JP2000296410A - End mill made of composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an end mill made of composite material the surface of which is hard and has wear resistance and the inside of which has high toughness. SOLUTION: A cutting part 12 constituting this end mill 10 has two cutting edges 18 extending from both ends of an end face cutting edge 16. A metal part 20 rich in metal is provided in the end mill inside of the cutting part 12, a ceramics part 22 rich in ceramics is provided on the end mill surface, and between these parts, an inclined part 24 in which the rate of metal component is gradually decreased from the end mill inside toward the end mill surface, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite end mill comprising a composite material containing a ceramic component and a metal component.

[0002]

2. Description of the Related Art Generally, in various machining fields,
Groove processing and flat or end face processing using an end mill are performed. During this type of machining operation, various stresses act on the end mill. For example, there are a compressive stress when applying a pressing force to the cutting material, a tensile stress acting on the biting portion and the cutting portion, and a tensile stress between a portion to be processed and a portion not used for the processing.
For this reason, cutting by an end mill is likely to be unstable in practice, and may cause chipping, chipping, breakage, or a decrease in dimensional accuracy of a machined portion, resulting in high hardness, high strength and high toughness. There is a demand for an end mill having the same. Therefore, high-speed steel, carbide, and the like are generally widely used as the material of the end mill.

[0003]

However, although high-speed steel has high strength and high toughness, it has problems in wear resistance, compressive strength and rigidity, whereas carbides have high rigidity, high hardness and high rigidity. Although it has compressive strength, there is a problem in toughness. In other words, toughness and strength deteriorate when trying to improve rigidity and wear resistance, but rigidity and hardness decrease when trying to improve strength and toughness. Is extremely difficult in practice.

At this time, various measures have been taken to apply a surface treatment such as hard coating to the superhard material or high-speed steel. However, the accuracy of the edge of the end mill decreases, and the coating peels off under high load stress or high temperature. And so on, and could not be put to practical use.

[0005] In view of the above, when the development of an end mill having high hardness and abrasion resistance in the vicinity of the surface of the end mill where cutting is actually performed and having high strength inside the end mill was studied, Japanese Patent No. 2593354, filed by the present applicant, It has been found that a “composite material having a gradient function containing a ceramic powder and a metal component” disclosed in JP-A-8-127807 and the like is applied.

That is, an object of the present invention is to provide an end mill made of a composite material having a tilting function in which physical properties such as toughness and strength are improved as the surface goes toward the inside with high hardness.

[0007]

The end mill made of a composite material according to the present invention is composed of a composite material containing a ceramic component and a metal component. The end mill in the composite material moves from the inside of the end mill to the end mill surface. The ratio of the metal component is gradually decreasing. Here, there is a correlation between the proportion of the metal component in the composite material and the hardness, strength, and toughness. When the proportion of the metal component decreases and the proportion of the ceramic component increases, the hardness, wear resistance, rigidity, and the like are improved. But it becomes brittle. On the other hand, when the proportion of the metal component is increased to improve the brittleness, the strength and the toughness are improved, but the rigidity and the wear resistance are reduced.

In view of this, the surface of the end mill where the actual processing is performed is made of a material having high hardness and wear resistance, and the inside of the end mill is made of a material having high toughness and high strength. By gradually changing the composition and physical properties of the end mill, it is possible to obtain an end mill having a sharp cutting edge with high dimensional accuracy while maintaining desired wear resistance without stress concentration.

Therefore, the ceramic particles in the vicinity of the surface of the end mill promote the grain growth as compared with the inside and become coarser and become smaller toward the inside, and the metal components are accumulated inside by the rearrangement of the particle composition accompanying the grain growth. You. Therefore, the composition of the surface of the end mill that is actually processed is ceramic-rich and has high wear resistance, the inside of the end mill is metal-rich and has high strength and high toughness, and stress concentration inside the end mill is effectively reduced. Becomes possible.

