JPH09155540A - Production of inner face grooved heat transfer tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the production method to produce an inner face grooved heat transfer tube having narrow, high fins in a low cost and high reliability. SOLUTION: The method consists of a fin forming process to form a fin and groove on one face at least of the bar stock T by passing between a pair of fin forming rolls 14, 16 while running the bar stock T of copper or copper alloy annealed after cold rolling, a tube forming process to form the bar stock T formed with the fin and groove to a tubular with passing plural forming rolls 20 and a welding process to weld both end edges of the bar stock T formed to a tubular with heating and butting. Further, before the fin forming process, a surface roughness of both faces S1, S2 of the bar stock T is made to 0.05-0.30μm Ra.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a heat transfer tube with an inner groove, which adopts an electric resistance welded pipe method.

[0002]

2. Description of the Related Art An inner grooved heat transfer tube of this type is mainly used as an evaporator tube or a condenser tube in a heat exchanger such as an air conditioner or a refrigerator, and recently has a spiral shape over the entire inner surface. A heat transfer tube in which spiral fins are formed between grooves by forming such grooves is widely commercially available.

The heat transfer tube, which is currently the mainstream, is a metal tube obtained by passing a floating plug having a spiral groove formed on the outer peripheral surface inside a seamless (seamless) tube obtained by drawing or extruding. It is manufactured by a method of rolling a spiral groove and fins over the entire inner peripheral surface of the fin. In a commonly used heat transfer tube having an outer diameter of about 10 mm, the fin height is 0.15 to 0. 20m
m, fin pitch (distance between vertices of adjacent fins)
Is 0.45 to 0.55 mm, the bottom width of the groove formed between the fins is 0.2 to 0.3 mm, and the angle formed by both side surfaces of each fin is about 50 to 60 °. In the drawing process using the floating plug, it is technically difficult to form thin fins higher than the above range.

By the way, when the heat transfer tube with the inner groove as described above is used as the condenser tube, the heat transfer gas is introduced from one end of the heat transfer tube, condensed while releasing the heat, and the heat transfer liquid is fed from the other end. In order to improve the condensation efficiency in this process, it is necessary to increase the height of the fins to improve the liquid drainage at the apex of the fins and promote direct contact between the fins and the heat transfer gas. Considered to be effective.

Therefore, the inventors of the present invention, instead of the seamless pipe, rolled up a long metal plate material in the width direction and welded both side edges which are abutted to each other to obtain a metal tube by the "electric resistance welding method".
It was attempted to make the fins on the inner surface of the heat transfer tube higher than before by adopting the method for manufacturing a small diameter heat transfer tube. According to the electric resistance welded pipe method, the fins to be formed on the inner surface can be rolled in the state of the metal plate material, and tall fins can be formed regardless of the outer diameter of the heat transfer tube.

However, in reality, it was confirmed that the condensation efficiency of the heat transfer tube was not improved so much even if the fins higher than the conventional fins were formed. The inventors of the present invention have made detailed investigations into this cause and have obtained the following findings. That is, in the conventional heat transfer tube with internal groove, the fin has a triangular cross-section with a large apex angle. The heat transfer tube is blown up along a gentle slope, and the tip of the heat transfer tube is covered with the heat transfer liquid, so that the effect of exposing the tip of the fin is small. As a result, the effect of improving the heat exchange efficiency was limited.

Therefore, the present inventors have attempted not only to make the fins taller but also to make them thinner, as illustrated in FIG. The heat transfer tube 1 shown in this figure is a metal tube having a circular cross section, and a large number of parallel fins 2 that form a constant angle with the tube axis are formed in a spiral shape over almost the entire inner surface of the tube, and they are adjacent to each other. There are spiral grooves 3 between the fins 2. If the angle between both side surfaces of the fin 2 is less than 40 °, the heat transfer liquid in the groove is less likely to be blown up along the side surface of the fin due to the wind pressure of the heat transfer vapor flowing at high speed in the heat transfer tube, and the heat exchange efficiency is improved. It turns out to be expensive. Further, a welded portion 4 is formed by electric sewing at one location on the peripheral wall of the heat transfer tube 1, and finless portions 5 extending parallel to the central axis of the heat transfer tube 1 are formed on both sides of the welded portion 4, Each fin 2 is divided by this finless portion 5 as shown in FIG.

