JP2005066617A - Metal tube with outer spiral fin and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal tube with an outer spiral fin and its manufacturing method capable of obtaining a highly round-shaped metal tube with an outer spiral fin having a longer disk life because any slip is not generated on disks of a work roll. <P>SOLUTION: When spiral fins are formed on an outer surface of a worked tube by slantly arranging a plurality of work rolls having a plurality of disks at an axial direction around the axis of the worked tube, a fin height H and a fin width W, and fin volume Vf at an arbitrary length and the volume Vp of the metal tube are manufactured so as to satisfy the following inequalities (1) and (2), (1): 0.4≤Vf/Vp≤0.6, and (2): 2.5≤H/W≤3.5, respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a metal tube with an outer surface spiral fin used as a heat transfer tube for heat exchange, and a metal tube with an outer surface spiral fin manufactured by the manufacturing method. Manufacturing method of a metal tube with an outer surface spiral fin capable of producing a highly rounded product with a good fin shape and high roundness, and a metal tube with an outer surface spiral fin manufactured by the manufacturing method About.

  Metal pipes with outer spiral fins used as heat transfer tubes for heat exchangers, etc. Three processing rolls with a plurality of disks arranged in the axial length direction are arranged around the axis of the tube to be processed. It is manufactured by a rolling process in which 1 to 3 helical fins are formed on the outer surface of the pipe to be processed.

  Many proposals have been made for such rolling processes.

  Patent Document 1 proposes a method in which lubricating oil at a predetermined temperature is supplied between a work tube and a disk of a processing roll to improve the disk life.

  According to Patent Document 2, the height of the fin is 5 mm or more by making a tube having an inner diameter satisfying a certain relationship with the outer diameter and inner diameter of the tube including the fin after fin forming into a work tube. A method capable of forming an extremely high fin has been proposed.

  Patent Document 3 describes a method of reducing the fin height of two of the three fins by providing a crushing disk on two of the three processing rolls. Yes.

  However, the rolling process is less efficient than other cold workings, and when machining stainless steel, which is a difficult-to-work material, troubles due to slip between the work tube and the tool have occurred. If slip occurs between the work tube and the tool, the shape of the fin is disturbed, and predetermined processing cannot be performed. This causes a decrease in the yield rate and the operation efficiency, which is a serious problem.

  By the way, recently, as described in Patent Document 3, the formation of a triple fin is becoming mainstream. The reason is that the density of fins is the highest in the case of triple fins, and the heat transfer efficiency can be further increased.

  However, the formation of the triple fins increases the load on the disk of the processing roll, which not only makes the processing itself extremely difficult, but also shortens the life of the disk. For example, when manufacturing a metal tube with an outer surface spiral fin having the same pitch, if the ideal manufacturing can be performed without slipping, the processing speed of the pipe to be processed (advance speed in the pipe axis direction) v (mm / min) is given by the following equation (4).

ω = (D / d) · Ω (3)
v = k · p · ω = k · p · (D / d) · Ω (4)
Here, ω is the rotational speed (rpm) of the work tube, Ω is the rotational speed (rpm) of the disk, D is the outer diameter (mm) of the disk, d is the outer diameter (mm) of the work pipe, and k is the fin (1 to 3) and p is the fin pitch (mm).

  From equation (4), it can be seen that the traveling speed in the tube axis direction depends on the number of fins. Therefore, when the same processed pipe and disk are used, the processing speed of the processed pipe increases as the number of fins increases.

  On the other hand, when the machining speed is increased, the machining load applied to the disk is increased, so that the tool life is reduced and the production cannot be performed with high efficiency. In addition, slipping easily occurs between the work tube and the disk, and the roundness of the metal tube with the outer surface spiral fin and the shape of the fin are disturbed. These effects are particularly remarkable in the metal tube with the outer surface spiral fin having the three-row fin.

Japanese Patent Application Laid-Open No. 3-213395 Japanese Patent Laid-Open No. 9-94623 JP 2000-283678 A

  The present invention has been made in view of the above circumstances, and has a metal tube with an outer surface spiral fin that has excellent disk life of a work roll, does not slip during manufacturing, has high roundness, and has a good fin shape. An object of the present invention is to provide a method of manufacturing a metal tube with an outer surface spiral fin that can be efficiently manufactured, and a metal tube with an outer surface spiral fin manufactured by the manufacturing method.

  In producing a metal tube with an outer surface spiral fin having three-row fins, the present inventors first studied on suppressing slip that occurs between a processed tube and a disk. The slip was considered to be largely due to the friction between the tube to be processed and the disk, and various types of lubricating oil were used to reduce the frictional resistance between the two to produce a metal tube with an outer surface spiral fin. However, the slip did not change much with the type of lubricant.

Therefore, the processing roll is rotated at 300 rpm, a metal tube with an outer surface spiral fin is manufactured from a processed tube made of an outer diameter of 19.05 mm, a wall thickness of 1.90 mm, and a material of SUS410Ti under various conditions. The correlation between the presence and absence and the shape of the pipe being processed was investigated.
FIG. 1 is a diagram schematically showing the production of a metal tube with an outer surface spiral fin as viewed from the axial direction of the tube to be processed. The work tube 1 receives pressure from the disk 20 from three directions, and the bite 3 is generated at a portion located between the disks of the work tube. Here, paying attention to this biting, it was found that the biting rate indicating the size of biting depends on the presence or absence of slip. Reference numeral 4 in the figure denotes a plug.

Here, the biting rate is the maximum outer diameter and the minimum outer diameter at a specific cross section when the disk with the outer surface spiral fin being processed is taken out by stopping the rotation of the disk during processing and releasing the reduction. The value obtained by dividing the difference by the average outer diameter. The specific cross section refers to a cross section in which a disk having the maximum outer diameter is in contact.
Table 1 is a table showing the biting rate and the presence or absence of slip. As is apparent from Table 1, when the biting rate is 4% or less, it was found that slip does not occur.

  On the other hand, if the volume of the work roll disc that bites into the work tube from the outer surface increases during processing, the volume of the metal extruded by the disc also increases. The extruded metal moves toward the outer surface of the work tube. As a result, the work tube cannot maintain roundness and the biting rate increases. In other words, in order to reduce the biting rate and eliminate the slip, the volume that the disk bites into the work tube from the outer surface (the biting amount) may be reduced.

  For that purpose, it is conceivable to perform either one or both of reducing the amount of reduction of the disk onto the work tube and / or reducing the shape of the tip of the disk. In the former case, the height of the fins must be reduced, and the area of the outer surface is reduced, so that the heat exchange efficiency of the metal tube with the outer surface spiral fins is reduced. On the other hand, in the latter case, the disk life is shortened due to insufficient disk strength. Therefore, in order to control the amount of biting at the time of manufacture, it is necessary to control both in a balanced manner.

  FIG. 2 is a view schematically showing a part of a longitudinal section of a metal tube with an outer surface spiral fin after manufacture. In FIG. 2, H in FIG. 2B is the fin height, and W is the fin width. Further, Sf in FIG. 5A is the cross-sectional area of the fin, and Sp is the cross-sectional area of the pipe portion directly under the fin, and these cross-sectional areas are obtained by integrating with an arbitrary length of the metal pipe with the outer surface spiral fin. The volume becomes the volume Vf of the fin and the volume Vp of the pipe portion immediately below the fin.

  First, Vf / Vp is a volume ratio and does not reflect the shape of the fin, and hence the shape of the tip of the disk. When the same disk is used, increasing the amount of reduction increases the height of the fin, but does not change the width of the fin. For this reason, the larger the reduction amount, the larger the ratio H / W of the height and width of the fins.

  Further, when the amount of reduction is the same, the thinner the tip shape of the disk, the more the height of the fin does not change.

From the above, H / W depends on the amount of disk reduction and the shape of the tip of the disk.
On the other hand, the effect due to the difference in the thickness of the pipe portion directly under the fin cannot be evaluated only by evaluating using H / W.

  Therefore, attention was paid to the volume of the fin and the volume of the pipe portion directly below the fin. When the same disk is used, if the amount of reduction is increased, the volume of the fin portion increases, while the volume of the tube portion directly under the fin decreases. For this reason, the ratio Vf / Vp between the volume of the fin at an arbitrary length and the volume of the pipe portion immediately below the fin becomes a larger value as the amount of reduction is larger.

