JPH0343112A - Drill made of sintered hard alloy - Google Patents

Abstract

PURPOSE:To provide high reliability, long life, and high quality by monolithically joining a knife edge part and a shank part using cermet alloy having a specific composition excellent in abrasion resistance, adhesion resistance, and thermo cracking resistance in the knife edge part, and WC cemented carbide having excellent toughness in the shank part. CONSTITUTION:A cutting edge part 1 is composed of cermet consisting of a first hard dispersed phase and a first coupling metal phase having the main component of nickel and cobalt and accounting for 5-30 weight percent of the whole. When a, b, c, and d are made a mole fraction with one kind or more of a periodic table, IVa, Va, and VIa group metal except Ti as M, the composition of a first hard dispersed phase is represented as (TiaMb) (CcNd) and the following equations are effected: a+b=1, c+d=1, 0.5<=a<=0.95, and 0.1<=d<=0.7, and the volume ratio of a particulate group having a mean grain diameter of 0.2-0.6mum to a coarse grain group having a mean grain diameter of 1-3mum is made 0.3-3. A shank part 2 is monolithically joined with the cutting edge part 1, and composed of a second hard dispersed phase of a WC grain having a mean grain diameter of 0.7mum or below and a second coupling metal phase containing Co acounting for 13-30 volume percent of cemented carbide to increase toughness.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the structure of a drill mainly used for drilling steel, and in particular to a drill made of a high-quality sintered hard alloy with excellent wear resistance and toughness. This concerns the structure of the drill.

[Prior Art] A drill is one of the cutting tools used for drilling holes in steel materials and the like. As an example, the structure of a twist drill is shown in FIG. The twist drill consists of a cutting blade part 1 used for drilling, and a shank part 2 that does not participate in cutting but mainly serves to discharge chips and is attached to a chuck part of a cutting machine such as a drill press. .

Conventionally, the material of the drill inside the shell is high-speed steel (HSS).
and cemented carbide. Although high-speed steel has high toughness, it has low wear resistance and is unsuitable for high-speed cutting. On the other hand, although cemented carbide has excellent wear resistance and precision characteristics as a tool, it is brittle and may break when used in, for example, machine tools with low rigidity.

As an improvement to these, hard TiN was added to the cutting edge of high-speed steel.
A structure in which the cutting edge is made of cemented carbide and brazed to it has been considered.

Furthermore, in recent years, with the intention of improving wear resistance and toughness, structures in which cemented carbide of different quality (P2O and D30) are brazed together (Utility Model Application Publication No. 58-143115) or metallurgically integrated have been introduced. Structure that is bonded (Jikko 62-46)
489), and by focusing on the difference in required characteristics between the center and outer periphery of the drill, we developed a double-structured drill with different cemented carbide materials for the center and outer periphery (No. 489). JP-A No. 62-218010), or a method of forming this double structure by injection molding (JP-A No. 63-38501,
No. 38502), etc. have been devised.

In addition, in order to improve the adhesion resistance of the drill, we have developed a structure in which the drill is made of cermet (Japanese Patent Laid-Open No. 62-29230
7) etc.

[Problems to be Solved by the Invention] The cutting edge portion and the shank portion of a drill are used under different load conditions. Therefore, the characteristics required for each part of the drill are different. For example, the cutting edge of the cutting edge requires wear resistance and adhesion resistance, and the shank requires toughness to maintain the strength of the tool. Further, since the cutting speed of the cutting edge portion of the cutting edge portion is greatly different between the center portion and the outer peripheral portion, the characteristics required are also different.

In order to meet these complex requirements for the characteristics that a drill should have, there are some products that have been coated on the cutting edge. This has the disadvantage that at least the coating layer on the front and rear surfaces is removed, and most of the coating effect is lost. In addition, for those with a structure in which cemented carbide is brazed to the cutting edge, brazing itself is a method that inherently has inferior thermal and mechanical strength, and cannot be applied to deep hole machining of difficult-to-cut materials. It had the following drawback. Furthermore, in recent years, in order to improve the toughness of the shank of a drill, cemented carbide has been made coarser grained or has a higher bonding phase, but this has conversely reduced the strength of the material or caused strain at the elastic limit. There was a problem in that the shank part could break during drilling due to vibration of the material to be cut or unstable rotation of the cutting machine.

