JP2014043622A - High-strength copper alloy tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy tube excellent in strength by controlling precipitates and crystal grain sizes, as well as having good processability.SOLUTION: A copper alloy tube has an alloy content consisting of Co:0.16 mass% to 0.30 mass%, P:0.02 mass% to 0.1 mass% and the balance Cu with inevitable impurities, and has an average crystal grain size of 5 μm to 40 μm, an average diameter of precipitates of 3 nm to 10 nm, and a number density of the precipitates having a diameter of 1 nm to 10 nm, of 5,000/μmor more.

Description

The present invention relates to a high-strength copper alloy tube used for piping of a heat exchanger.

In general, copper is often used for piping and the like of heat exchangers because it is excellent in malleability and ductility, and is particularly excellent in thermal conductivity.
For example, in a heat exchanger of an air conditioner, first, a copper alloy straight pipe is passed through a through hole of an aluminum fin, and the copper alloy straight pipe is expanded with a jig, thereby bringing the copper alloy straight pipe and the aluminum fin into close contact with each other. Next, the open end of the copper alloy tube is expanded, a U-shaped copper alloy tube bent into a U-shape is inserted into this expanded portion, and the U-shaped copper alloy tube is brazed to the expanded portion with phosphorous copper brazing. To do.
For this reason, copper alloy straight pipes used in heat exchangers and copper alloy pipes that are U-shaped copper alloy pipes have good workability such as bending, pipe expansion / flaring, contraction / drawing, etc. Is required.

  In heat exchangers, the refrigerant used changes due to measures against environmental problems such as ozone depletion, and more pressure is applied to copper alloy tubes, and with the rise in copper bullion due to global competition for resources. Due to the increasing demand for reducing the amount of copper used due to the thinning of copper alloy pipes, copper alloy pipes with high fracture pressure resistance have been developed. As such a copper alloy tube excellent in breakdown pressure, a copper alloy tube made of a precipitation-strengthened Cu—Co—P alloy described in Patent Document 1 and Patent Document 2 is known.

  Furthermore, in addition to workability such as bending work on the copper alloy tube that is the pipe in the heat exchanger, from the necessity of joining with aluminum fins to demonstrate its function when completed as a heat exchanger, Brazing properties, proof stress after brazing heating and fatigue strength are also required. A solid solution strengthened Cu—Sn—P based alloy described in Patent Document 3 is known as a copper alloy having excellent brazing properties, proof stress after brazing heating and fatigue strength.

Japanese Patent No. 3414294 Japanese Patent No. 4228166 Japanese Patent No. 3794971

  In recent years, the demand for thinner copper alloy tubes used in heat exchangers has become more severe, and higher strength is required for copper alloy tubes. In the conventional Cu—Co—P-based alloy, for example, as in the invention according to Patent Document 1, high strength has been achieved by regulating the oxygen content. Further, as in the invention according to Patent Document 2, increasing the strength has been promoted by controlling the crystal grain size and the precipitate state.

However, in the conventional method of regulating the oxygen content by producing a molten low oxygen copper, the number of steps increases and the cost also increases. In addition, in conventional manufacturing methods that go through processes such as hot working, cold working, and annealing, it is possible to make the precipitate finer if the annealing temperature is low, but the crystal grain size is controlled because recrystallization does not occur. Can not do it. On the other hand, if the annealing temperature is high in the production method, the crystal grain size can be controlled by recrystallization, but the precipitates become too large.
As described above, in the conventional Cu—Co—P-based alloy, the precipitate and the crystal grain size change at the same time depending on the annealing conditions, and thus there is a limit to simultaneously control the crystal grain size and the precipitate. As a result, the copper alloy tube used in the conventional heat exchanger was not satisfactory in increasing the strength.

  Furthermore, in the conventional Cu-Sn-P alloy, the crystal grain size is controlled by the hot extrusion and the cooling rate after hot extrusion as in the invention according to Patent Document 3, and the manufacturing process is likely to be complicated and thin. It was difficult to control. As a result, the copper alloy tube used in the conventional heat exchanger was not satisfactory in increasing the strength.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a copper alloy tube having excellent workability as well as excellent strength by controlling the average crystal grain size and precipitates, respectively. .

