JP5534868B2 - Internal grooved tube and manufacturing method thereof - Google Patents

Description

  The present invention relates to an internally grooved tube used in a heat exchanger such as a refrigerator or an air conditioner and a method for manufacturing the same.

  In order to improve heat transfer, heat transfer tubes used in heat exchangers such as refrigerators and air conditioners often use internally grooved tubes with many spiral fins formed in parallel on the tube inner surface. Yes.

  In manufacturing an internally grooved tube, as in “Processing device for internally grooved tube” disclosed in Patent Document 1, a reduced diameter portion for reducing the diameter of the raw tube and a groove processing for forming a plurality of grooves on the tube inner surface In many cases, a manufacturing apparatus including a part is used.

In “Paper Processing Machine for Internally Grooved Pipe” in Patent Document 1, the reduced diameter portion is constituted by a reduced diameter die and a floating die, and the groove processed portion is formed on a rolling portion composed of a plurality of rolled balls, and on the outer periphery. And a groove plug in which a groove is cut.
The inner grooved tube can be manufactured through a diameter reduction process and a groove processing process.
The diameter reducing step is a step of reducing the diameter of the raw tube with a diameter reducing die. In the grooving process, a plurality of rolling balls (rolling elements) press the outer surface of the tube while rolling on the outer periphery of the tube, press the inner surface of the tube against a groove plug provided inside the tube, and thereby form a plurality of grooves on the inner surface of the tube. It is a process of forming.

  However, in the grooving process, when a plurality of rolling balls roll while pressing the outer circumference of the pipe, the outer surface of the raw pipe may be significantly different depending on the processing conditions such as the pressing force of the rolling ball and the size and material of the pipe. There is a difficulty that turning up occurs.

  Specifically, as shown in FIG. 6 (a), the rolling ball 33 rolls around the outer periphery of the raw tube 100a while pushing up the tube meat just before passing through the outer surface of the tube. If present, as shown in FIGS. 6 (b) to 6 (d), when the rolled ball 33 passes through a portion having the scratch 101, the wound 101 is stretched in the circumferential direction, so that the outer surface is significantly rolled up. Will occur.

  A plurality of such outer surface turn-ups appear in parallel with each other along the scratches extending in the tube axis direction on the outer surface of the tube, and it has been confirmed that the outer surface of the tube becomes scale-like (see FIG. 9). The internally grooved tube has a difficulty in quality including the properties of the tube outer surface.

  On the other hand, copper-based materials such as copper and copper alloys have been used for heat transfer tubes, but aluminum and aluminum have been used to meet the demands for excellent workability and weight reduction to accommodate a wide variety of groove shapes. The use of aluminum-based materials such as alloys is also desired.

  For example, among aluminum materials, aluminum alloys such as No. 3000 suitable for heat transfer tube processing are softer than copper. Therefore, when groove processing is performed using such an aluminum alloy base tube, Compared with the blank tube, the outer surface is more likely to be rolled up on the outer surface of the tube, resulting in deep scratches.

  These deep scratches reach 0.2 mm from the outer surface of the tube, and not only adversely affect the appearance but also reach a level where quality cannot be guaranteed.

  For example, when quality inspections such as non-contact defect detection methods and overcurrent flaw detection tests are performed on internally grooved tubes from the viewpoint of quality assurance, scratches and perforations become a significant noise source, and precision It is difficult to perform a quality inspection.

  In addition, the depth of scratches on the outer surface of the pipe must be subtracted from the pressure-resistant wall thickness in design, considering the pressure-resistant strength. The thickness of the product has to be increased, and the pressure loss increases.

  Furthermore, since the efficiency of the heat exchange device is expressed as a ratio of the energy used and the cooling capacity, if the compressor output of the main power source of the heat exchange cycle increases as the pressure loss increases, the efficiency of the overall heat exchange device will increase. It also has the disadvantage of leading to a decline.

In addition, since the corrosion resistance of the pipe is guaranteed by the wall thickness, the effective corrosion-resistant wall thickness is reduced due to scratches, resulting in a pipe having poor corrosion resistance.
Furthermore, there is a difficulty that a crack is generated due to insufficient strength of the pipe in the pipe expansion process at the time of producing the heat exchanger.

  Therefore, when an aluminum-based material tube is used, there are difficulties in terms of quality including the properties of the outer surface of the tube, which has been an obstacle to use as a heat transfer tube.

JP-A-8-192219

  Therefore, the present invention prevents the rolling-up of the outer surface of the tube when the rolling element rolls on the outer periphery of the tube in the grooving process, and the properties of the outer surface of the tube, the pressure resistance, the strength during expansion, the corrosion resistance, An object is to provide an internally grooved tube excellent in quality such as quality assurance and a manufacturing method thereof.

In the present invention, while pressing the outer surface of the raw tube with a rolling element that rolls in the circumferential direction of the tube, the inner surface of the raw tube is pressed against a grooved plug provided inside the tube, and a plurality of A method of manufacturing an internally grooved tube for performing a groove processing step for forming a groove, wherein the wound depth is 0.01 mm or less with respect to the tube outer surface of at least a length portion used as a heat transfer tube on the outer surface of the raw tube An outer surface smoothing process step for performing smoothing processing is performed, and the groove processing step is performed on the raw pipe having the outer surface smoothed.

  As an aspect of the present invention, the element tube can be made of an aluminum-based material.

  Furthermore, as an aspect of the present invention, the outer surface smoothing treatment step can be a raw tube outer surface polishing treatment step for polishing the outer surface of the tube.

In addition, the present invention is characterized in that a plurality of grooves are formed on the inner surface of the raw tube subjected to a smoothing treatment with a scratch depth of 0.01 mm or less with respect to the outer surface of the tube at least as long as the heat transfer tube. To do.

  Furthermore, as an aspect of the present invention, the raw tube can be configured such that the outer surface of the tube is polished.

  In the method for manufacturing an internally grooved tube of the present invention, a diameter reducing step for reducing the diameter of the raw tube may be performed before the groove processing step. In this case, the outer surface smoothing process may be performed before the diameter reducing process, or may be performed between the groove processing process and the diameter reducing process.

  Further, in the method for manufacturing an internally grooved tube of the present invention, a finishing step for smoothly shaping distortion of the tube outer surface of the internally grooved tube after the grooving step may be performed, but the finishing step is an essential step. Not.

  In the outer surface smoothing process, it is preferable to perform a smoothing process on the outer surface of the tube so that the outer surface of the raw tube has as few scratches having a scratch depth of 0.01 mm or more as much as possible.

The length portion used as the heat transfer tube refers to the internally grooved tube manufactured by the above manufacturing method, and is further incorporated into a heat exchanger after a process such as tube expansion, and is actually used as a final processed product. The length part of the heat transfer tube in the tube axis direction is shown.
In other words, the smoothing process need not be performed over the entire length of the raw tube drawn in the manufacturing process of the internally grooved tube.

  The outer surface smoothing treatment step is not limited to the raw tube outer surface polishing treatment step, but the outer surface of the tube is dissolved by an electrolytic solution or a special agent, or the wound on the outer surface of the tube is impregnated with a powder or liquid. It may be smoothed.

  The raw tube outer surface polishing treatment step may be automatically performed by a polishing apparatus, or may be manually performed using a polishing tool or a file.

  In the raw tube outer surface polishing process, a polishing method such as buff polishing, lapping polishing, and shot blasting is not particularly limited.

  The aluminum-based material includes an aluminum material, an aluminum alloy material, or the aluminum material or a clad material of the aluminum alloy material.

  The element tube is not limited to the aluminum material, and is not particularly limited as long as it is a metal having excellent thermal conductivity, such as a copper material.

  The rolling element is not limited to a rolled ball, for example, and can be configured by using a roller, and a combination of a rolled ball and a roller.

According to the present invention, when the rolling element rolls on the outer circumference of the pipe in the grooving step, the pipe outer surface is prevented from being turned up, and the pipe outer surface properties, pressure resistance, pipe expansion strength, and corrosion resistance are prevented. Further, it is possible to provide an internally grooved tube excellent in quality such as quality assurance and a manufacturing method thereof.
In particular, even with an aluminum-based material, it is possible to provide an internally grooved tube excellent in the above-described quality and a manufacturing method thereof.

Structure explanatory drawing of the manufacturing apparatus used for manufacture of the inner surface grooved pipe | tube of this embodiment. Flow explanatory drawing of the manufacturing method of the inner surface grooved pipe of this embodiment. Explanatory drawing explaining the measuring method of the damage | wound of a pipe outer surface. The photograph of the pipe | tube outer surface part of the inner surface grooved pipe | tube of this embodiment after a tape peeling test. The expanded cross-sectional photograph of the pipe | tube outer surface part of the inner surface grooved pipe | tube of this embodiment. Explanatory drawing which showed typically the appearance of the outer surface turning up generation | occurrence | production. The photograph of the pipe outer surface part of the inner surface grooved pipe of the comparative example after the tape peeling test. The expanded cross-sectional photograph of the pipe outer surface part of the inner surface grooved pipe of a comparative example. The enlarged front photograph of the pipe outer surface part of the inner surface grooved pipe of a comparative example.

An embodiment of the present invention will be described below with reference to the drawings.
As shown in FIGS. 1 and 2, the manufacturing method of the internally grooved tube of the present embodiment includes a plurality of rolling balls 33 as rolling elements that roll on the outer surface of the raw tube 1 c along the circumferential direction of the tube. Of the inner surface grooved tube 1e for pressing the inner surface of the element tube 1c against the grooved plug 32 provided inside the tube and forming a plurality of grooves on the inner surface of the element tube 1c. It is a manufacturing method. Furthermore, the outer surface smoothing process step (11A) is performed on the outer surface of the raw tube 1a, and the groove processing step 31A is performed on the raw tube 1c subjected to the smoothing process. .

  The outer surface smoothing treatment step (11A) is a raw tube outer surface polishing treatment step 11A for polishing the outer surface of the raw tube 1a. By the polishing treatment, the long surface used as at least a heat transfer tube in the raw tube 1a. The depth of damage is 0.01 mm or less with respect to the outer surface of the tube.

The manufacturing apparatus 10 of the inner surface grooved tube of this embodiment is explained in full detail using FIG.
FIG. 1 is a cross-sectional view of a manufacturing apparatus 10 that manufactures the inner grooved tube 1e (, 1d) in the present embodiment while drawing the raw tubes 1a to 1c in the drawing direction X.
The manufacturing apparatus 10 is provided with a reduced diameter portion 21, a groove processing portion 31, and a finishing processing portion 41 in order from the upstream side to the downstream side in the drawing direction X, and further includes a drawing device 51 on the downstream side. The inner pipe 1e is manufactured by continuously processing the elementary pipes 1a to 1c according to the configuration.

  The reduced diameter portion 21 is inserted into the element tube 1b so that the cylindrical die 22 for reducing the diameter of the passing element tube 1b and the inner periphery of the element tube 1b narrowed by the die 22 are pressed. Floating plug 23 is provided.

  The die 22 has a die hole 22a that opens in a conical shape so that the upstream portion has a larger diameter toward the upstream side.

  Furthermore, the floating plug 23 has a conical outer peripheral surface having a small diameter toward the downstream side in the downstream portion.

  Thereby, the die 22 and the floating plug 23 are engaged with each other so as to sandwich the element tube 1b therebetween.

  The groove processing section 31 includes a grooved plug 32 having a plurality of spiral grooves 32 a formed on the outer periphery and a plurality of rolling balls 33.

  The grooved plug 32 is inserted into the raw tube 1 c and is connected to the floating plug 23 via a connecting rod 34 so as to be independently rotatable. The plurality of rolling balls 33 are provided with equal distribution in the pipe circumferential direction so as to rotate and roll while revolving around the axis, and press the raw pipe 1c outside the pipe 1c. .

  The finishing portion 41 includes a shaping die 41, and the inner grooved tube 1d passes through the die hole 41a of the shaping die 41. For example, the finishing portion 41 is generated by pressing the rolling ball 33 in the groove processing portion 31. The process of removing the distortion of the outer surface of the tube and shaping the outer surface of the tube smoothly.

  The drawing device 51 includes a take-up drum 52 and a take-up motor M1, and winds around the take-up drum 52 while pulling the inner grooved tube 1e by the rotational drive of the motor M1.

A method of manufacturing the inner grooved tube 1e of the present embodiment using the manufacturing apparatus 10 will be described in detail with reference to FIG.
In the raw tube outer surface polishing step 11A, the entire tube circumference is polished until the depth of the outer surface of the raw tube 1a becomes 0.01 mm or less.

  The polishing treatment may be performed manually using a polishing tool or a file on the outer surface of the raw tube 1a before the grooving step 31A, or may be automatically performed by a polishing apparatus.

  Furthermore, in the raw tube outer surface polishing treatment step 11A, the raw tube 1a may be subjected to a polishing treatment as part of a process of continuously processing the raw tube 1a while being drawn in the drawing direction X by the drawing device 51, or You may perform a grinding | polishing process with respect to the raw material pipe | tube 1a by another process before carrying out continuous processing, drawing the raw material pipe | tube 1a.

  As described above, when a polishing process is performed on the raw tube 1a as part of the process of continuously processing the raw tube 1a, for example, as shown by the phantom line in FIG. By installing the tube outer surface polishing section 11, the outer surface of the raw tube 1a can be automatically polished.

  Further, in this case, the raw tube outer surface polishing portion 11 is not shown, but holds, for example, a polishing portion in which abrasive grains are attached to a flexible base cloth, and the polishing portion pressed against the raw tube 1a. It can be configured with a movable part that polishes the outer surface of the raw tube while rotating or sliding.

  Subsequently, in the diameter reducing step 21A, the raw tube 1b is squeezed with a die 22, and the inner surface of the tube is pressed against the floating plug 23 to reduce the diameter of the raw tube 1b.

In the groove processing step 31A, the raw tube 1c is reduced in diameter by the grooved plug 32 and the plurality of rolling balls 33, and the plurality of rolling balls 33 roll into the grooved plug 32 while rolling around the pipe circumference. The tube inner surface is pressed to form a plurality of spiral grooves having a predetermined lead angle and height on the tube inner surface.
Finally, in the shaping process 41A, the shaping groove 41 is used to shape the inner grooved tube 1d to a predetermined outer diameter, whereby the inner grooved tube 1e of the present embodiment can be obtained.
By the manufacturing method described above, the following various actions and effects can be obtained.
In the manufacturing method of the inner grooved tube 1e, the outer surface of the raw tube 1a is subjected to a raw tube outer surface polishing process 11A (outer surface smoothing process) for smoothing, and the outer tube is subjected to a smoothing process on the raw tube 1c. On the other hand, since the grooving step 31A is performed, when the rolling ball 33 rolls on the outer periphery of the pipe in the grooving step 31A, it is possible to prevent the occurrence of so-called outer surface curling, in which scratches are stretched in the circumferential direction. it can.

  As a result, it is possible to prevent the scratches existing on the outer surface of the raw tube 1a from deepening or increasing the number of scratches. The outer surface properties, pressure resistance, tube expansion strength, corrosion resistance, quality assurance It is possible to obtain the internally grooved tube 1e which is excellent in quality such as property.

  In addition, the groove processing section 31 is not changed or improved, or the processing time required in the groove processing step 31A does not increase, and the existing groove processing section 31 and the groove processing step 31A remain as described above, and the inner groove is provided. The quality of the tube 1e can be improved.

  Further, in the raw tube outer surface polishing step 11A, the wound depth is reduced to 0.01 mm or less with respect to at least the length of the tube outer surface used as the heat transfer tube in the raw tube 1a. Can be further prevented, and the above-described performance and quality of the internally grooved tube 1e can be significantly improved.

  Further, as described above, in the manufacturing method of the inner surface grooved tube 1e, the outer surface of the raw tube 1a is subjected to the raw tube outer surface polishing process step 11A for performing the smoothing process, and the outer tube is subjected to the smoothing process on the outer tube 1a. In contrast, this is a method of performing the groove processing step 31A.

  Therefore, when the raw tube 1a is made of an aluminum material such as, for example, an aluminum material, an aluminum alloy material, or the aluminum material, or a clad material of the aluminum alloy material, the tube 1a is similarly turned up to the outer surface of the tube. It is possible to provide the inner grooved tube 1e which is excellent in performance and quality described above.

  Therefore, a lightweight heat transfer tube can be obtained by utilizing the characteristics of the aluminum-based material, and the inner grooved tube 1e can be manufactured with excellent production efficiency by utilizing the property of the aluminum-based material, which is excellent in workability. it can.