[0008]

By the way, it has been found that the following specific problems occur when manufacturing the thin and tall fins 2 as described above. In the method of manufacturing the heat transfer tube 1, in order to form the fins 2 and the spiral grooves 3 on the plate material T made of copper or copper alloy, as shown in FIG.
The sheet material T is rolled between the smooth roll 7 and the smooth roll 7, but under the same rolling conditions as when forming a normal low fin, the material does not reach the inside of the rolling groove 8 of the grooved roll 6. It was observed that the fins 2 did not enter and the height of the fins 2 was insufficient.

In order to prevent such rolling defects,
The rolling pressure applied between the grooved roll 6 and the smooth roll 7 has to be made considerably higher than before, but if the rolling pressure is increased, not only the driving energy of the apparatus increases and the manufacturing cost is increased, but also the plate strip It was found that both side edges of the material T did not become linear but slightly wavy. If such a wavy shape occurs, a gap may be created on the abutting surfaces in the welding process, and the quality of the welded portion may become uneven.In order to improve the reliability of the welded portion when the wavy shape is remarkable, In addition, both edges had to be scraped off to form a straight line.

By the way, such rolling defects do not always occur in the same manner, and even if the same processing conditions are adopted,
The present inventors have found that in certain cases, the occurrence of rolling defects is suppressed. Therefore, the inventors examined the conditions under which rolling defects are less likely to occur, and found that the rolling defects are related to the heat treatment conditions and surface roughness of the strip material before rolling. . That is, when using an annealed copper or copper alloy sheet material, the surface roughness of the sheet material is usually (about 0.03 μmRa is general).
If it is larger than this, it becomes easy to form a high fin with a relatively small rolling force. However, if the surface roughness of the strip material is too large, elliptical slacks are formed at intervals in the widthwise central portion of the strip material, which hinders pipe forming.

The present invention has been made on the basis of the above findings, and it is an object of the present invention to provide a method for manufacturing an inner grooved heat transfer tube which can manufacture an inner grooved heat transfer tube having thin and high fins at low cost and with high reliability. I am trying.

[0012]

In order to solve the above-mentioned problems, a method of manufacturing a heat transfer tube with internal groove according to the present invention is directed to running a strip material made of copper or copper alloy that has been annealed after cold rolling. And a fin forming step of forming fins on at least one surface of the plate material through at least a pair of fin forming rolls, and a tube for forming the plate material having the fins formed into a tubular shape through a plurality of forming rolls. The method includes a forming step and a welding step of heating both end edges of the tubular material that has been tubularly formed and then abutting and welding the fin material. Prior to the fin forming step, the surface roughness of both surfaces of the sheet material is set to 0. It is characterized in that it is set to 0.05 to 0.30 μmRa.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a front view showing an example of an apparatus used for carrying out an embodiment of a method for manufacturing a heat transfer tube with internal grooves according to the present invention. First, the structure of this device will be described. In the figure, reference numeral 10 is an uncoiler that continuously feeds a strip material T having a constant width, and the delivered strip material T passes through a pair of pressing rolls 12 and forms a pair. The fins 2 and the spiral grooves 3 are formed by passing between the grooved roll 14 and the smoothing roll 16 (generally referred to as fin forming rolls). In this embodiment, the fins 2 and the spiral grooves 3 are formed only on the front surface S1 of the strip material T, and the back surface S2 is left smooth.

The grooved roll 14 and the smooth roll 16 are
As shown in FIGS. 2 and 3, the shafts 34,
It is rotatably supported by the frame 38 via 36. The grooved roll 14 and the smooth roll 16 may be driven in synchronization with the traveling of the strip material T, or may be driven and rotated without being driven.

