JPH04193406A - Polycrystal diamond cutting tool and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To improve edge sharpening property by setting the tipping a front edge in which a predetermined surface roughness of a cutting face is provided, to the flank of which a diamond surface is exposed, and which is laid along a cross line between the cutting face and the flank, in a grinding tool suing polycrystal diamond synthesized by the low pressure gas phase method. CONSTITUTION:A polycrystal diamond 2 is formed on the surface of a substrate 1 having the surface roughness not more than 0.1mum by maximum height indication Rmax by means of the low pressure gas phase method. Next, a polycrystal diamond tool material 3 is formed after utilizing the surface of the polycrystal diamond 2 making contact with the substrate 1 of the polycrystal diamond 2 as a cutting face 6, to be brazed on a tool supporting body 4. And then, the tool material 3 is ground and processed by laser processing under predetermined condition to expose the polycrystal diamond on a flank 7. Finally, the tipping size of the front edge which is laid along the cross line between the cutting face 6 and the flank 7 is set to be not less than 0.5mum and not more than 5mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a polycrystalline diamond cutting tool with excellent edge sharpness that is suitable for finishing nonferrous metals and nonmetals, and a method for manufacturing the same.

[Prior Art] Diamond has high hardness and high thermal conductivity, so it is used as cutting tools and wear-resistant tools. However, single-crystal diamond has the drawback of opening its arms, and in order to suppress this drawback, diamonds were sintered together using ultra-high pressure sintering technology, as described in Japanese Patent Publication No. 52-12126. Diamond sintered bodies have been developed.

Among commercially available diamond sintered bodies, those with fine grains, especially those with a grain size of several tens of micrometers or less, do not exhibit the interfold phenomenon seen in the above-mentioned polycrystalline diamonds and exhibit excellent wear resistance. Are known.

However, since these diamond sintered bodies contain a binder of several percent to several tens of percent, they have the problem that chipping occurs in the constituent particles. In particular, this chipping phenomenon becomes more noticeable when the wedge angle of the cutting edge of the tool becomes small, and it is extremely difficult to create a tool with a sharp cutting edge.

In order to suppress chipping of the cutting edge during tool making, it is possible to polish the cutting edge using a fine-grained diamond grindstone such as #3000 to #5000, but even with this method, the chipping of the cutting edge may be suppressed. Chipping 5
It was impossible to suppress the thickness to below μm. Further, in the polishing method using this fine-grained diamond grindstone, a new problem arises in that processing efficiency decreases as the grain size of the grindstone becomes finer.

In addition to the grinding process mentioned above, electric discharge machining and laser machining are known to be used as processing methods for diamond sintered bodies, but even when these processing methods are used, the diamond sintered bodies contain binder. Currently, it is not possible to obtain a tool with good edge sharpness because of this.

On the other hand, the inventors devised a cutting tool using polycrystalline diamond containing no binder, that is, a polycrystalline diamond tool material synthesized by a low-pressure vapor phase method, instead of the diamond sintered body. An example of a cutting tool made of polycrystalline diamond is disclosed in Japanese Patent Application Laid-Open No. 1-212.
This is shown in Japanese Patent No. 767.

[Problem to be solved by the invention] However, even when polycrystalline diamond is used as a tool material, when the cutting edge is formed by grinding, chipping of about 5 μm occurs on the cutting edge, and this cannot be suppressed. Ta. Therefore, the inventors newly devised the use of laser processing for cutting edge processing in order to improve the sharpness of cutting tools made of polycrystalline diamond as a tool material. That is, it is synthesized by a low-pressure gas phase method, and its surface roughness is 0.0 in the maximum height (Rmax) specified in JIS B 0601. We have devised a polycrystalline diamond cutting tool in which a tool material is polycrystalline diamond formed into a specular state of 1 μm or less, and the cutting edge flank of this tool material is formed using laser processing. A polycrystalline diamond cutting tool using this laser processing is described in Japanese Patent Application No. 2-271011 filed by the same applicant. When the roughness of the rake face of the tool is set to Rlao of 0°1 μm or less and the flank face is formed by laser processing, the roughness of the rake face is lower than that of a conventional polycrystalline diamond tool or a tool using a diamond sintered body. The sharpness of the blade has been significantly improved.

However, the flank face of the tool is formed by laser processing, and after this laser processing, a graphite coating layer is generated on the surface of the flank face due to the thermal influence of the laser processing. In tools used for applications where dimensional accuracy is strictly required, this graphite coating layer formed on the tool flank often causes welding of the rigid material, resulting in chipping during cutting or There is a concern that the problem of deterioration of the machined surface roughness may occur.

Therefore, the present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a polycrystalline diamond cutting tool that uses polycrystalline diamond as a tool material and has excellent edge sharpness, and a method for manufacturing the same. shall be.

[Means for Solving the Problems] This invention uses polycrystalline diamond synthesized by a low-pressure gas phase method as a tool material, and the rake face has a surface roughness of 0.1 μm in maximum height (R□ax). The flank face is formed so that the surface of the polycrystalline diamond is exposed, and the chipping size of the cutting edge along the intersection line between the rake face and the flank face is 0°5 μm or more and 5 μm or less.

This polycrystalline diamond cutting tool includes a structure in which a polycrystalline diamond tool material with a cutting edge processed is directly attached to a cutting device, or a structure in which such a polycrystalline diamond tool material is joined to a tool support.

Furthermore, the polycrystalline diamond cutting tool according to the present invention is
It is manufactured by the following steps.

First, the surface roughness is 0.1μ in maximum height display (Rmax)
Polycrystalline diamond is deposited on the surface of a base material having a size of less than m by a low pressure vapor phase method. Next, after cutting the polycrystalline diamond on the base material into a predetermined chip shape, the base material is removed from the polycrystalline diamond chip. Then, the surface of the polycrystalline diamond chip that intersects with the surface that was in contact with the base material is laser-processed to form a cutting edge flank.

Thereafter, the graphite coating layer formed on the flank of the cutting edge by laser processing is removed.

In addition, for polycrystalline diamond cutting tools with a structure in which a polycrystalline diamond tip is joined to a tool support,
After the base material has been removed, the polycrystalline diamond chip surface that was in contact with the base material is bonded to the tool support so that it becomes the rake face of the tool, and then a cutting edge flank surface is formed by laser processing. Ru.

[Operation Figures 1 to 6 are cross-sectional views of the manufacturing process of the polycrystalline diamond cutting tool according to the present invention.

The effects of the polycrystalline diamond cutting tool of the present invention will be explained with reference to FIGS. 1 to 6.

First, referring to FIG. 1, polycrystalline diamond is formed on the surface of a substrate 1 made of metal or alloy by using a low pressure vapor phase method. The surface roughness of the mirror surface of the substrate 1 is rounded 8. 0 at
．． Finished to a mirror surface of 1 μm or less. As a method for depositing polycrystalline diamond on this surface, the following low pressure vapor phase method is used. That is, a method in which thermionic radiation or plasma discharge is used to cause decomposition and excitation of the raw material gas, or a method in which a film is formed using a combustion flame are effective. As the raw material gas, a mixed gas whose main components are hydrogen and hydrocarbons such as methane, ethane, and propane, alcohols such as methanol and ethanol, and organic carbon compounds such as esters is generally used. In addition to this, inert gases such as argon, oxygen, carbon dioxide, water, etc. may also be contained in the raw material within a range that does not inhibit the diamond synthesis reaction or its properties. By such a low-pressure vapor phase method, the average crystal grain size of polycrystalline diamond is 0.5 mm on the surface of the substrate 1. It is synthesized to have a thickness of 5 to 15 μm. The grain size of this polycrystalline diamond is regulated because when used as a cutting tool, wear resistance decreases when the average crystal grain size becomes finer than 0.5 μm, and when it becomes coarser than 15 μm. This is because it becomes easy to lose. Further, in order to reduce the internal stress of polycrystalline diamond, the substrate 1 is preferably made of a material whose coefficient of thermal expansion is close to that of diamond, such as molybdenum (
Examples include Mo), tungsten (W), and silicon (Si).