  Furthermore, in addition to conventionally used materials such as copper and copper alloys, aluminum-based materials can also be added to the material selection in manufacturing the internally grooved tube 1e, thereby widening the range of material selection. it can.

  Therefore, according to the present invention, it is possible to select an optimum material from the viewpoints of application and material cost, and for example, the influence of fluctuations in material cost can be reduced.

  Furthermore, the outer surface of the raw tube 1a can be physically and mechanically smoothed by smoothing the outer surface of the raw tube 1a by polishing the outer surface of the tube as in the process 11A for polishing the outer surface of the raw tube. For example, a desired smooth surface can be reliably obtained according to the degree of polishing, such as a smooth surface having a scratch depth of 0.01 mm or less on the outer surface of the element tube 1a.

(Processing experiment)
Subsequently, an inner grooved tube was produced using various elementary tubes (material tubes), and a processing experiment was conducted to verify the effectiveness of the manufacturing method described above.

  In this processing experiment, as shown in Table 1, two raw pipes 1b (1b1, 1b2) of Examples 1 and 2 were prepared as raw pipes that had passed through the raw pipe outer surface polishing step 11A in advance, and the outer pipe surface was polished. Three element tubes 100a (100a1, 100a2, 100a3) of Comparative Examples 1 to 3 were prepared as element tubes that did not go through the processing step 11A.

Furthermore, in this processing experiment, the manufacturing method described above in order, that is, the diameter reducing step 21A and the groove processing step are performed in order for each of the raw tube 1b of Examples 1 and 2 and the raw tube 100a of Comparative Examples 1 to 3. 31A and finishing process 41A were performed to produce an internally grooved tube.
In addition, the processing experiment which produces these inner surface grooved pipes was made into Experiment No. 1-5, respectively.

  The raw tube 1b of Examples 1 and 2 and the raw tube 100a of Comparative Examples 1 to 3 both use an aluminum tube having an outer diameter of φ20 mm, a wall thickness of 0.6 mm, and a material of A303, and the outer diameter is An internally grooved tube having a diameter of 10 mm and a wall thickness of 0.5 mm shall be produced.

Table 1 shows the maximum flaw depth and the number of flaws on the outer surface of the pipe 1b of Examples 1 and 2 and the pipe 100a of Comparative Examples 1 to 3 as experimental conditions.
Here, as shown in FIG. 3A, the maximum depth of damage on the outer surface of the tube is obtained by observing a cross section of the raw tube 100a (, 1b) before the diameter reducing step 21A, and A line perpendicular to the wound tip was drawn from the outer surface, and the radial distance from the outer surface to the wound tip was defined as the wound depth d and measured. The number of flaws on the outer surface of the tube is the number of flaws having a flaw depth d of 0.01 mm or more measured as defined above.

  Specifically, with respect to the maximum flaw depth and the number of flaws on the tube outer surface of the tube, since the tube 100a of Comparative Examples 1 to 3 has not undergone the tube outer surface polishing step 11A in advance as described above, There are many scratches of 0.01 mm or more on the outer surface of the tube, and the maximum scratch depth is larger than 0.01 mm.

  On the other hand, since the pipe outer surface of each of the pipes 1b of Examples 1 and 2 has undergone the pipe outer surface polishing process 11A, the pipe outer surface has no scratch of 0.01 mm or more, or There are few scratches with a maximum scratch depth greater than 0.01 mm.

  In addition, although the number of scratches of 0.01 mm or more was counted in the raw tube 100a2 of Example 2, since the maximum scratch depth was 0.01 mm, the depth of these three scratches was Is also found to be 0.01 mm.

  Further, as the manufacturing apparatus 10 used in this processing experiment, a grooved plug 32 having an outer diameter of 9 mm, a groove depth of 0.20 mm, and a spiral groove lead angle of 30 ° with respect to the tube axis direction was used. .

  In this processing experiment, as an experimental result, the outer surface of the internally grooved tube was observed for scratches and the outer surface turned up, and the quality of the internally grooved tube was evaluated by an eddy current flaw detection test.

