JP2014173156A - Copper alloy seamless pipe for heat transfer pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy seamless pipe for a heat transfer pipe high in strength, little in strength degradation by brazing, high in creep deformation resistance and in inhibitory effect of intermediate temperature brittleness.SOLUTION: There is provided a copper alloy seamless pipe for a heat transfer pipe obtained by processing a copper alloy containing Sn, 0.01 to 0.08 mass% of Zr, 0.004 to 0.04 mass% of P and the balance Cu with inevitable impurities, and the contents of Sn and Zr in the copper alloy satisfies the formula (1):(1)0.4≤A+2B≤0.85, where A represents the content of Sn (mass%) and B represents the content of Zr (mass%)), and an electric conductivity of the copper alloy seamless pipe for the heat transfer pipe satisfies the formula (2):(1)ρ2-ρ1≥0.3(%IACS), where ρ1 represents electric conductivity after a solution treatment (%IACS) and ρ2 represents electric conductivity after an aging treatment (%IACS).

Description

  The present invention relates to a seamless pipe made of a copper alloy used for a heat transfer pipe or a refrigerant pipe such as a heat exchanger for an air conditioner or a heat exchanger for a refrigerator.

  Conventionally, seamless pipes made of copper alloy have been adopted as heat transfer tubes for heat exchangers used in air conditioners such as room air conditioners and packaged air conditioners, refrigerators, etc., strength, workability, heat transfer, etc. Phosphorus-deoxidized copper tubes (JIS C1220T), which have a good balance between their physical properties, materials and processing costs, have been used.

  In recent years, in these heat exchangers, it has become necessary to reduce the thickness of seamless pipes due to demands for weight reduction or cost reduction, and it is difficult to reduce the thickness of conventional phosphorous deoxidized copper pipes because the strength is low. Therefore, there is a demand for the development of a copper alloy seamless pipe that replaces this.

  Therefore, as a solid solution strengthened copper alloy, Patent Document 1 proposes a copper alloy to which Sn is added. Moreover, as a solid solution strengthening and precipitation strengthening type copper alloy, the patent document 2 and the patent document 3 have proposed the copper alloy which added Sn and Zr.

JP 2003-268467 A (Claims) WO2008 / 041777 (Claims) JP2011-94174A (Claims)

  Copper alloy seamless pipes used for heat transfer pipes and refrigerant pipes such as heat exchangers for air conditioners and heat exchangers for refrigerators may cause fatigue cracks due to thermal fatigue due to repeated thermal expansion and contraction. There is. In addition, tension is generated in the seamless pipe with thermal expansion, and there is a risk of creep deformation depending on the operating temperature.

  Therefore, in addition to “high strength” and “low strength loss due to brazing”, copper alloy seamless tubes used for heat transfer tubes or refrigerant pipes for heat exchangers for air conditioners, heat exchangers for refrigerators, etc. It is required to have heat-resistant fatigue crack generation characteristics and creep deformation resistance characteristics.

  However, a solid solution strengthened copper alloy seamless pipe to which Sn is added as in Cited Document 1 is brittle at an intermediate temperature and easily causes thermal fatigue and creep fracture in a brittle temperature range. At the time of manufacturing the heat exchanger, heating such as brazing is performed in a state where tension is applied to the seamless pipe, so that intermediate temperature brittleness is generated and brittle cracking is likely to occur.

  There are S and H as factors for promoting the intermediate temperature brittleness. Although the intermediate temperature brittleness can be suppressed to some extent by reducing the S and H contents to the limit, it is not sufficient. In addition, in order to reduce the S content to the limit, it is necessary to use a high-purity metal, which is not preferable in terms of cost. Further, in order to reduce the H content to the limit, it is not preferable in terms of cost, for example, a long-time molten metal treatment is required and a melt casting with controlled atmosphere is required.

  Therefore, it is desirable to effectively suppress the intermediate temperature brittleness even if the contents of S and H are at a normal level (a level that does not decrease to the limit). Note that the S and H contents at a normal level (a level that does not decrease to the limit) are such that S is about 0.0005 to 0.0008 mass% and H is 0.0002 to 0.0010 mass%. Degree.

  On the other hand, in the solid solution strengthened and precipitation strengthened type copper alloy seamless pipes to which Sn and Zr are added as in Patent Document 2 and Patent Document 3, the addition of Zr increases the strength and the strength by brazing. In addition to a small decrease, the occurrence of intermediate temperature brittleness can be suppressed to some extent.