Next, referring to FIG. 2, cutting lines are formed in polycrystalline diamond layer 2 formed on substrate 1 by a laser beam along a predetermined tool material shape.

Further, referring to FIG. 3, substrate 1 is dissolved and removed from the polycrystalline diamond by chemical treatment using hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or a mixture thereof. If the polycrystalline diamond tool material 3 thus formed has a thickness of 1 mm or more in the stacking direction, it can be directly processed to form a cutting edge, clamped in a holder, and used as a tool. Further, if the thickness is 0.05 to 1 mm, it may be used as a cutting tool joined to a tool support made of cemented carbide, steel, or the like. In the case of a cutting tool having such a structure to be joined to a tool support, if the thickness of the polycrystalline diamond tool material 3 is thinner than 0.05 mm, the strength as a tool material decreases and it becomes easy to break. Further, in such a joint type cutting tool, it is sufficient for the tool material to have a thickness of about 1 mm for use in boat fishing. In addition, as shown in FIG. 4, such a structure is such that the polycrystalline diamond tool material 3 and the tool support 4 are joined together so that the surface that was bonded to the substrate on the tool support 4 becomes the rake face 6. After attaching 5, it is essential to join.

Furthermore, referring to Fig. 5, by applying laser machining under appropriately selected conditions to the cutting edge forming process, a cutting tool with good edge sharpness that could not be obtained by grinding process can be created. . This is because the polycrystalline diamond used as the tool material does not contain any binder, and because laser machining involves a thermochemical reaction, there is less damage compared to grinding, which is a mechanical removal method. It is thought that it works. This laser processing requires YA from the point of view of processing efficiency and quality.
It is preferable to use a G laser. The laser beam is irradiated from the rake face 6 side of the tool or from the opposite side. At this time, the tool is installed and moved at an angle with respect to the laser beam so that a preset relief angle can be formed. Alternatively, a method may be used in which the tool is fixed and the laser beam is manipulated. The laser processing conditions are such that the chipping of the cutting edge is 0. 5
The thickness is selected to be 5 μm. The conditions are: single mode, average output 2-5 W19 switch repetition frequency 1-5 kHz, laser beam operation speed 0.
1 to 5 mm/see is preferred.

Incidentally, here, the size of chipping will be defined using FIG. 7. FIG. 7 is an enlarged view of the cutting edge portion of the indexable insert shown in FIG. 6, and schematically shows a state in which chipping 9 occurs along the intersection line of the rake face 6 and flank face 7. . The size of chipping is defined using the larger value of the length 1 measured from the intersection of the rake face 6 and flank face 7 toward the surface side of the rake face 6 and the length t2 measured toward the flank face 7 side. do. The lower limit value of this chipping size is 0, 5
μm is estimated from the inventor's experimental results, and it is possible to further reduce this chipping by changing the processing conditions.

Referring again to FIG. 5, after the cutting edge forming process using this laser process is completed, graphite is generated on the surface of the rake face 7 due to the laser process.

The thickness of this graphite coating layer 8 is approximately 0.5 to 10 μm.

Furthermore, referring to FIG. 6, after laser processing,
The graphite coating layer 8 formed on the flanks and the like is removed by the following chemical method. That is, a method of dissolving and removing it in an acid or alkali molten salt is used. The acid used is preferably dichromic acid or a mixture of sulfuric acid and nitric acid. When using a mixed solution of sulfuric acid and nitric acid, it is important to keep the mixing ratio in the range of 1:9 to 9:1 in order to efficiently dissolve graphite. In addition, alkaline molten salts include potassium hydroxide, potassium nitrate, sodium hydroxide,
Sodium nitrate or mixtures thereof can be used. In addition, in the case of a polycrystalline diamond cutting tool having a structure joined to the tool support 4 as shown in the figure, it is desirable to use an alkali molten salt in this graphite coating layer removal step.

This is because when an acid is used, there is a possibility that the brazing material and tool support used for joining may be damaged.

