JP2959065B2 - Sintered hard alloy drill - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a drill structure mainly used for drilling steel, and particularly to a sintered hard alloy having excellent wear resistance and toughness and high quality. It relates to the structure of the drill.

[Related Art] A drill is one of cutting tools used for drilling a steel material or the like. FIG. 7 shows an example of the structure of a twist drill. The twist drill is composed of a cutting edge portion 1 provided for drilling, a shank portion 2 not involved in cutting, and mainly for discharging chips and attaching to a chuck portion of a cutting machine such as a drilling machine. .

Conventionally, drills are generally made of high-speed steel (high-speed steel) and cemented carbide. High-speed steel is rich in toughness, but has low wear resistance and is unsuitable for high-speed cutting. On the other hand, a cemented carbide is excellent in wear resistance and precision characteristics as a tool, but has a brittle property. For example, when used in a machine tool having low rigidity, it may be broken.

These improvements include the use of hard TiN in the cutting edge of high-speed steel.
Or a structure in which the cutting edge is made of a cemented carbide and brazed.

In recent years, superalloys of different materials (P30 and D30) have been brazed (No. 58-143115) or metallurgically integrated to improve wear resistance and toughness. Structure (Japanese Utility Model Publication No. 62-46489),
Focusing on the difference in required characteristics between the center and the outer periphery of the drill, the drill is formed into a double structure in which the material of the cemented carbide is different between the center and the outer periphery (Japanese Patent Laid-Open No. 62-218010). issue),
Alternatively, a method of forming this double structure by injection molding (JP-A-63-38501 and 38502) has been devised. Further, there is a structure in which the material of the drill is made of cermet in order to improve the adhesion resistance of the drill (Japanese Patent Application Laid-Open No. 62-292307).

[Problems to be Solved by the Invention] The cutting edge portion and the shank portion of the drill are used under different load conditions. Therefore, the characteristics required for each part of the drill are different. For example, the cutting edge portion of the cutting edge portion is required to have wear resistance and adhesion resistance, and the shank portion is required to have toughness for maintaining strength as a tool. Also, the required characteristics of the cutting edge of the cutting edge part are also different because the cutting speed is largely different between the central part and the outer peripheral part.

In order to respond to the complicated requirements for the characteristics to be provided for such a drill, a coating with a cutting edge portion as a countermeasure, if re-grinding the drill as usual, at least the front relief lower surface side Of the coating layer is removed, and most of the effect of the coating is lost. In the case of brazing cemented carbide to the cutting edge, brazing itself is essentially a method of inferior thermal strength and mechanical strength, and cannot be applied to deep hole drilling of difficult-to-cut materials. Had disadvantages. Furthermore, in recent years, for the purpose of improving the toughness of the shank part of the drill, those made of coarse-grained cemented carbide or high-coupling phase have reduced the strength of the material or reduced the strain at the elastic limit. However, there is a problem that the shank portion is broken during drilling due to a deviation of the work material or unstable rotation of the cutting machine.

Then, this invention was made in order to solve the above-mentioned problems, and has excellent wear resistance and adhesion resistance at the cutting edge portion of the drill, and the shank portion has a breakage resistance. An object of the present invention is to provide a drill made of an alloy steel having necessary and sufficient toughness.

[Means for Solving the Problems] The sintered hard alloy drill according to the present invention comprises: (a) a cutting edge for cutting a workpiece; and (b) a cutting edge for mounting at a predetermined position on a cutting machine. And a shank part.

