JP2011020250A - Cutting edge replaceable cutting tool for machining blade root groove - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting edge replaceable cutting tool for machining a blade root groove which improves rigidity of a tool body, reduces cutting resistance, and improves breakage resistance in a small diameter size cutting edge replaceable cutting tool for machining the blade root groove which performs semi-finish machining to finish machining. <P>SOLUTION: The cutting edge replaceable cutting tool has an enlarged diameter part, in which a tool diameter is smoothly increased from the tip end of a rotary cutting tool toward the rear end side in the axial direction on a cutting blade ridge line, and a reduced diameter part, in which the tool diameter is smoothly reduced from the enlarged diameter part toward the rear end side in the axial direction. When the maximum value of the tool diameter of the enlarged diameter part is D2, and the minimum value of the tool diameter of the reduced diameter part is D1, they satisfy the relation: D1<D2. The thickness of an insert is reduced from the outer peripheral side in the radial direction of the rotary cutting tool toward the inner peripheral side. When a rake angle (degree) in the radial direction of the enlarged diameter part is Rr, Rr is more than zero, and the rotary cutting tool has a groove-shaped insert seat. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cutting edge exchangeable cutting tool for blade root groove machining such as a turbine blade blade. In particular, the present invention relates to a blade diameter grooving cutting edge exchangeable cutting tool that can be used when the minimum diameter is 10 mm or less.

  Patent Documents 1 to 3 disclose rotary cutting tools used for turbine blade blade root groove machining. The ones described in Patent Documents 1 and 2 are blade-cutting-type rotary cutting tools used for Christmas tree-shaped turbine blade blade root groove processing. There has been proposed a rotary tool for finishing which is composed of inserts. Patent Document 3 proposes a finishing method, and FIGS. 1 and 2 show a rotary tool used for the finishing method.

Japanese Patent No. 3737236 JP 2000-254812 A JP 2008-213127 A

  However, in the past, when using a small-diameter-sized blade root grooving cutting tool, especially when performing finishing from intermediate finishing, the cutting resistance is remarkably increased, so that the resistance to breakage of the small-diameter portion is reduced. The lack of sex was a problem.

  Accordingly, it is an object of the present invention to improve the breakage resistance and reduce the cutting resistance in a blade-cut groove cutting tool for blade root groove machining (especially for small-diameter size) that performs finishing from intermediate finishing to reliability. An object of the present invention is to provide a cutting edge exchangeable cutting tool for blade root groove processing with high performance.

The present invention relates to a blade tip grooving cutting edge replaceable rotary cutting tool in which an insert made of a WC-base cemented carbide is detachably attached to the tip of a tool, and the cutting edge ridge line of the insert is pivoted from the tip of the rotary cutting tool. A diameter-enlarged portion in which the tool diameter increases smoothly toward the rear end side in the direction, and a diameter-reduced portion in which the tool diameter decreases smoothly from the diameter-enlarged portion toward the rear end side in the axial direction. When the maximum value of the tool diameter at D2 is D2 and the minimum value of the tool diameter at the reduced diameter portion is D1, the D1 value and the D2 value have a relationship of D1 <D2, and the thickness of the insert is Rr> 0, when Rr is a rake angle (degree) in the radial direction of the diameter-enlarged portion that decreases from the outer circumferential side to the inner circumferential side of the rotary cutting tool, and the rotary cutting tool is Cutting edge exchangeable rotary cutting for blade root groove processing, characterized by having a groove-shaped insert seat It is a tool.
ADVANTAGE OF THE INVENTION According to this invention, the blade-tip-groove cutting type exchange cutting tool for blade root groove processing which improved breakage resistance can be provided.

  The blade tip exchange type rotary cutting tool for blade root groove processing of the present invention is suitable for turbine blade blade root groove processing. In particular, in order to meet the practical needs, the lower limit value of the D1 value is preferably about 8 mm, more preferably 8 ≦ D1 ≦ 10, for a small-diameter size from intermediate finishing to finishing.

