JP7236108B2 - Milling device and milling method - Google Patents

Description

The present disclosure relates to a cutting device and a cutting method.

Cutting of heat-resistant alloys such as Ni-based alloys and titanium alloys is generally performed using tools having inserts made of cemented carbide. Even in the case of milling, which is intermittent cutting, this cutting is performed in a low speed range of about 40 m/min.

On the other hand, there is an attempt to perform cutting at a high speed of 800 m/min using a ceramic insert that has higher heat resistance than cemented carbide, and its practical use has also begun (see Non-Patent Document 1).

Norikazu Suzuki, Risa Enmei, Yohei Hashimoto, Eiji Shamoto, and Yuki Hatano, “Tool failure Mechanism in High-Speed Milling of Inconel 718 by Use of Ceramic Tools”, International Journal of Automation Technology, Vol.8, No.6, PP 837-846, 2014

As described in Non-Patent Document 1, in high-speed cutting of a heat-resistant alloy using a ceramic insert, the insert is likely to break due to the brittleness of the ceramic. Therefore, stable cutting is difficult. Also, the life of the insert is shortened, requiring frequent tool changes.

Furthermore, when cutting is performed in a high speed range of 800 m/min or more by the conventional method, as shown in FIGS. In addition, FIG. 10A shows a cutting speed of 800 m / min, FIG. 10B shows a cutting speed of 1200 m / min, and FIG. 10C shows a cutting speed of 1500 m / min. This is the cutting edge of the insert after the

An object of one aspect of the present disclosure is to provide a cutting apparatus capable of cutting a heat-resistant alloy at high speed and stably.

One aspect of the present disclosure is a tool for cutting a heat resistant alloy work piece. The cutting tool has a ceramic insert. The vertical rake angle formed by the cutting speed vector of the insert and the straight line perpendicular to the cutting edge line and the rake face of the insert is -55° or more and -10° or less.

In cutting heat-resistant alloys using conventional cemented carbide inserts, it is desirable to make the vertical rake angle relatively large on the positive side. On the other hand, as a result of intensive studies, the inventors found that, when using a ceramic insert, chipping can be prevented by setting the vertical rake angle to −55° or more and −10° or less. The present disclosure has been reached.

That is, according to the configuration of the present disclosure, by setting the vertical rake angle of the insert to −55° or more and −10° or less, the heat-resistant alloy can be stably cut even in an ultra-high speed range of, for example, 1000 m/min or more. be able to.

In one aspect of the present disclosure, the heat-resistant alloy may be a Ni-based alloy or a titanium alloy. According to such a configuration, it is possible to achieve more stable cutting of a work material made of a Ni-based alloy or a titanium alloy in an ultra-high speed range.

In one aspect of the present disclosure, the insert may be generally cylindrical or generally conical and rotatably supported. According to such a configuration, since the contact point of the insert with the work material changes due to rotation, wear is dispersed. Therefore, the life of the insert can be extended.

Another aspect of the present disclosure is an apparatus for cutting a workpiece made of a heat resistant alloy. The cutting apparatus includes a cutting tool having a ceramic insert and a control that controls the relative cutting speed between the cutting tool and the work piece. Further, when the relative minimum cutting speed between the cutting tool and the work material at which the cutting point temperature becomes the melting point of the work material is defined as the reference cutting speed V (m/min), the control unit controls the cutting speed is 1.2 V (m/min) or more.

As a result of further intensive studies, the inventors have found that the cutting point temperature in cutting a heat-resistant alloy saturates when the cutting speed with a ceramic tool exceeds a certain level. Based on this discovery, the inventors predicted that the amount of wear of the insert would be reduced by increasing the cutting speed to a certain level or higher, and experimentally demonstrated this, leading to the present disclosure.

That is, according to the configuration of the present disclosure, by setting the cutting speed to 1.2·V (m/min) or more, it is possible to stably cut the heat-resistant alloy in a higher speed region than conventionally. In addition, the life of the insert can be extended by reducing the wear amount of the insert. The term "service life" as used herein refers to the cutting distance or the amount of work removed until the insert reaches a predetermined amount of wear or chipping, and does not refer to the cutting time.

