JPH08209285A - Hard metal for chipsaw - Google Patents

Abstract

PURPOSE: To provide a chipsaw having long service life in cutting pipes or the like at a high speed by improving heat crack resistance and high welding resistance in a hard metal for chipsaw. CONSTITUTION: The hard metal for chipsaw is constituted of a cermet consisting of 10-40% TiC, 0-40% TiN, 0-30% WC, 0-25% TaC or NbC, 0-15% Mo2 C, 10-25% Co+Ni and is 3.550-3.580Å in the lattice constant of bonding metallic phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard alloy for use in a tip saw having a large number of cutting blade tips mounted along the outside used for cutting a pipe, for example.

[0002]

2. Description of the Related Art Conventionally, a grindstone has been generally used to cut metal or the like. In this case, there are many safety problems such as damage and scattering of the whetstone, ignition by sparks,
In recent years, as a substitute for a grindstone, there is a tendency to mount a tip made of cemented carbide on the outer circumference of a metal disk. In addition, in cemented carbide, research on the influence of composition and grain size has been made, and it has been reported in Japanese Patent Laid-Open No.
There is also an example in which the cutting life is greatly improved as seen in -31530.

[0003]

However, in recent years, the cutting speed is generally required to be 1000 m / min or more, and there is a general tendency for high-speed and high-efficiency cutting. At present, it is not possible to meet the expectations of users. An object of the present invention is to provide a hard alloy for a tip saw having an excellent cutting life in high-speed cutting by improving wear resistance in high-speed cutting and welding resistance, which is a problem during high-speed cutting, as compared with conventional ones. Is.

[0004]

Means for Solving the Problems The above object is to use a cermet alloy and to determine the range of the hard phase forming component, the ratio of the hard phase forming component and the binder phase forming component, and the lattice constant of the binder phase. It is achieved by selecting and improving the heat crack resistance of the cermet alloy and suppressing the chemical reaction that occurs during cutting between the cermet alloy and the work piece.

[0005]

The inventors of the present invention have found that the cutting speed of the cermet alloy and cemented carbide tip saws having various compositions is 100%.
As a result of continuous cutting evaluation and observation at 0 m / min or more, fine heat cracks are generated on the tip like a turtle, and the portion surrounded by heat cracks is microscopically dropped due to welding of the work material. It was found that when the wear progressed to reach the end of life and chipping occurred in a relatively large range, chipping was induced by a sharp increase in cutting resistance and the end of life was reached. Furthermore, when observing the phenomenon in detail, the cutting speed is 15
At ultra-high speed cutting of 00 m / min or more, the detachment of each colony surrounded by the above heat cracks is dominant for the life.

That is, under such an ultra high speed,
Although the cutting resistance is relatively small, the heat generation is large and the amplitude of the heat cycle is large, so that heat cracks easily propagate, and the propagation of heat cracks governs the life. On the other hand, in the cutting speed range of about 800 to 1500 m / min, the propagation of heat cracks is relatively gradual, but the cutting resistance is relatively high and the surface pressure generated between the tip and the work material is high, so The cutting material has a strong tendency to be crimped. In this case, when the cross section of the pressure-bonded surface is analyzed, carbon is diffused from the work material to the chip, and this diffusion results in an increase in the adhesion between the pressure-bonded object and the chip. When the pressure-bonded product comes off during repeated cutting, the pressure-bonded product is strongly adhered to the diffusion layer, so that the pressure-bonded product is easily removed together with the underlying chip base material. Therefore, in order to suppress the propagation of heat cracks against such a phenomenon, not only to improve the toughness and heat crackability of the chip, but also suppress the above-mentioned diffusion and make it easier for the pressure-bonded object to fall off alone. The result is a long life.

JIS generally used for high-speed finishing
The cermet alloys represented by P10, P01, K10, and K01 attach great importance to heat resistance and wear resistance at high speeds, and often have a binding metal phase of 10% or less. However, such alloys have a low fracture toughness value, and once fine heat cracks occur, they immediately lead to overall defects. Therefore, the binder phase amount needs to be in the range of 10 to 25% in order to suppress the propagation of the generated heat cracks as much as possible. 1
If it is less than 0%, the above-mentioned defects are immediately caused, and if it exceeds 25%, the wear resistance is remarkably impaired. Main component TiC, T
Regarding iN, if the total amount exceeds 80%, the thermal conductivity deteriorates, and heat cracks easily occur. If it is too small, the cermet's advantages of abrasion resistance and welding resistance deteriorate. Therefore, the total amount of TiC and TiN is 40 to 7
The most preferable result is obtained at 0%. With respect to TiN, the fracture toughness value tends to improve as the added amount increases, and it is preferable to add TiN. However, if it exceeds 40%, defects tend to occur in the hard material.

