JP7404314B2 - Extruded tube with straight inner groove, inner spiral grooved tube and method for manufacturing heat exchanger - Google Patents

Description

TECHNICAL FIELD The present invention relates to an extruded raw tube with an inner straight groove, a tube with an inner spiral groove, and a method for manufacturing a heat exchanger.

As a method for manufacturing an inner spiral grooved tube, the manufacturing methods described in Patent Documents 1 and 2 below are known.
These manufacturing methods are suitable for manufacturing aluminum internally spiral grooved tubes, and use an aluminum internally linear grooved tube manufactured by extrusion as the base tube, and the diameter of this base tube is reduced using a drawing die. By applying twist at the same time, an internally spiral grooved tube can be manufactured. Since these manufacturing methods include a diameter reduction step using a drawing die, the straight grooved tube that is the raw tube needs to have a larger outer diameter than the inner spiral grooved tube that is the product obtained after processing.

By the way, since the inner spiral grooved tube is used as a heat transfer tube, it is desirable to make the inner diameter of the tube as large as possible in order to reduce the pressure loss caused to the refrigerant flowing inside. In order to increase the inner diameter of the pipe, it is desirable to reduce the bottom wall thickness if the outer diameter is the same.
By the way, when manufacturing a raw tube with a large D/t, where the outer diameter of the tube is D (mm) and the bottom wall thickness is t (mm), by extrusion processing, aluminum scum tends to adhere to the outer peripheral surface of the extruded raw tube. There is a problem.
Furthermore, even when the bottom wall thickness t of the internally spiral grooved tube is reduced, it is necessary to maintain the pressure generated by the refrigerant flowing inside, so it is necessary to increase the strength of the aluminum alloy used for the base tube.

When manufacturing internally spiral grooved pipes using the manufacturing methods described in Patent Documents 1 and 2, the raw pipe is obtained by extrusion processing, so the aluminum alloy used for the raw pipe is soft and has excellent extrudability at the extrusion stage. In addition, it is preferable that the final product, an internally spiral grooved tube, has high strength. JISA6000 series aluminum alloys, which are age hardening alloys, are considered to be applicable in obtaining such characteristics.

A technique described in Patent Document 3 is known as a technique for using JISA6000 series aluminum alloy for heat exchanger tubes, and Patent Document 3 states that it is recommended to use alloys such as JISA6005C and JISA6063 for heat exchanger tubes. has been done.

Patent No. 6169538 Patent No. 6439222 JP2008-267788A

However, when manufacturing internally spiral grooved tubes using the manufacturing methods described in Patent Documents 1 and 2, as mentioned above, the diameter reduction process using a drawing die is included, so the straight grooved tube that is the raw tube is It is necessary to make the outer diameter larger than the inner spiral grooved tube that is the resulting product.
Therefore, it is necessary to extrude the raw tube under conditions where D/t, where the outer diameter of the tube is D (mm) and the bottom wall thickness is t (mm), is extremely large. For this reason, even within the component ranges such as JISA6005C and JISA6063, aluminum sludge is likely to be generated during extrusion processing of the raw pipe, and there have been cases where it is necessary to reduce the extrusion speed to avoid generation of aluminum sludge.

Furthermore, when manufacturing an internally spirally grooved tube by rolling processing (internally grooved processing), there is no need for grooves on the inner surface of the extruded raw pipe, so extrusion of the raw pipe is easy.
However, when manufacturing an internally spiral grooved pipe using the manufacturing methods described in Patent Documents 1 and 2, it is necessary to form grooves on the inner surface of the extruded raw pipe in the process of manufacturing the raw pipe by extrusion.
The narrower the width W (mm) of the internal fins formed between the grooves on the inner surface of the extruded tube, the higher the height h (mm), the larger the heat transfer area, which improves the heat exchange performance of the heat transfer tube. can be increased.
Therefore, when manufacturing internally spiral grooved tubes for use as high-performance heat transfer tubes using the methods described in Patent Documents 1 and 2, during the extrusion process of the raw tube, the inner surface of the raw tube has a narrow width and a height. It is necessary to form high internal fins.

Therefore, under the condition that h/W is a certain value or more when the width of the internal fin formed on the inner surface of the raw pipe is W (mm) and the height is h (mm), even if the component range is JISA6005C or JISA6063. There is a problem that the aluminum alloy is insufficiently soft during extrusion processing of the raw pipe. In this case, there was a problem in that the aluminum alloy did not flow into the fins insufficiently during extrusion, and the desired dimensional accuracy could not be obtained in the fin shape on the inner surface of the raw tube obtained after extrusion.

The present invention allows the aluminum scum to be removed during extrusion even when extruding a raw tube under conditions where D/t is extremely large, where the tube outer diameter is D (mm) and the bottom wall thickness is t (mm). Even under conditions where the occurrence of internal fins can be suppressed and h/W, where the width of the internal fin formed on the inner surface of the raw tube is W (mm) and the height is h (mm), is above a certain level, the fins cannot be removed during extrusion. It is an object of the present invention to provide an extruded raw tube with an inner surface having linear grooves, in which the flow of aluminum alloy into the inner surface of the raw tube is sufficient, and desired dimensions can be obtained in the fin shape of the inner surface of the raw tube obtained after extrusion.
An object of the present invention is to provide an extruded base tube with internal straight grooves that has excellent extrusion manufacturability even when the bottom wall thickness is reduced and the heat transfer performance is good.
An object of the present invention is to provide an internally spiral grooved tube and a method for manufacturing a heat exchanger that have excellent manufacturability even when the bottom wall thickness is reduced and the heat transfer performance is good.

(1) The extruded raw pipe with inner straight grooves of this embodiment is an extruded raw pipe with inner straight grooves for manufacturing inner spiral grooved pipes, and the outer diameter of the extruded raw pipe with inner straight grooves is D (mm). , when the bottom wall thickness is t (mm), the width of the internal fin formed on the inner surface of the extruded pipe with inner linear grooves is W (mm), and the height is h (mm), h/W is 0. .7 or more, D/t is 26 or more, Si: 0.35 mass% or more and 0.55 mass% or less, Cu: 0.15 mass% or less, Mg: 0.45 mass% or more and 0.65 mass% The following contains Mn: 0.05% by mass or less, Mg ₂ Si: 0.71% by mass or more and 1.03% by mass or less, excess Si: 0.08% by mass or more and 0.29% by mass or less, and the remainder is unavoidable impurities. It is characterized by being constructed from an aluminum alloy consisting of aluminum and aluminum.

(2) In the extruded raw pipe with inner straight grooves of this embodiment, the aluminum alloy includes Si: 0.40 mass% or more and 0.55 mass% or less, Cu: 0.04 mass% or less, and Mg: 0.45 mass%. % or more and 0.60 mass% or less, Mn: 0.05 mass% or less, Mg ₂ Si: 0.71 mass% or more and 0.95 mass% or less, excess Si: 0.08 mass% or more and 0.25 mass% or less It is preferable that the aluminum alloy contains unavoidable impurities and the remainder consists of aluminum.

(3) The method for manufacturing the internal spiral grooved tube according to this embodiment includes Si: 0.35% by mass or more and 0.55% by mass or less, Cu: 0.15% by mass or less, Mg: 0.45% by mass or more and 0. .65 mass% or less, Mn: 0.05 mass% or less, Mg2Si: 0.71 mass% or more and 1.03 mass% or less, excess Si: 0.08 mass% or more and 0.29 mass% or less, and the remainder It is an extruded tube with an inner straight groove made of an aluminum alloy having a composition consisting of unavoidable impurities and aluminum, with an outer diameter of D (mm), a bottom wall thickness of t (mm), and an inner fin formed on the inner surface. When width is W (mm) and height is h (mm), the inner surface of an extruded pipe with internal straight grooves with h/W of 0.7 or more and D/t of 26 or more is twisted and drawn. This is a method for manufacturing a spirally grooved pipe, and is characterized in that an aging treatment is performed after the twist drawing process.

