JP6154611B2 - Aluminum alloy inner surface grooved heat transfer tube - Google Patents

Description

  The present invention relates to an aluminum inner surface grooved heat transfer tube used as a heat transfer tube of a cross fin type heat exchanger used in a domestic air conditioner, a commercial air conditioner, a heat pump type hot water heater and the like. .

  A general cross fin type (also known as fin and tube type) heat exchanger (FIG. 1) inserts a heat transfer tube into an insertion hole opened in an aluminum heat radiating fin and then has a larger inside diameter than the inside of the heat transfer tube. A mandrel for tube expansion having an outer diameter is pushed in to expand the diameter of the heat transfer tube, and the outer peripheral surface of the heat transfer tube and the insertion hole of the aluminum radiation fin are brought into close contact (tube expansion processing: FIG. 2). Thereafter, the heat transfer tube integrated with the aluminum radiation fin is bent into a hairpin shape, and a heat transfer tube (U-shaped tube) bent in a separate U shape is joined by torch brazing to complete (Non-patent Document 1).

  The heat transfer tube used in the cross fin type heat exchanger is one that causes HFC or the like to flow through the tube as a refrigerant to exchange heat, and a copper heat transfer tube having a trapezoidal or triangular protrusion fin on the inner surface of the tube (Hereinafter referred to as an internally grooved tube) is used to improve the efficiency and energy saving of the heat exchanger. The depth and bottom thickness of the groove between the projecting fins shown in FIG. (Thickness of the base of the projecting fin), the shape of the fin (vertical angle, etc.), or various transmissions that define the lead angle of the projecting fin shown in FIG. A heat pipe has been proposed (for example, Patent Document 1). It is said that the heat transfer performance of the internally grooved tube is superior because the surface area inside the tube is increased compared to the smooth tube, and a uniform refrigerant liquid film is formed in the tube by this groove (non- Patent Document 2).

  On the inner surface of the inner grooved tube, projecting fins that are continuously arranged in a spiral form are generally formed by rolling a raw tube (smooth tube). As a rolling method, a roll rolling method (see Fig. 3) in which a grooved plug that freely rotates into the pipe is inserted, a roll that freely rotates from the outside of the pipe is pressed, and the pipe is pulled out while rotating planetary (see Fig. 3), or instead of a roll A ball rolling method using a ball pressing mechanism is known (Non-patent Document 1, Patent Document 2).

  Until now, copper-based materials such as copper and copper alloys have been mainly used for internally grooved pipes, but aluminum-based materials such as aluminum and aluminum alloys (hereinafter referred to as “reducing costs”) , And aluminum alloys) are being studied.

  However, it is assumed that the aluminum alloy has a reduced corrosion resistance when compared to a copper-based material. Therefore, for example, in Patent Document 3, the heat transfer tube has a two-layer structure, an inner layer of the tube is made of an Al—Mn alloy, and an outer surface layer is coated with an Al—Zn alloy as a sacrificial anticorrosion layer. Grooved tubes have been proposed.

  Alternatively, in Patent Document 4, an Al—Mn alloy such as A3003 is used for the inner layer of the heat transfer tube, and the outer surface layer is a sacrificial anticorrosive layer clad with an Al—Zn alloy such as A7072 and the inner grooved tube. Heat exchangers using internally grooved tubes have been proposed.

  On the other hand, in addition to the problem of corrosion resistance, when expanding these aluminum inner-grooved tubes, so-called "fin crushing" occurs in which the top of the protruding fin on the inner surface of the tube is crushed, and the fin-shaped There is a problem that the desired heat transfer performance cannot be obtained due to the collapse and insufficient adhesion with the aluminum radiation fin. This is because the material strength of the inner grooved tube of aluminum or aluminum alloy is lower than that of copper.

  In order to solve the fin crushing at the time of the pipe expansion process, Patent Document 5 proposes forming an oxide film having a thickness of 5 μm or more on the inner surface of the aluminum pipe.