The high-strength copper alloy tube according to the present invention contains Co: 0.16% by mass to 0.30% by mass, P: 0.02% by mass to 0.1% by mass, with the balance being Cu and inevitable An alloy component composed of impurities, an average crystal grain size of 5 μm or more and 40 μm or less, an average diameter of precipitates of 3 nm or more and 10 nm or less, and a number density of 5000 precipitates having a diameter of 1 nm or more and 10 nm or less / Μm ³ or more.

With the above structure, the high-strength copper alloy tube controls the amount of each element to a predetermined amount, and has an average crystal grain size, an average diameter of precipitates, and a number density of precipitates with a predetermined diameter of 5000 / By controlling to μm ³ or more, it is possible to obtain excellent workability as well as excellent strength.

  The high-strength copper alloy tube according to the present invention is the high-strength copper alloy tube, and the components include Ni: 0.005% by mass to 0.10% by mass, Zn: 0.005% by mass to 1 0.0 mass% or less and Sn: 0.05 mass% or more and 1.0 mass% or less are further contained.

  By further including at least one of Ni, Zn, and Sn in the above configuration, excellent corrosion resistance can be obtained.

  Furthermore, the high-strength copper alloy tube according to the present invention is the high-strength copper alloy tube, and the component includes at least one selected from Fe, Mn, Mg, Cr, Ti, Zr, and Ag. Further, the total amount is less than 0.10% by mass.

  In the said structure, it contains further 1 or more types selected from Fe, Mn, Mg, Cr, Ti, Zr, and Ag, and the total amount is less than 0.10 mass%, copper It is possible to improve the strength and corrosion resistance of the alloy tube.

  The present invention has been made in view of the above problems, and a copper alloy tube having excellent workability and excellent workability can be obtained by controlling the average crystal grain size and precipitates, respectively.

A high-strength copper alloy tube according to the present invention will be described in detail based on an embodiment of the present invention. By setting the elemental composition, the average crystal grain size, the average diameter of the precipitates, and the number density of the precipitates described below, the high-strength copper alloy tube has excellent tensile strength.
The reasons for limiting these components and the reasons for defining the average crystal grain size, the average diameter of the precipitates, and the number density of the precipitates will be described.

<Alloy components>
The high-strength copper alloy tube according to the present invention contains a predetermined amount of Co and P, with the balance being Cu and inevitable impurities.

(Co: 0.16 mass% or more and 0.30 mass% or less)
Co is an effective element for improving the strength and workability of the copper alloy tube. Further, when Co contains Sn as a selective component of the copper alloy tube, fine phosphide precipitates containing Sn are precipitated in the copper alloy tube structure, thereby further improving the strength and workability of the copper alloy tube. It is an effective element for improving.

The Co content is 0.16 mass% or more and 0.30 mass% or less. If the Co content is less than 0.16% by mass, coarse crystals are generated in the copper alloy tube structure, and the strength of the copper alloy tube is insufficient. Further, when Sn is contained as a selective component of the copper alloy tube, the amount of the phosphide precipitate is small, and it is difficult to improve the strength and workability. On the other hand, if the Co content exceeds 0.30% by mass, cracks occur during hot extrusion, and the workability of the manufactured copper alloy tube is lowered.
More preferably, it is 0.18 mass% or more and 0.25 mass% or less.

(P: 0.02 mass% to 0.1 mass%)
P is added to deoxidize the copper alloy.
Content of P shall be 0.02 mass% or more and 0.1 mass% or less. If the P content is less than 0.02 mass%, coarse crystals are generated in the copper alloy tube structure, and the strength of the copper alloy tube is insufficient. On the other hand, when the content of P exceeds 0.1% by mass, cracks occur during hot extrusion, and the workability of the manufactured copper alloy tube is lowered.
More preferably, it is 0.03 mass% or more and 0.08 mass% or less.

(Balance: Cu and inevitable impurities)
In addition to the above, the copper alloy component is composed of Cu and inevitable impurities. Inevitable impurities include, for example, Al, Be, V, Nb, Mo, W, and the like, which are contained in metal and intermediate alloys. These inevitable impurity elements are liable to produce coarse crystallized products and precipitates, so that the content is preferably as small as possible.
Al, Be, V, Nb, Mo, W, etc. within the generally known range do not impair the processing characteristics and other characteristics of the Cu alloy according to the present invention.