  ADVANTAGE OF THE INVENTION According to the present invention, the blade tip grooved cutting edge exchange type rotary cutting tool which has markedly improved breakage resistance, particularly as a blade diameter groove cutting edge exchange type rotary cutting tool which performs from intermediate finishing to finishing processing. Tools can be provided.

  It is a figure explaining a blade root groove processing process.   The perspective view of the example 1 of the present invention is shown.   The enlarged view of the rotary tool front-end | tip part of the example 1 of this invention is shown.   The right view of FIG. 3 is shown.   The rotary tool main body of FIG. 4 is shown.   An example of a cross-sectional view perpendicular to the axis of the reduced diameter portion of Example 1 of the present invention is shown.   The axis perpendicular cross section in the diameter-reduction part of the prior art example 3 is shown.   FIG. 3 is a cross-sectional view perpendicular to the axis of the enlarged diameter portion of Example 1 of the present invention.   The calculation result by stress analysis is shown.

FIG. 1 is a diagram schematically illustrating steps from intermediate finishing to finishing using the blade root groove cutting type rotary cutting tool for blade root groove processing of the present invention.
For example, in the processing when the minimum diameter of the Christmas tree-shaped turbine blade blade root groove is 10 mm or less, as shown in FIG. 1, rough processing by the first step and the second step, the third step, The process is divided into a plurality of processes, such as the intermediate finishing process by the fourth process and the finishing processes by the fifth process and the sixth process.

  The rough machining in the first step is performed using, for example, a taper end mill for rough machining having a luffing cutting edge, and the groove cross section is formed into a substantially V-shaped shape. In particular, if the minimum diameter of the final shape of the Christmas tree-shaped blade root groove is 10 mm or less, using a total milling tool for rough cutting that approximates the Christmas tree shape will reduce tool breakage at the small diameter part of the tool. It is inappropriate because it invites you. In the roughing process in the second step, for example, a roughing end mill having a roughing cutting edge is used to form a groove having a minimum diameter portion.

  In the third finishing process, a portion having a large groove diameter in the blade root groove having a Christmas tree shape is processed. In the fourth finishing process, a portion having a small groove diameter in the blade root groove having a Christmas tree shape is processed. In particular, in the intermediate finishing of the third step, the machining margin becomes uneven over the length of the cutting edge, so measures for reducing cutting resistance to reduce the burden on the cutting edge and machining of parts with a small groove diameter Therefore, it is necessary to improve the breakage resistance in a portion having a small tool diameter. Therefore, by using the blade-tip-grooving rotary cutting tool for blade root groove processing according to the present invention, the intermediate finishing of the third step can be cleared without any problem.

  In the finishing process of the fifth step, a part having a large groove diameter in the blade root groove having a Christmas tree shape is processed. In the finishing process of the sixth step, a part having a small groove diameter in the blade root groove having a Christmas tree shape is processed. The machining margin in this finishing process is set so as to be substantially uniform over the length of the cutting edge, and is set so that the burden on the cutting edge is even. Also in the finishing process of the fifth step, the blade edge groove cutting edge type rotary cutting tool of the present invention can be used.

Here, the reason for dividing the second and third process intermediate finishing processes and the fourth and fifth process finishing processes into two processes according to the respective groove diameters is to divide the processes into parts having a larger groove diameter. This is because high-efficiency cutting can be performed by selecting appropriate cutting conditions for a small portion.
Therefore, the cutting time can be shortened by adopting highly efficient cutting conditions. This shortening of the cutting time has an effect more than offsetting the time required for tool change or the like.

  As described above, in the processing of the smallest diameter portion in the Christmas tree-shaped groove shape, which is performed by using the blade-tip-growing rotary cutting tool for blade root groove processing of the present invention, rotation with improved breakage resistance is achieved. It is important to use a cutting tool. The reason for this is that, especially in rotary cutting tools used for turbine rotor blade root groove processing, etc., there is a tendency for the tool diameter to be easily broken at the part where the tool diameter is the minimum diameter. This leads to a serious accident. Therefore, it is necessary to improve the breakage resistance by increasing the rigidity of the blade-cutting-type rotary cutting tool for blade root groove machining.

  The blade-tip-grooving rotary cutting tool for blade root grooving of the present invention has a reduced-diameter insert seat formed into a groove shape, and a rake angle in the radial direction without decreasing the tool body rigidity by using an insert rake face as an inclined plane. By adopting a structure that allows the cutting force to be reduced by setting to a positive value, the breakage resistance is remarkably improved as compared with the conventional one. Hereinafter, the configuration of the present invention will be described in detail with reference to the drawings.

FIGS. 2 to 6 and FIG. 8 are views showing Example 1 of the present invention of the blade-tip-exchange-type rotary cutting tool to which one insert is attached. In addition, it is good also as a structure which attached two or more said inserts as a rotary cutting tool of this invention. FIG. 2 is a perspective view of Example 1 of the present invention. FIG. 3 shows an enlarged view of the tool tip portion of Example 1 of the present invention. FIG. 4 shows a right side view of FIG. FIG. 5 shows the rotary tool body of FIG. FIG. 6 is a cross-sectional view perpendicular to the axis of the reduced diameter portion of Example 1 of the present invention. FIG. 7 is a cross-sectional view perpendicular to the axis of the reduced diameter portion of Conventional Example 3. FIG. 8 is a cross-sectional view perpendicular to the axis of the enlarged diameter portion of Example 1 of the present invention.
As shown in FIG. 2, an insert 3 is detachably fixed to a tool body 1 via a clamp screw 2 to constitute a cutting tool of the present invention. The cutting edge ridge line of the insert 3 has an enlarged diameter portion in which the tool diameter smoothly increases from the front end of the rotary cutting tool toward the axial rear end side, and a tool diameter from the enlarged diameter portion toward the axial rear end side. Was formed to have a reduced diameter portion that smoothly decreased.
As shown in FIG. 3 and FIG. 4, when the maximum value of the tool diameter in the enlarged diameter portion of the insert 3 is D2, and the minimum value of the tool diameter in the reduced diameter portion is D1, the D1 value and the D2 value Was formed so as to satisfy the relationship of D1 <D2. The D1 value of the tool of the present invention is a small diameter tool of about 10 mm, preferably 10 mm or less. As shown in FIG. 5, the groove-shaped insert seat 6 is provided from the reduced diameter portion toward the tool rear end in the rotation axis direction of the tool.
Further, as shown in FIG. 6, the insert thickness T (mm) of the reduced diameter portion 5 was formed so as to decrease from the outer peripheral side to the inner peripheral side in the tool radial direction. 5 and 6 show the groove length L and the groove width W of the groove-shaped insert seat 6. When the insert 3 was mounted on the tool body 1, the Rr value of the reduced diameter portion 5 shown in FIG. 6 and the enlarged diameter portion 4 shown in FIG. 8 was formed so that Rr> 0.

In Example 1 of the present invention, a groove-shaped insert seat is formed in the vicinity of the reduced diameter portion to increase the cross-sectional area of the reduced diameter portion, thereby ensuring rigidity.
In order to evaluate the rigidity, D1 value is 10 mm, D2 value is 17 mm, and the insert thickness at the outer peripheral blade at the position where D2 value is taken is T1, and the innermost insert thickness is T2. The T1 value was 2.5 mm and the T2 value was 1.5 mm. The groove width W of the groove-shaped insert seat is 2.7 mm, and the groove length L is from the position where the tool diameter reaches the minimum D1 value toward the tip end of the tool rotation axis until the tool diameter becomes D2. The distance. This was created as the model shape of Example 1 of the present invention. On the other hand, the model shape of Conventional Example 3 basically conforms to Example 1 of the present invention, but has no groove-shaped insert seat. Using these model shapes, the Mises equivalent stress was calculated with a load of 900 N using finite element method analysis software. As a result of the calculation, the stress value of the reduced diameter portion in Example 1 of the present invention was 400 MPa, and that of Conventional Example 3 was 538 MPa. It was found that the stress value of Example 1 was reduced by about 25%. Furthermore, as shown in the calculation results shown in FIG. 9, the stress value was calculated by forming the length L value of the groove-shaped insert seat long in the tool tip direction by 1 mm, but the stress value was converged. It has been found that the insert seat is sufficient up to the reduced diameter portion. As a material for forming the tool body, it is desirable to use an alloy material having a tensile strength of 2 GPa or more.

