JPH0659512B2 - Manufacturing method of reduced diameter tube - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a tapered pipe or a stepped 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. 12 (a) and 12 (b). Fig. 12
(a) and (b) show the state before the drawing process, in which the radial pressing force F is applied to the upper and lower two-divided pressing dies 2A, 2B having a semi-cylindrical surface with a diameter smaller than the outer diameter of the material tube 1. , To reduce the diameter of the tube 1.

However, according to this method, the diameter reduction rate (d ₀ -d) / d ₀ × 100 (where d _{0 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.

Also, the diameter reduction rate is the wall thickness t _{0 with} respect to the outer diameter d ₀ of the material pipe.
It depends on the ratio of (t ₀ / d ₀ ), and decreases as the tube becomes thinner. For example, at t ₀ / d ₀ = 0.03, the diameter reduction rate per time is approximately 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 expansion in the axial direction is small, and the thickness of the diaphragm portion only increases the image.

[Problems to be Solved by the Invention] The present invention increases the diameter reduction rate per time described above,
As a result, it is possible to reduce the number of times of drawing to reach a desired drawing shape, suppress the increase in the thickness of the drawing portion, and form a tapered or stepped tube with a uniform or controlled wall thickness distribution. The present invention intends to provide a method for manufacturing such a tapered pipe or stepped pipe.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the manufacturing method of the present invention is such that both ends of the material tube are gripped by chucks and the yield point or proof stress corresponding to the material of the material tube or more While applying a tensile force that will become, the material pipe is pressed and compressed in the radial direction by a pressing die,
It is characterized in that the material pipe is formed in a tapered shape or a stepped shape by repeating this operation.

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.

Thus, when the diameter of the material pipe is reduced by the pressing die in the state where the tensile force is applied to the material pipe in the axial direction, in particular, the tensile force is equal to or higher than the yield point or the proof stress corresponding to the material of the material pipe. The diameter reduction rate can be increased. For example, when tensile force is not applied, the diameter reduction rate per time is about 8%, whereas the diameter reduction rate is about 15%. You can

Further, due to the action of the tensile force, an increase in the thickness of the narrowed portion is suppressed when the diameter of the raw material pipe is reduced, and a tapered or stepped pipe is formed with a uniform or appropriately controlled wall thickness distribution. be able to.

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.

[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 5 show an example of an apparatus for producing a tapered pipe or a stepped pipe by press-swaging type draw forming for carrying out the method of the present invention.

This device is provided with, on the left and right sides of a base 11, slidable chuck slide blocks 12 respectively connected to left and right pulling hydraulic cylinders (not shown) for applying a pulling force to the material pipe 10. There is. This pair of left and right chuck sliding blocks 12
As shown in FIGS. 2 and 3, by engaging with the collar portion of the collet mounting bracket 13, the tensile force of the cylinder is transmitted to the chuck 15. A large number of sliding balls 16 are arranged in the groove so that when the material tube 10 moves up and down, it can move smoothly in synchronization with the up and down movement. The ball receiving plate 17 supports the ball so that it does not fall.

The chuck 15 for gripping both ends of the material tube 10 is a state in which a core metal 18 is inserted inside the material tube 10 and a claw 19 and a tightening ring 20 of a collet chuck are attached to the outside thereof, and the tightening ring 20 is rotated. The collet fitting 13 is screwed to the tip of the fitting 13.

On the other hand, in the center of the base 11, upper and lower half-cylindrical die guide members 24A, 24B are arranged, and the inner surface of each of these die guide members 24A, 24B is divided into a plurality of dice 25.
A, ..., and dies 25B, ... are mounted so as to be movable in the axial direction. Also, the upper die guide member 24A
Is attached to a die pressing plate 27 connected to a die pressing hydraulic cylinder (not shown). As shown in FIG. 4, the pressing dies 25A and 25B are slidably fitted on the upper and lower die guide members 24A and 24B.
This is done by fitting the dies 25A and 25B into the semi-cylindrical recess of B and hugging them with the die stop plate 26. Also,
In order to allow the dies 25A and 25B to move smoothly in the axial direction while being held, an appropriate clearance is provided in the semi-cylindrical part of the die guide members 24A and 24B, and the sliding surfaces of both are lubricated. The membrane is interposed.