A polycrystalline diamond cutting tool made by such a method has a rake face with a maximum height of Rrn a
x is a mirror surface of 0.1 μm or less, the flank surface is not covered with graphite, polycrystalline diamond is exposed, and the cutting edge has a chipping of 0.5 μm.
It has excellent edge sharpness that is suppressed to a range of ~5 μm.

[Example] Below, an example of a polycrystalline diamond cutting tool actually manufactured using the above method will be described.

(Example 1) Microwave plasma 7CVD (Chemi ca 1V
By the apor depos it 1 on) method,
S whose surface is a mirror state with Rmax of 0.05 μm
Polycrystalline diamond was synthesized on the i-substrate for 10 hours under the following conditions.

Raw material gas (flow rate): R2200seemCH4,
10 sec Gas pressure: 120 Torr Microwave oscillation starting Shaking crab 650 After synthesis, by immersing in fluoronitric acid and dissolving and removing only the Si substrate, the average crystal grain size was 5 μm and the thickness was 0.2 mm.
We were able to recover polycrystalline diamonds. Also,
The surface on the substrate side was R18X and 0°05 μm. This polycrystalline diamond was joined by brazing to a cemented carbide shank with its growth surface as the joint surface. Next, hold this joint at an angle and form a cutting edge so that the laser beam for processing and the rake face of the joint make an angle of 101°.
4) was created. Note that a continuous wave mode YAG laser with an output of 3 W was used to form the cutting edge. The indexable tip (A) obtained had good chipping at the cutting edge of 1 μm, and the flank surface was coated with graphite with a thickness of 2 μm. Next, the chip, which had been laser processed under the same conditions as this indexable chip (A), was immersed for 30 minutes in an equal volume mixture of potassium nitrate and sodium nitrate heated to 500°C to dissolve and remove graphite. Recovered chips (B)
The graphite on the flank face was completely removed without any damage to the filler metal or shank, and the chipping on the cutting edge was 1 μm.
It remained m.

The performance of these indexable inserts as finishing tools was evaluated under the following conditions.

(Cutting conditions) Work material: AC4C-76 (Al-7%Si) round bar Cutting speed: 500m/min Depth of cut: 0. 2mm Feed speed: 0.　1mm/　r　e　v.

Coolant, water-soluble oil (Evaluation method) Comparison of work surface roughness after 5 minutes and 60 minutes of cutting.

As a result, as shown in Table 1 below, the tool of the present invention maintains a sharp cutting edge for a long time compared to the comparative tip (A), and can obtain a good work surface. became clear.

(Table 1) Tool No., Work surface roughness Rm a x (p m)
Comparison after 5 minutes cutting and after 60 minutes cutting A1.6 1.7 Present invention B 1. 2 1. 2(
Example 2) By thermal CVD using a linear tungsten filament with a diameter of 0.5 mm and a length of 100 mm as the thermionic emitting material, a multilayer film was deposited on a Mo substrate with a surface Rmax of 0.03 μm under the following conditions. Crystalline diamond was synthesized for 20 hours.

Raw material gas (flow rate): H2300sccmC2H2
15 sec Gas pressure + 80 Torr Filament temperature: 2150°C Filament-substrate distance: 5 mm Radiation degree: 920°C After synthesis, by immersing in hot aqua regia to dissolve and remove only the MO substrate, the average crystal grain size was 3 μm. So, the thickness is 0.15
It was possible to recover polycrystalline diamond of mm. Note that the surface on the substrate side was Rma-finished and had a mirror finish of 0.03 μm. This polycrystalline diamond was joined by brazing to a cemented carbide shank with its growth surface as the joint surface. Next, this joined body was held tilted, the YAG relay output was continuously oscillated at 3 W, and the cutting edge was processed using a laser beam irradiated from the rake face side to create an indexable tip with a wedge angle of 80''. The prototype chip (C) had a chipping of 2 μm and a flank surface coated with graphite having a thickness of 3 μm.

Next, the same chip was immersed for 3 minutes in a mixture of potassium nitrate and sodium hydroxide (mixed in a 2:1 ratio by volume) heated to 500° C. to dissolve and remove graphite.