Another aspect of the present disclosure is a method of cutting a workpiece made of a heat resistant alloy. A cutting method comprises cutting a workpiece with a cutting tool having a ceramic insert. In the step of cutting, the vertical rake angle formed by the cutting speed vector of the insert and the straight line orthogonal to the cutting edge line and the rake face of the insert is set to −55° or more and −10° or less.

According to such a configuration, by setting the vertical rake angle of the insert to −55° or more and −10° or less, it is possible to stably cut a heat-resistant alloy even in an ultra-high speed range of, for example, 1000 m/min or more. .

Another aspect of the present disclosure is a method of cutting a workpiece made of a heat resistant alloy. A cutting method comprises cutting a workpiece with a cutting tool having a ceramic insert. In the cutting process, when the relative minimum cutting speed between the cutting tool and the work material at which the cutting point temperature becomes the melting point of the work material is the reference cutting speed V (m / min), the cutting speed is 1.2·V (m/min) or more.

According to such a configuration, by setting the cutting speed to 1.2·V (m/min) or more, it is possible to stably cut the heat-resistant alloy in a higher speed range than conventionally. In addition, the life of the insert can be extended by reducing the wear amount of the insert.

It is a typical block diagram showing a cutting device of an embodiment. It is a typical perspective view showing a cutting tool of an embodiment. FIG. 4 is a schematic diagram for explaining a vertical rake angle in an insert; FIG. 4 is a schematic cross-sectional view taken along line AA of FIG. 3; 4 is a graph showing the relationship between cutting speed and cutting point temperature. 4 is a graph showing the relationship between the cutting speed and the ratio of the cutting point temperature to the melting point for various metals. 4 is a graph showing the relationship between vertical rake angle and removal volume in Examples. 4 is a graph showing the relationship between specific cutting resistance and cumulative tool travel distance in Examples. 9A is a photograph of the insert after cutting at 800 m/min, FIG. 9B is a photograph of the insert after cutting at 2000 m/min, and FIG. 9C is a photograph of the insert after cutting at 2400 m/min. . 10A is a photograph of the insert after cutting at 800 m/min in the prior art, FIG. 10B is a photograph of the insert after cutting at 1200 m/min in the prior art, and FIG. 10C is a photo of the insert after cutting at 1500 m/min in the prior art. It is a photograph of the insert after cutting with.

Embodiments to which the present disclosure is applied will be described below with reference to the drawings.
[1. First Embodiment]
[1-1. composition]
A cutting device 1 shown in FIG. 1 is a device for cutting a work material made of a heat-resistant alloy. The cutting device 1 includes a cutting tool 2 , a rotary power mechanism 3 , a cutting power mechanism 4 and a controller 5 .

<Rotational power mechanism>
The rotary power mechanism 3 is a power source that actively rotates the insert 21 of the cutting tool 2 by an electric motor or the like. If the insert 21 of the cutting tool 2 is driven to rotate, the rotary power mechanism 3 can be omitted.

<Cutting power mechanism>
The cutting power mechanism 4 is a mechanism that rotates and moves the entire cutting tool 2 relative to the work material.

For example, when cutting the peripheral surface of a columnar work material, the cutting power mechanism 4 cuts the cutting tool 2 in the radial direction of the work material (cutting motion), feeds it in the axial direction (feeding motion), Cutting (turning in this case) is performed by rotating the work material around its central axis at high speed (cutting motion). The cutting power mechanism 4 may rotate and move only the cutting tool 2, or may rotate and move only the work material.

Examples of the heat-resistant alloy used for the work material include Ni-based alloys, titanium alloys, Co-based alloys, etc. Ni-based alloys and titanium alloys are preferred.

Ni-based alloys used as work materials include Ni--Cu alloys, Ni--Mo alloys, Ni--Cr--Fe alloys, Ni--Cr--Mo alloys, Ni--Cr--Mo--Cu alloys, Ni--Fe--Cr An alloy etc. are illustrated. Specific examples include Inconel (registered trademark) and Hastelloy (registered trademark).

Examples of titanium alloys used for the work material include Ti--Pd alloys, Ti--Ta alloys, Ti--Al alloys, Ti--6Al-4V alloys, and the like defined in JIS-H4600 (2012). Co-based alloys used for the work material include Co--Cr--Ni alloys, Co--Cr--Mo alloys, and the like.

