JP2020110891A - Cutting tool made of wc-group cemented carbide alloy excellent in anti-plastic deformation and anti-chipping and cutting tool made of surface-coating wc-group cemented carbide - Google Patents

Abstract

To provide a WC-group cemented carbide tool which can exert excellent anti-plastic deformation and anti-chipping, in cutting difficult-to-cut materials such as stainless steel, and a surface-coating WC-group cemented carbide tool.SOLUTION: In a WC-group cemented carbide tool, excellent in anti-plastic deformation and anti-chipping, basically made of WC-group cemented carbide alloy, a composition of components of the WC-group cemented carbide alloy contains Co:6-14 mass% and Cr3C2:0.1-1.4 mass% and the other part of the tool is made of WC and inevitable impurities, or further contains at least one kind selected from TaC, NbC, TiC and ZrC: 4 mass% or less in all, where when the area of particles in number integration 10% particle size of bonded-phase particles measured with respect to a cross section of the WC-group cemented carbide alloy is defined as A10, average roundness of fine bonded-phase particles having areas smaller than the A10 is in a range of 0.9-1.0, and a surface-coating WC-group cemented carbide 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”) that has excellent plastic deformation resistance and excellent chipping resistance in cutting difficult-to-cut materials such as stainless steel. And a surface-coated WC-based cemented carbide cutting tool.

Since the WC-based cemented carbide has high hardness and toughness, the WC-based cemented carbide tool based on this has excellent wear resistance and has a long life over long-term use. Known as a cutting tool.
However, in recent years, various proposals have been made in order to further improve the cutting performance and tool life of WC-based cemented carbide tools depending on 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 the cemented carbide) as main components. In a cemented carbide having a binder phase for forming a cemented carbide, the number of particles of tungsten carbide is A, and the number of particles of tungsten carbide having a contact point with another tungsten carbide particle of 1 point or less is B/A. By satisfying ≦0.05, the plastic deformation resistance of the cemented carbide is improved, and as a result, the longevity of the WC-based cemented carbide tool is extended in the 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 the total amount of TaC and NbC is 0.2 to 0.5% by mass. In a WC-based cemented carbide tool, the balance of which is WC, the balance is WC, and the hardness is 88.6HRA to 89.5HRA, in the area ratio on the polished surface, the WC cumulative particle size 80% diameter D80 and the cumulative particle size 20. The ratio D80/D20 of the% diameter D20 is in the range of 2.0≦D80/D20≦4.0, the D80 is in the range of 4.0 to 7.0 μm, and the WC adhesion c is 0.36≦c. By setting ≦0.43, it has been proposed to prevent adhesion of a work material and improve fracture resistance in cutting of a difficult-to-cut material represented by stainless steel.

In Patent Document 3, in WC group carbide tool, when the composition of WC-based cemented carbide, expressed in WC-x wt% Co-y _wt% Cr _{3 C} 2 -z wt% VC, 6 ≦ x ≦ 14, 0.4≦y≦0.8, 0≦z≦0.6, (y+z)≦0.1x are satisfied, and the WC adhesion C of the WC-based cemented carbide is C=1-V. When expressed by _b ^α ·exp (0.391·L), the value V _{b of the} volume fraction of the binder phase of the WC-based cemented carbide in this formula is 0.11≦V _b ≦0.25, and (WC particles Value of (standard deviation of particle size distribution)/(average WC particle size) is within the range of 0.3≦L≦0.7, and the coefficient α is 0.3≦α≦0.55. By using a WC-based cemented carbide having a satisfactory WC adhesion C, a WC-based cement with improved fracture resistance and improved toughness in cutting processing of Al alloy, carbon steel, etc. without decreasing hardness and rigidity. Carbide tools have been proposed.