It is conceivable to reduce the cutting resistance as a method of reducing the stress value of the reduced diameter portion. Generally, the cutting resistance decreases as the Rr value is increased positively. For example, it is a common practice to increase the Rr value by providing a breaker groove in the insert. However, since the shape of a blade root groove processing tool is complex and high accuracy is required, it must be cut while maintaining accuracy. It is difficult to form a breaker groove along the blade.
Therefore, in Example 1 of the present invention, as shown in FIG. 8, the insert thickness T1 value at the diameter-enlarged portion of the tool cutting blade gradually decreases from the outer peripheral side in the radial direction toward the inner peripheral side. It forms so that it may become a value. By devising such a technique, according to the present invention, it is possible to secure the tool rigidity while maintaining the tool cross-sectional thickness (t value) of the insert mounting portion in a thick state, and to make the Rr value positive. Cutting resistance can be reduced. Therefore, it is possible to provide a blade-cut-grooving blade type exchangeable rotary cutting tool with significantly improved breakage resistance in the reduced diameter portion.
On the other hand, as shown in FIG. 7, Conventional Example 3 is an insert with a constant thickness. Therefore, when trying to ensure the rigidity of the tool body, the Rr value becomes a negative value, and the cutting resistance is lower than that of a tool with a positive Rr value. It gets bigger. On the other hand, if the Rr value is set to a positive value, the t value cannot be set thick, and the rigidity of the tool body is lowered, so that breakage particularly occurs in the reduced diameter portion. Furthermore, the clearance angle of the cutting edge is increased, and the strength of the cutting edge is lowered. As shown in the sectional view of the minimum diameter portion of the reduced diameter portion of Conventional Example 3 in FIG. 7, the insert seat is formed by cutting perpendicular to the bottom surface contour shape of the insert 3. When the blade root groove is processed with the tool of Conventional Example 3 as described above, the blade is often broken from the reduced diameter portion. This is because fatigue failure occurs due to repeated loading due to cutting resistance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following Example.

The blade edge groove type rotary cutting tool for blade root groove machining of the present invention is such that the thickness of the insert attached to the tool is decreased from the outer peripheral side in the tool radial direction toward the inner peripheral side. The D1 value was 10 mm, the D2 value was 17 mm, the insert thickness T1 value of the tool enlarged diameter portion was 2.5 mm, and the T2 value was 1.5 mm. The tool body was made of hot die steel with a tensile strength of 1.29 GPa.
The method for creating the insert in Example 1 of the present invention was to form a cutting edge ridge line by machining a cemented carbide insert equivalent to JIS, P30 created using powder metallurgy technology. The number of inserts loaded in Invention Example 1 was one, the Rr value was set to 1 °, and the clearance angle was set to 15 °.
Here, the reason why the insert is created by machining is to satisfy the machining shape accuracy required at the time of intermediate finishing to finishing. For example, a method in which a breaker groove is provided on the upper surface of the insert in a state where the Rr value is a negative value to make the Rr value positive can be considered. Alternatively, there is a method of providing a breaker groove shape with a mold during press molding during insert manufacturing. However, these methods are difficult to satisfy the machining shape accuracy.
In addition, as the tools of Conventional Examples 3 and 4, a blade cutting groove exchanging cutting tool for blade root grooving with a flat insert having a constant insert thickness was used.