Therefore, this invention was made to solve the above problems.The cutting edge of the drill has excellent wear resistance and adhesion resistance, and the shank has excellent breakage resistance. It is an object of the present invention to provide a drill made of a sintered hard alloy having sufficient toughness.

[Means for Solving the Problems] A sintered hard alloy drill according to the present invention includes (a) a cutting blade portion for cutting a workpiece, and (b) a cutting blade portion for attaching to a predetermined position of a cutting machine. and a shank part.

(a) Cutting Edge The cutting edge is made 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 one or more carbides, nitrides, and polycarbonitrides of metals from groups IVa, Va, and VIa of the periodic table excluding titanium. The first bonding metal phase has nickel and cobalt as main components. The composition of the first hard dispersed phase is (Ti aMb)
(CcNd). M is the first V a of the Zhou Ming Table excluding Ti.

One or more of group Va and VIa metals. a, b.

c and d indicate the molar fraction. a, b, c, d
is defined by the following relational expression.

a+b fight 1 c+dm1 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 diameter of the fine particles is 0.2 μm or more.
It is 6 μm or less. The average particle diameter of the coarse particle group is 1 μm or more and 3 μm or less. 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 binding metal phase in the cermet is 5% by weight or more and 30% by weight or less.

(b) Shank portion The shank portion is integrally joined to the cutting edge portion. The shank portion is made of cemented carbide. The cemented carbide consists of a second hard dispersed phase of WC particles and a second bonded metal phase containing Co. The average particle size of the second hard dispersed phase is 0.7 μm
It is as follows. The second binding metal phase occupies 13% by volume or more and 30% by volume or less in the cemented carbide.

[Function] The properties required of a drill are broadly divided into wear resistance and adhesion resistance of the cutting edge, and breakage resistance represented by toughness of the shank. Among the characteristics required for these drills,
In particular, with a focus on improving wear resistance and adhesion resistance, the inventors of the present invention came up with the idea that it is essential to apply a nitrogen-containing cermet containing titanium (Ti) as a main component to the cutting edge.

Therefore, we conducted experiments on various cermet compositions and obtained many useful findings. On the other hand, it has also been found that it is preferable to apply WC-based cemented carbide to the shank portion of a drill, which requires toughness and strength.

The present invention was made based on these findings,
A cermet with excellent wear resistance and adhesion resistance is applied to the cutting edge of the drill, and a WC-based cemented carbide with excellent toughness is applied to the shank, both of which are integrated into one. A drill having a joined structure is provided. The reasons for limiting the composition, grain size, etc. in the sintered hard alloy drill according to the present invention will be explained below.

(a) Cutting edge part The state of wear in the drill is shown in FIG.

Reference numeral 11 indicates a portion (rake face) where adhesive wear occurs on the inner circumference of the drill. As the rake face wears down due to adhesion between the workpiece and the drill material, chips will adhere to it and the drill will reach the end of its life. 12 is the wear area (margin) of the drill peripheral cutting edge, 13
indicates the part where chipping occurs on the cutting edge (front transparent surface). In this invention, the composition and particle size of the hard dispersed phase are limited in order to improve wear resistance and adhesion resistance.

The amount of titanium in the metal atom group contained in the hard dispersed phase is 0. It is limited to a range of 5 to 0.95. 065
If it is less than that, abrasion resistance and adhesion resistance will decrease. Also,
If it exceeds 0.95, the sinterability of the cermet itself deteriorates.