In order to perform draw forming with the above apparatus, the upper die guide member 24A is raised by the die pressing hydraulic cylinder, and the chuck slide block 12 is retracted by the left and right pulling hydraulic cylinders. The cored bar 18 is inserted inside both ends, and the claw 19 and the tightening ring 20 of the chuck 15 are attached to the outside of the material tube 10. Next, the central portion of the material tube 10 to be drawn is placed on the lower pressing die 25B, and first one tightening ring 20 is rotated to chuck one end of the material tube 10 to the collet mounting bracket 13. The chuck 15 at the other end of the material pipe 10 tightens by rotating the other tightening ring 20 while advancing the left and right pulling hydraulic cylinders.

After the material pipe 10 is set in this way, the die pressing plate 27 is lowered, and the respective pressing dies 25A, 25B fitted in the die guide members 24A, 24B are set as shown in FIG. The tube 10 is once stopped at a position in contact with it. FIG. 2 shows this state.

Next, the left and right chuck slide blocks 12 are pulled by the pulling hydraulic cylinder, and the pulling force P is applied to the material pipe 10. As described above, the tensile force is set to such a value that a tensile stress exceeding the yield point or proof stress depending on the material of the material pipe 10 can be induced in the material pipe. Therefore, the thickness of the molded pipe can be made constant or partially controlled to an appropriate thickness by adjusting the tensile force.

Die pressing plate with the tensile force applied
27 is lowered and the pressing force F is divided into upper and lower pressing dies 25A,
It acts on 25B and draws the material tube. At this time, the collet fitting 13 moves smoothly downward in synchronization with the lowering of the material pipe 10. Thus, the gap between the upper and lower pipes of the pressing dies 25A and 25B is eliminated, and the first stage drawing is completed. The state at this time is shown in FIG.

After the draw forming is completed, the pressing force F and the tensile force P are unloaded, the die pressing plate 27 is raised, and the left and right chucks 15 are returned to the state at the start of forming. Then, as shown in FIG. 6, the pressing dies 25A and 25B are moved to the second
Substituting the pressing dies 30A and 30B, the second stage draw forming is performed in the same manner to obtain the second stage draw-formed product 10a. further,
If necessary, repeat this step to make the final drawn product.

When the final drawing shape has a required taper portion, as shown in FIG. 7, the correction pressing dies 31A, 31B are used.
The final pressing die 32A, 32 is used for non-tapered parts.
Final draw forming is performed using B to obtain a final draw formed product 10b. The drawing process using the correction pressing dies 31A and 31B is for correcting the step formed in the previous process.

In order to effectively perform such drawing of material pipe,
In the drawing process, it is necessary to spread the tensile force of the material pipe over the entire drawn portion. For example, in FIG. 5, the region where the diameter of the material tube 10 is drawn from d ₀ to d ₁ is the entire area of the center of the material tube, and when pressing and swaging with a single pressing die over the wide area, the left and right sides of the pressing die are The outer edge region can be effectively drawn by receiving the tensile force P, but the central portion of the pressing die may not reach the tensile force. In that case, the desired drawing process can be performed. Can't do.

However, in the above apparatus, the pressing dies 25A and 25B are divided into three parts, which are arranged side by side so as to be slidable in the axial direction, and the thickness lm of the one wheel cutting die 25A, 25B is d. Since it is set to 2 to 3 times of ₀ , not only the action of tensile force acts between each pressing die 25A, 25B,
The tensile force acts even on the central portion of the pressing die, so that the pressing die can be uniformly processed as a whole.

Prior to the drawing process, a lubricant is applied to the processing part of the raw material tube 10 and the pressing dies 25A, 25B so that the pressing dies 25A, 25B
It is desirable that B can slide smoothly inside the die guide members 24A, 24B.

The apparatus examples described with reference to FIG. 2 to FIG. 7 above show the basic configuration of the apparatus for carrying out the method of the present invention. However, when applied to the practical mass production of the present invention, Further consideration for workability is required.

