JP2021134364A - Wc-based hard metal-made cutting tool excellent in plastic deformation resistance and defect resistance, and surface-coated wc-based hard metal-made cutting tool - Google Patents

Abstract

To provide a WC-based hard metal cutting tool and a surface-coated WC-based hard metal cutting tool, exerting excellent plastic deformation resistance and defect resistance in the intermittent cutting work for alloy steels or the like.SOLUTION: A WC-based hard metal-made cutting tool is characterized in that the cutting tool comprising a WC-based hard metal as a base material consists of in mass%, 6.0 to 14.0% of Co, 0.1 to 1.4% of Cr3C2 and the balance of WC with inevitable impurities, or further includes 4.0 mass% or less in total amount of one or more selected from TaC, NbC, TiC and ZrC, and when analyzing the grain size distribution of a binder phase in the cross section of the hard metal and defining a cumulative 10% grain area as A10 and cumulative 90% grain area as A90, A10 is 0.15 μm2 or more but less than 0.25 μm2 and A90/A10 is 8.0 or more but less than 11.0. In a surface-coated WC-based hard metal-made cutting tool, a hard coating layer is formed on at least a cutting edge of the cutting tool.SELECTED DRAWING: None

Description

The present invention provides a WC-based cemented carbide cutting tool (also referred to as "WC-based cemented carbide tool") having excellent plastic deformation resistance and excellent fracture resistance in intermittent cutting of alloy steel and the like. The present invention relates to a cutting tool made of a surface-coated WC-based cemented carbide.

Since the WC-based cemented carbide has high hardness and toughness, the WC-based cemented carbide tool based on the WC-based cemented carbide exhibits excellent wear resistance and has a long life over a long period of use. Known as a cutting tool.
However, in recent years, various proposals have been made to further improve the cutting performance and tool life of WC-based cemented carbide tools according to the type of work material, cutting conditions, and the like.

For example, in Patent Document 1, a hard phase containing tungsten carbide as a main component and an iron group element (containing cobalt, and the content of cobalt is preferably 8% by mass or more in a cemented carbide) are the main components. In a cemented carbide provided with a bonding phase, when the number of tungsten carbide particles is A and the number of tungsten carbide particles having one or less contact points with other tungsten carbide particles is B, B / A. By satisfying ≤0.05, the plastic deformation resistance of cemented carbide is improved, and as a result, the life of WC-based cemented carbide tools is extended in wet continuous cutting of carbon steel and stainless steel. It is proposed to try.

In Patent Document 2, the amount of Co is 10 to 13% by mass, the ratio of the amount of Cr to the amount of Co is 2 to 8%, and at least one of TaC and NbC has a total amount of TaC and NbC of 0.2 to 0.5% by mass. In a WC-based cemented carbide tool containing WC in the range of 88.6 HRA to 89.5 HRA in hardness, the WC integrated particle size 80% diameter D80 and the integrated particle size 20 in the area ratio on the polished surface The ratio D80 / D20 of% diameter D20 is in the range of 2.0 ≦ D80 / D20 ≦ 4.0, D80 is in the range of 4.0 to 7.0 μm, and the WC adhesion degree c is 0.36 ≦ c. By setting ≤0.43, it has been proposed to prevent adhesion of the work material and improve fracture resistance in the cutting process of a difficult-to-cut material typified by stainless steel.

In Patent Document 3, in the WC-based cemented carbide tool, when the component composition of the WC-based cemented carbide _{is expressed by WC-x mass% Co-y mass% Cr 3} C _2- z mass% VC, 6 ≦ x ≦ 14, 0.4 ≦ y ≦ 0.8, 0 ≦ z ≦ 0.6, (y + z) ≦ 0.1x are satisfied, and the WC adhesion degree C of the WC-based cemented carbide is C = 1-V. _b ^{When expressed in α} _{· exp (0.391 · L), the value V b} of the bonded phase volume ratio of the WC-based cemented carbide in this equation is 0.11 ≦ V _b ≦ 0.25, and (WC particles). The value L of (standard deviation of particle size distribution) / (average WC particle size) is within the range of 0.3 ≦ L ≦ 0.7, and the value of the coefficient α is 0.3 ≦ α ≦ 0.55. By using a WC-based cemented carbide having a satisfactory WC adhesion degree C, in cutting of Al alloys, carbon steels, etc., the toughness is improved without lowering the hardness and rigidity, and the WC group with improved fracture resistance. Carbide tools have been proposed.