In Patent Document 4, in the WC-based cemented carbide tool, when the WC-WC adhesive interface length is L1 and the WC-Co adhesive interface length is L2,
R>(0.82-0.086×D)×(10/V)
It has been proposed that by satisfying the formula (1), the heat-resistant plastic deformability and toughness of the WC-based cemented carbide tool are improved in the cutting of the Ni-based heat-resistant alloy.
Note that R=(L1)/((L1)+(L2))
D: WC area average particle size (μm), which is in the range of 0.6≦D≦1.7.
Here, the D means the particle size of WC when the area ratio of WC is 50%.
V: Binder phase volume (vol %), which is in the range of 9≦V≦14.

In Patent Document 5, in weight %, Cr or/and Cr compound: 0 to 4% (in terms of Cr), V or/and V compound: 0 to 4% (in terms of V), TaC: 0 to 2%, TiC: 0-2%,
N or/and N compound: 0 to 1% (in terms of N), Co: 0.1 to 10%, WC and unavoidable impurities: a composition consisting of the balance, and a Co average of 0.06 to 30 nanometers It has a thickness (CFP), and during sintering, a part of the temperature range of 900° C. to 1600° C. during the temperature rise or the entire range is loaded with a pressure of 3 atm to 200 atm using a gas as a pressure medium to increase the temperature. A WC-Co-based cemented carbide part for cutting tools with a higher density has been proposed. This WC-Co-based cemented carbide part, desirably, the average particle size of WC is 1 μm or less, and the CFP is 0.06 to 30 nm. It is said that the toughness of ultrafine-grained low-Co cemented carbide parts in the range of can be enhanced.
However, CFP is Co average thickness (nm),
CFP=0.58*A/(100-A)*R
And A:Co(%), 2R:WC average particle size (nm).

Japanese Patent No. 6256415 JP, 2017-88999, A JP, 2017-148895, A JP, 2017-179433, A JP-A-7-305136

According to the conventional WC-based cemented carbide tools proposed in Patent Documents 1 to 5, by controlling the number of contact points between WC-WC particles, the particle size of WC, the degree of WC adhesion, the production conditions, etc. We are working to improve the cutting performance and tool characteristics of carbide tools.
However, in the conventional tool, when cutting a difficult-to-cut material such as stainless steel, due to occurrence of grain boundary slip at the interface of WC-WC particles, or occurrence of cracks due to stress concentration in the binder phase. The occurrence of abnormal damage such as chipping could not be sufficiently suppressed, and therefore the tool life was short.

In order to provide a WC-based cemented carbide tool that exhibits excellent plastic deformation resistance and chipping resistance in the cutting of difficult-to-cut materials such as stainless steel, the present inventors have found that the binder phase of WC-based cemented carbide is used. As a result of intensive research focusing on the morphology, the following findings were obtained.

In the WC-based cemented carbide tools shown in Patent Documents 1 to 4, improvements focused mainly on WC particles are made, and in the WC-based cemented carbide tool shown in Patent Document 5, mainly focused on CFP. However, the inventors of the present invention have conducted a study focusing on the morphology of the binder phase while changing the viewpoint from the conventional technique. When the roundness of the binder phase particles is set within the range of 0.9 to 1.0, the fine binder phase particles in the WC-based cemented carbide are not elongated but have a shape close to a circle. Therefore, by increasing the contact length between WC-WC particles, the occurrence of grain boundary slip at the interface of WC-WC particles is reduced, plastic deformation resistance is improved, and the cutting edge of the cutting edge is improved. It has been found that the occurrence of deformation is suppressed.
In addition, since the fine binder phase particles in the WC-based cemented carbide have a shape close to a circle, the stress concentration due to the high load acting during cutting is suppressed and the formation of voids is also suppressed, so that the deformation, It was found that the starting point of fracture is reduced and the occurrence of abnormal damage such as chipping and chipping is suppressed.
That is, for the fine binder phase particles of the binder phase of the WC-based cemented carbide, a WC-based cemented carbide tool whose roundness is set within the range of 0.9 to 1.0 is used for difficult-to-cut materials such as stainless steel. When the material is used for cutting, the deformation of the cutting edge is suppressed by the improvement of plastic deformation resistance, and the occurrence of deformation and fracture is reduced, which suppresses the occurrence of abnormal damage such as chipping and chipping. It was found that the tool life can be extended.