  However, there is a demand for further improvement in heat-resistant fatigue crack generation characteristics and creep deformation resistance characteristics.

  Accordingly, an object of the present invention is to provide a copper alloy seamless pipe for a heat transfer tube that has high strength, little strength reduction due to brazing, high creep deformation resistance, and high intermediate temperature brittleness suppressing effect. It is in.

  As a result of intensive studies to solve the above-described problems in the prior art, the present inventors have included a copper alloy with a specific content of Sn and Zr, and in addition, Zr in an appropriate state in the copper alloy. By making it exist, it has been found that a copper alloy seamless pipe for a heat transfer tube having high strength, less strength decrease due to brazing, high creep deformation resistance, and high suppression effect of intermediate temperature brittleness can be obtained, The present invention has been completed.

That is, the present invention (1) is a copper alloy seamless pipe for a heat transfer tube obtained by processing a copper alloy,
This copper alloy contains Sn, 0.01-0.08 mass% Zr, and 0.004-0.04 mass% P, and consists of the remainder Cu and inevitable impurities, The content of Sn and Zr of the following formula (1):
(1) 0.4 ≦ A + 2B ≦ 0.85
(In the formula, A represents the Sn content (mass%), and B represents the Zr content (mass%).)
The filling,
The electrical conductivity of the copper alloy seamless pipe for heat transfer tube is represented by the following formula (2):
(2) ρ2−ρ1 ≧ 0.3 (% IACS)
(In the formula, ρ1 indicates the electric conductivity after solution treatment (% IACS), and ρ2 indicates the electric conductivity after aging treatment (% IACS).)
Meeting,
A copper alloy seamless pipe for heat transfer tubes is provided.

Further, the present invention (2) is a copper alloy seamless pipe for heat transfer tubes obtained by processing a copper alloy,
This copper alloy contains Sn, 0.01-0.08 mass% Zr, and 0.004-0.04 mass% P, and consists of the remainder Cu and inevitable impurities, The content of Sn and Zr of the following formula (1):
(1) 0.4 ≦ A + 2B ≦ 0.85
(In the formula, A represents the Sn content (mass%), and B represents the Zr content (mass%).)
The filling,
The electrical conductivity of the copper alloy seamless pipe for heat transfer tube is represented by the following formula (3):
(3) ρ4-ρ3 ≧ 0.3 (% IACS)
(In the formula, ρ3 indicates the electric conductivity after heating-water cooling test at 950 ° C. for 10 minutes (% IACS), and ρ4 indicates the electric conductivity after heating-water cooling test at 550 ° C. for 60 minutes (% IACS). Point to.)
Meeting,
A copper alloy seamless pipe for heat transfer tubes is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the copper alloy seamless pipe for heat exchanger tubes with high intensity | strength, there is little intensity | strength fall by brazing, the creep deformation-proof characteristic is high, and the suppression effect of intermediate temperature brittleness can be provided. .

The copper alloy seamless pipe for heat transfer tubes of the first embodiment of the present invention (hereinafter also referred to as the copper alloy seamless pipe for heat transfer tubes of the present invention (1)) is a heat transfer tube obtained by processing a copper alloy. Copper alloy seamless pipe for
This copper alloy contains Sn, 0.01-0.08 mass% Zr, and 0.004-0.04 mass% P, and consists of the remainder Cu and inevitable impurities, The content of Sn and Zr of the following formula (1):
(1) 0.4 ≦ A + 2B ≦ 0.85
(In the formula, A represents the Sn content (mass%), and B represents the Zr content (mass%).)
The filling,
The electrical conductivity of the copper alloy seamless pipe for heat transfer tube is represented by the following formula (2):
(2) ρ2−ρ1 ≧ 0.3 (% IACS)
(In the formula, ρ1 indicates the electric conductivity after solution treatment (% IACS), and ρ2 indicates the electric conductivity after aging treatment (% IACS).)
Meeting,
It is a copper alloy seamless pipe for heat transfer tubes.