  Further, in Patent Document 6, the inner surface of the aluminum in which the inner layer on which the protruding fins are formed is made of an aluminum alloy layer having a high mechanical strength and the outer layer of the aluminum alloy layer is clad with an aluminum layer having a low mechanical strength. Grooved tubes have been proposed. As a specific alloy, an example is shown in which an inner layer uses an A3003 aluminum alloy and an outer layer uses A1050 (pure aluminum). In this document, the outer peripheral tube bottom portion made of A1050 is preferentially deformed and the outer diameter is expanded, and the inner peripheral tube bottom portion made of A3003 is on the inner surface even when the tube is expanded because the deformation amount is small. It is described that the collapse amount of the projection fin can be suppressed to an allowable range or less.

  Furthermore, Patent Document 7 uses a high-strength alloy obtained by adding Zn to an Al-Mn alloy (A3000 alloy) as an outer layer material of an aluminum tube as an inner grooved tube excellent in tube expansion workability. Three layers using an Al-Mn alloy (A3000 alloy) on the inner side, and an inner inner layer material using a high-strength Al-Mg-Si alloy (A6000 alloy) or Al-Mg alloy (A5000 alloy) A cladding tube has also been proposed.

JP 2003-287383 A JP-A-4-262818 JP 2000-121270 A JP 2009-250562 A JP 2000-205782 A Japanese Patent Application Laid-Open No. 11-351791 JP 2008-266738 A

Masaaki Ito: Heat transfer, 42, 174 (2003), 3 Akio Amagasaki et al .: R & D Kobe Steel Engineering Reports 50, 3 (2000), 66

However, the prior art described in the above literature has room for improvement in the following points.
First, in Patent Documents 1 and 2, Non-Patent Documents 1 and 2, the problems of corrosion resistance and fin crushing when an aluminum alloy is used for a heat transfer tube have not been improved.

  Secondly, Patent Documents 3 and 4 describe methods for improving the corrosion resistance of heat transfer tubes, but the problem of fin crushing has not been improved.

  Thirdly, Patent Documents 5 to 7 describe methods for improving fin crushing of heat transfer tubes, but have room for improvement in the following respects. That is, in Patent Document 5, an anodizing process or the like is added as a process for forming an oxide film inside, which causes a significant increase in processing costs and is not realistic. In addition, it is very difficult to perform such treatment on the inside of a generally long tube.

  In Patent Document 6, it is necessary to make the thickness ratio of pure aluminum of the outer layer thicker than the A3003 alloy of the inner layer. In the two examples disclosed in the embodiment of the same document, the A1050 outer layer is 0.8 mm and the A3003 inner layer is 0.2 mm, or the A1050 outer layer is 0.7 mm and the A3003 inner layer is 0.3 mm. Most are A1050. However, since such a structure reduces the strength of the pipe itself, it is necessary to make the pipe itself a thick-walled pipe in order to obtain a pressure resistance that can withstand the internal pressure of the refrigerant, which increases the material cost and is uneconomical. .

  In Patent Document 7, since a three-layer clad tube is used, the manufacturing process is complicated, and productivity and yield are low, so that there is a problem that the processing cost becomes high.

  The present invention has been made from such a viewpoint, and an object of the present invention is to provide an aluminum alloy internally grooved heat transfer tube that is less likely to cause fin crushing even when the tube is mechanically expanded by a mandrel. It is. Another object is to provide an aluminum alloy internally grooved heat transfer tube which is a heat transfer tube in which such fin crushing is unlikely to occur, and which has better corrosion resistance and can be thinned.

As a result of intensive studies, the present inventors have found that the following heat transfer tubes can solve the problems, and have completed the present invention.
That is, according to the present invention, a plurality of fin-shaped fins are formed on the inner surface, Mn: 0.8 to 1.8% by mass (hereinafter referred to as% by mass), Mg: 0.1 to 0.1% Provided is an aluminum alloy internally grooved heat transfer tube containing 0.6%, the balance being made of Al and inevitable impurities.