<Cutting tool>
A cutting tool 2 shown in FIG. 2 is a tool for cutting a work material made of a heat-resistant alloy. The cutting tool 2 includes an insert 21 , a bolt 22 , a rotating body 23 and a tool body 24 .

(insert)
The insert 21 is made of ceramic.
Specific examples of the ceramic constituting the insert 21 include sialon-based ceramic, alumina-based ceramic, silicon nitride-based ceramic, whisker-based ceramic, and the like.

In this embodiment, as shown in FIG. 2, the insert 21 is generally cylindrical or generally conical. Also, the insert 21 is supported by the rotating body 23 and the tool body 24 so as to be rotatable passively or actively about the center axis of the cylinder or cone. It should be noted that the term "substantially cylindrical" is a concept that includes not only a perfect cylinder whose peripheral surface is parallel to the central axis, but also a shape whose peripheral surface is inclined with respect to the central axis. Accordingly, a substantially cylindrical or substantially conical shape means a shape having a circular edge (that is, a cutting edge ridge). In addition, as an example of the substantially columnar shape, a round top shape can be mentioned.

The cutting tool 2 is a rotary tool that cuts a work material while an insert 21 rotates. The cutting tool 2 cuts a work material by rotating and moving the cutting tool 2 itself relative to the work material.

(bolt)
A bolt 22 passes through the center of the insert 21 . The insert 21 is fixed to the rotating body 23 by screwing the bolt 22 to the rotating body 23 .

(Rotating body)
The rotating body 23 is a columnar body with the insert 21 attached to its tip. The rotating body 23 is rotatably supported by the bearing portion of the tool body 24 .

(tool body)
The tool body 24 has bearings. A rotating body 23 having an insert 21 attached thereto is inserted into this bearing portion. The type of bearing is not limited, and sliding bearings, rolling bearings, and the like can be used.

(Vertical rake angle at insert)
The vertical rake angle α of the insert 21 in the cutting tool 2 of FIG. 2 will be described with reference to FIG.

The vertical rake angle α is, as shown in FIG. FIG. 3 is a diagram for explaining the vertical rake angle α in general cutting, and the insert 21 shown in FIG. 3 has a different shape from the insert 21 of this embodiment.

The “rake face” is a face that scoops up chips T at the front of the insert 21 in the advancing direction. Further, the straight line z perpendicular to the cutting speed vector C and the cutting edge ridge line y is the finished surface S1 (that is, the surface of the work W through which the insert 21 passes, and the work after the work W is cut off. parallel to the normal N of the plane). Note that C in FIG. 4 indicates the component of the cutting speed vector C in FIG. 3 in the AA line direction.

A flank face S4 in FIG. 4 is a face provided so that the work material W through which the insert 21 has passed does not come into contact with the insert 21. As shown in FIG. The workpiece W comes into slight contact with the flank face S4 due to recovery of elastic deformation occurring in the cutting area of the workpiece W. As shown in FIG.

Here, as shown in FIG. 4, the vertical rake angle α of the insert 21 in this embodiment is designed to be larger on the negative side than in the conventional case.

The vertical rake angle α is positive when the rake face S2 is on the side of the wear region R1 facing the cutting speed vector C (that is, on the side opposite to the direction of movement of the insert), and the rake face S2 has a cutting speed higher than the wear region R1. It is negative when it is on the side opposite to the direction of the vector C (that is, on the direction in which the insert advances), and is 0 when the rake face S2 is parallel to the straight line z.

As shown in FIG. 4 , chipping of the insert 21 during high-speed cutting of a heat-resistant alloy is caused by crack propagation generally parallel to the rake face S2 and grows along the direction D. As shown in FIG. This crack occurs after the cutting edge abutting the shear region R2 wears in the wear region R1.

On the other hand, the inventors apply fracture mechanics to the cutting edge shape outside the wear region R1, and by making the rake face S3 indicated by the broken line in FIG. It has been found that chipping of the insert 21 is prevented. The new rake face S3 has a vertical rake angle α of -55° or more and -10° or less.

The lower limit of the vertical rake angle α is more preferably −45°, more preferably −35°. On the other hand, the upper limit of the vertical rake angle α is more preferably −20°, more preferably −25°. If the vertical rake angle α is less than -55°, it may be difficult to discharge chips. Moreover, cutting power increases, and there is a possibility that machining accuracy may decrease. Conversely, if the vertical rake angle α is greater than −10° (that is, the vertical rake angle α approaches the positive side), chipping of the insert 21 is likely to occur during high-speed cutting as in the conventional art.