As shown in FIG. 4, the grooved roll 14 has a grooved roll body 14A having a rolling groove 40 formed on the outer peripheral surface thereof.
And a pair of side rolls 14B fixed on both sides thereof, the fins 2 are formed on the plate material T by the rolling grooves 40, while the ridges 42 between the rolling grooves 40 form a spiral. The groove 3 is formed. Although the leading edge of the protrusion 42 is chamfered, it may not be chamfered.

In this embodiment, it is desirable to make the fins 2 formed on the inner surface of the heat transfer tube 1 high and thin, so that as shown in FIG. 5 (a cross-sectional view orthogonal to the longitudinal direction of the rolling groove 40). The angle α formed by both sides of the rolling groove 40 is 1
The angle is 0 to 40 °, more preferably 15 to 30 °. This is because if the angle α is less than 10 °, it will be difficult to manufacture even with the electric resistance welded pipe method, and if it is 40 ° or more, the heat exchange efficiency cannot be remarkably improved. However, the present invention is not limited to the above range.

As shown in FIG. 5, the ratio of the depth D of the rolling groove 40 to the opening width W of the rolling groove 40 is not limited in the present invention, but is 1.1: 1 to 2.5: It is preferably 1 and more preferably 1.2: 1 to 2.3: 1. The thinner the fin 2 formed, the spiral groove 3
This is because the volume of the liquid is relatively increased, the drainage property at the tips of the fins 2 is improved, and the heat exchange efficiency can be improved. The opening width W is a value measured in a direction perpendicular to the longitudinal direction of the rolling groove 40. When both edges of the rolling groove 40 are chamfered, the side surface of the rolling groove 40 is extended. The line of intersection between the surface and the tip surface of the protrusion 42 is used as the reference point for measurement.

The outer peripheral surface of the side roll 14B is a taper surface whose outer diameter decreases toward the outside in the axial direction. This is a plate surface when the fin 2 is formed on the plate material T as shown in the drawing. This is because the both side edge portions 44 of the strip T are warped back to the side roll 14B side.

As shown in FIG. 1, the sheet material T grooved by the grooved rolls 14 and the smooth rolls 16 is gradually rolled into a tubular shape through a pair of rolls 18 and a plurality of pairs of forming rolls 20. The seam guide roll 21 keeps the gap between the opposite edges to be abutted constant, and the side edges are heated by the induction heating coil 22. Plate material T formed into a tube and heated
Is passed through a pair of squeeze rolls 24, and the both side edges heated by being pushed from both sides are butted,
Welded. A bead cutter 26 for cutting the bead is provided on the outer peripheral surface of the heat transfer tube P welded in this way, because a bead is formed by the molten material protruding.

The heat transfer tube P whose bead is cut is the cooling tank 28.
After being passed through and forcedly cooled, a plurality of pairs of sizing rolls 30 are passed through and the diameter is reduced to a predetermined outer diameter. The heat transfer tube P thus reduced in diameter is wound up by the rough coiler 32.

Next, one embodiment of a method for manufacturing the heat transfer tube with inner groove according to the present invention using the above apparatus will be described. The main feature of this method is that, as the sheet material T, a sheet material made of copper or copper alloy that has been annealed after cold rolling is used, and before performing the groove rolling by the grooved roll 14, the sheet material is The surface roughness of both surfaces S1 and S2 of the strip T is 0.05 to 0.3.
The point is to set it to 0 μmRa.

The reason why the strip material made of copper or copper alloy that has been annealed after cold rolling is used as the strip material T is that if a strip material that has not been recrystallized by annealing is used. Since the elongation of the material is small, the rolling pressure by the grooved roll 14 must be increased, which not only increases the running cost of the apparatus but also shortens the life of the grooved roll 14.

As the material of the strip material T, any material can be used as long as it is copper or a copper alloy. In particular, deoxidized copper (eg JIS 12) which is widely used as a material for heat transfer tubes.
20 alloy), the present invention is suitable. However, the present invention is not limited to application to this material, and the same effect can be obtained when applied to oxygen-free copper, tough pitch copper, brass, brass, admiralty brass, and the like. As an annealing treatment condition after cold rolling in any of the above materials, heat treatment at 350 to 450 ° C. for 30 to 90 minutes can be exemplified.

