JPH0659503B2 - Stepped tube / tapered tube manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a stepped pipe and a tapered pipe by compressing a raw material pipe in a radial direction and subjecting it to a drawing process.

[Prior Art] Conventionally, as a method of radially compressing a raw material tube and drawing it, there is a method as shown in FIGS. 6 (a) and 6 (b). FIGS. 6 (a) and 6 (b) show the state before the drawing process is started.
The pressing force in the radial direction F is applied to the upper and lower split pressing dies 2A and 2B having a semi-cylindrical surface having a diameter smaller than the outer diameter of the pipe.
It reduces the diameter of 1.

However, according to this method, the diameter reduction rate (d _o / d) / d _o × 100 (where d _{o is} the outer diameter of the material tube and d is the outer diameter after drawing) obtained by the first pressing. Has a problem that in a carbon steel pipe for general piping, it remains about 8%, and the thickness of the narrowed portion increases according to the diameter reduction rate.

Further, the diameter reduction rate is the wall thickness t _{o with} respect to the outer diameter d _o of the material pipe.
It depends on the ratio of (t _o / d _o ), and decreases as the tube becomes thinner. For example, at t _o / d _o = 0.03, the diameter reduction rate per time is almost 4%.
It will be about. Further, as the diameter reduction of the drawn portion progresses by drawing a plurality of times, it is necessary to reduce the diameter reduction rate per time due to the influence of work hardening, or buckling will occur. Therefore, it is usually necessary to perform the annealing treatment after the drawing process is performed three to four times. In addition, according to this conventional method, the amount of elongation in the axial direction is small, and the thickness of the narrowed portion is only increased.

[Problems to be Solved by the Invention] The present invention increases the diameter reduction rate per time described above,
As a result, the number of times of drawing to reach the desired drawing shape is reduced, the increase in the thickness of the drawing part is suppressed, and the simple device does not require replacement of the drawing die or the like. An object of the present invention is to provide a method capable of forming a tapered tube and a tapered tube with a uniform or controlled wall thickness distribution.

[Means for Solving the Problem] In order to solve the above problems, a method for manufacturing a stepped pipe according to the present invention is designed so that both ends of a raw material pipe are gripped by a chuck and pulled to yield a material corresponding to the material of the raw material pipe. A tensile force within the range where the elongation of the material pipe does not progress, which is more than the point or the proof stress, is applied, and when the material pipe is drawn between the squeezing rolls in this applied tensile force, the drawing is performed. As a roll, a dent having a semi-circular cross section whose radius of curvature becomes gradually smaller is provided on the circumference, and when the squeezing rolls are driven synchronously in a state of being joined to each other, the dent is formed at the joining portion. The space formed by the above is formed so that the depth of the recess becomes gradually shallower so that the circle formed by the recess is smaller than the diameter of the material pipe between the drawing rolls. Diameter of the first stage The first stage draw forming is carried out by passing the material tube through a fixed diameter, and then the circle formed by the depression between them is reduced by the rotation of the draw roll, and the second stage draw is drawn. The diameter of the second stage is reduced by passing the material pipe in a range shorter than the range subjected to the first stage drawing process with a tensile force higher than the yield point or proof stress. It is characterized in that a stepped tube having a pressed and compressed diameter in a stepped state is obtained by repeating the operation.

Further, in the method for manufacturing a tapered pipe in the present invention, in a state in which the tensile force is applied to the raw material pipe, the circle formed by the recess between the drawing rolls is reduced in diameter in relation to the forming speed of the raw material pipe. By passing the material pipe while making it, the material pipe is formed into a taper shape determined by the mutual relation of their speeds, and then the circle formed by the recess between the squeezing rolls is reduced in diameter as compared with the time of molding Using the part, while reducing the diameter of the circle in relation to the forming speed of the material pipe, the same draw forming is performed by passing the material pipe in a state in which a tensile force equal to or higher than the yield point or the proof stress is applied. By repeating the operation, the raw material pipe is pressed and compressed in the radial direction to obtain a tapered pipe.

More specifically, in the method of the present invention,
As shown in FIG. 1, when a radial pressing force F for drawing is applied to the material pipe 10, a point of applying a tensile stress equal to or higher than the yield point or the proof stress to the material pipe 10 by an axial tensile force P in advance. It has a great feature.

