JPH07241704A - Cutting tool made of cermet - Google Patents

Abstract

PURPOSE:To provide a cutting tool made of cermet showing excellent defect resistance when it is used for continuous cutting of steel or the like under some severe condition. CONSTITUTION:This is a cutting tool made of cermet having composition constituted of a bonding phase forming component consisting of at least one sort out of Co, Ni, and Fe by 1-30wt.%, and remains such as a hard dispersed phase forming component consisting of at least one sort of carbide, nitride, carbonitride of 4a, 5a, 6a group metal of the periodic table and solid solution consisting of two or more sorts of these compounds, and inevitable impurities. On the surface of the cutting tool made of cermet, there are holes elliptically opening of average 50-1000spot/cm<2>, and each hole has a major axis of 20-200mum, and the ratio major axis to minor axis a/b is less than 3.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cermet cutting tool which exhibits excellent fracture resistance when used for intermittent cutting of steel or the like under particularly severe conditions.

[0002]

2. Description of the Related Art In recent years, along with the trend of cutting efficiency and manpower saving, cutting time is shortened by increasing cutting speed, or a process from multi-step cutting such as rough cutting and finish cutting to one-step cutting is performed. The cutting process is being rationalized in all aspects such as shortening and constant tool replacement, such as automatic tool replacement.

On the other hand, the tool material is also provided with a tool material capable of withstanding the high temperature generated by the increase in the cutting speed and a cutting edge strength capable of withstanding a relatively heavy load such as one-step cutting. There has been a demand for a tool material for both roughing and finishing, and a tool material having a stable cutting edge that can withstand constant tool exchange.

Cermet cutting tools exhibit superior performance to high-efficiency machining by increasing the cutting speed, as compared with conventional cemented carbide cutting tools, and they are superior to cemented carbide cutting tools in their performance. Although it is possible to finish the work material with high accuracy, there is still a problem that the chip is more likely to be damaged than the cutting tool made of cemented carbide.

However, in recent years, cermet cutting tools are more likely to be chipped due to the presence of internal strain, and in order to eliminate such internal strain, cracks are positively cracked on the surface of the cermet cutting tool. It has also been performed to generate and eliminate the internal strain (Japanese Patent Application Laid-Open No. HEI 3-
228503).

[0006]

However, in the cutting tool made of cermet having cracks, the crack length is 100 times longer than the width and is connected to a wide range. However, when it is used for profiling cutting in which the cutting depth becomes large for a moment, it cannot be ignored as a cause of the crack introduced, and there is a problem that the cutting life is shortened.

[0007]

Therefore, the present inventors have
As a result of conducting research to obtain a cermet cutting tool that is excellent in fracture resistance and will not be broken for a longer period of time than before, (1) In a normal cermet cutting tool, In the conventional crack, the major axis of the surface opening diameter is 2 to 200 μm, and the ratio of major axis a to minor axis b: a / b is 3.0 or less (preferably 0.5).
The cermet-made cutting tool having holes (hereinafter, referred to as oval-shaped open holes) having an oval shape of 1.0 to 1.0) is more excellent in fracture resistance than conventional ones. (2) The above The oval-shaped open holes have an average of 50 rims on the rake face of the tool from the cutting edge toward the center within at least 3 mm.
It was found that the presence of ˜1000 pieces / cm ² is more excellent in fracture resistance.

The present invention has been made on the basis of such findings, and a binder phase forming component comprising 1 or 2 or more of Co, Ni and Fe: 1 to 30% by weight.
And the rest is a hard dispersion phase composed of one or two or more of solid solutions composed of carbides, nitrides, carbonitrides of group 4a, 5a and 6a metals of the periodic table and two or more of these compounds. A cermet cutting tool having a composition comprising a forming component and unavoidable impurities, (1) The major axis of the opening diameter is 2 to 2 on the surface of the cermet cutting tool.
200 μm (preferably 5 to 50 μm), and a ratio of major axis a to minor axis b: a / b is 3.0 or less (preferably 0.5 to 1.0) A cermet cutting tool having open holes (hereinafter referred to as oval-shaped holes), and (2) the oval-shaped holes are
On the rake face of the cutting tool, 50 to 1000 on average in the peripheral portion within at least 3 mm from the cutting edge toward the center.
The present invention is characterized by a cermet cutting tool existing in the number of pieces / cm ² .