[0010] Further, since the vicinity of the surface of the end mill where the cutting is actually performed is made rich in ceramics and the particles are coarsened, the transmission and diffusion of heat generated near the surface of the end mill during cutting are improved. Therefore, the generation of microcracks due to heat is prevented, and the resulting chipping and constituent edges are improved, so that the cutting performance is greatly improved.

[0011]

FIG. 1 is a partial sectional side view of a composite end mill 10 according to a first embodiment of the present invention, and FIG. 2 is a longitudinal sectional front view of the end mill 10. As shown in FIG.

The end mill 10 constitutes a two-flute end mill, and has a blade portion 12 and a shank portion 14 integrally. The blade portion 12 has an end face cutting edge 16 at the tip of the cutting edge, and two cutting edges 18 are provided from both ends of the end face cutting edge 16 at a predetermined twist angle in the axial direction (the direction of arrow A). ing. The end mill 10 is made of a composite material containing a ceramic component and a metal component. A metal-rich metal portion 20 is provided inside the end mill, and a ceramic-rich ceramic portion 2 is provided on the end mill surface.
2 are provided. An inclined portion 24 is provided between the metal portion 20 and the ceramic portion 22 so that the ratio of the metal component gradually decreases from the inside of the end mill toward the end mill surface.

The metal component is at least one selected from the group VIII elements of the periodic table, iron (Fe), nickel (Ni) and cobalt (Co), and if necessary, chromium (Cr), vanadium ( V), manganese (M
n), molybdenum (Mo) or tungsten (W) is mixed. The ratio of the metal component in the composite material is 3 wt%
~ 15wt%, more preferably 5wt% ~ 10wt%
Is set within the range.

If the metal component is less than 3% by weight, the amount of metal becomes too small, and the end mill 10 becomes brittle, and cannot be used in practice. When the metal component is 3 wt% or more, the ratio of the metal component on the surface side of the end mill 10 can be set to 1 wt% or less, and the metal component of about 8 wt% can be relatively accumulated inside the end mill. It can be put to practical use. In addition,
When the end mill 10 is manufactured by performing processing such as cutting after the sintering of the material, it is necessary to consider the strength of the cutting edge, and it is desirable that the ratio of the metal component is 5 wt% or more.

Here, when a powder material of about 2 μm is used as the ceramic particles, the particles near the end mill surface vary depending on the added particle growth agent, sintering temperature, time, atmosphere, etc. It grows about 30 times. In the end mill 10, when the strength of the cutting edge 18 is required, the cutting blade 18 is grown up to about 3 to 6 times, while when the wear resistance is mainly required, it is grown up to about 10 to 20 times. . At this time, the ratio of the metal component near the surface of the end mill 10 is about 1 wt% to 5 wt%, and the ratio of the metal component inside the end mill 10 changes depending on the growth degree, the thickness of the inclined portion 24, and the like. 5 near
In the case of wt%, it is about 8 wt% to 13 wt% or more inside.

The upper limit of the ratio of the metal component is set to 15 wt%, more preferably 10 wt%. For example, in processing on a broaching machine or the like or deep hole processing, a long end mill 10 similar to a gun drill is used, and high rigidity and high strength are required, and particularly, high tensile strength is required. In this case, when trying to avoid breakage or the like by increasing the amount of the contained metal component, the ratio of the metal component is 15 watts.
If it exceeds t%, the abrasion resistance may be deteriorated.

Further, in an end mill 10 having a metal component ratio of 15 wt% and a metal component of about 5 wt% in the vicinity of the surface, if it is attempted to secure a hardness of about HRA 93, the diameter of the end mill 10 is about 25 mm. If the size is large, the metal component at the center of the end mill is 20 wt.
% Or more, and has a toughness close to that of high-speed steel and is functionally sufficient.

In the end mill 10 having a diameter of about 10 mm to 20 mm, as described above, in order to make the amount of the metal component at the center of the end mill about 20 wt% or more,
It is sufficient that the ratio of the metal component in the composite material is set to 10 wt%. Even if the metal component is added at a higher ratio, it does not contribute to strength or toughness, and the rigidity of the entire end mill 10 is reduced. .

