JP2013237120A - Wc-based cemented carbide cutting tool excellent in chipping resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a WC-based cemented carbide cutting tool that has a sufficient cutting life and is excellent in chipping resistance and finished surface accuracy in high-speed intermittent cutting.SOLUTION: A cutting tool is made of a WC-based cemented carbide mainly consisting of WC and composed of a hard dispersed phase containing one or more of a carbide, a nitride, and a carbonitride of Ti, Ta, Mo, Nb, V, and Cr, and a binder metal phase comprising one or more of Co, Ni, Fe, and Al. The cutting tool is configured as follows: (a) the Hv of a flank face and a rake face is 1,600-1,800 while the Hv of a honing part is 1,900-2,200, (b) the surface roughness Ra of the flank face and the rake face is 0.15-0.30 μm while the surface roughness Ra of the honing part is 0.05-0.20 μm, and the surface roughness Ra of the flank face and the rake face is larger than the surface roughness Ra of the honing part, (c) the average particle size of WC particles in the WC cemented carbide is 0.5-3.0 μm and the content of the binder metal phase is 4-12 mass%.

Description

  The present invention relates to a cutting tool made of a WC-based cemented carbide, and more specifically, has excellent fracture resistance, and even when used for intermittent cutting of high-hardness steel such as alloy steel and bearing steel. The present invention relates to a cutting tool made of a WC-based cemented carbide that exhibits excellent wear resistance.

  In general, for cutting tools, inserts that are detachably attached to the tip of a tool for turning and planing of various materials such as steel and cast iron, chamfering, grooving, and shoulder processing There are known solid type end mills used for such as, and insert type end mills in which inserts are detachably attached and cut in the same manner as solid type end mills.

  And as a tool base of a cutting tool, WC is the main component from the past, and further, one or two types of carbides, nitrides, and carbonitrides of Ti, Ta, Mo, Nb, V, and Cr as required. It is known to use a WC-based cemented carbide composed of a hard dispersed phase containing the above and a bonded metal phase composed of one or more of Co, Ni, Fe and Al. It is also known that a cutting tool using a base cemented carbide is used for rough finishing cutting of steel or cast iron (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 5-230589

  In recent years, automation of cutting machines has been remarkable. On the other hand, there has been a strong demand for labor saving and energy saving and further cost reduction for cutting. Accordingly, cutting is performed under higher speed conditions in addition to normal cutting conditions. However, in the conventional cutting tool, no particular problem occurs when various types of steel and cast iron are cut under normal conditions. However, when this is used for high-speed intermittent cutting (hereinafter simply referred to as “high-speed cutting”) of high-hardness steel having a hardness higher than 50 Vickers hardness (C scale) such as hardened material of alloy steel and bearing steel However, when the toughness is improved, the hardness tends to decrease accordingly. In particular, since the cutting resistance is large in the vicinity of the honing portion, if the hardness decreases, the wear easily proceeds, the cutting edge is damaged, and the finished surface system is not stable. That is, since the fracture resistance of the WC-based cemented carbide is not sufficient, there is a problem that the cutting edge is chipped and the cutting life and finished surface accuracy are lowered.

  Therefore, the technical problem to be solved by the present invention, that is, the object of the present invention is to provide a WC-based cemented carbide excellent in chipping resistance and finished surface accuracy that has a sufficient cutting life even in high-speed cutting of high hardness steel. It is to provide a cutting tool.

From the above viewpoint, the present inventor has developed a cutting tool that exhibits excellent fracture resistance of WC-based cemented carbide, particularly in high-speed cutting of hardened steel such as alloy steel and hardened material of bearing steel. As a result of research,
(A) The cutting tool flank, rake face, honing hardness, and surface roughness Ra are adjusted to predetermined values.
(B) The particle size of the WC particles constituting the WC-based cemented carbide is adjusted to a predetermined value.
(C) The content of the metal binder phase in the WC-based cemented carbide is adjusted.
It has been found that when the conditions (a) to (c) are satisfied, the WC-based cemented carbide exhibits excellent fracture resistance.