The present invention was made based on the above findings,
“(1) In a WC-based cemented carbide cutting tool based on WC-based cemented carbide,
The composition of the WC-based cemented carbide contains 6 to 14% by mass of Co and 0.1 to 1.4% by mass of Cr ₃ C ₂ as a binder phase forming component, and the balance consists of WC and unavoidable impurities. The average circularity of the fine binder phase particles having an area of A10 or less is 0.9 to, where A10 is the particle area of 10% particle size integration of the binder phase particles measured on the cross section of the WC-based cemented carbide. A WC-based cemented carbide cutting tool characterized by being in the range of 1.0.
(2) The WC-based cemented carbide further contains at least one selected from TaC, NbC, TiC and ZrC in a total amount of 4% by mass or less, and (1) is characterized in that Cutting tool made of WC-based cemented carbide.
(3) 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 (1) or (2). tool. "
It is characterized by.
The contents of Cr ₃ C ₂ , TaC, NbC, TiC and ZrC in the above (1) and (2) are the Cr amount, Ta amount, Nb amount and Ti amount measured on the cross section of the WC-based cemented carbide, The values of Zr are all converted into carbides.

The WC-based cemented carbide tool and the surface-coated WC-based cemented carbide cutting tool of the present invention include Co, Cr ₃ C ₂ , or TaC, NbC, or TiC, which are the components of the WC-based cemented carbide constituting the substrate. , ZrC has a specific composition range, and the average particle size of fine binder phase particles having an area of A10 or less, where A10 is the particle area at 10% particle size integration of binder phase particles in WC-based cemented carbide. Since the circularity is in the range of 0.9 to 1.0, there are few elongated fine binder phase particles in the WC-based cemented carbide, and most of them have a fine circular binder shape. Since the contact interface between WC-WC particles is long because they are particles, in the cutting of difficult-to-cut materials such as stainless steel, even when a high load is applied during cutting, grain boundary slip between WC particles Is suppressed, the plastic deformation resistance is improved, the deformation of the cutting edge is suppressed, and the life of the cutting tool is extended.
Further, since the stress concentration on the fine binder phase particles is relieved, the occurrence of breakage starting from the binder phase is reduced, and the occurrence of abnormal damage such as chipping is suppressed.

The measurement schematic of the flank plastic deformation amount of a cutting edge is shown. The upper diagram (rake face) is a plan view, and the lower diagram (flank face) is a side view. The amount of plastic deformation of the flank of the cutting edge is measured after cutting, with reference to the undeformed cutting edge ridgeline before cutting, and the amount by which the cutting edge ridgeline is pressed and deformed by cutting. A specific measurement method is to draw a line segment on the main cutting edge side flank of the tool on a ridgeline where the main cutting edge side flank and the rake face intersect at a position sufficiently distant from the cutting edge, and cut the same line segment. Extend in the blade direction, measure the part where the distance between the extended line segment and the ridgeline of the cutting edge (vertical direction of the extended line segment) is the longest, and calculate this as the flank plastic deformation amount of the cutting edge. ..

Hereinafter, the present invention will be described in detail.

Co:
Co is contained as a main binder phase forming component of the WC-based cemented carbide, but if the Co content is less than 6 mass %, sufficient toughness cannot be maintained, while the Co content exceeds 14 mass %. And the desired hardness required as a cutting tool is not obtained, and the deformation and wear progress become remarkable, so that the Co content in the WC-based cemented carbide is set to 6 to 14% by mass. Specified.

Cr ₃ C ₂ :
Cr ₃ C ₂ is a WC-based cemented carbide, in which Cr is solid-dissolved in Co that forms the main binder phase, suppresses the growth of the WC phase that forms the hard phase, and reduces the grain size of the WC phase. To improve the toughness. However, this action is insufficient if the Cr ₃ C ₂ content is less than 0.1% by mass. On the other hand, if the content exceeds 10% with respect to the Co content, the compound carbide of Cr and W is formed. To reduce the toughness and become a starting point of occurrence of defects.
In the present invention, since the upper limit of Co content is 14% by mass, the upper limit of Cr ₃ C ₂ is 1.4% by mass, which is 10% of the upper limit of Co content.
Therefore, _Cr 3 _{C 2} content of WC-based cemented carbide is specified to 0.1 to 1.4 mass%.

