JPH0357510A - Manufacture of inside surface grooved tube - Google Patents

Abstract

PURPOSE:To improve the productivity of the inside surface grooved tube by bringing a tube to be worked, brought to form rolling by a first drawing rate, and thereafter, brought to reduction by a second drawing rate to reduction by a third drawing rate and executing its tube reduction, while suppressing satisfactorily thickening of wall thickness of the tube. CONSTITUTION:By winding of a first capstan drum 8, a tube 2 to be worked is brought to form rolling by a form rolling head 4, and brought to tube reduction by a first drawing rate. Also, by a grooved plug 14, a prescribed groove is formed on the inside surface of the tube 2. Thereafter, it is brought to reduction by a first drawing die 6 and brought to tube reduction by a second drawing rate. Moreover, by winding of a second capstan drum 12, in a state that backward tension is allowed to work by a first capstan drum 8, the tube 2 to be worked is brought to reduction by a second drawing die 10, while suppressing satisfactorily thickening of wall thickness of the tube, and brought to tube reduction by a third drawing rate. In such a way, it is possible not to cause the deterioration of the heat transmission performance caused by thickening of wall thickness of the tube.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for manufacturing an internally grooved tube, and particularly to a technique for improving productivity of an internally grooved tube.

(Background Art) In general, an internally grooved tube, which is a heat transfer tube with a predetermined groove formed on the inner surface, is processed by rolling the tube to a first drawing ratio with a rolling head with a grooved plug inserted inside. After forming a predetermined groove on the inner surface of the pipe to be processed,
The pipe is manufactured by drawing the rolled pipe at a second drawing ratio using a drawing die disposed downstream of the rolling head.

However, with this conventional manufacturing method of internally grooved tubes,
The drawing ratio of the pipe to be processed is not necessarily sufficient, and for this reason, it is necessary to use a pipe with a correspondingly smaller diameter for rolling. There have been circumstances in which the speed, and therefore the production rate of internally grooved tubes, are limited.

On the other hand, in order to eliminate such problems, the pipe to be processed that has been drawn at the second drawing ratio is further subjected to dry drawing at a predetermined drawing ratio to improve the drawing ratio of the pipe to be processed. ,
It has been considered to increase the diameter of the pipe to be rolled to improve the productivity of internally grooved pipes. However, in this case, the wall thickness of the tube to be processed (bottom wall thickness at the bottom of the groove) increases significantly, resulting in problems such as a significant decrease in heat transfer performance of the internally grooved tube as a final product. was there.

In order to avoid such problems, if the groove is formed by thin-wall rolling, taking into account the increase in thickness when forming the groove, the production efficiency will not increase and problems will arise, such as the pipe being processed will break.

(Problem to be solved) The present invention has been made against the background of the above, and the problem to be solved is that the wall thickness (bottom wall thickness) of the pipe to be processed is significantly increased. The pipe to be processed can be shrunk at the third drawing ratio without increasing the wall thickness.
It is an object of the present invention to provide a method for manufacturing an internally grooved tube that can satisfactorily improve the productivity of the internally grooved tube without causing a significant decrease in heat transfer performance.

(Solution Means) In order to solve this problem, in the present invention, from the upstream side to the downstream side in the feeding direction of the pipe to be processed, a rolling head, a first drawing die, a first A capstan drum, a second drawing die, and a second capstan drum are arranged in this order, and the tube to be processed is passed through the rolling head and the first drawing die, and then wound by the first capstan drum. At the same time, the pipe to be processed is paid out from the first capstan drum so that the amount of winding on the first capstan drum is constant, and the pipe is fed out from the first capstan drum. "After passing the processed pipe through the second drawing die, the pipe is wound up by the second capstan drum, and then under the action of a tensile force based on the winding action of the first capstan drum. After rolling the pipe to be processed using the rolling head, shrinking the pipe at a first drawing ratio, and forming a predetermined groove on the inner surface of the pipe using a grooved plug. , the tube to be processed having the groove formed therein is drawn by the first drawing die to be contracted at a second drawing ratio, and further under the action of a tensile force based on the winding action of the second capstan drum. Then, while applying backward tension in the first capstan drum, the pipe to be processed fed out from the first capstan drum is drawn with the second drawing die to obtain a third drawing ratio. This caused the tube to shrink.

(Specific structure/effect) Hereinafter, the present invention will be explained in more detail based on the drawings.

First, FIGS. 1 and 2 schematically show a specific example of an internally grooved tube manufacturing system for manufacturing an internally grooved tube according to the method of the present invention. As shown in FIG. 2, the internally grooved tube manufacturing system for manufacturing an internally grooved tube according to the method of the present invention includes rolling hends 4 and 4, which are arranged in order from the upstream side to the downstream side in the feeding direction of the tube to be processed 2. First drawing die 6, first capstan drum 8
, a second drawing die 10 and a second capstan drum 12.

Here, the rolling head 4 rolls balls and rollers onto the tube to be processed.
The grooved plug 14 is pressed against the outer surface of the pipe 2 to be processed and rolled at a predetermined first drawing ratio, and inserted into the inside of the pipe 2 to be processed.
The first drawing die 6 is used to form a predetermined spiral groove, that is, a spiral fin I6, on the inner surface of the tube to be processed 2, and the first drawing die 6 is used to form a predetermined spiral groove, that is, a spiral fin I6, on the inner surface of the tube to be processed 2. 2 at a predetermined second drawing rate, and the rolling process in the rolling head 4 and the drawing process in the first drawing die 6 are carried out by the first drawing die provided on the downstream side thereof. This is done by the winding action of the pipe to be processed 2 by the capstan drum 8.

Further, the second drawing die 10 provided on the downstream side of the first capstan drum 8 is similar to the first drawing die 6.
The purpose is to further draw the pipe 2 to be processed which has been drawn at a predetermined third drawing rate, and the drawing process at the second drawing die 10 is carried out by drawing at a second This is done by the winding action of the pipe to be processed 2 by the capstan drum l2.

By the way, in order to manufacture a pipe with internal grooves using such a manufacturing system from a raw pipe 2 having a smooth inner surface, the pipe 2 to be processed must be passed through the rolling head 4 and the first drawing die 6.
A predetermined number of times, for example 5.6 times, is applied to the first capstan drum 8.
After winding the tube 2 to be processed by the rotation of the capstan drum 8, it is passed through the second drawing die 10 and wound around the second capstan drum 12, and then the first capstan drum 8 is wound. The pipe to be processed 2 unwound from the second capstan drum 12 is wound up by the second capstan drum 12, and then the second capstan drum 12
The material is then unrolled and sent to the inspection process, etc. Then, a tensile force is applied to the tube to be processed 2 by the winding action caused by the rotation of the first capstan drum 8, and the tube to be processed 2 is rolled and drawn by the rolling head 4 and the first drawing die 6. At the same time, a tensile force is applied to the tube to be processed 2 by the winding action caused by the rotation of the second capstan drum 2, and the tube to be processed 2 is drawn by the second drawing die 10, and at the same time, the caps are drawn. The relative rotational speeds of the stand rams 8 and 12 are adjusted so that a predetermined backward tension is applied to the portion of the pipe to be processed 2 to be drawn by the second drawing die 10. In FIG. 1, reference numeral 18 denotes a tension measuring device that detects the displacement of the degree of warpage of the pipe to be processed 2 and measures the rear tension.
The relative rotational speed of is normally adjusted based on the measurement result of the rear tension measured by such a tension measuring device 18.

If an internally grooved tube is manufactured in this manner, the tube to be processed 2 is rolled by the rolling head 4 at the first reduction rate by the winding action of the first capstan drum 8, and then A predetermined spiral groove (fin 16
) can be shaped in the same way as before, and the pipe to be processed 2 that has been rolled with the rolling head 4 is drawn with the first drawing die 6 at the second drawing rate in the same manner as before. In addition, the pipe to be processed 2 drawn by the first drawing die 6 can be passed through the second drawing die 1.
0 allows for further drawing processing at a third drawing ratio to further shrink the tube. At this time, the wall of the tube to be processed 2 is reduced based on the rear tension applied to the tube to be processed 2. By effectively suppressing plastic flow in the radial direction, the pipe to be processed 2
This makes it possible to effectively suppress the increase in tube wall thickness (bottom wall thickness of the spiral groove).