(A) Cutting blade part The cutting blade part is composed of cermet. This cermet consists of a first hard dispersed phase and a first bonded metal phase. The first hard dispersed phase is mainly composed of titanium and at least one of carbides, nitrides and double carbonitrides of metals of Groups IVa, Va and VIa of the Periodic Table excluding titanium. . The first bonding metal phase contains nickel and cobalt as main components. The composition of the first hard dispersed phase is (TiaMb) (CcN
d). M is one or more of metals belonging to Groups IVa, Va and VIa of the Periodic Table excluding Ti. a, b, c, and d indicate mole fractions. a, b, c, d are defined by the following relational expressions.

a + b = 1 c + d = 1 0.5 ≦ a ≦ 0.95 0.1 ≦ d ≦ 0.7 The first hard dispersed phase includes at least a group of fine particles and a group of coarse particles. The average particle size of the particles is 0.2μm or more and 0.6μ
m or less. The average particle size of the coarse particle group is 1 μm or more and 3 μm
It is as follows. The volume ratio of the fine particles to the coarse particles is
0.3 or more and 3 or less. The proportion of the first bonded metal phase in the cermet is 5% by weight or more and 30% by weight or less.

(B) Shank section The shank section is mechanically joined to the cutting blade section so as to be separable. The shank portion is made of an alloy steel.

(C) Method of joining the cutting edge and the shank A so-called throw-away type, which is mechanically joined so as to be separable by joining the cutting edge and the shank, is adopted.

As a general 2-flute indexable drill,
There are those as shown in FIGS. 1A to 1C. In this drill, the tip 31a is fixed to the outer peripheral portion of the cutting edge, and the tip 31b is fixed to the inner peripheral portion by screwing. Each of the chips has a chip breaker (not shown) for chip cutting at the tip of the cutting blade.

FIG. 2 shows a typical structure of a single-blade indexable drill. In the drill shown in the figure, a tip part 11 is fitted into a shank part 12 as shown by an arrow, and is fixed to a screw hole 14 by a screw 13. Coolant is supplied directly from the coolant supply hole 15 to the cutting edge of the tip portion 11, thereby enabling high-speed machining and extending the life of the blade.

As a single-flute indexable drill, a so-called self-grip insertion type drill is also conceivable. Since the cell grip does not need to be screwed, there is a possibility that the cell grip can be applied to a drill having a smaller diameter than the method shown in FIG.

In any of the above-described indexable drills, the tip portion having a relatively large damage and a short life can be disposable, so that the cost can be reduced as compared with an integrated body.

In addition, since a chip breaker can be easily formed on a chip, high-speed cutting and deep hole processing can be performed.

[Operation] The characteristics required of a drill are roughly classified into wear resistance and adhesion resistance of a cutting edge portion and breakage resistance represented by toughness of a shank portion. Of the characteristics required for these drills, the inventors of the present application apply a nitrogen-containing cermet containing titanium (Ti) as a main component to the cutting edge, paying particular attention to the improvement of wear resistance and adhesion resistance. I thought it was necessary. Therefore, experiments were conducted on various cermet compositions, and many effective findings were obtained. On the other hand, it has also been found that it is preferable to apply alloy steel to a shank portion of a drill requiring toughness and strength. The present invention has been made based on these findings, abrasion resistance to the cutting edge of the drill, applying a cermet excellent in adhesion resistance,
Further, an alloy steel having excellent toughness is applied to a shank portion, and a drill having a structure in which the two are mechanically joined to be separable is provided. Hereinafter, the reasons for limiting the composition, grain size, and the like of the sintered hard alloy drill according to the present invention will be described.

(A) Cutting edge part FIG. 8 shows a typical damaged part in a drill. 3
Is the area where the cohesive wear occurs on the inner circumference of the drill (rake face)
Is shown. As the rake surface wears due to the adhesion between the work material and the drill material, chips are attached and the life of the drill is extended.
Reference numeral 4 denotes a worn portion (margin) of the outer peripheral edge of the drill, and 5 denotes a chipping-occurring portion (front flank) of the cutting edge. In the present invention, the composition and particle size of the hard dispersed phase are limited in order to improve abrasion resistance and adhesion resistance.

The amount of titanium in the group of metal atoms contained in the hard dispersed phase is limited to the range of 0.5 to 0.95 by mole fraction. Below 0.5,
Abrasion resistance and adhesion resistance decrease. If it exceeds 0.95, the sinterability of the cermet itself deteriorates.

