JP2008144541A - Drilling bit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drilling bit which is used in the fields of civil engineering, construction, etc., and has a blade having superior impact resistance, abrasion resistance, brazing property, etc. <P>SOLUTION: The drilling bit is constructed by fixing the blade made of a cemented carbide tip (3) to the front end of a steel shank (2). The cemented carbide tip (3) is a laminated cemented carbide tip made by bonding together a plurality of types of cemented carbide tips having different compositions via a bond (5) infiltrating through a binder metal of the cemented carbide tips. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an excavation bit such as a cutter bit in a shield machine.

  For example, a cutter bit of a shield machine is generally a cemented carbide chip (hereinafter referred to as “carbide chip” or “chip”) as a hard blade to a shank (base metal) made of steel. It is. Since the shield machine is used for underground tunnel excavation and the like, it is necessary that the cutter bit not only has high cutting performance such as earth and sand but also has a high strength that is not easily damaged during excavation. This is because if the blade is lost during excavation, not only the cutting performance is remarkably lowered, but also other blades are damaged by the fragments, and the cutter bit is easily replaced during excavation in the basement. Therefore, the cemented carbide tip constituting the blade body is particularly required to have excellent impact resistance and wear resistance.

  The cemented carbide is obtained by dispersing hard metal carbide particles in a binder metal matrix. As the metal carbide particles, WC, TiC, TaC or the like is used, and as the metal forming the binder layer, Co, Ni, Fe, or the like is generally used, which is used for a civil engineering cutter bit. As the cemented carbide tip, a WC-Co alloy having relatively high toughness is most widely adopted.

  In general, cemented carbide has finer carbide particles (WC, etc.), and the smaller the binder layer (cobalt Co layer, etc.), the higher the hardness and the better the wear resistance. Conversely, the carbide particles are coarser and there are many binder layers. The higher the toughness (strength), the better the impact resistance. That is, the hardness and strength of the cemented carbide are conceptually contradictory, and usually a cemented carbide chip according to the application is obtained by adjusting the carbide particle size and the amount of the binder layer.

  The cutting performance and wear resistance of the cutter bit are improved by increasing the hardness of the blade. However, as described above, a hard tip with high hardness has a drawback that it is easily damaged by impact, so various measures have been taken to achieve both wear resistance and impact resistance, such as combining multiple types of carbide tips. Has been made. Examples thereof include those shown in the following patent documents.

JP 2006-241681 A Japanese Patent No. 3780941 JP-A-9-78986 Japanese Utility Model Publication No. 5-16897

  The one described in Patent Document 1 is a cutter bit in which a soft tip made of a cemented carbide and a hard tip are brazed to a base material with a joining material interposed therebetween. A material similar to an alloy and made of a softer material than the soft tip is used. The cutter bit maintains wear resistance with a hard tip, and shocks are buffered with a soft tip, thereby achieving a long life.

  Further, the one described in Patent Document 2 is an excavation cutter bit provided with a hard tip at the tip, and the tip is implanted in a plurality of stages from the tip to the base end. At least some of the chips in the steps have different grades and hardnesses from those of the other steps, and have different lengths from the other steps.

  Further, the one described in Patent Document 3 is a cutter bit such as a shield machine, and is a multilayer formed by brazing a plurality of layers of carbide chip pieces having different materials such as hardness and toughness with a copper plate interposed therebetween. A chip is used as a blade, which is brazed to a steel base metal.

  Further, the one described in Patent Document 4 is a cutter bit of a tunnel digging machine in which hard chips and soft chips are alternately stacked and fixed to the cutter bit body.

  Although the thing of the said patent document 1 is what fixedly integrated the hard chip | tip, the soft chip | tip, and steel materials mutually by brazing, it needs a troublesome trouble to braze several layers simultaneously. Moreover, since the cemented carbide chip is vulnerable to thermal shock, there is a possibility that micro cracks may be caused by brazing. In addition, there is a problem that residual stress due to brazing is liable to be lost during use and peeling between the brazing material layer and the cemented carbide tip is likely to occur.

  For example, when brazing a cemented carbide tip to a base metal, the same amount of compressive stress and tensile stress are applied to the base metal and the carbide tip. The gold and the cemented carbide chip share and absorb, and the remaining stress remains in the brazing layer and can be balanced. On the other hand, when the material of the cemented carbide tip is hard, since the absorption of stress is reduced, the cemented carbide tip can be balanced by being broken. For this reason, it is difficult to braze a hard carbide chip without damaging it. In order to cope with such a problem, it is considered to divide the carbide chip into smaller pieces and braze in advance, but in this case, defects such as dropping off from the brazed portion are likely to occur. Thus, there are various problems in brazing a cemented carbide tip.

