JPS6335705B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sintered hard alloy used in tools for machining difficult-to-cut materials. Work materials that have traditionally been considered difficult to cut include Ti alloys, Ni-based superalloys, and Co-based superalloys. Ti alloys have high high-temperature strength and low thermal conductivity, which causes the temperature of the cutting edge to rise during cutting, resulting in reduced tool life.Also, Ni-based superalloys and Co-based superalloys also have high strength and thermal conductivity at high temperatures. The temperature of the cutting edge increases due to its low ratio, and the wear of the cutting edge increases as it contains hard substances such as carbides and nitrides. For this reason, Ti alloys and Ni-based superalloys. Co-based superalloys require low speed, low feed, and small depth of cut machining, resulting in extremely low productivity. When machining such difficult-to-cut materials, in order to increase productivity without deteriorating machining accuracy or surface roughness of the workpiece, it is necessary to increase the cutting speed and avoid intermittent cutting such as milling and end mill cutting. It is necessary to develop tools that can also be used for cutting. For this purpose, conventionally WC-based cemented carbide, TiC-based cermet,
Al ₂ O _3- base ceramics etc. are used, but WC
Cemented carbides have the disadvantage of being easily welded and cannot be cut at high cutting speeds, while TiC-based cermets and Al ₂ O _3- based ceramics have poor chipping resistance and thermal shock resistance. As a result of the inventors' efforts to develop an alloy with a composition suitable for machining difficult-to-cut materials without the above-mentioned drawbacks,
The present invention was achieved by discovering that a sintered alloy mainly composed of ternary alloys of TiC, TiN-TaC, NbC-WC, and _Mo2C systems satisfies this purpose. First, the present inventors believe that bond metal is essential in the sintered alloy from the viewpoint of chipping resistance and thermal shock resistance of the tool cutting edge, and as a result of examining the necessary amount, the bond metal accounts for at least 1% or more by volume. It was concluded that it was necessary. If it is less than 1%, sufficient chipping resistance and thermal shock resistance cannot be obtained. Furthermore, it has been found that when the amount of bonded metal exceeds 5% by volume, the wear resistance during machining of difficult-to-cut materials is significantly degraded. From this, it was concluded that the amount of bonding metal should be 1% or more and 5% or less by volume. However, with the above composition alone, sufficient wear resistance could not be obtained when machining difficult-to-cut materials.Next, we investigated the particle size of the hard phase. As a result, it was confirmed that satisfactory wear resistance could only be achieved by setting the average particle size of the hard phase to 1 μm or less. As is well known, in a sintered hard alloy, the smaller the particle size of the hard phase, the harder it becomes. In other words, hardness suitable for machining difficult-to-cut materials can only be achieved when the average grain size of the hard phase is 1 μm or less. Furthermore, we made a prototype with a hard phase average particle size of 0.15 μm,
No particular inconvenience was observed. Based on the above findings, the present inventors investigated the composition of the hard phase, including TiC, TiN-TaC, NbC-WC,
The Mo ₂ C-based hard phase is particularly good, especially the one shown in Figure 1.
The present invention was achieved by discovering that a composition within XYZ shows excellent performance when machining difficult-to-cut materials. That is, the purpose of the present invention is to provide a sintered hard alloy suitable for machining difficult-to-cut materials, and the purpose is to provide a sintered hard alloy suitable for machining difficult-to-cut materials. In Figure 1, which shows the ternary phase diagram of Mo ₂ C), the hard phase, which has a composition within XYZ and has an average particle size of 1 μm or less, accounts for 95% by volume.
The above is 99% or less, and can be achieved by a sintered alloy for machining difficult-to-cut materials that contains iron group metals as a bonding metal in an amount of 1% to 5% by volume. The compositions of X, Y, and Z in FIG. 1 are as follows.