Specifically, in the observation of scratches on the outer surface of the inner surface grooved tube 1e (1e1, 1e2) of Examples 1 and 2 and the inner surface grooved tube 101a (101a1, 101a2, 101a3) of Comparative Examples 1 to 3, In the cross section of the inner grooved tube after the processing step 31A, a line perpendicular to the outer surface of the tube is drawn down from the outer surface of the scratches 102 and 103 as shown in FIG. The distance was defined as the flaw depth d and measured.
Further, the number of scratches on the outer surface of the tube is a number obtained by counting scratches having a scratch depth of 0.01 mm or more as measured according to the definition of the scratch depth described above.

As for the outer surface turn-up, “×” indicates the tube where the wound that was judged to be turned-up was present among the observed scratches, and “○” indicates that the tube was not observed.
In addition, there are many scratches on the inner grooved tube in addition to the outer surface curling, but the scratches caused by the outer surface curling run obliquely with respect to the outer surface of the tube in a cross-sectional view of the tube, and the tip is Since it has the feature of being thin, it can be easily discriminated. For example, 102 in FIG. 3 (b) is an outer surface turning-up, and 103 is not an outer surface turning-up.

  In the eddy current flaw detection test, first, the outer surface of each of the inner surface grooved tubes 1e and 101a obtained in the example and the comparative example is intentionally scratched in advance (this is referred to as “reference outer surface defect”). The same applies hereinafter), and whether or not the reference external surface defect could be detected by a known eddy current testing machine was verified.

  In this eddy current flaw detection test, there is a large amount of upset on the outer surface of the tube, and if there are a large number of them, noise due to eddy current flaw detection becomes large and it becomes difficult to detect the reference outer surface defect. Whether it is possible or not is an index that indicates the degree of depth and depth of the crease occurring on the outer surface of the pipe.

  Therefore, in the eddy current flaw test, those that could detect the reference outer surface defect were evaluated as “◯”, those that could not be detected were “×”, and those that could or could not be detected depending on the conditions were “△”. evaluated.

  When processing was performed under the above experimental conditions and the results were compared, the results shown in Table 2 below were obtained.

As shown in Table 2, regarding the maximum flaw depth on the outer surface of the internally grooved tube, in the case of the internally grooved tube 101a of Comparative Examples 1 to 3, the maximum flaw depth is greater than when measured in the case of the raw tube 100a. The depth was deep.

  On the other hand, in the case of the inner grooved tube 1e of Examples 1 and 2, the maximum flaw depth was not changed from the value measured in the case of the raw tube 1b, and it became clear that the flaw was not deepened.

  Furthermore, regarding the number of scratches on the outer surface of the inner surface grooved tube, in the case of the inner surface grooved tube 101a of Comparative Examples 1 to 3, all of them were increased several times as much as when measured with the raw tube 100a. On the other hand, in the case of the inner grooved tube 1e of Examples 1 and 2, it was the same as or substantially the same as that of the raw tube 1b.

  In the case of the inner surface grooved tube 101a of Comparative Examples 1 to 3, the inner surface grooved tube was turned into an evaluation result of “x”, whereas the inner surface grooved tube of Examples 1 and 2 In the case of 1e, the evaluation results were “◯” in all cases, and no scratches that were judged to be turned up were observed.

  Regarding the eddy current flaw detection test, the inner surface grooved tube 101a1 of Comparative Example 1 was “Δ”, and the inner surface grooved tubes 101a2 and 101a3 of Comparative Examples 2 and 3 were both evaluated as “x”. On the other hand, in the case of the inner grooved tube 1e of Examples 1 and 2, both were evaluated as “◯”, and no scratches judged to be turned up on the outer surface could be confirmed.

  Further, in addition to the observation and test described above, a tape peeling test for observing the properties of the outer surface of the tube when the tape attached to the outer surface of each of the inner surface grooved tubes 1e1 and 101a3 of Example 1 and Comparative Example 3 is removed. Was done.

  Regarding the tape peeling test, when the tape attached to the outer surface of the inner grooved tube 101a3 of Comparative Example 3 was peeled off, as shown in FIG. When I peeled off, I got up and got up and got in a standing position. From this, it was confirmed that the outer surface of the internally grooved tube 101a3 of Comparative Example 3 has a large number of scratches due to rolling up.