The proportion of nitrogen in the nonmetallic atomic group contained in the hard dispersed phase is limited to a range of 0.1 to 0.7 in molar fraction. If it is less than 0.1, nitrogen will not have the effect of suppressing grain growth of the hard dispersed phase during sintering of cermet. Moreover, when it exceeds 0.7, 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 fine particles to coarse particles is 0.3
-3.

This volume ratio is 0. If it is less than 3, the toughness of the cermet itself deteriorates and chipping occurs at the cutting edge of the drill. Moreover, if this volume ratio exceeds 3.0, thermal cracks will occur at the cutting edge of the drill.

The amount of bound metal phase is limited to a range of 5-30% by weight.

If it is less than 5% by weight, the toughness of the cermet itself will be insufficient and chipping will occur on the cutting edge of the drill. Also, 30
If it exceeds this weight percent, wear resistance will be insufficient and large wear will occur on the transparent surface and margin of the cutting edge.

(b) Shank Part For the shank part of the drill of the present invention, a WC-based cemented carbide containing WC particles with an average particle size of 0.7 μm or less as a hard dispersed phase is used. When high-speed steel or the like is used, since its coefficient of thermal expansion is large, a cutting edge is likely to occur in the cutting edge due to a difference in thermal expansion between the cutting edge and the cermet. Furthermore, the Young's modulus of high-speed steel is about 173 compared to that of WC-based cemented carbide, which has poor vibration resistance during cutting, which promotes wear and chipping of the cutting edge.

If the average particle size of the hard dispersed phase exceeds 0.7 μm, the strength of the shank portion of the drill will not be sufficient to satisfy the breakage resistance. If the amount of the bonding metal phase is less than 13% by volume, the toughness will decrease, and if it exceeds 30% by volume, plastic deformation will occur, which is not preferable.

[Example] Examples of the present invention will be described below.

The sintered hard alloy drill according to the present invention is formed by using a cermet alloy for the cutting edge part and a WC cemented carbide for the shank part, joining them during powder forming press, and sintering them. The cermet alloy that constitutes 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 abundance ratio of the hard dispersed phase become the values shown in Table 1 after sintering. It was created by The cemented carbide forming the shank part is W with an average grain size of 0.5 μm.
It was produced by blending C powder and Co powder so that the binding metal (volume %) and hard dispersed phase average particle size (μm) became the values shown in Table 1 after sintering. At this time, a small amount of VC powder was added as a grain growth inhibiting component.

Note that FIG. 2 shows the particle size distribution of the hard dispersed phase in the cermet alloy that constitutes the cutting edge of the drill. A shows the frequency distribution of fine particles, and B shows the frequency distribution of coarse particles. The volume ratio of the fine particles to the coarse particles is expressed in Table 1 as A/B.

The cermet alloy powder constituting the cutting edge portion and the cemented carbide powder constituting the shank portion were joined during the powder forming press. Specifically, using a hydrostatic press, so-called CIP (Cold l5ostatic Pr)
Each alloy powder was bonded before sintering. Thereafter, the obtained compact was sintered to produce a sintered hard alloy in which the cermet alloy and the cemented carbide were integrally joined. A drill with a diameter of 10 mm was obtained by grinding each sample.

In addition, as a comparison product, a 10 mm diameter drill was manufactured in the same manner as above by changing the particle size and blending ratio of the powder as shown in Table 1.

Table 1 shows the composition and particle size distribution of the hard alloy of the sintered hard alloy drill of the present invention and a drill prepared for comparison. In Table 1, the comparative products were manufactured so that the composition and particle size abundance ratio of the hard dispersed phase in the cutting edge were outside the range of the present invention, as indicated by *.

Comparative product E was manufactured so that the particle size of the hard phase constituting the shank portion was outside the range of the present invention.

Furthermore, comparative product F was manufactured so that the particle size abundance ratio of the hard dispersed phase constituting the cutting edge portion was outside the range of the present invention. Comparative product G was manufactured so that the amount of the bonded metal phase in both the cutting edge portion and the shank portion was outside the range of the present invention. Comparative product H was manufactured so that the amount of the bonded metal phase constituting the cutting edge portion was outside the range of the present invention. Values outside the scope of the present invention are marked with *.