Such a high content of titanium lowers the affinity for iron, so that the finished surface of the workpiece containing iron is improved.

The proportion of nitrogen in the group of non-metallic atoms contained in the hard dispersed phase is limited to the range of 0.1 to 0.7 by mole fraction. If it is less than 0.1, the effect of suppressing the grain growth of the hard dispersed phase during the sintering of the cermet cannot be seen. Also, 0.
If it exceeds 7, the sinterability of the cermet itself deteriorates.

The hard dispersed phase consists of a mixture of fine particles having a particle size of 0.2 to 0.6 μm and coarse particles having a particle size of 1 to 3 μm. The volume ratio of the fine particles to the coarse particles is limited to the range of 0.3 to 3. If the volume ratio is less than 0.3, the toughness of the cermet itself deteriorates and chipping occurs at the cutting edge of the drill. In addition, this volume ratio is 3.0
Above, thermal cracks occur at the cutting edge of the drill.

The amount of bound metal phase is limited to the range of 5 to 30% by weight.
If the content is less than 5% by weight, the magnetism of the cermet itself becomes insufficient, and chipping occurs at the cutting edge of the drill. On the other hand, if it exceeds 30% by weight, abrasion resistance is insufficient, and large wear occurs on the flank of the cutting edge and the margin.

(B) Shank The alloy steel is used for the shank of the drill of the present invention. Since metal steel has a wide elastic deformation range, it exhibits excellent toughness even with a slight impact and is hard to break. Steel is roughly classified into carbon steel, alloy steel, and high alloy steel. In the present invention, considering both wear resistance and workability, alloy steel (for example, nickel chromium molybdenum steel, chromium molybdenum steel, Steel, etc.). In the case of a plug-in type single-flute indexable drill, it is necessary to particularly consider elasticity, and spring steel or the like is used. In addition, for the shank, generally, alloy steel that can be easily manufactured is used,
Since a sintered hard alloy requiring a complicated manufacturing process is used only for the cutting edge, manufacturing costs can be reduced,
It is also advantageous in price.

[Example] Hereinafter, an example of the present invention will be described.

The sintered hard alloy drill according to the present invention is formed by using a cermet alloy for the cutting edge portion and using an alloy steel for the shank portion and mechanically joining them so that they can be separated. The cermet alloy constituting the cutting edge is prepared by mixing various powders so that the composition of the hard dispersed phase, the composition of the binder phase, and the particle size existence ratio of the hard dispersed phase become the values shown in Table 1 after sintering. It was made by doing. As the alloy steel constituting the shank portion, those having the materials shown in Table 1 were used.

FIG. 3 shows the particle size distribution of the hard dispersed phase in the cermet alloy forming the cutting edge of the drill. A shows the abundance distribution of fine particles, and B shows the abundance distribution of coarse particles. The volume ratio of fine particles to coarse particles is the first in A / B
It is represented in the table.

The product of the present invention and the comparative product shown in the following examples use a drill made of a sintered hard alloy having a diameter of 16 mm obtained by the joining method shown in FIG.

Table 1 shows the composition and particle size distribution of the hard alloy of the sintered hard alloy drill of the present invention and the drills manufactured for comparison. In Table 1, the comparison product F
Is produced so that the non-metal atomic ratio and the particle size abundance ratio of the hard dispersed phase of the cutting edge portion are outside the range of the present invention as indicated by *. The comparative product G was manufactured so that the amount of the bonded metal phase in the cutting edge portion was out of the range of the present invention. Comparative product H uses a K30 grade cemented carbide outside the scope of the present invention as the shank portion.

Each numeral outside the scope of the present invention is marked with *.

The performance evaluation test of the drill was performed under the following conditions.