  On the other hand, with respect to the inner grooved tube 1e1 of Example 1, when the tape attached to the outer surface of the tube was peeled off, the outer surface of the tube remained smooth without any rustling as shown in FIG. From this, it was confirmed that the outer surface of the internally grooved tube 1e1 of Example 1 did not have any scratches due to turning up.

Finally, the properties of the tube outer surfaces of the inner grooved tubes 1e1 and 101a3 of Example 1 and Comparative Example 3 were observed.
Specifically, the properties when the tube outer peripheral portion of the inner surface grooved tube 101a3 of Comparative Example 3 is viewed in cross section and the properties when the tube outer surface is viewed from the front are shown in FIG. 8 and FIG. It is shown.

  As shown in FIG. 8, on the outer surface of the internally grooved tube 101a3 of Comparative Example 3, due to the occurrence of significant outer surface curling, the scratches present on the base tube 100a3 were stretched in the circumferential direction, resulting from the outer surface curling. 102 was confirmed.

  Furthermore, as shown in FIG. 9, the inner grooved tube 101a3 of Comparative Example 3 appeared parallel to each other with a plurality of turned-up portions extending in the tube axis direction on the outer surface of the tube, and a scaly tube outer surface was confirmed.

  In contrast, the properties of the inner circumferential grooved tube 1e1 of Example 1 when viewed from the cross section of the tube are as shown in FIG.

  As shown in FIG. 5, only irregularities of about 0.005 mm were confirmed on the tube outer surface of the inner grooved tube 1e1 of Example 1, and no scratches due to the outer surface turning up were confirmed.

  Thus, it can be seen that there is a great difference in appearance as well as a difference in quality as observed in the properties of the tube outer surfaces of the inner surface grooved tubes 1e1 and 101a3 in Example 1 and Comparative Example 3.

  From the experimental results described above, by making the maximum flaw depth on the outer surface of the raw tube 0.01 mm or less, rolling with the rolling ball 33 in the grooving step 31A is performed on an aluminum tube that has been difficult to process conventionally. Even if it performed, it was able to process without the depth of the damage | wound after the groove | channel processing process 31A of a pipe outer surface becoming deep, or increasing the number.

  Therefore, the inner grooved tube 1e having greatly improved quality such as the properties of the outer surface of the tube, the pressure resistance, the strength at the time of expansion, the corrosion resistance, and the quality assurance can be obtained by the manufacturing method of the inner grooved tube described above. We were able to demonstrate.

  The present invention is not limited to the above-described embodiments, and can be configured in various embodiments.

  In the correspondence between the configuration of the present invention and the above-described embodiment, the rolling element corresponds to the plurality of rolling balls 33.

DESCRIPTION OF SYMBOLS 1a, 1b, 1c ... Elementary tube 1d, 1e ... Inner surface grooved tube 11A ... Elementary tube outer surface polishing process 21A ... Diameter reduction step 31A ... Groove processing step 33 ... Rolled ball 32 ... Slotted plug

Claims (6)

While pressing the outer surface of the raw tube with a rolling element that rolls along the circumferential direction of the tube, the inner surface of the raw tube is pressed against a grooved plug provided inside the tube to form a plurality of grooves on the inner surface of the raw tube. A manufacturing method of an internally grooved tube for performing a grooving process,
An outer surface smoothing process is performed on the outer surface of the raw tube to perform a smoothing process with a wound depth of 0.01 mm or less with respect to the outer surface of the tube at least as a heat transfer tube ,
A manufacturing method of an internally grooved tube, wherein the groove processing step is performed on a raw tube whose outer surface has been smoothed. The manufacturing method of the internally grooved pipe according to claim 1 , wherein the base pipe is made of an aluminum-based material. The manufacturing method of the inner surface grooved pipe according to claim 1 or 2 , wherein the outer surface smoothing step is a raw tube outer surface polishing step for polishing the outer surface of the tube. An internally grooved tube in which a plurality of grooves are formed on the inner surface of a raw tube that has been subjected to a smoothing treatment with a scratch depth of 0.01 mm or less with respect to the outer surface of the tube at least as long as the heat transfer tube. The internally grooved tube according to claim 4 , wherein the base tube is made of an aluminum-based material. The inner grooved tube according to claim 4 or 5 , wherein the raw tube has a configuration in which a tube outer surface is polished.