The thickness of the inclined portion 24 of the end mill 10 is set to several hundred μm, preferably 0.3 mm or more.
In the end mill 10, there is a correlation between the amount of the metal component and the heat conduction and the particle size and the heat conduction, and the generated thermal stress becomes a gradient of the heat transfer. Changes. When the thickness of the inclined portion 24 is several μm to several tens μm, the amount of relaxation of the generated thermal stress and the stress at the time of processing is small, and a desired effect cannot be obtained even if the ratio of the metal component is appropriately controlled.

On the other hand, it is conceivable to set the thickness of the inclined portion 24 to be large, but the end mill 10 becomes large in diameter. The diameter of a practical end mill 10 is 25 mm
The upper limit of the thickness of the inclined portion 24 is 10 m
Set to m.

The ceramic components in the composite material constituting the end mill 10 include tungsten carbide (WC), titanium carbide (TiC), molybdenum carbide (Mo ₂ C), tantalum carbide (TaC), niobium carbide (NbC), and carbon carbide. It is mainly composed of at least one selected from chromium (Cr ₃ C ₂ ) or vanadium carbide (VC), and various kinds of nitrides, borides or carbonitrides may be used as necessary. You may add to a part.

The amount of ceramic is 85 wt% ≦ WC + T
iC + Mo ₂ C + TaC + NbC + Cr ₃ C ₂ + VC ≦
It is set to 97 wt%. These ceramic components constitute the cutting edge 18 that actually performs cutting when cutting by the end mill 10, and have properties such as heat resistance, wear resistance, and corrosion resistance. If the amount of ceramics exceeds 97 wt%, the amount of the metal component becomes too small, and the wear resistance is sufficient, but the strength and toughness are reduced, and it is difficult to put to practical use.

On the other hand, if the ceramic component is less than 85% by weight, the metal component becomes too large, and when used after dressing the end mill 10, the wear resistance may be significantly deteriorated. The surface hardness of the end mill 10 is HRA88 or more. Below this value, the cutting edge 18 of the end mill 10
In addition, the exposure ratio of the metal component increases, the coefficient of friction (μ) with the work material increases, causing an increase in heat generation, the work surface of the work material becomes rough, and the cutting edge 18 of the end mill 10 itself Wear will be increased.

As described above, the end mill 10 according to the first embodiment is advantageous in physical properties as compared with the high-speed steel, and the machining accuracy and the machining surface are effectively improved. Moreover, the frequency of replacing the end mill 10 is reduced,
Good use over a long period of time becomes possible. In addition, in the end mill 10, by appropriately selecting a grain growth agent, for example, when nickel is used as a metal component, the surface hardness of the end mill 10 becomes HRA94 and further HRA98, and the hard ceramic coating is applied. Is obtained.

FIG. 3 is a partial cross-sectional side view of a composite end mill (four-flute end mill) 10a according to a second embodiment of the present invention, and FIG. 4 is a sectional view showing a third embodiment of the present invention. It is a partial cross-sectional side view of such a composite end mill (straight-edge end mill) 10b. FIGS. 5, 6 and 7 show,
FIG. 10 is a partial cross-sectional side view of composite end mills (two-, three- and four-blade spiral end mills) 10c to 10e according to fourth, fifth and sixth embodiments of the present invention.
The same components as those of the end mill 10 according to the above-described first embodiment are denoted by the same reference numerals, and the detailed description thereof is omitted.

The end mills 10a-
In 10e, the same effects as those of the end mill 10 according to the first embodiment are obtained, such as that high-speed machining is easily performed as compared with an end mill made of high-speed steel or carbide. Example 1 In Example 1, 89 wt% of tungsten carbide (WC) powder having an average crystal grain size of 2.2 μm, 2 wt% of niobium carbide (NbC) powder having an average grain size of 2 μm, and an average grain size of 2.
4 μm of tantalum carbide (TaC) powder and 1 wt% of cobalt (Co) powder were thoroughly mixed at a ratio of 8 wt% using a ball mill with an organic solvent as a solvent for 72 hours. After this mixture was prepared so that the liquid content was 9%, the circumcircle was φ25 mm at a molding pressure of 100 MPa by a hydrostatic pressure molding method in a mold without a binder in order to avoid the influence of the molding binder. A molded article of × 150 mm was molded.

