JP2006131975A - Cermet for saw blade - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cermet for a saw blade superior in not only abrasion resistance but also fracture resistance. <P>SOLUTION: The cermet for the saw blade comprises a binder phase and a hard phase. The binder phase is formed of an iron group metal mainly including Co and Ni, and has an average thickness of 0.35 to 0.50 μm. The hard phase is mainly formed of carbonitrides of one or more metals selected from the group consisting of Ti and W, which are indispensable, and Ta, Nb, Mo, Hf, V and Cr. The total weight of Ni and Co is 15 to 25 mass%, a Ti content is 30 to 50 mass%, a W content is 15 to 30 mass%, and the total content of Ta, Nb, Mo, Hf, V and Cr is 5 to 15 mass%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cermet for a saw blade. In particular, the present invention relates to a cermet for a saw blade that is excellent in fracture resistance and suitable for a saw blade for metal processing.

  A metal cutting saw having a plurality of chips fixed to the outer periphery of a substrate is known. In this method, a plurality of blades are formed on the outer periphery of a disk-shaped substrate, and a chip made of cermet or cemented carbide is brazed to the blades. Such saws are required not only to have wear resistance but also to have chipping resistance.

  Of the materials used for this chip, WC-based cemented carbide, which is a typical cemented carbide, is excellent in fracture resistance, but often lacks wear resistance and has a long tool life. On the other hand, titanium carbonitride-based alloys, which are typical cermets, are superior in oxidation resistance and wear resistance compared to WC-based cemented carbides, and are widely used as cutting tools. However, conventional cermets have the disadvantage of being easily lost.

For example, the techniques described in Patent Document 1 and Patent Document 2 are known as techniques mainly aimed at improving this defect. In Patent Document 1, when observed with a scanning electron micrograph, the particles of the hard phase in the alloy include a black core portion that appears black and a peripheral structure that appears gray around the black core portion. A TiCN-based alloy having is disclosed. Then, in this alloy, the distribution of the area of the black core portion, a first peak existing in the range of 0.1 [mu] m ² or more 0.7 [mu] m ² or less, the second existing in the range of 0.8 [mu] m ² or more 2.5 [mu] m ² or less By including the peak, the wear resistance and fracture resistance are improved. On the other hand, Patent Document 2 discloses a TiCN-based cermet in which a hard phase is composed of a black first hard phase and an off-white second hard phase in a scanning electron micrograph of an arbitrary cross section. Then, by specifying the average particle size of the first hard phase and the second hard phase and the area ratio of each hard phase in each of the inside and the surface portion of the cermet, the fracture resistance and the wear resistance are improved. .

Japanese Patent Laid-Open No. 10-298697 JP 2004-115881 A

  However, even with the above prior art, it is difficult to achieve both high wear resistance and high fracture resistance sufficiently, and as a cermet used for saw blades for metal processing, etc., it is even more resistant. There is a need for improved deficiencies.

  Accordingly, a main object of the present invention is to provide a saw blade cermet which is excellent not only in wear resistance but also in fracture resistance.

  In order to find a chip material suitable for a saw blade, the inventors of the present invention have a cermet having not only a wear resistance equivalent to or higher than that of a conventional cermet but also a fracture resistance equivalent to that of a cemented carbide. As a result of examining and testing the conditions, the present invention has been completed.

  The present invention is a saw blade cermet comprising a binder phase and a hard phase. The binder phase is made of an iron group metal mainly composed of Co and Ni, and has an average thickness of 0.35 to 0.50 μm. The hard phase is essentially composed of carbonitride containing Ti and W as essential components and one or more selected from the group consisting of Ta, Nb, Mo, Hf, V and Cr as metal components. And the total amount of Ni and Co is 15 to 25% by mass, the content of Ti is 30 to 50% by mass, the content of W is 15 to 30% by mass, Ta, Nb, Mo, Hf, V and The total content of Cr is 5 to 15% by mass.

  When the cross section of the conventional cermet is observed with a scanning electron microscope, a state in which the hard phase particles 20 are dispersed in the binder phase 10 is observed as shown in FIG. These hard phase particles include hard phase particles having a cored structure and hard phase particles having a non-core structure. The hard-phase particles having a cored structure are composed of black core particles 21 that are located at the core and appear black and peripheral structures 22 that appear gray around the black core particles. On the other hand, hard-phase particles having a non-core structure can be seen as hard-phase particles consisting essentially of black core particles 21 and hard-phase particles consisting essentially only of the surrounding structure 22.

  In such a structure, the size of the hard phase particles is different in the conventional cermet, and as a result, the thickness of the binder phase is small, which is thought to be a factor that hinders the improvement of fracture resistance. .

  Therefore, as a result of various investigations, the present inventors mainly (1) specify the amount of the binder phase, and (2) reduce the hard phase particles consisting only of the black core particles as much as possible to reduce the hard phase with a core structure. By increasing the number of particles, the thickness of the binder phase is increased and the fracture resistance of the cermet is improved. In addition, the wear resistance is maintained by adopting a cermet structure in which precipitation of WC, which has a lower hardness than Ti carbide, nitride and carbonitride, is suppressed. That is, as shown in FIG. 3, the cermet of the present invention is configured such that the number of fine black core particles 21 that tend to be the starting point of fracture is reduced and the thickness of the binder phase 10 is increased.

  Hereinafter, the present invention will be described in more detail.

  The cermet of the present invention is composed of a binder phase and a hard phase.

First, the binder phase is composed of an iron group metal mainly composed of Co and Ni. Typically, a material composed of Ni, Co, and the balance of inevitable impurities is used for the binder phase. Moreover, the average thickness of this binder phase shall be 0.35-0.50 micrometer. This is because if the average thickness of the binder phase is less than the lower limit, it is difficult to sufficiently improve the fracture resistance, and conversely if it exceeds the upper limit, the wear resistance is reduced. This average thickness is obtained using a photograph taken with a scanning electron microscope in an area 0.5 mm or more from the cermet surface. In other words, an arbitrary line segment is drawn in the 14.4 μm × 18.7 μm (substantially 270 μm ² ) field of view of this micrograph, the total length of the binder phase on that segment is L, and the total number of binder phases on that segment is L / Nt when Nt is taken as the average thickness of the binder phase. However, the measurement is performed so that a plurality of visual fields are obtained and the total length L of line segments in each visual field is 118 μm or more and the total number Nt is 50 or more.

  Next, the hard phase is essentially composed of carbonitride containing Ti and W as essential components and one or more selected from the group consisting of Ta, Nb, Mo, Hf, V and Cr as metal components. For example, Ti carbide, nitride, carbonitride may be used as the main component of the hard phase. These are the main factors that determine the hardness and strength of the cermet. In addition, as an essential component of the hard phase, W carbide, nitride, and carbonitride are listed. These have the effect of improving the wettability between the hard phase and the binder phase and increasing the strength. The hard phase additive component includes carbides, nitrides, and carbonitrides of one or more metal components selected from the group consisting of Ta, Nb, Mo, Hf, V, and Cr. Typically, the main component is Ti carbonitride. Of the additive components, Ta and Nb are preferably selected as the metal components. Ta, Nb carbides, nitrides, and carbonitrides have the function of strengthening the hard phase and can contribute to the improvement of the wear resistance of the cermet.

  In the cermet comprising the above binder phase and hard phase, the contents of various metal components are specified as follows.

  First, the total amount of Ni and Co is set to 15 to 25% by mass. When the total amount of Ni and Co is less than 15% by mass, the amount of the binder phase is small, and it is difficult to improve the fracture resistance by forming a binder phase having a sufficient average thickness. On the other hand, if the amount exceeds 25% by mass, the amount of the binder phase becomes too large, leading to a decrease in wear resistance. Thus, it becomes easy to obtain the cermet with the large average thickness of the above-mentioned binder phase by relatively increasing the content of the binder phase. The Ni and Co contents are the total mass% of Ni and Co in the entire cermet. The content is measured by pulverizing the sintered cermet with a pulverizer and analyzing the pulverized material with, for example, ICP (inductively coupled plasma emission analysis). This content is the proportion of the entire cermet and the measurement method is the same for the content of other metal components.

  Next, the content of Ti is set to 30 to 50% by mass. If the Ti content is less than 30% by mass, it will be difficult to sufficiently produce a hard phase such as TiCN, and it will be difficult to obtain the required wear resistance. If it exceeds 50% by mass, the fracture resistance will be inferior. .

  Further, the W content is 15 to 30% by mass. W has the effect of improving the wettability between the hard phase and the binder phase and increasing the strength as WC, but the W content is set to 15 to 30% by mass in order to affect the wear resistance.

  Furthermore, the total content of Ta, Nb, Mo, Hf, V and Cr is set to 5 to 15% by mass. These usually have a hard phase strengthening function as carbides, nitrides, carbonitrides and the like. If it falls below the specified lower limit value, the fracture resistance tends to decrease, and if it exceeds the specified upper limit value, the wear resistance is inferior and the reaction with the work material tends to be high.

