JPH0342112A - Manufacture of tube having grooves on inside surface - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Technical Field) Does the present invention cover the inside? The present invention relates to a method of manufacturing an I4-equipped tube, and particularly to a technique for improving the productivity of an inner-grooved tube with a simple device configuration.

(Background technology) An internally grooved tube as a heat transfer tube with a spiral groove formed on the inside is rolled at -m with a grooved plug inserted inside the tube to be processed. Manufactured by processing. However, simply rolling the pipe to be processed with a rolling head does not achieve a sufficient tube shrinkage rate, and it becomes necessary to roll the pipe with a small diameter, which significantly limits the rolling speed. be done.

Therefore, some proposals have been made to perform rolling on the pipe to be processed in a relatively large-diameter state, and then perform so-called dry drawing on the pipe to reduce its outer diameter to the desired size. ing.

However, since the conventional dry drawing after the rolling process of the pipe to be processed is simply performed using one die, the wall thickness of the pipe to be processed (bottom of the spiral groove) There is a problem that the pipe wall thickness (bottom wall thickness) is significantly thicker than before dry drawing, and as a result,
When rolling the pipe to be processed, it is necessary to roll the pipe so that the pipe wall thickness becomes thinner than the product target value by the increase in thickness due to dry drawing. There is a problem that the rolling speed decreases and the productivity of the internally grooved tube decreases.

On the other hand, in order to eliminate such problems, during the above-mentioned dry drawing, a rear tension is mechanically applied to the pipe to be processed using a drive roll or a drive gear table, and the workpiece is subjected to the mechanical rear tension. Dry drawing of processed pipes is also being considered. By dry-drawing the pipe to be processed under the action of rear tension, the increase in wall thickness of the pipe can be effectively suppressed or prevented. By adopting this method, it is possible to improve the rolling speed, thereby improving the productivity of the internally grooved tube.

However, with this method, the cost of the device for applying backward tension to the pipe to be processed is high, the overall configuration of the drawing device is large-scale, and it is difficult to control the backward tension when the drawing speed fluctuates. There was a problem in that it was difficult to control the wall thickness to a constant value, which could not be said to be desirable.

It is also known that a plug mandrel is used to draw and shrink a rolled pipe without applying backward tension to the pipe. Although it is easy to control the tube wall thickness using the tube shrinking method for processed pipes, there is a problem in which the drawing speed during drawing processing is significantly reduced, especially when the pipe to be processed has a small diameter, and depending on the conditions, There is a problem that such a method cannot be adopted in some cases, and it is significantly inferior to the empty drawing method.

(Problem to be solved) The present invention has been made against the background of the above-mentioned circumstances, and the problem to be solved is to dry-draw a pipe to be processed after rolling. An internally grooved tube that effectively suppresses or prevents the increase in wall thickness of the pipe to be processed when shrinking the tube with a simple device configuration, thereby advantageously improving the productivity of the internally grooved tube. The objective is to provide a method for manufacturing pipes.

(Solution Means) In order to solve this problem, in the present invention, a predetermined spiral groove is formed on the inner surface of the pipe to be processed using a grooved plug and a rolling hend, and then arranged in series. The pipe to be processed is continuously drawn using a plurality of dies, and the outer diameter of the pipe to be processed is reduced in stages while suppressing an increase in the wall thickness of the pipe. be.

(Specific configuration and operation) The present invention will be explained in more detail below with reference to the drawings.

That is, according to the present invention, as shown in FIG.
And the grooved plug 6 is used to perform rolling processing in the same manner as in the conventional method. In this rolling process, the pipe to be processed 2 is shrunk at a predetermined shrinkage ratio, and at the same time, spiral fins 8, that is, helical grooves, are formed on the inner surface of the pipe.

In addition, in FIG. 1, IO is a floating plug that shrinks the pipe to be processed 2 by a predetermined amount between it and a die 12 provided on the upstream side of the rolling head 4, and the tie rod 14
It is connected to the mounting plug 6 via the mount plug 6, and serves to hold the mounting plug 6 at a constant E'L:fj.

In addition, here, as 7.do.1 for rolling, the to-be-processed pipe 2
Although a type of rolling head that presses balls 16 against the outer surface of the tube 2 to be processed is used, it is also possible to use a type of rolling head that presses rollers against the outer surface of the tube 2 to be processed.

Next, the wave force pipe 2 which has been rolled as described above is
As shown in FIG. 2, at least two dies 18 (here, 6
(1 day is shown) is used for dry drawing at around j, and the diameter is reduced stepwise to the desired final outer diameter. In this way, an internally structured pipe with a desired outer diameter is manufactured.

In this way, a plurality of dies 18 having different molding dimensions are used.
If the pipe to be processed 2 after rolling is drawn continuously and stepwise in the same line using The pulling force at 18 acts on the tube 2 to be processed as a rear tension force, which affects the flow of the tube material in the radial direction during the process.
Compared to the conventional case where the pipe to be processed 2 is drawn using a single die, the wall thickness of the pipe to be processed 2 (wall thickness at the bottom of the spiral groove; bottom wall thickness) is increased. The wall thickness can be significantly reduced, and the wall thickness of the tube 2 to be processed can even be reduced. Therefore, during rolling processing, it has become possible to set the wall thickness of the pipe to be processed 2 larger than before, and it has become possible to further increase the rolling processing speed. This made it possible to improve the productivity of internally grooved tubes.