(Average crystal grain size: 5 μm or more and 40 μm or less)
In the present invention, as the average crystal grain size is smaller in the copper alloy tube, a copper alloy tube having a high balance of strength and excellent bending workability can be obtained. For this reason, the average crystal grain size including the crystal containing Co effective in improving the strength is controlled to 5 μm or more and 40 μm or less by the solution treatment described later.

  When the average crystal grain size exceeds 40 μm, the amount of strengthening due to crystal grain refinement becomes small, and the strength tends to be insufficient. On the other hand, if the average crystal grain size exceeds 40 μm, the workability deteriorates. There is no lower limit for the average grain size, but 5 μm is the lower limit for manufacturing reasons. The control method will be described later.

  For the average crystal grain size, three points were selected at the center in the thickness direction of the cut surface obtained by cutting the copper alloy tube in a plane parallel to the longitudinal direction of the tube, and the crystal grain size was determined by the comparison method described in JIS H 0501. The particle diameter is measured, and an average value is calculated from the measured value.

(Average diameter of precipitate: 3 nm or more and 10 nm or less)
In the present invention, not only the average crystal grain size is controlled within the specified range, but also by controlling the average diameter of the precipitates, a copper alloy having a high strength and excellent bending workability in a well-balanced manner. Can be obtained. For this reason, the average diameter of precipitates is controlled to 3 nm or more and 10 nm or less by solution treatment and annealing treatment described later.

  When the average diameter of the precipitates exceeds 10 nm, the distance between the particles of the precipitates increases, so that the precipitation strengthening amount decreases and the strength of the copper alloy tube tends to be insufficient. On the other hand, if the average diameter of the precipitates is less than 3 nm, the bond is cut by the transition, so that the precipitation strengthening amount becomes small and the strength of the copper alloy tube tends to be insufficient. The control method will be described later.

  The average diameter of the precipitates was observed at a magnification of 100,000 times using a transmission electron microscope (TEM), and the precipitates observed in a range of 500 nm × 500 nm under a film thickness of 100 nm were measured for each precipitate. After measuring the diameter, the average value is calculated from the diameter of each precipitate.

(Number density of precipitates: 5000 / μm ³ or more)
In the present invention, by controlling the number density of precipitates in addition to controlling the average crystal grain size and the average diameter of precipitates, a copper alloy having a higher balance of strength and excellent bending workability is obtained. be able to. For this reason, the number density of precipitates having a diameter of 1 nm or more and 10 nm or less is controlled to 5000 / μm ³ or more by solution treatment and annealing treatment described later.

When the number density of precipitates having a diameter of 1 nm or more and 10 nm or less is less than 5000 / μm ³ , the precipitation strengthening amount becomes small and the strength tends to be insufficient. Further, although there is no upper limit to the number density of precipitates, the limit is 100,000 pieces / μm ^{3 in} the component range of the alloy according to the present embodiment. The control method will be described later.

  The number density of precipitates is observed with a transmission electron microscope (TEM) at a magnification of 100,000 times, and the precipitates having a diameter of 1 nm or more and 10 nm or less are observed in a range of 500 nm × 500 nm under a film thickness of 100 nm. It is calculated | required by measuring a number about and calculating.

  The high-strength copper alloy tube of the present invention may contain a predetermined amount or less selected from Ni, Sn, or Zn as a selective component in addition to the alloy component.

(Ni: 0.005 mass% or more and 0.10 mass% or less)
Ni is an element that forms a phosphide with P and increases the strength by precipitation strengthening.
The content of Ni is preferably 0.005% by mass or more and 0.10% by mass or less. In order to effectively exhibit the above-described effects due to Ni, it is preferable to contain 0.005% by mass or more. However, since an intensity | strength falls on the contrary when it contains excessively, 0.10 mass% or less is preferable.
More preferably, it is 0.01 mass% or more and 0.05 mass% or less.

(Zn: 0.005 mass% or more and 1.0 mass% or less)
Zn is an effective element for improving corrosion resistance and suppressing corrosion.
The content of Zn is preferably 0.005% by mass or more and 1.0% by mass or less. In order to exhibit the said effect by Zn effectively, it is preferable to contain 0.005 mass% or more. However, if it is excessively contained, the corrosion resistance is lowered, so 1.0% by mass or less is preferable.
More preferably, it is 0.01 mass% or more and 0.5 mass% or less.

