JP7250720B2 - Cutting tools and cutting methods - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cutting tool having an insert and a cutting method for use in cutting a work material.

2. Description of the Related Art Conventionally, cutting using inserts for face milling or the like has been used for processing steel materials. Cutting a steel material with such an insert may cause chipping of the cutting edge. In particular, when applied to rough machining of high-hardness steel materials that generate high loads, the stress applied to the cutting edge increases, causing severe chipping of the cutting edge and shortening the life of the insert.

Techniques for preventing chipping of inserts have been proposed, for example, in Patent Document 1 and Patent Document 2. The technique of Patent Document 1 suppresses chatter vibration and prevents breakage of the cutting edge by setting the cutting edge angle of a milling tip for rough cutting of castings to 70° or more and 80° or less. In addition, the technique of Patent Document 2 is intended to prevent chipping of the cutting edge while suppressing an increase in cutting resistance by making the rake angle of the four corners of the milling insert negative and making the rake angle other than the four corners positive. .

Japanese Utility Model Laid-Open No. 61-201716 JP-A-7-276130

However, the technique of Patent Document 1 is used for rough cutting of castings with relatively low hardness. It is difficult to prevent cutting edges from chipping due to high loads such as rough machining of hard steel materials.

In addition, the technique of Patent Document 2 is a precision machining technique, and when this technique is applied to rough machining of steel materials, especially high-hardness steel materials, a large load is applied to the middle of the cutting edge other than the four corners. Chipping occurs, and chipping occurs from the middle of the cutting edge.

Therefore, an object of the present invention is to prevent chipping caused by chipping on the entire cutting edge of an insert when applied to cutting a work material made of a steel material, particularly rough machining of a work material made of a high-hardness steel material. To provide a cutting tool and a cutting method capable of suppressing friction and having a long insert life.

In order to solve the above problems, the present invention provides the following (1) to (11).

(1) A cutting tool used for cutting a work material,
An insert having a rake face and a flank face and a cutting edge consisting of a ridgeline formed by the rake face and the flank face has an entering angle that is the angle formed by the surface of the work material and the cutting edge. Attached to the cutter body,
The insert has a tip angle formed by the rake face and the flank face according to the cutting angle so that the stress applied to the tip of the cutting edge during cutting is less than or equal to a predetermined value. A cutting tool characterized by:

(2) The insert is attached to the cutter body so that the included angle is 80° or more and less than 105° and the cutting angle is 45° or more and less than 90° (1) The cutting tool described in .

(3) The cutting tool according to (1) or (2), wherein the insert is attached to the cutter body so that the axial rake is 10° or more and 35° or less.

(4) The cutting tool according to any one of (1) to (3), wherein the insert is made of a low toughness material having a fracture toughness of 20 MPa·m ^1/2 or less.

(5) The cutting tool according to any one of (1) to (4), which is applied to a work material made of a steel material having a Vickers hardness of HV250 or more.

(6) A cutting method for cutting a work material with a cutting tool,
An insert having a rake face and a flank face and a cutting edge consisting of a ridgeline formed by the rake face and the flank face, with an entering angle that is the angle between the surface of the work material and the cutting edge Cutting is performed using a cutting tool attached to the cutter body,
The cutting edge angle formed by the rake face and the flank face of the insert is adjusted according to the cutting angle so that the stress applied to the cutting edge of the cutting edge of the insert during cutting is less than or equal to a predetermined value. A cutting method characterized by setting

(7) The insert has a cutting edge angle of 80° or more and less than 105°, and the insert is mounted on the cutter body so that the cutting angle is 45° or more and less than 90°. The cutting method according to (6).

(8) The cutting method according to (6) or (7), wherein the insert is attached to the cutter body so that the axial rake of the insert is 10° or more and 35° or less.

(9) The cutting according to any one of (6) to (8), wherein the insert is made of a low-toughness material having a fracture toughness of 20 MPa·m ^1/2 or less and is attached to the cutter body. Method.

(10) The cutting method according to any one of (6) to (9), wherein a work material made of a steel material having a Vickers hardness of HV250 or more is cut.