Test Conditions Workpiece: S50C (H _B = 230) Cutting Speed: 120 m / min, wet (water soluble cutting oil) Feed rate: 0.15 mm / rev Depth:. 35 mm criteria: after processing to life, the cutting edge situation Observe etc.

Life: Usually, when the wear amount of the outer peripheral surface becomes 0.2 mm or more.

The results of the drill performance evaluation test are shown in Table 2. Referring to Table 2, first, in the comparison between inventive products A and B and comparative product F, in comparative product F, the toughness of the cermet constituting the cutting edge portion was deteriorated, and the cutting edge portion was chipped.

Next, in the present invention, in comparison of A and B with Comparative Product G, it was found that Comparative Product G had a deeper inner rake surface adhesion wear depth and was inferior in adhesion resistance.

Further, in the comparison between the products A and B of the present invention and the comparative product H, the comparative product H was inferior in shank strength, and the shank portion was broken.

Furthermore, the products C, D, and E of the present invention also showed almost the same good performance as the products A and B of the present invention from a comprehensive viewpoint.

In addition to these inventive products and comparative products, the present performance test was also performed on a coated high-speed steel or coated carbide drill currently used for reference.
In comparison between these drills and the drills of the present invention A, B, C, D and E, it is clear that the performance of the drill of the present invention is excellent.

The joining method of the product of the present invention and the comparative product in the above embodiment is based on the method shown in FIG.
It has been experimentally confirmed that the results shown in FIGS.

[Effects of the Invention] As described above, in the present invention, a drill using a cermet alloy having a specific composition excellent in wear resistance, adhesion resistance or heat crack resistance (chipping resistance) is used for a cutting edge of a drill. The drill is formed by mechanically joining both of them using a tough and relatively low-cost alloy steel for the shank portion. Therefore, a drill made of a sintered hard alloy having high reliability, long life and high quality without causing sudden breakage or the like can be provided at low cost.

[Brief description of the drawings]

FIG. 1A is a front view showing an example of a two-flute indexable drill, FIG. 1B is a right side view thereof, and FIG. 1C is an enlarged perspective view showing the tip thereof. FIG. 2 shows a drill applied to the sintered hard alloy drill of the present invention.
FIG. 2 is an exploded perspective view of a single-blade screw-down indexable drill. FIG. 3 is a distribution diagram showing a particle size distribution of a hard dispersion layer in a cermet alloy constituting a cutting edge portion of a drill according to the present invention. FIG. 4 is a structural view showing a general twist drill. FIG. 5 is a view showing a typical damaged portion of a drill. In the figure, 1,11,31a, 31b are cutting edge portions, and 2,12,32 are shank portions.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B23B 51/00 B23B 27/14 C22C 29/02

Claims (1)

(57) [Claims] 1. A sintered hard alloy drill provided with a cutting blade for cutting a workpiece and a shank for attaching the cutting blade to a predetermined position of a cutting machine, wherein the cutting blade comprises titanium; Periodic Tables IVa, Va and VI Excluding Titanium
a first hard dispersed phase mainly composed of at least one of carbides, nitrides and double carbonitrides of a group a metal, and a first bonded metal phase mainly composed of nickel and cobalt. Wherein the composition of the first hard dispersed phase is (TiaMb) (CcNd)
[However, M is the Periodic Table IVa, Va and VIa excluding Ti
A, b, c, and d are mole fractions, a + b = 1, c + d = 1, 0.5 ≦ a ≦ 0.95, 0.1 ≦
d ≦ 0.7], wherein the first hard dispersed phase comprises at least a group of fine particles having an average particle size of 0.2 μm or more and 0.6 μm or less and a group of coarse particles having an average particle size of 1 μm or more and 3 μm or less. A volume ratio of the fine particle group to the coarse particle group is 0.3 or more and 3 or less; and a ratio of the first binding metal phase in the cermet is 5% by weight or more and 30% by weight or less. A drill made of a sintered hard alloy, wherein the drill is made of alloy steel and mechanically joined to the cutting blade so as to be separable.