JPH03202402A - Combined hard alloy material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a composite hard alloy material used as a material for cutting tools and the like.

[Prior Art] High-speed tool steel or cemented carbide is most commonly used as a material for cutting tools and the like.

High-speed tool steels are mainly made of CrSMo, W, and V.

It is an alloy steel containing CO and C as alloy components and having Fe as a matrix. In high-speed tool steel, by adjusting each alloy component, properties suitable for the tool material can be adjusted, and at the same time, the properties can be changed by heat treatment.

Generally, high-speed tool steel has excellent toughness and is therefore used as a material for cutting tools that require high reliability. Manufacturing methods for high-speed tool steel include melt casting,
The atomized powder is subjected to hot isostatic pressing (HIP, Hot
Powder metallurgy methods are widely used in which solidification is performed by, for example, 1sostatic pressing.

Furthermore, in order to add wear resistance to high-speed tool steel which has excellent toughness as described above, a method has been proposed in which the amount of carbides and nitrides is increased. For example, JP-A-55-583
No. 50 and Japanese Unexamined Patent Publication No. 58-181848 disclose a method of mixing and sintering high-speed tool steel powder with powders such as carbides and nitrides to increase the amount of carbides and nitrides in the matrix. has been proposed as a method to do so. Furthermore, Japanese Patent Publication No. 60-18742 proposes a material in which extremely fine TiN particles are dispersed in a matrix of high-speed tool steel. JP-A-60-2648 and JP-A-61-179845 disclose a high-speed tool steel in which extremely fine TiN particles are dispersed in a matrix;
Tool materials composited with alloy steels such as high-speed tool steels have been proposed.

On the other hand, cemented carbide is an alloy obtained by sintering carbides such as WC, TiC, TaC5Nbc, etc. using Co'PNi as a base. Although this cemented carbide is inferior to high-speed tool steel in terms of toughness, it has excellent high abrasion resistance, making it a tool material that exhibits its characteristics in high-speed cutting. The properties of cemented carbide suitable for use as a tool material can be adjusted by changing its composition, but the properties can also be adjusted by appropriately changing the grain size of its hard phase. Note that cemented carbide can be manufactured by a powder metallurgy method consisting of a series of steps of mixing, pressing, and sintering powder as a raw material.

[Problems to be Solved by the Invention] As described above, although high-speed tool steel has excellent toughness, it has insufficient wear resistance, so it is difficult to use it as a tool material suitable for high-speed cutting.

In order to improve the wear resistance of high speed tool steels, increasing the alloying content and increasing the amount of carbides in the matrix are commonly used.

However, it is not easy to achieve improved wear resistance while maintaining the excellent toughness that characterizes high-speed tool steel.

In other words, by increasing the alloy components, the amount of carbides in high-speed tool steel increases, and the wear resistance increases, but on the other hand,
A rapid decrease in toughness occurs. In particular, when manufactured by the melt casting method, the volume of carbides in high-speed tool steel is at most about 15% by volume, and if more than this amount of carbides is included in the matrix, it cannot be used as a practical tool. Unable to obtain toughness. Further, although the amount of carbides can be increased to some extent by powder metallurgy, the amount of carbides that can be increased is about 30% by volume at most.

By mixing powders such as carbides and nitrides with high-speed tool steel powder,
According to the sintering method, it is theoretically possible to contain any amount of carbide or nitride. However, even in this case, it is inevitable that as the hard phase increases, the toughness will decrease. Generally, when powders with a particle size of several microns are mixed, compression molded, and sintered, as the amount of hard ceramics such as carbides and nitrides increases, they form at the grain boundaries of the powder of high-speed tool steel. Carbides and nitrides aggregate in a network. When carbides and nitrides aggregate in this way, the toughness decreases to an unacceptable degree. As a countermeasure to this problem, it is possible to make carbides and nitrides into ultrafine particles on the order of submicrons. However, such ultrafine particles tend to aggregate, and it is not easy to uniformly disperse them. Therefore, it is currently impossible to obtain a structure of high-speed tool steel in which carbides and nitrides are dispersed so as to have desired properties.

Furthermore, since the elastic modulus of high-speed tool steel is smaller than that of cemented carbide, which will be discussed later, deformation during cutting increases.
There was a problem in that it could not be used for applications such as tools that required high accuracy.

On the other hand, unlike high-speed tool steel, cemented carbide has excellent wear resistance but does not have sufficient toughness.

