JP3368367B2 - Tungsten carbide based cemented carbide and cutting tools - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-hardness and high-strength tungsten carbide-based cemented carbide and a cutting tool using the same as a base material. Cutting tools and drills made of this alloy have excellent wear resistance and fracture resistance, and can be suitably used for continuous cutting and intermittent cutting. In particular, a cutting tool in which a predetermined surface coating is further formed on the substrate can be suitably used in fields requiring excellent cutting performance such as high-speed cutting, high feed, high cutting, and the like. [0002] Conventionally, cemented carbides have been used as cutting tools as well as cermets, and are composed of a hard phase mainly composed of tungsten carbide and a binder phase composed of cobalt, nickel or the like. Consists of [0003] Recently, however, the use conditions of cutting tools have become severer and tools for precision machining have been desired, and a cemented carbide made of fine crystal grains has been developed as such a tool material. . For example, WC-Co
Addition of carbides such as VC and Cr ₃ C ₂ in order to suppress the grain growth of WC crystal particles to the base alloy
No. -56224. It is also known from the viewpoint of the properties of cemented carbide that it is important to suppress the formation of intermetallic compounds (η phase) and the formation of free carbon due to the low carbon content in the alloy. . [0004] Further, surface-coated cemented carbides, which are made of cemented carbide as a substrate and whose surface is coated with ceramics,
It has both the toughness of a cemented carbide as a base material and the wear resistance of a ceramic coating, and has attracted attention (for example, JP-A-55-83507 and JP-A-4-275804). [0005] However, in recent years, there has been a demand for higher efficiency and labor saving of cutting work, and there has been a tendency to cope with heavy cutting under more severe conditions. It is becoming difficult to maintain sufficient performance with the above technique, and there is a demand for the development of a tungsten carbide-based cemented carbide having both excellent wear resistance and fracture resistance. [0006] The inventors of the present invention have conducted various experiments and found that the hardness and strength of the tungsten carbide-based cemented carbide are reduced by making the width of the particle size distribution extremely small. It has been found that they have increased significantly and that their properties can be obtained stably. [0007] The present invention has been made based on such findings, and a first object of the present invention is to provide a cemented carbide having high hardness and high strength. A second object is to provide a cutting tool having excellent wear resistance and fracture resistance using such a cemented carbide. Means for solving the problems include a hard phase mainly composed of tungsten carbide, a binder phase composed of one or more kinds of iron group metals, and a tungsten carbide base composed of unavoidable impurities. in hard alloy, said hard phase, particles having a particle size 0.5~1.5μm will have a particle size distribution which accounts 90 vol% or more of the total hard phase, hardness and strength of the alloy is less
A tungsten carbide-based cemented carbide characterized by satisfying the following two formulas: [0009] Similarly, the second means is that a hard phase mainly composed of tungsten carbide, a binder phase composed of one or more of iron group metals, and a substrate composed of unavoidable impurities are provided on the surface of the base of 4a of the periodic table. , 5a, 6a metals, and carbides, nitrides, oxides, borides of one or more metal elements selected from the group of Al and one or more layers of one or more of these compounds In a cutting tool provided with a coating composed of: the hard phase has a particle size of 0.5 to 1.5 μm
Seki particles have a particle size distribution which accounts 90 vol% or more of the total hard phase, hardness and strength of the substrate satisfy the following two equations
Surface-coated cemented carbide cutting tool, characterized in that in the engagement
It is in. Hv ≧ 2600−4.0σf H
v: Vickers - scan hardness σf ≧ 200kg / mm ² σf: bending strength [action] hard phase mainly contributes to improvement of hardness, thereby improving the wear resistance. Examples of the component forming the hard phase include TiC, TaC, NbC and solid solutions thereof in addition to WC. The binder phase functions as a sintering aid to bind hard sintering hard materials, increases strength and toughness,
Improves fracture resistance. And the film further improves the wear resistance. Here, the particles of the hard phase constituting the tungsten carbide-based cemented carbide (hereinafter also referred to as "hard particles") preferably have a particle size of 0.5 to 1.5 μm, and more preferably 0 to 1.5 μm. 0.8 to 1.2 [mu] m. Therefore, in the particle size distribution of these hard particles, 0.5 to 1.
It is desirable that 90% or more of the particles exist between the particle sizes of 5 μm. This is because, when the particle diameter is 0.5 μm or less, although the hardness increases, the mean free path between the particles becomes too small, and the strength is rather reduced. This is because both decrease. In the particle size distribution, the particle size is 0.5 to 1.5μ.
If the content of the particles m is 90% or less, stable performance cannot be obtained in abrasion resistance and chipping resistance. Further, the tungsten carbide-based cemented carbide according to the present invention has a very precisely controlled structure, and therefore has excellent properties with extremely high hardness and strength. Therefore, it varies with the amount of the binder phase while maintaining the relationship between the hardness and the strength as shown in FIG. 1 and can cope with a wide range of cutting conditions. Examples Example 1 Tungsten carbide powder (WC powder) having an average particle size of 0.8 μm was mixed with cobalt powder (Co powder) having an average particle size of 2 μm.
After mixing and molding at the ratios shown in Table 1, sintering was performed at 1400 to 1600 ° C. in a reduced pressure atmosphere. The obtained sintered body was one in which a hard phase composed of tungsten carbide was firmly bound by a binder phase composed of Co. On the other hand, as a comparative product, in the composition shown in Table 1, 5,6
7 indicates that the raw material was strongly pulverized and refined, and then molded.