  Next, the thing of the said patent document 2 is the thing which transplanted the several chip | tip from which a material kind differs in the step shape in the hole drilled in the base metal, It is what is brazed. Specifically, a round bar-like chip is inserted into the circular hole. However, in this configuration, the stacked chips are concentrically arranged and brazed, and then fixed to the bottom of the base metal by brazing or by press-fitting. In the case where each chip is fixed by brazing, there may be a problem due to cracks or residual stress.

  Similar to Patent Document 1, those described in Patent Document 3 and Patent Document 4 are obtained by integrating a plurality of carbide chips by brazing, and these are also the same problems as those described in Patent Document 1 have. In addition to the above, a method of fixing a plurality of chips by pulse energization has been considered, but all have strength problems and are not suitable for severe use conditions such as excavation bits.

  Therefore, the present invention improves the above-mentioned conventionally known technique and adopts a joining method that is superior in strength to brazing to produce a cemented carbide tip having both wear resistance and impact resistance. It is an object to provide a long-life excavation bit with a blade.

  In order to solve the above problems, the present invention has the following configuration. That is, the excavation bit according to the present invention is an excavation bit in which a cemented carbide tip is fixed to the tip of a steel shank, and the cemented carbide tip includes a plurality of types of cemented carbide tips having different compositions. The cemented carbide chip is characterized by being a laminated cemented carbide chip bonded and integrated through a bonding material that penetrates into the binder metal of the cemented carbide chip.

  As the cemented carbide tip, it is preferable to use a WC-Co alloy. Further, as a bonding material for bonding the cemented carbide chips to each other, a binder metal that forms a matrix of the cemented carbide alloy is preferable, and cobalt is more preferable.

  The excavation bit according to the present invention is obtained by adhering a laminated carbide chip in which a plurality of chips of different material types are laminated and fixed to the blade edge as a blade body. And impact resistance can be provided. In addition, since the chips are fixed using a binder metal used in cemented carbide as a bonding material instead of brazing, they are superior in strength compared to the case where the chips are fixed together by brazing and cracks due to residual stress. Problems such as occurrence are less likely to occur. Further, since the chips can be fixed to each other by using a heating device such as an electric furnace, a troublesome work such as brazing work is not required, and stable fixing can be performed.

  Hereinafter, embodiments of the present invention will be specifically described. FIG. 1 shows a cutter bit which is a kind of excavation bit. In this bit 1, a laminated cemented carbide chip 3 is fixed as a blade body to a tip portion of a shank (base metal) 2 made of steel. ing. The laminated carbide chip 3 is brazed to the shank 2 at the bottom and the rear surface in a state where the laminated carbide chip 3 is fitted in a stepped notch recess 2 a formed at the tip of the shank 2. In this illustrated example, three laminated carbide chips 3 are fixed side by side in a plan view, but this is to reduce the residual stress of each chip when brazed to the shank 2, and more chips. The blade body may be formed by being divided into two, and when the size of the blade body is small, the blade body may be constituted by one or two chips.

  All the grades of the laminated cemented carbide chip 3 shown in FIG. 1 are WC-Co based cemented carbide, and a superhard cemented chip 3a is superposed on a cemented carbide chip 3b having a lower hardness. It is a chip having a two-layer structure which is joined and integrated. In the embodiment of FIG. 1, the material type of the cemented carbide tip 3a used for the cutting edge portion of the excavating bit 1 is a WC-Co based cemented carbide having a relatively high hardness, such as E3 type defined by JIS. It is. Further, the material type of the impact resistant cemented carbide tip 3b that supports the cemented carbide tip of the blade edge portion is a WC-Co based cemented carbide having relatively high toughness, such as E5 class defined by JIS. As described above, it is possible to achieve both wear resistance and impact resistance by laminating and integrating a plurality of types of carbide chips of different materials.

  In the example of FIG. 1, the cutting edge and the wear resistance are kept good by using a high hardness tip 3a at the cutting edge portion of the excavation bit 1 that requires wear resistance, and brazing is performed only with the high hardness tip. Therefore, brazing and impact resistance are ensured by using a relatively tough tip 3b having a relatively low hardness on the base side of the bit 1. Conversely, if the upper (blade edge) cemented carbide tip is a soft tip 3b and the lower tip is a hard tip 3a, it is resistant to impact at the start of excavation and is damaged even if it collides with gravel during excavation. Hard to do. Moreover, after the excavation has progressed, the work can be excavated for a long time with the lower chip 3a after the upper chip 3b is worn under the working condition where there is no risk of collision.

  In the present invention, as described above, as a method of superimposing a plurality of cemented carbide chips by overlapping and joining and integrating, a method of heating in a vacuum furnace or the like by sandwiching the bonding material 5 between the cemented carbide chips instead of brazing. There is a feature in the point to adopt. That is, by superposing a plurality of cemented carbide chips having a desired property on both sides of a bonding material and heating to a temperature equal to or higher than the melting point of the bonding material, the bonding material is bonded to the cemented carbide chip on both sides of the bonding material. It diffuses and penetrates into the (matrix). Thereby, the cemented carbide chips on both sides are joined and integrated via the joining material layer. The thickness of the bonding material layer in the bonded state is preferably about 0.1 to 2 mm (a metal foil can be used). It is useless that the thickness of the bonding material layer is too large, and the bonding strength also decreases. In the embodiment of FIG. 1, two cemented carbide chips are joined and integrated. However, in the case of three or more cemented carbide chips, the cemented material can be similarly joined by heating.