The copper alloy seamless pipe for heat transfer tubes of the second aspect of the present invention (hereinafter also referred to as the copper alloy seamless pipe for heat transfer tubes of the present invention (2)) is a heat transfer tube obtained by processing a copper alloy. Copper alloy seamless pipe for
This copper alloy contains Sn, 0.01-0.08 mass% Zr, and 0.004-0.04 mass% P, and consists of the remainder Cu and inevitable impurities, The content of Sn and Zr of the following formula (1):
(1) 0.4 ≦ A + 2B ≦ 0.85
(In the formula, A represents the Sn content (mass%), and B represents the Zr content (mass%).)
The filling,
The electrical conductivity of the copper alloy seamless pipe for heat transfer tube is represented by the following formula (3):
(3) ρ4-ρ3 ≧ 0.3 (% IACS)
(In the formula, ρ3 indicates the electric conductivity after heating-water cooling test at 950 ° C. for 10 minutes (% IACS), and ρ4 indicates the electric conductivity after heating-water cooling test at 550 ° C. for 60 minutes (% IACS). Point to.)
Meeting,
It is a copper alloy seamless pipe for heat transfer tubes.

  The copper alloy seamless pipe (1) for heat transfer tubes of the present invention and the copper alloy seamless tube (2) for heat transfer tubes of the present invention are the electrical conductivity of the copper alloy seamless tube (1) for heat transfer tubes of the present invention. However, while satisfy | filling Formula (2), it is the same except that the electrical conductivity of the copper alloy seamless pipe for heat-transfer tubes (2) of this invention differs in the point which satisfy | fills Formula (3).

  The copper alloy seamless pipe (1) for heat transfer tubes of the present invention and the copper alloy seamless tube (2) for heat transfer tubes of the present invention are a heat exchanger for an air conditioner, a heat exchanger for a refrigerator, and a natural gas refrigerant heat pump type. It is a seamless pipe used as a heat transfer pipe or refrigerant pipe for a heat exchanger or the like, and is a copper alloy seamless pipe made of a copper alloy, that is, a copper alloy seamless pipe for a heat transfer pipe.

  The copper alloy seamless pipe (1) for heat transfer tubes of the present invention (1) or the copper alloy seamless pipe (2) for heat transfer tubes of the present invention contains Sn, Zr and P as essential elements, with the remainder Cu and It is a copper alloy composed of inevitable impurities.

  In the copper alloy seamless pipe for heat transfer tubes of the present invention (1) or the copper alloy seamless pipe for heat transfer tubes of the present invention (2), Sn has an effect of improving the strength of the copper alloy by solid solution strengthening and at room temperature. Has the effect of improving the ductility of the steel. In addition, these elements are advantageous in production because they can be alloyed at a relatively low temperature.

  In the copper alloy seamless pipe for heat transfer tubes of the present invention (1) or the copper alloy seamless pipe for heat transfer tubes of the present invention (2), Zr has an effect of improving the strength of the copper alloy by precipitation strengthening. In addition, Zr has the effect of reducing the decrease in strength by suppressing the coarsening of crystal grains because Zr precipitates remain on the premise that the brazing temperature does not become excessively high.

  In the copper alloy according to the copper alloy seamless pipe (1) for heat transfer tubes of the present invention or the copper alloy seamless pipe (2) for heat transfer tubes of the present invention, the content of Zr is 0.01 to 0.08 mass%. It is. When the content of Zr in the copper alloy is less than 0.01% by mass, the effect of suppressing the coarsening of the crystal grains is small, the strength is decreased by brazing, and the solid solution strengthening by Sn and precipitation by Zr are performed. Even if strengthening is combined, the strengthening of the copper alloy becomes insufficient. On the other hand, when the content of Zr in the copper alloy exceeds 0.08% by mass, excessive precipitation hardening occurs, which causes a decrease in workability. In particular, the rolling processability in the cold is deteriorated. As a result, the transfer of the spiral groove shape on the inner surface of the tube becomes insufficient, making it difficult to obtain the heat transfer performance obtained with C1220.

The content of Sn in the copper alloy according to the present invention for the copper alloy seamless pipe for heat transfer tubes (1) or the copper alloy for the heat transfer tubes according to the present invention (2) is defined as A (mass%) and the content of Zr. Is B (mass%), in the copper alloy according to the copper alloy seamless pipe for heat transfer tubes of the present invention, A + 2B is 0.4 or more and 0.85 or less, that is, the following formula (1):
(1) 0.4 ≦ A + 2B ≦ 0.85
The filling,
A + 2B is preferably 0.42 or more and 0.83 or less, that is, the following formula (1a):
(1a) 0.42 ≦ A + 2B ≦ 0.83
Meet. By keeping A + 2B within the above range and the Zr content of 0.01 to 0.08 mass%, even when severe workability is required, the strength of the seamless pipe can be kept to a minimum. it can. On the other hand, when A + 2B is less than the above range, the strength of the seamless pipe is insufficient, and when it exceeds the above range, cold workability is remarkably lowered.