(4) The method for manufacturing the inner spiral grooved tube according to the present embodiment includes the aluminum alloy described in (3) : Si: 0.40 mass% or more and 0.55 mass% or less, Cu: 0.04 mass% or less. , Mg: 0.45% by mass or more and 0.60% by mass or less, Mn: 0.05% by mass or less, Mg ₂ Si: 0.71% by mass or more and 0.95% by mass or less, Excess Si: 0.08% by mass It is characterized by using an aluminum alloy containing 0.25% by mass or less, and the remainder consisting of unavoidable impurities and aluminum.

(5) The method for manufacturing the heat exchanger according to this embodiment includes Si: 0.35% by mass or more and 0.55% by mass or less, Cu: 0.15% by mass or less, Mg: 0.45% by mass or more and 0.65% by mass or less. % by mass or less, Mn: 0.05% by mass or less, Mg ₂ Si: 0.71% by mass or more and 1.03% by mass or less, excess Si: 0.08% by mass or more and 0.29% by mass or less, and the remainder It is an extruded tube with an inner straight groove made of an aluminum alloy having a composition consisting of unavoidable impurities and aluminum, with an outer diameter of D (mm), a bottom wall thickness of t (mm), and an inner fin formed on the inner surface. If the width is W (mm) and the height is h (mm), an extruded pipe with internal straight grooves with h/W of 0.7 or more and D/t of 26 or more is twisted and drawn. When manufacturing an internal spiral grooved tube and manufacturing a heat exchanger using this internal spiral grooved tube, the internal spiral grooved tube is removed after the twist drawing process and before the heat exchanger is completed. It is characterized by subjecting it to aging treatment.

(6) In the method for manufacturing a heat exchanger according to the present embodiment, the aluminum alloy includes Si: 0.40 mass% or more and 0.55 mass% or less, Cu: 0.04 mass% or less, and Mg: 0.45 mass%. % or more and 0.60 mass% or less, Mn: 0.05 mass% or less, Mg ₂ Si: 0.71 mass% or more and 0.95 mass% or less, excess Si: 0.08 mass% or more and 0.25 mass% or less It is preferable to use an aluminum alloy containing aluminum with the remainder being unavoidable impurities.

(7) In the method for manufacturing a heat exchanger according to the present embodiment, after forming a heat exchanger assembly by assembling the inner spiral grooved tube and the outer fin according to (5) or (6) , the inner spiral groove When manufacturing a heat exchanger by joining a tube and the external fin, the internal spiral grooved tube may be subjected to aging treatment after the twist drawing process and before combination with the external fin, or the internal spiral grooved tube may be aged. The present invention is characterized in that after the attached tube and the external fin are assembled and joined, an aging treatment is performed.
(8) In the method for manufacturing a heat exchanger according to the present embodiment, it is preferable that a zinc sprayed layer is formed on the outer surface of the extruded raw tube with inner straight grooves.

According to this embodiment, when extruding the raw pipe under conditions where D/t is extremely large, where the outer diameter of the raw pipe with internal straight grooves is D (mm) and the bottom wall thickness is t (mm), The extrusion process can also suppress the generation of aluminum scum during the extrusion process, and the extrusion process can be carried out under conditions where h/W, where the width of the internal fins formed on the inner surface of the raw tube is W and the height is h, is above a certain level. In this case, the aluminum alloy flows into the fin portions sufficiently, and it is possible to provide an extruded blank tube with internal straight grooves in which desired dimensional accuracy can be obtained in the internal fin shape of the inner surface of the extruded blank tube obtained after extrusion.

It is a figure which shows the extruded raw pipe with an inner surface linear groove of 1st Embodiment which equipped the inner surface with a linear groove, FIG.1(a) is a front view and FIG.1(b) is a longitudinal cross-sectional view. A partial enlarged cross-sectional view of the same extruded tube with straight grooves on the inner surface. FIG. 1 is a vertical cross-sectional view of the inner spiral grooved tube of the first embodiment. It is a figure which shows an example of the heat exchanger provided with the same internal spiral grooved tube, FIG.4(a) is a front view and FIG.4(b) is a perspective view. FIG. 3 is a flow diagram showing the first manufacturing process. FIG. 7 is a flow diagram showing the second manufacturing process. FIG. 7 is a flow diagram showing the third manufacturing process. FIG. 7 is a flow diagram showing a fourth manufacturing process. FIG. 7 is a flow diagram showing a fifth manufacturing process. FIG. 7 is a flow diagram showing a sixth manufacturing process.

Embodiments of the present invention will be described below with reference to the drawings.
Note that in the drawings used in the following explanation, characteristic parts may be enlarged and highlighted for convenience. Furthermore, for the same purpose, non-characteristic parts may be omitted from the illustrations.

1(a), (b) and FIG. 2 show an extruded raw tube with inner straight grooves according to the first embodiment of the present invention. A plurality of linear grooves 2 are formed along the length of the tube at predetermined intervals in the inner circumferential direction, and internal fins 3 are formed between adjacent linear grooves 2 in the inner circumferential direction of the tube.

The extruded raw pipe 1 with internal straight grooves includes Si: 0.35% by mass or more and 0.55% by mass or less, Cu: 0.15% by mass or less, Mg: 0.45% by mass or more and 0.65% by mass or less, Mn. : 0.05% by mass or less, Mg ₂ Si: 0.71% by mass or more and 1.03% by mass or less, excess Si: 0.08% by mass or more and 0.29% by mass or less, and the remainder is from inevitable impurities and aluminum. It is made of an aluminum alloy with the following composition.
The extruded raw tube 1 with internal straight grooves includes Si: 0.40% by mass or more and 0.55% by mass or less, Cu: 0.04% by mass or less, Mg: 0.45% by mass or more and 0.60% by mass or less, Mn. : 0.05% by mass or less, Mg ₂ Si: 0.71% by mass or more and 0.95% by mass or less, excess Si: 0.08% by mass or more and 0.25% by mass or less, and the remainder is from inevitable impurities and aluminum. It may be formed from an aluminum alloy having the following composition.
In addition to the above-mentioned composition, the extruded raw pipe 1 with internal straight grooves has a composition containing Fe in the range of 0.14 to 0.20% and Ti in the range of 0.01 to 0.05% (mass%). It may have.

The extruded raw tube 1 with inner linear grooves shown in FIGS. 1 and 2 consists of a tube body 5 having a circular outer shape in cross section. Note that, in order to make it easier to see the internal shape of the extruded raw tube 1 with inner linear grooves, FIG. 2 shows a state in which the circumferential wall of the extruded raw tube 1 with inner linear grooves is cut open and developed into a flat plate shape.
The outer diameter of the tube body 5 (the diameter of the circle drawn by the outer peripheral surface 5a of the tube body 5) is, for example, 3 mm or more and 15 mm or less. On the inner circumferential surface 5b of the tube body 5, there are 20 to 60 internal fins 3 formed linearly along the length direction of the tube body 5 at predetermined intervals in the inner circumferential direction of the tube body 5. Approximately 20 to 60 articles) are formed. Furthermore, a linear groove 2 having a predetermined width, for example, a constant width, is formed between the linear internal fins 3, 3 adjacent to each other in the inner circumferential direction of the tube body 5.

As shown in FIG. 2 in a developed view of the inside of the tube body 5, the internal fin 3 includes a tip portion (fin top portion) 3a located on the inside side of the tube body 5, a bottom portion 3b located on the outer circumferential side, and a tip portion 3b located on the outer peripheral side. The cross section is formed into an isosceles trapezoidal shape and includes a pair of side wall portions 3c located between a portion 3a and a bottom portion 3b.
The bottom portion 3b of the internal fin 3 is located at the inner peripheral portion of the tube body 5, and is continuous with the inner peripheral surface 5b, in other words, the bottom surface of the linear groove 2. The side wall portion 3c extends linearly toward the center of the tube body 5 in the cross section of the tube body 5 shown in FIG. In the cross section of the tube body 5, the wall thickness from the bottom surface of the linear groove 2 to the outer peripheral surface 5a of the tube body 5 can be expressed as a bottom wall thickness t.