(Left below) Performance evaluation tests for the drill were conducted under the conditions shown below.

Test conditions Work material: 550C (Ha = 230) Cutting speed: 60
m/min, wet (water-soluble cutting oil) feed rate: 0. 25
mm/rev.

Depth: 25mm Judgment criteria: After machining to the end of its life, observe the condition of the cutting edge.

Lifespan: (a) Defined when the amount of wear on the front and back surfaces of the outer periphery reaches 0.2 mm or more.

The results of the above drill performance evaluation test are shown in Table 2. Referring to Table 2, first, in a comparison between products A to C of the present invention and the comparison product, the toughness of the cermet constituting the cutting edge portion of the comparison product deteriorated, and chipping occurred at the cutting edge portion. .

Further, in a comparison between products A-C of the present invention and comparative product E, comparative product E was inferior in shank strength, and the shank portion was broken.

In a comparison between products A-C of the present invention and comparative products F and G, the toughness of the cermet in Comparative products F and G was insufficient, and the cutting edge of the drill was chipped.

In a comparison between products A-C of the present invention and comparative product H, comparative product H
The wear resistance was insufficient, and the cutting edge showed a certain amount of wear even after a small number of holes were drilled.

Furthermore, for reference, the performance test was also conducted with coated high speed steel or coated carbide drills that are currently in use. In comparing these drills with drills A to C of the present invention, it is clear that the drills of the present invention have superior performance.

(The following is a blank space) [Effects of the Invention] As described above, in the present invention, a cermet having a specific composition that has excellent wear resistance, adhesion resistance, or heat cracking resistance (chipping resistance) is used at the cutting edge of a drill. The drill is formed by using a WC cemented carbide, which has high toughness, in the seat part of the drill, and integrally joining these two together. Therefore, it is possible to provide a sintered hard alloy drill that is highly reliable, has a long lifespan, and has high quality without causing any accidental breakage.

[Brief explanation of drawings]

FIG. 1 is a structural diagram showing an in-shell twist drill. FIG. 2 is a distribution diagram showing the particle size distribution of the hard dispersed phase in the cermet alloy constituting the cutting edge portion of the drill according to the present invention. FIG. 3 is a diagram showing typical damaged parts of the drill. In the figure, 1 is a cutting edge portion, and 2 is a shank portion. Fig. 2 Fig. 2 Niji-rich incense P

Claims (1)

[Claims] A sintered hard alloy drill comprising a cutting edge for cutting a workpiece and a shank for attaching to a predetermined position of a cutting machine, the cutting edge being made of titanium. , Periodic Table IVa, Va and V excluding titanium
A first hard dispersed phase whose main component is one or more carbides, nitrides, or double carbonitrides of Group Ia metals; and a first bonded metal phase whose main components are nickel and cobalt. The composition of the first hard dispersed phase is (TiaMb) (Cc
Nd) [However, M is one or more metals from Groups IVa, Va, and VIa of the periodic table excluding Ti, a, b, c, and d indicate molar fractions, a+b=1, c+d=1, 0.5≦a≦
0.95, 0.1≦d≦0.7], and the first
The hard dispersed phase has an average particle size of 0.2 μm or more and 0.6
A group of fine particles of 1 μm or less and an average particle size of 1 μm or more and 3 μm
m or less, the volume ratio of the fine particles to the coarse particles is 0.3 or more and 3 or less, and the first binding metal phase accounts for 5% by weight in the cermet. % or more and 30% by weight or less, and the shank portion is integrally joined to the cutting edge portion and is a cemented carbide comprising a second hard dispersed phase of WC particles and a second bonding metal phase containing Co. The second hard dispersed phase has an average particle size of 0.7 μm or less, and the second binding metal phase accounts for 13% by volume or more and 30% by volume or less in the cemented carbide. A sintered hard alloy drill characterized by: