JP6964498B2 - Manufacturing method of inner spiral grooved tube, heat exchanger and inner spiral grooved tube - Google Patents

Description

The present invention relates to an inner spiral grooved tube having excellent thermal characteristics and tube expandability, and a method for manufacturing a heat exchanger and an inner spiral grooved tube.

Fin tube type heat exchangers for air conditioners and water heaters are provided with heat transfer tubes for passing refrigerant through the aluminum fin material. The mainstream heat transfer tube is an inner spiral grooved tube provided with a continuous spiral groove on the inner surface in order to improve the heat exchange efficiency with the refrigerant.
Conventionally, copper alloys have been mainly used for heat transfer tubes. However, there is an increasing demand for the development of heat transfer tubes made of aluminum alloy due to the demand for weight reduction, cost reduction and improvement of recyclability.
As a method for manufacturing an inner spiral grooved tube (heat transfer tube) made of a copper alloy, a groove rolling method for rolling a twisted groove on the inner surface of the tube is known. However, in the heat transfer tube made of an aluminum alloy, it is necessary to increase the bottom wall thickness in order to increase the pressure resistance, and it is difficult to manufacture by the groove rolling method.
Further, in the groove rolling method, there is a problem that aluminum slag is generated due to friction between the groove plug and the inner surface of the pipe, and it is difficult to remove the aluminum slag. Therefore, in order to manufacture an inner spiral grooved tube made of an aluminum alloy, a new manufacturing method that replaces the groove rolling method has been required.
In the following Patent Document 1, one of the take-up drum and the rewind drum is supported by a cradle, and the pipe material conveyed between the drums is made of an aluminum alloy that is twisted by a flyer rotating around the one drum. Disclosed is an apparatus for manufacturing an inner spiral grooved tube.

Japanese Unexamined Patent Publication No. 62-240108

In the apparatus for manufacturing an inner spiral grooved pipe described in Patent Document 1, buckling is likely to occur in the pipe material because only torsional stress is applied to the pipe material as the flyer rotates. For this reason, the apparatus for manufacturing an inner spiral grooved pipe described in Patent Document 1 has a problem that even if an attempt is made to process an aluminum alloy pipe material, only a small twist of 10 ° or less can be imparted.
When applying an inner spiral grooved tube made of an aluminum alloy to a heat transfer tube of a heat exchanger, the heat transfer tube is provided in a serpentine manner so as to penetrate a plurality of juxtaposed fins, and the heat transfer tube is expanded as necessary. The fins and heat transfer tubes are joined. For this reason, the heat transfer tube is partially bent with a hairpin with a small radius of curvature. However, since the heat exchanger has been miniaturized in recent years, the pitch of the hairpin bent portion of the heat transfer tube has become smaller. There is a risk of wrinkles and flat parts occurring at the bent part of the hairpin of the heat transfer tube, and in some cases cracks and breaks may occur.

For this reason, the applicant of the present application is developing a technique capable of forming an inner spiral groove having a large twist angle in a pipe material made of an aluminum alloy, and even if it is used as a heat transfer tube of a heat exchanger to form a hairpin bent portion. It is an object of the present invention to provide an inner spiral grooved tube that does not crack or break.

The inner spiral grooved tube, which is one aspect of the present invention, is an aluminum inner spiral groove in which a plurality of spiral grooves along the length direction and a plurality of spiral fins are formed at intervals in the circumferential direction on the inner surface. In the attached pipe, the plurality of spiral grooves and the plurality of spiral fins are all spirally formed in the length direction of the pipe body at the same twist angle, and on the pipe wall of the pipe body, An aggregate having an inclination depending on the twist angle with respect to the length direction is formed , and a spiral weld line is intermittently formed along the length direction of the pipe body on the outer peripheral surface of the pipe body. , A spiral die mark is formed on the outer peripheral surface of the tube body along the length direction of the tube body, and the weld line has 30 pits having a diameter of 10 μm or more when observing in an observation field of 180 μm × 250 μm. The portion included above, the length of the weld line is 5 mm or less, the twist angle of the spiral fin is 15 ° or more and 25 ° or less, and the twist angle of the die mark is 17.5 °. It is characterized in that it is 29.73 ° or less.
In the inner spiral grooved tube which is one aspect of the present invention, the length of the weld line is preferably 1.5 mm or more and 2 mm or less.
In the inner spiral grooved pipe which is one aspect of the present invention, the twist angle of the fin is θ1, the twist angle of the die mark is θ2, the inner peripheral length of the pipe body is α, and the wall thickness of the pipe body is Let β be, and it is preferable to have a relationship of tan θ2 = {(α + 2πβ) tan θ1} / α.

In the present invention, it is preferable that the texture is a preferentially oriented texture in the Cu orientation and the Goss orientation.
In the present invention, it is preferable that the texture is a structure in which Cu orientation {112} < 111 > is integrated and Goss orientation {011} < 100 > is integrated.
In the present invention, the inclined a texture twisting withdrawal texture with an integrated degree of the Cu orientation {112} <111> is smaller than the integrated degree of Cu orientation of the drawn tube {112} <111> It is preferable that it has been done.

In the present invention, it is preferable that a spiral die mark is formed on the outer peripheral surface and the maximum depth of the die mark is 35 μm or less.
In the present invention, it is preferable that the twist angle of the spiral die mark on the outer peripheral surface is 1.0 ° or more larger than the twist angle of the spiral fin.
The heat exchanger of the present invention is characterized by including the inner spiral grooved tube according to any one of the above and a heat sink coupled to the inner spiral grooved tube.

The manufacturing method of the present invention is the method for manufacturing the inner spiral grooved tube according to any one of the above, and has a plurality of fins extending linearly along the length direction on the inner peripheral surface and on the outer peripheral surface. An extrusion molding process in which an aluminum raw tube having a die mark extending linearly along the length direction is extruded, and a torsion drawing step in which the raw tube is drawn and twisted at a twist angle of 15 ° or more. By performing an empty drawing step of drawing out with a diameter reduction ratio of 10% or more after the drawing step, an aggregate structure having an inclination depending on the twist angle on the pipe wall of the raw pipe in the length direction thereof. Is characterized by forming.
In the present invention, it is preferable that the texture is a preferentially oriented texture in the Cu orientation and the Goss orientation.

According to the present invention, large inner surface helical grooves and helical fin twist angle Ri inner surface helical grooved tube der having a tubular member made of aluminum alloy, the inner surface helical grooves having a weld line and a die marks on the outer peripheral surface It is possible to provide a tube with an inner spiral groove that does not cause cracks or breakage even if it is an attached tube and is used as a heat transfer tube of a heat exchanger to form a hairpin bent portion, and a heat exchanger provided with the inner spiral grooved tube. ..

It is a front view of the heat exchanger of an embodiment. It is a partial perspective view of the heat exchanger of an embodiment. It is a cross-sectional view of the inner surface spiral grooved tube of an embodiment. It is a vertical sectional view of the inner surface spiral grooved pipe of an embodiment. It is a side view of the inner surface spiral grooved pipe of an embodiment, (a) is a figure which shows an example of a weld line, (b) is a figure which shows an example of a die mark. It is a vertical sectional view of the raw pipe (straight grooved pipe) in the manufacturing method of embodiment. It is a perspective view of the raw pipe (straight grooved pipe) in the manufacturing method of embodiment. It is a front view which shows the manufacturing apparatus which performs the twisting process in the manufacturing method of embodiment. It is a top view of the floating frame seen from the arrow IX direction in FIG. It is an image taken by a laser microscope of the outer peripheral part of the inner spiral grooved tube, (a) is a part where a weld line remains, and (b) is a part where a weld line disappears. It is a (200) incomplete pole figure for analyzing the crystal orientation of the inner spiral grooved tube obtained in the Example. It is a (220) incomplete pole figure for analyzing the crystal orientation of the inner spiral grooved tube obtained in the Example. It is a (111) incomplete pole figure for analyzing the crystal orientation of the inner spiral grooved tube obtained in the Example. It is a (200) pole figure after correcting the pole figure shown in FIG. 11 by 20 ° in the RD-TD direction. It is a (220) pole figure after correcting the pole figure shown in FIG. 12 by 20 ° in the RD-TD direction. It is a (111) pole figure after correcting the pole figure shown in FIG. 13 by 20 ° in the RD-TD direction. It is a (200) incomplete pole figure for analyzing the crystal orientation of the linear grooved drawing tube created as a comparative example. It is a (220) incomplete pole figure for analyzing the crystal orientation of the linear grooved drawing tube created as a comparative example. It is a (111) incomplete pole figure for analyzing the crystal orientation of the straight grooved drawing tube created as a comparative example. The crystal orientation distribution functions of the inner spiral grooved tube obtained in the examples are 0 °, 25 °, and 45 °. It is explanatory drawing which shows every 90 °. 0 °, 25 °, 45 ° of the inner spiral grooved tube obtained in the examples. It is explanatory drawing which shows the crystal orientation distribution function which added 20 ° correction to the crystal orientation distribution function for every 90 °. 0 °, 25 °, 45 ° of the straight grooved pipe obtained as a comparative example. It is explanatory drawing which shows the crystal orientation distribution function for every 90 °. (A) is an image of an example of the dice mark, and (b) is a measurement graph of the depth of the dice mark. (A) is an image of an example of the dice mark, and (b) is a measurement graph of the depth of the dice mark.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the drawings used in the following description, for the purpose of emphasizing the characteristic parts, the characteristic parts may be enlarged for convenience, and the dimensional ratios of the respective components may not be the same as the actual ones. No. Further, for the same purpose, a part that is not a feature may be omitted in the figure.

[Heat exchanger]
1 and 2 are schematic views of a heat exchanger 80 provided with a heat transfer tube 81 composed of an inner spiral grooved tube according to the first embodiment of the present invention.
The heat exchanger 80 of this embodiment has a structure in which a heat transfer tube 81 is provided in a meandering manner as a tube for passing a refrigerant, and a plurality of aluminum heat sinks 82 are arranged in parallel around the heat transfer tube 81. The heat transfer tube 81 is provided so as to pass through a plurality of insertion holes provided so as to individually penetrate the heat radiating plates 82 arranged in parallel.

In the heat exchanger 80, the heat transfer tube 81 connects a plurality of U-shaped main pipes 81A that linearly penetrate the heat radiating plate 82 and adjacent end openings of adjacent main pipes 81A with a U-shaped elbow pipe 81B. It becomes. Further, the refrigerant inlet portion 87a is formed on one end side of the heat transfer tube 81 penetrating the heat radiation plate 82, and the refrigerant outlet portion 87b is formed on the other end side of the heat transfer tube 81. The heat exchanger 80 is configured. The U-shaped bent portion of the heat transfer tube 81 is a hairpin bent portion, and the U-shaped bent portion of the elbow tube 81B is a hairpin bent portion.

[Inner spiral grooved tube (heat transfer tube)]
Next, the inner spiral grooved pipe (heat transfer pipe) 10 constituting the main pipe 81A and the elbow pipe 81B used in the above-mentioned heat exchanger 80 will be specifically described.
FIG. 3 is a perspective view of a part of the inner spiral grooved pipe 10 of the first embodiment as a cross section, FIG. 4 is a vertical cross-sectional view, and FIG. 5 is a side view.

As the inner spiral grooved tube 10, one made of aluminum or an aluminum alloy can be used. When an aluminum alloy is used for the inner spiral grooved tube 10, the aluminum alloy is not particularly limited, and is represented by a pure aluminum system such as 1050, 1100, 1200 specified by JIS, or 3003 to which Mn is added. A 3000 series aluminum alloy or the like can be applied. In addition to these, any of the 5000 series to 7000 series aluminum alloys specified in JIS may be used to form the inner spiral grooved pipe 10, or an aluminum alloy not specified in JIS may be used. Of course it is good. In addition, in this specification, "aluminum" is a concept including an aluminum alloy and pure aluminum.

The inner spiral grooved tube 10 is composed of a tube body 10A having a circular outer shape in cross section. The diameter of the outer peripheral surface 10a of the tube body 10A is, for example, 4 mm or more and 15 mm or less in the case of a small heat exchanger. A plurality of fins 3 formed spirally along the length direction are provided on the inner peripheral surface 10b of the pipe body 10A. A spiral groove 4 having an inner diameter larger than that of the tip of the fin 3 is formed between the fins 3.

In the present embodiment, for example, 30 to 60 fins 3 are provided in the inner peripheral direction of the pipe body 10A. The height of the fin 3 (that is, the dimension in the radial direction) is 0.1 mm or more and 0.4 mm or less. The bottom wall thickness c of the pipe body 10A (that is, the thickness of the pipe body 10A corresponding to the bottom of the spiral groove 4) is 0.2 mm or more and 0.8 mm or less. The apex angle of the fin 3 (the angle formed by the side surfaces of the fin 3) is 10 ° to 30 °. The twist angle θ1 (twist angle) of the spirally formed fins 3 is 5 ° or more and 45 ° or less.

As shown in FIG. 3, four weld lines WLs arranged at equal intervals along the circumferential direction are provided on the outer peripheral surface 10a of the pipe body 10A. Further, as shown in FIG. 5A, the weld line WL is spirally formed on the outer peripheral surface 10a of the pipe body 10A. The weld line WL is a portion where the materials are merged and welded during extrusion processing. The weld line WL extends in the depth direction from the outer peripheral surface 10a toward the inner peripheral surface 10b side.
The number of weld lines WL is not limited to four. The weld line WL is formed in a portion where billets housed in the apparatus are divided into a plurality of flow paths and pumped and merged in extrusion processing. Therefore, the number of weld lines WL is determined according to the number of flow paths in the extruder.

In the present embodiment, the twist angle θ2 of the spirally formed weld line WL is 10 ° or more and 45 ° or less. As will be described later, in the inner spiral grooved pipe 10 of the present embodiment, a twisting process is applied to a raw pipe 10B (see FIG. 6) having a linear fin 3 and a linear weld line WL. It is formed.

A high-pressure refrigerant of, for example, 12 MPa or more flows inside the inner spiral grooved pipe 10. Therefore, the inner spiral grooved tube 10 is required to have sufficient withstand voltage against the internal pressure. According to the inner spiral grooved tube 10 of the present embodiment, the weld line WL is formed in a spiral shape, so that the pressure resistance strength is increased. When the internal pressure of the inner spiral grooved pipe 10 increases, a stress is applied to the inner peripheral surface 10b of the inner spiral grooved pipe 10 to push the inner spiral grooved pipe 10 radially outward. Therefore, in the inner spiral grooved pipe 10, cracks due to an increase in internal pressure are likely to be formed along the longitudinal direction. On the other hand, the weld line WL tends to be a starting point of a crack because the structure is different from that of other parts. According to the present embodiment, since the weld line WL is formed in a spiral shape, cracks are unlikely to occur along the weld line WL even when the internal pressure is increased. Therefore, it is possible to provide the inner spiral grooved tube 10 having excellent pressure resistance.

The weld line WL of the inner spiral grooved tube 10 draws a spiral with a twist angle θ2. Therefore, the spirally formed weld line WL extends with a sufficient inclination with respect to the length direction of the inner spiral grooved tube 10, which is the direction in which cracks are likely to occur in response to an increase in internal pressure. As a result, it is possible to more effectively suppress the formation of cracks along the weld line WL.

In this embodiment, the spiral weld line WL is formed intermittently along the length direction. That is, a partially interrupted portion is formed in the weld line WL. As described above, the weld line WL is a welded portion between materials when extrusion processing is performed. Therefore, the structure of the weld line WL of the inner spiral grooved tube 10 is different from that of other parts. As will be described later, the inner spiral grooved pipe 10 of the present embodiment is manufactured by repeatedly drawing and twisting a raw pipe formed by extrusion. The weld line WL is mixed with the surrounding structure by being subjected to the processing a plurality of times, and the boundary becomes ambiguous. As a result, the weld line WL partially disappears and becomes intermittent.

According to this embodiment, the weld line WL is formed intermittently. In addition, the portion where the weld line WL has disappeared is mixed with the surrounding tissue and homogenized. Therefore, the strength of the inner spiral grooved tube 10 along the weld line WL can be increased. Thereby, it is possible to provide the inner spiral grooved tube 10 having high pressure resistance.
Further, it is said that the weld line WL is preferentially corroded because a solid solution component is precipitated at the time of formation. According to the present embodiment, since the weld line WL is formed intermittently along the length direction, the corroded portion does not extend continuously, and the decrease in pressure resistance due to corrosion can be suppressed.

The length of each of the intermittently formed weld lines WL is preferably 5 mm or less. By setting the length of each weld line WL to 5 mm or less, the decrease in pressure resistance due to the weld line WL can be effectively suppressed.

When the inner spiral grooved tube 10 is immersed in a 10% nitric acid aqueous solution for 20 seconds and etched, the weld line WL rises like a white streak on the surface. Further, since the white streak-shaped portion is a welded portion, there is a difference in the etching method as compared with other portions, and fine pits are generated. In this state, in the weld line WL, light is scattered and can be identified as a streak-like portion.
FIG. 10 is an image taken by a laser microscope of the outer peripheral portion of the inner spiral grooved tube 10 manufactured by a manufacturing apparatus described later, FIG. 10 (a) is a portion where a weld line remains, and FIG. 10 (b) is a portion. This is the part where the weld line disappeared. As shown in FIG. 10, by etching, fine pits on the outer peripheral portion of the inner spiral grooved tube become apparent. As shown in FIG. 10A, when the outer peripheral surface is observed with a laser microscope, pits having a diameter of 10 μm or more are formed on the weld line. On the other hand, as shown in FIG. 10B, only a few pits having a diameter of 10 μm or more are formed in the weld line disappearance portion.

In the present specification, in the observation in the range of the observation field of view of 180 μm × 250 μm with a laser microscope, the portion including 30 or more pits having a diameter of 10 μm or more is defined as a weld line WL. Therefore, it is considered that the weld line WL has disappeared in the portion where the number of pits having a diameter of 10 μm or more is less than 30.
In the inner spiral grooved tube 10 of the present embodiment, the fins 3 are formed in a spiral shape with a twist angle θ1. On the other hand, as shown in FIG. 5, the weld line WL is formed in a spiral shape with a twist angle θ2. When α is the inner peripheral length of the inner spiral grooved pipe 10 and β is the bottom wall thickness of the inner spiral grooved pipe 10, the twist angle θ1 of the fin 3 and the twist angle θ2 of the weld line WL satisfy the following relationship.

According to the above equation, the twist angle θ2 of the weld line WL is larger than the twist angle θ1 of the fin 3 from the above equation. This is because the outer peripheral surface and the inner peripheral surface of the surface that is the reference for the twist angle θ1 of the fin 3 and the twist angle θ2 of the weld line WL are different due to the difference in wall thickness.
For the twist angle θ2, for example, when the inner spiral grooved tube 10 is viewed from the side as shown in FIG. 5, the spiral drawn by the weld line WL is observed, and the straight line portion thereof is extracted to extract the center of the inner spiral grooved tube 10. It is grasped as the intersection angle of the axis line with the parallel line.

Further, according to the present embodiment, a plurality of fins 3 formed spirally along the length direction are provided on the inner peripheral surface 10b of the inner surface spiral grooved tube 10. By forming the spiral fin 3 on the inner peripheral surface 10b, the heat exchange efficiency between the inner spiral grooved pipe 10 and the refrigerant liquid flowing inside the pipe 10 can be improved. The inner spiral grooved pipe 10 provided with the spiral fins 3 can be formed by applying a twist to the raw pipe 10B having fins extending linearly in the length direction by extrusion processing. Further, by applying a twist, the weld line WL can be formed in a spiral shape, and the inner surface spiral grooved tube 10 having excellent pressure resistance to the internal pressure can be provided.

As shown in FIG. 5B, a spiral die mark DM is formed on the outer peripheral surface 10a of the inner spiral grooved tube 10. The die mark DM is a linear recess formed along the extrusion direction on the peripheral surface of a member formed by extrusion processing. The die mark DM is formed due to the influence of scratches on the extrusion die and the bearing surface. The inner spiral grooved pipe 10 of the present embodiment is manufactured by twisting the extruded raw pipe while pulling it out. Therefore, the die mark DM formed linearly by extrusion processing becomes spiral as the twist is applied.
The dice mark DM of FIG. 5B is shown so that one dice mark DM is continuously formed for the sake of clarity. The actual dice marks are formed intermittently along the length direction as shown as photographs in FIGS. 23 (a) and 24 (a). Further, a plurality of die marks DM extend spirally and in parallel along the circumferential direction of the outer peripheral surface of the inner surface spiral grooved tube 10.
In addition, in this specification, the term "die mark" is used not only for the recess formed by the extrusion process but also for the recess of the heat transfer tube after twisting the raw tube having the recess. Strictly speaking, the concave portion of the pipe material after being twisted is a concave portion due to the die mark. However, for the sake of clarity in the present specification, the concept including these is referred to as a dice mark. The twist angle of the die mark DM is formed to be θ2, which is the same as the twist angle of the weld line WL. Therefore, the relationship of the above equation also holds for the dice mark DM.

The maximum depth of the die mark DM after the twist is applied is 35 μm or less. As described above, the inner spiral grooved tube 10 is bent into a hairpin shape when used as a heat exchanger 80 (see FIGS. 1 and 2). In such a bending process, the die mark DM tends to be a starting point of damage to the inner spiral grooved tube 10. According to the present embodiment, by setting the maximum depth of the die mark DM to 35 μm or less, the strength of the inner spiral grooved tube 10 is increased, and the inner spiral grooved tube is not easily damaged by additional processing such as bending. 10 can be provided.

The method of measuring the depth of the die mark will be described.
For the die mark depth measurement, for example, the surface shape can be measured using a scanning laser microscope (VK-X100 / X200) manufactured by KEYENCE CORPORATION. Further, in the measurement analysis, the die mark depth can be measured by using the analysis application (VK-H1XA).
First, the sample is placed on the stage of a scanning laser microscope (VK-X100 / X200), and after focusing at an observation magnification of 50 times, the observation height upper and lower limit range is 100 μm, and the surface shape is 0.5 μm pitch. Make a measurement.
Next, the dice mark depth on the image obtained by using the analysis application (VK-H1XA) is measured. As a pretreatment before measurement, tilt correction was performed to flatten the arc on the pipe surface. From the surface shape that was pretreated, three straight lines were drawn so as to be parallel to the circumferential direction of the pipe, and the maximum valley depth (Rv) and maximum height (Rz) were obtained from the obtained roughness curve. In the measurement of the die mark depth, the measurement is performed as the maximum cross-sectional height (Rt).
In the analysis application, the surface roughness analysis was performed with the roughness parameters defined in JISB0601-2001 and JIS0601-1994 based on "Definition of Surface Roughness" (JISB0601: 2001).
FIG. 23 (b) shows the depth measurement result of the dice mark DM of FIG. 23 (a). Similarly, FIG. 24 (b) shows the depth measurement result of the dice mark DM of FIG. 24 (a). The inner spiral grooved tube having the die mark DM illustrated in FIGS. 23 and 24 is an example of the inner spiral grooved tube 10 of the present embodiment manufactured by the manufacturing apparatus shown in FIG.

In the inner spiral grooved pipe 10 of the present embodiment, an aggregate structure is formed on the pipe wall of the pipe body 10A.
Aluminum or an aluminum alloy is a polycrystal, and the orientation of individual crystal grains is usually random, but when the polycrystal undergoes plastic deformation, the orientation of the crystal grains may easily gather in a specific direction. There, this specific direction can be referred to as a priority orientation, and a polycrystal having a priority orientation can be referred to as a material having an texture. The formation of textures by plastic processing is known as the result of crystal rotation due to slippage in specific crystal planes and crystal directions.
The inner spiral grooved pipe 10 of the present embodiment is obtained by twisting and pulling out a raw pipe (straight grooved pipe) 10B having a structure shown in FIG. 6 as described later using a manufacturing apparatus A described later.
That is, the inner spiral grooved tube 10 can be obtained by twisting the raw tube 10B at the same time as drawing with a die.
Therefore, the tube wall of the raw tube 10B is subjected to a predetermined plastic working due to drawing and twisting, and as a result, the inner spiral grooved tube 10 having a metal structure in which an aggregate structure is developed in a specific direction of the tube wall. Is obtained.

To specify the orientation of this texture, as an example, the inner spiral grooved tube 10 is cut to an appropriate length, the tube wall is cut open to form a flat sample, and then the outer surface (tube) of this sample is obtained. The (200), (220), and (111) incomplete pole diagrams are measured on the outer surface of the wall using the X-ray reflection method, analyzed by the Bunge method using analysis software (Standard ODF), and crystallized. It can be grasped by measuring the orientation distribution function (ODF).
For example, a Cu tube, 40 kV-40 mA, can be used as the X-ray diffraction condition in the X-ray reflection method, and the value can be obtained under the condition of α angle: 20 to 90 ° (Step: 5.0 °). The pull-out direction can be defined as RD, the scanning direction can be defined as TD, and the radial direction of the tube can be defined as ND.

FIG. 11 is a (200) incomplete pole figure of an inner spiral grooved tube manufactured so as to impart a torsion angle of 20 ° in an embodiment using a manufacturing apparatus A described later, and FIG. 12 is a (220) incomplete pole. FIG. 13 shows an example of (111) incomplete pole figure.
FIG. 14, FIG. 15, and FIG. 16 show pole figures obtained by adding a correction of 20 ° corresponding to the twist angle in the RD-TD direction to these pole figures.
Further, the (200) pole figure, (220) pole figure, and (111) pole figure of the comparative example sample obtained by omitting the twisting of these Example samples using the manufacturing apparatus A described later and performing only drawing are shown. It is shown in FIG. 17, FIG. 18, and FIG.
Although the main features cannot be confirmed in the pole figures shown in FIGS. 11 to 13, the pole figures shown in FIGS. 14 to 16 after 20 ° correction have a pattern similar to the pole figures of the drawn pipes shown in FIGS. 17 to 19. It can be seen that it shows.
From this, since the correction value of 20 ° coincides with the twist angle of the inner spiral grooved tube, the crystal orientation of the aggregate structure of the inner spiral grooved tube causes a twist of 20 ° in the drawing direction as compared with the drawn tube. It turned out that.

Further, the crystal orientation distribution function of the inner spiral grooved tube obtained from the incomplete pole diagram shown in FIGS. 11 to 13 is shown in FIG. 20 and obtained from the incomplete pole diagram corrected by 20 ° shown in FIGS. 14 to 16. The crystal orientation distribution function of the inner spiral grooved tube is shown in FIG. 21, and the crystal orientation distribution function of the inner spiral grooved tube obtained from the incomplete pole diagrams shown in FIGS. 17 to 19 is shown in FIG.
From these comparisons, in the crystal orientation distribution function of the inner spiral grooved tube, a crystal orientation map similar to that of the drawn tube could be obtained by applying a correction of 20 ° as in the pole figure.
From the position of the typical priority orientation observed in the face-centered cubic crystal of the texture, it was possible to recognize the accumulation of the Cu orientation {112} <111>, which is the rolled texture, in both the drawn pipe and the inner spiral grooved pipe. ..
Next, the accumulation of Goss orientation {011} <100> was observed.
Further, it can be seen that the degree of accumulation of these pipes tends to be weaker in the inner spiral grooved pipe than in the drawn pipe.
From these analyzes, it was found that the texture of the inner spiral grooved tube shows a texture in which the Cu orientation and the Goss orientation are preferentially oriented, and the orientation of the texture is relative to the RD (pulling orientation). It can be determined that the texture has an inclination of 20 ° depending on the twist angle in the RD-TD direction.

As described above, the inner spiral grooved pipe 10 has an aggregate structure depending on the twist angle on the tube wall, but since the development of the aggregate structure is weaker than that of the drawn pipe, the aggregated structure is larger than that of the drawn pipe. Development can be weakened. If a twisted drawing pipe with weaker texture development is used than a drawn pipe with strong texture development, the inner spiral grooved pipe weakens the elongation anisotropy and strength anisotropy of the pipe wall. Therefore, the inner spiral grooved tube 10 having a weakly developed aggregated structure has a feature that cracks and buckling can be suppressed at the bent portion of the hairpin than the drawn tube with a strongly developed aggregated structure.
Therefore, even if the inner spiral grooved tube 10 is used as the heat transfer tube 81 and the elbow tube 81B of the heat exchanger 80 and the hairpin is bent with a small radius of curvature, wrinkles and flat portions are unlikely to occur in the bent portion. It is characterized by being able to provide a heat transfer tube 81 and an elbow tube 81B that are unlikely to crack or break.

[Production method]
Hereinafter, embodiments of a method for manufacturing the inner spiral grooved tube 10 according to the present invention will be described with reference to the drawings. The method for manufacturing the inner spiral grooved tube 10 includes an extrusion molding step and a torsional drawing step in this order.

<Extrusion molding process>
First, the extrusion molding process will be described.
FIG. 6 is a vertical cross-sectional view of a raw pipe (straight grooved pipe) 10B formed by an extrusion molding step, and FIG. 7 is a perspective view of the raw pipe 10B.
By extruding a billet made of an aluminum material, as shown in FIG. 7, a raw pipe 10B in which a plurality of straight grooves 4B along the length direction are formed on the inner surface at intervals in the circumferential direction is manufactured (straight groove). Attached pipe extrusion process). In the raw tube 10B formed by the extrusion molding step, four weld lines WL extending linearly in the length direction of the raw tube 10B are formed. The four weld lines WL are located at equal intervals (90 ° intervals) along the circumferential direction of the raw tube 10B.

<Twisting and pulling process>
Next, the twisting and pulling process will be described.
The twist-pulling step is a step of spiraling the weld line WL, the fins 3B, and the straight groove 4B by applying a twist to the above-mentioned raw pipe 10B while pulling out.