TaC, NbC, TiC, ZrC:
The WC-based cemented carbide of the present invention can further contain, as a component thereof, at least one selected from TaC, NbC, TiC and ZrC in a total amount of 4% by mass or less.
Ta, Nb, Ti, and Zr all have the effect of increasing the hardness by forming a solid solution in Co that forms the main binder phase, but if the total content in terms of carbides exceeds 4% by mass, carbides The precipitation lowers the toughness and becomes the starting point of 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 thereof is preferably 4% by mass or less.
The contents of Cr ₃ C ₂ , TaC, NbC, TiC, and ZrC described above are all the amounts of carbide, Cr amount, Ta amount, Nb amount, Ti amount, and Zr amount measured by EPMA for WC-based cemented carbide. It is a converted value.

Circularity of fine binder phase particles:
The average circularity of the fine binder phase particles of the WC-based cemented carbide referred to in the present invention means the individual fine binder phases specified by observation using a scanning electron microscope (SEM) with respect to the cross section of the WC-based cemented carbide. The circularity of the particles is calculated and the averaged circularity is used.
Here, the fine binder phase particles are, for example, using a scanning electron microscope (SEM), observing a cross section of the WC-based cemented carbide at a magnification of 3000 to 4000 times, and a binder phase (containing Co as a main component). Phase) to obtain a SEM image that can be clearly separated from the contrast of the other phase, image processing of this to determine the area and number of individual binder phase particles, the area of the binder phase particles as the horizontal axis, Also, when the number of binder phase particles is taken as the vertical axis and a cumulative distribution is created by stacking particles with a small binder phase area, and the particle area at 10% of the total number of particles is A10, a bond having an area of A10 or less is obtained. The phase particles are called finely bonded phase particles.
Then, regarding the circularity of the fine binder phase particles, for example, using a scanning electron microscope (SEM), a cross section of the WC-based cemented carbide is observed at a magnification of 3000 to 4000 times to obtain an SEM image. The roundness of each fine binder phase particle can be obtained by identifying and extracting the fine binder phase particle in the SEM image and measuring it using the image analysis software ImageJ.

More specifically, it is as follows.
When n fine binder phase particles are specified in one observation visual field of the cross section of the WC-based cemented carbide, the fine binder phase particles are given numbers 1 to n, and fine binder phase particles 1 to n are given. When the area of each is A _{1 to} A _n, and the circumferential length of the fine binder phase particles of numbers _{1 to n} is L _{1 to} L _n , the roundness C _m of the fine binder phase particles of number _m is
C _m =4π×A _m /L _m ²
Is defined by
Then, a value of _C 1 -C _n as m = 1 to n, further, an average value _{C 1 to n} of _C 1 -C _n, fine binding the _{C 1 to n} is in the one observation field It is the roundness of the phase particles.
Then, in a plurality of observation visual fields (for example, 10 observation visual fields), the circularity of the fine binder phase particles in each observation visual field is obtained, and the averaged value is used as the WC-based cemented carbide of the present invention. The average roundness of the fine binder phase particles in the cross section.
As is clear from the definition of roundness, the closer the value of roundness or average roundness is to 1, the closer the shape of the fine binder phase particles of the WC-based cemented carbide is to a roundness. Since the shape of the fine binder phase particles becomes an elongated shape instead of a circle as the value approaches 0, the value of the roundness or the average roundness of the fine binder phase particles in the WC-based cemented carbide is It can be said to be an index.