9 As described above, according to the method of the present invention, the pipe to be processed 2 is shrunk at the first drawing ratio in the rolling head 4 and then shrunk at the second drawing ratio in the first drawing die 6. , the second drawing die 1
0, it is possible to further shrink the pipe at the third drawing ratio while suppressing the increase in the pipe wall thickness to produce an internally grooved pipe, which results in a significant decrease in heat transfer performance. By increasing the diameter of the tube to be processed 2 (original tube) during rolling processing, the rolling speed of the tube to be processed 2 is increased, thereby increasing the productivity of the internally grooved tube that is the final product. It is possible to improve the situation.

Further, according to the method of the present invention, as described above, the rolling process by the rolling head 4, the first drawing process by the first drawing die 6, and the second drawing process by the second drawing die 10 are performed. Since these steps can be performed on the same line, there is an advantage that the manufacturing system for the tube with an inner surface M can be greatly simplified compared to a case where these steps are performed on separate lines.

Here, a drawing mechanism consisting of a drawing die (10) and a capstan drum (I2) is simply provided on the downstream side of the first capstan drum 8, and the pipe to be processed 2 is contracted in three stages. However, by providing two or more sets of drawing mechanisms like the above example on the downstream side of the first capstan drum 8, the pipe to be processed 2 is compressed in four or more stages. It may also be arranged as a tube.

Hereinafter, in order to clarify the present invention more specifically,
Although examples of the present invention are shown, the present invention is not limited in any way by the description of such examples, and the present invention may be implemented in other embodiments without departing from the spirit thereof. should be understood.

(Example) Using a ball pressing type rolling hend 4 that rolls the pipe 2 to be processed with balls and a W-shaped drawing die 610,
An internally grooved pipe manufacturing system as shown in Fig. 1 was constructed.

In such an inner surface iM4/j tube manufacturing system, the drawing ratio (third drawing ratio) in the second drawing die 10 is changed to 12%, 20%, and 25%, and the breaking force of the pipe to be processed 2 is changed. An internally grooved tube is manufactured by changing the ratio of the rear tension (=back tension/breaking force) to each breaking condition, and at that time, the ratio of the to-be-processed tube 2 before and after drawing with the second drawing die 10 is Pipe wall thickness (bottom wall thickness of spiral groove): The amount of change in tf was measured. The measurement results are shown in FIG.

The outer diameter of the pipe to be processed 2 before drawing with the second drawing die 10 (after drawing with the first drawing die 6) is 7.
．． 94 mm, tube wall thickness: tf is 0. 3 1 m
It was m.

From the measurement results shown in FIG. 3, when the drawing ratio of the second drawing die 10 is set to around 10%, the rear tension/breaking force is relatively wide from about 0.1 to 0.6. Within this range, the amount of increase in the pipe wall thickness (Lf) of the pipe to be processed 2 is approximately 1/2 or less (approximately 0.005 mm or less) of that in the case of simple dry drawing (backward tension/rupture force 10). It is recognized that this can be suppressed, and even when the drawing ratio in the second drawing die 10 is set to around 20%, the rear tension/breaking force is 0. In the range of about 1 to 0.3, the amount of increase in 11 pipe wall thickness: tf of the pipe to be processed 2 is approximately 1 in the case of simple dry drawing.
It is recognized that it can be suppressed to about /2 or less (about 0.01 mm or less). From this, the method of manufacturing internally grooved pipes according to the present invention can suppress the deterioration of heat transfer performance due to the increase in the pipe wall thickness tr, while increasing the drawing ratio of the pipe to be processed 2. It has now been recognized that the productivity of internally grooved tubes can be greatly improved.