  According to this configuration, it is possible to obtain a heat transfer tube in which fin crushing is less likely to occur.

  Further, according to the present invention, a plurality of protrusion-shaped fins are formed on the inner surface, containing Mn: 0.8 to 1.8%, Mg: 0.1 to 0.6%, and further Fe: 0. .60% or less, Si: 0.60% or less, Cu: 0.30% or less, Zn: 0.30% or less, Cr: 0.20% or less, Ti: 0.20% or less, Zr: 0.20 An aluminum alloy inner surface grooved heat transfer tube is provided, which contains one or two or more of the following elements, and the balance is made of Al and inevitable impurities.

  According to this configuration, it is possible to obtain a heat transfer tube in which fin crushing is less likely to occur.

  Moreover, according to this invention, a heat exchanger provided with one of the said heat exchanger tubes is provided.

  According to this configuration, since the heat transfer tube that is unlikely to cause fin crushing is provided, a heat exchanger having excellent heat transfer performance can be obtained.

  Moreover, according to this invention, an air conditioner provided with one of the said heat exchanger tubes is provided.

  According to this configuration, since the heat transfer tube that is unlikely to cause fin crushing is provided, an air conditioner having excellent heat transfer performance can be obtained.

  The heat transfer tube with an inner surface groove made of an aluminum alloy according to the present invention has an effect that the fin crushing hardly occurs even when the tube is mechanically expanded by a mandrel. Or it has the effect that it is hard to generate | occur | produce a fin crushing, has favorable corrosion resistance, and also can be reduced in thickness and material cost can also be suppressed.

It is the elements on larger scale of a cross fin type heat exchanger. It is a figure which shows the mandrel pipe expansion method. It is an example of a roll rolling apparatus. It is a schematic diagram of the cross section of an internally grooved tube. It is a schematic diagram which shows the lead angle of an internal surface protrusion fin.

Hereinafter, embodiments of the present invention will be described in detail. For similar contents,
In order to avoid repeated complications, description will be omitted as appropriate.

<Embodiment 1: Heat transfer tube>
(1-1) Component The heat transfer tube assumed in the present embodiment is used for a heat exchanger for an air conditioner for general households, and its dimensions are, for example, outer diameter φ4.0 to φ9. It is a small-diameter thin tube with a thickness of 54 mm and a bottom wall thickness of about 0.3 to 0.6 mm. For this reason, among various aluminum alloys, the base is based on Al-Mn, which has moderate strength and relatively excellent workability (extrudability, drawability, rollability) for obtaining small-diameter thin-walled tubes. As described above, an aluminum alloy that prevents the crushing of the fins due to the pipe expansion process by improving the strength without impairing the workability by adjusting the element is obtained.

  In the heat transfer tube of the present embodiment, a plurality of fin-shaped fins are formed on the inner surface, Mn: 0.8 to 1.8% by mass (hereinafter referred to as% by mass), Mg: 0.1 to 0.1% It is an aluminum alloy internally grooved heat transfer tube characterized by containing 0.6% and the balance being made of Al and inevitable impurities. This heat transfer tube has an effect that the fin crushing hardly occurs, as demonstrated in the examples described later. Since this heat transfer tube has high pressure resistance, the material cost can be reduced by thinning. Since this heat transfer tube does not necessarily require a complicated production process or a special structure, it is excellent in productivity and quality.

  The heat transfer tube has a plurality of fins formed on the inner surface, contains Mn: 0.8 to 1.8%, Mg: 0.1 to 0.6%, and further Fe: 0.60. % Or less, Si: 0.60% or less, Zn: 0.30% or less, Cr: 0.20% or less, Ti: 0.20% or less, Zr: 0.20% or less Even if it is an aluminum alloy inner surface grooved heat transfer tube containing the above, and the balance being made of Al and inevitable impurities, it is considered that the same effect can be obtained.

  Here, the aluminum alloy is an alloy containing Al as a main component. The Al content in the aluminum alloy is, for example, 90 to 99.9%.