(Sn: 0.05 mass% or more and 1.0 mass% or less)
Sn is effective in improving the corrosion resistance of the copper alloy tube in order to improve the strength by solid solution hardening and to suppress the coarsening of precipitates.
The content of Sn is preferably 0.05% by mass or more and 1.0% by mass or less. In order to effectively exhibit the effect of Sn, it is preferable to contain 0.05% by mass or more. When the Sn content is less than 0.05% by mass, these effects are insufficient. On the other hand, if the Sn content exceeds 1.0% by mass, the hot deformation resistance in the hot extrusion process is increased and the productivity is lowered.
More preferably, the content is 0.1% by mass or more and 0.8% by mass or less.

  Furthermore, the high-strength copper alloy tube of the present invention includes, as a selective component in addition to the alloy component, one or more selected from Fe, Mn, Mg, Cr, Ti, Zr, and Ag, less than a predetermined amount. You may contain.

(Fe, Mn, Mg, Cr, Ti, Zr, Ag: total less than 0.10% by mass)
Fe, Mn, Mg, Cr, Ti, Zr, and Ag are effective for improving the strength and corrosion resistance of the copper alloy tube and improving the bending workability by refining the crystals and precipitates. is there. In order to exhibit these effects effectively, it is preferable to contain less than 0.10 mass% in total.
When the total content of these elements is 0.10% by mass or more, the extrusion pressure increases at the time of hot extrusion. Therefore, hot extrusion pressure is used to perform hot extrusion at the same extrusion pressure as those not containing these elements. It is necessary to raise. As a result, surface oxidation of the extruded material increases, resulting in frequent surface defects in the copper alloy tube. For this reason, it is impossible to improve the corrosion resistance expected of the thinned heat transfer tube, which is one of the intended uses of the present invention.
Therefore, the total content of these elements is preferably less than 0.10% by mass.

<Manufacturing method of copper alloy>
Next, a method for producing a copper alloy tube according to the present invention will be described.
The manufacturing process itself of the copper alloy in the present invention is basically the same as the manufacturing process of the conventional copper alloy tube. That is, the manufacturing process of the copper alloy tube according to the present invention includes a billet manufacturing process, a homogenization heat treatment process, a hot extrusion process, a rolling process, a rough drawing process, a solution treatment process, and an annealing process. Consists of.

  First, the raw electrolytic copper is dissolved under the charcoal coating, after the copper is dissolved, a predetermined amount of Co is added, and further a copper alloy containing about 15% by mass of P is added for deoxidation, After adjusting the components, a billet of a predetermined size is produced by semi-continuous casting (billet production process). Next, in order to improve segregation, the billet is heated to 750 to 950 ° C. and held for about 0.1 to 2 hours as necessary to perform a homogenization heat treatment (homogenization heat treatment step). Then, a billet is made into an extrusion element pipe by hot extrusion at 750-850 ° C (hot extrusion process). The extruded element tube is rolled into a rolled element tube (rolling process), and a drawn tube (element pipe) having a predetermined size is manufactured by a drawing process (rough drawing process). By setting the processing rate in the rolling process to 92% or less and the processing rate in the rough drawing process to 35% or less, product defects during each processing can be reduced.

  Next, a solution treatment step and an annealing step that affect the average crystal grain size of the copper alloy composition and the average diameter, number density, and volume fraction of the precipitate are performed under the following conditions.

(Solution treatment process)
The solution treatment is performed at 750 ° C. or more and 900 ° C. or less, and heating is performed for 10 to 300 seconds.
When the solution treatment temperature is a low temperature of less than 750 ° C., a coarse precipitate is generated at the time of the solution treatment, and therefore the average diameter of the precipitate tends to be larger than 10 nm. In addition, since the precipitates generated in the subsequent annealing step are reduced, the number density of the precipitates having a diameter of 1 nm or more and 10 nm or less tends to be less than 5000 / μm ³ . As a result, the strength of the copper alloy tube tends to be insufficient. On the other hand, when the solution treatment temperature is a high temperature exceeding 900 ° C., the average crystal grain size tends to be larger than 40 μm. As a result, the corrosion resistance of the copper alloy tube tends to decrease.
Under the above conditions, the average crystal grain size is controlled to be 40 μm or less, which is the upper limit, and the average diameter of the precipitate is controlled to be 10 nm or less, which is the upper limit. At the same time, the number of precipitates having a diameter of 1 nm or more and 10 nm or less is controlled so that the number of precipitates generated in the subsequent annealing step is 5000 / μm ³ or more which is the lower limit.
As described above, the solution treatment is an important process for effectively controlling either the average crystal grain size or the precipitates which are easily changed at the same time.