  Further, when the amount of reduction is the same, the volume of the fin portion increases as the tip shape of the disk is thinner. At this time, the volume of the tube portion directly under the fin does not greatly depend on the shape of the tip of the disk. For this reason, Vf / Vp becomes smaller as the tip shape of the disk is thinner.

  From the above, Vf / Vp also depends on the amount of disk reduction and the shape of the tip of the disk.

  Therefore, the present invention has been completed by focusing on H / W and Vf / Vp.

  The gist of the present invention is the following method for producing a metal tube with an outer surface spiral fin.

  A metal tube with an outer surface spiral fin for forming a spiral fin on the outer surface of the tube to be processed by inclining a plurality of processing rolls each having a plurality of disks arranged in the axial direction around the axis of the tube to be processed The fin height H and the fin width W, and the fin volume Vf and the volume Vp of the pipe part directly below the fin satisfy the following formulas (1) and (2): The manufacturing method of the metal tube with an outer surface spiral fin manufactured so that it may do.

0.4 ≦ Vf / Vp ≦ 0.6 (1)
2.5 ≦ H / W ≦ 3.5 (2)
At this time, it is preferable that the fin of the metal tube with an outer surface spiral fin is a triple fin.

  Moreover, the metal tube manufactured with the manufacturing method of the said metal tube with an outer surface spiral fin becomes as follows.

  Metal tube with an outer surface spiral fin in which fin height H and fin width W, and volume Vf of the fin at an arbitrary length and volume Vp of the tube portion immediately below the fin satisfy the following expressions (1) and (2): .

0.4 ≦ Vf / Vp ≦ 0.6 (1)
2.5 ≦ H / W ≦ 3.5 (2)
Also in this case, it is preferable that the fin of the metal tube with the outer surface spiral fin is a triple fin.

  According to the method of the present invention, since the life of the disc is prolonged even when the three-row fin is subjected to an excessive load, the manufacturing cost can be reduced. Further, it is possible to obtain a metal tube with an outer surface spiral fin which has no fin during manufacturing, has high roundness, and has a good shape.

  In the method of manufacturing a metal tube with an outer surface spiral fin according to the present invention, a plurality of processing rolls each having a plurality of discs arranged in the axial length direction are inclinedly arranged around the axis of the processing tube, and the outer surface of the processing tube. It is assumed that a spiral fin is formed on the substrate.

  FIG. 3 is a diagram schematically showing a case where a metal tube with an outer surface spiral fin is manufactured by a processing roll for forming fins on a tube to be processed, and FIG. 4 is a diagram when manufacturing a metal tube with an outer surface spiral fin. It is the figure which showed typically the process cross section of.

  As shown in FIG. 3, a plurality of processing rolls 2 are arranged with respect to the processing pipe 1. A plurality of discs 20 (see FIG. 4) are arranged in the axial direction in this processing roll, and are inclined around the axis of the tube to be processed. As shown in FIG. 4, the disk is gradually formed into grooves on the outer surface of the pipe to be processed, and finally the spiral fin 10 is formed. It becomes the pipe | tube 5 (refer FIG. 3).

  FIG. 5 is a development view (upper stage) of a metal tube with outer surface spiral fins having 1 to 3 fins and a disk arrangement (lower stage) of processing rolls for manufacturing the outer surface finned metal tube. FIG.

The number of fins can be changed by adjusting the position of the processing roll according to the pitch of the disk. For example, when a fin is formed by a processing apparatus having three processing rolls as shown in FIG. 3, a metal tube with an outer surface spiral fin having 1 to 3 fins can be manufactured. In order to manufacture the metal tube with the outer surface spiral fins having the above-mentioned fins, the processing rolls may be arranged so as to be shifted in the axial length direction of the tube to be processed so as to have a disk arrangement as shown in the lower part of FIG.
However, as the number of strips increases, the stress applied to the tube to be processed and the disk increases, so that the metal tube with the outer surface spiral fin having a larger number of strips is difficult to manufacture.

  In addition, as also shown below, the present invention was completed in consideration of a metal tube with an outer surface spiral fin having three-row fins that are difficult to manufacture, but the outer surface spiral having fewer than three wires The present invention is applicable even to a finned metal tube.

  In the method of manufacturing a metal tube with an outer surface spiral fin according to the present invention, the fin height H and the fin width W, and the fin volume Vf at an arbitrary length and the volume Vp of the tube portion immediately below the fin are expressed by the following formula (1): And (2).

0.4 ≦ Vf / Vp ≦ 0.6 (1)
2.5 ≦ H / W ≦ 3.5 (2)
Using processing rolls having disks of various shapes, metal tubes with outer surface spiral fins having three-row fins, which are considered to be particularly difficult to manufacture even with metal tubes with outer surface spiral fins, were manufactured. At this time, the processing roll was rotated at 300 rpm, and a metal tube with an outer surface spiral fin was manufactured from a metal tube having an outer diameter of 19.05 mm, a wall thickness of 1.90 mm, and a material SUS410Ti.

  Table 2 shows the disk shape of the processing roll. The meaning of each parameter in Table 2 is as shown in FIG. Further, as described above, since a plurality of disks are arranged on the processing roll, regarding D and T in Table 2, the minimum value (upstream side) and the maximum value (downstream side) are shown.

  Table 3 shows the ratio Vf / Vp between the fin volume Vf of the metal pipe with the outer surface spiral fin manufactured by the processing roll having the disk shape shown in Table 2 and the volume Vp of the pipe portion directly below the fin, and the fin height H. The ratio H / W with the fin width W is shown. In the case of using work rolls having disks having different shapes, the shapes are reflected, and metal tubes with outer surface spiral fins having different Vf / Vp and H / W are formed.

  Table 4 shows the biting rate, the presence / absence of slip, and the life of the disc when the metal pipe with the outer surface spiral fin is manufactured by the processing roll having the disc shape shown in Table 2. As described above, it can be seen from Table 4 that slip occurs when the biting rate exceeds 4%. Here, the disk life means the total length of the metal pipe with the outer surface spiral fin manufactured from the state in which the disk is not used and before the metal tube with the outer surface spiral fin is manufactured.

  First, Vf / Vp and H / W with a biting rate of 4% or less without slipping were summarized.

  FIG. 7 is a graph showing the dependency of the biting rate on Vf / Vp, and FIG. 8 is a graph showing the dependency of the biting rate on H / W.

  From FIG. 7 and FIG. 8, in order to keep the biting rate within 4% and prevent slippage during production, Vf / Vp is set to 0.4 or more and H / W is set to 3.5%. Must be: Preferably, Vf / Vp is 0.44 or more and H / W is 3.2% or less.

  On the other hand, when the metal tube with the outer surface spiral fin is manufactured under the condition that slip occurs during the manufacturing, the life of the disk of the processing roll is shortened. This is because when a slip occurs, the load applied to the disk is momentarily reduced by the slip and then a larger load is applied, whereas when the slip does not occur, a stable load is always applied to the disk. .

  Therefore, the relationship between the disk life and Vf / Vp and H / W is summarized.

  FIG. 9 is a graph showing the dependency of the disk life on Vf / Vp, and FIG. 10 is a graph showing the dependency of the disk life on H / W.

From FIG. 9 and FIG. 10, the disk life has an inflection point where Vf / Vp is 0.75 and H / W is 2.4. Vp must be 0.75 or less, and H / W must be 2.4 or more. Preferably, Vf / Vp is 0.6 or less and H / W is 2.8 or more.
From the above, in the method of manufacturing a metal tube with an outer surface spiral fin according to the present invention, the fin height H and the fin width W, and the fin volume Vf and the volume Vp of the tube portion immediately below the fin at an arbitrary length are as follows: It was assumed that the product was manufactured so as to satisfy the formulas (1) and (2).

0.4 ≦ Vf / Vp ≦ 0.6 (1)
2.5 ≦ H / W ≦ 3.5 (2)

  Three processing rolls with 38 discs arranged between 34 mm are installed in an inclined manner around the pass line, and a metal tube made of outer diameter 19.05 mm, wall thickness 1.90 mm, and material SUS410Ti is used as the work tube. A metal tube with an outer surface spiral fin having three fins was manufactured. At that time, a plug having an outer diameter of 13.36 mm was used, and the rotation speed of the processing roll was set to 300 rpm.