  Furthermore, the present inventor has found that the condition (a) can be achieved by subjecting the cutting edge of a WC-based cemented carbide alloy to Ar bombardment treatment under predetermined conditions.

The present invention has been completed based on the above research results,
“A hard dispersed phase mainly composed of WC and containing one or more of carbides, nitrides, and carbonitrides of Ti, Ta, Mo, Nb, V, and Cr, and Co, Ni, Fe, and Al. A WC-based cemented carbide cutting tool having a tool base made of a WC-based cemented carbide composed of one or more metal binder phases,
(A) The flank of the WC-base cemented carbide cutting tool, the Vickers hardness (Hv) of the rake face is 1600 to 1800, the Vickers hardness (Hv) of the honing part is 1900 to 2200, and
(B) The surface roughness Ra of the flank and rake face of the WC-based cemented carbide cutting tool is 0.15 to 0.30 μm, the surface roughness Ra of the honing part is 0.05 to 0.20 μm, and Surface roughness Ra of flank and rake face> Surface roughness Ra of honing portion, and
(C) WC group characterized in that an average particle diameter of WC particles in the WC cemented carbide is 0.5 to 3.0 μm and a content of a metal binder phase is 4 to 12% by mass. Cemented carbide cutting tool. "
It has the characteristics.
Here, the surface roughness Ra in the present invention means the arithmetic average roughness Ra defined by JIS B0601-2001, that is, the average value of the absolute value deviation from the average line.

  Next, in the WC-based cemented carbide cutting tool of the present invention, the reason why the constituent components of the WC-based cemented carbide, the content of the metal binder phase, and the average particle size of the WC particles are limited will be described.

Components of WC-based cemented carbide:
The WC-based cemented carbide of the present invention has WC as a main component and includes a hard dispersed phase containing one or more of Ti, Ta, Mo, Nb, V, Cr carbide, nitride, carbonitride, It is a sintered body composed of a metal binder phase containing one or more of Co, Ni, Fe and Al.

Content of each component in the hard dispersed phase:
Although the content of each component contained in the hard dispersed phase constituting the WC-based cemented carbide is not particularly limited, it goes without saying that various properties of the WC-based cemented carbide change by changing the content of each component. For example, when Cr is contained, there is an effect of suppressing grain growth of WC particles. In this case, the Cr content is preferably 0.1% by mass or more and 1.0% by mass or less. If it is less than 0.1% by mass, the content is small and the grain growth of WC cannot be sufficiently suppressed. On the other hand, if it exceeds 1.0% by mass, Cr becomes excessive, and a brittle phase such as a carbide of Cr is produced in a large amount in the cemented carbide, and this compound becomes a starting point of fracture, which tends to cause a decrease in strength. .

Content of metal binder phase:
In the composition of the metal bonded phase, the main component is particularly preferably Co. However, a part of Co may be substituted with other iron group elements such as Ni and Fe or Al. However, the content of the metal binder phase is 4% by mass or more and 12% by mass or less. The reason is that if the content of the metal binder phase is less than 4% by mass, the toughness of the entire WC-based cemented carbide decreases even if the content of Cr, Ta, etc. in the hard dispersed phase is an appropriate amount, Fracture resistance is reduced. On the other hand, if the amount exceeds 12% by mass, the amount of the binder phase is too large, so that the hardness is lowered and the desired wear resistance cannot be obtained.

In the WC-based cemented carbide of the present invention, the WC average particle size of the hard phase is specified to be 0.5 μm or more and 3.0 μm or less. The reason for this is that if the thickness is less than 0.5 μm, the heat resistance and plastic deformation resistance of the entire WC-based cemented carbide will decrease. On the other hand, if the thickness exceeds 3.0 μm, the hardness of the entire WC-based cemented carbide decreases and desired wear resistance cannot be obtained, and a decrease in bending strength due to a decrease in strength tends to occur.

The content of each component in the WC-based cemented carbide of the present invention can be determined using a well-known analysis method, for example, an electron beam microanalyzer (EPMA).

Vickers hardness (Hv) of flank and rake face and Vickers hardness (Hv) of honing part:
In the WC-based cemented carbide of the present invention, the Vickers hardness (Hv) of the flank and rake face is 1600 to 1800, and the Vickers hardness (Hv) of the honing portion is 1900 to 2200. The reason for this is that the Vickers hardness (Hv) of the flank and rake face is less than 1600 because the effect of improving the wear resistance of the flank and rake face cannot be obtained. If it exceeds 1800, the wear resistance is improved. Toughness decreases and chipping is likely to occur. Therefore, it was set as 1600-1800.
Also, in the honing portion, if less than 1900, the desired effect of improving wear resistance is not obtained, and this is not preferable. If it exceeds 2200, the wear resistance is improved, but the toughness in the vicinity of the honing portion decreases, and the cutting edge Defects are likely to occur. Therefore, it was set to 1900-2200. Further, by determining the Vickers hardness (Hv) of the flank, rake face, and honing portion in this way, the Vickers hardness (Hv) of the flank and rake face is greater than the Vickers hardness (Hv) of the honing portion. Therefore, the honing part is less likely to be chipped. That is, by setting the flank, rake face, and Vickers hardness (Hv) of the honing part as described above, the impact at the honing part at the time of cutting can be mitigated, and the honing at which cutting resistance is maximized at the time of cutting. Peeling at the part can be suppressed.

Surface roughness Ra of WC-based cemented carbide:
It is not preferable that the surface roughness Ra of the WC-based cemented carbide is less than 0.15 μm on the flank and rake face because it leads to an increase in manufacturing cost. If it exceeds 0.30 μm, the cutting resistance on the coating surface Since it becomes large and chipping is likely to occur, it is set to 0.15 μm or more and 0.30 μm or less. Further, in the honing portion, it is not preferable that the thickness is less than 0.05 μm because it leads to an increase in manufacturing cost. If it exceeds 0.20 μm, the cutting resistance on the surface of the film increases and chipping is likely to occur. It was defined as 0.20 μm or less. Further, by setting the surface roughness Ra of the flank and the rake face> the surface roughness Ra of the honing portion, the wear in the honing portion at the time of cutting can be alleviated, and the honing portion in which the cutting resistance is maximized at the time of cutting. It is possible to suppress wear on the surface.

  The flank and rake face have a Vickers hardness (Hv) of 1600 to 1800, the honing part has a Vickers hardness (Hv) of 1900 to 2200, and the flank and rake face have a surface roughness Ra of 0.15 to 0. In order to set the surface roughness Ra of the honing part to 0.05 to 0.20 μm and the surface roughness Ra of the flank and rake face> the surface roughness Ra of the honing part, for example, a surface treatment method This can be achieved by performing Ar bombardment treatment, which is one of the above.

Here, the Ar bombardment treatment means that positive ions (Ar +) formed in an inert gas (Ar gas in this case) discharge in a reduced pressure are collided with a negatively applied WC-based cemented carbide and are positively charged. A processing method applied to remove impurities and thin oxide film layers on the surface, roughen and activate the surface, and knock out impregnated impurities (moisture, etc.) by sputtering effect by ions (Ar +) That is.

When a relatively weak surface treatment such as Ar bombardment is performed, the flank rake face is not significantly affected, but the honed portion has a large bombardment effect due to the edge effect. Therefore, the compressive stress is selectively increased in the honing portion, and the hardness is improved. On the other hand, the flank and rake face have smaller compressive residual stress than the honing part, and the hardness does not increase much, so relatively high toughness is maintained, and fracture resistance is maintained on the flank and rake face, or Impact generated in the vicinity of the honing portion can be reduced. Further, the honing portion has a smooth flat surface, so that cutting resistance can be reduced, leading to stable cutting over a long period of time and improvement of finished surface accuracy.
Therefore, as described above, the synergistic effect of improved hardness and smoothness controlled for each part of the cutting tool provides excellent wear resistance and finished surface accuracy over a long period of time in high-speed cutting of high-hardness steel. It can be demonstrated.

  Moreover, even if the honing shape of the cutting edge is any shape, for example, round honing or chamfer honing, the above-described effects can be obtained by setting the surface roughness and hardness to predetermined values. .

  The cutting tool made of WC-based cemented carbide according to the present invention has improved the hardness of the honing part of the WC-based cemented carbide selectively and has improved smoothness. In addition to exhibiting excellent wear resistance, it is possible to maintain excellent finished surface accuracy of the work material.

It is a schematic explanatory drawing of the arc ion plating apparatus for performing the Ar bombardment process of this invention, (a) is a top view, (b) is a side view.

  Next, the WC-based cemented carbide cutting tool of the present invention will be specifically described with reference to examples.

Prepare WC powder, Co powder, VC powder, Cr ₃ C ₂ , TiC powder, TaC powder, and NbC powder having an average particle diameter in the range of 0.5 to 3.0 μm as raw material powder, and add wax. These raw material powders were blended in the composition shown in Table 1, wet mixed by a ball mill for 72 hours, dried, press molded into a green compact, and then the green compact was placed in a 1.3 Pa vacuum atmosphere. A cemented carbide material was manufactured by holding at a predetermined temperature within a range of 1380 to 1480 ° C. for 1 hour and sintering, followed by sintering under furnace cooling conditions. Further, the outer periphery of the cutting edge is processed to a predetermined size with a grindstone, the chamfer honing process is performed on the cutting edge with a width of 0.13 mm and an angle of 25 °, and finish polishing is performed to further satisfy ISO standard SNGA120204. WC-based cemented carbide cutting tool bases A to D (hereinafter referred to as tool bases A to D) having an insert shape were formed.

(A) Next, each of the tool bases A to D is subjected to ultrasonic cleaning in acetone and dried, and in a radial direction from the central axis on the rotary table in the arc ion plating apparatus shown in FIG. Attached along the outer periphery at a predetermined distance away,
(B) First, the inside of the apparatus is heated to 500 ° C. with a heater while the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, and then Ar gas is introduced to make an atmosphere of 1 to 2 Pa.
(C) A DC bias voltage of −100 V is applied to the tool base that rotates while rotating on the table, so that the cutting tool surface is irradiated with Ar ions for 30 to 60 sec. After bombarding for 30 sec. Of untreated time.
(D) The process of (c) is repeated 5 to 20 times. The Ar bombardment treatment conditions (b) to (c) used in this example are shown as treatment conditions a to c in Table 2. The cutting tools 1 to 10 of the present invention were manufactured by performing the Ar bombardment process.

(E) Further, for comparison purposes, each of the tool bases A to D is ultrasonically cleaned in acetone and dried, and the center on the rotary table in the arc ion plating apparatus shown in FIG. Attached along the outer circumference at a predetermined distance in the radial direction from the shaft,
(F) First, the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, and the inside of the apparatus is heated to 500 ° C. with a heater, and then Ar gas is introduced to obtain 0.4 to 0.8 Pa or 2 A DC bias voltage of −50 V or −200 V is applied to the tool base that rotates while rotating on the table, and the tool base surface is irradiated with Ar ions for 80 to 200 sec. After bombarding for 30 sec. Of untreated time.
(G) The process of (f) is repeated 5 to 20 times. The Ar bombardment treatment conditions (e) to (f) used in this comparative example are also shown in Table 2 as treatment conditions (d) to (f). Comparative cutting tools 1 to 10 were manufactured by performing the Ar bombardment process.

  Vickers hardness (Hv) and surface roughness Ra were measured for the flank, rake face, and honing part of the obtained cutting tools 1 to 10 and comparative cutting tools 1 to 10 of the present invention.

  Here, the measurement of the Vickers hardness (Hv) was performed by using a Vickers microhardness meter to push into each test surface (center of the rake surface, center of the flank surface, center of the honing portion) of the sample with a measurement load of 500 gf. Measure from the size of. In the present invention, five points were measured within a diameter range of 5 mm from the center of each test surface, and the average value was evaluated.