When a tensile stress is applied to a material, as shown in the stress-strain diagram of FIG. 5, a strain corresponding to the stress is generated. However, the tensile stress is a tensile stress equal to or higher than the yield point or the proof stress. Needless to say, the stress is in a range where the elongation of the material pipe does not reach the fracture, that is, the stress is not less than the yield point in FIG. Here, the K point is
Although it is a point that reaches the maximum stress region ▼ line, the stress near the point K easily breaks. Therefore, it is actually necessary to set the stress to some extent lower than that.

In this way, when a tensile stress is applied to the material pipe within the range where the elongation of the material pipe does not proceed above its yield point or proof stress, the material pipe begins to expand due to plastic deformation due to that stress, The hardening increases the deformation resistance of the material tube, and as a result, the elongation stops after a slight elongation. When the material pipe is subjected to such an axial tensile force and the diameter of the material pipe is reduced by a squeezing roll, the material pipe is subjected to a tensile force equivalent to its yield point or proof stress, Since the forming is performed by the squeezing rolls, it is possible to increase the diameter reduction rate by their combined action, and as will be understood from the examples described later, for example, in the case where no tensile force is applied, The diameter reduction rate is about 8%, whereas the diameter reduction rate can be about 15%.

In the draw forming of the second and subsequent stages, as in the first stage, it is necessary to apply a tensile force that is equal to or higher than the yield point or proof stress of the material at the time of forming and within the range in which the elongation of the material pipe does not proceed. However, in the second and subsequent stages, the yield point (proof stress) naturally rises as compared with the drawing process up to the previous stage, because the portion whose diameter has been reduced by the forming up to the previous stage is work-hardened. On the other hand, since the part that has been reduced in diameter by the drawing process up to the previous stage is expanded in the axial direction, thickening of the drawn part is suppressed, and its cross-sectional area is the cross-sectional area of the material pipe at the start of processing in the previous stage. It is decreasing more. Therefore, it is necessary to set the tensile force of each step in consideration of the processing of those preceding steps. In actual drawing, set the appropriate tensile force that has been experimentally or empirically obtained in advance, or detect the tensile force that causes plastic deformation due to yield during the drawing process at each stage and It may be set to an appropriate value based on the force.

On the other hand, in selecting the diameter reduction rate, it is desirable to reduce the number of machining operations required to reduce the diameter of the material pipe to a predetermined diameter, that is, to reduce the number of machining steps to achieve economic efficiency. In order to reduce the diameter of the material pipe while further expanding it, it is desirable to carry out a drawing process in a larger number of stages.

Further, the occurrence of buckling depends on the material of the material pipe, the wall thickness / diameter of the material pipe, the diameter reduction rate, the magnitude of the tensile force, etc. from the viewpoint of processing. Regarding the material, if it is a normal wrought material, there is no big difference. As for the wall thickness / diameter, the thinner the tube, the more likely it is to buckle. Further, if the diameter reduction rate is increased, buckling is likely to occur. However, as will be understood from Examples described later, it is possible to suppress buckling by increasing the tensile force. Therefore, in consideration of the above-mentioned various conditions, the draw forming may be performed under the condition that buckling does not occur.

Then, control the magnitude of the pulling force, the amount of diameter reduction, etc. at each stage,
Depending on the selection, a stepped or tapered tube can be formed with a uniform or appropriately controlled wall thickness distribution.

Such control of the wall thickness distribution can be achieved by appropriately adjusting the axial weight balance when the molded pipe is used as a ball striking exercise device or the like, and the axial strength balance when being used for various purposes including the above ball striking device. This is effective when setting.

In addition, another great feature of the present invention is that, when the material pipe is passed between the drawing rolls to perform the draw forming, as the draw rolls, a recess whose radius of curvature is gradually reduced in a semicircular cross section is formed on the circumference. When the squeezing rolls are circumferentially mounted and are driven synchronously in a state where they are joined to each other, the depth of the depressions is gradually reduced so that the space formed by the depressions in these joints has a circular cross section. The material tube is formed into a stepped shape or a taper shape.

The use of such a squeezing roll makes it possible to easily form a stepped or tapered pipe without the need to replace the squeezing die and the like. It is also advantageous in that both the tapered pipe and the tapered pipe can be molded.

[Embodiment] Hereinafter, a configuration example of a method of the present invention and an apparatus for performing the method will be described in detail with reference to the drawings.

2 to 4 show an example of a draw roll type draw forming apparatus for producing stepped pipes and tapered pipes by carrying out the method of the present invention.

This device is provided with a sliding groove 12 on a base 11 that supports the entire device, holds a movable table 15 slidably along the sliding groove 12, and mounts it on the base 11 for movement. By connecting the rod 14 of the cylinder 13 to the support wall 16 on the moving table 15, the moving table 15 is formed so as to be slidable along the sliding groove 12 when the cylinder 13 is driven.

On the moving table 15, the support wall 16 and the pulling hydraulic cylinder 17 mounted on the moving table 15 are provided with toggle chucks 18 and 19 for holding the material pipe 10. These toggle chucks 18 and 19 are for holding the material tube 10 with the cored bar 20 inserted in the end portion of the material tube 10. A collet type chuck can be used in place of the toggle type chuck, but the operation is simplified by using the toggle type chuck.

On the other hand, on the base 11, a rotary shaft installation frame 23 and a rotary shaft installation plate 24 are arranged and fixed so as to face each other, and a drive shaft 26 and rotary shafts 27, 28 are supported between them. . Drive shaft 26
Is a prime mover consisting of a pulse motor, oil motor, etc.
A drive gear 31 connected to the drive shaft 26 is connected to a first gear 32 on the rotary shaft 27, and the first gear 32 is connected to the rotary shaft 27.
It is meshed with the second gear 33 on the 28. And the above gear
On the rotary shaft 27 and the rotary shaft 28, which are driven to rotate in the opposite directions at the same speed by 32 and 33, there are attached squeeze rolls 35A and 35B constituting a pressing die for squeezing the material pipe 10.

The squeeze rolls 35A and 35B have dents 36A and 36B with a semicircular cross section on the circumference.The cross-sectional shape of these dents 36A and 36B is the curvature of the roll as the rotation progresses. It is carved so that the radius becomes smaller and the depth becomes shallower. And both squeezing rolls 35A, 35
When B is driven synchronously by the gears 32 and 33 in the state of being joined to each other, the space formed by the double recesses 36A and 36B at the joining portion of the two squeezing rolls 35A and 35B is the outer diameter of the material pipe at the maximum portion. Has a circular cross section that is equal to or slightly larger than, and the diameter of the circle gradually decreases as the rotation of the rolls 35A and 35B progresses, and at the smallest part it reduces to a circular cross section that is about the outer diameter of the final formed shape. Is formed.

Next, a method of manufacturing the stepped pipe and the tapered pipe by the molding apparatus having the above configuration will be described.

In order to draw the material pipe 10 into a stepped pipe or a tapered pipe, first, in FIG. 2, the circle formed by the semicircular recesses 36A, 36B is the maximum diameter, that is, the material pipe diameter, of the drawing rolls 35A, 35B. Is driven to rotate by the prime mover 30 to a position (position shown in the figure) which is almost the same as, and stopped at that position. Also,
The rod 14 of the moving cylinder 13 is retracted to the right in FIG. 2, and the material pipe 10 with the cored bar 20 inserted at both ends is inserted from the right into the semi-circular recesses 36A and 36B of the squeezing roll, and both ends of the pipe are To toggle chucks 18 and 19. Then, the pulling cylinder 17 on the moving table 15 is retracted so that both ends of the material tube 10 are grasped by the toggle chucks 18 and 19, and the tensile stress of the material tube 10 becomes equal to or higher than the yield point or the proof stress. A force is applied to the material tube. This state is shown in FIG.

The above-mentioned tensile force is applied at a yield point or proof stress or more and within a range in which the elongation of the material pipe does not proceed, but the magnitude of the tensile force under such restrictions and the adjustment of the diameter reduction amount at each stage are adjusted. The degree of thickening of the raw material pipe during molding can be adjusted by, for example, by making the thickness constant while suppressing the thickening of the forming pipe, or by increasing or decreasing the tensile force, it is partially appropriate. The thickness can be controlled.