Next, the reason for limiting the components of the heat transfer tube in this embodiment will be described.
Mn is a main additive element for improving the strength of 3000 series alloys, and has the effect of giving solid solution, a part of which precipitates to give strength, and if the added amount is less than 0.8%, the heat transfer tube Insufficient strength, and if it exceeds 1.8%, the effect of improving the strength is saturated, and the amount of coarse intermetallic compound increases, so that defects such as cracks are likely to occur in the manufacturing process of the tube. Therefore, the amount of Mn added is in the range of 0.8 to 1.8%. A more preferable range is 1.0 to 1.5%.

  Mg is an element that has the effect of further improving the strength by solid solution in aluminum and does not impair the workability. If the amount added is less than 0.1%, the strength is insufficient and crushing of the groove due to mechanical expansion cannot be prevented, and if it exceeds 0.6%, the extrudability and the drawability deteriorate. Therefore, the amount of Mg added is in the range of 0.1 to 0.6%. A more preferable range is 0.2 to 0.5%.

  Impurities include Fe, Si, Cu, Zn, etc. These may be Fe: 0.60% or less, Si: 0.60% or less, Cu: 0.30% or less, Zn: 0.30% or less. It does not hinder the effects of the present invention. These content ratios are preferably as small as possible from the viewpoint of not inhibiting the effects of the present invention. Moreover, the lower limit of these content rates is not specifically limited, For example, 0.01, 0.001, 0.0001 or more, or 0% may be sufficient.

  Ti, Cr, Zr may be contained because it has the effect of uniformly refining the ingot structure. However, if it exceeds 0.2%, a giant intermetallic compound is formed or the extrudability is lowered. The content is 0.2% or less. Although the lower limit of these content rates is not specifically limited, For example, 0.01, 0.001, 0.0001 or more, or 0% may be sufficient.

(1-2) Fin In the present embodiment, the hardness of the ridge fin may be HV (Vickers hardness) 33 or more. This is to prevent the occurrence of fin crushing in the pipe expansion process. In order to control this hardness, specifically, the above-mentioned Mn and Mg addition amount is optimized (basically, a higher combination within the component range) and normal processes such as annealing and not overheating. Management should be performed. In addition, if the hardness of the ridge fin is HV33 or more before the pipe expansion process, the ridge fin will not be plastically deformed during the pipe expansion process, so the hardness after the pipe expansion process will also change to a value of HV lower than HV33. Absent.

(1-3) Sacrificial Corrosion Protection Layer The heat transfer tube of this embodiment is assumed to be used as a heat exchanger of an outdoor unit in a salt damage area along the coast, and pure Al or Al- A Zn-based alloy layer may be provided. The heat transfer tube of the present embodiment in which the sacrificial anticorrosion layer is formed is a high-quality heat transfer tube because it is excellent in both corrosion resistance and fin crushing.

  The thickness of these sacrificial anticorrosive layers is preferably 5 to 30% with respect to the total thickness. If the thickness of the sacrificial anticorrosive layer is less than 5% of the total thickness, the effective period of the sacrificial anticorrosive layer in use as a heat exchanger is insufficient, and if it exceeds 30%, the strength of the heat transfer tube decreases and the wall thickness decreases. May become difficult.

  The sacrificial anticorrosive layer may have a natural potential lower than that of the core Al-Mn-Mg alloy. For example, pure aluminum such as A1050 or A7072 (Al-0.8 to 1.3%). An Al—Zn alloy such as a Zn alloy may be used as appropriate.

Next, the example of the embodiment of the formation method of a sacrificial anticorrosion layer is demonstrated.
A combination billet in which a sacrificial anticorrosion alloy sheet (pure Al or Al-Zn alloy) is bent cylindrically on the outside of the cylindrical billet of the Al-Mn-Mg alloy in the heat transfer tube of the present embodiment is produced. Is heated to 350 to 600 ° C. in a heating furnace and homogenized. The combination billet is inserted between the extrusion die and the extrusion ram nose and inserted into the container. With the extrusion die and the extrusion ram nose fixed, a mandrel having an outer diameter larger than the inner diameter of the core material is press-fitted to expand the core material. To expel the air between the core and the skin. Next, the mandrel is fixed at a predetermined position, the extrusion hollow stem is advanced, the combination billet is extruded through a die, and a two-layer clad extruded tube is obtained. Next, the extruded tube is drawn to a predetermined outer diameter and thickness to obtain a two-layer clad elementary tube (smooth tube). For this drawing process, it is desirable to use a draw block type continuous drawing machine with high productivity.

  Alternatively, the cylindrical sacrificial anticorrosive billet is heated to 350-600 ° C., and the hollow hollow billet obtained by shrink-fitting the cylindrical hollow billet inside is extruded. It is also possible to obtain a two-layer clad base tube (smooth tube).

  Alternatively, a two-layer clad sheet obtained by clad rolling a sacrificial anti-corrosion material sheet on one side of an aluminum alloy core sheet, and roll-forming the sheet into a tubular shape, and then welding the sheet abutting surface to form a two-layer clad electro-resistance tube It is good.

  The above is a description of a method for forming a two-layer element tube (smooth tube) in which a sacrificial anticorrosive layer is formed by clad extrusion / drawing or clad rolling. As other methods, Al—Mn in the heat transfer tube of this embodiment is used. -A method of forming an Al-Zn diffusion layer by applying Zn diffusion heat treatment after spraying Zn on an extruded tube of Mg-based alloy (by hot extrusion or conform extrusion) or a drawing tube. . In this case, it is desirable that the temperature and time of the diffusion heat treatment are appropriately set so that the Zn diffusion layer is in the range of 5 to 30% with respect to the total thickness. It is industrially preferable that the temperature is about 400 to 500 ° C. and about 2 to 8 hours. Only when this Zn spraying method is adopted, Zn spraying and diffusion heat treatment may be performed after performing the rolling process described later.

  In order to facilitate the rolling process in the next step, it is desirable to subject the raw pipe (smooth pipe) on which the sacrificial anticorrosive layer is formed in this manner to an annealing softening process in advance. In that case, it is industrially preferable that the annealing condition is 300 to 400 ° C. and the time is about 2 to 8 hours.

  In addition, these smooth tubes are slightly reduced in outer diameter and wall thickness in the subsequent rolling process. Therefore, the dimensions (outer diameter, wall thickness) of the raw pipe are set larger than the inner grooved pipe as the final product in consideration of the decrease.

  Next, the smooth tube is subjected to a rolling process by a roll rolling method, a ball rolling method, or the like to manufacture an internally grooved tube having a protruding fin.

(1-4) Structure and processing method The inner grooved tube of the present embodiment can be manufactured in various dimensions according to the use of the heat exchanger, but when used in a domestic air conditioner, production in the manufacture of the tube The outer diameter is preferably 4.0 mm or more from the viewpoint of performance, and the outer diameter is preferably 9.95 mm or less from the viewpoint of reducing the size and weight of the heat exchanger.

  Further, the thickness of the bottom wall is preferably 0.3 mm or more from the viewpoint of pressure resistance and 0.6 mm or less from the viewpoint of reducing the size and weight of the heat exchanger.

  Further, the height H of the inner surface projecting fin is 0.1 to 0.4 mm, the apex angle α of the inner surface projecting fin is 10 to 40 °, the number of the inner surface projecting fins is 40 or more, and the lead angle β (inner surface projecting fin). The angle between the strip fin and the longitudinal direction of the pipe is preferably 20 ° or more.

  After the rolling process, annealing softening treatment may be performed. This is for removing the processing distortion introduced at the time of rolling and facilitating hairpin bending (meandering bending). What is necessary is just to give annealing for about 2 to 8 hours at 300-400 degreeC by a conventional method.