The extruded raw pipe 1 with inner straight grooves has an outer diameter of D (mm), a bottom wall thickness of t (mm), and a width of the internal fins 3 formed on the inner surface of the extruded raw pipe with inner straight grooves. (mm) and the height is h (mm), preferably h/W is 0.7 or more and D/t is 26 or more. D/t is more preferably 30 or more.
Note that the width W of the internal fin 3 is different between the tip side and the bottom side, so the internal fin width (W) is the average of the tip width (internal fin top width: a) and the bottom width (b), and W = It is defined as (a+b)/2.
In the extruded raw tube 1 with internal straight grooves shown in FIG. It can be written as groove bottom width c.

In the structure shown in FIG. 2, the width of the tip 3a of the internal fin 3 and the width of the bottom 3b may be equal or substantially equal. In this case, the groove widths of the straight grooves 2 formed between the internal fins 3, 3 adjacent to each other in the circumferential direction of the tube body 5 are equal or approximately equal on the groove bottom side and the groove opening side.
In addition, in this embodiment, the cross-sectional shape of the internal fin 3 is not limited to the shape shown in FIG. The bottom portion 3b may have a rectangular shape with the same width.

Next, the constituent elements contained in the aluminum alloy constituting the extruded tube 1 with internal straight grooves will be explained. Note that this aluminum alloy is also the aluminum alloy that constitutes the internal spiral grooved tube 10, which is a twisted drawing tube to be described later.
"Si: 0.35% by mass or more and 0.55% by mass or less"
The Si content affects the extrusion processability of the extruded raw tube 1 with internal straight grooves and the pressure resistance of the internal spiral grooved tube, and if the Si content is less than 0.35% by mass, the When the compressive strength is insufficient and the Si content exceeds 0.55% by mass, the extrusion processability of the raw pipe deteriorates. Therefore, the Si content is preferably 0.35% by mass or more and 0.55% by mass or less. The Si content is more preferably 0.40% by mass or more and 0.55% by mass or less.

"Cu: 0.15% by mass or less"
The Cu content has an influence on the extrusion processability of the extruded raw pipe 1 with internal straight grooves, and when the Cu content exceeds 0.15% by mass, the extrusion processability of the raw pipe deteriorates. The Cu content is more preferably 0.04% by mass or less.
"Mg: 0.45 mass% or more and 0.65 mass% or less"
The Mg content affects the pressure strength and extrusion processability of the extruded raw pipe 1 with internal straight grooves, and if the Mg content is less than 0.45% by mass, the pressure strength of the internal spiral grooved pipe will be insufficient. When the Mg content exceeds 0.65% by mass, the extrusion processability of the raw tube deteriorates. Therefore, the Mg content is preferably 0.45% by mass or more and 0.65% by mass or less. The Mg content is more preferably 0.45% by mass or more and 0.60% by mass or less.

"Mn: 0.05% by mass or less"
The Mn content has an effect on the extrusion processability of the extruded raw pipe 1 with internal linear grooves, and when the Mn content exceeds 0.05% by mass, the extrusion processability of the extruded raw pipe 1 with internal linear grooves deteriorates. .
"Mg ₂ Si: 0.71 mass% or more and 1.03 mass% or less"
The Mg ₂ Si content affects the pressure strength and extrusion processability of the extruded raw tube 1 with internal straight grooves, and if the Mg ₂ Si content is less than 0.71% by mass, the pressure resistance strength of the internal spiral grooved tube will decrease. is insufficient and the Mg ₂ Si content exceeds 1.03% by mass, the extrusion processability of the extruded raw tube 1 with inner linear grooves deteriorates. Therefore, the Mg ₂ Si content is preferably 0.71% by mass or more and 1.03% by mass or less. The Mg ₂ Si content is more preferably 0.71% by mass or more and 0.95% by mass or less.
"Fe, Ti"
In addition to the above-mentioned component elements, the extruded raw tube 1 with internal straight grooves may contain Fe in the range of 0.14 to 0.20% and Ti in the range of 0.01 to 0.05% (mass%). .

"Excess Si: 0.08% by mass or more and 0.29% by mass or less"
Excess Si content affects the pressure resistance and surface roughness of the extruded raw tube 1 with inner linear grooves, and if the excess Si content is less than 0.08% by mass, If the compressive strength is insufficient and the excess Si content exceeds 0.29% by mass, the surface condition of the extruded tube 1 with internal straight grooves becomes noticeably rough, causing a problem of spoiling the appearance. Therefore, the excess Si content is preferably 0.08% by mass or more and 0.29% by mass or less. The excess Si content is more preferably 0.08% by mass or more and 0.25% by mass or less.

The amount of excess Si (mass %) contained in the above-mentioned aluminum alloy can be determined according to equation (1) shown below.
Excess Si amount=Si-(Mg/1.73)...Equation (1) In Equation (1), Si and Mg are the contents (mass %) of each element in the aluminum alloy. However, if the right side of equation (1) is a negative value, the excess Si amount is considered to be zero.

"Definition of Mg ₂ Si amount (mass%)"
The amount of Mg ₂ Si can be determined using the following equations (2) and (3) depending on the right side of equation (1).
When the right side of equation (1) is zero or a positive value: Mg ₂ Si amount = Mg + (Mg/1.73) ...(2) equation: When the right side of equation (1) is a negative value: Mg ₂ Si amount =Si+1.73×Si...Equation (3) In Equations (2) and (3), Si and Mg are the amounts (% by mass) of each element added in the aluminum alloy.

FIG. 3 shows an inner spiral grooved tube 10 which is a twisted drawn tube manufactured by twisting and drawing the extruded inner tube 1 with inner straight grooves having the configuration shown in FIGS. 1 and 2.
The inner spiral grooved tube 10 shown in FIG. 3 consists of a tube body 11 having a circular outer shape in cross section, and the outer diameter of the tube body 11 (the diameter of the circle drawn by the outer peripheral surface of the tube body 11) is, for example, 3 mm. 15 mm or less. On the inner circumferential surface of the tube body 11, there are 20 to 60 internal fins 12 formed spirally along the length direction of the tube body 11 at predetermined intervals in the inner circumferential direction of the tube body 11. Approximately 60 articles) have been established. Furthermore, a spiral groove 13 having a predetermined width, for example, a constant width, is formed between the spiral inner fins 12, 12 adjacent to each other in the inner circumferential direction of the tube body 11.

As shown in FIG. 3, in the inner spiral grooved tube 10, the spiral internal fins 12 and the spiral grooves 13 extend in the length direction of the tube body 11 at a constant twist angle θ1.
The torsion angle θ1 of each internal fin 12 or helical groove 13 is determined by the helical groove 13 or helical shape displayed at the center of the inner side of the tube when a vertical cross section of the inner spiral grooved tube 10 is drawn as shown in FIG. It shows the angle between the extension line of the linearly drawn portion of the internal fin 12 and the central axis of the tube body 11 (or a line parallel to the central axis). Note that the twist angle θ1 does not necessarily have to be constant, and may have a structure in which the twist angle varies periodically in the length direction of the inner spiral grooved tube 10.

The internal spiral grooved pipe 10 is different from the extruded base pipe 1 with internal linear grooves, as described in Patent Document 1 (Patent No. 6169538) or Patent Document 2 (Patent No. 6439222) described above. It is manufactured using a twist drawing process, which involves drawing and twisting at the same time.
Therefore, the cross-sectional shape of the internal fins 12 and the spiral grooves 13 formed in the internal spiral grooved tube 10 is the same as the cross-sectional shape of the internal fins 3 and the linear grooves 2 formed in the extruded inner tube 1 with linear grooves. They have similar shapes. However, the difference is that the internal fins 12 and the spiral groove 13 are spirally formed in the longitudinal direction of the tube.

The internal spiral grooved tube manufacturing apparatus shown in FIG. 1 of Patent Document 1 (Patent No. 6169538) or the internal spiral grooved tube shown in FIG. 1 of Patent Document 2 (Patent No. 6439222) By twisting and drawing the extruded raw tube 1 with straight inner grooves shown in FIGS. 1 and 2 attached to the present specification using a manufacturing apparatus, the inner spiral grooved tube 10 shown in FIG. 3 can be obtained. can.

