JP3106424B2 - Manufacturing method of small-diameter inner grooved pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a micro heat pipe for cooling electronic equipment and a small-diameter inner grooved pipe used for a small heat exchanger such as an air conditioner and a refrigerator.

[0002]

2. Description of the Related Art In recent years, high-density mounting of electronic devices and miniaturization of semiconductors have been rapidly progressing, and it has become an urgent need to solve the problem of heat dissipation accompanying the high-density mounting. Accordingly, a micro heat pipe using a small-diameter inner grooved pipe has been developed because it is advantageous in terms of good heat dissipation from the substrate to the outside and cost. In addition, even in an air conditioner in which miniaturization and high efficiency are conventionally promoted by using an inner grooved pipe, there is a tendency to use an inner grooved pipe having a smaller diameter because of environmental and energy saving problems. Japanese Patent Application Laid-Open No. Sho 62-9820 discloses a method for manufacturing such a small-diameter inner grooved tube.
No. 0 and Japanese Patent Application Laid-Open No. 1-29707 have proposed a method of improving productivity by performing a large-size drawing / drawing after groove processing.

[0003]

However, in the case where the drawing is performed after the groove forming process as in the prior art, the pipe is elongated in the longitudinal direction by the drawing process, and the inner groove processing surface is also extended at the same time, as shown in FIG. A fin break 4 occurs at the projection. In addition, cracks called "cracks" as shown in 5 of FIG. 3 also occur on the outer surface of the tube. The fin breakage causes a decrease in the heat transfer performance of the inner surface of the tube, and a poor outer surface of the tube causes a problem that the tube leaks even at a low pressure. The present invention has been made as a result of examining the above problem, and has developed a manufacturing method capable of obtaining a small-diameter inner grooved tube free from fin cuts and outer surface defects.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a helical or continuous groove is formed in a pipe inner surface by rolling or drawing using a grooved plug, and once or twice.
In the method for producing a small-diameter inner grooved tube in which drawing is performed more than once, after forming a groove, heat annealing is performed, and the diameter is reduced by 30 to 80% by one or more times of drawing. A method for producing a small-diameter inner grooved pipe, wherein the heat annealing is performed at 200 to 800 ° C. for 30 minutes to 2 hours.
Time is preferable, and in order to further reduce the manufacturing cost, the drawing is performed by reducing the diameter by 30 to 50% only once, and the groove is twisted in the pipe axis direction. A method for manufacturing a small-diameter internally grooved pipe, wherein a groove having an angle of 5 ° or more is formed.

[0005]

The material after groove processing using a grooved plug in a metal tube is considerably hardened. Then, a plastic flow from the outer peripheral surface toward the inner peripheral surface remains in the material, and such a tube becomes an extremely uneven wall having a large number of protrusions on the inner surface. For this reason, at the time of drawing drawing, a difference occurs in the circumferential stress per unit area due to a difference in thickness between the projection and the groove, and the inner peripheral surface moves from the outer peripheral surface along the plastic flow generated at the time of groove forming. In addition, it is easy for crackle to occur. In the present invention, the plastic flow in the material can be eliminated by heat annealing the grooved tube before drawing drawing, and since the material is softened, at the time of drawing drawing, the protrusion and the groove are not connected. Even when a circumferential stress difference occurs, the occurrence of cracks from the outer peripheral surface to the inner peripheral surface can be suppressed. Furthermore, since the tube softened by annealing has a smaller drawing force at the time of drawing and drawing than the conventional hardened tube, the elongation of the material in the longitudinal direction of the tube due to drawing and drawing is small, and since the material is soft, the inner surface is The fins of the projections are cut off. In the present invention, the condition of the heat annealing is set at 200 to 800 ° C. for 30 minutes to 2 hours because the tube material does not sufficiently soften at a temperature of less than 200 ° C. and for a time of less than 30 minutes, and at 800 ° C. When the temperature exceeds 2 hours and the temperature exceeds 2 hours, the softening is over and the drawing becomes difficult. In addition, the diameter reduction processing of the above-mentioned drawing is performed by 30 to 80.
The reason why the percentage is set is that if the processing is less than 30%, the production cost is increased. In particular, by performing the drawing process by reducing the diameter by 30% to 50%, it is possible to manufacture a small-diameter inner grooved tube by one drawing process, without increasing the number of steps, and manufacturing costs. Can be suppressed. Furthermore, the reason why the drawing is performed by setting the twist angle to the pipe axis direction to 5 ° or more is that the fin is less likely to be cut when the twist angle is provided, and even if the angle is set, the angle becomes smaller when the drawing is performed. Because.

[0006]

An embodiment of the present invention will be described below.
First, as an example of an apparatus for manufacturing a grooved tube, as shown in FIG. 1, a grooved plug 10 having a floating plug 8 on the inner surface of a raw tube 6 and a die 7 on the outside, and held at a fixed position by the floating plug. And a rolling tool 9 disposed outside the rolling tool. Using this apparatus, an inner grooved pipe (outer diameter 6.0 m) having a projection 2 and a groove 3 shown in FIG.
m, number of grooves 20, groove depth H0.15mm, bottom thickness t0.2
7 mm, helix angles of 0 ° and 5 °). Thereafter, the material softened by annealing at 650 ° C. for 30 minutes, and the material with the grooved hard material, were evacuated by 10 to 80%,
It was a small-diameter inner grooved tube having an outer diameter of 5.4 to 1.2 mm. Then, the occurrence of fin breakage at the inner surface projection at that time was examined. Table 1 shows the results. In the table, the mark ○ indicates that no fin break occurred, and the mark X indicates that fin break occurred.

[0007]

[Table 1]

As is apparent from Table 1, up to an air drawing rate of 30%, a thin pipe with no fin cut can be obtained by applying a twist angle of 5 ° without annealing after grooving. But 4
When the diameter becomes smaller than 1 mm or less, it is understood that annealing is necessary to obtain a tube without fin cut. Especially 2mm outside diameter
For the following, it is effective to have a twist angle of 5 ° at the time of grooving. At this time, 10 to 50
% Reduction processing could be performed by one empty drawing. If the diameter reduction processing of 60% or more was performed by one single drawing, the pipe burst and could not be pulled out.
I went more than once. Next, for an inner grooved tube having an outer diameter of 6.0 mm, a groove number of 20, a groove depth of 0.15 mm, a bottom wall thickness of 0.27 mm, and a twist angle of 5 °, having the same shape as above,
A thin tube having an outer diameter of 3.6 mm was finished by annealing and softening by annealing at 50 ° C. for 1 hour and a hard material with a grooved process, each of which was 1000 m, by only one-time drawing and drawing of 40%. . As a result of examining the number of outer surface defects that occurred at this time, it was found that the hard material with the groove processing was 65/1000 m.
Most of the defects were defective. on the other hand,
What was annealed and softened was 14 pieces / 1000m,
Of these, seven were defective.

[0009]

According to the present invention as described above,
This makes it possible to manufacture a small-diameter inner grooved tube free from fin breakage and defective outer surface, and has an industrially remarkable effect.

[Brief description of the drawings]

FIG. 1 is a schematic view of an inner grooved pipe manufacturing apparatus used in the present invention.

FIG. 2 is a cross-sectional view of an essential part showing an example of a small-diameter inner grooved pipe manufactured according to the present invention.

FIG. 3 is a sectional view of an essential part showing a defect of a small-diameter inner grooved pipe.

FIG. 4 is a developed view showing an inner surface of the small-diameter inner grooved tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat transfer tube 2 Protrusion part 3 Groove part 4 Fin cutout 5 Metal core 6 Base tube 7 Die 8 Floating plug 9 Rolled ball 10 Slotted plug

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-344819 (JP, A) JP-A-4-266417 (JP, A) JP-A-3-42112 (JP, A) JP-A-2- 197551 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B21C 1/22

Claims (4)

(57) [Claims] (1) A helical or continuous groove is formed in the pipe axis direction by rolling or drawing using a grooved plug on the inner surface of the pipe, and then one or two or more times of drawing and drawing are performed. In the method of manufacturing a tube with a radially inner surface groove, after forming a groove, heat annealing is performed, and a diameter reduction of 30 to 80% is performed by one or more times of drawing and drawing. Manufacturing method of inner grooved pipe. 2. The heat annealing at 200 to 800 ° C. for 30 minutes.
2. The method for producing a small-diameter internally grooved tube according to claim 1, wherein the treatment is carried out for a period of minutes to 2 hours. 3. The method for producing a small-diameter inner grooved pipe according to claim 1, wherein the drawing drawing is performed by reducing the diameter by 30 to 50% only once. 4. The groove according to claim 1, wherein the groove has a twist angle of 5 ° or more with respect to the tube axis direction.
Or the method for producing a small-diameter inner grooved pipe according to 3.