In the recovered chip (D), both the brazing material and the shank were undamaged, the chipping was 2 μm, and the graphite on the flank surface had been completely removed.

The performance of these indexable inserts as finishing tools was evaluated under the following conditions.

(Cutting conditions) Work material: AC8A-T6 (Al-12%Si) round bar Cutting speed: 600m/min Depth of cut: 0.3mm Feed speed + 0.08 mm/r e v.

Coolant: Water-soluble oil (Evaluation method) Comparison of cutting edge wear (chip size) after 5 and 60 minutes of cutting.

The results of the performance evaluation test are shown in Table 2.

(Table 2) Tool No. 1 Lead removal result evaluation item 5 minutes cutting 11 Post comparison after 60 minutes cutting C
None Cutting edge chipping 20μm 25μm coverage
11 Surface roughness 1. hm 2.1g
m Invention D Yes Cutting edge chipping 5μ mountain
6μ machined surface roughness 1.1μml, 2μm
Comparative product (C) had more welding of the workpiece material on the cutting edge at the initial stage of cutting than inventive product (D), and it is presumed that chipping occurred at the initial stage due to this influence.

On the other hand, since there is no graphite on the flank surface of the invention (D), there is almost no welding of the work material to the cutting edge, and it is clear that the cutting edge remains sharp for a long time. .

(Example 3) H2, C2H6, and Ar
A gas mixture of 8:1:1 with a flow rate of 5QQsc
cm and the pressure was adjusted to 150 Torr.

Next, a high frequency (13.56 MH) was applied from a high frequency oscillator to excite the mixed gas to generate plasma, and synthesis was performed for 30 hours. Note that the high frequency output was selected in the range of 700 to 900 W for each synthesis experiment.

After each synthesis experiment was completed, the taken substrate was treated with hot aqua regia to recover polycrystalline diamond.

The obtained polycrystalline diamond has an average crystal grain size of 5 to 3
Although the thickness was different for each experiment, the thickness was 1.0 μm in all cases.
6 mm, and Rmax of both substrate side surfaces is 0.
．． It was in a mirror state of 0.06 μm.

In producing a throw-away chip (model number: TPGNO60104-B) from these polycrystalline diamonds, processing was performed using a YAG laser with different output conditions. Chips produced under the same conditions as these indexable chips (E, FSG) were further immersed in dichromic acid heated to 100° C. to remove graphite covering the flanks. After observing the machining conditions of the cutting edge of these chips (H, I, J) and chips that had not been acid-treated (E, F, G), cutting experiments were conducted under the following conditions to determine the roughness of the workpiece surface. We measured and evaluated the performance.

The conditions for the cutting test are shown below.

(Cutting conditions) Work material: AC4A-T6 (AI-10%Si) round bar Cutting speed: 300m/min Depth of cut: 0.15mm Feed speed; 0.08 mm/r e v.

Cutting time: 90 minutes Coolant: Water-soluble oil The results of the performance evaluation test are shown in Table 3.

(Table 3) Tool No. E F G HI J
Polycrystalline diamond grain size (μm) 5 30
12 5 30 12 Laser output (W)
! ,0 1.5 2.5 1.0 1
．． 5 2.5 Cutting edge tipping amount (μm)
230 4 230 4 Cutting edge graphite coating thickness (μm) 257000 Covered surface 1 degree R,,, (μm)
1.2 3.5 1.5 0.8 3.2 1.
Referring to Table 3, it is considered that chips F and I had too large a grain size of polycrystalline diamond, so large chipping occurred and a good machined surface could not be obtained. However, the chips (H, J) produced by the method of the present invention both have excellent sharpness, and compared to the comparative chips (E, G), there is no coating black smoke layer on the flank surface. It was found that good surface roughness could be obtained.

