JPS6133645B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a drill used for drilling holes in cast iron or steel materials, and particularly to a cemented carbide drill using cemented carbide as a material. [Conventional technology and its problems] High-speed steel drills have traditionally been used for drilling work in general steel materials, cast iron, etc., but recently there has been a strong demand for improved efficiency in drilling work. Increasingly, the number of rotational speeds of drills is increased to meet this demand, and as a result, cemented carbide, which has excellent wear resistance, is increasingly used as a drill material. However, compared to high-speed steel, cemented carbide has inferior transverse rupture strength, slow cutting speed, and the cutting edge at the center of the drill, which has a large negative rake angle, is likely to break. For this reason, it was necessary to use a material with high strength among cemented carbides, or in other words, material with poor wear resistance, and as a result, it was extremely difficult to prevent wear on the outer periphery of the drill, where the cutting speed was high. Therefore, attempts have been made to improve the wear resistance of the rake face and outer peripheral margin by providing a hard coating grown on the surface by chemical vapor deposition (for example, Japanese Patent Application Laid-Open No. 56-3118, In this method, the hard coating may peel off, and the coating itself is very thin, so long-term storage with good wear resistance cannot be expected. [Means for Solving the Problems] The present invention solves the inherent problem of drills that if either toughness or wear resistance is emphasized, the chip velocity differs between the center and the outer periphery. This was done in view of the current technology of carbide drills, which requires sacrificing the other or providing a hard coating that has problems with the sustainability of the effect. This is a solution from this point of view. That is, the drill of the present invention has two or more layers divided into a central part where the cutting speed is slow and requires toughness rather than wear resistance, and an outer peripheral part where the cutting speed is fast and where emphasis is placed on wear resistance. The drill is characterized by the fact that the drill is composed of composite and metallurgically integrated cemented carbide alloys that have properties that match the required characteristics of each part. In the above, the cemented carbide with properties that meet the required properties of the partition layer means that the one that forms the center of the drill is a strong alloy, while the one that is coaxially arranged and assembled around the outer periphery of the drill core is a strong alloy. , refers to an alloy that has higher wear resistance (hardness) than the cemented carbide in the center, and when there are multiple layers around the center layer, the outer layers have higher hardness. The specific selection of this material can, for example, make the drill center
When using JIS V3 cemented carbide with high transverse rupture strength shown in column E of Table 1, use M40 cemented carbide on the outside and P20 cemented carbide on the outside. In this way, the selected materials are composited.

〔Example〕

An example is shown in FIGS. 1 and 2. This drill 1 has a central part 2 that spans the entire length, for example, JIS
The outer peripheral part 3 surrounding the center part 2 is made of tough cemented carbide such as P40, and is made of JIS
A high-hardness cemented carbide such as P20 is used, and a chisel blade 4 and a cutting blade 5 continuous to this blade are made of the cemented carbide in the center.
On the other hand, the remaining part of the cutting edge 5 and the margin part 6 are formed in the cemented carbide of the outer peripheral part. The material of the center portion 2 and the material of the outer peripheral portion 3 are integrally joined by the first method among the methods described above in order to eliminate insufficient bonding force and interfacial peeling after bonding. That is, in FIG. 3, the cylindrical body 2a of tough cemented carbide forming the center and the cylindrical high-hardness cemented carbide layer 3a concentrically arranged around the outer periphery of the material before main sintering are both preliminary. Sintered. This material is used as it is or is pre-processed into a shape close to the shape of a drill and then subjected to main sintering to form a thermal diffusion layer of each component at the contact interface between the cylindrical body 2a and the layer 3a. after that,
If necessary, by placing the main sintered material in a high-temperature, high-pressure gas for a certain period of time, the cavities formed at the bonding interface can disappear, and the drill material 1a obtained in this way can be freed from chips by grinding and polishing. After forming the discharge groove 7, the cutting edge, and the margin, the illustrated drill is completed. In addition, in the case of a drill, due to the difference in cutting speed,
The optimum hardness and toughness of the cutting edge differ in each part in the radial direction. Therefore, in order to optimize the material of the drill, it is desirable to laminate more layers of different types of cemented carbide whose wear resistance increases gradually toward the outer layer. [Effects] The drill of the present invention configured as described above has excellent wear resistance at the outer periphery, which is subject to severe wear during normal drilling, so overall wear is reduced, while the center part is strong and has excellent wear resistance. This prevents the center cutting edge from breaking and ensures sufficient drill strength, making it possible to perform highly efficient machining through high-speed rotation with a large thrust force applied. If the outer high-hardness cemented carbide layer is divided into more layers, the material in each radial direction will more closely approximate the optimal material, so the effect will be more pronounced. In addition, instead of providing a false coating to improve wear resistance, materials that meet the required characteristics are coaxially composited at each radial part of the cutting edge, resulting in excellent wear resistance and long-term connectivity. , wear resistance does not decrease even if the cutting edge is regenerated by re-polishing. Furthermore, since the cemented carbide layers are firmly integrated through the thermal diffusion layer at the interface, there is no risk of interfacial peeling or abnormal wear caused by insufficient bonding force at the joint.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an embodiment of the drill of the present invention, FIG. 2 is a front view thereof, and FIG. 3 is a perspective view showing the drill material before being subjected to groove and cutting processing. 1...Drill, 2...Center, 3...Outer periphery,
4... Chisel blade, 5... Cutting blade, 6... Margin section, 7... Chip discharge groove.

Claims (1)

[Claims] 1. The drill material consists of a combination of a tough cemented carbide forming the center of the drill and one or more layers of cemented carbide harder than the core cemented carbide disposed coaxially around the outer periphery, and Each cemented carbide layer is
It is a structure in which the components are integrally combined through a heat diffusion layer formed at each contact interface, and a chip discharge groove, a cutting edge, and a margin are formed in this drill material. A carbide drill featuring the following.