JP2010227988A - Method and apparatus for expansion forming of steel pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for expansion forming of steel pipe, which can carry out expansion forming with superb efficiency and yield, while preventing occurrence of buckling and cracking and the like, in the expansion forming of steel pipe to perform expansion forming in multiple steps. <P>SOLUTION: A main cylinder 11 is driven so as to insert a punch 12a into an open end of a round steel pipe P held by clamp devices 25, 26. In the steps, a side die 21 to press the open end of the round pipe P is not driven while the punch 12a is being moved. Then, following the insertion process of the punch 12b, the side die 21 is contacted to the open end of expanding part of the round pipe P, and pressed in the same direction with the insertion direction of the punch 12b. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a steel pipe expansion molding method and a pipe expansion molding apparatus that perform pipe expansion molding by inserting a punch into an end opening of a steel pipe.

In recent years, a method has been used in which a punch is inserted into one open end of a steel pipe to form a portion that has been expanded and formed at the end of the steel pipe.
For example, Patent Document 1 discloses a method of manufacturing a metal cylinder that performs tube expansion forming step by step using a plurality of diameter expansion punches.

However, the conventional steel pipe expansion forming method has the following problems.
That is, in the method for expanding and forming a steel pipe disclosed in the above publication, buckling, cracking, and thinning may occur if the tube expansion speed is not appropriately controlled when expanding in stages using a plurality of diameter expansion punches. May occur.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a steel pipe expansion molding method capable of efficiently performing a pipe expansion molding with a good yield while preventing the occurrence of buckling, cracking, etc. And it is providing a pipe expansion molding apparatus.

  A steel pipe expansion forming method according to a first aspect of the present invention is a steel pipe expansion forming method in which a plurality of punches having different sizes are inserted into an end opening of a steel pipe to perform pipe expansion forming in multiple stages. A step and a second tube expansion forming step. The first tube forming step inserts the smallest first punch among the plurality of punches into the steel pipe and does not press the end of the steel pipe. In the second pipe expansion forming step, a second punch larger than the first punch is inserted into the steel pipe, and the end of the steel pipe is pressed in the insertion direction of the second punch using a side mold.

Here, in the steel pipe tube forming method in which a plurality of punches of different sizes are inserted from the end opening of the steel tube and the tube is formed in multiple stages, the smallest punch (first punch) corresponding to the first tube expansion forming step is used. At the time of pipe expansion molding, unlike the subsequent second pipe expansion molding step or the like, only the punch is inserted without pressing the end of the steel pipe with the side mold.
That is, when performing pipe expansion molding in a plurality of stages using a plurality of punches, only the first punch is inserted into the end opening of the steel pipe without using a side mold in the first pipe expansion molding step. In the subsequent tube expansion forming step, the end portion of the steel pipe using the side mold is pressed at a predetermined timing in parallel with the insertion of the punch.

Here, the tube expansion forming step described above may include the first and second tube expansion forming steps, and the tube expansion forming may be performed in two stages, or the tube expansion forming may be performed in three or more stages. Good.
Thereby, by pressing the steel pipe end using an effective side mold in order to prevent the occurrence of buckling or cracking at the time of pipe expansion molding, omitting it in the first pipe expansion molding step and minimizing it, The molding speed at the time of pipe expansion molding can be increased. Further, it is possible to avoid the occurrence of buckling or the like in the steel pipe due to excessive pressing on the end portion of the steel pipe by the side mold. As a result, high-quality pipe expansion molding with high yield and high yield can be performed by performing pipe expansion molding in multiple stages using a side mold and a plurality of punches in combination as much as necessary.

The steel pipe expansion forming method according to the second invention is a steel pipe expansion forming method according to the first invention, wherein the first punch has the largest expansion ratio among a plurality of punches.
Here, the first punch that is inserted first into the end opening of the steel pipe is set to have a larger pipe expansion ratio than the other punches.
Here, the said pipe expansion rate means the expansion rate of the outer diameter of the steel pipe after the pipe expansion forming step with respect to the outer diameter of the steel pipe before each pipe expansion forming step.
Thereby, a moldability can be improved safely and efficiently by using a punch with the largest pipe expansion ratio in the first step with the least thickness reduction by the pipe expansion molding.