FIG. 8 to FIG. 10 show an example of the structure of an apparatus in consideration of such workability. The characteristic point of this apparatus is that a pair of eccentric squeeze rolls are used instead of a large number of pressing dies. In point. Further, the operation is simplified in that a toggle chuck is used instead of the collet chuck.

Explaining the configuration of this device in detail, a sliding groove 42 for slidably holding a moving table 45 is provided on a base 41 that supports the entire device, and a sliding table 42 mounted on an image of the base 41 is used. By connecting the rod 44 of the cylinder 43 to the support wall 46 on the moving table 45, the moving table 45 is drivably supported along the sliding groove 42.

On the moving table 45, the support pipe 46 and the pulling hydraulic cylinder 47 mounted on the moving table 45 are connected to the material pipe.
Toggle chucks 48 and 49 for holding 10 are provided.
These toggle chucks 48, 49 hold the material tube 10 with the core metal 50 inserted in the end portions, as in the case described above.

On the other hand, a pivot shaft installation frame 53 and a pivot shaft installation plate 54 are fixed on the base 41, and a drive shaft 56 and rotary shafts 57, 5 are interposed between them.
8 is supported. The drive shaft 56 is connected to a prime mover 60 including a pulse motor and an oil motor, and a drive gear 61 provided on the drive shaft 56 is a first gear on a rotary shaft 57.
62, and this first gear 62 meshes with the second gear 63 on the rotary shaft 58. The eccentric squeeze roll 65A, which constitutes a pressing die for squeezing the material tube 10, is provided on the rotary shaft 57 and the rotary shaft 58 that are rotatably driven by the gears 62 and 63.
Installed 65B.

The squeezing rolls 65A, 65B have cavities 66A, 66B with a semicircular cross section on the circumference.The radii of the cross sections gradually decrease with the rotation of the rolls. Moreover, the recess is carved so that it gradually becomes shallower. Therefore, when both squeezing rolls 65A, 65B are driven synchronously by the gears 62, 63 in a state where they are joined to each other, the space formed by both dents 66A, 66B is equal to the outer diameter of the material pipe at the start of molding. Make up a circle,
The diameter of the circle gradually decreases as the rotation of the rolls 65A and 65B progresses.

In order to draw the raw material tube 10 into a stepped tube or a tapered tube with the device having such a configuration, first, in FIG. 8, the eccentric drawing rolls 65A and 65B are cut into their semicircular recesses 66.
The prime mover 60 rotationally drives to a position where A and 66B have the maximum diameter, that is, the same as the material pipe diameter (the position shown in the drawing), and stops at that position. Also, the rod 44 of the moving cylinder 43 is retracted to the right, and the material pipe 10 with the cored bar inserted at both ends is inserted from the right into the semicircular recesses 66A and 66B of the squeezing roll, and both ends of the pipe are toggled. Attach it to the chucks 48 and 49. And the moving table
Retract the pulling cylinder 47 on the 45 to move the toggle chuck.
Hold both ends of the material pipe with 48, 49, and
A tensile force is applied to the raw material pipe so that the tensile stress of is higher than the yield point or yield strength. This state is shown in FIG. As in the case of the above-mentioned apparatus, the wall thickness of the molded tube can be made uniform or appropriately controlled by adjusting the tensile force.

In this state, the prime mover 60 causes the first gear 62 and the second gear 63 to
When they are rotated in the opposite directions, the circle formed by the semicircular recesses 66A, 66B of the eccentric squeeze roll is successively reduced in diameter.
The eccentric squeeze rolls 65A, 65B are stopped at the position where the diameter of the semicircular recesses 66A, 66B corresponds to the first stage squeeze diameter.

Therefore, the moving table 43 is moved to the left by the moving cylinder 43 installed on the base 41, and the first stage draw forming is completed over the entire draw portion of the material tube 10.

Next, the eccentric squeeze rolls 65A, 65B are further rotated in the diameter reducing direction by the prime mover 60, and the squeeze rolls 65A, 65B are positioned at a position where the diameter of the circle formed by the recesses 66A, 66B corresponds to the second stage squeeze diameter.
The rotation of B is stopped, and in that state, the moving table 45 is moved to the right 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 step, after moving the moving table 45 slightly to the left to set the drawing start position of the third step, the drawing rolls 65A and 65B are again moved to the position corresponding to the drawing diameter of the third step. The rotation and stop are performed, and the drawing is performed in the same manner as the first stage draw forming.

In this way, the alternating reciprocating motion of the movable table and the eccentric squeeze roll in the direction of decreasing the diameter are alternately repeated,
It is possible to obtain a stepped molding tube without replacing a large number of dies.

On the other hand, in order to obtain a tapered tube, from the state of FIG.
The prime mover 60 is driven in association with the leftward movement amount of the moving table 45 to rotate the eccentric throttle rolls 65A, 65B in the diameter reducing direction. Thereby, the material tube 10 is moved to the moving table 45 described above.
Can be formed into a taper shape that is determined by the interrelationship between the moving amount and the amount of rotation of the drawing rolls 65A and 65B, and in the final drawing, it is possible to obtain a final formed pipe having a desired taper.

After the molding is completed, the load of the pulling cylinder 47 is removed and the toggle chuck 49 is moved to the right to remove both ends of the molded tube from the dog chuck and pull out the final molded tube from the squeeze roll.

Of course, even in the middle of step forming, by driving the prime mover 60 in association with the movement amount of the moving table 45, it is possible to form a tapered tube without using a step forming tube.

Further, in each of the above-mentioned draw forming devices, the material pipe is formed between the pair of pressing dies or the pair of eccentric drawing rolls, but the pressing die and the eccentric drawing roll are not necessarily illustrated. Not only the correct arrangement,
Two or more pressing dies or squeezing rolls can be radially arranged around the material tube.

Next, an embodiment of the method of the present invention by the apparatus shown in FIGS. 2 to 5 will be described.

The drawing process by press swaging is performed on a material tube made of copper or brass using a device as shown in Fig. 2 to Fig. 5, and the outer diameter is 19 mm, the wall thickness is 1.5 mm, and the entire circumference is 350 mm.
The central part of the mm material tube was machined between about 250 mm. At the time of the first draw forming, that is, when the outer diameter is drawn from 19 mm to 16 mm, when comparing the degree of axial elongation and thickening of the processed part with the case where no tensile force is applied to the copper pipe, the axial elongation is In the case of no tensile force, the thickness was 7.5% and 12%, while the thickness was 11% and only about 7%.

The outer diameter change is 19 mm in the multiple pressing process using the pressing die.
→ 16 mm → 14 mm → 12 mm → 10 mm → 8 mm, but in the tensile-free drawing process as a comparative example, at 16 → 14 mm, the meat protruded between the upper and lower pressing dies and the molding became impossible. Therefore, in order to continue appropriate molding in the case of no tensile force, it is necessary to carry out a small pressing step with a pressing die with a small diameter reduction rate. That is, the number of steps is doubled and the thickness is increased.

On the other hand, when the required tensile force is applied, the axial elongation of the portion made 19 → 8 mm through the multiple steps of drawing is 68% and the wall thickness is increased by 41%. It could be processed in numbers. Moreover, the same results could be obtained for brass tubes without intermediate annealing.

FIG. 11 shows a total length of 350 using the apparatus shown in FIGS.
The experimental results (throttle effect of adding tension) when the diameter of a copper pipe having a diameter of 1 mm, an outer diameter of 18.9 mm and a wall thickness of 13.5 mm is reduced as a material pipe are shown.

As the upper and lower pressing dies, 16mmφ, 14mmφ, 12mmφ,
Repeated diameter reduction processing using 10 mmφ and 8 mmφ,
By reducing the diameter from 18.9 mmφ to 8 mmφ, the deformation behavior of the central part of the material tube was investigated. The axial length of the pair of pressing dies was 50 mm.

