JPH06336635A - Cemented carbide for cutting tool - Google Patents

Abstract

PURPOSE:To produce cemented carbide having excellent wear resistance and chipping resistance to a hard-to cut material such as stainless steel, in cemented carbide obtd. by adding the carbides or the like of specified elements to a WC-Co system by controlling the solid solution quantity of W and C in a bonding phase. CONSTITUTION:This cemented carbide for a cutting tool is constituted of a bonding phase contg. at least, by weight, 1 to 15% Co and a hard phase constituted of <=15% of one or more kinds among the carbides, nitrides and carbonitrides of 4a, 5a and 6a group elements excluding W, and the balance WC. Then, the quantity of W and C entering into solid solution in the bonding phase is respectively regulated to 1 to 15% and <=5% to the total quantity of the bonding phase. In the case of <1% solid solution quantity of W, the solid-solution strengthening of the bonding phase is insufficient to deteriorate its wear resistance, and welding is increased from the viewpoint of reaction resistance. In the case of >15%, the bonding phase is made brittle. In the case of >5% solid solution quantity of C, the m.p. of the bonding phase is reduced, and its affinity with the material to be cut is increased to cause the increase of welding at the time of milling and the chipping of the edge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cemented carbide for a cutting tool, which is used for milling, for example, and which is mainly used for machining an iron group alloy containing Ni, Co such as stainless steel and has excellent fracture resistance.

[0002]

2. Description of the Related Art Conventionally, a cemented carbide that has been widely used for cutting metal is a WC-C composed of a hard phase mainly composed of tungsten carbide and a binder phase of an iron group metal such as cobalt.
O-based alloy or WC-Co system above
Systems in which carbides, nitrides, carbonitrides, etc., of a, 5a, and 6a group metals are added are known. These cemented carbides are mainly used as cutting tools for cutting cast iron, carbon steel, stainless steel and the like.

Here, iron group metals such as cobalt exist as a liquid phase during sintering and serve to efficiently sinter high melting point carbides, nitrides, and carbonitrides, and brittle carbides,
It has the advantage of imparting toughness to nitride and carbonitride sintered bodies.

[0004]

However, when the cemented carbide as described above is used as a cutting tool, the iron group metal such as cobalt in the cemented carbide is essentially the same as the work-based iron-based metal. There is a problem that the affinity is good, and therefore the tool wear is increased.

Further, particularly in the case of milling, welding of the damaged material occurs on the tool edge, which accelerates deterioration of the edge such as chipping and shortens the tool life.

[0006]

As a result of repeated studies on the above problems, the present inventor has found that by controlling the amount of solid solution of tungsten and the amount of solid solution of carbon in the binder phase, it is possible to achieve The inventors have found that a cemented carbide having improved wear resistance and fracture resistance, which improves reactivity and weldability and suppresses strength reduction due to embrittlement of a binder phase, has been accomplished, and has led to the present invention. .

That is, the cemented carbide of the present invention comprises at least 1 to 15% by weight of cobalt as a binder phase component and carbides, nitrides and charcoals of elements of groups 4a, 5a and 6a in the periodic table excluding tungsten as a hard phase. At least one of the nitrides is 15% by weight or less, a cemented carbide consisting of the balance tungsten carbide and unavoidable impurities, and the amount of tungsten dissolved in the binder phase is 1 to 15% by weight based on the total amount of the binder phase. And the amount of carbon solid-dissolved in the binder phase is 5% by weight or less.

Here, the amount of tungsten solid-dissolved in the binder phase is set to 1 to 15% by weight of the total amount of the binder phase, because the solid solution amount of tungsten is less than 1% by weight. This is because the reinforcement is insufficient, the wear resistance is inferior, and the amount of welding increases from the viewpoint of reaction resistance, and if it exceeds 15% by weight, the binder phase becomes brittle. The solid solution amount of tungsten is particularly preferably 2 to 10% by weight based on the total amount of the binder phase.

Further, the amount of carbon solid-dissolved in the binder phase is set to 5% by weight or less of the total amount of the binder phase, because the melting point of the binder phase is lowered when the amount of carbon is more than 5% by weight, and the work material is This is because the affinity of the metal is increased and, for example, the welding is increased and the tip of the blade is chipped during milling. The amount of carbon solid-dissolved in the binder phase is preferably 4% by weight or less.

On the surface of the cemented carbide of the present invention, a hard layer having a thickness of 0.1 to 10 μm or a single phase or two or more layers is formed, and the hard layer is formed of a metal of Group 4a and Al of the periodic table. It may be composed of at least one of carbide, nitride, carbonitride, and oxide.

The present invention will be described in detail below. The cemented carbide of the present invention is composed of a hard phase and a binder phase, and the hard phase contains tungsten carbide, or 5 to 15% by weight of tungsten carbide, a carbide of a group 4a, 5a, or 6a metal of the periodic table, a nitride of the metal. When a component other than tungsten carbide is blended, the hard phase consists of a composite carbide solid solution or a composite carbonitride solid solution. The binder phase has an iron group metal such as Co as a main component, and Co is contained in a total amount of 5 to 15% by weight.