In Patent Document 4, when the WC-WC bonding interface length is L1 and the WC-Co bonding interface length is L2 in the WC-based cemented carbide tool,
R> (0.82-0.086 × D) × (10 / V)
It has been proposed to improve the heat-resistant plastic deformation and toughness of the WC-based cemented carbide tool in the cutting process of the Ni-based heat-resistant alloy by satisfying the above equation.
R = (L1) / ((L1) + (L2))
D: WC area average particle size (μm), which is in the range of 0.6 ≦ D ≦ 1.7.
Here, D refers to the particle size of WC when the area ratio of WC is 50%.
V: The bound phase volume (vol%), which is in the range of 9 ≦ V ≦ 14.

In Patent Document 5, in% by weight, Cr or / and Cr compounds: 0 to 4% (in terms of Cr), V or / and V compounds: 0 to 4% (in terms of V), TaC: 0 to 2%, TiC: 0-2%,
N or / and N compounds: 0 to 1% (in terms of N), Co: 0.1 to 10%, WC and unavoidable impurities: a composition consisting of the residue, and a Co average of 0.06 to 30 nanometers. It has a thickness (CFP), and during sintering, it is high by applying a pressure of 3 atm to 200 atm using gas as a pressure medium in a part or the whole range of the temperature range of 900 ° C to 1600 ° C during temperature rise. WC-Co-based cemented carbide parts for cutting tools with densification have been proposed, and these WC-Co-based cemented carbide parts, preferably, have an average particle size of WC of 1 μm or less and a CFP of 0.06 to 30 nm. It is said that the toughness of ultrafine low Co cemented carbide parts in the range of
However, CFP has a Co average thickness (nm) and is
CFP = 0.58 * A / (100-A) * R
It is a value calculated from A: Co (% by weight) and 2R: WC average particle size (nm).

Japanese Patent No. 6256415 JP-A-2017-888999 JP-A-2017-148895 JP-A-2017-179433 Japanese Unexamined Patent Publication No. 7-305136

According to the conventional WC-based cemented carbide tools proposed in Patent Documents 1 to 5, the WC-based carbide tool is controlled by controlling the number of contact points between WC-WC particles, the particle size of WC, the degree of WC adhesion, the manufacturing conditions, and the like. The cutting performance and tool characteristics of cemented carbide tools have been improved.
However, the conventional tools do not have sufficient plastic deformation resistance and fracture resistance in intermittent cutting such as end milling of alloy steel, and crack extension or bonding phase at the interface of WC-WC particles. It was not possible to sufficiently suppress the occurrence of defects and tool deformation due to the occurrence of cracks due to stress concentration on the steel, and therefore the tool life was short.

Therefore, the present inventors have developed a WC-based cemented carbide tool that exhibits excellent plastic deformation resistance and fracture resistance in intermittent cutting such as end milling of alloy steel. Focusing on the morphology of the bound phase, we conducted diligent research and obtained the following findings.

That is, in the WC-based cemented carbide tools shown in Patent Documents 1 to 4, improvements are made mainly focusing on WC particles, and in the WC-based cemented carbide tools shown in Patent Document 5, mainly CFP. However, the present inventors have changed the viewpoint from the conventional technique and conducted research focusing on the morphology of the bonded phase. As a result, the bonded phase particles of the WC-based cemented carbide (the bonded phase particles of the WC-based cemented carbide ( By adjusting the sintering conditions, the main body is Co particles), and when a predetermined number of bonded phase particles having an appropriate size are provided, that is, the area occupied by one bonded phase particle when the cumulative particle area is 10%. Is A10, and the area occupied by one bonded phase particle when the cumulative 90% particle area is A90, A10 is 0.15 μm ² or more and less than 0.25 μm ² , and A90 / A10 is 8.0 or more. If it is less than 11.0, the WC skeleton structure becomes strong, and as a result, the plastic deformation resistance is improved. It has been found that when the tool is subjected to cutting, the life of the tool can be extended by improving the toughness and the fracture resistance.