(Annealing process)
The annealing treatment is performed at a temperature exceeding 450 ° C. and less than 700 ° C., and heating is performed for 5 minutes to 1 hour. When the annealing temperature is a low temperature of 450 ° C. or less, the average diameter of the precipitates becomes too fine as less than 3 nm, and the strength of the copper alloy tube is insufficient. On the other hand, when the annealing temperature is 700 ° C. or higher, the average diameter of the precipitates is larger than 10 nm, and the number density of the precipitates having a diameter of 1 nm or more and 10 nm or less is reduced to less than 5000 / μm ^3. The strength of the alloy tube is insufficient.
In the present invention, by performing the treatment on the drawing tube after the solution treatment, the average crystal grain size is controlled to be within the specified value, and the average diameter of the precipitate is to be within the specified value. And the number density of precipitates having a diameter of 1 nm to 10 nm is controlled to 5000 / μm ³ or more.
As described above, the annealing treatment is an important process for effectively controlling either the average crystal grain size or the precipitates which are easily changed by being combined with the solution treatment.

As mentioned above, although the form for implementing this invention has been described, according to this invention, the high intensity | strength copper alloy pipe | tube which is excellent in intensity | strength and has favorable workability and a clear crack is not observed at the time of a bending process is obtained. . For this reason, in the heat exchanger, by using the high-strength copper alloy tube according to the present invention, it is possible to expand and flare while reducing the amount of copper used, and a heat exchanger having a pipe bent into a hairpin shape. It becomes possible to manufacture efficiently. In particular, the high-strength copper alloy tube according to the present invention is suitable for use in a small heat exchanger having severe bending requirements. Furthermore, since the high-strength copper alloy tube according to the present invention is excellent in corrosion resistance, an effect of extending the life of the heat exchanger and the air conditioner is also obtained.
Note that the present invention is not limited to such an embodiment, and can be appropriately changed without departing from the technical idea of the present invention.

Hereinafter, Examples 1 to 3 in which the effects of the present invention have been confirmed will be specifically described in comparison with Comparative Examples that do not satisfy the requirements of the present invention.
In addition, [Example 1] is Nos. 1 to 4, 17, 18 in Table 1, [Example 2] is Nos. 5 to 10 in Table 1, and [Example 3] is No. 1 in Table 1. It corresponds to 11-16.

(Sample material)
The sample material was produced by the following steps.
First, after adding Co to a molten metal made of electrolytic copper, a cast ingot having a diameter of 300 mm and a length of 3000 mm at a casting temperature of 1200 ° C. using a Cu-P alloy added and deoxidized. Continuous casting. A billet having a length of 475 mm was cut out from the ingot, and as a homogenization treatment, the billet was heated to 900 ° C., held for 1.5 hours, and then cooled.

Next, the homogenized billet was heated to 830 ° C. and held for 3 minutes, and then extruded to produce an extruded element tube having an outer diameter of 94 mm and a wall thickness of 10 mm. The extruded element tube was rolled to an outer diameter of 38 mm and a wall thickness of 2.1 mm, and further drawn at a processing rate of 35% to produce a smooth tube having an outer diameter of 9.52 mm and a wall thickness of 0.8 mm. The smooth tube was annealed in the annealing furnace under the conditions shown in Table 1 to obtain a test material.
A predetermined amount of sample is taken from the test material, and the composition is analyzed and shown in Table 1. In addition, the average crystal grain size, the average diameter, the number density, and the volume fraction of the precipitates were measured by the following procedure, and the results are shown in Table 1.

(Average crystal grain size measurement)
The average crystal grain size was calculated by the following method.
First, after cutting a copper alloy tube along a plane parallel to the longitudinal direction of the tube, the cross section was polished to obtain an observation surface. Next, this observation surface was observed with an optical microscope, and three central portions in the thickness direction of the copper alloy tube were arbitrarily selected. Then, the crystal grain size was measured by a comparative method described in JIS H 0501, and the average crystal grain size was calculated as the average value of the measured crystal grain sizes.