Regarding WC, it is preferable to add WC because it has the effect of improving the toughness and thermal conductivity of the cermet, but the wear resistance deteriorates with the addition, and if it exceeds 25%, the wear resistance is remarkably deteriorated. To do. TaC and NbC are preferably added to improve wear resistance at high temperatures, but if they exceed 30%, the rubbing wear resistance deteriorates.
Mo ₂ C is preferably added because it has the effect of refining the structure and improving the toughness, but if it exceeds 15%, M ₂ C
Since o ₂ C itself is soft, both wear resistance at high temperatures and rubbing wear resistance tend to deteriorate.

The lattice constant of the bonded metal phase of the cermet alloy having the above-mentioned composition changes depending on the total carbon content of the alloy. The lattice constant becomes larger as the carbon content becomes lower because other components dissolved in the binder phase increase, and becomes smaller as the carbon content becomes higher and generally ranges from about 3.550 angstroms to 3.620 angstroms. In the present invention, the preferable result is in the range of 3.550 angstroms to 3.580 angstroms, that is, the higher carbon amount side. This is because when the chip material is a low-carbon alloy, the difference in the amount of carbon from the work material is large, which naturally results in the diffusion of carbon.

Therefore, the higher the half of the range of carbon allowed as an alloy, the less the diffusion of carbon and the longer the life. In the present invention, the lattice constants are Co and Ni
Calculated from the (111) plane bending angle of (3), but when it is less than 3.550 angstrom, brittle free carbon is often formed in the alloy, which is not preferable. Hardness mainly depends on composition, but 8 on Rockwell A scale
If it is less than 5, not only the wear resistance is poor, but also plastic deformation tends to occur, and if it exceeds 91.5, the toughness deteriorates and the heat cracks easily propagate as described above. Further, in order to improve the plastic deformation resistance in such a case, Zr, H
One or two of f, V metal, carbide, nitride, carbonitride
Addition of at least one species is effective, but if over 5%, toughness tends to deteriorate.

[0011]

EXAMPLES The present invention will be described in detail below with reference to examples. A commercially available average particle size of 1.2 so that the composition shown in Table 1 is obtained.
μ TiC, TiN, TiCN powder, 1.5μ WC
Powder, 1.4 μm of TaC, NbC powder, 1.8 μm of Mo 2 C powder, Co, and Ni powder were mixed in an attritor for 7 hours, dried, and then a saw tip was pressed.
Sintering was performed at 460 ° C. for 1 hour in an atmosphere of nitrogen 0.3 Torr.

[0012]

[Table 1]

The tip saw shape is a common shape used for metal cutting. Using these tip saws, an S50C pipe having a diameter of 50 mm and a wall thickness of 4 mm was cut at a cutting speed of 1000 m / min to compare the number of cuttable pieces. Table 2 shows the results.

[0014]

[Table 2]

It is apparent from Table 2 that the alloys of the present invention are excellent in heat crack resistance and welding resistance, so that the life span is greatly improved and the alloys on the high carbon side show longer life. Is clear.

[0016]

EFFECTS OF THE INVENTION The hard alloy tip saw of the present invention is superior in wear resistance, fracture resistance, heat crack resistance and welding resistance at medium to high speeds as compared with the conventional cemented carbide tip saw, and is significantly excellent in cutting pipes and the like. It has a long life.

Claims (3)

[Claims] 1. A TiCN-based cermet, wherein a hard phase forming component is in a weight ratio of TiC: 10 to 40% and TiN: 0.
-40%, WC: 0-30%, TaC or NbC: 0
˜25%, Mo ₂ C: 0 to 15%, Co + Ni: 10 to 25% as a binder phase forming component, and unavoidable impurities, and the lattice constant of the binder metal phase is 3.55 Å to 3.58 Å. A hard alloy for tip saws. 2. Part of Ti is replaced with one or more of Zr, Hf, V and Cr metals, carbides, nitrides and carbonitrides within a range of 5% by weight or less. The hard alloy for a tip saw according to claim 1. 3. The hard alloy for a tip saw according to claim 1, which has a hardness of 85.0 to 91.5 on the Rockwell A scale.