The internal spiral grooved tube 10 is formed from an aluminum alloy having the composition described above. The internal spiral grooved tube 10 made of the above-mentioned aluminum alloy has improved pressure resistance by aging treatment, and the strength before the aging treatment is lower than after the aging treatment, so it is described in the above-mentioned Patent Documents 1 and 2. It is suitable for application to twist drawing processing using an internal spiral grooved tube manufacturing device.
The aging treatment can be carried out at a temperature range of 150° C. or higher and 250° C. or lower for 1 hour or more and 24 hours or less. More preferably, conditions can be selected in which the temperature is maintained in a temperature range of 180° C. to 220° C. for 1 hour to 8 hours. Details of manufacturing conditions such as aging treatment will be described later.

"Heat exchanger"
FIG. 4 is a schematic diagram showing an example of a heat exchanger 15 equipped with an internal spiral grooved tube 10, in which the internal spiral grooved tube 10 is provided in a meandering manner as a tube through which a refrigerant passes. It has a structure in which a plurality of plate-shaped external fins 16 made of aluminum alloy are arranged in parallel around the fin 10. The internal spiral grooved tube 10 is provided so as to pass through a plurality of through holes provided in external fins 16 arranged in parallel, as shown in FIG.
In the heat exchanger 15 shown in FIG. 4, the internal spiral grooved tube 10 includes a plurality of U-shaped main tubes 10A that linearly pass through the external fins 16, and adjacent end openings of the adjacent main tubes 10A are formed into a U-shape. The elbow pipes 10B are connected as shown in FIG. Furthermore, a refrigerant inlet 17 is formed at one end of the inner spiral grooved tube 10 penetrating the outer fin 16, and a refrigerant outlet 18 is formed at the other end of the inner spiral grooved tube 10. The heat exchanger 15 shown in FIG. 4 is constructed by forming the heat exchanger 15 shown in FIG.

Since a plurality of internal fins 12 and a spiral groove 13 are formed on the inner surface of the internal spiral grooved tube 10, the fin height (h'), The fin top width (a'), fin bottom width (b'), groove bottom width (c'), fin apex angle (θ'), and bottom wall thickness (t') can be determined.
If the bottom wall thickness (t') of the internally spiral grooved tube 10 is too thin, the pressure resistance will be insufficient, and if it is too thick, the pressure loss generated in the refrigerant flowing inside will increase. The bottom wall thickness (t') of the inner spiral grooved tube 10 is preferably 0.15 mm or more and 0.30 mm or less.
If the fin apex angle (θ') of the internal spiral grooved tube 10 is too small, the internal fin 12 will tend to fall down during the tube expansion process for joining with the external fin 16, and the distance between adjacent fin apexes 3a will be too small. The groove may become narrow and obstruct the flow of refrigerant into the spiral groove, resulting in a decrease in heat transfer performance. On the other hand, if the fin apex angle θ is too large, the spiral groove 13 formed between the internal fins 12 becomes narrower, resulting in a decrease in heat transfer performance, and the cross-sectional area inside the tube, which serves as a refrigerant flow path, becomes narrower. becomes smaller, and the pressure loss that occurs in the refrigerant flowing inside the tube increases. The fin apex angle (θ') of the inner spiral grooved tube 10 is preferably -5° or more and 30° or less, more preferably -5° or more and 22° or less, and even more preferably -5° or more and 10° or less.

If the fin top width (a') of the internal spiral grooved tube 10 is too small, it will be difficult for aluminum to flow into the fin portion during extrusion, making the shape of the internal fin 12 unstable; if it is too large, the internal fin 12 and the internal The spiral grooves 13 formed between the fins 12 become narrower, reducing heat transfer performance, and the cross-sectional area inside the tube, which serves as a flow path for the refrigerant, becomes smaller, increasing the pressure loss that occurs in the refrigerant flowing inside the tube. . The fin top width a' of the inner spiral grooved tube 10 is preferably 0.05 mm or more and 0.20 mm or less.

If the height (h') of the internal fins 12 of the internally spiral grooved tube 10 is too low, the surface area of the tube's inner surface will become small and the heat transfer performance will deteriorate; if it is too high, the internal fins 12 that become the refrigerant flow path will be cut off. As the area becomes smaller, the pressure loss that occurs in the refrigerant flowing inside the tube increases. The fin height (h') of the inner spiral grooved tube 10 is preferably 0.15 mm or more and 0.40 mm or less, more preferably 0.20 mm or more and 0.40 mm or less.
If the groove bottom width (c') of the inner spiral grooved tube 10 is too small, the amount of refrigerant that can be held in the spiral groove 13 will decrease, resulting in a decrease in heat transfer performance, and if it is too large, the surface area of the inner surface of the tube will decrease. Heat transfer performance decreases. The groove bottom width (c') of the inner spiral grooved tube 10 is preferably 0.10 mm or more and 0.30 mm or less, more preferably 0.25 mm or more and 0.30 mm or less.

If the torsion angle (θ') of the inner spiral grooved tube 10 is too small, the effect of disturbing the flow of refrigerant will be reduced, and the heat transfer performance will be reduced; if it is too large, the resistance to the flow of refrigerant will be large, and the inside of the tube will be damaged. The pressure loss that occurs in the flowing refrigerant increases. The twist angle (θ') of the inner spiral grooved tube 10 is preferably 10° or more and 45° or less, more preferably 10° or more and 24° or less.
When h'/W' is the fin height of the inner spiral grooved tube 10 and the fin width is (W'), if it is too small, the heat transfer performance will deteriorate, and if it is too large, the external fins will When expanding pipes for joining, the internal fins tend to collapse, increasing the pressure loss caused by the refrigerant flowing inside the pipes. h'/W', where the fin height of the inner spiral grooved tube 10 is (h') and the fin width is (W'), is preferably 0.8 or more and 2.5 or less, and 1.54 or more and 2.5 or less. The following are more preferred.

“Heat exchanger manufacturing method”
To manufacture the heat exchanger 15, first, an inner spiral grooved tube is hairpin-processed to form the main tube 10A. In addition, an elbow tube 10B is prepared by bending an aluminum alloy tube made of the same material as the inner spiral grooved tube. Alternatively, the elbow tube 10B may be formed by bending an inner spiral grooved tube.
Next, the main pipe 10A is provided so as to pass through the through holes formed in the plurality of external fins 16 arranged in parallel, and a pipe expansion plug is inserted into the main pipe 10A to expand the main pipe 10A. The mechanical joining force is ensured, and then the ends of the main pipe 10A are joined together with the elbow pipe 10B.
In addition, when manufacturing the heat exchanger 15, the connection between the main pipe 10A and the external fins 16 is not limited to the mechanical joining method using the tube expansion method, but other joining methods such as brazing may be used. Also good.

The extruded raw tube 1 with internal straight grooves according to the embodiment of the present application has specific amounts of Si, Cu, Mg, Mn, Mg ₂ Si, and excess Si as described above, so it is manufactured using the special procedure described below and twisted. After performing drawing processing and twist drawing processing, it is necessary to perform aging treatment.
Below, regarding the method of manufacturing a heat exchanger using the extruded raw tube 1 with internal straight grooves and the internal spiral grooved tube 10, from manufacturing the extruded raw tube 1 with internal straight grooves, including the process of aging treatment, The entire manufacturing method will be explained.

"Details of heat exchanger manufacturing method"
A billet is formed from a molten aluminum alloy by a semi-continuous casting method so as to have the above-mentioned predetermined composition. The resulting billet is subjected to homogenization treatment.
The homogenization treatment temperature is desirably set to 500°C or higher and 590°C or lower, more preferably 540°C or higher and 590°C or lower. The homogenization treatment time is desirably 2 hours or more and 20 hours or less.
After the homogenization treatment, the billet is forcibly cooled down to 100° C. or lower using a fan or the like.

Next, prior to extrusion, the billet accommodated in an extrusion device is heated, and the heating temperature is preferably 460° C. or higher and 560° C. or lower. More preferably, the temperature is 480°C or higher and 540°C or lower. The billet can be heated using an atmospheric furnace or an induction heating furnace.
Using a billet heated to a predetermined temperature, hot extrusion of an extruded raw pipe 1 with internal straight grooves is carried out.
After extrusion, the extruded raw pipe 1 with internal straight grooves is cooled to room temperature, subjected to zinc thermal spraying if necessary, and then wound into a coil on a drum.
The extruded raw pipe 1 with inner linear grooves wound around a drum in a coil shape is formed with inner spiral grooves by the method described in Patent Document 1 (Patent No. 6169538) or Patent Document 2 (Patent No. 6439222). It can be used for manufacturing attached pipes.

Next, solution treatment and aging treatment for obtaining the strength necessary for the inner spiral grooved tube 10 will be explained.
The temperature of the solution heat treatment is desirably 480°C or higher and 560°C or lower, more preferably 510°C or higher and 560°C or lower. The holding time at the solution treatment temperature is 1 minute or more and 8 hours or less, more preferably 1 minute or more and 1 hour or less.
Hardening is always required after the solution treatment time. Quenching is performed by forced air cooling using a fan in combination with water mist spraying as necessary, or by pouring cooling water over it, or by immersing it in cooling water, so that the cooling rate is 1°C/s or more. This can be done by

Note that heating of the billet during extrusion and solution treatment may also be performed. In that case, the temperature of the billet heating/solution treatment is 480° C. or higher and 540° C. or lower, and the holding time at the billet heating/solution treatment temperature is preferably 1 minute or more, the shorter the better. Considering productivity, the time is preferably 1 minute or more and 10 minutes or less, more preferably 1 minute or more and 5 minutes or less.
In addition, when heating the billet during extrusion and solution treatment simultaneously, quenching is performed at the press exit immediately after extrusion using a method such as forced air cooling using a fan so that the cooling rate is 1° C./s or more.
The aging treatment is performed at a temperature range of 150° C. or higher and 250° C. or lower for 1 hour or more and 24 hours or less. More preferably, the temperature range is 180° C. or higher and 220° C. or lower, and the temperature is maintained for 1 hour or more and 8 hours or less.

Solution treatment and aging treatment can be carried out at any timing between billet heating and completion of the heat exchanger having the configuration shown in Figure 4, as long as the aging treatment is a downstream process than the solution treatment. It can be carried out in
First to fourth manufacturing steps in which the timing of solution treatment and aging treatment are different will be described below.

FIG. 5 illustrates the first manufacturing process.
In the first manufacturing process shown in Figure 5, after billet casting and homogenization treatment, billet heating and solution treatment are performed during extrusion, quenching is performed by forced air cooling using a fan at the press exit immediately after extrusion, and twisting and drawing are performed. This can be carried out as a step of aging treatment after processing. The aged internally spiral grooved tube is cut to the required length and processed into a main tube and an elbow tube as shown in FIG. 4 by hairpin processing. Using these main pipes, elbow pipes, and external fins, assemble the main pipes into the through holes of the required number of external fins to form a heat exchanger shape, insert the pipe expansion plug into the main pipe, and connect the main pipes and external fins. A heat exchanger can be formed by mechanically joining and joining the ends of adjacent main pipes with an elbow pipe.

In the case of the first manufacturing process, there is no need for heat treatment after assembling the external fin, and if the external fin surface has a functional coating with excellent hydrophilicity or odor resistance, there is a risk that those functions will deteriorate due to heating. It is preferable that there is no such thing. On the other hand, it is necessary to perform hairpin processing and tube expansion processing on inner spiral grooved pipes that have been hardened by aging treatment, and care must be taken that problems such as pipe cracking and internal fin collapse are likely to occur during these processes. .

FIG. 6 illustrates the second manufacturing process.
In the second manufacturing process shown in FIG. 6, after billet casting and homogenization treatment, billet heating and solution treatment during extrusion are performed simultaneously, and quenching is performed by forced air cooling using a fan at the press exit immediately after extrusion. After this, aging treatment can be performed after the heat exchanger assembly process in which twist drawing is performed, cutting and hairpin processing are performed after twist drawing, and the internal spiral grooved tube is inserted into the through hole of the external fin and then expanded. . The details of the heat exchanger assembly process are the same as those for assembly by expanding the tubes, using the main pipe, elbow pipe, and external fins as described above.

In the case of the second manufacturing process, hairpin processing and tube expansion processing are performed before the internal spiral grooved tube hardens through aging treatment, so problems such as tube cracking and internal fin collapse are relatively unlikely to occur during these forming processes. It is preferable.
On the other hand, in this procedure, aging treatment is performed after the external fin is assembled. For this reason, the external fins are also heated at the same time during aging treatment, and if the external fins have functional coatings with excellent hydrophilicity or odor resistance on their surfaces, it is important to be aware that heating may deteriorate their functions. Become.

FIG. 7 illustrates the third manufacturing process.
In the third manufacturing step shown in FIG. 7, it is preferable that after billet casting and homogenization treatment, the billet is heated during extrusion, and immediately after extrusion, it is allowed to cool to room temperature in the atmosphere. Note that quenching may be performed by forced air cooling using a fan at the extrusion outlet.
After this, the heat exchanger assembly process involves twist drawing, annealing after twist drawing, cutting and hairpin processing, and then inserting the internal spiral grooved tube into the through hole of the external fin and expanding the tube. Aging treatment can be performed later. The details of the heat exchanger assembly process are the same as those for assembly by expanding the tubes, using the main pipe, elbow pipe, and external fins as described above.

In the third manufacturing process, the extruded tube with straight inner grooves is twisted and drawn, and then annealed to give the tube with inner spiral grooves an O temper. Thereafter, cutting and hairpin processing are performed, followed by a heat exchanger assembly process in which the internal spiral grooved tube is inserted into the through hole of the external fin and then expanded, followed by solution treatment and aging treatment.
Here, the annealing can be carried out under any conditions within the range that the internal spiral grooved tube becomes O tempered, but in the case of batch processing, an atmospheric furnace is used and the annealing is held at 330 to 380°C for 1 to 8 hours. Conditions can be selected. In this case, hairpin processing and tube expansion processing are performed in the annealed O-refined state, which is preferable in that problems such as cracking and internal fin collapse are less likely to occur during these forming operations.

Moreover, since a long time is not required between the solution treatment and the aging treatment, the strength after the aging treatment is likely to be stable, which can also be mentioned as a preferable point of this third manufacturing process.
On the other hand, in the third manufacturing process, since solution treatment and aging treatment are performed after the external fin is assembled, the external fin is also heated at the same time during the solution treatment and aging treatment, and the external fin surface has hydrophilic properties, odor resistance, etc. If the material has a functional coating with excellent properties, care must be taken that heating may deteriorate its functionality.

FIG. 8 illustrates the fourth manufacturing process.
In the fourth manufacturing step shown in FIG. 8, it is preferable that after billet casting and homogenization treatment, the billet is heated during extrusion, and immediately after extrusion, it is allowed to cool to room temperature in the atmosphere. Note that quenching may be performed by forced air cooling using a fan at the extrusion outlet.
Thereafter, the surface of the extruded raw pipe with straight inner grooves after extrusion is subjected to zinc spraying, and then twisted drawing processing is performed. Thereafter, a zinc diffusion heat treatment that also serves as a solution treatment is performed, and after the zinc diffusion heat treatment that also serves as a solution treatment, quenching is performed by a method such as forced air cooling using a fan.

After this, aging treatment can be continued. Here, the zinc diffusion heat treatment, which also serves as solution treatment, is performed at a temperature of 480°C or higher and 560°C or lower for 30 minutes or more and 8 hours, more preferably at a temperature of 480°C or higher and 520°C or lower for 30 minutes or more and 8 hours. It can be selected to provide the required zinc diffusion depth in the thickness direction of the grooved tube.
After the aging treatment, a heat exchanger assembly process can be performed in which the internal spiral grooved tube is inserted into the through hole of the external fin and then expanded. The details of the heat exchanger assembly process are the same as those for assembly by expanding the tubes, using the main pipe, elbow pipe, and external fins as described above.

In this case, since a zinc sprayed layer is formed on the outer surface of the internally spiral grooved tube, it is preferable in that it has excellent corrosion resistance when used as a heat exchanger for a long period of time after being assembled into a heat exchanger. Furthermore, no heat treatment is required after assembling the external fins. In addition, when the external fin surface has a functional coating having excellent hydrophilicity and odor resistance, there is no risk of deterioration of those functions due to heating, which is also a preferable point of the fourth manufacturing process.
On the other hand, it is necessary to perform hairpin processing and tube expansion processing on inner spiral grooved tubes that have been hardened by aging treatment, and care must be taken that problems such as pipe cracking and internal fin collapse are likely to occur during these processes. .

FIG. 9 illustrates the fifth manufacturing process.
In the fifth manufacturing process shown in FIG. 9, after billet casting and homogenization treatment, the billet is heated during extrusion, and after extrusion, zinc spraying is applied to the surface of the extruded raw tube, and then twist drawing is performed.
Thereafter, a zinc diffusion heat treatment that also serves as a solution treatment is performed, and after the zinc diffusion heat treatment that also serves as a solution treatment, quenching is performed by a method such as forced air cooling using a fan.
After that, cutting and hairpin processing are performed, followed by a heat exchanger assembly process in which the internal spiral grooved tube is inserted into the through hole of the external fin and then expanded, and then an aging treatment can be performed. The details of the heat exchanger assembly process are the same as those for assembly by expanding the tubes, using the main pipe, elbow pipe, and external fins as described above.

In the case of the fifth manufacturing process, a zinc sprayed layer is formed on the outer surface of the inner spiral grooved tube, so it has excellent corrosion resistance when used as a heat exchanger for a long time after being assembled into a heat exchanger. preferable. Another advantage is that hairpin processing and tube expansion are performed before the internal spiral grooved tube hardens through aging treatment, so problems such as tube cracking and external fin collapse are relatively unlikely to occur during these forming processes. Can be done.
On the other hand, in the fifth manufacturing process, since the aging treatment is performed after the external fin is assembled, the fin is also heated at the same time, and when the external fin surface has a functional coating with excellent hydrophilicity and odor resistance, etc. It should be noted that these functions may deteriorate due to heating.

FIG. 10 illustrates the sixth manufacturing process.
In the sixth manufacturing process shown in FIG. 10, after billet casting and homogenization treatment, the billet is heated during extrusion, and after extrusion, zinc spraying is applied to the surface of the extruded raw pipe. After this, after performing twist drawing processing, zinc diffusion heat treatment is performed, and then cutting and hairpin processing are performed.
Subsequently, a heat exchanger assembly step is performed in which the internal spiral grooved tube is inserted into the through hole of the external fin and then expanded, and then a solution treatment and an aging treatment can be performed. The details of the heat exchanger assembly process are the same as those for assembly by expanding the tubes, using the main pipe, elbow pipe, and external fins as described above.

In the case of the sixth manufacturing process, a zinc sprayed layer is formed on the outer surface of the inner spiral grooved tube, so it has excellent corrosion resistance when used as a heat exchanger for a long period of time after being assembled into a heat exchanger. preferable. In addition, since the spiral grooved tube becomes O tempered by zinc diffusion heat treatment, hairpin processing and tube expansion processing can be performed in the O tempered state, which may cause problems such as tube cracking and external fin collapse during forming. This is preferable because it is difficult to use.
Furthermore, since a long time is not required between the solution treatment and the aging treatment, the strength after the aging treatment is likely to be stable, which can also be mentioned as a preferable point of the sixth manufacturing step.
On the other hand, in the sixth manufacturing process, since solution treatment and aging treatment are performed after the external fin is assembled, the external fin is also heated at the same time during the solution treatment and aging treatment, and the external fin surface has properties such as hydrophilicity and odor resistance. If the material has a functional coating with excellent properties, it should be noted that heating may deteriorate its functionality.

In addition, as mentioned above, solution treatment and aging treatment may be performed even if they are not shown in the first to sixth manufacturing steps, as long as the aging treatment is a downstream process than the solution treatment. , can be carried out at any timing between heating the billet and completing the heat exchanger.
Depending on the timing of the solution treatment and quenching, it is also possible to select the case where the heat treatment is performed while the extruded tube with straight inner grooves or the spiral grooved inner tube is wound around a drum in a coiled state.
In this case, it must be noted that in an extruded tube with a linear groove on the inner surface or a tube with a spiral groove on the inner surface, the heating rate and the cooling rate tend to vary. In particular, in the case of quenching following solution treatment, it is necessary to keep in mind that the cooling rate of the inside of the coil is slower than that of the outside. The entire tube may be cooled at a cooling rate of 1° C./s or more.

In the case of the extruded raw tube 1 with internal straight grooves, if D/t is large or if the amount of excess Si contained in the aluminum alloy is large, aluminum deposits are likely to be formed at the exit of the extrusion die during extrusion.
For this reason, aluminum deposits are likely to peel off from the mold during extrusion and adhere to the outer surface of the extruded product, resulting in so-called "aluminum scum."
In the manufacturing process described above, since the extruded raw tube 1 with internal straight grooves was formed from an aluminum alloy with a specified composition of Si, Cu, Mg, Mn, Mg ₂ Si, and excess Si as described above, h/W was Even if the extruded raw tube 1 with internal straight grooves has a D/t of 0.7 or more and D/t is 26 or more, it can be extruded without producing aluminum scum, and the extruded raw tube 1 with internal straight grooves that does not have poor appearance can be manufactured. .
Moreover, since the internal spiral grooved tube 10 is manufactured by performing aging treatment after the twist drawing process, the internal spiral grooved tube 10 can be manufactured without causing breakage or breakage of the tube during the twist drawing process.

Furthermore, since the inner spiral grooved tube 10 is formed from an aluminum alloy with a specified composition of Si, Cu, Mg, Mn, Mg ₂ Si, and excess Si as described above, when a heat exchanger is constructed, pressure resistance performance is improved. It is possible to provide a heat exchanger that has excellent properties and is free from concerns about refrigerant leakage even when subjected to pressure from refrigerant.
As described above, the inner spiral grooved tube 10 is made of an aluminum alloy with a specified composition of Si, Cu, Mg, Mn, Mg ₂ Si, and excess Si, so it is a heat exchanger with excellent surface condition and no appearance defects. can be provided.

An extrusion billet with a diameter of approximately 200 mm was produced by semi-continuous casting so as to have the alloy components shown in Table 1. As components other than the alloy components shown in Table 1, all alloys contained Fe in a range of 0.14 to 0.20% and Ti in a range of 0.01 to 0.05% (mass%).

The produced billet for extrusion was subjected to a homogenization treatment at 560°C for 6 hours, and then air-cooled with a fan to 100°C or lower.
The billet for extrusion after the homogenization treatment was heated to 510° C. in an induction heating furnace to heat the billet for hot extrusion and also as a solution treatment.
The extrusion billet that reached 510°C was transferred to a hot extruder, hot extruded, and the number of fins (number of internal fins), outer diameter, bottom wall thickness, fin apex angle, and fin top shown in Table 2 was obtained. An extruded raw tube with inner straight grooves having width, fin height, D/t, and h/W was produced.

The holding time after the extrusion billet reached 510°C was about 2 minutes. Immediately after extrusion, the extruded blank tube with inner straight grooves having the shape shown in Table 2 obtained from the die was water-cooled to 100° C. or lower at a cooling rate of 1° C./s or higher.
The obtained extruded tube with straight inner grooves was twisted and drawn twice by a method using a twist-drawing device described in Patent No. 6439222, and the inner fin shape (outer diameter, bottom wall) was changed as shown in Table 2. It was processed into an internal spiral grooved tube with different thickness, fin apex angle, fin apex width, and fin height). Note that the twist drawing device described in Patent No. 6439222 is equipped with a first drawing die and a second drawing die that perform twist drawing processing, so that the twist drawing device substantially twists and draws the extruded raw pipe 1 with internal straight grooves. An internally spiral grooved tube is produced by passing it through the device once.
After the twist drawing process, the inner spiral grooved tube was subjected to aging treatment at 195°C for 2 and a half hours.
When the heat transfer performance was compared for the shapes of the inner spiral grooved tubes shown in Table 2, the heat transfer characteristics of the inner spiral grooved tubes of φ5-0.20t and φ4-0.18t were particularly excellent. Next, the φ7-0.25t and φ5-0.25t internal spiral grooved tubes had excellent heat transfer performance, but the φ7-0.30t internal spiral grooved tube also satisfied a certain level of heat transfer performance.