When manufacturing a stepped pipe, in this state, the first gear 32 and the second gear 33 are rotated in opposite directions by the prime mover 30, and the circle formed by the semi-circular recesses 36A and 36B of the squeeze roll is sequentially formed. The diameter is reduced to stop the squeezing rolls 35A, 35B at a position where the diameter of the semicircular recesses 36A, 36B corresponds to the squeezing diameter of the first stage.

Therefore, the moving table 15 is moved to the left by the moving cylinder 13 installed on the base 11 to complete the first stage draw forming over the entire drawn portion of the material tube 10.

Then, the prime mover 30 further rotates the squeeze rolls 35A, 35B in the direction of reducing the diameter, so that the diameter of the circle formed by the recesses 36A, 36B corresponds to the second stage squeeze diameter. The rotation is stopped, and in that state the moving table 15 is moved to the left to complete the second stage draw forming. The movement amount at this time is made shorter than that within the range where the first stage drawing process is performed.

Further, in the drawing process of the third stage, the movable table 15 is moved to the left as needed within the range of the drawing process of the second stage, and is held at the drawing start position of the third stage, and then the drawing roll is again drawn. Rotate and stop 35A and 35B to the position corresponding to the third stage drawing diameter, and perform the same as in the first stage drawing.

In this way, the stepped molding tube can be obtained without exchanging a large number of dies by alternately repeating the left and right reciprocating motion of the moving table and the inching motion of the squeezing roll in the diameter reducing direction.

On the other hand, in order to obtain a tapered tube, from the state shown in FIG.
The prime mover 30 is driven in relation to the moving speed of the moving table 15 to the left, and the squeezing rolls 35A and 35B are sequentially rotated in the diameter reducing direction. As a result, the material tube 10 is moved to the moving table above.
It can be formed into a taper shape that is determined by the interrelationship between the moving speed of 15 and the rotation speed of the squeezing rolls 35A and 35B, and then the circle formed by the depressions 36A and 36B between the squeezing rolls 35A and 35B is formed as described above. Using the part that has been reduced in diameter from time,
While reducing the diameter of the circle in relation to the forming speed of the raw material pipe, similarly draw forming by passing the raw material pipe in a state in which a tensile force equal to or higher than the yield point or proof stress is applied,
After repeating this operation a required number of times, it is possible to obtain a final molded tube having a desired taper in the final drawing.

After the molding is completed, the load of the pulling cylinder 17 is removed, and the toggle chuck 19 is moved to the right to remove both ends of the molded tube from the toggle chuck and pull out the final molded tube from the squeeze roll.

When the above-mentioned stepped formed tube is formed, the formed stepped tube is not used as the final formed tube, and it is attached to the forming device as a material tube and associated with the movement amount of the moving table 15. By driving the prime mover 30 with the lever, a tapered pipe can be formed.

Further, the illustrated drawing forming apparatus is configured to form a material pipe between a pair of drawing rolls. However, the drawing roll is not limited to the arrangement as illustrated, and the drawing pipe is formed around the material pipe. The above squeezing rolls can be arranged in the radial direction.

Next, an experimental example of forming a material pipe according to the present invention will be shown.

As a material pipe, outer diameter φ18.9 mm, wall thickness 1.35 mm, total length about 3
A 50 mm copper tube (JIS standard C1200T-0) was used to perform intermediate annealing, and the minimum diameter was reduced to φ8 mm to form a stepped tube.

In the experiment, a device capable of applying substantially the same stress load as the device shown in FIGS. 2 to 4 was used. First, both ends of a material pipe having an outer diameter of φ18.9 mm were gripped by chucks, Tensile force P
Is 0 (comparative example), 1200 (example substantially corresponding to the yield point of the raw material pipe), and 1600 kgf (range in which the elongation of the raw material pipe does not proceed), and a diameter reduction of φ16 mm (diameter reduction rate; 15%) Tried. Table 1 shows the amount of elongation in the axial direction when the diameter was reduced.

Next, under the above P = 1200 kgf, the diameter of the material pipe after the diameter reduction of φ16 mm was successively reduced to φ14 mm, φ12 mm, φ10 mm, and φ8 mm. Table 2 shows the effect of the tensile force (range defined in the present invention) at the time of multi-stage diameter reduction on the axial elongation.

