JP2002102916A - Method for manufacturing inside grooved tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an inside grooved tube capable of improving productivity of the inside grooved tube with high thermal performance, without causing a damage on the grooved plug and capable of making the best possible use of the resources. SOLUTION: A floating plug 2 and a grooved plug 4 connected through a coupling rod 3 to the floating plug 2 are inserted into a metal tube 1, and the metal tube 1 is drawn out through holding dies 9, 7, 8 and in the method for manufacturing the inside grooved tube which forms a plurality of grooves inside the metal tube by pressing the metal tube 1 to the grooved plug 4 through the pressing means 5, 6 during the drawing process, strength of the grooved plug 4 is improved by using a cemented carbide as a material of the grooved plug 4 and the damage on the grooved plug 4 can be restrained.

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 grooved tube having an inner surface, and more particularly to a method for reducing chipping of a grooved plug when manufacturing a metal tube having a groove formed on an inner surface by a rolling method. The present invention relates to a method for manufacturing an inner grooved pipe.

[0002]

2. Description of the Related Art Heat exchangers such as metal tubes are used for heat exchangers such as air conditioners and refrigerators. The heat transfer tube causes the refrigerant that changes phase to flow in the tube and exchanges heat with the fluid outside the tube, thereby causing the refrigerant to evaporate or condense. For example, in a heat exchanger such as a room air conditioner, an inner grooved heat transfer tube (an inner grooved tube) having a spiral continuous groove on an inner surface thereof in order to promote heat conduction by evaporation and condensation of a refrigerant in the tube. ) Is used. The inner grooved pipe includes a seamless type and a seam type. As a seamless type manufacturing method, for example, JP-A-54-37059, JP-A-6-15345, and JP-A-4-266417 (Japanese Patent No. 2756)
192). Manufacturing methods common to these publications will be described below.

FIG. 3 shows a method for manufacturing an inner grooved tube. The metal tube 1 is passed through holding dies 9 pressing means 5 and 6 and drawing dies 7 and 8. The floating plug 2, the connecting rod 3 connected to the floating plug 2, and the grooved plug 4 connected to the rear end of the connecting rod 3 are inserted into the metal tube 1 and moved, thereby moving the floating plug 2.
Is held by the holding die 9, and the grooved plug 4 is set at a position facing the pressing means 5, 6. Around the grooved plug 4, pressing means 5, 6 composed of a plurality of planetary-rotating rolls, balls and the like are disposed, and the outer circumference of the metal tube 1 passing through the opposing position by the pressing means 5, 6 is provided. The surface is pressed against the grooved plug 4, and a continuous groove is formed on the inner surface of the metal tube 1. Further, the metal tube 1 is emptied by the drawing dies 7, 8 arranged at the subsequent stage of the contraction means 5, 6, whereby the metal tube 1 is finished to a predetermined outer diameter.

FIG. 4 shows details of the grooved plug 4 shown in FIG. As shown in FIG. 4A, the grooved plug 4 is
Grooves 10 for processing with grooves (for forming fins) having an angle β with respect to the axis X are provided on the outer peripheral surface at a predetermined pitch. As shown in FIG. 4B, the grooved plug 4 has an angle α formed by the groove side surface 11, an opening W2, and the groove 1
The groove is machined so that the groove depth of 0 becomes Hf. Groove 10
The width of the protrusion 12 left between the grooves 10 without being processed is W
It becomes 3.

In recent years, from the viewpoint of improving the heat transfer performance, the fin height in the heat transfer tube with inner grooves has been increasing, and the angle formed by the side surfaces of the fins (= the angle α formed by the groove side surfaces 11) has become smaller. . Accordingly, in the grooved plug 4, the groove 10 corresponding to the fin in the inner surface grooved pipe is deepened, and the angle α is also reduced. In such processing, since the fins of the inner surface grooved heat transfer tube are formed at a predetermined height, the suppression of the grooved plug 4 is increased, and the protrusion 1 of the grooved plug 4 is formed.
That is, a so-called plug chipping in which a part of the plug 2 is missing easily occurs.

FIG. 5 shows an example of chipping of the plug, in which the projection 12 of the grooved plug 4 is missing from the groove bottom. The chipping of the plug is caused by an increase in the load applied to the protrusion 12. This will be described with reference to a grooved plug having the shape shown in Table 1. Here, two types of grooved plugs A and B are put in a metal tube (copper tube), and the outer surface of the copper tube is compressed to reduce the compression load and the height of the fin formed on the inner surface of the copper tube. investigated.

[0007]

[Table 1]

FIG. 6 shows the grooved plugs A, [Table 1].
The relationship between the height (mm) of the fin and the load (kN) by B is shown. The groove opening width W2 decreases as the angle α of the groove 10 decreases, and the heat transfer performance improves as the angle α decreases. W2 / (Hf × W3) indicating the shape ratio for both grooved plugs A and B
Is small, the compressive load for forming the fin at the target height increases as shown in FIG. This is because when the groove depth Hf and the plug protrusion width W3 are the same and the groove opening width W2 is small, the grooved plug 4 having a small groove opening width W2 is used even if the fin height of the heat transfer tube is the same. Means that the load for pressing the copper tube (metal tube 1) against the grooved plug 4 increases. That is, in the case of a high-performance heat transfer tube of a type having a small fin tip angle, the load pressing against the grooved plug 4 becomes high during the groove forming process.

[0009]

However, according to the conventional method for manufacturing an inner grooved pipe, in the case of a grooved plug having a small W2 / (Hf × W3), the pressing pressure applied to the grooved plug is high, and Since the pressing force is applied by the rotation of the pressing means 5 and 6, a large load is applied to the groove side surface 11 of the grooved plug 4 when the material flows into the groove. As a result of this load, the protruding portion 12 of the grooved plug 4 receives a bending force, and as a result, a tensile force acts on the bottom of the groove 10, which leads to chipping of the plug, causing disconnection and defective products, and lowering productivity. As a result, effective use of resources cannot be achieved. When the angle α is reduced by making the groove 10 of the grooved plug 4 deep, the groove 10
Since the flow of the material into the pipe becomes worse and it becomes difficult to set the fin of the inner surface grooved pipe to a predetermined height, workability is reduced and productivity is deteriorated.

Accordingly, an object of the present invention is to provide a method of manufacturing an inner grooved tube capable of improving the productivity of an inner grooved tube having high heat transfer performance and effectively utilizing resources by eliminating the plug chipping of the grooved plug. Is to do.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a floating plug and a grooved plug which is connected to the floating plug via a connecting member and which uses a cemented carbide as a material. A plurality of grooves are formed on the inner surface of the metal tube by pressing the metal tube against the grooved plug by pressing means in a process of inserting the metal tube into the tube and pulling out the metal tube. And a method for producing the same.

According to this method, since the plurality of grooves are formed on the inner surface of the metal tube using the grooved plug using a cemented carbide as a material, the strength of the grooved plug is increased by the cemented carbide. Also, the chipping of the grooved plug is prevented. Eliminating the lack of plugs can reduce disconnection and product defects, improve productivity, and achieve more efficient use of resources.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings. Method for manufacturing inner grooved pipe of the present invention
Is the same as the conventional manufacturing method described with reference to FIG.
The description is omitted here. The present inventors have proposed a grooved plug 4
Of the plug can be reduced, and the occurrence of plug chipping can be suppressed.
Various investigations were made on plug materials. As a result,
Some tungsten carbide (WC) has a particle size of 0.5μ
m or less, anti-deposition force is 3,400 N / mm^TwoAbove, tensile strength
Is 1,900 N / mm^TwoAbove and a compressive strength of 4,20
0N / mm ^TwoBy using a cemented carbide having the above
And found good results. With plug material
And the grooved plastic of the present invention using the above cemented carbide (material b)
Of the grooved plug with the conventional plug material (material a)
Table 2 shows the mechanical characteristics. From [Table 2]
As can be seen, the grooved plug of the present invention is a conventional grooved plug.
Higher precipitation resistance, tensile strength, and compressive strength than
The particle size of tungsten carbide (WC) is small
You can see that

[0014]

[Table 2]

Next, the dimensions of the grooved plug 4 are set as shown in [Table 3], and the material of the grooved plug 4 is the material b shown in [Table 2].
And material a. Using this grooved plug 4, a change in the pressing load when fins were formed on the inner surface of the metal tube 1 was measured.

[Table 3]

FIG. 1 shows the relationship between the fin height and the ratio of the indentation load of the present invention and the conventional grooved plug using the grooved plug 4 shown in [Table 3]. As is clear from FIG. 1, the grooved plug of the present invention (characteristic indicated by a dashed line) has a breaking load (Wb).
On the other hand, the ratio (Wf / Wb) of the indentation load (Wf) when forming at the target fin height is smaller than that of the conventional grooved plug (solid line). This indicates that the plug of the present invention is harder to break than the conventional plug.

Table 4 shows the shapes of the grooved plugs of the prior art and the present invention and the rate of occurrence of chipping of the plugs according to the materials shown in Table 2.

[Table 4] Here, the plug chipping rate is determined for each shape (plug numbers P1 to P
7) Number of plugs (Nt) used for processing the inner grooved tube =
For 50 plugs, the number of plugs (N
P) (NP / Nt). As is clear from Table 4, the conventional grooved plug has a shape ratio ｛= W2
When / (Hf × W3)} is 5 or less, plug missing occurs. On the other hand, the grooved plug of the present invention did not show any chipping of the plug regardless of the shape ratio.

FIG. 2 shows the characteristics of the occurrence of chipping of the conventional grooved plug shown in Table 4. FIG. 2 is created based on the plug numbers P2 to P5 in [Table 4]. It can be seen that when the shape ratio W2 / (Hf × W3) becomes 5 to 5.5 or less, the plug chipping rate becomes significant, and as the value of W2 / (Hf × W3) decreases, the plug chipping rate increases. However, according to the grooved plug 4 of the present invention, 5.0.
The following specification of W2 / (Hf × W3) can also be recommended.

In the above, the method of manufacturing the grooved plug of the inner surface grooved tube has been described. However, embossing is performed by a grooved roll, and after forming the rolled material, the grooved method is manufactured by welding. The present invention is also applicable to rolls.

[0020]

As is apparent from the above, according to the present invention, the floating plug and the grooved plug connected to the floating plug via the connecting member are inserted into the metal tube, and the process of pulling out the metal tube is performed. In the method for manufacturing an inner grooved tube in which a plurality of grooves are formed on the inner surface of the metal tube by pressing the metal tube against the grooved plug by pressing means, since a cemented carbide is used as a material of the grooved plug,
Since the strength of the grooved plug is enhanced and the plug of the grooved plug is prevented from being chipped, disconnection and defective products are reduced, productivity can be improved, and more effective use of resources can be achieved. . In particular, in the production of heat transfer tubes with high heat transfer performance, costs can be reduced by improving productivity, so that ultimately, high-performance air conditioning equipment can be provided at low cost, and furthermore, the preservation of the global environment Also contributes.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing characteristics of a ratio of a fin height to a pushing load in a grooved plug of the present invention and a conventional grooved plug.

FIG. 2 is a characteristic diagram showing a plug chipping occurrence rate in a conventional grooved plug.

FIG. 3 is a sectional view of a manufacturing apparatus showing a method for manufacturing an inner grooved pipe.

FIG. 4 is a front view showing the grooved plug shown in FIG. 3;

FIG. 5 is a photograph showing an example of a missing plug.

FIG. 6 is a characteristic diagram showing a relationship between a fin height and a load in the grooved plug of the present invention (plug A) and the conventional (plug B).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal tube 2 Floating plug 3 Connecting rod 4 Plug with groove 5, 6 Contraction means 7, 8 Drawing die 9 Holding die 10 Groove

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hideto Omoto 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Within Hitachi Cable Co., Ltd. F-term in Tsuchiura Works Co., Ltd. (reference) 4E096 EA18 FA02 FA03 FA18 FA24 FA30 GA03 HA16

Claims (4)

[Claims] 1. A floating plug and a grooved plug which is connected to the floating plug via a connecting member and which uses a cemented carbide as a material are inserted into a metal tube, and a pressing means is used in a process of pulling out the metal tube. A method for manufacturing an inner surface grooved tube, wherein a plurality of grooves are formed on an inner surface of the metal tube by pressing the metal tube against the grooved plug. 2. The cemented carbide has tungsten carbide (WC) as a main component having a particle size of 0.5 μm or less, a cohesive strength of 3,400 N / mm 2 or more, and a tensile strength of 1,900.
The method for producing an inner grooved pipe according to claim 1, wherein the compression strength is not less than N / mm2 and the compression strength is not less than 4,200 N / mm2. 3. The grooved plug has a groove opening length of W
2. The value of W2 / (Hf × W3) is 5 or less, where the groove depth is Hf and the length of the outer peripheral surface of one grooved plug projection is W3. Method for manufacturing an inner grooved pipe. 4. A step subsequent to the drawing step, wherein a metal pipe having a groove formed on an inner surface is subjected to an empty drawing process with a working degree of 35% or less to form a target outer diameter of an outer diameter of 10 mm or less. The method for manufacturing an inner grooved pipe according to claim 1, further comprising: