr _A / Cr _B ) is 0.8 to 1.1, Sample No. In I-1 to I-3 and I-6 to I-12, the number of processing was large.

Furthermore, sample no. _Each of I-1 to I-12 has a second region having a slope _S2Co and a first region having a slope _S1Co that is larger than the slope _S2Co , the flank wear width is small, and the number of workpieces is large. It was. In particular, Sample No. No. ₂ having a slope S _1Co of 0.2 to 1% by mass / mm and a slope S _{2Co of 0} to _0.2 % by mass / mm. In I-1, I-2, and I-6 to I-12, the number of processing was large. In addition, Sample No. in which the average particle diameter of the WC particles in the end portion A is larger than the average particle diameter of the WC particles in the end portion B. In I-1 to I-4 and I-6 to I-12, the flank wear width is small and the number of processed parts is large, and the average particle diameter of the WC particles at the end A is 0.3 to 1 respectively. The average particle size of the WC particles at the end B was 0.1 to 0.9 μm.

Furthermore, Cr _AO has a higher sample No. than Cr _A. In I-1, I-2, and I-5 to I-12, although not shown in the table, the corrosion resistance was high, and rust did not occur even after long-term storage.

Using the raw material powder used in Example 1, the compacts shown in Table 6 were produced and fired under the conditions shown in Table 7. And the drill was produced using this blank. About the obtained drill, the drilling test was done on the following conditions. The results are shown in Tables 7-10.
(Drilling test conditions)
Work material: FR4 material, 24-layer plate, 3.2 mm thickness, single drill shape: φ0.25 mm
Rotation speed: 160krpm
Feed rate: 3.2 m / min Evaluation item: Number of drilled products (pieces) and drill flank wear width after testing (μm)

From Table 6 to 10, Co _A and _{V A} is less than Co _B and _{V B, respectively,} smaller samples than _{S Cr} is _{S V} No. In II-1 to II-4, the flank wear width was small and the number of workpieces increased.

Using the raw material powder used in Example 1, the compacts shown in Table 11 were produced and fired under the conditions shown in Table 12. And the drill was produced using this blank. About the obtained drill, the drilling test was done on the following conditions. The results are shown in Tables 12-15.
(Drilling test conditions)
Work material: FP4 material, 0.06mm thickness, 10-ply drill shape: φ0.105mm
Rotation speed: 300krpm
Feeding speed: 1.8 m / min Evaluation item: Number of products that have been drilled (pieces) and flank wear width of the drill after the test (μm)

From Table 11 to 15, Co _A and _{V A} is less than Co _B and _{V B, respectively,} smaller samples than _{S Cr} is _{S V} No. In III-1 to III-3, the flank wear width was small and the number of workpieces increased.

  Sample No. For I-1, I-3 to I-6, I-13 to I-21, II-1 to II-5, III-1, III-2 and III-4, the surface of each sample was polished and polished A surface is prepared, and observation is performed in a field where 10 or more WC particles can be confirmed with the position where the Co content is intermediate between the Co content at the end A and the Co content at the end B being the intermediate part. It was.

  First, the Co content in this visual field was determined using TEM. Within this field of view, the concentration distribution of Co across the grain boundary from one WC particle to the inside of the adjacent WC particle was confirmed by EDX. Then, two adjacent WC particles and a grain boundary located between them are taken as one set, and from the distribution diagram of Co concentration in each set, first, an average value Coa of Co content in the WC particle grains, The maximum Co content Comax at the boundary was calculated.

  And the group which has a grain boundary in which Comax / Coa is 1.2 or more was specified, and the percentage of the group in which the Co concentration of the grain boundary was 1.2 times or more in the grain of the WC particle was obtained.

  From Table 16, Sample No. In I-13 to I-20, II-5, and III-4, the flank wear width was large and the number of workpieces was small.

  On the other hand, the Co content is 1 to 7% by mass, two adjacent WC particles and a grain boundary located between them are set as one set, and the grain boundary is sandwiched between 10 sets or more in one field of view. When the concentration distribution of Co across adjacent WC particles was measured, Sample No. having a region in which the set in which the Co concentration at the grain boundary was 1.2 times or more of the grains of the WC particles was 50% or more. In I-1, I-3 to I-6, I-21, II-1 to II-4, III-1 and III-2, the flank wear width was small and the number of workpieces was increased.

1 Drill (cutting tool)
2 Blank (blank for cutting tool)
3 Shank 5 Cutting edge 6 Groove 7 Neck 8 Body 11 First region 12 Second region 13 Third region 14 Fourth region 15 Protrusion 25 WC particle 27 Grain boundary 29 Region

Claims (12)

A long rod-shaped body made of a cemented carbide containing WC particles, Co, Cr and V, having a first end and a second end in the longitudinal direction,
The Co content in the first end is less than the Co content in the second end;
The V content at the first end is less than the V content at the second end;
From the first end toward the second end, the Cr content changes with the slope SCr, and the V content changes with the slope SV,
A rod-shaped body in which the inclined SCr is smaller than the inclined SV. The rod-shaped body according to claim 1, wherein the ratio of the Co content in the first end portion to the Co content in the second end portion is 0.2 to 0.7. The ratio of the V content at the first end to the V content at the second end is 0.3 to 0.9;
The rod-shaped body according to claim 1 or 2, wherein a ratio of a Cr content in the first end portion to a Cr content in the second end portion is 0.8 to 1.1. The rod-like body is located on the first end side, the first region in which the Co content is changed by the slope S1Co, and the Co end is located on the second end side. A second region in which the content changes with the gradient S2Co,
The rod-shaped body according to any one of claims 1 to 3, wherein the slope S1Co is larger than the slope S2Co.   The rod-shaped body according to claim 4, wherein the slope S1Co is 0.2 to 1 mass% / mm, and the slope S2Co is less than 0.2 mass% / mm.   The rod-shaped body according to any one of claims 1 to 5, wherein an average particle diameter of the WC particles at the first end portion is larger than an average particle diameter of the WC particles at the second end portion.   The average particle size of the WC particles at the first end is 0.3 to 1.5 µm, and the average particle size of the WC particles at the second end is 0.1 to 0.9 µm. The rod-shaped body described. The first end portion has an outer peripheral portion and a central portion located at least 100 μm from the outer peripheral portion,
The rod-shaped body according to any one of claims 1 to 7, wherein a content of Cr in the outer peripheral portion is larger than a content of Cr in the central portion. When an adjacent WC particle composed of two adjacent WC particles and a grain boundary located between the adjacent WC particles are taken as one set, the region has a plurality of positions.
When measuring the concentration of Co in the grain boundary and the concentration of Co in the adjacent WC particles in each of the 10 or more sets in one field of view of the region,
Co content is 1-7 mass%,
The rod-shaped body according to any one of claims 1 to 8, wherein a set in which the Co concentration in the grain boundary is 1.2 times or more of the Co concentration in the adjacent WC particles is 50% or more.   The rod-shaped body according to claim 9, wherein an average particle diameter of the WC particles in the region is 0.1 to 0.8 μm.   The rod-shaped body according to claim 9 or 10, wherein a standard deviation of a particle size distribution of the WC particles in the region is 0.5 µm or less. A long cutting tool made of a cemented carbide containing WC particles, Co, Cr and V, and having an end X having a cutting edge and an end Y located on the shank side in the longitudinal direction. ,
While the content of Co in the end X is less than the content of Co in the end Y,
The content of V at the end X is less than the content of V at the end Y,
From the end X toward the end Y, the Cr content changes with the gradient SCr, and the V content changes with the gradient SV,
A cutting tool in which the slope SCr is smaller than the slope SV.