"Appearance (aluminum cast) evaluation method and evaluation criteria"
(Detailed explanation of aluminum cassette)
In an extruded tube with a straight groove on the inside, if the outer diameter is D (mm) and the bottom wall thickness is t (mm), if D/t is large or if the amount of excess Si contained in the aluminum alloy is large, during extrusion Aluminum deposits tend to form at the exit of the extrusion mold. For this reason, aluminum deposits are likely to peel off from the mold during extrusion and adhere to the outer surface of the extruded product, resulting in so-called "aluminum scum."
The individual size of the "aluminum scum" attached to the outer surface of the extruded product is approximately 0.1 mm in diameter, but since the gloss of the extruded product surface and the aluminum scum surface are different, the aluminum scum stands out visually and is considered to be a defective appearance. This may become a problem.

In addition, if aluminum scum is generated, the aluminum scum is pushed from the outer surface of the extruded raw tube with internal straight grooves toward the radial inside of the pipe cross section during the twist drawing process that follows the extrusion process, so that Compressive stress in the circumferential direction of the tube caused by the diameter reduction of the tube may cause buckling of the tube.
Furthermore, even if buckling of the raw pipe does not occur during twist drawing, in the obtained twist drawing product, the portion where the aluminum scum is pushed becomes the starting point of stress concentration, which may result in a decrease in pressure resistance.
Due to the above circumstances, it is necessary to suppress the generation of aluminum scum, and it is necessary to reduce the extrusion speed in order to avoid the generation of aluminum scum.

(Investigation of aluminum scum adhesion)
Hot extrusion was performed at an extrusion speed of 45 m/min, and the state of adhesion of aluminum scum to the outer surface of the obtained extruded tube was investigated.
Aluminum scum is aluminum deposits attached near the exit of an extrusion die, peeled off from the die, and attached to the outer surface of the extruded product. Although the size of each deposit is minute, approximately 0.1 mm in diameter, it can be sufficiently detected visually because the gloss is different from the surface of the extruded product.
An extruded raw pipe with a length of 1 m was taken, and the state of adhesion of aluminum sludge on the entire outer surface was visually confirmed.
The evaluation criteria for the state of aluminum scum adhesion were as follows: 3 or more aluminum scum adhered per 1 m of extruded raw tube was evaluated as ×, 1 or more but less than 3 was evaluated as △, and 0 was evaluated as ○.

"Extrudability evaluation method and evaluation criteria"
Extrusion processing was performed at an extrusion speed of 45 m/min, and the shape of internal fins formed on the inner surface of the obtained extruded raw tube was measured to evaluate extrudability.
A method for measuring the shape of internal fins will be explained. The extruded raw tube was cut at a cross section perpendicular to the extrusion direction so that the length in the extrusion direction was about 20 mm, to obtain a small piece of the extruded raw tube for internal fin shape measurement. The entire tube inner and outer surfaces of the small piece were embedded in an epoxy resin that cures at room temperature, and was left to cure at room temperature. A cross section of the small piece embedded in the cured epoxy resin perpendicular to the extrusion direction was polished together with the epoxy resin using emery polishing paper. The polishing was finished using emery abrasive paper #1000.

After final polishing, a cross section of the extruded raw tube perpendicular to the extrusion direction was imaged using a digital microscope manufactured by Keyence Corporation, and the width of the tip of the internal fin formed on the inner surface of the extruded raw tube was measured. If the aluminum alloy has poor extrudability, the flow of aluminum into the fin portion during extrusion processing of the raw tube will be insufficient, and the problem of narrowing the width of the internal fin will likely occur. If the measured internal fin tip width is 70% or less of the design value, extrudability ×, if it exceeds 70% and 85% or less, extrudability △, if it exceeds 85% was evaluated as extrudability.

"Torsion workability evaluation method and evaluation criteria"
The obtained extruded raw tube was drawn and twisted twice by a method using a twisting and drawing device described in Patent No. 6439222, and was processed into an inner spiral grooved tube having the shape shown in Table 2. .
At that time, at the stage when the extruded raw tube is wrapped around the second guide capstan provided at the rear stage of the second drawing die that performs the second drawing, the extruded raw tube cannot withstand the processing load and breaks. There was a case.
Wrapping the tube material around the second guide capstan is necessary to apply tension for stable torsional pultrusion, so we wrapped the extruded raw tube around the second guide capstan. If the extruded raw pipe broke at any stage, the twisting workability was evaluated as poor.
On the other hand, when it was possible to wrap the extruded raw tube around the second guide capstan without causing breakage of the extruded raw tube, the torsion workability was evaluated as 0.

"Pressure resistance"
After the aging treatment, the inner spiral grooved tube was subjected to a pressure test.
The internal spiral grooved tube was cut so that the axial length of the internal spiral grooved tube was approximately 150 mm, and sockets were attached to both ends. The socket at one end was connected to a water pressure pump via a pressure gauge. Water was sent into the inner spiral grooved tube from a water pressure pump, and the other socket was sealed with a plug while the inside of the inner spiral grooved tube was filled with water up to the opposite end of the tube.
Thereafter, the water pressure pump was operated to increase the water pressure in the inner spiral grooved pipe at a pressure increase rate of approximately 0.5 MPa/s. At that time, the limit water pressure at which the inner spiral grooved tube could not withstand the water pressure inside the tube and burst was measured as the "pressure resistance value" of the inner spiral grooved tube. The pressure resistance performance of the inner spiral grooved pipe was evaluated by marking the pressure resistance value 15 MPa or more as ○ and the case less than 15 MPa as ×.
The above evaluation results are summarized in Table 3.

As shown in Table 1 above, the aluminum alloys of Examples 1 to 16 contained Si: 0.35% by mass or more and 0.55% by mass or less, Cu: 0.15% by mass or less, and Mg: 0.45% by mass. 0.65 mass% or less, Mn: 0.05 mass% or less, Mg ₂ Si: 0.71 mass% or more and 1.03 mass% or less, excess Si: 0.08 mass% or more and 0.29 mass% or less. It is an aluminum alloy consisting of aluminum and unavoidable impurities.
Using the aluminum alloys described in Examples 1 to 16, extruded blank pipes with internal straight grooves having the shapes shown in Table 2 were extruded, and twisted and drawn twice by a method using a twisting and drawing device described in Patent No. 6439222. By applying the processing, it was possible to manufacture an internally spiral grooved tube having the shape shown in Table 2.
When an extruded raw tube with an inner straight groove is produced using the aluminum alloy described in Examples 1 to 16, and an inner spiral grooved tube is manufactured using this extruded raw tube with an inner straight groove, the extrudability is good. It was possible to manufacture an inner spiral grooved tube with excellent twisting workability, good evaluation in pressure resistance tests when the bottom wall thickness t was 0.3 mm or less, and good surface condition.

As shown in Table 1, Comparative Example 1 is a sample (outer diameter 7 mm) in which the content of Si, Mg, and Mg ₂ Si is outside the above range, and Comparative Examples 2 and 3 are samples in which the content of Si, Mg, and Mg ₂ Si is outside the above range. The pressure resistance of the samples (outer diameter 7 mm) was lower than the above range, but as shown in Table 3, the pressure resistance performance decreased.
Comparative Examples 4 and 5 were samples (outer diameter 7 mm) in which the content of Si and Mg ₂ Si was greater than the above-mentioned range, but the surface condition of both samples deteriorated.
Comparative Examples 6 and 7 are samples (outer diameter 7 mm) in which the content of Cu, Mg, Mn, and Mg ₂ Si is higher than the above range, but there is a problem that the width of the internal fin becomes thinner during extrusion processing. It broke during twist drawing.