The present invention has been made based on the above findings.
"(1) In a cutting tool made of WC-based cemented carbide based on WC-based cemented carbide,
The composition of WC-based cemented carbide, a 6.0 to 14.0 wt% of Co and _Cr 3 _{C 2} as the binder phase forming component containing 0.1 to 1.4 wt%, the balance being WC and Consists of unavoidable impurities
The particle size distribution of the bonded phase was analyzed for the cross section of the WC-based cemented carbide, and the area occupied by one bonded phase particle when the cumulative 10% particle area was occupied by A10 and one bonded phase particle when the cumulative 90% particle area was occupied. When the area is A90, A10 is 0.15 μm ² or more and ^{less than 0.25 μm 2} , and A90 / A10 is 8.0 or more and less than 11.0. Manufactured cutting tool.
(2) The WC-based cemented carbide is characterized by further containing at least one selected from TaC, NbC, TiC and ZrC in a total amount of 4.0% by mass or less (1). The WC-based cemented carbide cutting tool described.
(3) A surface-coated WC-based cemented carbide cutting characterized in that a hard coating layer is formed on at least the cutting edge of the WC-based cemented carbide cutting tool according to (1) or (2). tool. "
It is characterized by.
Incidentally, the _{(1), (2) Cr} 3 C 2, TaC in, NbC, TiC, content of ZrC is, Cr content measured for the cross section of the WC-based cemented carbide, Ta amount, Nb amount, Ti amount, The amount of Zr is a value converted into carbide.
Further, in the present specification, when "~" is used to indicate a numerical range, it means that the lower limit and the upper limit of the numerical value are included.

The WC-based cemented carbide tool and the surface-coated WC-based cemented carbide cutting tool according to the present invention include Co, Cr ₃ C ₂ , which are components of the WC-based cemented carbide constituting the substrate, and further, TaC, NbC, and so on. TiC and ZrC have a specific composition range, and the particle size distribution of the bonded phase is analyzed. When the area occupied by one phase particle is A90, A10 is 0.15 μm ² or more and ^{less than 0.25 μm 2} , and A90 / A10 is 8.0 or more and less than 11.0. As a result of the skeleton structure being firmly assembled, it has the effect of improving the plastic deformation resistance.
Therefore, the WC-based cemented carbide tool and the surface-coated WC-based cemented carbide cutting tool of the present invention have a long life of the tool due to improved toughness and fracture resistance in intermittent cutting such as end milling of alloy steel. Is planned.

Hereinafter, the present invention will be described in detail.

Co:
Co is contained as a main bonded phase forming component of the WC-based cemented carbide, but if the Co content is less than 6.0% by mass, sufficient toughness cannot be maintained, while the Co content is 14.0. If it exceeds% by mass, it softens rapidly, the desired hardness required for a cutting tool cannot be obtained, and deformation and wear progress become remarkable. Therefore, the Co content in the WC-based cemented carbide is set to 6. It was defined as 0 to 14.0% by mass.

Cr ₃ C ₂ :
Cr ₃ C ₂ is a WC-based cemented carbide in which Cr is dissolved in Co forming the main bonding phase to suppress the growth of the WC phase forming the hard phase, and the particle size of the WC phase is made finer. To increase toughness by forming a fine-grained / uniform-grained structure. However, this action is _{insufficient when the Cr 3} C ₂ content is less than 0.1% by mass, while when the content exceeds 10% with respect to the Co content, a composite carbide of Cr and W is produced. Precipitates, the toughness decreases, and it becomes the starting point for the occurrence of defects.
Since the upper limit of the Co content is 14.0% by mass in the present invention, the upper limit of Cr ₃ C ₂ is 1.4% by mass, which is 10% of the upper limit of the Co content.
_{Therefore, the Cr 3} C ₂ content in the WC-based cemented carbide was determined to be 0.1 to 1.4% by mass.

