JP2002166306A - Cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend service life of a tool by largely improving abrasion resistance and anti-plastic deformation performance in high speed and high efficiency cutting of hard-to-cut material such as stainless. SOLUTION: This cutting tool comprises a coating layer on the surface of base material of cemented carbide comprising hard phase components of WC and more than one sort of metal carbides, nitrides, and carbon nitrides selected from a group of groups 4a, 5a, and 6a in a periodic table, and coupling phase components of more than one sort of iron group metals. Thermal conductivity of the base material of cemented carbide at 1000 deg.C is 70% or more of that at room temperature. Such cemented carbide is used for high speed and high efficiency cutting of hard-to-cut material such as stainless.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting tool which has a high thermal conductivity even at a high temperature and is particularly suitable for high-speed cutting of difficult-to-cut materials whose cutting temperature rises.

[0002]

2. Description of the Related Art Conventionally, a cemented carbide widely used for metal cutting is a WC-hard alloy composed of a hard phase mainly composed of tungsten carbide and a binder phase of an iron group metal such as cobalt.
Periodic Table 4 for Co-based alloy or WC-Co-based alloy
There are known systems to which carbides, nitrides, carbonitrides, and the like of metals of groups a, 5a, and 6a are added. In the latter case, solid solution particles of WC and carbides, nitrides, and carbonitrides of metals of Groups 4a, 5a, and 6a of the periodic table are added to the hard phase and the binder phase.

[0003] These cemented carbides are mainly used as cutting tools for cutting cast iron, carbon steel and the like, but recently, application to cutting stainless steel has been advanced. Since this stainless steel has characteristics such as excellent corrosion resistance, oxidation resistance and heat resistance, it is applied in a wide range of fields and the amount of processing is increasing year by year.

However, stainless steel causes work hardening,
It is known as a representative of difficult-to-cut materials due to its low thermal conductivity and high affinity with tool materials.

[0005] Among WC cemented carbides for cutting tools, JIS B 4053 is generally used for cutting stainless steel.
According to (1996), a cemented carbide classified into the so-called M series is used. This M series mainly includes WC-
TiC-Ta (Nb) C-Co-based cemented carbide is used, and TiC and Ta (Nb) are used to impart toughness.
C is added in a relatively small amount.

[0006]

However, even when stainless steel is cut with a conventional M-series cemented carbide cutting tool, the cutting tool wears greatly, shortens the tool life in a short time, and provides good performance for a long time. There is a problem that it is difficult to perform a proper cutting.

In addition, the primary boundary is severely damaged by cutting resistance received from a work surface hardened by cutting stainless steel, and the tool life is shortened in a short time.

It is an object of the present invention to provide a cutting tool having improved wear resistance and plastic deformation resistance and a long tool life even when cutting difficult-to-cut materials such as stainless steel.

[0009]

The inventor of the present invention has repeatedly studied the above-mentioned problems and found that the base metal of the cemented carbide is 1000
By setting the thermal conductivity at 70 ° C. to 70% or more of the thermal conductivity at room temperature, it is possible to reduce the influence of thermal shock due to a rapid temperature change during machining of difficult-to-cut materials. The present invention is based on the finding that a cutting tool having excellent cutting performance for high-speed and high-efficiency machining of difficult-to-cut materials can be obtained by suppressing the deterioration of the mechanical properties and maintaining the mechanical strength at a high temperature. Reached.

[0010] Further, in the conventional cutting tool, a defect considered to be caused by welding occurs to deteriorate the machined surface state of the work material. In the present invention, however, the heat conduction of the cemented carbide base material at 1000 ° C. When the rate is 70% or more of the thermal conductivity at room temperature, the cemented carbide base material itself is strengthened, and the fracture resistance can be improved.

That is, the cutting tool of the present invention comprises, as a hard phase component, at least one of carbides, nitrides and carbonitrides of metals selected from the group consisting of WC and groups 4a, 5a and 6a of the periodic table; In a cutting tool having a coating layer on a surface of a cemented carbide base material containing at least one of iron group metals as a binder phase component, the thermal conductivity of the cemented carbide base material at 1000 ° C. is 70% at room temperature. % Or more.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. The cutting tool of the present invention has a coating layer on the surface of a cemented carbide base material. This cemented carbide base material is composed of a hard phase and a binder phase.

The hard phase is composed of WC and periodic table 4a, 5a, 6a.
It is composed of at least one of carbides, nitrides, and carbonitrides of metals selected from the group consisting of group metals. And this hard phase is WC
And two or more solid solutions (composite carbide solid solutions or composite carbonitride solid solutions) of carbides, nitrides, and carbonitrides of metals selected from the group consisting of the WC and groups 4a, 5a, and 6a of the periodic table. Is preferred.