[Table] In the ternary phase diagram of the attached drawing, the composition in XYZ is TiC and/or TiN 50 to 85 mol%,
WC and/or _Mo2C15-50 mol%, and
It means TaC and/or NbC 0 to 35 mol%. The reason why the present invention is particularly limited in this way is as follows. TiC and/or TiN
If it is less than 50 mol%, wear resistance and welding resistance will decrease, and if it exceeds 85 mol%, chipping resistance,
The sharpness of the blade deteriorates. Also WC and/or
If Mo ₂ C is less than 15 mol %, chipping will occur easily, and if it exceeds 50 mol %, wear resistance will decrease. Additionally TaC and/or NbC is 35
When the amount exceeds mol%, wear resistance decreases. The above hard phase accounts for 95% or more and 99% or less by volume, and the Fe group metal which is the bonding metal accounts for 1% or more and 5% or less by volume, but the hard phase accounts for less than 95%,
When the binding metal content exceeds 5%, the wear resistance is significantly reduced, and when the hard phase exceeds 99%, and the binding metal content is less than 1%, the toughness deteriorates significantly. Furthermore, if the particle size of the hard phase exceeds 1 μm, chipping resistance and edge sharpness will be poor, and sufficient wear resistance will not be exhibited.
It must be 1 μm or less. To prepare the alloy of the invention, the corresponding components are mixed in accordance with conventional methods,
It may be pulverized, molded, and sintered, but it is preferable to maintain a nitrogen atmosphere at a nitrogen partial pressure of 1 to 500 Torr during sintering because denitrification will not occur and sintering will be performed stably. The present invention will be explained in more detail with reference to Examples below. Example 1 The composition shown in Table 1 was mixed with TiC-Ni
Acetone was added using a -Mo ball and an 18-8 stainless steel pot, and wet ball milling was carried out for 96 hours. Add camphor to this mixed powder,
Embossed with tons/ ^cm2 . This stamped body was fired at 1400° C. for 1 hour under a nitrogen partial pressure (PN ₂ ) of 5 Torr to produce an alloy. The mechanical properties of the alloys obtained are shown in Table 1. Below the table are Ti alloys, Ni-based alloys,
The results of a cutting test when cutting a Co-based alloy are shown. This shows that this alloy is superior to comparative alloys.

[Table] Cutting test 1 Work material: Ti alloy (Ti-6Al-4V) Cutting speed: 60 m/min Depth of cut: 0.5 mm Feed amount: 0.20 mm/reV Cutting time: 30 seconds Invention alloy in Table 1 A, B, C and comparative alloy H
When cut under the above conditions, A, B, and C were cut.
The amount of _VB wear was 0.15mm, the amount of H was 0.30mm, and the amount of welding was also extremely large. Cutting test 2 Work material: Co-based alloy (S 816) Cutting speed: 40 m/min Depth of cut: 0.5 mm Feed rate: 0.20 mm/reV Cutting time: 30 seconds Comparison with the invention alloys F and G in Table 1 When Alloy K was cut under the above conditions, the _VB wear amount for F and G was 0.10 mm, while for K it was 0.25 mm. Cutting test 3 Work material: Ni-based alloy (InConel-X) Cutting speed: 30 m/min Depth of cut: 0.5 mm Feed amount: 0.20 mm/reV Cutting time: 30 seconds Invention alloys D and E in Table 1 Comparative alloys I, J
When cut under the above conditions, the _VB wear amount for D and E was 0.17 mm, while for I it was 0.3 mm, and for J it became impossible to cut in 10 seconds. Example 2 The composition shown in Table 2 was mixed with TiC-Ni.
- Using a Mo ball, acetone was added through an 18-8 stainless steel pot, and wet ball milling was carried out for 96 hours. Camphor was added to this mixed powder and it was embossed at 2 tons/cm ² . This embossed body is heated to 1400℃.
Vacuum sintering (vacuum degree 10 ^-3 Torr) was performed for 1 hour to create an alloy. The mechanical properties of the alloys obtained are shown in Table 2. The cutting test was conducted in the same manner as in Example 1.

[Table] Cutting test 1 When the present invention alloys L and M and the comparative alloy R in Table 2 were cut, the V _B wear amount of L and M was 0.20 mm, while that of R was 0.30 mm. Ta. Cutting Test 2 When alloys N and O of the present invention and comparative alloy T in Table 2 were cut, the V _B wear amount of N and O was 0.15 mm, while that of T was 0.35 mm. Cutting Test 3 When alloys P and Q of the present invention and comparative alloy S in Table 3 were cut, the V _B wear amount of P and Q was 0.17 mm, while that of S was 0.30 mm.

[Brief explanation of the drawing]

Figure 1 shows the three-dimensional structure of TiC (and/or TiN) - TaC (and/or NbC) - WC (and/or Mo ₂ C).
It is an original state diagram.

Claims (1)

[Claims] 1 TiC (and/or TiN)-TaC (and/
or NbC) − WC (and/or Mo ₂ C)
In Figure 1, which shows the original phase diagram, 95% by volume is composed of a hard phase with an XYZ composition and an average particle size of 1 μm or less.
A sintered hard alloy for machining difficult-to-cut materials, characterized by containing 1% or more and 5% or less by volume of an iron group metal as a bonding metal. However, the composition of XYZ in Figure 1 above is as follows (mol%): [Table]