Therefore, cemented carbide is not used as a material for tools that require reliability. As a method of improving the toughness of cemented carbide, a method of making carbides in the hard phase finer has been adopted. However, this method also has its limitations, and the toughness obtained falls far short of that of high-speed tool steel. Usually, the amount of carbide contained in cemented carbide is about 80 to 90% by volume. In order to improve toughness depending on the application, cemented carbide is manufactured with a composition in which the amount of carbide is reduced to about 60% by volume, but the wear resistance rapidly decreases and it cannot be used as a material for cutting tools. .

As mentioned above, high-speed tool steel and cemented carbide used as materials for conventional cutting tools each have drawbacks.
In practice, they can only be used under conditions that do not cause these drawbacks. Therefore, there was a problem that the characteristics of high-speed tool steel or cemented carbide could not be fully exhibited.

Therefore, an object of the present invention is to provide a composite hard alloy material that maintains the excellent toughness characteristic of high-speed tool steel and at the same time has significantly improved wear resistance.

[Means for Solving the Problems] A composite hard alloy material according to the present invention includes a central portion made of a sintered hard alloy, and an outer peripheral portion covering the central portion and made of sintered alloy steel. The sintered hard alloy contains 50% by volume of one or more of carbides, nitrides, and carbonitrides of elements in groups IVa, Va, and Via of the periodic table in its central part.
The content is 95% by volume or less, with the remainder consisting of iron group metals and unavoidable impurities. The sintered alloy steel that constitutes the outer peripheral portion consists of a hard phase and a bonding phase. The hard phase is comprised of TiN particles containing 15% by volume or more and 70% by volume or less in the outer peripheral portion and having a particle size of 0.3 μm or less. The binder phase contains 30% by volume or more and 85% by volume or less in the outer peripheral portion,
Consists of alloy steel for dispersing and bonding the hard phase therein. The alloy steel contains Cr of 2.5% to 4.5% by weight, Mo of 1.5% to 5.0% by weight, W
2. 0 wt% or more and 6.0 wt% or less, C 0.3 wt% or more and 1.2 wt% or less, Co 1.5 wt% or more1
5% by weight or less, Mn 0. It contains 5% by weight or less of Si, and 0.5% by weight or less of Si, with the remainder consisting of Fe and unavoidable impurities.

Preferably, 50 atomic % or less of Ti in TiN is Zr, Hf, VSNb, or Ta5Cr.

It may be substituted with one or more elements selected from the group consisting of Mo1WSAl and SL.

Preferably, 50 atomic % or less of N in TiN may be substituted with one or more elements selected from the group consisting of B, C, and O.

Further, the thickness of the outer peripheral portion made of sintered alloy steel may be 0.05 or more and 0.3 or less of the total thickness of the composite hard alloy material.

[Function] According to the composite hard alloy material according to the present invention, TiN particles as a hard phase dispersed in the sintered alloy steel constituting the outer peripheral portion have wear resistance that is insufficient in high-speed tool steel alone. enhance TiN has a Vickers hardness of Hv2000k.
g/mm2, - Hv8 of high-speed tool steel for boat fishing.
The hardness is more than twice that of 00 to 1000 kg/mm2. By dispersing this hard TiN, the hardness of the high-speed tool steel becomes HvlO00 kg/mm2 or more, and a significant improvement in wear resistance is achieved. Furthermore, TiN has little reactivity with steel, suppresses adhesive wear during cutting, and improves the surface roughness of the cut surface.

According to the conventional technology for dispersing TiN as a hard phase into high-speed tool steel, the strength of the tool steel sharply decreases as the amount of TiN increases because the TiN particles are large. On the other hand, according to the present invention, the particle size of the TiN particles is reduced to 0.
．． By suppressing the thickness to 3 μm or less, the TiN particles are uniformly and finely dispersed, making it possible to reduce the decrease in strength.

In addition, if the particle size is 0. The amount of TiN particles less than 3 μm is 15
Appropriately, the content is at least 70% by volume and not more than 70% by volume. 1
If it is less than 5% by volume, the effect of improving wear resistance by dispersing TiN as a hard phase will be small, and if it exceeds 70% by volume, the toughness will decrease slightly.