In the present invention, the average circularity of the fine binder phase particles is set within the range of 0.9 to 1.0, but this is for the following reason.
When the average roundness of the fine binder phase particles in the WC-based cemented carbide is less than 0.9, the contact interface length between the WC-WC particles is shortened due to the increase in the number of elongated fine binder phase particles, Stress concentration is likely to occur at the tip of the elongated fine binder phase particles, voids are likely to occur at the tip of the fine binder phase particles, and grain boundary slip between WC-WC particles is likely to occur, resulting in insufficient plastic deformation resistance. Disappear. Furthermore, the voids formed at the tip of the fine binder phase particles serve as the starting points for deformation and breakage of the WC-based cemented carbide tool, so that the toughness, chipping resistance, fracture resistance, etc. are reduced.
When the average circularity of the fine binder phase particles is 1.0 (or a value close to 1.0), it means that the shape of the fine binder phase particles is circular or almost circular, and the contact interface between the WC-WC particles. As a result, the plastic deformation resistance is improved, and the abnormal damage resistance against chipping and chipping is also improved.
Therefore, in the present invention, the average roundness of the fine binder phase particles is within the range of 0.9 to 1.0. By this, in wet continuous cutting of difficult-to-cut materials such as stainless steel, the plastic deformation resistance is improved, so that the deformation of the cutting edge is suppressed and the formation of voids between WC-WC particles is suppressed. By relaxing the stress concentration on the binder phase, it is possible to enhance the abnormal damage resistance such as chipping and chipping, and prolong the life of the cutting tool.

The WC-based cemented carbide tool of the present invention can be produced, for example, by the following steps.
First, a raw powder consisting of coarse WC powder, fine WC powder, Co powder, Cr ₃ C ₂ powder, or, if necessary, one or more of TaC powder, NbC powder, TiC powder, and ZrC powder. The raw material powder containing the above powder is mixed and mixed so as to have a predetermined composition to prepare a mixed powder.
Then, the mixed powder is molded to prepare a powder compact, and the powder compact is heated at a temperature of 1000° C. or higher and 1100° C. or lower for an isothermal holding time of 30 to 300 minutes and a heating atmosphere of argon. A solid phase rearrangement step of maintaining isothermal conditions under gas atmosphere and atmospheric pressure: 0.5 to 0.7 MPa is performed, and then heating temperature: 1300° C. to 1500° C. and heating holding time: 30 to 120 minutes, Sintering is performed in a vacuum atmosphere to produce a WC-based cemented carbide.
The isothermal holding temperature in the solid phase rearrangement step is 100° C. or more lower than the liquid phase formation temperature of the binder phase, and the plastic flow of the binder phase is not active. By accelerating the solid-phase contraction by the gas pressure in this temperature range, rearrangement of the WC particles becomes remarkable, and after the isothermal holding step, the average roundness of the WC particles is mainly Co near 0.9 to 1.0. Binder particles as a component remain.
Next, the WC-based cemented carbide can be machined and ground to produce a WC-based cemented carbide tool of a desired size and shape.

In the WC-based cemented carbide tool produced in the above step, the average circularity of the fine binder phase particles of the WC-based cemented carbide is in the range of 0.9 to 1.0, and the WC-based cemented carbide has a substantially circular shape rather than an elongated shape. As the fine binder phase particles are formed close to each other, the contact interface length of the WC-WC particles becomes long.
As a result, since the grain boundary slip at the WC-WC grain interface is suppressed, the plastic deformation resistance is improved, and the stress concentration on the binder phase is relieved. The fracture starting from the void formed between the binder phase and the WC particles is reduced, and the toughness is improved.
Further, at least the cutting edge of the WC-based cemented carbide cutting tool is coated with a hard coating such as a Ti-Al-based or Al-Cr-based carbide, nitride, carbonitride, or Al ₂ O ₃ by PVD or CVD. By forming a coating by a film forming method such as the above, a surface-coated WC-based cemented carbide cutting tool can be produced.
In the production of the surface-coated WC-based cemented carbide cutting tool, the type of hard coating and film forming method may be the film type and film forming method that are well known to those skilled in the art. 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.