(11) The cutting method according to any one of (6) to (10), wherein the cutting is performed under cutting conditions of 0.25 mm or more per blade feed and 2 mm or more of cutting depth. .

According to the present invention, the cutting edge angle of the insert is appropriately set according to the cutting angle to reduce the stress applied to the cutting edge of the cutting edge to a predetermined value or less. When applied to rough machining of a work material made of a high-hardness steel material that generates a high load, it is possible to suppress fracture due to chipping that occurs on the entire cutting edge, and to extend the life of the insert.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the cutting tool which concerns on one Embodiment, (a) is sectional drawing, (b) is a front view. 1, (a) is a view seen from the same direction as the cross-sectional view of FIG. 1, (b) is a view seen from the B direction of the cross-sectional view of FIG. 1, ( c) is a view seen from the direction C of the cross-sectional view of FIG. 2 is a perspective view showing a state of an insert when rough machining a work material with the cutting tool of FIG. 1; FIG. It is a diagram showing the state of the insert when rough machining a work material with the cutting tool of FIG. 1, (a) is a view seen from the D direction of FIG. FIG. (c) is a view seen from direction F in FIG. 3 is a perspective view showing the cutting angle α, clearance angle β, and cutting edge angle γ. FIG. FIG. 3 is a perspective view showing an axial rake δ; 4 is a graph showing the relationship between the cutting edge angle and the cutting area ratio at cutting angles of 15°, 45°, 60°, 75° and 90°. FIG. 4 is a diagram showing the relationship between the cutting edge angle and the tensile stress generated at the cutting edge; 4 is a graph showing the relationship between the cutting area ratio and the axial rake of −30°, −20°, −10°, 0°, 10°, 20°, and 30°.

The present invention will be described in detail below.
In the insert, the ridge line formed by the rake face and the flank face serves as a cutting edge, and cutting is performed by this cutting edge. The rake face is the main cutting surface of the insert, on which chips pass while rubbing against each other. A flank is a relief surface to prevent contact between the insert and the machined surface.

Conventionally, cutting has not been used for high-load cutting such as cutting of steel materials, especially rough machining of high-hardness steel materials. , and was used only for applications with relatively small stress, such as precision machining as in Cited Document 2. For this reason, in Patent Document 1, chatter vibration is suppressed by setting the cutting edge angle of the insert to 70° or more and less than 80°. By making positive, it was possible to prevent chipping of the cutting edge. However, in the cutting of steel materials, especially in rough machining of work materials made of high-hardness steel materials, the stress applied to the cutting edge of the cutting edge of the insert is much larger than in the case of precision machining, etc., and the method of Patent Document 2 However, it was found that chipping may occur on the entire cutting edge, leading to chipping of the cutting edge.

Therefore, the present inventors have sought to obtain an insert that is less likely to cause chipping of the cutting edge even if the cutting of the work material is applied to the cutting of steel materials, especially to the rough machining of work materials made of high-hardness steel materials. I considered it. As a result, increasing the bevel angle increases the strength of the cutting edge and reduces the stress on the cutting edge. Also, the cutting resistance changes depending on the cutting angle, which is the angle between the surface of the work material and the flank, and the cutting edge angle is optimized according to the cutting angle to balance the cutting resistance and cutting edge strength. It was found that the stress applied to the cutting edge can be reduced and chipping can be suppressed. Cutting resistance also changes depending on the axial rake, which is the angle between the cutting edge ridge line and the axis when viewed from the front of the tool in the radial direction. I have found that it can be suppressed.

Conventionally, since the cutting surface becomes rough when the cutting edge angle is increased, the cutting edge angle is about 75°, and there was no idea of increasing the cutting edge angle. In such a case, there is no problem even if the included angle is increased, and the included angle can be set larger as the cutting resistance increases as the cutting angle increases.

Therefore, in the present invention, the cutting edge angle over the entire cutting edge is set so that the stress applied to the cutting edge of the cutting edge is less than or equal to a predetermined value according to the cutting angle, which is an index of cutting resistance. Specifically, there is a cutting edge angle at which the stress applied to the cutting edge of the cutting edge is minimal, and the cutting edge angle is set so that the stress applied to the cutting edge is equal to or less than a predetermined value near the minimum value.