According to the cemented carbide of the present invention, the amount of solid solution of tungsten in the binder phase is 1 to 1 of the total amount of binder phase.
It is 5% by weight, but as a method for solid-dissolving tungsten in the binder phase, 1 to 1
5 wt% is replaced by metallic tungsten. Metallic tungsten is effective when the average particle size is 5 μm or less, and particularly 3 μm or less. Controlling the amount of carbon and / or adding it to tungsten carbide at the time of mixing raw materials
By controlling the addition amount of the carbides, nitrides, and carbonitrides of the 6a group element, the carbon amount in the total amount of the raw materials is suppressed, and the cobalt tungsten carbide (Co ₃ W ₃ C and / or Co ₆ W) is contained in the structure. Η consisting of ₆ C and / or Co ₂ W ₄ C)
Form a phase. Substituting W ₂ C or WCx (x <1) for part or all of WC used as the primary raw material,
There are methods to control the carbon content in the binder phase.

In producing the cemented carbide of the present invention, as a raw material powder, WC powder, periodic table 4a, 5a,
1 selected from carbides, nitrides and carbonitrides of 6a group elements
One kind or two or more kinds of powder, Co powder, and iron group metal powder are weighed as described above. Depending on the case, a part of cobalt is replaced with metallic tungsten, or WCx is used as a primary raw material.
(X <1) may be used. These are mixed and pulverized, molded by a known molding method such as press molding, and then fired.

The firing is carried out in a vacuum of 10 ^-1 to 10 ^-4 torr or under a condition of 100 torr or less in an inert atmosphere of nitrogen, argon or the like 1623 to 177.
It is carried out in the temperature range of 3K for 10 minutes to 2 hours.

In addition to cobalt, another iron group metal may be added as a binder phase.

[0016]

According to the present invention, 1 tungsten is contained in the binder phase.
When it is used as a cutting tool by reacting with 15 to 15% by weight of solid solution and the amount of carbon in the binder phase to 5% by weight or less, reaction with elements such as iron and chromium constituting the work material,
By suppressing the diffusion, the compatibility with the work material can be lowered, welding of the work material can be prevented, and chipping of the cutting edge can be reduced. This is because the solid solution of tungsten with a large atomic radius in cobalt disturbs the lattice of the binding metal phase, and the melting point of the binding metal increases by reducing carbon, which suppresses element diffusion. Is thought to be the cause. Further, it is generally said that when the solid solution amount of tungsten decreases, the solid solution amount of carbon increases, but in the present invention, as described above, the composition of the raw material and the addition method (W ₂ C or WCx) should be changed. This makes it possible to limit the amounts of tungsten and carbon that form a solid solution in the binder phase to a predetermined amount, and suppress the deformation and wear of the cutting tool.

[0017]

The present invention will be described below with reference to the following examples. As primary raw materials, WC powder, TiC powder, TiN powder, TaC powder, NbC powder, WCx powder, W powder and Co powder were weighed and mixed in the proportions shown in Table 1, crushed, and then SEK.
It was molded into a shape of 1203 and fired at 1673 ° C. for 1 hour in a vacuum of 10 ⁻² torr or less.

After crushing the obtained sintered body, the binder metal phase is selectively dissolved in an HCl solution, and the amounts of cobalt and tungsten are determined by ICP emission spectrometry. The amount of dissolution was measured. In addition, an η phase composed of a cobalt tungsten compound was confirmed by an X-ray diffraction method. Furthermore, a metal pool of about 5 to 10 μm was formed in the sintered body, and the amount of carbon in this portion was quantitatively analyzed by EPMA (X-ray microanalyzer). Further, the following cutting test was performed on each sample.

[Cutting Conditions] Work Material SUS304 Tool Shape SEK42AU3N Cutter Shape MSE45125R Speed 200 m / min. Feed 0.2 mm / tooth Depth of cut 2 mm Cutting time 810 (sec) Dry type And tool life judgment condition (average flank wear 0.2 m
m, maximum flank wear of 0.5 mm), or cutting was performed for a maximum of 810 seconds. The amount of flank wear and the amount of boundary wear after cutting were measured. The results are shown in Table 1.

[0020]

[Table 1]

According to Table 1, the samples having a solid solution amount of tungsten in cobalt of less than 1% by weight (Sample Nos. 6 to 8) suffer from defects and abnormal wear which are considered to be caused by welding, and the tool life is short. I understand. Further, it can be seen that the sample having a solid solution amount of tungsten of more than 15% by weight (Sample No. 12) has low toughness and the cutting edge is broken in a short time, which is not suitable for a cutting tool. On the other hand, the solid solution amount of tungsten is 1 to
With the cemented carbide of the present invention in the range of 15 weights, stable cutting performance could be exhibited in cutting.

Samples Nos. 19 and 20 are examples in which TiN powder was used instead of TiC powder to prepare the cemented carbide of the present invention.

[0023]

As described above, when the cemented carbide of the present invention is used as a cutting tool by solidifying 1 to 15 wt% of tungsten and 5 wt% or less of carbon in the binder phase, It suppresses the reaction and diffusion of elements such as iron and chromium that make up the work material, prevents the welding of the work material due to this, and resists the cutting performance of difficult-to-cut materials such as stainless steel, which is heavily welded. The chipping property and wear resistance can be significantly improved,
The tool life can be extended.

Claims (1)

[Claims] 1. At least 1 cobalt is used as a binder phase component.
-15% by weight, 15% by weight or less of at least one of carbides, nitrides, and carbonitrides of elements of groups 4a, 5a, and 6a of the periodic table excluding tungsten as a hard phase, and the balance tungsten carbide and unavoidable impurities In a cemented carbide, the amount of tungsten that forms a solid solution in the binder phase is 1 to 15% by weight of the total amount of the binder phase, and the amount of carbon that forms a solid solution in the binder phase is 5% by weight or less. Cemented carbide for cutting tools characterized by