After molding, 50 P
After removing the hexane remaining in the molded body in a,
For 30 x 60 seconds to prevent collapse during impregnation of the molded article. Further, in order to improve the homogeneity of the calcined body, a cutting process was performed so as to have a diameter of 15 mm after the burning. Next, the calcined body was immersed in a 10% concentration aqueous solution of Ni salt, and then subjected to a drying treatment in an exhaust-type hot-air drying oven at 130 ° C., thereby steepening the Ni concentration in the calcined body.

On the other hand, in the above basic properties, the amount of cobalt is increased or decreased by controlling the amount of tungsten carbide while keeping the Ni concentration the same, and the calcined body is immersed in an aqueous solution of Ni salt and embedded in powder. By drying, a homogenous body was obtained.

After these were sufficiently dried, they were sintered at a temperature of 50 Pa and a temperature of 1400 ° C. for 1 hour under a nitrogen flow. FIG. 8 shows the relationship between the distance from the surface of the sintered body and the hardness and toughness.

Here, the gradient functional area is about 7 mm,
The thickness of the high hardness homogeneous layer on the surface was about 0.3 mm, and the hardness was HRA93. The hardness of the equivalent product of the commercial material shown in FIG.
Has a very high hardness. Further, in the measurement under the same test conditions, the toughness of the inside of Example 1 was almost twice as large as that of 7 MPam ^1/2 of a commercially available product.

Further, the cross section of the sintered body obtained in Example 1 was observed using a microscope, and the size of the particles was measured. The result shown in FIG. 9 was obtained. Thus, it was found that the particles near the surface of the sintered body grew about 3 to 4 times as large as the inside.

FIG. 10 is a graph comparing the relationship between the amount of cobalt and the strength in the case of a homogeneous composition depending on the presence or absence of a grain growth agent. According to this, by performing the impregnation operation, the impregnated material promotes the growth of the ceramic particles, and is closely bonded to cobalt, which plays a role of a binder,
An improvement in strength was seen. That is, the ceramic particles and the metal were more closely bonded than before, and the effect of improving the strength was enhanced. As a result, the properties of the sintered body obtained in Example 1 are superior to those of carbide, and an effect that the performance as an end mill is dramatically improved can be obtained. Example 2 In Example 2, the end mills 10 and 10a shown in FIGS. 1 and 3 were manufactured using the sintered body formed according to Example 1. The end mill 10a constitutes a four-flute end mill for aluminum test, while the end mill 10a
Constitutes a two-flute end mill for SCM test.

More specifically, a molded body was formed using a composite material having the same composition as in Example 1, and the molded body was preliminarily calcined and preliminarily worked to prepare a 10% strength aqueous solution of Ni salt. After immersion and drying, a baking treatment was performed under the same conditions. After the baking treatment, the end mill 10a was manufactured by performing a cutting process or the like. As a comparative tool, a commercially available ultra-fine particle super hard material was manufactured under the same processing conditions and the same cutting condition, and an experiment was performed to compare the respective performances in an aluminum processing line. The work material was a high silicon content aluminum alloy ADC12 equivalent material.

FIG. 11 shows the test results. In the case of a commercially available cemented carbide material, although the wear resistance and strength are high, the formation of the constituent cutting edge is already seen at the time when the groove passes through the 5000 × 100 mm groove, and the 10,000 × 100 mm
In the groove, chipping of the cutting edge was also confirmed by chipping. Then, the precision of the groove processed at this point was considerably deteriorated, and thereafter, the chip edge was chipped by wear. On the other hand, in the end mill 10a, the metal component was gradually decreased from the inside of the end mill toward the end mill surface, the formation of the constituent edge was not observed, and the result that the precision of the machined hole was good was obtained. .