  The inner grooved tube of the present embodiment manufactured in this manner is brought into close contact with the insertion hole of the aluminum radiating fin by tube expansion processing. In order to obtain good adhesion, it is appropriate to set the clearance between the insertion hole and the heat transfer tube so that the tube expansion rate (outer diameter increase rate) is about 4 to 6%. It should be noted that the pipe expanding process can improve production efficiency by a hydraulic pipe expanding method in which an internal pressure is applied to the pipe by hydraulic pressure or water pressure instead of a mechanical pipe expanding method using a mandrel.

<Embodiment 2: Heat exchanger>
Other embodiment of this invention is a heat exchanger provided with the heat exchanger tube which concerns on said embodiment. Since this heat exchanger includes a heat transfer tube in which fin crushing is difficult to occur, heat transfer performance is good and efficiency is excellent. Or since this heat exchanger is equipped with the heat exchanger tube which is hard to generate | occur | produce fin collapse and was excellent in corrosion resistance, it is excellent in heat transfer performance and durability.

<Embodiment 3: Air conditioner>
Other embodiment of this invention is an air conditioner provided with the heat exchanger tube which concerns on said embodiment. Since this air conditioner includes a heat transfer tube in which fins are not easily crushed, heat transfer performance is good and efficiency is high. Or since this air conditioner is equipped with the heat exchanger tube which is hard to generate | occur | produce fin collapse and was excellent in corrosion resistance, it is excellent in heat transfer performance and durability.

  As mentioned above, although embodiment of this invention was described, these are illustrations of this invention and various structures other than the above are also employable.

Next, the present invention will be described in more detail based on examples.
A cylindrical billet of an aluminum alloy having the composition shown in Table 1 was cast, and an extruded tube having an outer diameter of 47 mm and a wall thickness of 3.5 mm was obtained by an indirect extrusion method. The extruded tube was subjected to a drawing process using a draw block type continuous drawing machine to obtain a drawn tube having an outer diameter of 10 mm and a wall thickness of 0.45 mm.

  For Nos. 8 to 14 and Nos. 22 to 28 on which the sacrificial anticorrosive layer was formed, the cylindrical sacrificial anticorrosive billet of A1050 or A7072 was heated to 450 ° C., and the cylindrical core billet was shrink-fitted inside to form two layers A hollow billet was obtained, this was indirectly extruded, and then subjected to a drawing process using a draw block type continuous drawing machine to obtain a drawing tube having an outer diameter of φ10 mm and a wall thickness of 0.48 mm.

  The drawn tube thus obtained is annealed and softened at 360 ° C. for 2 hours, and then a floating plug, a rod and a plug with a grooved plug are inserted, and a floating die, a machining head, and a molding die are inserted. The inner surface is grooved by passing it through, the outer diameter: φ7 mm, the bottom wall thickness: 0.35 mm, the height H of the ridge fins: 0.22 mm, the number of ridge fins is 50, the apex angle α : An internally grooved tube having a lead angle β of 35 ° was prepared. In addition, about No8-14, No21-26, it adjusted with the billet thickness of the sacrificial anticorrosive material in an extrusion process so that the sacrificial anticorrosive layer might be 0.035 mm (ratio of 10% with respect to bottom thickness). . Furthermore, the annealing softening process was finally performed at 360 degreeC for 2 hours, and the internally grooved pipe was completed.

  In order to evaluate the characteristics of the internally grooved tubes of the inventive examples and comparative examples thus obtained, the following tests were conducted. The obtained results are shown in Table 2.

(A) Tensile test A tensile test was performed according to JIS Z2241 in order to measure the strength of the internally grooved tube.

(B) Pipe expansion workability The pipe with an inner diameter of 7 mm in outer diameter was subjected to pipe expansion work using a steel mandrel so that the outer diameter increased by 5%. Thereafter, the cross section of the tube was observed, and the amount of decrease in the fin height H of the ridge was measured to evaluate the amount of fin collapse. In order to obtain heat transfer characteristics as a heat exchanger, it is desirable that the amount of fin collapse is 0.01 mm or less. Moreover, the hardness of the center part of the rib fin cross section before and after the pipe expansion process was measured with a micro Vickers hardness meter.