  The P content in the copper alloy seamless pipe (1) for heat transfer tubes of the present invention or the copper alloy seamless tube (2) for heat transfer tubes of the present invention is 0.004 to 0.04 mass%. Preferably, it is 0.015-0.030 mass%. It is shown that the deoxidation in the material is sufficient when the copper alloy contains 0.004% by mass or more of the P element. And when there is too much content of P in a copper alloy, since the heat conductivity of a copper alloy will become low, content of P in a copper alloy is 0.040 mass% or less.

About the electrical conductivity of the copper alloy seamless pipe (1) for heat transfer tubes of the present invention, ρ2-ρ1 is 0.3 or more, that is, the following formula (2):
(2) ρ2−ρ1 ≧ 0.3 (% IACS)
(In the formula, ρ1 indicates the electric conductivity after solution treatment (% IACS), and ρ2 indicates the electric conductivity after aging treatment (% IACS).)
The filling,
Preferably ρ2-ρ1 is 0.5 or more and 20 or less, that is, the following formula (2a):
(2a) 0.5 ≦ ρ2−ρ1 ≦ 20
Meet. Moreover, about the electrical conductivity of the copper alloy seamless pipe (2) for heat-transfer tubes of this invention, (rho) 4- (rho) 3 is 0.3 or more, ie, following formula (3):
(3) ρ4-ρ3 ≧ 0.3 (% IACS)
(In the formula, ρ3 indicates the electric conductivity after heating-water cooling test at 950 ° C. for 10 minutes (% IACS), and ρ4 indicates the electric conductivity after heating-water cooling test at 550 ° C. for 60 minutes (% IACS). Point to.)
The filling,
Preferably ρ4-ρ3 is 0.5 or more and 20 or less, that is, the following formula (3a):
(3a) 0.5 ≦ ρ4-ρ3 ≦ 20
Meet.

  In the present invention, the solution treatment refers to a treatment for sufficiently dissolving the Zr-based intermetallic compound crystallized in the ingot cooling process in the melting and casting process, and the aging treatment is a Zr-based metal. It refers to a treatment for precipitating intermetallic compounds. The copper alloy seamless pipe for heat transfer tubes of the present invention is manufactured by performing the steps of “melting and casting process → hot extrusion process → cold working process → intermediate annealing process and rolling process → aging process if necessary”. . And in such a manufacturing process, the heating in a hot extrusion process turns into the solution treatment which fully dissolves the Zr type | system | group intermetallic compound crystallized in the cooling process of the ingot in a melt | dissolution and a casting process.

  In copper alloy seamless pipes, if the Zr crystallized during the ingot cooling process in the melting and casting process does not sufficiently dissolve in the solution treatment, it is necessary to obtain the strength corresponding to the Zr content. The amount and distribution of fine precipitates precipitated by aging treatment are not appropriate. In addition, the Zr-based crystallized material that could not be completely dissolved by the solution treatment not only contributes to the improvement of strength, but also in the subsequent cold working process, rolling process, bending process during heat exchanger production. Workability will be hindered. Furthermore, the solid solution Zr traps S by forming S and a compound in the solidification process or solution treatment during casting, and traps H that forms grain boundary voids during hot extrusion. Improves creep deformation resistance and suppresses intermediate temperature brittleness. Thus, Zr dissolved in solution after the solution treatment not only contributes to precipitation strengthening by aging treatment, which is a subsequent process, but also contributes to improvement in creep deformation resistance and suppression of intermediate temperature brittleness. Further, by making the Zr precipitation state appropriate in the aging treatment, the intermediate temperature brittleness suppressing effect is enhanced.