The binder phase is mainly composed of an iron group metal such as Co, and is preferably contained in the cemented carbide at a ratio of 5 to 15% by weight. When the proportion of the binder phase is higher than this range, the hardness and the compressive strength are reduced, the wear resistance is reduced, and the wear of the tool may be increased. On the other hand, when the proportion of the binder phase is lower than the above range, the bonding between the hard phases is not sufficient, so that the toughness is insufficient and there is a possibility that a tool breakage may occur during processing.

The cemented carbide according to the present invention is characterized in that the thermal conductivity of the cemented carbide base material at 1000 ° C. is 70% or more of the thermal conductivity at room temperature.
The reason for setting the above range is that when the thermal conductivity at 1000 ° C. is lower than 70%, the amount of tool wear and damage becomes remarkable due to the influence of thermal shock due to a rapid temperature change during machining of difficult-to-cut materials.

In the cemented carbide base material, two or more B1 type solid solutions exist, and at least one of the B1 type (cubic type) solid solutions is a B1 type solid solution having a high Zr content. preferable. This is because a B1 type solid solution having a high Zr content is very excellent in toughness and plastic deformation resistance at high temperatures.

The B1 type solid solution having a high Zr content is as follows:
In energy dispersive X-ray diffraction, the peak intensity indicated by Zr is greater than 50% of the peak intensity indicated by W,
Preferably it is 50 to 120%. When the peak intensity indicated by Zr is 50% or less of the peak intensity indicated by W, the content of W becomes relatively high, so that the hardness of the alloy cannot be increased, and high wear resistance is obtained. , Plastic deformation resistance cannot be exhibited.

On the other hand, a solid solution other than a solid solution having a high Zr content is a metal other than Zr, that is, Ti, V, C
One or both of a solid solution of WC with one or more of r, Mo, Hf, Nb and Ta and a solid solution of Zr and WC having a low content. As described above, the solid solution containing no Zr or having a low content thereof has a peak intensity indicated by Zr less than 50% of a peak intensity indicated by W in energy dispersive X-ray diffraction.

Here, the following method can be used for the temporary confirmation of those having a high Zr content and those other than the B1 type solid solution. An arbitrary cross section of the sintered body is ground and polished, and the mirror surface portion is etched with Murakami reagent.
Observe at 0-1000x. At this time, since the degree of etching of the B1 type solid solution differs depending on the Zr content, the B1 type solid solution can be easily confirmed.

The B1 type solid solution having a high Zr content desirably exists in the alloy as a phase having an average particle diameter of 3 μm or less. This is because, when the average particle size exceeds 3 μm, the B1-type solid solution has poor wettability with the binder phase, so that the strength of the entire alloy decreases. Optimally an average particle size of 1
It is about μm.

The coating layer coated on the cemented carbide base material is
Examples of the material include carbides, nitrides, carbonitrides, and TiAlN, ZrO ₂ , and Al ₂ O _{3 of} metals of Groups 4a, 5a, and 6a of the periodic table including TiC, TiN, and TiCN. CVD with thickness of 0.1-20μm
It is desirable to form by the method or the PVD method.

In producing the cemented carbide of the present invention, WC powder, periodic table Nos. 4a, 5a,
2 selected from carbides, nitrides and carbonitrides of group 6a metals
The above powders and Co powders are weighed as described above, mixed and pulverized, molded by a known molding method such as press molding, and then fired.

The firing is performed in a vacuum of 10 to 10 ^-1 Pa in a temperature range of 1623 to 1823 K for 10 minutes to 2 hours. The region where the ratio of Zr in the metal selected from the group consisting of groups 4a, 5a and 6a in the cemented carbide matrix structure, which is a feature of the present invention, is higher than that in the cemented carbide matrix. Is formed in the vicinity of the surface of the cemented carbide base material by adjusting the ratio of the Zr compound in all the compounds constituting the so-called B1 type solid solution of the primary raw material, and further from the vicinity of the liquid phase appearance temperature to the sintering temperature. It can be obtained by slowing down the rate of temperature rise.

After processing into the shape of a cutting tool and cleaning, the surface is coated with a coating layer. Each mixing ratio of the raw material powder is W
C powder 70 to 95% by weight, the periodic table 4a, 5
a, 6a metal compound powder is 0.1 to 20% by weight, and iron group metal powder is 5 to 20% by weight, more preferably WC.
85 to 95% by weight of powder, 0.5 to 5% by weight of powder of group 4a, 5a and 6a metal compound, 5 to 5% of powder of iron group metal
10% by weight.