[Brief explanation of the drawing]

1 to 6 are manufacturing process diagrams showing the manufacturing process of a polycrystalline diamond cutting tool according to the present invention. FIG. 7 is an enlarged perspective view of the cutting edge portion of the polycrystalline diamond cutting tool according to the present invention. In the figure, 1 is a base material, 2 is a polycrystalline diamond layer formed by a low-pressure vapor phase method, 3 is a polycrystalline diamond chip, 4 is a tool support, 5 is a brazed part, 6 is a rake face, 7
8 indicates a flank surface, 8 indicates a graphite coating layer, and 9 indicates chipping. Patent applicant: Sumitomo Electric Industries, Ltd., -5 No. 1
Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (12)

[Claims] (1) A polycrystalline diamond cutting tool using polycrystalline diamond synthesized by a low-pressure vapor phase method, with a surface roughness of 0.1μ in maximum height (R_m_a_x)
m or less, and a flank face on which the surface of the polycrystalline diamond is exposed, and the size of chipping of the cutting edge along the intersection line of the rake face and the flank face is 0.5 μm or more and 5 μm or less. , polycrystalline diamond cutting tools. (2) The polycrystalline diamond constituting the polycrystalline diamond cutting tool has an average grain size of 0.5 μm or more and 15 μm.
The polycrystalline diamond cutting tool according to claim 1, wherein the polycrystalline diamond cutting tool has a diameter of less than m. (3) The polycrystalline diamond according to claim 1 or 2, wherein the polycrystalline diamond constituting the polycrystalline diamond cutting tool has a thickness of 0.05 mm or more and 1 mm or less in a direction substantially perpendicular to the rake face. diamond cutting tools. (4) A polycrystalline diamond cutting tool constructed by using polycrystalline diamond synthesized by a low-pressure vapor phase method as a tool material and bonding this tool material to a tool support, with surface roughness indicating the maximum height. (R_m_a_x) is 0.1μ
m or less, and a flank surface on which the surface of the polycrystalline diamond is exposed, and the chipping size of the cutting edge along the intersection line of the rake face and the flank surface is 0.5 μm or more and 15 μm or less. , polycrystalline diamond cutting tools. (5) The polycrystalline diamond cutting tool according to claim 4, wherein the average grain size of the polycrystalline diamond of the tool material is 0.5 μm or more and 15 μm or less. (6) The thickness of the polycrystalline diamond of the tool material in the direction substantially perpendicular to the rake face is 0.05 mm or more and 1 mm.
The polycrystalline diamond cutting tool according to claim 4 or claim 5, which is as follows. (7) Surface roughness is 0 in maximum height display (R_m_a_x)
．． A step of depositing polycrystalline diamond on the surface of a base material of 1 μm or less by a low-pressure vapor phase method, and cutting the polycrystalline diamond on the base material into a predetermined chip shape, and then depositing the polycrystalline diamond on the base material. of the polycrystalline diamond chip surface;
A step of laser processing a surface that intersects with the surface that was in contact with the base material to form a flank of the cutting edge, and a step of removing a graphite coating layer generated on the flank of the cutting edge by the laser processing. Also, a method for manufacturing polycrystalline diamond cutting tools. (8) The method for manufacturing a polycrystalline diamond cutting tool according to claim 7, wherein the graphite coating layer is removed by a chemical method. (9) The graphite coating layer is dissolved and removed by an acid solution.
A method for manufacturing a polycrystalline diamond cutting tool according to claim 8. (10) A step of depositing polycrystalline diamond on the surface of a base material having a surface roughness of 0.1 μm or less in maximum height (R_m_a_x) by a low-pressure vapor phase method, and depositing the polycrystalline diamond on the base material. After cutting into the specified chip shape,
a step of removing the base material from the polycrystalline diamond chip, and attaching the polycrystalline diamond chip to a tool support such that the surface of the polycrystalline diamond chip that was in contact with the base material becomes the rake face of the tool. a step of joining the polycrystalline diamond to a surface that intersects the rake face with a laser to form a flank of the cutting edge, and removing a graphite coating layer generated on the flank of the cutting edge by the laser processing. A method for manufacturing a polycrystalline diamond cutting tool, comprising a process. (11) The method for manufacturing a polycrystalline diamond cutting tool according to claim 10, wherein the graphite coating layer is removed by a chemical method. (12) The method for manufacturing a polycrystalline diamond cutting tool according to claim 11, wherein the graphite coating layer is removed using a molten alkali salt.