In the cermet cutting tool of the present invention, the major diameter of the elliptical open hole is limited to the major diameter of 2 to 200 μm. When the major diameter of the opening is longer than 200 μm, it is almost the same as a crack. This is not preferable because it acts and the stress applied to the tip of the oval-shaped open hole becomes large, resulting in a decrease in toughness. This is because it is weak and unfavorable.

It is preferable that 50 to 1000 holes / cm ² are present on the rake face of the cutting tool on the rake face of the cutting tool in the peripheral portion within at least 3 mm from the cutting edge to the center. If the distribution density is less than 50 pieces / cm ² , the internal strain cannot be sufficiently eliminated, while 10
This is because when it is present in excess of 00 / cm ² , it becomes porous and its strength is lowered.

In order to manufacture a cermet cutting tool having an oval-shaped open hole on the surface of the present invention, raw material powders are blended and the mixed powder is granulated to produce a granular powder (hereinafter, granulated powder). This granulated powder is press-molded into a molded body, and the molded body is placed in a nitrogen gas atmosphere from a predetermined temperature lower than the temperature at which the liquid phase appears. Sintering is performed by switching to a vacuum or denitrifying atmosphere in a temperature range above the densification temperature. At this time, the elliptical open pores and the density can be controlled by appropriately combining the size and hardness of the granulated powder, the temperature for switching the atmosphere during sintering, and the atmosphere before and after the switching.

[0012]

EXAMPLES Next, the present invention will be specifically described based on Examples. Examples As raw material powders, all have an average particle diameter of 1.0 to 2.0 μm.
TiCN powder, TiC powder, TiN powder within the range of m,
TaC powder, NbC powder, WC powder, Mo ₂ C powder, Z
rC powder, Co powder, and Ni powder were prepared, and these raw material powders were blended so as to have the blending composition shown in Table 1, wet-mixed with a ball mill to prepare a mixed powder, and dried and granulated. Further, paraffin was coated to prepare granulated powder having an average particle diameter of 200 μm, and the granulated powder was press-molded at a pressure of 1 ton / cm ² to prepare molded products A to C.

[0013]

[Table 1]

The compacts A to C shown in Table 1 are charged into a sintering furnace and sintered according to the sintering pattern (I) at the temperature and atmosphere shown in FIG. 1 to obtain ISO standard CNMG12040.
Eight shapes of the present invention cermet cutting tool (hereinafter referred to as the present invention cutting tool) 1 to 3 were manufactured. Sintering pattern (I)
As shown in FIG. 1, the temperature in the sintering furnace is 5 ° C./m.
The temperature is raised to the sintering temperature of 1480 ° C. at a heating rate of 1
After the sintering temperature of 480 ° C. is maintained for 1 hour, the temperature pattern of cooling and the temperature rising range of the atmosphere in the sintering furnace up to 1200 ° C. are maintained at a vacuum of 0.05 torr and 1200
At 10 ° C., the atmosphere was switched to a nitrogen gas atmosphere of 10 torr, and the temperature was raised to a sintering temperature of 1480 ° C.
After the holding time at 80 ° C. is maintained in this nitrogen gas atmosphere, the atmosphere is further switched to a vacuum atmosphere of 0.1 torr and the subsequent cooling is maintained in this vacuum atmosphere.