According to the method of the present invention, as described above, by simply using a plurality of dies 18, the increase in the tube wall thickness or the decrease in the tube wall thickness when the tube to be processed 2 is contracted after the rolling process is suppressed. Since this can be achieved by simply continuously empty drawing the pipe 2 to be processed, the equipment cost is lower and more compact than when mechanically applying rear tension to the pipe 2 to be processed. It has become extremely easy to manufacture and maintain.

According to the method of the present invention, the rear tension during dry drawing with each die 18 and the rate of change in the wall thickness of the pipe to be processed 2 due to dry drawing are determined by the number of dies 18 used,
It is possible to control over a relatively wide range based on the combination of the tube contraction rate of the pipe to be processed 2 at each die 18 or the shape of each die 18, and the rate of change can be controlled at each die 18. Since this can be stably achieved by controlling the lubrication conditions at a constant level, there is also the advantage that the tube wall thickness can be easily and extremely stably controlled to a desired thickness.

In addition, in the method of the present invention, the die 18 whose molding dimensions have changed due to wear can be reused with corrected dimensions, except for the one with the maximum molding dimension, so in this sense as well, it is economical. There are advantages such as being advantageous.

Incidentally, FIGS. 3 and 4 each have an outer diameter of 15.
Using a circular pipe with a diameter of 88 mm and a wall thickness of 0.665 mm as the pipe to be processed 2, the number of dies 18 used was varied from 1 to 6 stages to dry draw the pipe to be processed, and the result of the dry drawing was When,
This figure shows the results of measuring the relationship between the shrinkage ratio of the pipe 2 to be processed and the pull-out load, as well as the relationship between the shrinkage ratio and the wall thickness of the pipe 2 to be processed, and as is clear from these figures. If a plurality of dies 18 are used, the rate of increase in the wall thickness of the pipe to be processed 2 can be significantly suppressed compared to the case where only one die 18 is used. In such a case, the wall thickness of the tube 3 to be processed can even be reduced. From this, when a pipe with internal grooves provided with spiral fins 8 on the inner surface is used as the pipe to be processed 2, and the pipe to be processed 2 is subjected to dry drawing with two or more dies 18, the pipe to be processed is It is easily inferred that the rate of increase in the bottom wall thickness at the bottom of the spiral groove of the pipe to be processed 2 can be significantly reduced or reduced compared to the case where the pipe 2 is simply drawn with one die 18. It is.

In addition, FIG. 5 shows a pipe to be processed (inner surface) equipped with a spiral 14 (fin 8) on the inner surface by empty drawing according to the present invention, more precisely, by empty drawing using a six-stage die 8. )I
7゜0 mnn from the outer diameter of 9.52 m
The measurement results of the bottom t, ] thickness, fin height, and total wall thickness (bottom wall thickness + fin height) of the J Loe tube 2 when the tube is shrunk to the outer diameter of are measured using a single die 18. As is clear from the figure, when only a single die 18 is used, the bottom wall thickness of the pipe to be processed 2 becomes significantly larger. Although this is unavoidable, in the case of dry drawing according to the present invention using a six-stage die 18, only the outer diameter of the pipe to be processed 2 can be changed without changing the bottom wall thickness or the fin height. It has been recognized that tube contraction can be achieved effectively.

Although the present invention has been described in detail above, the present invention is not limited in any way by the above description, and may be implemented in modes other than the above without departing from the spirit thereof.
Of course.

For example, the pipe to be processed may be a pipe of different diameters such as an elliptical pipe, and a die 18 with seven or more stages may be used during dry drawing after rolling. There is no problem.

(Effect of completeness) As is clear from the above description, the present invention uses a rolling head and a grooved plug to create a spiral groove (helical fin) on the inner surface of the tube.
When shrinking the pipe to be processed to the desired dimensions, the pipe to be processed is continuously drawn using a plurality of dies arranged in series. The tube to be processed can be effectively reduced while suppressing or preventing the wall thickness of the processed tube from increasing in thickness. Therefore, by increasing the thickness of the tube to be processed, rolling The rolling speed during rolling can be made higher than before, and the productivity of the internally grooved tube can be advantageously improved. Moreover, according to the method of the present invention, the tube wall thickness of the final product can be accurately maintained at a constant value by simply controlling the lubrication of each die at a constant level during dry drawing, making it possible to control the tube wall thickness. It also has the advantage of being extremely easy.

[Brief explanation of drawings]

FIG. 1 is an explanatory sectional view for explaining the rolling process of the method of the present invention, and FIG. 2 is an explanatory sectional view for explaining the dry bow drawing process. FIG. 3 is a graph showing the fluctuation state of the drawing force of the circular tube during dry drawing due to the change in the number of dies used.
The figure is a graph showing how the wall thickness of a circular tube changes during dry drawing as the number of dies used changes. FIG. 5 compares the variation in the wall thickness of a pipe with internal groove 1 that was dry drawn according to the method of the present invention and the variation in the wall thickness of a pipe with internal grooves that was dry drawn according to the conventional method. This is a graph shown as follows. 2: Processed pipe 4: Rolling head 6: Grooved plug 8: Fin 18: Die

Claims (1)

[Claims] After forming a predetermined spiral groove on the inner surface of the pipe to be processed using a grooved plug and a rolling head, the pipe to be processed is continuously drawn using a plurality of dies arranged in series. A method for manufacturing an internally grooved tube, characterized by reducing the outer diameter of the tube to be processed in stages while suppressing an increase in the wall thickness of the tube.