In any of the materials, the Vickers hardness of the sheet material T before fin formation is preferably 50 to 150 Hv, and more preferably 50 to 100 Hv. This is because if it is in the range of 50 to 150 Hv, the rolling pressure can be reduced even when manufacturing thin and high fins, and the manufacturing cost can be reduced. However, the effect of the present invention can be obtained even if it is out of this range. The crystal grain size of the strip material T is preferably 0.005 to 0.04 mm by recrystallization, and more preferably 0.01 to 0.04 mm.
It is set to 0.03 mm. However, the effects of the present invention can be obtained even if the content is out of these ranges.

On the other hand, the reason for setting the surface roughness of both surfaces S1 and S2 of the plate material T to 0.05 to 0.30 μmRa is that the elongation in the surface direction of the plate material T is appropriately suppressed and the material is This is because it is easy for the fins to flow into the rolling groove 40, and even when thin and high fins are formed, fin rolling defects can be prevented. A more preferable range of the surface roughness of the strip material T is 0.07 to 0.
20 μmRa, more preferably 0.10 to 0.17 μm
mRa. If the surface roughness is less than 0.05 μmRa, the elongation of the material is large, and the material tends to flow in the direction parallel to the sheet material T, and the material does not sufficiently enter the rolling groove 40. Not only is it difficult to roll the thin and tall fins 2, but also when the rolling force is increased, corrugated shapes are likely to occur at both ends in the width direction of the strip material T. Also, 0.30
When it is larger than μmRa, the elongation of the material is poor, the material locally expands at the central portion of the plate material T, and a large number of slacks (intermediate elongation) such as ellipses occur in the longitudinal direction of the plate material T. Electric sewing becomes difficult.

The surface roughness of the sheet material T is preferably the same on both surfaces S1 and S2, but may not be the same as long as it is within the above range. As a means for controlling the surface roughness of the plate material T within the above range, any conventionally used polishing method, surface treatment method, or the like can be used and is not particularly limited.

Conventionally, since the surface roughness of the sheet material has not been taken into consideration, a sheet material much finer than 0.05 μmRa has been used. Therefore, it is considered that the material flow is likely to occur in the direction parallel to the strip material T during rolling, and the material does not enter the rolling groove 40 sufficiently, so that it is difficult to form a thin and high fin.

The method of this embodiment is applied to a general outer diameter of 3-1.
When applied to the production of a heat transfer tube of about 5 mm, the thickness of the plate material T before fin formation is preferably 0.30 to 1.20 mm, and the depth of the rolling groove 40 (= fin 2 Is preferably 20 to 60% of the thickness of the plate material T.

Further, in this case, the surface roughness of the tip end surface of the protrusion 42 of the grooved roll 14 shown in FIGS. 4 and 5 is 0.3.
˜1.2 μmRa, more preferably 0.5 to 1.0 μmRa. The tip end surface of the protruding portion 42 is a portion that forms the bottom surface of the spiral groove 3, and affects the elongation of the plate material T as well as the surface roughness of the plate material T itself. When the surface roughness of the tip end surface of the protruding portion 42 is within the above range, the effect of preventing the rolling defect is further enhanced in combination with the effect of defining the surface roughness of the plate material T, and the groove rolling is performed. The driving force required for is even smaller. The surface roughness of the outer peripheral surface of the smooth roll 16 is also preferably 0.3 to 1.2 μmRa.

The above-described plate material T and rolling conditions are adopted, and the procedure and other processing conditions when fin formation and electric resistance welding are performed by the apparatus shown in FIG.
That is, a strip material T having a constant width is continuously fed from the uncoiler 10, and the strip material T fed out is passed between the grooved roll 14 and the smooth roll 16 through the pair of pressing rolls 12 to form the grooved portion. The roll 2 forms the fin 2 and the spiral groove 3.