In addition, in a scanning electron micrograph of an arbitrary cross section in this cermet, it is preferable that the number of black core particles, which are hard phases having a black core, is 200 or less within a visual field of 270 μm ² . By reducing the number of fine black core particles, the hard phase composed of the surrounding structure is relatively increased, and the toughness of the cermet is improved. Moreover, it contributes to increasing the average thickness of the binder phase by reducing the fine black core particles. The number of black core particles is determined by measuring the number of black core particles from five or more visual fields in a 270 μm ² visual field within 0.5 mm or more from the cermet surface, and taking the average value.

  In that case, the ratio Na / N of the number Na of black core particles of 1 μm or more to the total number N of black core particles is preferably 0.13 to 0.55. By specifying the ratio Na / N, the balance between fracture resistance and wear resistance can be controlled. If this ratio Na / N is less than 0.13, the fracture resistance tends to decrease, and if it exceeds 0.55, the wear resistance tends to decrease. The black core particles having a size of 1 μm or more are black core particles having a maximum length of 1 μm or more.

  Further, the ratio Nb / Na of the number Nb of 1 μm or more black core particles having an aspect ratio of 1.0 to 2.0 with respect to the number Na of black core particles of 1 μm or more is preferably 0.50 or more. By increasing the number of rounded black core particles having a relatively small aspect ratio, stress concentration can be avoided and toughness can be improved. The aspect ratio is represented by Lmax / Lmin, where Lmax is the longest length of black core particles and Lmin is the shortest length. Then, the ratio Nb / Na is obtained for 100 or more black core particles of 1 μm or more.

  The cermet of the present invention is usually obtained by preparing material powder → mixing and grinding material powder → press molding → sintering.

  First, at the stage of preparing the material powder, it is desirable that the ratio of TiCN having an average particle diameter of 1 μm or less in the hard phase powder used as a raw material, particularly TiCN, is 30% by volume or less. As a result, a state where a large number of fine black core particles are dispersed is avoided, and the average thickness of the binder phase is increased to improve toughness.

  In the stage of sintering, it is preferable to perform sintering at 1450 to 1600 ° C., for example. In particular, sintering at 1500 ° C. or higher is preferable. Sintering at a relatively high temperature allows hard phase particles to grow and re-solidifies elements such as Ti in the hard phase, preventing fine black core particles from being dispersed in the binder phase To do.

  Then, by specifying the proportion of TiCN having an average particle size of 1 μm or less and limiting the sintering temperature, the aspect ratio can also be controlled, and a cermet having a proportion Nb / Na of 0.50 or more can be obtained. .

  The cermet of the present invention can be a cermet having improved toughness and excellent fracture resistance by mainly increasing the average thickness of the binder phase. Moreover, wear resistance can also be improved by using a hard phase in which precipitation of WC is suppressed.

  Embodiments of the present invention will be described below.

The raw material powders shown in Table 1 were mixed according to the formulation shown in the table, the mixed powder was pressed into a predetermined shape, and then sintered in the N ₂ atmosphere under the conditions shown in the table. Here, the proportion of TiCN having an average particle diameter of 1 μm or less in the raw material TiCN ((volume of TiCN having an average particle diameter of 1 μm or less) / (volume of all TiCN)) is 30% by volume or less in the examples. However, the comparative example is more than 30% by volume. About the obtained sintered body, the content of the metal component, the average thickness of the binder phase, the number of black core particles, the number Na of black core particles of 1 μm or more to the total number N of black core particles Na / N, 1 μm The ratio Nb / Na of the number Nb of black core particles of 1 μm or more having an aspect ratio of 1.0 to 2.0 with respect to the number Na of black core particles was determined. The results are shown in Table 2.

The content of the metal component was determined by pulverizing the sintered cermet with a pulverizer and analyzing the pulverized material with ICP (inductively coupled plasma emission analysis). The average thickness of the binder phase (simply expressed as “Binder Layer Thickness” in Table 2) is obtained using a photograph taken with a scanning electron microscope at a region 0.5 mm or more from the cermet surface. Drawing an arbitrary line segment in the 14.4 μm x 18.7 μm (substantially 270 μm ² ) field of view of this micrograph, L / Nt when the total length of the binder phase on the line segment is L and the total number is Nt The average thickness of the binder phase. However, the measurement is performed by using a plurality of visual fields so that the total length of the line segments L in each visual field is 118 μm or more and the total number Nt of binder phases on the same line segment is 50 or more. The number of black core particles was determined by measuring the number of black core particles from five or more of the above visual fields. The ratio Na / N was determined by dividing the above black core particles into those having a maximum length of 1 μm or more and those other than that. For the ratio Nb / Na, the maximum length of the black core particles was Lmax, the minimum length was Lmin, and Lmax / Lmin was the aspect ratio.

  Further, scanning micrographs of No. 1-6 as an example and No. 2-1 as a comparative example are shown in FIGS. 1 and 2, respectively. In the photograph of FIG. 1, black portions are black core particles, surrounding gray portions are surrounding tissues, and white portions are binder phases. As is clear from this photograph, it can be seen that in the examples there are few fine black core particles and there are many hard phases mainly composed of surrounding structures. In particular, there are few fine black core particles dispersed only in the black core particles and dispersed in the binder phase in the absence of surrounding tissue. In the examples, it can be seen that many of the black core particles are round and have a small aspect ratio. Further, the precipitation of WC observed in the photograph of FIG. 2 described below is not recognized in the photograph of FIG.

  On the other hand, in the photograph of FIG. 2, the part that appears black is black core particles, the part that appears gray is the surrounding tissue and the binder phase, and the part that appears white is WC. In the photo in Fig. 1, the binder phase looked white, but in Fig. 2, it is difficult to distinguish the surrounding tissue, WC, and binder phase in a single photo because of the contrast. As a result, the surrounding tissue and the binder phase are gray and are indistinguishable. As is apparent from the photograph in FIG. 2, precipitation of WC having a low hardness is observed in the comparative example. In addition, there are many black core particles, and there are many black core particles that are thin and have a large aspect ratio. Note that the size of the black core particles is the diameter of only the black portion in the above photograph, and the diameter of the particles including the surrounding tissue is not measured even if it is a hard phase particle having a centered structure.

  Further, a circular saw having a diameter of 305 mm and a number of blades of 54 was produced using each obtained cermet as a chip, and a cutting test was performed. Cutting conditions are as follows.

Work material: STK400 plated pipe (outer diameter 48.6mm, wall thickness 2mm)
Rotation speed: 1500r.pm
Cutting time: 3-5 seconds / cut Number of cuts: ~ 60 cuts

  The fracture resistance was evaluated from the number of cuts required until half of the total number of blades were missing.

  Further, cutting was performed under the following conditions, and the wear resistance was evaluated from the average amount of wear of the maximum worn portion of each chip.

Work material: S15CK round bar (outer diameter 50mm)
Rotation speed: 1500r.pm
Cutting time: 25-60 seconds / cut Number of cuts: 45 cuts

  These test results are also shown in Table 2.

  As is apparent from the above table, all of the inventive examples (No. 1-1 to No. 1-6) are excellent in both wear resistance and fracture resistance. On the other hand, when the amount of the metal component was out of the predetermined range or the average thickness of the binder phase was out of the predetermined range, the fracture resistance was lowered.

  The cermet of the present invention can be suitably used for a saw blade tip. In particular, it can be suitably used for a saw blade tip for metal processing.

It is a scanning electron micrograph of Example No. 1-6. It is a scanning electron micrograph of Comparative Example No. 2-1. It is a schematic diagram which shows an Example structure | tissue. It is a schematic diagram which shows a comparative example structure | tissue.

Explanation of symbols

  10 Bonded phase 20 Hard phase 21 Black core particle 22 Surrounding structure

Claims (4)

A saw blade cermet consisting of a binder phase and a hard phase,
The binder phase is made of an iron group metal mainly composed of Co and Ni, and has an average thickness of 0.35 to 0.50 μm,
The hard phase is essentially composed of carbonitrides containing Ti and W as essential components and one or more selected from the group consisting of Ta, Nb, Mo, Hf, V and Cr as metal components,
The total amount of Ni and Co is 15-25% by mass,
Ti content is 30-50% by mass,
W content is 15-30% by mass,
A cermet for a saw blade, wherein the total content of Ta, Nb, Mo, Hf, V and Cr is 5 to 15% by mass.   The cermet for a saw blade according to claim 1, wherein the metal component selected from the group consisting of Ta, Nb, Mo, Hf, V and Cr is Ta and Nb. In a scanning electron micrograph of an arbitrary cross section in this cermet,
In the visual field of 270 μm ² substantially, there are 200 or less black core particles that are hard phases having a black core,
2. The cermet for a saw blade according to claim 1, wherein the ratio Na / N of the number Na of black core particles of 1 μm or more to the total number N of black core particles is 0.13 to 0.55.   The saw blade according to claim 3, wherein the ratio Nb / Na of the number Nb of 1 μm or more black core particles having an aspect ratio of 1.0 to 2.0 to the number Na of black core particles of 1 μm or more is 0.50 or more. Cermet for.

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