In this specification, the pipe material (that is, the above-mentioned raw pipe 10B) before twisting and pulling out is referred to as a "straight grooved pipe". Further, the pipe material after twisting and pulling out is called an "inner surface spiral grooved pipe". Further, in the process from the straight grooved pipe to the inner spiral grooved pipe, an intermediate formed product to which about half of the twisted pull-out is given as compared with the inner spiral grooved pipe is called an "intermediate twisted pipe". Further, the “tube material” in the present specification is a superordinate concept of a straight grooved pipe, an intermediate twisted pipe and an inner spiral grooved pipe, and means a pipe to be processed regardless of the stage of the manufacturing process.
In the present specification, the "pre-stage" and "rear stage" mean the front-back relationship (that is, upstream and downstream) along the processing order of the pipe material, and do not mean the arrangement of each part in the apparatus.
The pipe material is conveyed from the front stage (upstream) side to the rear stage (downstream) side in the manufacturing apparatus for the inner spiral grooved pipe. The portion arranged in the front stage is not always arranged in the front, and the portion arranged in the rear stage is not always arranged in the rear.

<Manufacturing equipment that performs the twisting and pulling process>
FIG. 8 is a front view showing a manufacturing apparatus A for manufacturing an inner spiral grooved tube (heat transfer tube) 10 by applying twisting and pulling out twice to a straight grooved tube (bare tube) 10B. First, the manufacturing apparatus A will be described, and then the twisting and pulling step using the manufacturing apparatus A will be described.

The manufacturing apparatus A includes a revolution mechanism 30, a floating frame 34, an unwinding bobbin (first bobbin) 11, a first guide capstan 18, a first drawing die 1, and a first revolution capstan. It includes 21, a revolution flyer 23, a second revolution capstan 22, a second drawing die 2, a second guide capstan 61, and a take-up bobbin (second bobbin) 71. The details of each part will be described below.

(Revolution mechanism)
The revolution mechanism 30 has a rotating shaft 35 including a front shaft 35A and a rear shaft 35B, a drive unit 39, a front stand 37A, and a rear stand 37B.
The revolution mechanism 30 rotates the rotating shaft 35, and the first revolution capstan 21, the second revolution capstan 22, and the revolution flyer 23 fixed to the rotating shaft 35.
Further, the revolution mechanism 30 maintains a stationary state of the floating frame 34 located coaxially with the rotating shaft 35 and supported by the rotating shaft 35. As a result, the unwinding bobbin 11, the first guide capstan 18, and the first drawing die 1 supported by the floating frame 34 are maintained in a stationary state.

Both the front shaft 35A and the rear shaft 35B have a cylindrical shape with a hollow inside. Both the front shaft 35A and the rear shaft 35B are arranged coaxially with the revolution center axis C (pass line of the first drawing die) as the center axis. The front shaft 35A is rotatably supported by the front stand 37A via a bearing 36, and extends from the front stand 37A toward the rear (rear stand 37B side). Similarly, the rear shaft 35B is rotatably supported by the rear stand 37B via a bearing, and extends from the rear stand 37B toward the front (front stand 37A side). A floating frame 34 is bridged between the front shaft 35A and the rear shaft 35B.

The drive unit 39 includes a drive motor 39c, a linear motion shaft 39f, belts 39a and 39d, and pulleys 39b and 39e. The drive unit 39 rotates the front shaft 35A and the rear shaft 35B.
The drive motor 39c rotates the linear motion shaft 39f. The linear motion shaft 39f extends in the front-rear direction at the lower part of the front stand 37A and the rear stand 37B.
A pulley 39b is attached to the front end portion 35Ab of the front shaft 35A at a tip penetrating the front stand 37A. The pulley 39b is interlocked with the linear motion shaft 39f via the belt 39a. Similarly, the rear end portion 35Bb of the rear shaft 35B has a pulley 39e attached to the tip penetrating the rear stand 37B and interlocks with the linear motion shaft 39f via the belt 39d. As a result, the front shaft 35A and the rear shaft 35B rotate synchronously around the revolution center axis C.

A first revolution capstan 21, a second revolution capstan 22, and a revolution flyer 23 are fixed to the rotating shaft 35 (front shaft 35A and rear shaft 35B). As the rotary shaft 35 rotates, these members fixed to the rotary shaft 35 revolve around the center axis C of the revolution rotation.

(Floating frame)
The floating frame 34 is supported by bearings 34a at the ends 35Aa and 35Ba of the front shaft 35A and the rear shaft 35B of the rotating shaft 35 facing each other. The floating frame 34 also supports the unwinding bobbin 11, the first guide capstan 18, and the first drawing die 1.

FIG. 9 is a plan view of the floating frame 34 as seen from the direction of arrow IX in FIG. As shown in FIGS. 8 and 9, the floating frame 34 has a box shape that opens vertically. The floating frame 34 has a front wall 34b and a rear wall 34c that face each other in the front-rear direction, and a pair of support walls 34d that face each other in the left-right direction and extend in the front-rear direction.

Through holes are provided in the front wall 34b and the rear wall 34c, and the ends 35Aa and 35Ba of the front shaft 35A and the rear shaft 35B are inserted, respectively. A bearing 34a is interposed between the ends 35Aa and 35Ba and the through holes of the front wall 34b and the rear wall 34c. As a result, it is difficult for the rotation of the rotating shaft 35 (front shaft 35A and rear shaft 35B) to be transmitted to the floating frame 34. The floating frame 34 keeps a stationary state with respect to the ground G even when the rotating shaft 35 is in a rotating state. A weight that biases the center of gravity of the floating frame 34 with respect to the revolution center axis C may be provided to stabilize the stationary state of the floating frame 34.

As shown in FIG. 9, the pair of support walls 34d has the unwinding bobbin 11, the first guide capstan 18, and the first drawing die 1 arranged on both sides in the left-right direction (vertical direction in FIG. 9). There is. The pair of support walls 34d rotatably support the bobbin support shaft 12 that holds the unwinding bobbin 11 and the rotation shaft J18 of the first guide capstan 18. Further, the support wall 34d supports the first drawing die 1 via a die support (not shown).

(Unwinding bobbin)
A bare tube 10B (see FIG. 6) in which a straight groove 4B is formed is wound around the unwinding bobbin 11. The unwinding bobbin 11 unwinds the raw tube 10B and supplies it to the subsequent stage.
The unwinding bobbin 11 is detachably attached to the bobbin support shaft 12.

As shown in FIG. 9, the bobbin support shaft 12 extends in a direction orthogonal to the rotating shaft 35. Further, the bobbin support shaft 12 is supported by a floating frame 34 so as to rotate and rotate. Here, the rotation rotation means rotation around the central axis of the bobbin support shaft 12 itself. The bobbin support shaft 12 holds the unwinding bobbin 11 and rotates on its axis in the supply direction of the unwinding bobbin 11 to assist the feeding of the raw pipe 10B from the unwinding bobbin 11.

The unwinding bobbin 11 is removed when all the wound raw tubes 10B are supplied, and is replaced with another unwinding bobbin. The removed empty unwinding bobbin 11 is attached to an extruder forming the raw pipe 10B, and the linear grooved pipe 10B is wound again. The unwinding bobbin 11 is supported by the floating frame 34 and does not revolve. Therefore, even if the straight grooved tube 10B is randomly wound on the unwinding bobbin 11, the supply can be performed without any problem, and the unwinding bobbin 11 can be used without rewinding. Further, the weight of the unwinding bobbin 11 does not limit the number of revolutions of the revolution rotation for imparting a twist to the linear grooved pipe 10B in the manufacturing apparatus A. Therefore, the long straight grooved tube 10B can be wound around the unwinding bobbin 11. As a result, the long raw pipe 10B can be twisted, and the manufacturing efficiency can be improved.

The bobbin support shaft 12 is provided with a brake portion 15. The brake unit 15 applies a braking force to the rotation of the bobbin support shaft 12 with respect to the floating frame 34. That is, the brake unit 15 regulates the rotation of the unwinding bobbin 11 in the unwinding direction. A rear tension is applied to the linear grooved pipe 10B conveyed in the unwinding direction by the braking force of the brake portion 15. As the brake unit 15, for example, a powder brake or a band brake capable of adjusting torque as a braking force can be adopted.

(1st guide capstan)
The first guide capstan 18 has a disk shape. A straight grooved pipe 10B unwound from the unwinding bobbin 11 is wound around the first guide capstan 18. The tangential direction of the outer circumference of the first guide capstan 18 coincides with the revolution center axis C. The first guide capstan 18 guides the raw pipe 10B along the first direction D1 on the revolution center axis C.
The first guide capstan 18 is supported by a floating frame 34 so as to rotate and rotate. Further, on the outer circumference of the first guide capstan 18, the guide rollers 18b that can rotate and rotate are arranged side by side. The first guide capstan 18 of the present embodiment rotates on its own axis and the guide roller 18b rotates, but if either one rotates, the straight grooved pipe 10B can be smoothly conveyed. In FIG. 8, the guide roller 18b is not shown.

As shown in FIG. 7, a pipeline guide portion 18a is provided between the first guide capstan 18 and the unwinding bobbin 11. The pipeline guide portion 18a is, for example, a plurality of guide rollers arranged so as to surround the straight grooved pipe 10B. The pipeline guide portion 18a guides the raw pipe 10B supplied from the unwinding bobbin 11 to the first guide capstan 18.

Instead of the first guide capstan 18, a guide tube having a traverse function may be provided between the unwinding bobbin 11 and the first drawing die 1. When the guide pipe is provided, the distance between the unwinding bobbin 11 and the first drawing die 1 can be shortened, and the space in the factory can be effectively utilized.

(1st pull-out die)
The first drawing die 1 reduces the diameter of the raw pipe 10B (tube material 5). The first drawing die 1 is fixed to the floating frame 34. The first drawing die 1 has the first direction D1 as the drawing direction. The center of the first drawing die 1 coincides with the revolution center axis C of the rotating shaft 35. Further, the first direction D1 is parallel to the revolution center axis C.
Lubricating oil is supplied to the first drawing die 1 by the lubricating oil supply device 9A fixed to the floating frame 34. As a result, the pulling force of the first pulling die 1 can be reduced.
The pipe material 5 that has passed through the first drawing die 1 is introduced into the front shaft 35A through a through hole provided in the front wall 34b of the floating frame 34.

(1st revolution capstan)
The first revolution capstan 21 has a disk shape. The first revolution capstan 21 is arranged in a lateral hole 35Ac that radially penetrates the inside and outside of the hollow front shaft 35A. The first revolving capstan 21 is supported by a support 21a fixed to the outer peripheral portion of the rotating shaft 35 (front shaft 35A) with the center of the disk as the rotating shaft J21 in a state where the rotation can be freely rotated.

In the first revolution capstan 21, one of the tangents on the outer circumference substantially coincides with the revolution center axis C.
A pipe material 5 conveyed in the first direction D1 on the revolution center axis C is wound around the first revolution capstan 21 for one or more turns. The first revolution capstan 21 winds the pipe material 5 and pulls it out from the inside of the front shaft 35A to guide it to the revolution flyer 23.

The first revolution capstan 21 revolves around the revolution center axis C together with the front shaft 35A. The revolution center axis C extends in a direction orthogonal to the rotation axis J21 of the rotation rotation of the first revolution capstan 21. The pipe material is twisted between the first revolution capstan 21 and the first drawing die 1. As a result, the pipe material 5 changes from the straight grooved pipe 10B to the intermediate twisted pipe 10C.

Along with the first revolution capstan 21, a drive motor 20 is provided on the front shaft 35A. The drive motor 20 drives and rotates the first revolution capstan 21 in the winding direction (conveying direction) of the pipe material 5. As a result, the first revolution capstan 21 applies a forward tension to the pipe material 5 for passing through the first drawing die 1.

The first revolution capstan 21 and the drive motor 20 are preferably arranged at positions symmetrical with respect to the revolution center axis C so that the center of gravity is located on the revolution center axis C of the front shaft 35A. Thereby, the balance of rotation of the front shaft 35A can be stabilized. If the weight difference between the first revolution capstan 21 and the drive motor 20 is large, a weight may be provided to stabilize the center of gravity.

(Revolution flyer)
The revolution flyer 23 reverses the pipe line of the pipe material 5 between the first drawing die 1 and the second drawing die 2. The revolving flyer 23 reverses the pipe material 5 conveyed in the first direction D1 which is the drawing direction of the first drawing die 1, and sets the conveying direction to the second direction D2 which is the drawing direction of the second drawing die 2. Turn to. More specifically, the revolution flyer 23 guides the pipe material 5 from the first revolution capstan 21 to the second revolution capstan 22.

The revolution flyer 23 has a plurality of guide rollers 23a and a guide roller support (not shown) that supports the guide rollers 23a. Here, the guide roller support is not shown in order to eliminate the complexity, but the guide roller support is supported by the rotating shaft 35. However, the guide roller is not indispensable for the structure of the flyer, and it may be simply a plate-like structure for the pipe to pass through and a shape to which a ring for passing the pipe is attached. This ring may be provided on a plate-shaped member. A part of this ring may be composed of a part of this plate-shaped member. The plate-shaped member may be supported by the rotating shaft 35 in the same manner as the guide roller support.
The guide rollers 23a are arranged in a bow shape that curves outward with respect to the revolution center axis C. The guide roller 23a itself rolls and smoothly conveys the pipe material 5. The revolution flyer 23 rotates around the floating frame 34, the first drawing die 1 supported in the floating frame 34, and the unwinding bobbin 11 around the revolution rotation center axis C.

One end of the revolution flyer 23 is located outside the first revolution capstan 21 with respect to the revolution center axis C. Further, the other end of the revolution flyer 23 passes through a lateral hole 35Bc that radially penetrates the inside and outside of the hollow rear shaft 35B and extends to the inside of the rear shaft 35B. The revolution flyer 23 guides the pipe material 5 wound around the first revolution capstan 21 and extended outward to the rear shaft 35B side. Further, the revolution flyer 23 feeds the pipe material 5 inside the rear shaft 35B on the revolution center axis C along the second direction D2.

The revolution flyer 23 of the present embodiment has been described as being for transporting the pipe material 5 by the guide roller 23a. However, the revolution flyer 23 may be formed from a strip formed in an arch shape, and the pipe material 5 may be transported by sliding one surface of the strip.
Further, in FIG. 8, a case where the pipe material 5 passes outside the guide roller 23a is illustrated.
However, when the rotation speed of the revolution flyer 23 is high, the pipe material 5 may derail from the revolution flyer due to centrifugal force. In such a case, it is preferable to further provide a guide roller 23a on the outside of the pipe material 5.
A plurality of dummy flyers having the same weight as the revolution flyer 23 and extending from the front shaft 35A to the rear shaft 35B and rotating synchronously with the revolution flyer 23 may be provided. Thereby, the rotation of the rotating shaft 35 can be stabilized.

(Second revolution capstan)
The second revolution capstan 22 has a disk shape like the first revolution capstan 21. The second revolving capstan 22 is supported by a support 22a provided at the tip of the end portion 35Bb of the rear shaft 35B in a state where it can rotate freely. Further, on the outer circumference of the second revolving capstan 22, guide rollers 22c that can rotate and rotate are arranged side by side. The second revolving capstan 22 of the present embodiment rotates on its own axis and the guide roller 22c rotates, but if either one rotates, the pipe material 5 can be smoothly conveyed.

In the second revolution capstan 22, one of the tangents on the outer circumference substantially coincides with the revolution center axis C.
A pipe material 5 conveyed in the second direction D2 on the revolution center axis C is wound around the second revolution capstan 22 for one or more turns. The second revolution capstan 22 feeds the wound pipe material in the second direction D2 on the revolution center axis C.

The second revolution capstan 22 revolves around the revolution center axis C together with the rear shaft 35B. The revolution center axis C extends in a direction orthogonal to the rotation axis J22 of the rotation rotation of the second revolution capstan 22. The pipe material 5 unwound from the second revolution capstan 22 is reduced in diameter in the second drawing die 2. Since the second drawing die 2 is stationary with respect to the ground G, the pipe material 5 can be twisted between the second revolving capstan 22 and the second drawing die 2. As a result, the pipe material 5 changes from the intermediate twisted pipe 10C to the inner spiral grooved pipe 10.

The support 22a that supports the second revolution capstan 22 supports the weight 22b at a position symmetrical to the second revolution capstan 22 with respect to the revolution center axis C. The weight 22b stabilizes the rotational balance of the rear shaft 35B.

(Second pull-out die)
The second drawing die 2 is arranged after the second revolution capstan 22. The second drawing die 2 has the opposite second direction D2 as the drawing direction. The second direction D2 is a direction parallel to the revolution center axis C. The second direction D2 is opposite to the first direction D1, which is the drawing direction of the first drawing die 1. The pipe material 5 passes through the second drawing die 2 along the second direction D2. The second drawing die 2 is stationary with respect to the ground G. The center of the second drawing die 2 coincides with the revolution center axis C of the rotating shaft 35.

The second drawing die 2 is supported by the gantry 62, for example, via a die support (not shown). Further, lubricating oil is supplied to the second drawing die 2 by the lubricating oil supply device 9B attached to the gantry 62. As a result, the pulling force of the second pulling die 2 can be reduced.
Due to the diameter reduction and twisting of the second drawing die 2, the pipe material 5 changes from the intermediate twisted pipe 10C to the inner spiral grooved pipe 10.

(Second guide capstan)
The second guide capstan 61 has a disk shape. The tangential direction of the outer circumference of the second guide capstan 61 coincides with the revolution center axis C. A pipe material 5 conveyed in the second direction D2 on the revolution center axis C is wound around the second guide capstan 61 for one or more turns.

The second guide capstan 61 is rotatably supported by the gantry 62 around the rotation shaft J61. Further, the rotating shaft J61 of the second guide capstan 61 is connected to the drive motor 63 via a drive belt or the like. The second guide capstan 61 is driven and rotated by the drive motor 63 in the winding direction (conveying direction) of the inner spiral grooved pipe 10. As the drive motor 63, it is preferable to use a torque motor capable of torque control.

A forward tension is applied to the pipe material 5 by driving the second guide capstan 61. As a result, the pipe material 5 is conveyed forward by applying the drawing stress required for processing in the second drawing die 2.

(Take-up bobbin)
The take-up bobbin 71 is provided at the end of the pipeline of the inner spiral grooved pipe 10 and collects the inner spiral grooved pipe 10. An induction portion 72 is provided in front of the take-up bobbin 71. The guide portion 72 has a traverse function and winds the inner spiral grooved pipe 10 around the bobbin 71 in an aligned manner.

The take-up bobbin 71 is detachably attached to the bobbin support shaft 73. The bobbin support shaft 73 is supported by the gantry 75 and is connected to the drive motor 74 via a drive belt or the like. The take-up bobbin 71 is driven and rotated by the drive motor 74, and takes up the pipe material 5 without loosening it. The take-up bobbin 71 is removed when the inner spiral grooved tube 10 is sufficiently wound and replaced with another take-up bobbin 71.

<Twisting and pulling process>
A method of manufacturing the inner spiral grooved tube 10 by using the manufacturing apparatus A described above will be described.
First, as a preliminary step, the raw pipe (straight grooved pipe) 10B is unwound and wound around the bobbin 11 in a coil shape. Further, the unwinding bobbin 11 is set in the floating frame 34 of the manufacturing apparatus A. Further, the raw pipe 10B (pipe material 5) is unwound from the unwinding bobbin 11 and the pipeline of the raw pipe 10B is set in advance. Specifically, the raw pipe 10B is provided with a first guide capstan 18, a first drawing die 1, a first revolution capstan 21, a revolution flyer 23, a second revolution capstan 22, and a second drawing die. 2. Pass the second guide capstan 61 and the take-up bobbin 71 in this order and set them.

In the manufacturing process of the inner spiral grooved pipe 10, the description will be given along the transport path of the pipe material.
First, the raw pipe 10B (tube material 5) is sequentially unwound from the unwinding bobbin 11.
Next, the raw pipe 10B unwound from the unwinding bobbin 11 is wound around the first guide capstan 18. The first guide capstan 18 guides the raw pipe 10B into the die hole of the first drawing die 1 located on the revolution center axis C (first guiding step).

Next, the raw tube 10B is passed through the first drawing die 1. Further, in the subsequent stage of the first drawing die 1, the pipe material 5 is wound around the first revolution capstan 21 and rotated around the rotation axis. As a result, the diameter of the raw tube 10B is reduced and a twist is applied (first twisting and pulling step).

In the first torsional pull-out step, forward tension is applied to the raw pipe 10B by the drive motor 20 that drives the first revolution capstan 21. At the same time, a rear tension is applied to the raw pipe 10B by the brake portion 15 of the unwinding bobbin 11. Therefore, it is possible to apply an appropriate tension to the raw pipe 10B, and it is possible to give a stable twist angle to the raw pipe 10B without causing buckling or breakage.

The pipe material 5 is passed through the first drawing die 1 and then wound around the first revolving capstan 21 that revolves. The pipe material 5 is reduced in diameter by the first drawing die 1 and twisted by the first revolution capstan 21. As a result, the linear flow path pipe 7A inside the pipe material 5 is twisted to form the inner spiral grooved pipe 10. By the first twisting and pulling step, the raw pipe 10B becomes an intermediate twisted pipe 10C. The intermediate twisted pipe 10C is a pipe material in an intermediate stage in the manufacturing process of the inner surface spiral grooved pipe 10, and is in a state where a spiral groove having a twist angle shallower than that of the inner surface spiral groove of the inner surface spiral grooved pipe 10 is formed.

In the first torsional drawing step, the pipe material 5 is twisted and at the same time the diameter is reduced by the drawing die. That is, the pipe material 5 is subjected to a composite stress due to simultaneous machining of twisting and diameter reduction. Under the combined stress, the yield stress of the pipe material 5 becomes smaller than that in the case where only the twisting process is performed, and a large twist can be applied to the pipe material 5 before the buckling stress of the pipe material 5 is reached. As a result, it is possible to impart a large twist while suppressing the occurrence of buckling of the pipe material 5. Further, by this twisting and pulling step, the aggregate structure of the pipe wall of the pipe material 5 develops to some extent.

A first guide capstan 18 is provided in front of the first drawing die 1 to regulate the rotation of the pipe material 5. That is, the pipe material 5 is restrained from being deformed in the twisting direction in the front stage of the first drawing die 1. The pipe material 5 is twisted between the first drawing die 1 and the first revolving capstan 21. That is, in the first torsional drawing step, the region (machining area) where the pipe material 5 is twisted is limited between the first drawing die 1 and the first revolution capstan 21.
There is a correlation between the length of the machining area and the limit twist angle (the maximum twist angle that can be twisted without buckling), and even if a large twist angle is given by shortening the machining area. Buckling is unlikely to occur in the pipe material 5. By providing the first guide capstan 18, the machining area can be set short without twisting in the front stage of the first drawing die 1. Further, the machining area is set short by shortening the distance between the first drawing die 1 and the first revolution capstan 21, and a large twist, for example, a twist of 10 to 45 ° is performed on the pipe material 5 without causing buckling. Can be granted.

The diameter reduction ratio of the pipe material 5 by the first drawing die 1 is preferably 2% or more. A correlation is observed between the limit twist angle and the diameter reduction ratio, and the limit twist angle tends to increase as the diameter reduction ratio at the time of drawing increases. That is, if the diameter reduction ratio is too small, the effect of pulling out is poor and it is difficult to obtain a large twist angle. Therefore, it is preferably 2% or more. For the same reason, it is more preferable that the diameter reduction ratio is 5% or more.
On the other hand, if the diameter reduction ratio becomes too large, fracture is likely to occur at the processing limit, so it is preferably 40% or less.

Next, the pipe material 5 is wound around the revolution flyer 23, and the transport direction of the pipe material 5 is directed to the second direction D2 on the revolution center axis C. Further, the pipe material 5 is wound around the second revolution capstan 22 and the pipe material 5 is introduced into the second drawing die 2 (second induction step). As a result, the transport direction of the pipe material 5 is reversed from the first direction D1 to the second direction D2, and is aligned with the center of the second drawing die 2. The revolution flyer 23 rotates around the floating frame 34 about the revolution center axis C. The first revolution capstan 21, the revolution flyer 23, and the second revolution capstan 22 rotate synchronously about the revolution center axis C. Therefore, between the first revolution capstan 21 and the second revolution capstan 22, the pipe material 5 does not rotate relatively and is not twisted.

Next, the pipe material 5 that rotates together with the second revolution capstan 22 is passed through the second drawing die 2. As a result, the diameter of the pipe material 5 is reduced and a twist is applied to further increase the twist angle of the inner spiral groove (second twist pulling step). By this second torsional drawing step, the intermediate torsion pipe 10C becomes the inner spiral grooved pipe 10.

In the second torsional pull-out step, forward tension is applied to the pipe material 5 by the drive motor 63 that drives the second guide capstan 61. When a torque controllable torque motor is used as the drive motor 63, the second guide capstan 61 can adjust the forward tension applied to the pipe material 5. By adjusting the forward tension with the second guide capstan 61, it is possible to apply an appropriate tension to the pipe material 5 in the second torsional pull-out step. As a result, a stable twist angle can be imparted to the pipe material 5 without causing buckling or breakage.

The pipe material 5 passes through the second drawing die 2 after being wound around the second revolving capstan 22 that revolves and rotates. The diameter of the pipe material 5 is reduced by the second drawing die 2, and the pipe material 5 is twisted by the second revolution capstan 22. As a result, a larger twist is applied to the flow path pipe of the pipe material 5, and the twist angle of the spiral groove becomes larger. The intermediate torsion tube 10C becomes the inner spiral grooved tube 10 by the second torsional drawing step.

In the front stage of the second drawing die 2, the pipe material 5 is wound around the second revolution capstan 22. In the subsequent stage of the second drawing die 2, a second guide capstan 61 is provided to regulate the rotation of the pipe material 5. That is, the pipe material 5 is restrained from being deformed in the twisting direction before and after the second drawing die 2, and the pipe material 5 is twisted between the second revolution capstan 22 and the second guide capstan 61. Withdrawal is granted. That is, in the second twist-drawing step, the region (machining area) where the pipe material 5 is twisted is limited between the second revolution capstan 22 and the second drawing die 2. As described above, by shortening the processing area, buckling is less likely to occur even if a large twist angle is applied. By providing the second guide capstan 61, the machining area can be set short without twisting in the subsequent stage of the second drawing die 2.

In the present embodiment, the second revolution capstan 22 is provided behind the rear stand 37B (on the side of the second drawing die 2), but the second revolution capstan 22 is the front stand 37A. It may be located between the rear stand 37B. However, by arranging the second revolution capstan 22 rearward with respect to the rear stand 37B and bringing it closer to the second drawing die 2, the machining area in the second torsional drawing step can be shortened. Thereby, the occurrence of buckling can be suppressed more effectively.

In the second torsional pull-out step, as in the first torsional pull-out step, twisting and diameter reduction are performed to apply a composite stress to the pipe material 5. As a result, before the buckling stress of the pipe material 5 is reached, a large twist, for example, a twist angle of 10 to 45 ° can be imparted to the pipe material while suppressing the occurrence of buckling.
In addition, the development of the textured structure progresses by the second torsional drawing step, and the textured structure having an inclination depending on the target twisting angle is developed.

The diameter reduction ratio of the pipe material 5 by the second drawing die 2 is preferably 2% or more (more preferably 5% or more) and 25% or less, as in the first torsional drawing step.
If the first drawing die 1 is subjected to a large diameter reduction (for example, a diameter reduction of 30% or more), the pipe material 5 is work-hardened, so that the second drawing die 2 is subjected to a large diameter reduction. It becomes difficult. Therefore, the total of the diameter reduction ratio of the first drawing die 1 and the diameter reduction ratio of the second drawing die 2 is preferably 4% or more and 50% or less.
<Sky pulling process>
Next, the pipe material 5 is passed through the finish drawing die 70 (finish drawing step). By passing the pipe material 5 through the finish drawing die 70, the surface is shaped and the uneven thickness of the wall thickness is reduced. Further, even if the pipe material 5 is slightly deformed such as crushed, the deformation can be corrected by going through this finish drawing step to obtain the pipe material 5 having a predetermined roundness. The force for transporting the pipe material 5 with respect to the pulling load of the finishing pulling die 70 is applied by the drive motor 74 provided on the take-up bobbin 71.

Further, the inner spiral grooved pipe 10 having a stable surface texture and shape can be manufactured by performing an empty pulling step after the twisting pulling step (the first twisting pulling step and the second twisting pulling step). The diameter reduction ratio of the pipe material 5 in the dry drawing step is preferably 25% or less. Further, the total diameter reduction ratio of the first drawing step, the second pulling step and the empty pulling step is preferably 30% or more.

<Recovery process>
Next, the pipe material 5 is wound around the take-up bobbin 71 and collected. The take-up bobbin 71 is rotated by the drive motor 74 in synchronization with the transport speed of the pipe material 5, so that the pipe material 5 can be wound up without slack.
Through the above steps, the inner surface spiral grooved tube 10 can be manufactured by using the manufacturing apparatus A.

According to the twisting step of the present embodiment, the linear weld line WL formed in the linear grooved pipe 10B in the extrusion molding step becomes spiral. As a result, it is possible to form a weld line WL in which cracks are unlikely to occur with an increase in internal pressure.
Further, according to the twisting step of the present embodiment, the twisting is repeated a plurality of times. As a result, the weld line WL formed in the extrusion molding process mixes with the surrounding structure and the boundary becomes ambiguous. As a result, the weld line WL can be partially eliminated and formed intermittently, and as a result, the inner spiral grooved tube 10 having high pressure resistance can be manufactured.
<O material conversion process>
Next, the O-material making process will be described.
The O materialization step is performed after the twisting step. The O-material formation step is a heat treatment step in which the pipe material 5 is annealed. By performing the O-material process, the strain of the aluminum material can be removed and the internal stress can be removed.

According to the manufacturing method of the present embodiment, by directly twisting and pulling out the straight grooved pipe 10B, the weld line WL, the spiral groove and the fin 3 can be formed spirally and intermittently at the same time. It becomes. In addition, it is possible to develop an aggregate structure of inclination angles depending on the desired torsion angle.
As a result, the inner spiral grooved tube that simultaneously achieves the effect of improving the pressure resistance by forming the weld line WL spirally and intermittently and the effect of improving the heat exchange rate by the spiral fin 3. 10 can be manufactured. Further, since an aggregate structure having an inclination depending on the twist angle can be developed, it is possible to manufacture the inner spiral grooved tube 10 which is unlikely to crack or break even if the hairpin is bent with a small curvature.

According to the manufacturing method of the present embodiment, the weld line generated in the raw pipe 10B by extrusion is performed by performing heat treatment (O material formation step) after twisting and drawing the raw pipe 10B formed by extrusion processing. The diffusion bonding of WL can be strengthened and the bonding strength can be increased.

According to the manufacturing method of the present embodiment, the total diameter reduction ratio of each step (first pulling step, second pulling step and empty pulling step) is 30% or more. By setting the diameter reduction ratio to 30% or more, a large twist can be imparted. Further, according to the manufacturing method of the present embodiment, the diameter reduction ratio of each step is 25% or less. When the diameter reduction ratio in each process is 25% or less, work hardening can be suppressed and the diameter reduction in the subsequent process can be smoothly performed.

In the twisting step of the present embodiment, the first torsional drawing step and the second torsional drawing step are performed again on the inner spiral grooved tube 10 formed through the above steps, and a larger twisting angle is imparted. You may. In this case, the inner spiral grooved tube 10 that has undergone the above steps is heat-treated (annealed) to form an O material. Further, the unwinding bobbin 11 is wound around the unwinding bobbin 11, and the unwinding bobbin 11 is attached to a manufacturing apparatus A having a first drawing die having an appropriate diameter reduction ratio and a second drawing die. Further, the manufacturing apparatus A can manufacture the inner spiral grooved tube 10 having a larger twist angle by going through the same steps (first twist-pulling step and second twist-pulling step) as described above.

According to the twisting step of the present embodiment, since the diameter is reduced at the same time as the twisting, the outer diameter and the cross-sectional area of the starting material and the final product are different. Further, since the combined stress of twist and diameter reduction is applied to the pipe material 5, it is possible to reduce the shear stress required for the twisting process, and a large twist is applied to the pipe material 5 before the buckling stress of the pipe material 5 is reached. Can be granted. Therefore, the inner spiral grooved tube 10 having the spiral groove 4 and the fin 3 having a large twist angle θ1 and having a thin bottom wall thickness can be manufactured without causing buckling. Further, it is possible to manufacture an inner spiral grooved tube 10 which is an inner spiral grooved tube 10 having a developed aggregate structure having an inclination depending on a twist angle and which is resistant to hairpin bending.
The inner spiral grooved tube 10 can improve the heat exchange efficiency by increasing the twist angle θ1 of the fin 3. Further, the inner surface spiral grooved tube 10 can be made lighter and less expensive by reducing the wall thickness. That is, according to the present embodiment, it is possible to manufacture the inner spiral grooved tube 10 which is lightweight, inexpensive, and has high heat exchange efficiency.

According to the twisting step of the present embodiment, since the straight grooved pipe 10B is twisted and the diameter is reduced, a large twisting angle can be imparted while suppressing the occurrence of buckling. In the present embodiment, the outer diameter of the straight grooved pipe 10B, which is a material, is 1.1 times or more the outer diameter of the final product, the inner spiral grooved pipe 10.

According to the twisting step of the present embodiment, the pipe material 5 is twisted by the first revolution capstan 21 between the first drawing die 1 and the second drawing die 2. Further, the drawing directions of the first drawing die 1 and the second drawing die 2 are reversed. As a result, the pipe material 5 can be twisted by matching the twisting directions in the first twisting and pulling step and the second twisting and pulling step. Further, it is not necessary to revolve the unwinding bobbin 11 which is the start end of the pipeline of the pipe material 5 and the take-up bobbin 71 which is the end of the pipeline. Since the speed of the line depends on the rotation speed, the rotation speed can be easily increased in the twisting step of the present embodiment in which the unwinding bobbin 11 or the winding bobbin 71, which is a heavy object, is not rotated. That is, according to this embodiment, the line speed can be easily increased.

Further, in the present embodiment, since the unwinding bobbin 11 is not revolved, a long straight grooved pipe 10B (tube material 5) can be wound around the unwinding bobbin 11. Therefore, according to the twisting step of the present embodiment, the unwinding bobbin 11 can be twisted in a single stroke without replacing the unwinding bobbin 11. That is, according to the present embodiment, mass production of the inner spiral grooved tube 10 becomes easy.
In the twisting step of the present embodiment, the pipe material 5 is twisted through at least two twisting and pulling steps. Therefore, it is possible to give a large twist angle by accumulating the twist angles given in the twist pulling step of each stage.

According to the twisting step of the present embodiment, the front tension and the rear tension are applied to the pipe material 5 in the first twisting and pulling step and the second twisting and pulling step. The forward tension is applied to the pipe material 5 by the second guide capstan 61, and the rear tension is applied to the pipe material 5 by the brake portion 15 that brakes the unwinding bobbin 11. As a result, an appropriate tension can be stably applied to the pipe material 5 to be processed. Since there is no slack in the pipe line of the pipe material 5 and the straight grooved pipe 10B enters the drawing die without misalignment, a stable twist angle can be imparted to the pipe material 5 without causing buckling or breakage.

In the first drawing die 1 and the second drawing die 2 according to the present embodiment, the center of the die hole is located on the revolution center axis C. As a result, the pipe material 5 passing through the die hole can be arranged linearly with respect to the die hole, so that the diameter of the pipe material 5 can be uniformly reduced and buckling at the time of twisting can be suppressed. In the first drawing die 1 and the second drawing die 2, the position of the die hole with respect to the revolution center axis C is allowed as long as the diameter of the pipe material 5 can be reduced normally.

In the present embodiment, it has been described that the unwinding bobbin 11 is supported by the floating frame 34 and the winding bobbin 71 is installed on the ground G. However, either the unwinding bobbin 11 or the winding bobbin 71 may be supported by the floating frame 34. That is, in FIG. 8, the unwinding bobbin 11 and the winding bobbin 71 may be interchanged and arranged. In this case, the transport path of the pipe material 5 is reversed. Further, the first drawing die 1 and the second drawing die 2 are arranged interchangeably, and the drawing directions of the respective drawing dies 1 and 2 are reversed and arranged along the conveying direction. Further, in the capstans located before and after the drawing dies 1 and 2, the capstan located at the rear stage of the drawing dies is driven in the winding direction (conveying direction) of the pipe material to apply a forward tension against the pulling force of the drawing dies. give.
Through the steps described above, the inner spiral grooved tube 10 having the configurations shown in FIGS. 3 to 5 can be manufactured.

According to the manufacturing method using the manufacturing apparatus A described in the above-described embodiment, the inner surface spiral grooved pipe (number of threads 58, number 58,) in which spiral fins are formed on the inner surface and spiral weld lines WL are formed on the outer peripheral surface. Samples with an outer diameter of 6 to 7.2 mm, a bottom wall thickness of 0.45 to 0.55 mm, a fin height of 0.25 mm, a fin apex angle of 11 °, and a maximum twist angle of 25 ° (Samples No. 1 to No. 6). Was produced.
For each sample, the outer diameter, the difference between the maximum bottom wall thickness and the minimum bottom wall thickness, the twist angle on the outer peripheral surface, the twist angle ratio ρ, the ratio of the length of one circumference to the spiral pitch for the die mark DM, and the die mark. DM depth and flatness are different. Each parameter of each sample is summarized in Table 1 below.
A slim fin type heat transfer tube was used as each sample.

(Measurement of strength against hairpin bending)
The heat transfer tube of each sample was bent by 180 ° in a hairpin shape with a radius of curvature (R = 15). Each condition was evaluated under n = 20, and those in which cracks were observed on the outer peripheral surface of the heat transfer tube were evaluated as x, and those in which no cracks were observed were evaluated as 〇.
The evaluation results are summarized in Table 1.

From the results shown in Table 1, it was confirmed that the heat transfer tube twisted with a sufficient twist angle is less likely to be damaged by the hairpin bending process.

(Evaluation of tube expandability)
As a test for confirming the soundness of the weld line, a pipe expansion test is performed by pushing a cone with an apex angle of 60 degrees (material SS400) into the pipe. The pipe was cut out to a length of 40 mm, and the end face was smoothed using a lathe. During the tube expansion test, beef tallow was applied to the surface in contact with the conical pipe with a brush to suppress variations in the results due to seizure.
Under the above conditions, the tube expansion load (force applied to the cone along the length direction of the heat transfer tube) and the pushing amount at the time when the heat transfer tube was cracked were measured.
A slim fin type heat transfer tube was used as each sample.

As shown in Table 2, when the weld line is spiral, the tube expansion load and the pushing amount are larger than those of the linear shape. More specifically, when the weld line is spiral, the tube expansion load can be 10 KN or more, and the pushing amount can be 3 mm or more.

"Analysis of aggregate structure"
A part of sample 1 in Table 1 is cut out, the tube wall is cut open, light pressure is applied with a press device to process it into a flat sample (40 mmL × 29 mmW × 0.5 mmt), and then the outer surface (tube) of this sample is processed. The (200), (220), and (111) incomplete pole diagrams were measured on the outer surface of the wall using the X-ray reflection method.
For example, a Cu tube, 40 kV-40 mA, can be used as the X-ray diffraction condition in the X-ray reflection method, and the value can be obtained under the condition of α angle: 20 to 90 ° (Step: 5.0 °). The pull-out direction is defined as RD, the scanning direction is defined as TD, and the radial direction of the tube is defined as ND.

FIG. 11 shows a (200) incomplete pole figure of this sample, FIG. 12 shows a (220) incomplete pole figure, and FIG. 13 shows a (111) incomplete pole figure.
FIG. 14, FIG. 15, and FIG. 16 show pole figures in which 20 ° correction (correction of the same inclination as the twist angle) corresponding to the twist angle is added to these pole figures in the RD-TD direction.
Further, with respect to these Example samples, twisting was omitted when the manufacturing apparatus A passed through the first drawing die and the second drawing die, and only drawing was performed to obtain the sample No. 4 (drawing tube) (drawing tube). 200) Extreme point diagram, (220) Extreme point diagram, and (111) Extreme point diagram are shown in FIGS. 17, 18, and 19.
Although the main features cannot be confirmed in the pole figures shown in FIGS. 11 to 13, the pole figures shown in FIGS. 14 to 16 after 20 ° correction have a pattern similar to the pole figures of the drawn pipes shown in FIGS. 17 to 19. It can be seen that it shows.
From this, since the correction value of 20 ° coincides with the twist angle of the inner spiral grooved tube, the crystal orientation of the aggregate structure of the inner spiral grooved tube causes a twist of 20 ° in the drawing direction as compared with the drawn tube. It turned out that.

Next, using analysis software (Standard ODF), analysis was performed by the Bunge method, and the crystal orientation distribution function (ODF) was obtained.
The crystal orientation distribution function of the inner spiral grooved tube obtained from the incomplete pole points of the samples shown in FIGS. 11 to 13 is shown in FIG. 20, and the incomplete pole points of the sample after 20 ° correction shown in FIGS. 14 to 16 are shown. The crystal orientation distribution function of the inner spiral grooved tube obtained from FIG. 21 is shown in FIG. 21, and the crystal orientation distribution function of the inner spiral grooved tube obtained from the incomplete pole drawings of the drawn tubes shown in FIGS. 17 to 19 is shown in FIG. show.
From the comparison between FIGS. 20 and 21, the crystal orientation distribution function of the inner spiral grooved tube shown in FIG. 20 is a drawing tube shown in FIG. 22 by applying a correction of 20 ° as in the polar diagram as shown in FIG. A crystal orientation map similar to the crystal orientation distribution function of was obtained.

From the position of the typical priority orientation observed in the surface-centered cubic crystal of the texture of these samples, the Cu orientation, which is the rolled texture of both the drawn pipe (FIG. 22) and the inner spiral grooved pipe (FIGS. 20 and 21). The accumulation of {112} <111> could be recognized.
Next, in these samples, accumulation of Goss orientation {011} <100> was observed.
Further, it can be seen that the degree of accumulation of these is weaker in the inner spiral grooved pipe than in the drawn pipe shown in FIG. 22.
From these analyzes, it was found that the texture of the inner spiral grooved tube shows a texture in which the Cu orientation and the Goss orientation are preferentially oriented, and the orientation of the texture is relative to the RD (pulling orientation). It can be determined that the texture has an inclination of 20 ° depending on the twist angle in the RD-TD direction.

This is an aggregate structure having a priority direction on the tube wall of the raw tube by two twisting and drawing processes using the first drawing die and the second drawing die, and has a Cu orientation {112} <111>. It means that the aggregate structure in which the Goss direction {011} <100> was accumulated could be generated so as to have an inclination depending on the twist angle of the inner spiral grooved tube of 20 °.
In addition, when comparing the No. 1 sample (inner spiral grooved tube) and the No. 9 to No. 10 samples (straight grooved tube) in the pressure resistance evaluation shown in Table 1, the inner spiral grooved tube is better. It was also found that it is superior to the straight grooved tube in terms of pressure resistance.
This is done by generating an aggregate structure in which the Cu orientation {112} <111> and the Goss orientation {011} <100> are integrated so as to have an inclination depending on the twist angle 20 ° of the inner spiral grooved tube. This means that the strength of the spiral grooved tube can also be improved.

Therefore, the above-mentioned No. 1 to No. 6 inner spiral grooved tubes can provide a heat transfer tube having excellent strength and corrosion resistance, and when used as a heat transfer tube in a heat exchanger, the hairpin is bent. It was found that a heat transfer tube that is hard to crack or break can be provided.
The Cu orientation integration degree and the Goss orientation integration degree of the inner spiral grooved pipe are lower than the Cu orientation integration degree and the Goss orientation integration degree of the drawn pipe of the straight grooved pipe, and the aggregation degree of the aggregate is low. Is synonymous with the fact that the anisotropy of the structure of the inner spiral grooved pipe can be relaxed as compared with the structure of the drawn pipe, and it is considered that the breakage due to processing such as bending of a pin is suppressed.

Conventionally, it has been considered that an extruded material and a wire drawing material of an aluminum alloy are likely to form a fibrous texture stretched in the longitudinal direction. In that case, a crystal plane having a <111> orientation or a <100> orientation is preferentially oriented. It is said to be easy. This phenomenon is caused by twisting the inner spiral grooved tube in which the aggregate structure in which the Cu orientation {112} <111> and the Goss orientation {011} <100> are integrated is formed in the inner spiral grooved tube manufactured by simultaneously twisting and pulling out. This is in line with the result of this time that it can be generated so as to have an inclination depending on the angle of 20 °. Under constant yield conditions, in the manufacture of inner spiral grooved pipes, drawing and twisting are applied at the same time, so the action of force in one direction can be relaxed and dispersed, and an unnecessarily strong texture is formed. Seems to be able to suppress.
Therefore, the anisotropy of the structure of the inner spiral grooved tube can be reduced, and as a result of improving the limit drawing amount, the inner spiral groove and fins having a high twist angle can be formed, and at the same time, the Cu orientation {112} <111>. It can be presumed that the aggregate structure in which the Goss orientations {011} <100> are accumulated can be generated so as to have an inclination depending on the twist angle of the inner spiral grooved tube of 20 °.

Although various embodiments of the present invention have been described above, the configurations and combinations thereof in each embodiment are examples, and the additions, omissions, substitutions, and configurations of the configurations are added, omitted, replaced, and the like without departing from the spirit of the present invention. Other changes are possible. Further, the present invention is not limited to the embodiments.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an inner spiral grooved tube which is made of aluminum or an aluminum alloy and has a spiral groove and a spiral fin inside. As a result, the cost, weight, and performance of the heat exchanger are reduced.

A ... Manufacturing equipment 1 ... 1st drawing die, 2 ... 2nd drawing die, 3 ... Fin, 4 ... Spiral groove, 5 ... Raw pipe (straight grooved pipe: pipe material), 10 ... Inner surface spiral grooved pipe ( Heat transfer tube), 10A ... tube body, 10B ... bare tube, 10a ... outer peripheral surface, 10b ... inner peripheral surface, 11 ... unwinding bobbin, 21 ... first revolving capstan, 22 ... second revolving capstan, 23 ... Revolving flyer, 30 ... Revolving mechanism, 34 ... Floating frame, 35 ... Rotating shaft, 71 ... Winding bobbin, 80 ... Heat exchanger, 81 ... Heat transfer tube (inner spiral grooved tube), 82 ... Heat dissipation plate, b ... Weld line spiral pitch, p ... Fin spiral pitch, θ1 ... Spiral groove twist angle, θ2 ... Weld line twist angle, WL ... Weld line.

Claims (11)

A plurality of helical grooves and a plurality of aluminum inner surface helical grooved tubes of helical fins in the circumferential direction at intervals was formed in plurality along the longitudinal direction on the inner surface, the said plurality of helical grooves plurality The spiral fins of the above are all spirally formed in the length direction of the pipe body with the same twist angle, and the pipe wall of the pipe body is inclined depending on the twist angle with respect to the length direction. texture with is formed,
Spiral weld lines are intermittently formed on the outer peripheral surface of the pipe body along the length direction of the pipe body, and spiral die marks are formed on the outer peripheral surface of the pipe body in the length direction of the pipe body. Formed along
The weld line is a portion including 30 or more pits having a diameter of 10 μm or more in an observation in an observation field of view of 180 μm × 250 μm, and the length of the weld line is 5 mm or less.
An inner spiral grooved tube characterized in that the twist angle of the spiral fin is 15 ° or more and 25 ° or less, and the twist angle of the die mark is 17.5 ° or more and 29.73 ° or less. The inner spiral grooved tube according to claim 1, wherein the weld line has a length of 1.5 mm or more and 2 mm or less. Assuming that the twist angle of the fin is θ1, the twist angle of the die mark is θ2, the inner peripheral length of the tube body is α, and the wall thickness of the tube body is β, tan θ2 = {(α + 2πβ) tan θ1} / The inner spiral grooved tube according to claim 1 or 2, wherein the tube has an α relationship. The inner spiral grooved tube according to any one of claims 1 to 3, wherein the texture is a preferentially oriented texture in the Cu orientation and the Goss orientation. The one according to any one of claims 1 to 4, wherein the texture is a structure in which the Cu orientation {112} {111} is integrated and the Goss orientation {011} {100} is integrated. The described inner spiral grooved tube. The fact that the texture having the inclination is the twist-pulled texture, and the degree of accumulation of the Cu orientation {112} {111} is smaller than the degree of accumulation of the Cu orientation {112} {111} of the drawing pipe. The inner spiral grooved tube according to claim 5. The inner spiral grooved tube according to any one of claims 1 to 6, wherein the maximum depth of the die mark is 35 μm or less. The inner spiral grooved tube according to claim 7, wherein the twist angle of the spiral die mark on the outer peripheral surface is 1.0 ° or more larger than the twist angle of the spiral fin. A heat exchanger comprising the inner spiral grooved tube according to any one of claims 1 to 8 and a heat sink coupled to the inner spiral grooved tube. The method for manufacturing an inner spiral grooved tube according to any one of claims 1 to 8.
An aluminum raw tube having a plurality of fins and grooves extending linearly along the length direction on the inner peripheral surface and a die mark extending linearly along the length direction on the outer peripheral surface is formed by extrusion. Extrusion molding process and
By performing a twist-pulling step of pulling out the raw pipe and twisting the raw pipe with a twist angle of 15 ° or more, and an empty pulling step of pulling out the raw pipe with a diameter reduction ratio of 10% or more after the pulling step, the raw pipe is pulled out. A method for manufacturing an inner spiral grooved pipe, which comprises forming an aggregate structure having an inclination depending on the twist angle with respect to the length direction of the pipe wall. The method for manufacturing an inner spiral grooved tube according to claim 10, wherein the texture is a preferentially oriented texture in the Cu orientation and the Goss orientation.

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