Comparative Example 8 is a sample (outer diameter 5 mm) in which the content of Si, Mg, and Mg ₂ Si is outside the above range, and Comparative Example 9 is a sample (outside diameter) in which the content of Si and excess Si is lower than the above range. (diameter: 5 mm), but the pressure resistance performance decreased in both cases.
Comparative Example 10 was a sample (outer diameter 5 mm) in which the content of Si and excess Si was greater than the above range, but the surface condition deteriorated.
Comparative Example 11 is a sample (outer diameter 5 mm) in which the content of Si, Cu, Mg, Mn, and Mg ₂ Si is greater than the above range, but there is a problem that the width of the internal fin becomes narrow during extrusion processing. It broke during twist drawing.

Comparative Example 12 was a sample (outer diameter 5 mm) in which the contents of Si, Mg, Mg ₂ Si, and excess Si were lower than the above ranges, but the pressure resistance performance was lowered.
Comparative Example 13 is a sample (outer diameter 4 mm) in which the content of Si, Mg, and Mg ₂ Si is lower than the above range, and Comparative Example 14 is a sample (outside diameter) in which the content of Si and excess Si is lower than the above range. (diameter: 4 mm), but the pressure resistance performance decreased in both cases.
Comparative Example 15 is a sample (outer diameter 4 mm) in which the content of Si, Cu, Mg, Mn, and Mg ₂ Si is higher than the above range, but there is a problem that the width of the internal fin becomes narrow during extrusion processing. It broke during twist drawing.

Examples 1 and 3 are samples within the above-mentioned Si content range, but they are samples with a low Si content, and when the bottom wall thickness is 0.3 mm, pressure resistance can be ensured, but the bottom wall thickness is When it was set to 0.25 mm, the pressure resistance decreased as shown in Table 3. From this, it can be seen that the Si content is more preferably 0.40% by mass or more and 0.55% by mass or less.

Example 9 had the above-mentioned Cu content range, Mg content range, and Mg ₂ Si content range, but the extrudability was slightly decreased. Furthermore, in Examples 2 and 8, the extrudability did not decrease.
Further, a similar tendency is observed in Examples 11, 12, 15, and 16. Furthermore, from the comparison of Examples 2, 8, 9, 11, 12, 15, and 16, it was found that the Cu content was 0.04% by mass or less, the Mg content was 0.45% by mass or more and 0.60% by mass or less, Mg ₂ Si It is considered that an aluminum alloy having a content of 0.71% by mass or more and 0.95% by mass or less is more preferable.

DESCRIPTION OF SYMBOLS 1... Extruded raw pipe with inner straight groove, 2... Straight groove, 3... Internal fin, 5... Pipe body, 5a... Outer circumferential surface, 5b... Inner circumferential surface, 10... Inner spiral grooved tube, 10A... Main pipe, 10B... Elbow pipe, 11... Pipe body, 12... Internal fin, 13... Spiral groove, 15... Heat exchanger, 16... External fin.

Claims (8)

An extruded raw tube with an inner straight groove for manufacturing a tube with an inner spiral groove,
The outer diameter of the extruded raw pipe with inner straight grooves is D (mm), the bottom wall thickness is t (mm), and the width of the internal fin formed on the inner surface of the extruded raw pipe with inner straight grooves is W (mm). , the height is h (mm),
h/W is 0.7 or more, D/t is 26 or more,
Si: 0.35% by mass or more and 0.55% by mass or less,
Cu: 0.15% by mass or less,
Mg: 0.45% by mass or more and 0.65% by mass or less,
Mn: 0.05% by mass or less,
Mg ₂ Si: 0.71% by mass or more and 1.03% by mass or less,
1. An extruded raw tube with straight inner grooves, characterized in that it is made of an aluminum alloy containing excess Si: 0.08% by mass or more and 0.29% by mass or less, the remainder consisting of unavoidable impurities and aluminum. The aluminum alloy is
Si: 0.40% by mass or more and 0.55% by mass or less,
Cu: 0.04% by mass or less,
Mg: 0.45% by mass or more and 0.60% by mass or less,
Mn: 0.05% by mass or less,
Mg ₂ Si: 0.71% by mass or more and 0.95% by mass or less,
2. The extruded raw tube with internal straight grooves according to claim 1 , characterized in that it contains excess Si: 0.08% by mass or more and 0.25% by mass or less, and the remainder consists of inevitable impurities and aluminum. Si: 0.35 mass% or more and 0.55 mass% or less,
Cu: 0.15% by mass or less,
Mg: 0.45 mass% or more and 0.65 mass% or less,
Mn: 0.05% by mass or less,
Mg ₂ Si: 0.71% by mass or more and 1.03% by mass or less,
An extruded base pipe with internal straight grooves made of an aluminum alloy having a composition containing excess Si: 0.08% by mass or more and 0.29% by mass or less, and the remainder consisting of unavoidable impurities and aluminum,
If the outer diameter is D (mm), the bottom thickness is t (mm), the width of the internal fin formed on the inner surface is W (mm), and the height is h (mm), then h/W is 0.7 The above is a method for manufacturing an internal spiral grooved pipe in which twist drawing is performed on an extruded internal linear grooved pipe having a D/t of 26 or more,
A method for manufacturing an internally spiral grooved tube, characterized in that an aging treatment is performed after the twist drawing process. As the aluminum alloy,
Si: 0.40% by mass or more and 0.55% by mass or less,
Cu: 0.04% by mass or less,
Mg: 0.45% by mass or more and 0.60% by mass or less,
Mn: 0.05% by mass or less,
Mg ₂ Si: 0.71% by mass or more and 0.95% by mass or less,
4. The method for manufacturing an internally spiral grooved tube according to claim 3 , characterized in that an aluminum alloy containing excess Si: 0.08% by mass or more and 0.25% by mass or less, the remainder consisting of unavoidable impurities and aluminum is used. Si: 0.35% by mass or more and 0.55% by mass or less,
Cu: 0.15% by mass or less,
M g: 0.45% by mass or more and 0.65% by mass or less,
Mn: 0.05% by mass or less,
M g ₂ Si: 0.71% by mass or more and 1.03% by mass or less,
An extruded base pipe with internal straight grooves made of an aluminum alloy having a composition of 0.08% by mass or more and 0.29% by mass or less of excess Si, and the remainder consisting of unavoidable impurities and aluminum,
If the outer diameter is D (mm), the bottom thickness is t (mm), the width of the internal fin formed on the inner surface is W (mm), and the height is h (mm), then h/W is 0.7 As described above, an internal spiral grooved tube is manufactured by performing twist drawing on an extruded internal linear grooved tube having a D/t of 26 or more, and a heat exchanger is manufactured using this internal spiral grooved tube. On this occasion,
A method for manufacturing a heat exchanger, comprising subjecting the inner spiral grooved tube to an aging treatment after the twist drawing process and before completing the heat exchanger. As the aluminum alloy,
Si: 0.40 mass% or more and 0.55 mass% or less,
Cu: 0.04% by mass or less,
Mg: 0.45 mass% or more and 0.60 mass% or less,
Mn: 0.05% by mass or less,
Mg ₂ Si: 0.71% by mass or more and 0.95% by mass or less,
6. The method for manufacturing a heat exchanger according to claim 5 , wherein an aluminum alloy containing excess Si: 0.08% by mass or more and 0.25% by mass or less, the remainder consisting of unavoidable impurities and aluminum is used. After assembling the inner spiral grooved tube and the outer fin to form a heat exchanger assembly, when manufacturing the heat exchanger by joining the inner spiral grooved tube and the outer fin,
The internal spiral grooved tube may be subjected to an aging treatment after the twist drawing process and before being combined with the external fin, or the internal spiral grooved tube and the external fin may be assembled and joined and then subjected to an aging treatment. The method for manufacturing a heat exchanger according to claim 5 or 6 , characterized in that: The method for manufacturing a heat exchanger according to any one of claims 5 to 7 , characterized in that a zinc sprayed layer is formed on the outer surface of the extruded raw pipe with internal straight grooves.

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