A steel pipe expansion forming method according to a third invention is a steel pipe expansion forming method according to the first or second invention, wherein the steel pipe is a round steel pipe having a substantially circular cross section.
Here, the above-described multi-stage pipe expansion molding is performed on the round steel pipe. Here, the said round steel pipe means the steel pipe which has a substantially circular cross-sectional shape.
Thereby, a pipe expansion molding part can be efficiently formed in the edge part of a round steel pipe.

The steel pipe expansion forming method according to the fourth invention is a steel pipe expansion forming method according to any one of the first to third inventions, and is larger than the second punch after the second pipe expansion forming step. A third tube expansion forming step for inserting the third punch into the steel tube is further provided.
Here, tube expansion molding is performed in three stages using three punches having different sizes.
As a result, even when performing multi-stage tube expansion forming, the tube expansion portion can be formed at the end portion of the steel pipe by an efficient method, with minimal steps, which are unlikely to cause buckling or cracking.

  The steel pipe expansion forming method according to the fifth invention is a steel pipe expansion forming method according to the fourth invention, and in the third pipe expansion forming step, a side mold is used as in the second pipe expansion forming step. Press the end of the steel pipe.

Here, in the method of performing the pipe expansion molding in the three stages described above, in the second and third pipe expansion molding steps, excluding the first first pipe expansion molding step, the punch is inserted and the steel pipe end portion using the side mold is used. Press.
Thus, the first pipe expansion forming step in which the thinning is unlikely to occur is not performed on the steel pipe end portion, and the second and third pipe expansion forming steps are pressed to the steel pipe end portion efficiently. Tube forming with high moldability can be performed.

  A pipe expansion molding apparatus according to a sixth invention is a pipe expansion molding apparatus for performing pipe expansion molding in multiple stages by inserting a plurality of punches having different sizes into an end opening of a steel pipe, the plurality of punches and a side mold. And a control unit. The side mold presses the end of the steel pipe in the punch insertion direction. The control unit does not use the side mold in the first first expansion forming step of inserting the smallest punch among the plurality of punches into the end opening of the steel pipe, and the punch and the side mold in the subsequent tube expansion forming step. Control is performed so that pipe expansion molding is performed in combination.

Here, in the tube expansion molding apparatus that performs tube expansion molding in multiple stages while inserting a plurality of punches having different sizes from the end opening of the steel pipe, at the time of tube expansion molding using the smallest punch that corresponds to the first tube expansion molding step, Unlike the tube expansion forming step or the like, only the punch is inserted without pressing the end of the steel tube with the side mold.
That is, when pipe expansion molding is performed in a plurality of stages using a plurality of punches, only the punch is inserted into the end opening of the steel pipe without using a side mold in the first pipe expansion molding step. In the subsequent tube expansion forming step, the end portion of the steel pipe using the side mold is pressed at a predetermined timing in parallel with the insertion of the punch.

Here, the above-described tube expansion forming step may be performed in two stages, or may be performed in three or more stages.
By this, by pressing the steel pipe end using the effective side mold to prevent the occurrence of buckling, cracking, etc. during pipe expansion molding, omit it in the first pipe expansion molding step and minimize it. The molding speed at the time of pipe expansion molding can be increased. Further, it is possible to avoid the occurrence of buckling or the like in the steel pipe due to excessive pressing on the end portion of the steel pipe by the side mold. As a result, high-quality pipe expansion molding with high yield and high yield can be performed by performing pipe expansion molding in multiple stages using a side mold and a plurality of punches in combination as much as necessary.

  According to the method for expanding and forming a steel pipe according to the present invention, a high-quality tube-expanding method having a high yield and a high yield is achieved by performing tube-expanding molding in multiple stages using a side mold and a plurality of punches in combination as much as possible. Can be implemented.

1 is an overall view showing a configuration of a pipe expansion molding apparatus according to an embodiment of the present invention. Explanatory drawing which shows performing a pipe expansion molding by inserting a punch in multiple steps in the pipe expansion molding apparatus of FIG. (A)-(c) is a side view which respectively shows the working state of the punch in the 1st-3rd step, and a side metal mold | die. (A)-(c) is a graph which shows the relationship with the displacement amount of the main cylinder with respect to the elapsed time corresponding to each step of FIG. The flowchart which shows the flow of the pipe expansion molding method of the round steel pipe by the pipe expansion molding apparatus of FIG. Sectional drawing which shows the structure of the round steel pipe after pipe expansion forming. The graph which shows the plate | board thickness of each part corresponding to the round steel pipe of FIG. The graph which shows the board thickness fluctuation | variation of the round steel pipe in each step of 1-3.