As shown in FIG. 1, the grooved plate material T should be gradually rolled into a tubular shape through a pair of rolls 18 and a plurality of forming rolls 20 arranged in a pair, and then abutted by a seam guide roll 21. Keep the distance (gap) between both edges constant. Then, the both side edges are heated by passing through the induction heating coil 22, and further pushed by pushing the pair of squeeze rolls 24 from both sides, so that the both side edges are abutted and welded. Since the molten material protruding to the outer peripheral surface of the heat transfer tube P becomes a bead, the bead cutter 26 cuts this bead.

The heat transfer tube P with the bead cut is placed in the cooling tank 28.
Through a sizing roll 30 in which a plurality of pairs are arranged, and the diameter is reduced to a predetermined outer diameter. The heat transfer tube P thus reduced in diameter is wound up by the rough coiler 32. However, the above steps are for the case of using the apparatus of FIG. 1, and it goes without saying that the steps may be changed according to the configuration of the apparatus.

According to the method of manufacturing the heat transfer tube with internal groove of the present embodiment having the above-mentioned structure, the strip material T made of copper or copper alloy annealed after cold rolling is used,
In addition, the surface roughness of both surfaces S1 and S2 of the plate material T is 0.05 to
Since it is set to 0.30 μmRa, the elongation of the material is appropriately suppressed, the material can be prevented from excessively flowing in the direction parallel to the strip material T, and the material can easily enter the rolling groove 40. It is possible to form thin and high fins with a relatively small rolling pressure. Therefore, there is an excellent effect that an inner grooved heat transfer tube having excellent heat exchange performance can be manufactured at a low manufacturing cost. Further, since it is not necessary to increase the rolling pressure, there is an advantage that a wavy shape does not occur at both ends of the strip material T in the width direction.

In the above embodiment, the fins 2 and the spiral groove 3 are formed only on the inner surface of the heat transfer tube 1, but in the present invention, the fins and grooves are formed on the outer surface of the heat transfer tube, or on the inner surface and the outer surface. It is also applicable to. Further, in the above-described embodiment, the grooved roll 14 is used to perform one-step groove rolling, but two or more grooved rolls are used to form the groove in two or more steps so that two kinds of grooves are crossed. It is also possible to form the cross groove on the inner surface and / or the outer surface of the heat transfer tube, and in this case, the same effect as that described above can be obtained. Furthermore, according to the method of the present invention, not only is it possible to form spiral fins or spiral grooves extending over the entire width of the strip material, but also to divide short fins into a plurality of staggered or spiral lines. It is also possible to form a large number.

[0035]

EXAMPLES Next, the effects of the present invention will be demonstrated with reference to examples. [Experiment 1] Using an annealed sheet material made of deoxidized copper (C1220), an internal grooved heat transfer tube was manufactured by the apparatus shown in FIG. At that time, only the surface roughness is changed by changing the polishing conditions of the strip material, while all other conditions are unified, the rolling reduction force and rolling force required to obtain the fin shape described below are Whether a wavy shape occurs on the end surface of the plate material after fabrication, whether a welding defect occurs,
And it was confirmed whether or not the medium elongation occurred. The shape of the intended heat transfer tube with inner groove is as follows. Outer diameter: φ9.52 mm Thickness of metal pipe excluding fins: 0.32 mm Height of fin from inner peripheral surface of pipe: 0.28 mm Number of fins (number of threads) in pipe cross section: 60 Both sides of fin Angle (vertical angle): 20 ° Spiral angle (lead angle) with respect to the tube axis of the fin: 18 °

Other common conditions are as follows. Annealing condition: heating at 400 ° C. for 30 minutes Dimensions of sheet material: thickness 0.53 mm × width 33 mm Average grain size of sheet material: 0.015 to 0.020 mm Average hardness of sheet material: 52 to 57Hv Surface roughness of plate material T: 0.15 μmRa Outer peripheral surface roughness of grooved roll 14: 0.95 μmRa

The results are shown in Table 1. "Good or bad shape of plate edge"
Means the occurrence of a wavy shape, “x” indicates the occurrence of a remarkable wavy shape that makes welding difficult, and “△” indicates that a clear wavy shape has occurred, although welding can be performed. “◯” indicates that a slight wavy shape was generated, and “⊚” indicates that no wavy shape was observed. "Medium elongation" means the occurrence of slack in the central part of the strip material, "x" indicates the occurrence of medium elongation that makes welding difficult, and "△" indicates that welding is possible but clear. It shows that the middle elongation occurred, "○" indicates the occurrence of a slight middle elongation,
“⊚” indicates that medium elongation was not observed.
"Good or bad of the welded part" means the soundness of the welded part, and "x"
Indicates that a clear welding defect has occurred, and “△” indicates that a welding defect that does not affect airtightness has occurred.
"○" indicates that a slight appearance abnormality with practically no problem occurred, and "⊚" indicates that no abnormality in the welded portion was observed.