<Control section>
The control unit 5 controls the relative cutting speed between the cutting tool 2 and the work material. Specifically, the control unit 5 controls the rotation speed of the rotary power mechanism 3, the cutting speed of the cutting tool 2 by the cutting power mechanism 4, and the like. The control unit 5 is composed of, for example, a microcomputer having an input/output unit.

(cutting speed)
FIG. 5 shows the result of milling Inconel (registered trademark) 718 by fixing a 12.7 mm diameter sialon insert 21 to a milling cutter body and rotating the body. In FIG. 5, f is the tool feed, Rd is the radial depth of cut, and Ad is the axial depth of cut.

As shown in FIG. 5, increasing the cutting speed between the cutting tool 2 and the work material also increases the cutting point temperature. When the relative minimum cutting speed between the cutting tool 2 and the work material at which this cutting point temperature becomes the melting point of the work material is defined as a reference cutting speed V (m/min), the control unit 5 performs cutting The cutting speed between the tool 2 and the work material is controlled to 1.2·V (m/min) or more.

Here, in the present disclosure, "cutting point temperature" means the highest temperature on the surface of the insert 21 that is in contact with the work material. The cutting point temperature can be measured, for example, using a thermometer using infrared radiation.

The inventors of the present invention have found that when the cutting speed is increased, the temperature of the cutting point reaches saturation at a certain point, and after that, it hardly increases. The reason why the cutting point temperature is saturated is thought to be that the cutting point temperature approaches the melting point of the work material.

FIG. 6 shows the result of turning by fixing the alumina insert to the tool body and rotating the work material. The machining conditions for this turning are 0.15 mm radial depth of cut, 0.15 mm/rev tool feed, and dry (ie, no cutting fluid).

As shown in FIG. 6, the above-mentioned phenomenon of saturation of the cutting point temperature is not observed in metals with good machinability such as iron-based materials, aluminum or aluminum alloys, copper or copper alloys, even at high cutting speeds. . On the other hand, heat-resistant alloys such as Ni-based alloys and titanium alloys have low thermal conductivity, relatively high material strength, and large cutting resistance (that is, cutting force). In addition to these conditions, the use of a ceramic with low thermal conductivity and high heat resistance as the insert is the reason why the phenomenon of saturation of the cutting point temperature, as shown in Fig. 6, was observed for the first time.

It is known that insert wear in high speed cutting increases due to atomic diffusion phenomena and chemical reactions. This diffusion phenomenon and chemical reaction increases exponentially with increasing temperature.

However, as shown in FIGS. 5 and 6, when ceramic inserts are used for heat-resistant alloys such as Ni-based alloys and titanium alloys, the cutting point temperature saturates during high-speed cutting as described above, and the cutting speed decreases. Even if it rises, the increase of the diffusion phenomenon and the chemical reaction can be suppressed. That is, even if the cutting speed is increased when the cutting point temperature is saturated, temperature-dependent diffusion phenomena and chemical reactions do not change significantly.

Therefore, in high-speed cutting where the cutting point temperature is saturated, the progress of insert wear is dominated by the cutting time during which the insert is in contact with the work material at the saturated temperature. When the cutting speed is increased, the cutting distance, that is, the amount of material removed increases for the same cutting time. That is, the amount of insert wear is reduced for the same amount of material removed. This results in longer insert life.

The present disclosure sets the cutting speed of the cutting tool 2 to 1.2·V (m/min) or higher based on knowledge based on the results of FIGS. 5 and 6 . The lower limit of the cutting speed is preferably 1.5·V (m/min), more preferably 2.0·V (m/min). On the other hand, although the upper limit of the cutting speed is not particularly limited, it is, for example, 10·V (m/min).

A specific cutting speed is, for example, 1200 m/min or more, more preferably 1500 m/min, and even more preferably 2000 m/min, in the case of milling without using a rotary tool. In addition, in the rotating insert 21 in this embodiment, when the cutting tool 2 is a rotary tool, a relative cutting speed in consideration of the rotational movement of the insert 21 may be the above cutting speed.