[0025]

The present invention will be described below with reference to the following examples. The raw material powder having the composition shown in Table 1 was mixed and pulverized, molded into a CNMG432 shape, and fired at 1773 K for 1 hour in a vacuum of 1 Pa or less.

With respect to the sintered body thus obtained,
The thermal conductivity at room temperature (RT: 25 ° C) and the thermal conductivity at high temperature (HT: 1000 ° C) were measured using a laser flash method according to JIS R1611 (manufactured by Vacuum Riko: TC-7000).

Also, the following method was used to primarily confirm the B1 type solid solutions having a large Zr content and those other than the Zr content. Grind and polish any section of the sintered body,
The mirror surface is etched with Murakami's reagent.
Observed at 000x. At this time, since the degree of etching of the B1 type solid solution was different depending on the Zr content, the B1 type solid solution could be easily confirmed.

For the B1 type solid solution having a high Zr content, the above tool was ground by about 2,000 μm from the rake face side with a surface grinder or the like, and then the sample obtained by mirror-polishing the ground face was subjected to SEM electron microscopy. (Backscattered electron image) B1 type solid solution (gray) which can be confirmed in an arbitrary region (20 μm × 20 μm) in observation can be distinguished from solid solution having a different color, and the Zr content is measured by an X-ray microanalyzer (PV9800). And those having an X-ray peak intensity indicated by Zr of 50% or more of the X-ray peak intensity indicated by W were defined as a solid solution having a high Zr content. The results are shown in Table 1.

[0029]

[Table 1]

After processing the obtained sintered body into a cutting tool shape,
A titanium-alumina composite film of about 5 μm was coated by a CVD method.

Test Example Using the obtained cutting tool, stainless steel was cut. Then, the flank wear of the cutting tool (the flank wear caused by the work material directly rubbing the flank of the tool) and the nose deformation were measured.

The cutting conditions are as follows. [Cutting Condition 1] Work Material SUS304 Tool Shape CNMG120408 Speed 200m / min Feed 0.2mm / rev Depth of Cut 2mm Cutting Fluid Available (Water-soluble) Cutting Time 40 seconds per pass repeated 15 times (10
Minutes) In addition, in order to evaluate the plastic deformation resistance and fracture resistance of the cutting tool, the presence or absence of deformation and the presence or absence of damage were confirmed.

The results are shown in Table 2.

[0034]

[Table 2]

As can be seen from Table 2, the products of the present invention of Sample Nos. 1, 2 and 3 have excellent wear resistance and also excellent plastic deformation resistance and fracture resistance. The flank wear was 0.25 m when cutting under the above conditions.
m or less, it was determined to have practical wear resistance. Further, the amount of plastic deformation of the cutting edge is considered to affect the dimensional accuracy of the workpiece, and it is determined that practical dimensional correction is not required when the amount is less than 0.15 mm.

However, the sample No. 1 having a large Zr-containing B1 type solid solution having a large particle size of 3.2 μm was used. With respect to 2, the cutting performance was excellent in the cutting condition 1, but when only the feed of the cutting condition was set to 0.3 mm / rev with respect to the cutting condition 1, chipping occurred.

On the other hand, the sample No. For 4, 5, and 6, there was a problem in any of the plastic deformation resistance, fracture resistance, and wear resistance. That is, the sample No. Sample No. 7 had a wear amount larger than 0.25 mm and had a problem in wear resistance. Sample No. 4, 5, 6, and 7 had a deformation amount of 0.15 mm or more, and had a problem in plastic deformation resistance. Sample No. Nos. 4 and 5 had a problem in fracture resistance.

[0038]

As described above, the coated cemented carbide base material of the present invention has a thermal conductivity at 1000 ° C. of at least 70% of the thermal conductivity at room temperature. Wear resistance in high speed and high efficiency cutting of stainless steel is greatly improved, and tool life can be extended.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 16/30 C23C 16/30

Claims (3)

[Claims] 1. A carbide, nitride or carbonitride of a metal selected from the group consisting of WC and groups 4a, 5a and 6a of the periodic table.
In a cutting tool having a coating layer on the surface of a cemented carbide base material having at least one species as a hard phase component and at least one type of iron group metal as a binder phase component, the thermal conductivity of the cemented carbide base material at 1000 ° C. Is 70% or more of the thermal conductivity at room temperature. 2. A cemented carbide base material comprising two or more B1 type solid solutions, and at least one of the B1 type solid solutions is a B1 type solid solution having a high Zr content. The cutting tool according to claim 1. 3. The cutting tool according to claim 2, wherein the B1 type solid solution phase having a high Zr content in the cemented carbide base material has an average particle size of 3 μm or less.