  The surface roughness Ra was measured using a laser microscope in the range of 10 μm × 10 μm, and 10 points were measured at each measurement point to calculate the average. The cut-off values were λs of 0.25 μm and λc of 0.25 mm.

  These results are shown in Table 3.

Next, the cutting conditions A to 10 of the present invention cutting tools 1 to 10 and the comparative cutting tools 1 to 10 with the various cutting tools screwed to the tip of the tool steel tool with a fixing jig. A high-speed intermittent cutting test was conducted at B.
[Cutting conditions A]
Work material: JIS · SKD11 4 fluted round bar,
Cutting speed: 200 m / min. ,
Cutting depth: 0.20mm,
Feed: 0.15 mm / rev. ,
Cutting time: 4 minutes
Dry high-speed intermittent cutting test of high hardness steel under the conditions of (normal cutting speed is 100 m / min.),
[Cutting conditions B]
Work material: JIS · SKD11 4 fluted round bar,
Cutting speed: 220 m / min. ,
Cutting depth: 0.15mm,
Feed: 0.15 m / rev. ,
Cutting time: 4 minutes
Dry high-speed intermittent cutting test of high hardness steel under normal conditions (normal cutting speed is 100 m / min.)
In each cutting test, the flank wear width (mm) of the cutting edge and the finished surface accuracy (arithmetic mean roughness Ra (μm) according to JIS B0601-2001) of the work material were measured. The measurement results are shown in Table 4.

  From the results shown in Tables 2 to 4, the cutting tools of the present invention all control the flank, rake face, honing surface roughness and Vickers hardness (Hv), so alloy steel, bearing steel Even in high-speed interrupted cutting of hardened steel such as hardened steel, excellent wear resistance can be achieved without causing abnormal boundary damage and chipping, and excellent finished surface accuracy of the work material can be secured. On the other hand, all the comparative cutting tools, unlike the cutting tool of the present invention, the flank, rake face, honing part surface roughness and Vickers hardness (Hv) are not controlled. It is clear that the hardness of the honing part is not sufficient, leading to abnormal boundary damage and chipping at the cutting edge, not only maintaining the finished surface accuracy of the work material but also reaching the service life in a relatively short time. Et It is.

  As described above, the WC-based cemented carbide cutting tool according to the present invention can be used not only for cutting under normal cutting conditions such as various types of steel and cast iron, but particularly for hardened materials of alloy steel and bearing steel. WC-based cemented carbide shows excellent fracture resistance even in high-speed intermittent cutting of high-hardness steel, even with high-speed intermittent cutting in which extremely large intermittent and impact mechanical loads are applied to the cutting edge with high heat generation, Maintains excellent surface finish accuracy of the work material for a long period of time and also exhibits excellent wear resistance, so that the performance of the cutting device is improved, and the labor and energy saving of the cutting work is further reduced, and the cost is lower. It is possible to cope with the conversion sufficiently satisfactorily.

Claims (1)

A hard dispersed phase mainly composed of WC and containing one or more of carbides, nitrides, and carbonitrides of Ti, Ta, Mo, Nb, V, and Cr, and one of Co, Ni, Fe, and Al A WC-based cemented carbide cutting tool having a WC-based cemented carbide composed of a seed or a metal binder phase containing two or more types as a tool base,
(A) The flank of the WC-base cemented carbide cutting tool, the Vickers hardness (Hv) of the rake face is 1600 to 1800, the Vickers hardness (Hv) of the honing part is 1900 to 2200, and
(B) The surface roughness Ra of the flank and rake face of the WC-based cemented carbide cutting tool is 0.15 to 0.30 μm, the surface roughness Ra of the honing part is 0.05 to 0.20 μm, and Surface roughness Ra of flank and rake face> Surface roughness Ra of honing portion, and
(C) WC group characterized in that an average particle diameter of WC particles in the WC cemented carbide is 0.5 to 3.0 μm and a content of a metal binder phase is 4 to 12% by mass. Cemented carbide cutting tool.