Furthermore, FIG. 4 shows the results of measuring the amount of change in the height of the fins 16 before and after drawing of the pipe 2 to be drawn, which has been drawn as described above. Of course, when the drawing ratio of the drawing die 10 is relatively small, around IO%, and even when it is relatively large, around 20%, the rear tension/breaking force O. 1~0. It is recognized that the amount of decrease in fin height can be suppressed to a sufficiently small value within a range of about 3.3, and therefore, according to the inventive method, the decrease in heat transfer performance due to decrease in fin height can be sufficiently suppressed. What is done is l'2 fi6.

On the other hand, the outer diameter = Do is 1. 9 n++n, tube wall thickness:
A circular tube with L of 0.13 I2 and 36 mm was used as the original tube of the tube to be processed 2, and using the internally grooved tube manufacturing system constructed as described above, the apex angle was 56 degrees and the height was 0. 1 5 mm fin 16
60 stripes are formed on the inner surface of the tube with a lead angle of 8 degrees.
An internally grooved tube with a tube outer diameter of 7 mm and a tube wall thickness: tf of 0.27 mm was manufactured. At that time, the drawing speed of the processed tube (inner grooved tube) 2 from the second drawing die 10 was measured, and the drawing speed was 48 m/min, and a similar inner grooved tube was manufactured using the conventional method. Pulling speed (
40 m/min), it was confirmed that the productivity could be improved by about 20%.

The feed rate, outer diameter, and tube wall thickness (5u) of the processed tube 2 in each region I to ■ shown in FIG. 1 are as shown in Table 1 below, and the second drawing die It was observed that the amount of increase in tube wall thickness: tf due to the drawing process at 10 mm was suppressed to 0.1 mm. Further, the drawing ratios (first to third drawing ratios) at each processing position are as shown in Table 2 below.

14 1.11 (Effect of the invention) As is clear from the above explanation, if the method of the present invention is followed,
After being rolled at the first drawing rate, the pipe to be processed is drawn at the first drawing rate, and the thickness of the pipe wall (bottom wall v- at the bottom of the groove) is suppressed in an appropriate manner. At the same time, it is possible to further shrink the tube by drawing at the third reduction rate (5). This results in the effect that the productivity of pipes can be improved satisfactorily.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing an example of an internally grooved tube manufacturing system suitable for implementing the method of the present invention, and FIG. 2 shows a more concrete version of the system shown in FIG. It is an explanatory diagram. FIG. 3 is a graph showing an example of the measurement results of the amount of change in the wall thickness of an internally grooved tube manufactured according to the method of the present invention before and after drawing with the second drawing die, and FIG. 3 is a graph showing an example of a measurement result of the amount of change in fin height. 2: Pipe to be processed 4: Rolling head 6: First drawing die 8: First capstan drum 10: Second drawing die 12: Second capstan drum 16 l4: Grooved plug 16: Fin

Claims (1)

[Claims] From the upstream side to the downstream side in the feeding direction of the pipe to be processed, a rolling head, a first drawing die, a first capstan drum, a second drawing die, and a second capstand. The rams are arranged in order, and after the tube to be processed passes through the rolling head and the first drawing die, it is wound on the first capstan drum, and the winding on the first capstan drum is The to-be-processed tube was let out from the first capstan drum so that the applied amount was constant, and the to-be-processed tube let out from the first capstan drum was passed through the second drawing die. Thereafter, the tube to be processed is rolled by the rolling head under the action of a tensile force based on the winding action of the first capstan drum so as to be rolled by the second capstan drum, After shrinking the pipe to be processed at a first reduction rate and forming a predetermined groove on the inner surface of the pipe using a grooved plug,
The pipe to be processed in which the groove has been formed is drawn by the first drawing die to be contracted at a second drawing ratio, and further under the action of a tensile force based on the winding action of the second capstan drum. , while applying backward tension in the first capstan drum, the pipe to be processed that is fed out from the first capstan drum is drawn with the second drawing die, and is drawn at a third drawing ratio. A method for manufacturing an internally grooved tube, characterized by shrinking the tube.