[0038]

[Table 1]

As is clear from Table 1, when the surface roughness of both surfaces of the plate material T is 0.05 to 0.30 μmRa, the roll rolling force required to obtain a thin and high fin shape is small, No wavy shape, welding defects, and medium elongation were observed.

[0040]

As described above, the method for producing an inner grooved heat transfer tube according to the present invention uses a strip material made of copper or copper alloy that has been annealed after cold rolling as a strip material, Moreover, since the surface roughness of the strip material is set to 0.05 to 0.30 μmRa, the elongation of the material is appropriately suppressed during rolling by the fin forming roll, and the material is spread in the direction parallel to the strip material. It is possible to prevent excessive flow, facilitate material entry into the rolling groove, and form thin and high fins with a relatively small rolling pressure. Therefore, it is possible to manufacture an inner grooved heat transfer tube having excellent heat exchange performance at a low manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a side view showing an apparatus used in an embodiment of a method for manufacturing a heat transfer tube with an inner groove according to the present invention.

FIG. 2 is a side view showing the periphery of a fin forming roll of the same device.

FIG. 3 is a front view showing the periphery of a fin forming roll of the same device.

FIG. 4 is a vertical cross-sectional view showing the periphery of a fin forming roll of the same device.

FIG. 5 is an enlarged cross-sectional view showing a fin rolled state by the fin forming roll of the same apparatus.

FIG. 6 is a cross-sectional view showing an example of an inner grooved heat transfer tube obtained by the method of the present invention.

FIG. 7 is an enlarged cross-sectional view showing a fin rolled state showing a problem of the conventional method.

[Explanation of symbols]

 1, P Heat transfer pipe 2 Fin 3 Spiral groove 4 Welded portion 5 Finless portion T Plate material S1, S2 Both sides of plate material 14 Grooved roll (fin forming roll) 16 Smooth roll (fin forming roll) 20 Forming roll 40 Rolling groove 42 Ridge section α Angle formed by both sides of rolling groove D Depth of rolling groove W Opening width of rolling groove

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Haruo Kono Inventor Haruo Kono 128-7 Ogimachi, Aizuwakamatsu, Fukushima Prefecture Wakamatsu Works, Mitsubishi Shindoh Co., Ltd.

Claims (4)

[Claims] 1. A fin for forming a fin on at least one surface of the strip material while passing a strip material made of copper or copper alloy annealed after cold rolling and passing through at least a pair of fin forming rolls. A forming step, a tube forming step of forming a plate material on which the fins are formed into a tubular shape through a plurality of forming rolls, and a welding step of heating both end edges of the tube material formed into a tubular shape and then abutting and welding the same. And a step of forming the fins with a surface roughness of 0.05 to 0.30 μmRa on both surfaces of the strip material, the manufacturing method of the inner grooved heat transfer tube. 2. The thickness of the plate material before fin formation is set to 0.
30 to 1.20 mm, the angle between both sides of each rolling groove of the fin forming roll is set to 10 to 40 °, and the depth of each rolling groove of the fin forming roll is set to the fin forming roll. The method for producing a heat transfer tube with an inner groove according to claim 1, wherein the thickness is set to 20 to 60% of the thickness of the preceding strip material. 3. The method for producing a heat transfer tube with an inner groove according to claim 1, wherein a deoxidized copper strip material is used as the strip material. 4. The method for producing a heat transfer tube with an inner surface groove according to claim 1, wherein the sheet material used in the fin forming step has a Vickers hardness of 50 to 150 Hv. .