On the other hand, JISP-
The end mill 10 was manufactured by immersing the calcined body in a 10% concentration nickel salt aqueous solution in the same manner as described above and subjecting the calcined body to a calcining treatment. In the end mill 10, only the region of the blade portion 12 is hardened and formed into an inclined material. As a comparative tool, an end mill having excellent wear resistance and the like was produced by applying a multilayer coating of alumina, titanium nitride, titanium carbonitride or titanium carbide to a commercially available P-10 material. And SCM435 as a work material
When the end mill 10 and a commercially available product were subjected to machining experiments under the machining conditions of a rotation speed of 1800 rpm and a feed of 60 mm, the machining amount until the die life was about 300 km in the end mill 10, whereas the It was 68 km for the tool. With this end mill 10, the machining amount was about four times that of the comparative tool, and a very excellent result was obtained.

As described above, according to the second embodiment, when machining various kinds of materials such as aluminum-based materials and iron-based materials, the durability is remarkably improved as compared with the conventional tool, and the high hard coating film is formed. Compared with those having, it has an effect of being excellent in workability, improving the continuity of the production line, and suitable for high-speed processing and ultra-high-speed processing.

[0037]

In the composite end mill according to the present invention,
From the inside of the end mill to the end mill surface,
Because the ratio of the metal component in the composite material gradually decreases, the cutting edge part that actually performs processing has high hardness and wear resistance,
The inside of the end mill has high toughness and high strength,
During this time, the composition and physical properties gradually change. This allows
It is suitable for high-speed machining and greatly improves the durability.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional side view of a composite end mill according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional front view of the end mill.

FIG. 3 is a partial cross-sectional side view of a composite end mill according to a second embodiment of the present invention.

FIG. 4 is a partial cross-sectional side view of a composite end mill according to a third embodiment of the present invention.

FIG. 5 is a partial cross-sectional side view of a composite end mill (two blades) according to a fourth embodiment of the present invention.

FIG. 6 is a partial cross-sectional side view of a composite end mill (three blades) according to a fifth embodiment of the present invention.

FIG. 7 is a partial cross-sectional side view of a composite end mill (four blades) according to a sixth embodiment of the present invention.

FIG. 8 is a diagram illustrating the relationship between the distance from the end mill surface and the hardness and toughness.

FIG. 9 is an explanatory diagram of a growth state of tungsten carbide particles by adding nickel.

FIG. 10 is a diagram illustrating the relationship between the amount of cobalt and strength.

FIG. 11 is an explanatory diagram of a test result of an actual machining line.

[Explanation of symbols]

10, 10a to 10e: End mill 12, 12a to 12e: Blade part 14, 14a to 14
e: Shank part 16, 16a-16e: End face cutting edge 18, 18a-18
e: Cutting blade 20, 20a-20e: Metal part 22, 22a-22
e: ceramic part 24, 24a to 24e: inclined part

Claims (4)

[Claims] 1. An end mill comprising a composite material containing a ceramic component and a metal component.
An end mill made of a composite material, wherein a ratio of the metal component in the composite material is gradually reduced. 2. The end mill according to claim 1, wherein the thickness of the inclined portion where the ratio of the metal component gradually decreases is 0.3 mm.
A composite end mill characterized in that the end mill is set within a range of 10 to 10 mm. 3. The end mill according to claim 1, wherein the metal component in the composite material is VIII of the periodic table.
At least one metal component selected from the group consisting of Fe, Ni and Co, and the ceramic component in the composite material is WC, Ti
C, Mo ₂ C, TaC, NbC, Cr ₃ C ₂ or VC
And at least one ceramic component selected from the group consisting of: 85 wt% ≦ WC + TiC + Mo ₂ C + TaC + NbC
An end mill made of a composite material, wherein + Cr ₃ C ₂ + VC ≦ 97 wt%. 4. The end mill according to claim 1, wherein the hardness of the end mill surface is HRA.
A composite end mill having a diameter of 88 or more.