(A) First, as a powder for sintering, a coarse WC powder having an average particle size (d50) of 4.0 to 8.0 μm shown in Table 1, and an average particle size (d50) of 0.5 to 0 shown in Table 1 are used. 2.0 μm fine WC powder, Co powder, Cr ₃ C ₂ powder, TaC powder, NbC powder, TiC powder, and ZrC powder are prepared.
These powders were blended so as to have the blending composition shown in Table 1 to prepare a sintering powder.
Table 1 shows the composition of each powder (mass %).
The average particle diameter (d50) of Co powder, Cr ₃ C ₂ powder, TaC powder, NbC powder, TiC powder, and ZrC powder is in the range of 1.0 to 3.0 μm.

(B) Sintering powders blended with the blending composition shown in Table 1 were wet mixed in a ball mill for 72 hours, dried, and then press-molded at a pressure of 100 MPa to produce a powder compact.

(C) Then, these powder compacts are heated to the holding temperature range of 1000 to 1100° C. under the conditions shown in Table 2, that is, in an argon atmosphere of 0.5 to 0.7 MPa (this temperature range is The solid phase reaction occurs, but it is lower than the liquid phase formation temperature of the binding phase), and the solid phase rearrangement step was performed under the condition of holding at the holding temperature for 30 to 300 minutes.

(D) Next, the inside of the furnace was set to a vacuum atmosphere of 10 ⁻¹ Pa or less, and the conditions shown in Table 3, that is, heating temperature: 1300° C. or more and 1500° C. or less, and heating holding time: 30 to 120 minutes, 10 ⁻¹ Sintering was performed under a vacuum atmosphere of Pa or less to produce a WC-based cemented carbide.

(E) Then, the WC-based cemented carbide is machined and ground, and the WC-based cemented carbide tools 1 to 12 shown in Table 4 of the insert shape of CNMG120408-GM (hereinafter referred to as Tools 1 to 12 of the present invention). Was produced.

For comparison, WC-based cemented carbide tools 1 to 9 of Comparative Examples (hereinafter, referred to as Comparative Example tools 1 to 9) were manufactured.
The manufacturing procedure is one in which the step (c) is omitted in the manufacturing process of the tools 1 to 12 of the present invention, or the step (c) is performed under an inappropriate condition.
That is, the sintering powder blended in the blending composition shown in Table 1 was wet mixed in a ball mill for 72 hours, dried, and then press-molded at a pressure of 100 MPa to produce a powder compact, and the conditions shown in Table 3 were used. That is, heating temperature: 1300° C. or more and 1500° C. or less, and heating holding time: 30 to 120 minutes, sintering is performed under the conditions of a vacuum atmosphere to produce a WC-based cemented carbide, which is machined and ground. Then, comparative example tools 1 to 9 shown in Table 5 of the insert shape of CNMG120408-GM were manufactured.
Regarding the comparative tool 9, the solid-phase rearrangement step was performed under the conditions shown in Table 2 and then the sintering was performed under the conditions shown in Table 3 to produce a WC-based cemented carbide.

For the cross sections of the WC-based cemented carbides of the present tools 1 to 12 and comparative tools 1 to 9, EPMA was used to measure the contents of the components Co, Cr, Ta, Nb, Ti, and Zr at 10 points, The average value was used as the content of each component.
In addition, Cr, Ta, Nb, Ti, and Zr were converted into their respective carbides to calculate their contents.
Tables 4 and 5 show the respective average contents.

Next, regarding the cross sections of the WC-based cemented carbides of the present invention tools 1 to 12 and comparative example tools 1 to 9, using a scanning electron microscope (SEM), cross sections of the WC-based cemented carbide at a magnification of 3000 to 4000 times. By observing, the SEM image was acquired with an image size of 120×96 mm and the number of pixels was 1280×1024 pixels, the image was processed, and the area and the number of individual bonded phase particles in one observation visual field were obtained. The horizontal axis represents the area of B, and the vertical axis represents the number of binder phase particles, and a cumulative distribution of binder phase particles is created. The particle area at 10% of the number integration is A10, and the fine binder phase particles have an area of A10 or less. For, the roundness of each fine binder phase particle was measured using image analysis software ImageJ, and the average value of the roundness of each fine binder phase particle in the one observation visual field was determined.
Incidentally, from the observation magnification and the pixel number of relationships, minimal binding phase area is 3000 times observation is 977 nm ^2, which is 549 nm ² in 4000 times observed. The observation visual field magnification was selected so that 150 to 400 binder phase particles were included in the visual field. In the present invention, each binder phase divided by the WC particles is regarded as one crystal grain.
Then, the average circularity of the fine bonding phase particles in the cross section of the WC-based cemented carbide was calculated by further averaging the average values of the circularity obtained in the 10 observation fields.
Tables 4 and 5 show the values of A10 and the average roundness.