On the other hand, the binder phase for dispersing and bonding the above-mentioned hard phase therein has a matrix composition close to that of the high-speed tool steel during quenching. Basically, it is most important to create a composition that does not precipitate primary carbides during the quenching process. The toughness provided by high speed tool steels is due to this matrix composition. Also in the present invention, the maximum effect can be obtained by employing this matrix composition. If the alloy components other than Fe are below the specified lower limit, sufficient strength cannot be obtained, and if they exceed the upper limit, the toughness decreases.

The hard phase to be dispersed in the matrix may be mainly composed of TiN, with some of the components of the binder phase matrix dissolved therein. In addition, up to 50 atomic % of Ti in TiN is replaced by Zr, Hf, and V.

Nb, Ta, Cr, Mo s Ws A Q and S
It is possible to substitute with one or more elements selected from the group i. Similarly, up to 50 atomic percent of N in TiN is
It is also possible to substitute with one or more elements selected from the group consisting of , C and 0. These substitutions are effective in improving the heat resistance, wear resistance, toughness, etc. of the alloy. However, substitution exceeding 50 atom % is not preferable because it impairs the properties of TiN.

The sintered alloy steel configured as described above can exhibit satisfactory characteristics as a tool material for cutting tools and the like.

However, by introducing a composite method using the above-mentioned sintered alloy steel as the outer peripheral portion, it is possible to improve the performance of the -layer.

First, by employing a sintered hard alloy, so-called cemented carbide, as the core material, it is possible to significantly improve the rigidity of the tool material as a whole. As a result, the machining accuracy of the tool improves, and the surface roughness of the surface machined by the tool improves.

In order to maintain consistency between the cemented carbide that makes up the core material and the sintered alloy steel that makes up the outer periphery, the coefficient of thermal expansion of the cemented carbide should be close to that of the sintered alloy steel. is valid.

Since the outer peripheral portion is made of the above-mentioned sintered alloy steel, a cutting tool edge with improved wear resistance can be obtained while maintaining the toughness of high-speed tool steel. Incidentally, coating the surface of the sintered alloy steel with a hard ceramic film brings about good results in further improving the performance. As the material for this film, TiN is preferable, but TiN
C or Ti (CN) may be used, and furthermore All, 0. may be coated.

[Example] FIG. 1 is a sectional view conceptually showing a composite hard alloy material according to the present invention. According to this figure, an outer peripheral part 1 made of sintered alloy steel covers a central part 2 made of sintered hard alloy.

Example 1 Average particle size as hard phase: 0. 40 1μm TiN particles
10% by volume, WC particles with an average particle size of 0.05 μm
, high-speed tool steel powder as a binder phase was blended to be 50% by volume, and mixed using a dry ball mill. The composition of the powder for high-speed tool steel is 4.0% by weight of C, Mo
was 3.5% by weight, W was 2.0% by weight, Co was 8.5% by weight, C was 0.5% by weight, and the remainder was Fe and unavoidable impurities. After coating the outer periphery of a rod made of cemented carbide with the alloy steel powder mixed in this way, cold isostatic pressing (
CIP, cold isostatic pre
ssing). The composition of cemented carbide is WC
is 75% by volume, Tic is 7.5% by volume, TaC is 4.0% by volume.
Co content was 13.5% by volume. The cemented carbide rod had a diameter of 5 mm and a length of 200 mm. In this way, a layer of alloyed steel powder with a thickness of 2 mm was formed.

This molded body was placed in a mild steel cylindrical container, heated to a temperature of 500° C. while being deaerated, and vacuum-sealed. Thereafter, this molded body was subjected to hot isostatic pressing treatment. The conditions for hot isostatic pressing are a temperature of 1130°C.
In this case, the pressure of Ar gas used as a pressure medium was set to 1000 kg/Cm2. A drill with a diameter of 6 mm was prototyped from the sintered body thus obtained. In the cross-sectional structure of this drill, a part made of cemented carbide with a diameter of 5 mm was located at the center, and a part made of sintered alloy steel was surrounded by a part made of sintered alloy steel with a thickness of 0.5 mm. Predetermined grooves and cutting edges were molded into the drill.

For comparison, a prototype drill made of sintered alloy steel without cemented carbide in its center was produced. Cutting tests were conducted using prototype drills of the present invention and comparison products, as well as commercially available drills made of cemented carbide and high-speed tool steel. The cutting conditions were as follows.

Work material: 550C Cutting speed: 50m/min Feed rate: 0. 25mm/ r ev machining depth:
The results of the 15 mm cutting test are shown in Table 1.