However, it is difficult to quantitatively determine the solid solution state of Zr in the solution treatment and the precipitation state of Zr in the aging treatment. Accordingly, as a result of intensive studies, the inventors have determined that the solid solution state of Zr in the solution treatment is based on the difference between the electrical conductivity after the solution treatment and the electrical conductivity after the aging treatment (ρ2−ρ1). It was also found that the precipitation state of Zr in the aging treatment can be grasped, and by defining ρ2-ρ1 in a specific range, the creep deformation resistance can be improved and the intermediate temperature brittleness can be suppressed. That is, about the electrical conductivity of the copper alloy seamless pipe (1) for heat transfer tubes of the present invention, ρ2-ρ1 is 0.3 or more, that is, the following formula (2):
(2) ρ2−ρ1 ≧ 0.3 (% IACS)
The filling,
Preferably ρ2-ρ1 is 0.5 or more and 20 or less, that is, the following formula (2a):
(2a) 0.5 ≦ ρ2−ρ1 ≦ 20
Meet. When ρ2-ρ1 is within the above range, the creep deformation resistance can be improved and the intermediate temperature brittleness can be suppressed.

In addition, the inventors of the present invention have a solution solution by a difference (ρ 4 −ρ 3) between the electrical conductivity after a heating-water cooling test at 950 ° C. for 10 minutes and the electrical conductivity after a heating-water cooling test at 550 ° C. for 60 minutes. The solid solution state of Zr in the treatment and the precipitation state of Zr in the aging treatment can be grasped, and by defining ρ4-ρ3 in a specific range, the creep resistance characteristic deformation is improved and the intermediate temperature brittleness is suppressed. I found that I can do it. That is, about the electrical conductivity of the copper alloy seamless pipe (2) for heat exchanger tubes of the present invention, ρ4-ρ3 is 0.3 or more, that is, the following formula (3):
(3) ρ4-ρ3 ≧ 0.3 (% IACS)
The filling,
Preferably ρ4-ρ3 is 0.5 or more and 20 or less, that is, the following formula (3a):
(3a) 0.5 ≦ ρ4-ρ3 ≦ 20
Meet. When ρ4-ρ3 is within the above range, the creep deformation resistance can be improved and the intermediate temperature brittleness can be suppressed.

  In the present invention, the heating-water cooling test at 950 ° C. for 10 minutes is a test in which the copper alloy seamless tube to be tested is heated at 950 ° C. ± 25 ° C. for 10 minutes and then water-cooled. The test object was placed in an electric furnace set at 950 ± 25 ° C. in a nitrogen gas atmosphere, and after the furnace temperature returned to 950 ° C., it was held at 950 ° C. ± 25 ° C. for 10 minutes, and then 950 It is carried out by immediately cooling with water from ℃. Then, the electrical conductivity (% IACS) of the test object after the heating-water cooling test at 950 ° C. for 10 minutes is measured to obtain ρ3.

  Further, in the present invention, the heating-water cooling test at 550 ° C. for 60 minutes means that the copper alloy seamless tube to be tested is heated and cooled at 950 ° C. for 10 minutes and then 550 ° C. ± 10 In this test, the test object is heated at 60 ° C. for 60 minutes and then cooled with water. First, the test object is heated at 950 ° C. ± 25 ° C. for 10 minutes in the same manner as the 950 ° C. heating-water cooling test at 950 ° C. The test object that was immediately cooled with water and then heated at 950 ° C. for 10 minutes and cooled with water was placed in a salt bath furnace, held at 550 ° C. ± 10 ° C. for 60 minutes, and then immediately cooled with water. Done. Then, the electrical conductivity (% IACS) of the test object after the heating-water cooling test at 550 ° C. ± 10 ° C. for 60 minutes is measured to obtain ρ4.

  The copper alloy according to the copper alloy seamless pipe (1) for heat transfer tubes of the present invention or the copper alloy seamless pipe (2) for heat transfer tubes of the present invention may further contain S atoms. When the copper alloy according to the copper alloy seamless pipe (1) for heat transfer tubes of the present invention or the copper alloy seamless pipe (2) for heat transfer tubes of the present invention further contains S, the inclusion of S in the copper alloy The amount is 0.0005 to 0.0010% by mass. Moreover, the copper alloy which concerns on the copper alloy seamless pipe (1) for heat-transfer tubes of this invention or the copper alloy seamless pipe (2) for heat-transfer tubes of this invention may contain H further. When the copper alloy according to the copper alloy seamless pipe (1) for heat transfer tubes of the present invention or the copper alloy seamless pipe (2) for heat transfer tubes of the present invention further contains H, the inclusion of H in the copper alloy The amount is 0.0002 to 0.0020% by mass. If the content of S or H in the copper alloy exceeds the above range, S or H cannot be sufficiently supplemented by the dissolved Zr, and the creep deformation resistance is improved, the intermediate temperature The effect of suppressing brittleness cannot be obtained. On the other hand, when the S content or the H content in the copper alloy is less than the above range, effects of improving creep deformation resistance and suppressing intermediate temperature brittleness can be obtained, but the cost tends to increase.