  As the bonding material 5, a binder metal used for holding carbide particles with a cemented carbide, for example, cobalt, nickel, iron, or the like can be used. Since the bonding material 5 is melted by heating and penetrates into the matrix of the cemented carbide, it is preferable to use the same type of binder metal used for the cemented carbide chip to be bonded. In the case of the illustrated example, it is preferable to use cobalt as the bonding material 5 because the material type of the cemented carbide chip is a WC-Co based cemented carbide.

For reference, in order to investigate the toughness of the laminated cemented carbide chip obtained by bonding, a test piece specified in JIS was cut out, and the bending strength by three-point bending was examined by placing the bonding portion in the center. When the E3 type chip and the E5 type chip were joined, the bending strength was 2913 N / mm ^{2 to} 3007 N / mm ² . On the other hand, the bending strength of a test piece in which cemented carbide chips having a single bending strength of 3000 N / mm ² are joined together by conventional brazing is 830 to 1100 N / It was mm ^2. As in the present invention, when cemented carbide chips are joined using a cemented carbide binder metal as a binder, it can be seen that strength superior to that of the conventional brazing method can be obtained.

  Next, the excavation bit 1 shown in FIG. 2 is configured with three carbide tips arranged in a plan view in the same manner as in FIG. 1, and each tip is shown in a side view. The front end side (front side) S and the base side (rear side) K are divided and integrated by a bonding material. They are not stacked one above the other. The bonding surface is an inclined surface T, and even if the thickness of each chip is small, the bonding area is larger than the case of bonding on a surface perpendicular to the upper surface, so that the bonding strength is increased. In this configuration, if the tip S is a soft carbide tip 3b and the base K is a hard tip 3a, it is advantageous when there is a risk of collision with gravel at the start of excavation (start). . The size of the tip S on the tip side may be adjusted according to the distance to be excavated. On the contrary, if the tip S is a hard carbide tip 3a and the base tip K is a soft tip 3b, there is no risk of collision at the start of excavation, and there is a risk of collision when the excavation progresses Is advantageous.

  FIG. 3 shows an example in which a plurality of laminated carbide chips are arranged at intervals. In the illustrated bit, a hard chip 3a is arranged on the tip side S and a soft chip 3b is arranged on the base side K, and both are integrated by a bonding material. This is also advantageous when there is no risk of collision at the start of excavation (start) and there is a risk of collision later. Conversely, if a soft tip 3b is arranged on the tip side S and a hard tip 3a is arranged on the base side K, there is a risk of collision at the start, and it is predicted that there is no risk of collision thereafter. Is advantageous.

  The embodiment of FIG. 4 is the same as the illustrated example of FIG. 3 except that the tip side tip 3a and the base side tip 3b are joined at an inclined joining surface. In this case, since the bonding area becomes large, a relatively large bonding strength can be obtained. FIG. 5 shows an example in which a hard carbide chip 3a is surrounded by a soft carbide chip 3b among a plurality of carbide chips 3 arranged at intervals. This example is also advantageous when there is a danger of a collision at the start and there is no danger of a collision when the excavation progresses.

  As described above, the excavation bit according to the present invention has a cemented carbide tip, which is a blade body, bonded and integrated with a bonding material that penetrates a plurality of different types of carbide tips into the binder metal of the carbide tip. The laminated carbide tip thus made can be combined with wear resistance and toughness, and can be adapted well even when the ground conditions change during excavation.

  The excavation bit according to the present invention can be effectively used as a blade body of a cutter bit for tunnel excavation, for example.

It is the top view (a) and side view (b) showing an example of the bit for excavation concerning this invention. It is the top view (a) and side view (b) of the bit for excavation different from the above. Furthermore, it is the top view (a) and side view (b) of another excavation bit. Furthermore, it is the top view (a) and side view (b) of another excavation bit. Furthermore, it is the top view (a) and side view (b) of another excavation bit.

Explanation of symbols

1 Drilling bit 2 Shank 3 Carbide tip 5 Bonding material

Claims (2)

A drilling bit comprising a cemented carbide tip fixed to the tip of a steel shank, wherein the cemented carbide chip penetrates a plurality of types of cemented carbide chips having different compositions into the binder metal of the cemented carbide chip. A drill bit characterized in that it is a laminated cemented carbide chip bonded and integrated through a bonding material. The laminated cemented carbide chip according to claim 1, wherein the composition of the cemented carbide chip constituting the laminated cemented carbide chip is a WC-Co based cemented carbide and the bonding material is cobalt.

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