(C) Corrosion resistance In order to evaluate external corrosion resistance, a CASS test was performed for 1500 hours on each internally grooved tube in accordance with JIS Z8681. After the test, the surface corrosion products of the test tube were removed, the corrosion state of the tube was observed, and the external corrosion resistance was evaluated by the presence or absence of through holes.

  As is apparent from Table 2, the aluminum inner grooved tubes No1 to No14 of the present invention have a reduction amount of the fin height H (fin collapse amount) of 0.01 mm or less, and among them, the protrusion before expansion. The fin collapse amount of No3-No7 and No10-No14 whose hardness of a fin part is HV35 or more is zero, and is very favorable. Moreover, No8-No14 in which the sacrificial anticorrosive layer was formed has good external corrosion resistance with no occurrence of through holes. Further, the tensile strength of the tube is 119 MPa or more, and the strength is higher than that of, for example, 91 MPa (corresponding to A3003) of Comparative Example No. 16, and therefore the pressure resistance of the tube is also high.

  In contrast, No. 15 to No. 18 and No. 22 to No. 25 with a small amount of Mn and Mg have a large collapse of the projecting fins at the time of tube expansion, and the strength of the tube itself is also low. On the other hand, No19 to No21 and No26 to No28 with large amounts of Mn and Mg were cracked in the drawing process or rolling process, and the inner grooved tube itself could not be manufactured.

  In the above, this invention was demonstrated based on the Example. It is to be understood by those skilled in the art that this embodiment is merely an example, and that various modifications are possible and that such modifications are within the scope of the present invention.

1 Aluminum radiation fin 2 Heat transfer tube (inner grooved tube)
3 Louver 4 Expanded plug (mandrel)
5 Elementary tube (smooth tube)
6 Rolled plug 7 Rotating roll 8 Internal spiral grooved tube 9 Projection fin 10 Sacrificial anticorrosion layer

Claims (7)

A heat transfer tube with an inner surface groove made of aluminum alloy for tube expansion processing,
40 or more ridge-shaped fins are formed on the inner surface, Mn: 0.8 to 1.8% by mass (hereinafter referred to as “%”) , Mg: 0.1 to 0.6% Fe: 0.60% or less, Si: 0.60% or less, Cu: 0.30% or less, Zn: 0.30% or less, Cr: 0.20% or less, Ti: 0.20% or less Zr: containing one or more of 0.20% or less, the balance is made of Al and inevitable impurities, and the apex angle α of the ridge-shaped fin is 10 to 40 °,
A pure Al or Al-Zn alloy layer was formed on the outer surface as a sacrificial anticorrosive,
The thickness of the sacrificial anticorrosion layer is 5 to 30% with respect to the total thickness. The heat transfer tube according to claim 1 ,
A heat transfer tube with an inner surface groove made of aluminum alloy for tube expansion processing, wherein a lead angle β formed between the protruding fin and the longitudinal direction of the tube is 20 ° or more. The heat transfer tube according to claim 1 or 2 ,
A heat transfer tube with an inner surface groove made of aluminum alloy for tube expansion processing, wherein the protrusion-shaped fin has a hardness of HV33 or more. A heat transfer tube according to any one of claims 1 to 3 ,
A heat transfer tube with an inner surface groove made of aluminum alloy for tube expansion processing, wherein the outer diameter of the heat transfer tube is 4.0 to 9.54 mm. The heat transfer tube according to any one of claims 1 to 4 ,
A heat transfer tube with an inner surface groove made of an aluminum alloy for tube expansion processing, wherein the heat transfer tube has a bottom wall thickness of 0.3 to 0.6 mm. Comprising a heat exchanger tube according to any one of claims 1 to 5, the heat exchanger. An air conditioner comprising the heat transfer tube according to any one of claims 1 to 5 .