  The copper alloy seamless pipe for heat transfer tubes of the present invention is produced by melting, casting and cooling → hot extrusion and cooling → cold working → if necessary, intermediate annealing treatment and rolling → aging treatment.

  First, melting, casting and cooling are performed. In melting and casting, a billet containing a predetermined element in a predetermined content is obtained by melting and casting according to a conventional method. For example, the content of the bullion of the copper ingot and the copper alloy seamless tube for the heat transfer tube of the present invention in the element contained in the copper alloy seamless tube for the heat transfer tube of the present invention The ingredients are adjusted so as to have a predetermined content, the components are adjusted, and then the billet is cast using a high-frequency melting furnace or the like. The billet is then cooled after casting.

  Subsequently, hot extrusion and cooling are performed. In hot extrusion, a billet obtained by casting is heated at a predetermined temperature and hot extruded. Hot extrusion is performed by mandrel extrusion. That is, hot extrusion is performed with a mandrel inserted into a billet previously perforated cold before heating, or a billet perforated hot before extrusion. And after performing hot extrusion, it cools rapidly and obtains a hot extrusion element pipe.

  Next, cold working is performed. In cold working, the hot extruded element tube obtained by hot extrusion is cold processed, such as cold rolling or cold drawing, to reduce the outer diameter and wall thickness of the tube, obtain.

  In the case of obtaining an inner smooth tube (bearing tube) in which no inner groove is formed, the cold-worked seamless tube obtained by cold working is heated at 400 to 600 ° C. and then cooled. Perform aging treatment. And the copper alloy seamless pipe (1) for heat transfer tubes of this invention or the copper alloy seamless pipe (2) for heat transfer tubes of this invention is obtained by performing an aging treatment.

  When obtaining an internally grooved pipe in which an internal groove is formed, after cold working, a seamless elementary pipe obtained by cold working is subjected to intermediate annealing by heating at 400 to 600 ° C., and then rolled. I do. Rolling is done by placing a rolling plug with a spiral groove on the outer surface in a seamless tube, pressing it from the outside of the tube with multiple rolling balls that rotate at high speed, This is done by transferring the groove of the rolling plug. Next, the rolled seamless pipe is subjected to an aging treatment. The aging treatment is performed by heating and cooling the rolled seamless pipe at 400 to 600 ° C. And the copper alloy seamless pipe (1) for heat transfer tubes of this invention or the copper alloy seamless pipe (2) for heat transfer tubes of this invention is obtained by performing an aging treatment.

  And in the copper alloy seamless pipe (1) for heat transfer tubes of the present invention, the electrical conductivity is expressed by the formula (2): ρ2-ρ1 ≧ 0.3 (% IACS), preferably the formula (2a): 0.5. In the method of ≦ ρ2−ρ1 ≦ 20, and the copper alloy seamless pipe (2) for heat transfer tubes of the present invention, the electrical conductivity is expressed by the formula (3): ρ4-ρ3 ≧ 0.3 (% IACS), Preferably, the method of formula (3a): 0.5 ≦ ρ4-ρ3 ≦ 20 includes, for example, a method of adjusting the cooling rate of the billet in the cooling after melting and casting. The inventors of the present invention differed in the presence state of Zr in the copper alloy due to the difference in the billet cooling rate in the cooling after melting and casting, and the difference in the existence state of Zr after melting and casting was “ρ2-ρ1”. And the value of “ρ4-ρ3” was found to be affected. Depending on the diameter of the billet, the cooling conditions after casting, the solution treatment conditions, the aging conditions, etc., an appropriate cooling rate for adjusting the electrical conductivity to the formula (2), preferably the formula (2a), or Since the cooling rate suitable for adjusting to the formula (3), preferably the formula (3a) is different, the cooling rate of the billet in the melting and cooling after casting is the diameter of the billet, the cooling condition after casting, the solution It is appropriately selected depending on the aging treatment conditions, the aging treatment conditions and the like. Further, by appropriately adjusting the billet diameter, the cooling condition after casting, the solution treatment condition, the aging treatment condition, etc., the electrical conductivity of the copper alloy seamless pipe (1) for the heat transfer pipe of the present invention can be expressed by the formula ( 2), preferably adjusted to satisfy the formula (2a), and the electrical conductivity of the copper alloy seamless pipe (2) for heat transfer tubes of the present invention is the formula (3), preferably the formula (3a) Adjust to meet.