In addition, under non-tension, the diameter is reduced from 16 mm to 14 mm, and 12
When the diameter was reduced from φ14 mm to φ12 mm (comparative examples) with a constant tensile force of 00 kgf, the material tube buckled, and subsequent molding was impossible.

[Effects of the Invention] According to the method of the present invention described in detail above, by increasing the diameter reduction rate per time, the number of times of drawing to reach the desired drawing shape is reduced, and With a simple device that suppresses thickening, stepped and tapered pipes can be formed in a uniform or controlled wall thickness distribution at room temperature without the need to replace the drawing die. can do.

[Brief description of drawings]

FIG. 1 is an explanatory view relating to a pressing force at the time of draw forming according to the present invention, FIGS. 2 to 4 show an example of an apparatus for carrying out the method of the present invention, and FIGS. 2 to 4 are the draw rolls. FIG. 2 shows the configuration of a model draw forming device, FIG. 2 is a plan view showing a state before the start of forming, which is cut along the axis of the material pipe, FIG. 3 is a partially cutaway front view, and FIG. 4 is FIG. C-C sectional view of Fig. 5, Fig. 5 is a stress-strain diagram in a tensile test of a metallic material, and Fig. 6 (a) is a model for explaining a pressing force at the time of conventional press-swaging type draw forming. A front view, and FIG. 2B is a side view thereof. 10 …… Material tube, 18,19 …… Chuck, 35A, 35B …… Squeezing roll, 36A, 36B …… Dent.

Claims (2)

[Claims] 1. The material pipe (10) is grasped at both ends by chucks (18, 19) and pulled, and the elongation does not proceed even though the yield point or proof stress is higher than the material pipe material. Apply a tensile force within the range, and with this tensile force applied, squeeze the material pipe (10)
(A, 35B), when performing draw forming, the draw roll (35A, 35B) has a semicircular cross section with a recess (36A, 36B) whose radius of curvature gradually decreases. And the squeezing rolls (35A, 35B) are driven synchronously in a state where they are joined to each other, so that the space formed by the recesses (36A, 36B) at their joints has a circular cross section, The dents (36A, 36B) are formed so that the depth of the dents (36A, 36B) also gradually decreases, and the dents (36A, 36B) are placed between the squeezing rolls (35A, 35B).
The diameter of the circle formed by
By fixing it to the step diameter and passing the material tube (10),
The first stage draw forming is performed, then the circle formed by the depressions (36A, 36B) between them is reduced by the rotation of the draw rolls (35A, 35B), and the second stage draw diameter is The second stage draw forming is performed by passing the material pipe in a range shorter than the range subjected to the first stage drawing with a tensile force higher than the yield point or proof stress, and by repeating this operation. A method for producing a stepped pipe, characterized in that a stepped pipe is obtained by pressing and compressing the raw material pipe (10) in a stepped state. 2. The both ends of the material pipe (10) are gripped and pulled by the chucks (18, 19), and the elongation is higher than the yield point or proof stress corresponding to the material of the material pipe, but the elongation of the material pipe does not proceed. Apply a tensile force within the range, and with this tensile force applied, squeeze the material pipe (10)
(A, 35B), when performing draw forming, the draw roll (35A, 35B) has a semicircular cross section with a recess (36A, 36B) whose radius of curvature gradually decreases. And the squeezing rolls (35A, 35B) are driven synchronously in a state where they are joined to each other, so that the space formed by the recesses (36A, 36B) at their joints has a circular cross section, The dents (36A, 36B) are formed so that the depth of the dents (36A, 36B) also gradually decreases, and the dents (36A, 36B) are placed between the squeezing rolls (35A, 35B).
By forming the circle formed by the material pipe (10) while reducing the diameter in relation to the forming speed of the material pipe, the material pipe (10) is formed into a taper shape determined by the mutual relation of the speeds, Depression (36A, 36B) between the above squeezing rolls (35A, 35B)
By using the portion where the circle formed by the diameter is reduced from that at the time of forming, while reducing the diameter of the circle in relation to the forming speed of the material pipe, a tensile force equal to or higher than the yield point or the proof stress is applied. The same draw forming is performed by passing the material pipe (10) in this state, and by repeating this operation, the material pipe (10) is pressed and compressed in the radial direction to obtain a tapered pipe. And a method for manufacturing a tapered pipe.