In this way, by appropriately setting the cutting edge angle and reducing the stress applied to the cutting edge of the cutting edge to a predetermined value or less, cutting can be performed on a work material made of steel material, especially when a high load is generated. When applied to rough machining of a work material made of a high-hardness steel material, it is possible to suppress fracture due to chipping that occurs on the entire cutting edge, and to extend the life of the insert.

At this time, the predetermined value of the stress is preferably a value that is 30% larger than the minimum value of the stress applied to the cutting edge at the predetermined cutting angle. When the stress is below this value, chipping of the cutting edge can be effectively suppressed. Additionally, by optimizing the axial rake, further edge chipping can be prevented and insert life can be extended.

As a specific numerical value, it is preferable that the included angle is set in the range of 80° or more and less than 105° over the entire cutting edge when the cutting angle is in the range of 45° or more and 90° or less. Further, in the present invention, the cutting angle is in the range of 60° or more and 75° or less, the included angle is in the range of 80° or more and 100° or less over the entire cutting edge, and the cutting angle is in the range of 75° or more and 90° or less, It is particularly effective if the included angle is in the range of 80° or more and 90° or less over the entire cutting edge. Axial rake is effective in the range of 10° or more and 35° or less, and is particularly effective in the range of 25° or more and 35° or less.

The present invention is effective for work materials made of steel materials having a Vickers hardness of HV250 or more. Moreover, the present invention is particularly effective for work materials made of steel materials having a HV of 300 or higher. Suitable applications include descaling of steel slabs.

In addition, the present invention makes it possible to apply the cutting of the work material to steel materials, and is particularly effective for rough machining of high-hardness steel materials that are subject to high loads. Rough machining is a rough machining that does not require precision. In the case of descaling, it is sufficient to remove the scale, and the cutting conditions are large feed and large depth of cut. In the present invention, in such rough machining, even if the cutting conditions are 0.25 mm or more per tooth feed and 2 mm or more depth of cut, chipping occurring on the entire cutting edge can be suppressed.

Further, in the present invention, the insert may be a low toughness material with a fracture toughness of 20 MPa·m ^1/2 or less. Even with such a low-toughness material, it is possible to suppress chipping that occurs on the entire cutting edge. A super steel alloy (WC-based material) can be given as such a low-toughness material.

The inserts used in the present invention include inserts for face milling, inserts for cylindrical milling, and end mills.

Next, specific embodiments of the present invention will be described.
FIG. 1 is a diagram showing a cutting tool according to one embodiment, where (a) is a cross-sectional view and (b) is a front view. FIG. 1 shows a case where a face milling cutter is used as a cutting tool. As shown in FIG. 1, the cutting tool 1 has a cutter body 10, and the cutter body 10 is provided rotatably about a shaft 11 as a rotation axis. A plurality of inserts (milling inserts) 20 (only one is shown) are detachably attached to the outer peripheral portion of the distal end of the cutter body 10 at equal intervals in the circumferential direction of the cutter body 10 .

The insert 20 is generally rectangular as shown in FIG. 2 and constructed as described above. 2 (a) is a view seen from the same direction as the cross-sectional view of FIG. 1, (b) is a view seen from the B direction of the cross-sectional view of FIG. 1, and (c) is a view from the C direction of the cross-sectional view of FIG. It is a view.

Four sides of the insert 20 are cutting edges 23 . The insert 20 has a rake face 21 and a flank face 22 , and the ridge line where these intersect is the cutting edge 23 . The angle formed by the rake face 21 and the flank face 22 with the cutting edge 23 therebetween is the tip angle γ. The angle formed by the surface 24 of the steel material (high-hardness steel material) that is the work material and the flank surface 22 of the insert 20 is the cutting angle α. Furthermore, the angle between the flank 22 and a tangent 25 to the finished surface (the surface after cutting) is the flank angle β.