  The copper alloy seamless pipe for a heat transfer tube of the present invention is wound into a coil shape as a heat transfer tube for a heat exchanger, and used for production of a heat exchanger (cross fin tube type heat exchanger). The cross fin tube heat exchanger is configured by integrally assembling an air-side aluminum fin and a refrigerant-side heat transfer tube.

  The cross fin tube type heat exchanger first produces aluminum plate fins in which a plurality of predetermined assembly holes are formed by pressing or the like, and then stacks the obtained aluminum plate fins, Insert the copper alloy seamless pipe (1) for heat transfer pipe of the present invention or the copper alloy seamless pipe (2) for heat transfer pipe of the present invention into which the regular cut and hairpin are bent, and then connect the seamless pipe It is manufactured by brazing a U-bend tube to the end of the seamless tube opposite to the side where the hairpin is bent and fixed to the aluminum plate fin.

  EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this is only an illustration and does not restrict | limit this invention.

(Examples and Comparative Examples)
<Copper alloy seamless pipe for heat transfer tubes>
(Melting, casting and cooling)
Billets having an outer diameter of 254 mm containing the chemical components shown in Table 1 were cast by semi-continuous casting, and then cooled. The amount of billet cooling water at this time was as follows. In Table 1, the balance is Cu and inevitable impurities.
Cooling condition A: Cooling water amount 1,000 L / min Cooling condition B: Cooling water amount 600 L / min (hot extrusion and cooling)
The billet obtained as described above was heated by holding at 950 ° C. (± 25 ° C.) for 10 minutes or more in a continuous heating furnace, and then at an extrusion temperature of 950 ° C., an outer diameter of 81 mm × wall thickness of 8 mm. The tube was extruded, and immediately after extrusion, it was poured into water and cooled to obtain a hot extruded tube. At this time, the solution treatment was also performed.
A sample for measuring electrical conductivity (sample 1) was sampled from the head and tail of the obtained hot extruded tube.
(Cold processing)
The hot extruded elementless tube obtained as described above was cold-rolled and cold drawn to obtain a seamless elementless tube having an outer diameter of 9.52 mm and a wall thickness of 0.8 mm.
(Aging treatment)
The seamless element tube obtained as described above was heated in a non-oxidizing atmosphere at 550 ° C. for 60 minutes in a batch furnace to obtain a copper alloy seamless tube for a heat transfer tube.
Sample 2 was sampled from the obtained copper alloy seamless pipe for heat transfer tubes for electrical conductivity measurement. Samples 3 and 4 were sampled for the heating-water cooling test.

<Heating-water cooling test>
The heating-water cooling test at 950 ° C. for 10 minutes is a test in which a copper alloy seamless tube to be tested is heated at 950 ° C. ± 25 ° C. for 10 minutes and then water-cooled. The test object is charged into an electric furnace set at ± 25 ° C, and after the furnace temperature returns to 950 ° C, it is held at 950 ° C ± 25 ° C for 10 minutes, and then immediately cooled with water from 950 ° C. Is done. Then, the electrical conductivity (% IACS) of the test object after the heating-water cooling test at 950 ° C. for 10 minutes is measured to obtain ρ3.
The heating-water cooling test at 550 ° C. for 60 minutes means that the copper alloy seamless tube to be tested is heated at 950 ° C. for 10 minutes and then water-cooled, and then at 550 ° C. ± 10 ° C. for 60 minutes. First, the test object was heated at 950 ° C. ± 25 ° C. for 10 minutes and then immediately cooled with water from 950 ° C. in the same manner as the heating-water cooling test at 950 ° C. for 10 minutes. Then, the test object subjected to heating and water cooling at 950 ° C. for 10 minutes is placed in a salt bath furnace, held at 550 ° C. ± 10 ° C. for 60 minutes, and then immediately cooled with water. Then, the electrical conductivity (% IACS) of the test object after the heating-water cooling test at 550 ° C. ± 10 ° C. for 60 minutes is measured to obtain ρ4.