Further, it is known that in the case of a rotary tool in which the rotation of the insert 21 is driven, the relative speed between the insert 21 and the work material decreases. Therefore, in the driven type rotary tool, it is preferable to control the cutting power mechanism 4 in consideration of the decrease in the relative speed.

Note that the control unit 5 may be configured to be able to control the vertical rake angle α of the insert 21 of the cutting tool 2 . The vertical rake angle α can be controlled, for example, by changing the orientation of the cutting tool 2 or the orientation of the work material.

[1-2. Cutting method]
Next, a cutting method using the cutting device 1 will be described.
The cutting method of the present disclosure includes a step of cutting a work material with a cutting tool 2 .

<Cutting process>
In this step, the work material is cut while controlling the vertical rake angle α of the insert 21 to be −55° or more and −10° or less. A more preferable range of the vertical rake angle α is as described above. The vertical rake angle α may be controlled by the shape of the tool body 24, by the controller 5, or by other methods.

Moreover, in this step, the cutting speed of the cutting tool 2 is set to 1.2·V (m/min) or higher. A more preferable range of cutting speed is as described above. The cutting speed is controlled by the controller 5 .

[1-3. effect]
According to the embodiment detailed above, the following effects are obtained.
(1a) By setting the vertical rake angle α of the insert 21 to −55° or more and −10° or less, heat-resistant alloys such as Ni-based alloys and titanium alloys can be stably cut even at ultra-high speeds of 1000 m/min or more. can do.

(1b) Wear of the insert 21 is dispersed by rotating the insert 21 . Therefore, the life of the insert 21 can be extended.

(1c) By setting the cutting speed to 1.2·V (m/min) or higher, it is possible to stably cut heat-resistant alloys such as Ni-based alloys and titanium alloys in a higher speed range than conventional cutting speeds. Also, the life of the insert 21 can be extended by reducing the amount of wear of the insert 21 .

[2. Other embodiments]
Although the embodiments of the present disclosure have been described above, it is needless to say that the present disclosure is not limited to the above embodiments and can take various forms.

(2a) In the cutting device 1 of the above embodiment, the configuration of the cutting tool 2 is an example. In other words, the shape of each member (bolt 22, rotating body 23, tool body 24, etc.) constituting the cutting tool 2 can be changed as appropriate.

(2b) In the cutting tool 2 of the above embodiment, the insert does not necessarily have to be rotatably supported passively or actively. Also, the shape of the insert is not particularly limited. Therefore, the cutting tool 2 may be, for example, a cutting tool with a fixed insert.

(2c) In the cutting apparatus 1 of the above embodiment, when the vertical rake angle α of the insert 21 is −55° or more and −10° or less, the cutting speed must be 1.2 V (m/min) or more. No need.

(2d) Conversely, in the cutting device 1 of the above embodiment, when the cutting speed of the cutting tool 2 is set to 1.2 V (m/min) or higher, the vertical rake angle α of the insert 21 must be -55°. It is not necessary to set the angle above -10° or below.

(2e) The function of one component in the above embodiments may be distributed as multiple components, or the functions of multiple components may be integrated into one component. Also, part of the configuration of the above embodiment may be omitted. Also, at least a part of the configuration of the above embodiment may be added, replaced, etc. with respect to the configuration of the other above embodiment. It should be noted that all aspects included in the technical idea specified by the wording in the claims are embodiments of the present disclosure.

[4. Example]
A plurality of tests conducted to confirm the effects of the present disclosure and their results will be described below.

(Test 1)
Multiple cuts were made while varying the vertical rake angle on the insert and the volume of material removed by each cut was measured. Inconel (registered trademark) 718 was used as the material. In addition, as cutting equipment, Okuma's machining center "MILLAC (registered trademark) 415V" and DMG Mori Seiki's machining center "NV5000" are equipped with NGK SPARK PLUG CO., LTD.'s "SX7" (SiAlON ceramic) as inserts. A cutting tool equipped with a cutting tool was used. The machining center is an apparatus including the cutting power mechanism 4 and the control unit 5 shown in FIG. This result is shown in FIG. In addition, cutting was performed by milling.