In the cutting tool 1 configured as described above, by rotating the cutter body 10 about the shaft 11 as a rotation axis, the insert 20 is rotated as shown in FIG. . The cutting angle α, the clearance angle β, the cutting edge angle γ, and the axial rake δ at this time are shown in FIG. ), as shown in FIG. The axial rake δ is the angle formed by the cutting edge 23 and the shaft 11 when the front surface of the tool is viewed from the radial direction. Fig. 5 clearly shows the cutting angle α, the clearance angle β, and the cutting edge angle γ. FIG. 6 clearly shows the axial rake δ. If the axial rake δ is too large, the insert 20 contacts the steel material, and if it is too small, the insert 20 cannot be attached to the cutter body 10. Therefore, the axial rake δ is set in the range of −30° or more and 35° or less.

The cutting edge angle γ of the insert 20 is set according to the cutting angle α so that the stress applied to the cutting edge of the cutting edge 23 does not cause chipping on the cutting edge. At this time, it is preferable that the stress applied to the cutting edge is within a range of 30% larger than the minimum value.

As a specific numerical value, it is preferable that the included angle is set in the range of 80° or more and less than 105° over the entire cutting edge when the cutting angle is in the range of 45° or more and 90° or less. In addition, when the cutting angle is in the range of 60 ° or more and 75 ° or less, the cutting edge angle is in the range of 80 ° or more and 100 ° or less over the entire cutting edge, and when the cutting angle is in the range of 75 ° or more and 90 ° or less, the cutting edge angle is It is particularly preferable to set the angle in the range of 80° or more and 90° or less over the entire cutting edge. Axial rake is effective in the range of 10° or more and 35° or less, and is particularly effective in the range of 25° or more and 35° or less.

By using such an insert 20, even when applied to rough machining of high-hardness steel materials with a high load of HV250 or higher, especially HV300 or higher, it is possible to suppress fracture due to chipping occurring on the entire cutting edge. The life of the insert can be extended.

Moreover, the insert 20 may be made of a low-toughness material with a fracture toughness of 20 MPa·m ^1/2 or less, and even with such a low-toughness material, chipping occurring on the entire cutting edge can be suppressed. Further, when performing rough machining of a high-hardness steel material as cutting, even if the cutting conditions for rough machining are 0.25 mm per blade feed or more and a cutting depth of 2 mm or more, the entire cutting edge 23 Chipping that occurs can be suppressed.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the idea of the present invention. For example, in the above embodiments, the face milling cutter is used as the cutting tool, but other cutting tools such as a cylindrical milling cutter and an end mill can be used.

In addition, as the cutting of steel materials, slab descaling, which is rough machining of work materials made of high-hardness steel materials, has been exemplified. It can be applied to rough machining of materials, and can also be applied to cutting other than rough machining.

Next, examples of the present invention will be described.
Here, cutting tools were used in which cemented carbide inserts with various edge angles were attached to the face milling cutter body. A cutting experiment was performed on a work material made of steel material with a hardness of HV250 or higher, with cutting conditions of 0.25 mm or more per tooth feed and 2 mm or more depth of cut by changing the cutting angle of the cutting tool. . The cuttable area of each cutting tool (cutting area when the wear amount of the flank of the insert reaches 2 mm, or cutting area when the insert is chipped) was obtained from the cutting experiment. The results are shown in FIG. FIG. 7 is a graph showing the relationship between the cutting edge angle and the cutting area ratio at cutting angles of 15°, 45°, 60°, 75°, and 90°. The cutting area ratio was obtained by setting the cuttable area of a cutting tool having an insert with a cutting edge angle of 75° to a cutter body with a cutting angle of 15° as 1.

From this figure, it can be seen that the cutting area ratio is large when the included angle is in the range of 80° or more and 100° or less over the entire cutting edge, especially when the cutting angle is in the range of 60° or more and 75° or less. In addition, it can be seen that the cutting area ratio is large when the cutting angle is in the range of 75° or more and 90° or less and the cutting edge angle is in the range of 80° or more and 90° or less over the entire cutting edge.