(Heating-water cooling test 1) 950 ° C. ± 25 ° C. × 10 minutes First, sample 3 was charged into an electric furnace set at 950 ± 25 ° C. in a nitrogen gas atmosphere, and the temperature in the furnace returned to 950 ° C. After that, it was kept at 950 ± 25 ° C. for 10 minutes, and then immediately cooled with water from 950 ° C. to perform a heating-water cooling test 1.

(Heating-water cooling test 2) 550 ° C. ± 10 ° C. × 60 minutes First, sample 4 was heated and cooled in water at 950 ± 25 ° C. for 10 minutes in the same manner as in heating-water cooling test 1, and then heated-water cooling. Sample 4 that had been heated and cooled in the same manner as in Test 1 was placed in a salt bath furnace, held at 550 ° C. ± 10 ° C. for 60 minutes, and then immediately cooled with water to perform a heating-water cooling test 2. .

<Evaluation>
(mechanical nature)
Torch brazing was carried out using a brazing material (JIS Z3264 BCuP-2) and an oxygen-propane mixed gas to prepare a sample for measuring pressure resistance after brazing. At this time, brazing was performed until the brazing material flowed into the joint. Cooling was performed by air cooling, and after cooling, a burst test was performed by water pressure, the tensile strength was estimated from the fracture strength using the following formula * 1, and the mechanical properties (tensile strength and elongation) before and after brazing were evaluated.
Mechanical properties before brazing were evaluated by a tensile test, and tensile strength and elongation were measured according to JIS Z2241. The results are shown in Table 3.
<Formula * 1> KHK formula: bursting pressure = 2 × tensile strength × wall thickness / (outer diameter−0.8 × wall thickness)
(Electrical conductivity)
The electrical conductivity was measured by a method based on JIS H0505, that is, a four-terminal method, and the electric resistance was measured and expressed as a percentage by dividing by 0.15328.
(Intermediate temperature brittleness test)
The copper alloy seamless tube was subjected to a tensile test at 350 ° C. at a strain rate of 10 ⁻⁴ . A sample having an elongation (δ) of 30% or more was regarded as acceptable.
(Thermal fatigue test)
In a constant temperature bath at 100 ° C., a copper alloy seamless pipe was subjected to a repeated internal pressure of 0 to 15 MPa 100,000 times to conduct a thermal fatigue test. Those in which no cracks occurred during the test were considered acceptable.

Claims (3)

It is a copper alloy seamless pipe for heat transfer tubes obtained by processing a copper alloy,
This copper alloy contains Sn, 0.01-0.08 mass% Zr, and 0.004-0.04 mass% P, and consists of the remainder Cu and inevitable impurities, The content of Sn and Zr of the following formula (1):
(1) 0.4 ≦ A + 2B ≦ 0.85
(In the formula, A represents the Sn content (mass%), and B represents the Zr content (mass%).)
The filling,
The electrical conductivity of the copper alloy seamless pipe for heat transfer tube is represented by the following formula (2):
(2) ρ2−ρ1 ≧ 0.3 (% IACS)
(In the formula, ρ1 indicates the electric conductivity after solution treatment (% IACS), and ρ2 indicates the electric conductivity after aging treatment (% IACS).)
Meeting,
Copper alloy seamless pipe for heat transfer tubes. It is a copper alloy seamless pipe for heat transfer tubes obtained by processing a copper alloy,
This copper alloy contains Sn, 0.01-0.08 mass% Zr, and 0.004-0.04 mass% P, and consists of the remainder Cu and inevitable impurities, The content of Sn and Zr of the following formula (1):
(1) 0.4 ≦ A + 2B ≦ 0.85
(In the formula, A represents the Sn content (mass%), and B represents the Zr content (mass%).)
The filling,
The electrical conductivity of the copper alloy seamless pipe for heat transfer tube is represented by the following formula (3):
(3) ρ4-ρ3 ≧ 0.3 (% IACS)
(In the formula, ρ3 indicates the electric conductivity after heating-water cooling test at 950 ° C. for 10 minutes (% IACS), and ρ4 indicates the electric conductivity after heating-water cooling test at 550 ° C. for 60 minutes (% IACS). Point to.)
Meeting,
Copper alloy seamless pipe for heat transfer tubes.   The said copper alloy contains 0.0005-0.0010 mass% S and 0.0002-0.0020 mass% H further, The any one of Claim 1 or 2 characterized by the above-mentioned. Copper alloy seamless pipe for heat transfer tubes as described.