In the experiment, in order to investigate the effect of reducing the diameter by applying tension, first, drawing without tension ([D] in the figure)
Was performed by a diameter reduction path of 16 mm → 14 mm → 12 mm. In this case, when 14 mm was drawn, buckling occurred on the split surfaces of the upper and lower pressing dies, so the diameter could not be reduced to 12 mm.

The path of the diameter reduction by applying tension is to use the above-mentioned pressing dies one by one and move the pressing dies to the final drawing part one by one, and 16mmφ diaphragm 3 times (F = 1200), 14mmφ diaphragm 3 times (F = 1400). , 12mmφ diaphragm 3 times (F = 1600), 10mmφ diaphragm 3 times (F = 1600), 8mmφ diaphragm 2 times (F = 1600), and the diameter-reducing path [A] and 2-4 pressing dies at the same time. Use 2 pieces of 16mmφ (F = 1200), 2 pieces of 16mmφ and 2 pieces of 14mmφ (F = 1600), 1 piece each of 16mmφ, 14mmφ and 12mmφ (F = 1600), 14mmφ, 12mmφ and 10mmφ Deformation behaviors were investigated for two types, one (F = 1800), 12 mmφ, 10 mmφ, and 8 mmφ each (F = 1800) and the diameter-reducing path [B].

The tension F ≈ 1200 kg corresponds to the load (yield point) at which a stress of about 16 kgf / mm ² occurs in the cross section of the material pipe and begins to expand, and the deformation behavior under this tension was also confirmed (path [C]).

In FIG. 11, drawing processing under no tension [D],
Comparing the experimental results with the drawing [C] at the tension F = 1200 kg, there is almost no difference in the elongation amount of both. That is, in the tensile stress region below the yield point or proof stress, the effect of applying tension is negligible.

Also, in [D], it was impossible due to the buckling of the diameter reduction of 12 mm as described above, but it is possible to reduce the diameter under the tension F = 1200 kg of [C], and the extension amount is about 7.5 mm. became. Furthermore, when the diameter of the [B] path was reduced, the amount of elongation was 12.5 mm due to the addition of tension of 1600 kg, but when the diameter of the [A] path was reduced, it was 18.5 mm.
mm, and the effect of adding tension was remarkable.

[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 a desired drawing shape is reduced and the drawing portion It is possible to suppress the increase in thickness and form the material pipe into a tapered shape or a stepped shape with a uniform or controlled wall thickness distribution.

[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, and FIGS. 2 to 7 show an example of an apparatus for carrying out the method of the present invention. FIG. 2 is a state before the start of draw forming. FIG. 3 is a front sectional view showing FIG. 3, FIG. 3 is a partial plan view seen in the direction of the arrow A in FIG. 2, and FIG. 4 is a sectional view taken along the line BB in FIG.
The figure is a front cross-sectional view showing the state at the completion of the first stage drawing.
FIG. 6 is a front cross-sectional view showing a state after completion of the second stage draw forming, FIG. 7 is a front cross-sectional view showing a manufacturing process of a tapered pipe by draw forming, and a front cross-sectional view after completion of final draw forming, FIGS. FIG. 8 shows the structure of an eccentric squeeze roll type squeeze forming apparatus. FIG. 8 is a plan view showing the state before the start of slicing cut along the axis of the material pipe, FIG. 8 is a cross-sectional view taken along the line CC of FIG. 8, FIG. 11 is a graph showing the experimental results (drawing effect of tension addition) relating to the present invention, and FIG. 12 (a) is the drawing press of the conventional press-swaging type. FIG. 2 (b) is a schematic front view for explaining the pressing force in FIG. 10 …… Material tube, 15,48,49 …… Chuck, 25A, 25B …… Pressing die, 65A, 65B …… Eccentric squeeze roll.

Claims (1)

[Claims] 1. A raw material pipe is pressed and compressed in a radial direction by a pressing die while gripping both ends of the raw material pipe with a chuck and applying a tensile force equal to or higher than a yield point or proof stress corresponding to the raw material pipe material. Then, by repeating this operation, the raw material pipe is formed in a tapered shape or a stepped shape, a manufacturing method of a reduced diameter pipe.