According to the test results in Table 1, with drills made of cemented carbide, wear is small in the early stages when the number of holes to be machined is small, but as the number of holes to be machined increases, subtle chipping occurs on the cutting edge, and this is the cause. It was observed that wear increased. Furthermore, the comparative product was slightly inferior to the invented product. When comparing the enlargement allowance of the processed hole, the inventive product had an enlargement of about 20 μm, while the comparative product had an enlargement of about 60 μm.

Example 2 A cylinder made of sintered alloy steel having a structure in which each particle was uniformly dispersed was prepared such that the hard phase particles having a predetermined structure form were 40% by volume and the matrix of high-speed tool steel was 60% by volume. It was done. The hard phase particles surround the TiN particles (Ti
It had a structure in which a solid solution of W Mo) (CN) was formed surrounding it. The average particle size of the hard phase particles was 0.08 μm, and the thickness of the solid solution surrounding the TiN particles was 0.01 μm. The composition of the high-speed tool steel constituting the matrix is 3.8% by weight of Cr;
Mo is 5.5% by weight, W is 2.5% by weight, Co is 10% by weight.
0% by weight, C was 0.45% by weight, and the remainder was Fe and unavoidable impurities. In addition, WC was 85% by volume and CO was 1% by volume.
A bar made of cemented carbide with a composition of 5% by volume was prepared. This cylinder made of sintered alloy steel and the rod made of cemented carbide were integrated by diffusion bonding. A cutting tool having a predetermined shape for an end mill was manufactured from the composite hard metal member thus obtained. A cutting test was conducted using this cutting tool under the following conditions.

Work material: 5KDI 1 (HRc 20) Cutting speed:
60m/m1rl Feed rate: 0.15mm/1 blade machining width: 10mm Machining depth: 30mm According to the cutting test results, machining can be performed without any problems if the end mill made of composite hard alloy material according to the present invention is used. The deviation of the side surface of the machined groove from the vertical line is
The accuracy was extremely high, with a maximum of 0.04 mm. In addition,
For comparison, when using end mills made of cemented carbide and high speed tool steel, no cutting was possible.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain an alloy material whose wear resistance is improved to a level comparable to that of cemented carbide while maintaining the toughness of high-speed tool steel. can. Furthermore, when used as a cutting tool, it has high rigidity and enables highly accurate cutting. Therefore, the composite hard alloy material of the present invention can be used as a material for cutting tools.
It can contribute to improving cutting efficiency and reliability.

[Brief explanation of drawings]

FIG. 1 is a sectional view conceptually showing a composite hard alloy material according to the present invention.

Claims (1)

[Scope of Claims] (1) A central portion made of a sintered hard alloy; and an outer circumference portion covering the central portion and made of sintered alloy steel, wherein the sintered hard alloy is made of a periodic table IVa, The sintered alloy steel contains 50% by volume or more and 95% by volume or less of Va, group VIa element carbides, nitrides, and carbonitrides in the central portion, and the remainder consists of iron group metals and unavoidable impurities. has a particle size of 0.
Contains 15% by volume or more and 70% by volume or less of a hard phase consisting of TiN particles of 3 μm or less, and 30% by volume or more and 85% by volume or less of a binder phase made of alloy steel for dispersing and bonding the hard phase therein. The alloy steel contains Cr of 2.5% to 4.5% by weight, Mo of 1.5% to 5.0% by weight, and W of 2.5% to 4.5% by weight.
．． 0% to 6.0% by weight, C 0.3% to 1.2% by weight, Co 1.5% to 15% by weight, Mn 0.5% by weight or less, Si 0.5% by weight
A composite hard alloy material containing the following, with the remainder consisting of Fe and unavoidable impurities. (2) 50 atomic% or less of Ti in the TiN particles is Zr, Hf, V, Nb, Ta
The composite hard alloy material according to claim 1, wherein the composite hard alloy material is substituted with one or more elements selected from the group consisting of , Cr, Mo, W, Al, and Si. (3) The composite hard alloy material according to claim 1 or 2, wherein 50 atomic % or less of N in the TiN particles is replaced with one or more elements selected from the group consisting of B, C, and O. . (4) The thickness of the outer peripheral portion is 0.05 or more and 0.3 or less of the total thickness of the composite hard alloy material,
The composite hard alloy material according to any one of claims 1 to 3.