A steel pipe expansion forming method and a pipe expansion forming apparatus according to an embodiment of the present invention will be described below with reference to FIGS.
[Configuration of Tube Expansion Apparatus 10]
The tube expansion forming apparatus 10 according to the present embodiment is an apparatus that inserts a plurality of punches 12 having different sizes into a round steel pipe P and performs tube expansion forming in multiple stages. As shown in FIG. 1, the pipe expansion molding apparatus 10 includes a main cylinder 11, a pipe 12 for pipe expansion molding, a side pressure device 15 including a side mold 21 and a side cylinder 22, a control unit 20, Outer pressurizing devices 23 and 24, clamping devices 25 and 26, and a positioning portion 27 are provided.

The round steel pipe P is a pipe material having a substantially circular cross-sectional shape.
The main cylinder 11 is connected to the hydraulic pump 16, and applies a pressing force for inserting the punch 12 to the round steel pipe P fixedly arranged by the hydraulic oil supplied from the hydraulic pump 16.
As shown in FIG. 2, the punch 12 is a member that is inserted from the open end of the round steel pipe P to form the expanded portion P <b> 1 (see FIG. 6) at the end of the round steel pipe P. Moreover, in this embodiment, as shown in FIG. 2 and FIG. 3 (a)-FIG.3 (c), three types of punches 12a-12c from which a magnitude | size differs in order are passed through three steps, The expanded pipe portion P1 is formed at the end of the round steel pipe P.

  Here, among the three types of punches 12a to 12c, the smallest punch 12a used in the first first step is set to have the largest tube expansion ratio among the three types of punches 12a to 12c. Yes. Thus, by setting the maximum tube expansion rate in the first first step in which the thinning is most unlikely to occur, the tube expansion can be efficiently performed without causing a sudden thinning or molding failure.

Note that the pipe expansion rate is, for example, the outer diameter d1 of the round steel pipe P before each step in the first to third steps and the outer diameter d2 of the round steel pipe P after each step. Represented by 1).
Tube expansion rate α = (d2−d1) / d1 (1)
That is, the pipe expansion rate means how much the outer diameter dimension of the round steel pipe P is expanded by the insertion of the punch 12 with respect to the outer diameter dimension before the punch 12 is inserted.

  The side pressurization device 15 is a mechanism that applies a pressing force in the same direction as the insertion direction of the punch 12 to one open end of the round steel pipe P that is an object of pipe expansion molding. And the side pressurization apparatus 15 has the side metal mold | die 21 and the side cylinder 22, as shown in FIG. The side mold 21 is a substantially annular member, and a plurality of sizes are provided according to the size of the punch 12 described above (side molds 21b and 21c to be described later). It arrange | positions so that it may move in the cyclic | annular inner peripheral part, it contact | abuts to the opening edge part of the round steel pipe P by which pipe expansion molding was carried out, and axially pushes it in the same direction as the insertion direction of the punch 12. FIG. The side cylinder 22 presses the side mold 21 attached to the tip of the movable part in the direction in which the punch 12 is inserted. Further, the side cylinder 22 is controlled by the control unit 20 so that an appropriate pressing force is applied toward the open end of the round steel pipe P based on the stroke and speed when the punch 12 in the main cylinder 11 is advanced. Feed forward controlled.

  As described above, the control unit 20 moves the side die 21 by the side pressurizing device 15 toward the round steel pipe P with the optimum pressing force based on the information on the stroke and speed at which the punch 12 in the main cylinder 11 is advanced. The hydraulic pump 16 that supplies hydraulic oil to the side cylinder 22 is controlled so as to move forward. In addition, as shown in FIGS. 3A to 3C, the control unit 20 performs a step (first step) in which only the punch 12a is inserted in the process of expanding the tube in three stages, a punch 12b, In the step (second and third steps) in which the punch 12c and the side mold 21 are used in combination, the punches 12a to 12c and the side mold 21 are controlled. The contents of such pipe expansion molding will be described in detail later.