6 (b) has a cross-sectional shape shown on the right side, and has a shape in which the tip R is 0.30 mm, the taper angle α is 7.0 °, and the disk width T is 0.88 to 0.96 mm. The disc having was used.
In addition, the manufactured metal tube with an outer surface spiral fin has a fin density of 26 pieces of 3 fins per 25.4 mm (1 inch) in the tube axis direction, and an outer diameter including the fin portion is 19.05 mm, The outer diameter (valley diameter) excluding the fin portion was 14.88 mm, Vf / Vp was 0.44, and H / W was 2.94, which was within the scope of the present invention.

  At this time, the biting rate during manufacture was 3.1%, slip did not occur, and a metal tube with an outer surface spiral fin having high roundness was obtained. Further, the disk life was 780 m, and the disk life could be extended sufficiently.

  The same metal tube as that of Example 1 was used as a tube to be processed, and had a cross-sectional shape shown in FIG. 6 (b). Was used to manufacture a metal tube with an outer surface spiral fin having two-row fins using a disk having a shape of 0.88 to 0.96 mm. At that time, the outer diameter of the plug used and the rotational speed of the processing roll are the same as those in the first embodiment.

  The manufactured metal pipe with an outer surface spiral fin had Vf / Vp of 0.56 and H / W of 3.03, which was within the scope of the present invention.

  At this time, the biting rate during manufacture was 2.2%, slip did not occur, and a metal tube with an outer surface spiral fin having high roundness was obtained. Further, the disk life was 830 m, and the disk life could be extended sufficiently.

  The production method of the present invention can also be applied to the production of a metal tube with an outer surface spiral fin made of a non-ferrous metal such as aluminum or copper having good workability.

It is the figure which showed typically the place which looked at manufacture of the metal pipe with an outer surface spiral fin from the axial direction of the to-be-processed pipe. It is the figure which showed typically a part of longitudinal section of the metal tube with an outer surface spiral fin after manufacture. It is the figure which showed typically the place where the metal pipe with an outer surface spiral fin is manufactured with the process roll which shape | molds a fin in a to-be-processed pipe. It is the figure which showed typically the process cross section when manufacturing the metal tube with an outer surface spiral fin. FIG. 2 is a development view of an outer surface spiral finned metal tube having 1 to 3 fins (upper stage) and a diagram schematically showing a disk arrangement (lower stage) of processing rolls for manufacturing the outer surface spiral finned metal tube. is there. It is a figure for demonstrating the cross-sectional shape of the front-end | tip of a disk. It is the figure which showed the dependence of the biting rate with respect to Vf / Vp. It is the figure which showed the dependence of the biting rate with respect to H / W. It is the figure which showed the dependence of the disk lifetime with respect to Vf / Vp. It is the figure which showed the dependence of the disk lifetime with respect to H / W.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pipe to be processed 2 Processing roll 20 Disc 3 Biting 4 Plug 10 Fin 5 Metal pipe with outer surface spiral fin

Claims (4)

A metal tube with an outer surface spiral fin for forming a spiral fin on the outer surface of the tube to be processed by inclining a plurality of processing rolls each having a plurality of disks arranged in the axial direction around the axis of the tube to be processed The fin height H and the fin width W, and the fin volume Vf and the volume Vp of the pipe part directly below the fin satisfy the following formulas (1) and (2): The manufacturing method of the metal tube with an outer surface spiral fin manufactured so that it may do.
0.4 ≦ Vf / Vp ≦ 0.6 (1)
2.5 ≦ H / W ≦ 3.5 (2)   The method of manufacturing a metal tube with an outer surface spiral fin according to claim 1, wherein the fin of the metal tube with the outer surface spiral fin is a triple fin. Metal tube with an outer surface spiral fin in which fin height H and fin width W, and volume Vf of the fin at an arbitrary length and volume Vp of the tube portion immediately below the fin satisfy the following expressions (1) and (2): .
0.4 ≦ Vf / Vp ≦ 0.6 (1)
2.5 ≦ H / W ≦ 3.5 (2)   The metal tube with an outer surface spiral fin according to claim 3, wherein the fin of the metal tube with the outer surface spiral fin is a triple fin.

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