TaC, NbC, TiC, ZrC:
The WC-based cemented carbide of the present invention can further contain at least one selected from TaC, NbC, TiC and ZrC as a component thereof in a total amount of 4.0% by mass or less.
Ta, Nb, Ti, and Zr all have the effect of increasing the hardness by solid solution in Co forming the main bonding phase, but when the total content in terms of carbides exceeds 4.0% by mass. , The toughness is lowered by the precipitation of carbides, which serves as a starting point for the occurrence of defects.
Therefore, when at least one selected from TaC, NbC, TiC and ZrC is contained as a component in the WC-based cemented carbide, the total content may be 4.0% by mass or less. desirable.
_{The content of Cr 3} C ₂ , TaC, NbC, TiC, and ZrC described above is the amount of Cr, Ta, Nb, Ti, and Zr measured by EPMA for the WC-based cemented carbide, all of which are carbides. It is a converted value.

Particle size distribution of the bonded phase In the WC-based cemented carbide, by defining the particle size distribution of the bonded phase in the range, a large number of bonded phase particles of appropriate size are provided, and the WC skeleton structure is firmly assembled. It is possible to obtain a structure that is sown and has excellent plastic deformation resistance.
Specifically, the particle size distribution of the bonded phase in the WC-based superhard alloy is analyzed, and the area occupied by one bonded phase particle when the cumulative particle area is 10% is A10, and the area occupied by the bonded phase particle when the cumulative 90% particle area is one. When the area occupied by the particles is A90, ^{it can be obtained by defining that A10 is 0.15 μm 2} or more and less than 0.25 μm ² and A90 / A10 is 8.0 or more and less than 11.0.
On the other hand, when A10 is ^{less than 0.15 μm 2} , there are many fine bonds and the coarse bonding phase is insufficient, so that the plastic deformation resistance is not sufficient, and when A10 is 0.25 μm ² or more, Since there are many coarse bonded phases and the fine bonded phases are insufficient, the fracture resistance is not sufficient, so that the desired effect cannot be exhibited. Further, when A90 / A10 is less than 8.0, the particle size distribution of the bonded phase is narrow and the structure becomes homogeneous, so that the fracture resistance is improved, but the skeleton structure of the WC is divided and sufficient plastic deformation resistance is exhibited. It is difficult, and when A90 / A10 is 11.0 or more, a large number of coarse bonded phases are present, and the coarse bonded phase becomes the starting point of fracture, so that sufficient fracture resistance cannot be exhibited.
For the extraction of the bound phase from the SEM image, for example, the image analysis software ImageJ can be used, and the area of each particle of the extracted bound phase is accumulated from the particles having the smallest area, and the cumulative area ratio is the total area of the bound phase. The bonded phase area when it becomes 10% of the above can be obtained as A10, and the bonded phase area when the cumulative area ratio becomes 90% of the total area of the bonded phase can be obtained as A90. In the present invention, each bonded phase region divided by WC in a cross-sectional image of one WC-based cemented carbide is referred to as a bonded phase particle.

The WC-based cemented carbide tool of the present invention can be produced, for example, by the following steps.
First, a raw material powder composed of coarse-grained WC powder, fine-grained WC powder, coarse-grained Co powder, fine-grained Co powder, and Cr ₃ C ₂ powder having a predetermined average particle size, or, if necessary, TaC. A mixed powder is prepared by blending and mixing a raw material powder containing one or more of powder, NbC powder, TiC powder, and ZrC powder so as to have a predetermined composition.
Then, the mixed powder is molded to prepare a powder compact, and the powder compact is subjected to a solid phase rearrangement step (pressurization at 1000 to 1100 ° C. for 300 to 1100 minutes) in a pressurized atmosphere. After that, a WC-based cemented carbide is produced by low-temperature sintering (1350 to 1400 ° C., 60 to 120 minutes).
Then, the WC-based cemented carbide can be machined and ground to produce a WC-based cemented carbide tool having a desired size and shape.

Further, at least the cutting edge of the WC-based cemented carbide, Ti-Al-based, carbide Al-Cr system and the like, nitrides, carbonitrides or hard film such as _Al 2 _{O 3,} PVD, growth of CVD etc. By forming a coating by the film method, a cutting tool made of a surface-coated WC-based cemented carbide can be manufactured.
When manufacturing a cutting tool made of a surface-coated WC-based cemented carbide, the type of hard film and the film forming method may be a film type and a film forming method already well known to those skilled in the art, and are particularly limited. It is not something to do.