  The outer mold pressure devices 23 and 24 are arranged so as to sandwich the peripheral portion of the expanded portion P1 of the round steel pipe P from above and below, respectively, the outer mold portions 23a and 24a, the outer mold cylinders 23b and 24b, have. The outer mold portions 23a and 24a have a constant size until the end of molding, and are tapered in the vicinity of the contact portion with the round steel pipe P along the shape of the tip portion of the punch 12 inserted into the round steel pipe P. It has a shape and abuts against the outer peripheral surface of the round steel pipe P. Thereby, the periphery of the expanded part P1 into which the punch 12 is inserted and expanded and formed is supported from the outer peripheral surface side, and the formability can be improved. The outer mold cylinders 23 b and 24 b are connected to the hydraulic pump 16, and the outer mold parts 23 a and 24 a are moved with respect to the outer peripheral part of the expanded part P 1 of the round steel pipe P in accordance with the movement of the punch 12 and the side mold 21. Move to a close position.

The clamp devices 25 and 26 support the round steel pipe P so as to sandwich the outer peripheral portion in the vicinity of the substantially central portion in the longitudinal direction of the round steel pipe P from above and below. The clamp devices 25 and 26 have clamp dies 25a and 26a and clamp cylinders 25b and 26b, respectively. The clamp dies 25 a and 26 a are in contact with and supported by the outer peripheral surface of the round steel pipe P when the round steel pipe P is set in the pipe expansion molding apparatus 10. The clamp cylinders 25 b and 26 b are connected to the hydraulic pump 16 and move the clamp dies 25 a and 26 a in a direction orthogonal to the longitudinal direction of the round steel pipe P.
When the round steel pipe P is set in the pipe expansion molding apparatus 10, the positioning part 27 contacts the end of the round steel pipe P opposite to the side where the pipe expansion molding is performed, and performs positioning in the longitudinal direction.

<Flow of tube expansion forming by the tube expansion forming apparatus 10>
In the present embodiment, in the tube expansion molding apparatus 10 having the above-described configuration, as shown in FIGS. 3 (a) to 3 (c) and FIGS. 4 (a) to 4 (c), 3 different in size. The round steel pipe P is expanded in a stepwise manner using three types of punches 12a to 12c. In the present embodiment, by performing the pipe expansion molding in a plurality of stages as described above, the molding load on the round steel pipe P is reduced and the molding limit is improved.

Specifically, in the present embodiment, the round steel pipe P is expanded according to the following procedure according to the flowchart shown in FIG.
That is, in the tube expansion forming apparatus 10 of the present embodiment, in step S1 (first tube expansion forming step), as shown in FIG. 3 (a), the opening end portion of the round steel pipe P supported by the clamp devices 25 and 26 is provided. On the other hand, the main cylinder 11 is driven so that the punch 12a (punch A) having the smallest pipe expansion rate among the punches 12a to 12c is inserted. Here, in this step S1, the side mold 21 that presses the open end of the round steel pipe P is not driven during the process of moving the punch 12a. At this time, the stroke amount and the molding pressure of the main cylinder 11 for driving the punch 12a are set such that the punch 12a is inserted into the round steel pipe P as shown in FIG. As the part begins to form, the molding pressure rises in steps.

Next, in step S2, it is confirmed whether or not the first step has been completed. The end of the first step may be determined by detecting that the main cylinder 11 that drives the punch 12a has reached a predetermined stroke amount or the like.
Next, in step S3, the punch 12a is taken out from the open end of the round steel pipe P.
Next, in step S4 (second pipe expansion molding step), as shown in FIG. 3 (b), from the opening end of the pipe expansion portion formed at the end of the round steel pipe P by the punch 12a in the first step, A punch 12b that is larger than the punch 12a and has a smaller tube expansion rate is inserted.