Further, the compacts A to C shown in Table 1 are charged into a sintering furnace and sintered according to the sintering pattern (II) at the temperature and atmosphere shown in FIG. 2 to obtain ISO standard CNMG1204.
Cermet cutting tools of the present invention having a shape of 08 (hereinafter referred to as cutting tools of the present invention) 4 to 6 were manufactured. Sintering pattern (I
I), as shown in Figure 2, the temperature in the sintering furnace is 5 ℃
1200 ° C. at a heating rate of / min
C. to 1500.degree. C. sintering temperature at a temperature increase rate of 2.degree. C./min and holding at a sintering temperature of 1500.degree. C. for 1 hour, and then cooling the temperature pattern and the atmosphere in the sintering furnace to 12
The temperature rising range up to 00 ° C. is maintained at a vacuum of 0.05 torr, and at 1200 ° C., the atmosphere is switched to a nitrogen gas atmosphere of 30 torr, and the temperature rising range up to the sintering temperature of 1500 ° C. and then 1500 ° C. After holding for 30 minutes in this nitrogen gas atmosphere, the atmosphere is further switched to a nitrogen gas atmosphere of 5 torr, and the subsequent sintering holding and cooling are held in this nitrogen gas atmosphere.

Further, the compacts A to C were sintered according to the sintering pattern (III) at the temperature and atmosphere shown in FIG. 3 to manufacture the cutting tools 7 to 9 of the present invention having the ISO standard CNMG120412 shape. In the sintering pattern (III), the temperature in the sintering furnace is 5
The temperature is raised to 1200 ° C. at a heating rate of ° C./min, and
The temperature pattern from 0 ° C. to 1540 ° C. and the temperature in the sintering furnace were raised after the temperature was raised at a heating rate of 2 ° C./min. 1
The temperature rise up to 200 ° C. is maintained in a vacuum of 0.05 torr, the atmosphere is switched to a nitrogen gas atmosphere of 40 torr at 1200 ° C., the temperature rise up to the sintering temperature of 1540 ° C. is kept in this nitrogen gas atmosphere, and then 0.1 torr The atmosphere pattern is such that the vacuum atmosphere is switched to, and the holding and cooling at 1540 ° C. for 1 hour are maintained in this vacuum atmosphere. Hereinafter, similarly, the molded bodies A to C are sintered in the sintering pattern (IV) at the temperature and the atmosphere shown in FIG.
The cutting tools 10 to 12 of the present invention having the shape of ISO standard CNMG120412 were manufactured.

Comparative Example For comparison, the compacts A to C shown in Table 1 were placed in a sintering furnace and sintered in a sintering pattern (V) shown in FIG.
Comparative cermet cutting tools (hereinafter referred to as comparative cutting tools) 1 to 3 having an ISO standard CNMG120412 shape were manufactured. As shown in FIG. 5, the sintering pattern (V) was performed by increasing the temperature in the sintering furnace to 1100 ° C. at a temperature increasing rate of 5 ° C./min, and increasing the sintering temperature from 1100 ° C. to 1500 ° C. to 2 ° C. The temperature pattern is such that the temperature is raised at a heating rate of 1 / min, the temperature is maintained at the sintering temperature of 1500 ° C. for 1 hour and then cooled, and the temperature inside the sintering furnace is raised to 1100 ° C. by 0.05 torr.
In a nitrogen gas atmosphere of 1 to 100 ° C., and the atmosphere is switched to a nitrogen gas atmosphere of 20 torr at 1100 ° C., and then the temperature is raised and held at the sintering temperature and cooled in this nitrogen gas atmosphere.

Conventional Example As a raw material powder, each has an average particle diameter of 1.0 to 2.0 μm.
TiCN powder, TiC powder, TiN powder within the range of m,
TaC powder, WC powder, Mo ₂ C powder, VC powder, Co
Powder and Ni powder are prepared, and these raw material powders are weight%
TiC: 29%, TiN: 19%, WC: 16%, T
aC: 6%, VC: 4%, Mo ₂ C: 9%, Ni: 6
%, Co: 11%, and wet mixed with a ball mill to prepare a mixed powder, which is dried and then 1 ton
A molded body D was prepared by a usual method of press molding at a pressure of / cm ² , and this molded body D was put into a sintering furnace and sintered according to a sintering pattern (VI) shown in FIG. Standard CNM
A conventional cermet-made cutting tool having a G120408 shape (hereinafter referred to as a conventional cutting tool) was manufactured.

As shown in FIG. 6, the sintering pattern (VI) shows that the temperature in the sintering furnace is 120 at a temperature rising rate of 5 ° C./min.
Increase the temperature to 0 ° C, and increase from 1200 ° C to 1450 ° C by 2 ° C
The temperature pattern is one in which the temperature is raised at a heating rate of 1 / min, the temperature is maintained at the sintering temperature of 1450 ° C. for 1 hour and then cooled, and the atmosphere pattern is maintained in a vacuum of 0.05 torr from the beginning to the end of sintering. Is.

When the surfaces of the cutting tools 1 to 12 of the present invention, the comparative cutting tools 1 to 3 and the conventional cutting tool produced under such sintering conditions were observed, the cutting tools 1 to 12 of the present invention had an oval-shaped opening. Although holes were found, they were not found on the surfaces of the comparative cutting tools 1 to 3, and cracks were found on the surface of the conventional cutting tools. The major diameter size, the ratio of major diameter a to minor diameter b: a / b and the distribution density of the oval-shaped open holes on the surface of the cutting tools 1 to 12 of the present invention and the cracks on the surface of the conventional cutting tool were measured, and the results were obtained. Is shown in Table 2. The distribution density was measured by taking an enlarged photograph of the tool rake face from above and measuring the number per unit area on the photograph.

Furthermore, these cutting tools 1 to 12 of the present invention,
Using comparative cutting tools 1 to 3 and a conventional cutting tool, a work material: SCM440, a four-grooved material, a cutting speed: 200 m / min. , Feed: 0.2 mm / rev. Cutting depth: 2 mm, intermittent cutting of steel was performed, and the number of impacts until the cutting edge was broken was measured. The results are shown in Table 2.

[0022]

[Table 2]

[0023]

From the results shown in Table 2, the major diameter size of the oblong-shaped open pores is 2 to 200 μm, and the ratio of major diameter a to minor diameter b: a / b is 3.0 or less. The cutting tools 1 to 12 of the present invention having a distribution density in which certain oblong-shaped open holes are present on average of 50 to 1000 holes / cm ² are comparative cutting tools 1 to 3 having no oblong-shaped open holes and cracks. As compared with the conventional cutting tool, the number of impacts until the cutting edge is broken is large, which shows that it exhibits excellent performance for severe intermittent cutting. As described above, since the cermet cutting tool of the present invention is excellent in toughness, it exhibits a long life even when used for milling cutting under severe conditions and brings an excellent industrial effect.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a sintering pattern (I).

FIG. 2 is an explanatory diagram of a sintering pattern (II).

FIG. 3 is an explanatory diagram of a sintering pattern (III).

FIG. 4 is an explanatory diagram of a sintering pattern (IV).

FIG. 5 is an explanatory diagram of a sintering pattern (V).

FIG. 6 is an explanatory diagram of a sintering pattern (VI).

Claims (3)

[Claims] 1. A binder phase mainly composed of one or more of Co, Ni and Fe: 1 to 30% by weight, and the rest being carbides and nitrides of 4a, 5a and 6a metals of the periodic table. A cutting tool made of cermet having a composition comprising a hard dispersed phase mainly composed of one or more of a carbonitride and a solid solution composed of two or more of these compounds, and an unavoidable impurity. The major axis of the opening diameter is 2 on the surface of the cutting tool.
˜200 μm, and ratio of major axis a to minor axis b: a / b
A cermet-made cutting tool having holes having an oval shape having a value of 3.0 or less (hereinafter referred to as oval-shaped open holes). 2. The hard dispersed phase comprises Ti, W and / or
Alternatively, it is a hard dispersed phase mainly composed of one or more of Mo and Ta and / or Nb carbides, nitrides, carbonitrides and solid solutions composed of two or more of these compounds. The cermet-made cutting tool according to claim 1. 3. The elliptical open hole is at least 3 mm from the cutting edge to the center of the rake face of the cutting tool.
The cutting tool made of cermet according to claim 1 or 2, characterized in that an average of 50 to 1000 pieces / cm ² are present in the peripheral portion within.