The rotary cutting tool created above was mounted on a vertical machining center and a cutting test was performed. At the time of the cutting test, assuming a medium finishing after rough machining, a work material that was previously subjected to a groove machining with a width of 9 mm and a depth of 12 mm using a roughing end mill was prepared. The evaluation evaluated the presence or absence of tool breakage when the cutting length was set to 15 m. When tool breakage occurred during the test, the cutting length at that time was taken as the evaluation value. Further, cutting resistance was measured with a cutting dynamometer (KISTLER 9257A).
Furthermore, the vibration of the chatter test and the chipping situation of the insert were also observed. The chatter vibration was determined according to the following criteria. The cutting state with a stable cutting sound but rough cutting surface compared to the stable cutting state was evaluated with the chatter vibration being small, the cutting state with a high-pitched sound in the middle, and the cutting state with a high-pitched sound and mechanical vibration as large.
Here, the following cutting conditions are approximately twice the cutting efficiency of a conventionally used high speed tool. Table 1 shows the used tool shape, insert shape, and experimental results.
(Cutting conditions)
Machining method: grooving using work material that has been pre-grooved, dry cutting work material: SCM440, hardness HB310
Spindle speed: 2250 min ^-1
Feed amount per blade: 0.01 mm / blade feed speed: 22 mm / mim
Axial depth of cut: 12.4 mm

From Table 1, Example 1 of the present invention showed a stable cutting state, and the insert with a cutting length of 15 m was in a normal wear state and could be continuously cut. This is because the reduced diameter portion of the tool has a groove-shaped insert seat so that the rigidity as a tool is maintained, and the insert thickness is gradually decreased from the outer peripheral side to the inner peripheral side to correct the Rr value. This is because the cutting resistance of Example 1 of the present invention was reduced by 39% from 900 N of Conventional Example 3 to 549 N.
On the other hand, in the case of Comparative Example 2, the experimental result showed that the cutting length was 15 m and minute chipping occurred in the insert, and the continuous use was impossible.
Conventional Example 3 had a constant thickness Rr value of −5 °, but had large chatter vibration and was broken at a cutting length of 3 m.
Conventional Example 4 is an insert having a constant thickness and an Rr value of 1 °. In Conventional Example 4, the t value of Invention Example 1 was 30% smaller. Although there was no chatter vibration, it was broken at a cutting length of 5 m. This is because the t value becomes too thin by making the Rr value a positive value with an insert having a constant thickness.
From these results, it was confirmed that the tool body was provided with a groove-shaped insert seat and the insert thickness was decreased from the tool outer peripheral side toward the inner peripheral side to make the Rr value a positive value. .

  The blade tip groove type rotary cutting tool for blade root groove processing according to the present invention is suitable for blade root groove processing from intermediate finishing to finishing, improving breakage resistance, reducing cutting resistance, and having high reliability. High blade root groove machining, particularly turbine blade root groove machining can be realized.

1: Tool body 2: Clamp screw 3: Insert 4: Expanded diameter part 5: Reduced diameter part 6: Groove-shaped insert seat D1: Tool diameter D2: Tool diameter T: Insert thickness t: Tool cross-sectional thickness of the insert mounting part Rr: Radial rake angle W: Groove width of groove-shaped insert seat L: Length of groove-shaped insert seat

Claims (2)

  The blade edge grooving rotary cutting tool for blade root grooving, in which a WC-base cemented carbide insert is detachably attached to the tip of the tool, the cutting edge ridge line of the insert from the tip of the rotary cutting tool to the axial rear end side And a reduced diameter portion where the tool diameter smoothly decreases from the enlarged diameter portion toward the rear end side in the axial direction. When the maximum value is D2 and the minimum value of the tool diameter in the reduced diameter portion is D1, the D1 value and the D2 value are in a relationship of D1 <D2, and the thickness of the insert is the rotational cutting tool. When the rake angle (degree) in the radial direction of the enlarged diameter portion is Rr, Rr> 0, and the rotary cutting tool has a groove-shaped insert seat. A blade-cutting-type rotary cutting tool for blade root groove machining.   The blade tip grooved cutting edge exchange type rotary cutting tool for blade root groove machining according to claim 1, wherein the blade tip grooved cutting edge exchange type rotary cutting tool is used for turbine blade blade root groove machining.

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