Next, in step S5 (second tube expansion forming step), a side metal corresponding to the size of the punch 12b is formed with respect to the opening end of the expanded portion of the round steel pipe P in accordance with the process of inserting the punch 12b. The die 21b is brought into contact and pressed in the same direction as the insertion direction of the punch 12b.
At this time, the punch 12b, the main cylinder 11 that drives the side mold 21b, and the stroke amount and the molding pressure of the side cylinder 22 are inserted into the round steel pipe P as shown in FIG. Almost simultaneously with this, pressing to the opening end by the side mold 21b is started. And if a straight part begins to be formed in the expansion part of the round steel pipe P, the molding pressure concerning the punch 12b will rise in steps.

Next, in step S6, it is confirmed whether or not the second step has been completed. Note that the end of the second step may be determined by detecting that the main cylinder 11 that drives the punch 12b has reached a predetermined stroke amount, as in step S2.
Next, in step S7, the punch 12b is taken out from the open end of the round steel pipe P.
Next, in step S8 (third pipe expansion molding step), as shown in FIG. 3C, from the opening end of the pipe expansion portion formed at the end of the round steel pipe P by the punch 12b in the second step, A punch 12c larger than the punch 12b is inserted.

Next, in step S9 (third pipe expansion forming step), in accordance with the process of inserting the punch 12c, the side metal corresponding to the size of the punch 12c with respect to the opening end of the pipe expansion portion of the round steel pipe P is used. The mold 21c is brought into contact with and pressed in the same direction as the insertion direction of the punch 12c.
At this time, the punch 12c, the main cylinder 11 that drives the side mold 21c, and the stroke amount and the molding pressure of the side cylinder 22 are inserted into the round steel pipe P as shown in FIG. Almost simultaneously with this, the pressing to the opening end by the side mold 21c is started. And if a straight part begins to be formed in the expanded part of the round steel pipe P, the molding pressure concerning the punch 12c will rise in steps.

Next, in step S10, it is confirmed whether or not the third step is completed. Note that the end of the third step may be determined by detecting that the main cylinder 11 that drives the punch 12c has reached a predetermined stroke amount or the like, similar to the end of the first and second steps. .
Next, in step S11, the punch 12c is taken out from the open end of the round steel pipe P.
Next, in step S12, the side mold 21c, the outer mold parts 23a and 24a, etc. are retracted, the support by the clamping devices 25 and 26 is released, and the round steel pipe P in which the expanded pipe part P1 is formed at the opening end part. Take out.

  Here, as shown in FIG. 6, the round steel pipe P for which the above-described three-stage pipe expansion molding has been completed is classified into the straight part, the taper part, and the raw pipe part in order from the opening end part side subjected to the pipe expansion molding. Is done. In addition, the pipe expansion part P1 means a straight part including a parallel part in a side sectional view, and a part including a tapered part including an inclined part in the side sectional view. The raw pipe portion is a portion having an outer diameter of the round steel pipe P before the pipe expansion molding. Therefore, the tube expansion ratio after the three-stage tube expansion molding can be obtained by dividing the dimension obtained by subtracting the outer diameter of the raw tube portion from the outer diameter of the straight portion by the outer diameter of the raw tube portion.

Here, as a result of investigating the change in the plate thickness in each part of the round steel pipe P after the pipe expansion forming as described above, as shown in FIG. 7, depending on the presence or absence of pressing (shaft pressing) to the opening end by the side mold 21, It was possible to greatly suppress the thickness reduction. In particular, the reduction in the plate thickness in the vicinity of the boundary portion between the straight portion and the taper portion was significantly suppressed by the combined use with the punch 12 of the side mold 21.
Furthermore, as a result of investigating the reduction in the plate thickness of the round steel pipe P in the first to third steps described above, as shown in FIG. 8, the pressing (shaft on the opening end by the side mold 21 in the second and third steps is performed. Depending on the presence or absence of pressing, the thickness reduction in the second and third steps could be significantly suppressed.

  In the tube expansion forming apparatus 10 of the present embodiment, as described above, in the process of forming the tube expansion portion P1 having a desired tube expansion ratio in a plurality of stages using the plurality of punches 12a to 12c having different sizes, the first first In the step, without using the side mold 21, the punch 12a is inserted into the open end of the round steel pipe P to form the expanded portion. In the subsequent steps (second and third steps), the punches 12b and 12c and the side mold 21 are used together, and the side mold 21 presses the opening end portion simultaneously with the insertion of the punches 12b and 12c. (Press the axis).