The WC-based cemented carbide tool and the surface-coated WC-based cemented carbide tool of the present invention will be specifically described with reference to Examples.

<< WC-based carbide tool of the present invention >>
(A) First, as the powder for sintering, coarse WC powder having an average particle size (d50) of 4.0 to 8.0 μm and fine particles having an average particle size (d50) of 0.5 to 2.0 μm are shown in Table 1. WC powder, coarse Co powder with an average particle size (d50) of 3.0 to 4.0 μm, fine Co powder with an average particle size (d50) of 0.5 to 1.5 μm, and an average particle size of 1.0 to 3 in the range of .0μm, _Cr 3 _{C 2} powder, TaC powder, NbC powder, TiC powder, to prepare a ZrC powder. The average particle size (d50) of the powder was calculated on a volume basis.
These powders were blended so as to have the blending composition shown in Table 1 to prepare a powder for sintering.
Table 1 shows the compounding composition (mass%) of various powders.

(B) The sintering powder blended in the blending composition shown in Table 1 is wet-mixed with a ball mill for 72 hours, dried, and then press-molded at a pressure of 100 MPa to prepare a powder compact having a predetermined shape. bottom.

(C) Then, under the conditions shown in Table 2, a WC cemented carbide was prepared through a pressure calcining step (1000 to 1100 ° C., 300 to 1100 minutes) and a low-temperature sintering step.

(D) Next, the WC-based cemented carbide is machined and ground to prepare WC-based cemented carbide tools 1 to 10 (hereinafter referred to as tools 1 to 10 of the present invention) having an insert shape of CNMG120408-GM. bottom. Table 3 shows the manufacturing conditions and composition of the tool of the present invention.

≪Comparative example WC-based carbide tool≫
For comparison, WC-based cemented carbide tools 1 to 10 of Comparative Example (hereinafter referred to as Comparative Example Tools 1 to 10) were manufactured.
The manufacturing process is performed by sintering under normal conditions using the raw material powder shown in Table 4. Specifically, the sintering powder blended in the compounding composition shown in Table 4 is used in a ball mill 72. After wet mixing for hours and drying, press molding was performed at a pressure of 100 MPa to prepare a powder compact, and the heating temperature: 1360 ° C. or higher and 1500 ° C. or lower and the heating holding time: 30 to 120 minutes shown in Table 5 were obtained. , A WC-based cemented carbide sintered body is produced by sintering under normal conditions of a vacuum atmosphere, and this is machined and ground to form an insert shape of CNMG120408-GM.

≪Measurement of area ratio of bonded phase and number of bonded phases≫
With respect to the cross section of the WC-based cemented carbide of the tools 1 to 10 of the present invention and the tools 1 to 10 of the comparative example, the contents of Co, Cr, Ta, Nb, Ti, and Zr, which are the components thereof, were measured at 10 points by EPMA. The average value was taken as the content of each component.
The contents of Cr, Ta, Nb, Ti, and Zr were calculated by converting them into their respective carbides. Tables 3 and 6 show the average contents of each.

Next, with respect to the cross section of the WC-based superhard alloy of the tools 1 to 10 of the present invention and the tools 1 to 10 of the comparative example, using a scanning electron microscope (SEM), for example, the WC-based superhard alloy at a magnification of 200 to 500 times. An SEM image was acquired with an image size of 120 × 96 mm and a Magnification of 1280 × 1024 Magnifier, and the area of each coupled phase in one observation field was determined by image processing with the image analysis software ImageJ. Measure and accumulate the area of each particle of the bonding phase from the particle with the smallest area, and the area occupied by one bonding phase particle when the cumulative area exceeds 10% of the total area of the bonding phase is A10, and the cumulative area is bonded. The area occupied by one bonded phase particle when it exceeds 90% of the total area of the phase is determined as A90.
Next, A90 / A10 is obtained by dividing the obtained A90 by A10.
The number of bonded phases is measured by measuring each of the individual bonded phases divided by the WC particles as one bonded phase.
Further, in order to include a sufficient number of coupled phases in the image, observation is performed at a magnification of 200 to 500 times, and the observation magnification is adjusted so that the number of coupled phases measured after image processing falls within the range of 5000 to 15000. Selected.