No. Samples 8 and 9 were manufactured under the same conditions as those of the product of the present invention except for the firing conditions. Next, each sample No. The average particle size of 1 to 9, the content of particles having a particle size of 0.5 to 1.5 μm with respect to the entire hard phase, Vickers hardness and bending strength were measured. Table 1 shows the measurement results together with the production conditions. Fig. 1 shows the results of plotting the relationship between Vickers hardness and bending strength (No. 8 in which both hardness and strength were low was not shown). [Table 1] In Table 1, the values of the average particle diameter and the particle content were determined by observing the structure of each sample with an electron microscope at 5000 times and using an image analyzer. The bending strength σ is JIS B-4053
Is a value obtained by a three-point bending test according to As shown in Table 1, the cemented carbide of the present invention showed higher values in both hardness and strength than the alloy of the comparative example. Among the sintered bodies thus obtained, No. 1-7
Was ground into a tool shape of CNMG432 to produce cutting tool chips, and a turning test was performed on each of the chips under the following conditions to evaluate cutting performance. Cutting conditions: Cutting speed V = 150 (m / min) Feed f = 0.25 (mm / rev) Depth of cut = 0.5 (mm) Wet cutting work material: Titanium Ti Holder: C31R-44 Turning after testing, the results obtained by RBI the relationship between V _B wear amount and the cutting time in FIG. [0018] As seen in FIG. 2, the cutting tool according to the invention the cemented carbide is compared to a cutting tool by an alloy of the comparative example, less V _B wear amount, moreover the difference is significant as the cutting time becomes longer Met. Therefore, when considering the results of Table 1 and FIG. 2 together, it was found that the particle size distribution of the hard phase significantly affected the mechanical properties and the cutting performance regardless of the chemical composition of the cemented carbide. Example 2 A sintered body (except No. 5) obtained under the same conditions as in Example 1 was polished into a tool shape of CNGA432, and this was used as a substrate to form a chemical vapor deposition method on the surface thereof ( CVD method) to form a titanium carbide (TiC) coating having a thickness of 5
μm, and then aluminum oxide (A
l ₂ 0 ₃₎ a coating provided coating thickness thereof is subjected to a 1 [mu] m, to produce a cutting tool tip. For each of the chips obtained as described above, a turning test of a hard steel material was performed under the following conditions to evaluate the cutting performance. Cutting conditions: Cutting speed V = 150 (m / min) Feed f = 0.23 (mm / rev) Cutting depth d = 2.0 (mm) Wet cutting work material: SNGM8H (φ200 × 600 L [mm]) , H
_B 300) Holder: After C31R-44 Turning test shows a result of RBI the relationship between V _B wear amount and the cutting time in FIG. [0021] As seen in FIG. 3, the present invention cutting tool, in comparison with cutting tools of the Comparative Example, V _B wear amount is small,
Moreover, the difference was remarkable as the cutting time became longer. Therefore, considering the results of Table 1 and FIG. 3 together,
Regardless of the chemical composition of the substrate, it has been found that the particle size distribution of the hard phase has a significant effect on mechanical properties and cutting performance. Example 3 Under the same conditions as in Example 1, respective sintered bodies of the present invention and comparative products (except for No. 5) were obtained. These sintered bodies were SEK4
After processing into a 2A tool shape, a titanium nitride (TiN) coating was applied to a thickness of 2 μm by physical vapor deposition (PVD) using the substrate as a substrate to form a coating, and a cutting tool chip was manufactured. Each chip obtained as described above was subjected to milling of a hard steel material under the following conditions. [0023] Cutting conditions: cutting speed V = 244 (m / min) Feed f = 0.23 (mm / rev) cut d = 2.0 (mm) dry cutting work material: SCM440H (H _B 240) Cutter: after SE445R (φ160mm) milling test shows a result of RBI the relationship between V _B wear amount and the cutting time in FIG. [0024] As seen in FIG. 4, the present invention cutting tool, in comparison with cutting tools of the Comparative Example, V _B wear amount is small,
Moreover, the difference was remarkable as the cutting time became longer. Therefore, when the results of Table 1, FIG. 1, FIG. 2 and FIG. 3 are considered together, the particle size distribution of the hard phase significantly affects the mechanical properties and the cutting performance regardless of the presence or absence of the coating and the method. It was found to have The tungsten carbide based cemented carbide according to the present invention exhibits excellent wear resistance when used as a cutting tool in heavy cutting such as high feed and high depth of cut, and has a severe milling condition. It has excellent industrial effects, such as excellent fracture resistance when used for cutting. In addition, since it has high hardness and strength, it can be applied to drills.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph for deriving a relational expression between hardness and strength. [2] The relationship between V _B wear amount and the cutting time by turning the test of Example 1 is a graph showing the results of RBI. 3 is a graph showing the results of RBI the relationship between V _B wear amount and the cutting time by turning the test of Example 2. [4] The relationship between V _B wear amount and the cutting time by milling test of Example 3 is a graph showing the results of RBI.

Claims (1)

(57) [Claims 1] A periodic phase is formed on the surface of a substrate composed of a hard phase mainly composed of tungsten carbide, a binder phase composed of one or more of iron group metals, and unavoidable impurities. Rule 4
Carbide, nitride, oxide, boride of one or more metal elements selected from the group of a, 5a, 6a metals and Al, and a single layer or a plurality of two or more of these compounds In a cutting tool provided with a coating composed of layers, the hard phase has a particle size distribution in which particles having a particle size of 0.5 to 1.5 μm account for 90% by volume or more of the entire hard phase, and the hard phase of the substrate is hardened. And a strength that satisfies the following two formulas: a surface-coated cemented carbide cutting tool. Hv ≧ 2600−4.0σf Hv: Vickers hardness σf ≧ 200 kg / mm ² σf: Flexural strength