  Thereby, by using both the insertion of the punches 12a to 12c and the axial pressing by the side mold 21, it is possible to suppress a sudden decrease in the thickness when forming the expanded portion P1 at the end of the round steel pipe P. The limit can be increased and the occurrence of buckling or cracking can be effectively prevented. Also, in the first step where buckling or cracking is unlikely to occur, the side mold 21 is not used together, thereby minimizing the lengthening of the molding time by using the shaft pressing by the side mold 21 and improving the efficiency. The tube expansion can be performed well.

[Other Embodiments]
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of invention.
(A)
In the said embodiment, the example which performs a pipe expansion shaping | molding in three steps including the 1st-3rd pipe expansion shaping | molding step was given and demonstrated. However, the present invention is not limited to this.
For example, the steel pipe may be expanded by a method including a two-stage tube forming step or a four-stage or more tube expanding step.

(B)
In the said embodiment, the example which performs pipe expansion shaping | molding with respect to the round steel pipe with a substantially circular cross section was given and demonstrated. However, the present invention is not limited to this.
For example, the pipe expansion molding may be performed on a deformed steel pipe having a substantially square shape, polygonal shape, or the like using the pipe expansion molding method described above.

(C)
In the said embodiment, the example which starts the axial push to the opening edge part of the round steel pipe P using the side metal mold | die 21 at the timing when a straight part is formed in the pipe expansion part P1 in the punch 12 insertion process demonstrated. . However, the present invention is not limited to this.

For example, the shaft pressing to the open end of the round steel pipe may be started using the side mold at the timing when the thickness reduction near the expanded pipe portion starts.
The thickness reduction may be detected based on, for example, the stroke amount of the punch being inserted into the round steel pipe or the pressure fluctuation applied to the punch.

  The steel pipe expansion forming method of the present invention has the effect of expanding the forming limit of the steel pipe expansion forming method including a plurality of stages and efficiently performing pipe expansion forming with a high yield. Widely applicable to molding.

DESCRIPTION OF SYMBOLS 10 Tube expansion apparatus 11 Main cylinder 12 Punch 12a Punch A (1st punch)
12b Punch B (second punch)
12c Punch C (3rd punch)
15 Side pressure device 16 Hydraulic pump 20 Control unit 21, 21b, 21c Side mold 22 Side cylinder 23, 24 Outer pressure device 23a, 24a Outer portion 23b, 24b Outer cylinder 25, 26 Clamp device 25a, 26a Clamp type 25b, 26b Clamp cylinder 27 Positioning part S Step

JP 2000-246382 A (published September 12, 2000)

Claims (6)

A steel pipe expansion molding method in which a plurality of punches having different sizes are inserted into an end opening of a steel pipe to perform pipe expansion molding in multiple stages,
Inserting the smallest first punch among the plurality of punches into the steel pipe, and a first tube expansion forming step that does not press the end of the steel pipe;
Inserting a second punch larger than the first punch into the steel pipe, and using a side mold to press the end of the steel pipe in the insertion direction of the second punch; and
A method for expanding and forming a steel pipe. The first punch has the largest tube expansion ratio among the plurality of punches,
The steel pipe expansion forming method according to claim 1. The steel pipe is a round steel pipe having a substantially circular cross section.
A method for expanding and forming a steel pipe according to claim 1 or 2. After the second tube expansion forming step, the method further comprises a third tube expansion forming step of inserting a third punch larger than the second punch into the steel pipe.
The method for expanding and forming a steel pipe according to any one of claims 1 to 3. In the third pipe expansion molding step, as in the second pipe expansion molding step, the end of the steel pipe is pressed using the side mold.
The method for expanding and forming a steel pipe according to claim 4. A tube expansion molding device that inserts a plurality of punches having different sizes into an end opening of a steel pipe and performs tube expansion molding in multiple stages,
The plurality of punches;
A side mold for pressing the end of the steel pipe in the punch insertion direction;
In the first first tube forming step of inserting the smallest punch among the plurality of punches into the end opening of the steel pipe, the side mold is not used, and in the subsequent tube forming step, the punch and the side die are used. A control unit that performs control so that pipe expansion molding is performed in combination with a mold;
Expanded pipe forming apparatus.

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