In FIG. 7 , the white circles indicate the cases where MILLAC (registered trademark) 415V was used without leading to tool breakage, and the black circles indicate the cases where NV5000 was used and did not lead to tool breakage. Further, thin cross marks are caused by chipping on the rake face using MILLAC (registered trademark) 415V, and thick cross marks are by chipping on the rake face using NV5000. Those with defects indicate the removed volume at the time when the defect occurred. In addition, those that did not lead to chipping can be further processed from the plotted removed volume.

The horizontal axis of the graph in FIG. 7 represents the taper angle of the cutting edge of the insert, and the angle is 0° if not shown. The cutter body to which the insert is fixed holds the insert such that the vertical rake angle is reduced by 7°. Therefore, when the taper angle of the insert is 0°, the vertical rake angle is -7°, when it is 20°, the vertical rake angle is -27°, and when it is 45°, the vertical rake angle is -52°.

As can be seen from FIG. 7, with the conventional tool, tool breakage occurs at a material removal volume of about 10 cc to 20 cc. On the other hand, the tools with vertical rake angles of −52° and −27° did not cause chipping even when the volume of material removed was about 35 cc, indicating that machining could be continued.

FIG. 8 shows the relationship between the specific cutting resistance (proportional coefficient between cutting cross-sectional area and cutting force) measured in the above test and the cumulative tool movement distance. As shown in FIG. 8, the tool with a vertical rake angle of −52° (that is, a taper angle of 45°) had a higher initial cutting power than the other tools. Therefore, if the vertical rake angle is further reduced, it is predicted that the cutting power will become excessive and the machining accuracy will decrease.

(Test 2)
A plurality of cuts were performed on Inconel (registered trademark) while changing the cutting speed using the same insert, and the change in wear of the insert after each cut was confirmed. The results are shown in FIGS. 9A, 9B and 9C. Cutting was performed by intermittent turning simulating milling.

FIG. 9A shows the state of the cutting edge of the insert after removing 48 cc of material at a cutting speed of 800 m/min. Similarly, FIG. 9B shows the state of the cutting edge of the insert after removing 45 cc of material at a cutting speed of 2000 m/min and FIG. 9C after removing 45 cc of material at a cutting speed of 2400 m/min.

From these photographs, it can be seen that cutting at high speeds of 2000 m/min and 2400 m/min, which are higher than 800 m/min, did not increase the wear of the insert, but conversely reduced the wear.

The melting point of Inconel (registered trademark) 718 is from 1,260° C. to 1,336° C. With the cutting tool of this test, the cutting point temperature reaches the melting point at a cutting speed of about 1000 m/min. That is, the standard cutting speed V of this test is 1000 m/min. Therefore, from the results of this test, by setting the cutting speed to 1.2 V = 1200 m/min or more, it is possible to stably cut work materials made of heat-resistant alloys such as Ni-based alloys and titanium alloys. It was shown that the amount of wear of the insert was reduced while the amount of wear of the insert was reduced.

DESCRIPTION OF SYMBOLS 1... Cutting device, 2... Cutting tool, 3... Rotary power mechanism, 4... Cutting power mechanism, 5... Control part,
21... Insert, 22... Bolt, 23... Rotating body, 24... Tool body.

Claims (2)

A device for milling a work material made of a heat-resistant alloy,
a cutting tool having a ceramic insert;
a control unit that controls the relative cutting speed between the cutting tool and the work material;
with
The control unit sets a vertical rake angle formed by a straight line perpendicular to the cutting speed vector and the cutting edge ridgeline of the insert and the rake face of the insert to -55° or more and -27° or less,
When the relative minimum cutting speed between the cutting tool and the work material at which the cutting point temperature becomes the melting point of the work material is defined as a reference cutting speed V (m/min), the control unit: A milling apparatus, wherein the cutting speed is set to 1.2·V (m/min) or more using the reference cutting speed V recorded in advance . A method of milling a work material made of a heat-resistant alloy, comprising:
cutting the work material with a cutting tool having a ceramic insert;
In the cutting step, the vertical rake angle formed by the cutting speed vector of the insert and a straight line orthogonal to the cutting edge ridge line and the rake face of the insert is set to -55 ° or more and -27 ° or less, and the cutting point temperature is the melting point of the work material, and the relative minimum cutting speed between the cutting tool and the work material is the reference cutting speed V (m / min), the reference cutting speed recorded in advance A milling method, wherein V is used to set a relative cutting speed between the cutting tool and the work material to 1.2·V (m/min) or more.

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