The following wet continuous cutting test was performed on the above-mentioned tools 1 to 12 of the present invention and tools 1 to 9 of the comparative examples, in a state where they were screwed to the tip end of a tool steel bite with a fixing jig.
Work Material: JIS/SUS304 (HB170) round bar,
Cutting speed: 110m/min,
Notch: 2.0 mm,
Feed: 0.5 mm/rev,
Cutting time: 4 minutes,
Wet water-soluble cutting oil is used.
After the wet continuous cutting test, the flank plastic deformation amount of the cutting edge was measured, and the wear state of the cutting edge was observed. Incidentally, the flank plastic deformation amount of the cutting edge, for the main cutting edge side flank of the tool, draw a line segment on the ridge line where the main cutting edge side flank and the rake face intersect at a position sufficiently distant from the cutting edge, 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 farthest is measured, and the flank plastic deformation of the cutting edge is measured. And quantity. Further, when the flank face plastic deformation amount was 0.04 mm or more, the wear state was defined as the blade edge deformation.
FIG. 1 shows a schematic diagram of measurement of flank plastic deformation amount.
Table 6 shows the measurement results.

Further, a hard coating layer having an average layer thickness shown in Table 7 is formed on the cutting edge surfaces of the present invention tools 1 to 4 and comparative example tools 1 to 4 by PVD method or CVD method, and the present invention surface coated WC group Cemented carbide cutting tools (hereinafter referred to as "the present invention coated tool") 1 to 4 and comparative example surface-coated WC-based cemented carbide cutting tools (hereinafter referred to as "comparative example coated tool") 1 to 4 were produced. ..
The wet continuous cutting test shown below was performed on each of the above coated tools to measure the amount of plastic deformation of the flank of the cutting edge and observe the wear state of the cutting edge.
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,
Wet water-soluble cutting oil is used.
Table 8 shows the results of the cutting test.

The test results shown in Tables 6 and 8 show that the tool of the present invention and the coated tool of the present invention exhibit excellent plastic deformation resistance without causing severe chipping which affects the life. ..
On the other hand, in the comparative tool and the comparative coated tool, the plastic deformation of the tool is great in a predetermined cutting time, and it is difficult to satisfy the predetermined work material size.

As described above, the tool of the present invention and the coated tool of the present invention have excellent plastic deformation resistance and excellent chipping resistance when subjected to cutting of a difficult-to-cut material such as stainless steel, but other work materials. Even when applied to materials and cutting conditions, it is expected that excellent cutting performance will be exhibited over long-term use and that the tool life will be extended.

Claims (3)

In a cutting tool made of WC-based cemented carbide based on WC-based cemented carbide,
The composition of the WC-based cemented carbide contains 6 to 14% by mass of Co and 0.1 to 1.4% by mass of Cr ₃ C ₂ as a binder phase forming component, and the balance consists of WC and unavoidable impurities. Assuming that the particle area of the binder phase particles measured on the cross section of the WC-based cemented carbide in the 10% particle size integration is A10, the average roundness of the fine binder phase particles having an area of A10 or less is 0.9 to A WC-based cemented carbide cutting tool characterized by being in the range of 1.0. The WC-based cemented carbide further contains at least one selected from TaC, NbC, TiC and ZrC in a total amount of 4% by mass or less, and the WC-based cemented carbide according to claim 1. Hard alloy cutting tool. A surface-coated WC-based cemented carbide cutting tool, wherein a hard coating layer is formed on at least the cutting edge of the WC-based cemented carbide cutting tool according to claim 1.

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