The following wet continuous cutting test was performed on the tools 1 to 10 of the present invention and the tools 1 to 10 of the comparative examples in a state where they were screwed to the tip of the tool steel cutting tool with a fixing jig.
Work material: JIS / SUS304 (HB170) round bar,
Cutting speed: 100 m / min,
Notch: 2.0 mm,
Feed: 0.6mm / rev,
Cutting time: 4 minutes,
Uses wet water-soluble cutting oil.
After the wet continuous cutting test, the flank plastic deformation amount of the cutting edge was measured, and the worn state of the cutting edge was observed. The amount of plastic deformation of the flank surface of the cutting edge is determined by drawing a line segment on the flank surface on the main cutting edge side of the tool at a position sufficiently distant from the cutting edge on the ridge line where the flank surface on the main cutting edge side and the rake face intersect. The same line segment is stretched in the direction of the cutting edge, and the part where the distance between the stretched line segment and the ridgeline of the cutting edge (vertical direction of the stretched line segment) is the longest is measured, and the flank plastic deformation of the cutting edge is measured. The amount was taken. Further, when the flank plastic deformation amount was 0.04 mm or more, the worn state was defined as the cutting edge deformation.
Table 7 shows the test results.

Further, a hard coating layer having an average layer thickness shown in Table 8 is coated on the cutting tool surfaces of the tools 1 to 4 of the present invention and tools 1 to 4 of the comparative example by the PVD method or the CVD method, and the surface coating WC group of the present invention is formed. Cemented Carbide Cutting Tools (hereinafter referred to as "Coating Tools of the Present Invention") 1 to 4 and Comparative Example Surface Coated WC-based Cemented Carbide Cutting Tools (hereinafter referred to as "Comparative Example Covering Tools") 1 to 4 were produced. ..
The wet continuous cutting test shown below was carried out for each of the above-mentioned covering tools, the amount of plastic deformation of the flank of the cutting edge was measured, and the state of wear of the cutting edge was observed.
Cutting conditions:
Work material: JIS / SUS304 (HB170) round bar,
Cutting speed: 190m / min,
Notch: 2.0 mm,
Feed: 0.5 mm / rev,
Cutting time: 4 minutes,
Uses wet water-soluble cutting oil.
Table 9 shows the results of the cutting test.

According to the test results shown in Tables 7 and 9, the tools of the present invention and the coated tools of the present invention exhibit excellent plastic deformation resistance without causing defects, whereas the comparative tool and the comparative tool and the tool of the present invention have excellent plastic deformation resistance. Comparative example It can be seen that the coated tool has a short life due to the occurrence of defects or plastic deformation.

As described above, the tool of the present invention and the covering tool of the present invention exhibit excellent plastic deformation resistance and fracture resistance when subjected to intermittent cutting of alloy steel, etc., and are applicable to other work materials and cutting conditions. Even in such a case, it is expected that excellent cutting performance will be exhibited over a long period of use and the life of the tool will be extended.

Claims (3)

In a cutting tool made of WC-based cemented carbide based on WC-based cemented carbide,
The composition of WC-based cemented carbide, a 6.0 to 14.0 wt% of Co and _Cr 3 _{C 2} as the binder phase forming component containing 0.1 to 1.4 wt%, the balance being WC and Consists of unavoidable impurities
The particle size distribution of the bonded phase was analyzed for the cross section of the WC-based cemented carbide, and the area occupied by one bonded phase particle when the cumulative 10% particle area was occupied by A10 and one bonded phase particle when the cumulative 90% particle area was occupied. ^{Made of WC-based cemented carbide, characterized in that A10 is 0.15 μm 2} or more and less than 0.25 μm ² and A90 / A10 is 8.0 or more and less than 11.0 when the area is A90. Cutting tools. The WC according to claim 1, wherein the WC-based cemented carbide further contains at least one selected from TaC, NbC, TiC and ZrC in a total amount of 4.0% by mass or less. Cutting tool made of basic cemented carbide. A surface-coated WC-based cemented carbide cutting tool, characterized in that a hard coating layer is formed on at least the cutting edge of the WC-based cemented carbide cutting tool according to claim 1 or 2.