Next, using cemented carbide inserts with various cutting edge angles, a work material made of a steel material with a hardness of HV250 or higher is cut under cutting conditions of 0.25 mm per blade feed or more and a depth of cut. Rough machining was performed to a depth of 2 mm or more, and the tensile stress generated at the cutting edge for each cutting edge angle over the entire cutting edge in a state where the insert was worn was determined. FIG. 8 is a diagram showing the relationship between the cutting edge angle and the tensile stress generated at the cutting edge.

From this figure, it can be seen that the stress applied to the cutting edge at an angle of 80° or more and less than 105° becomes a minimum value or a value in the vicinity thereof, and chipping can be suppressed.

Furthermore, cutting experiments were performed using a cutting tool in which the axial rake was increased by 10° from -30° to 30°, a cemented carbide insert was used, and the cemented carbide insert was attached to the face milling cutter body. gone. Here, the cutting angle of the cutting tool was changed and the cutting conditions were set to 0.25 mm or more per blade feed and 2 mm or more depth of cut for a work material made of steel material having a hardness of HV250 or more. The cuttable area of each cutting tool (cutting area when the wear amount of the flank of the insert reaches 2 mm, or cutting area when the insert is chipped) was obtained from the cutting experiment. FIG. 9 is a graph showing the relationship between axial rake and cutting area ratio. The cutting area ratio was obtained by setting the cuttable area to 1 when the axial rake was 0°.

From this figure, it can be seen that the cutting area ratio is large when the axial rake is in the range of 10° or more and 35° or less, particularly in the range of 25° or more and 35° or less.

1 face mill (cutting tool)
10 cutter body 11 shaft 20 insert 21 rake face 22 flank face 23 cutting edge 24 surface of steel material (high-hardness steel material) 25 tangent to finished surface α cutting angle β relief angle γ cutting edge angle δ axial rake

Claims (9)

A cutting tool used for rough machining of a work material made of high-hardness steel material,
An insert having a rake face and a flank face and a cutting edge consisting of a ridgeline formed by the rake face and the flank face has an entering angle that is the angle formed by the surface of the work material and the cutting edge. Attached to the cutter body,
The insert has an included angle formed by the rake face and the flank face according to the cutting angle so that the stress applied to the cutting edge of the cutting edge during the rough machining is less than or equal to a predetermined value. and is attached to the cutter body so that the included angle is 80° or more and less than 105° over the entire cutting edge , and the cutting angle is 45° or more and less than 90°. 2. The cutting tool according to claim 1, wherein the insert is attached to the cutter body so that the axial rake is 10[deg.] or more and 35[deg.] or less. 3. The cutting tool according to claim 1, wherein the insert is made of a low toughness material having a fracture toughness of 20 MPa·m ^1/2 or less. 4. The cutting tool according to any one of claims 1 to 3, wherein the cutting tool is applied to a work material made of a steel material having a Vickers hardness of HV250 or higher. A cutting method for roughing a work material made of a high-hardness steel material with a cutting tool,
An insert having a rake face and a flank face and a cutting edge consisting of a ridgeline formed by the rake face and the flank face, with an entering angle that is the angle between the surface of the work material and the cutting edge Rough machining is performed using a cutting tool attached to the cutter body,
An included angle formed by the rake face and the flank face of the insert according to the cutting angle so that the stress applied to the cutting edge of the cutting edge of the insert during the rough machining is equal to or less than a predetermined value. and mounting the blade on the cutter body so that the included angle is 80° or more and less than 105° over the entire cutting edge , and the cutting angle is 45° or more and less than 90°. 6. The cutting method according to claim 5, wherein the insert is mounted on the cutter body so that the axial rake of the insert is 10[deg.] or more and 35[deg.] or less. 7. The cutting method according to claim 5, wherein the insert is made of a low-toughness material having a fracture toughness of 20 MPa·m ^1/2 or less and is attached to the cutter body. 8. The cutting method according to any one of claims 5 to 7, wherein a work material made of a steel material having a Vickers hardness of HV250 or higher is roughly machined. 9. The cutting method according to any one of claims 5 to 8, wherein the rough machining is performed under cutting conditions of 0.25 mm or more per blade feed and 2 mm or more of cutting depth.

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