(Precipitate average diameter measurement)
The average diameter of the precipitate was calculated by the following method.
First, observation was performed at a magnification of 100,000 times using a transmission electron microscope (TEM, manufactured by JEOL). Next, the diameter of all the precipitates was measured with an image analysis software Image Pro plus (manufactured by Nippon Rover Co., Ltd.) for the precipitates observed in the range of 500 nm × 500 nm under a film thickness of 100 nm. And the average diameter of the deposit was computed as an average value of the diameter measured from each deposit.

(Precipitate number density measurement)
The number density of precipitates was calculated by the following procedure.
First, observation was performed at a magnification of 100,000 times using a transmission electron microscope (TEM, manufactured by JEOL). Next, the number of precipitates having a diameter of 1 nm or more and 10 nm or less was measured by image analysis software Image Pro plus (manufactured by Nippon Rover) for the precipitates observed in the range of 500 nm × 500 nm under a film thickness of 100 nm. Then, the number of precipitates per 1 μm ³ was calculated as the precipitate number density by calculation for the precipitates having a diameter of 1 nm to 10 nm. The ten decimal places of the calculated number of precipitates are rounded off and listed in Table 1.

  In the present application, the diameters of precipitates measured by image analysis software or the like are all calculated as equivalent to yen. In other words, since the cross-sectional shape of the precipitate is not a clean circle, the diameter of the precipitate in the present application is defined so that the diameter of the precipitate can be defined even when the cross-sectional shape of the precipitate is irregular. The diameter is equivalent to the equivalent of a circle when converted into a perfect circle with the same area.

(Precipitation volume fraction)
As with the average diameter of precipitates and the number density of precipitates, the precipitate volume fraction can be an index for obtaining a copper alloy having a high balance of strength and excellent bending workability.
The precipitation volume fraction Vf described in Table 1 was determined by the following equation using the average diameter 2r and the number density N of the precipitates.
Vf = 4 / 3πr ³ × N

  Next, tensile strength, bending workability, and stress corrosion cracking were measured by the following procedures using the test materials. The results are shown in Table 1.

(Tensile strength evaluation test)
The tensile strength in the longitudinal direction of the tube was determined by cutting the test piece from the longitudinal direction after cutting and flattening the copper alloy tube produced in the longitudinal direction by making a cut in the longitudinal direction of the tube, and removing a tensile test piece having a length of 290 mm and a width of 10 mm. The specimen was prepared, and the tensile strength σL and elongation in the longitudinal direction of the pipe were measured with an Instron 5566 type precision universal testing machine. The tensile strength σL was determined to be acceptable when it was 270 MPa or more.
Further, the tensile strength in the circumferential direction of this tensile test piece was also measured and found to be comparable (not shown in Table 1).

(Evaluation test for bending workability)
Simulating the heat transfer section of the heat exchanger, bending the specimens (smooth tubes) produced 10 times for each of the examples and comparative examples into a U shape with a pitch of 40 mm and a U shape with a pitch of 30 mm It was processed into. At this time, the occurrence of cracks and cracks in the bent portion of the smooth tube was visually inspected, and all the ten pieces that could be bent without cracks and cracks were evaluated as having good bending workability (◯). In addition, there are no cracks or cracks in all of the ten pieces, but wrinkles are generated, the bending radius is smaller, and if the bending conditions are strict, the bending and cracking may occur. The property was evaluated as being inferior (Δ). Furthermore, the bending workability was evaluated as poor (x) when even one crack or crack occurred among the 10 bent.

(Evaluation test for stress corrosion cracking)
A test piece was cut out from the specimen, and a stress corrosion cracking test was performed according to the Thompson method (Materials Research & Standards (1961) 1081). That is, 14% by mass of ammonia water was added and exposed to a desiccator filled with saturated vapor at a temperature of 40 ° C., and the time until the test piece broke was measured. A product having a life span of 40 hours or longer until breakage was evaluated as good (◯).

[Example 1]
From the results shown in Table 1, No. 1 to No. 4, No. 17, and No. 18 are compared with No. 19 to No. 22 and No. 26 to No. 32 in terms of tensile strength and bending. It has been found that the physical properties are excellent in both measurement properties and stress corrosion cracking measurement items. These exhibit characteristics superior to those of the prior art when used in a small apparatus having many bent portions such as a heat exchanger.
Further, when No. 1, No. 17, and No. 18 in Table 1 are compared, since the solution treatment is the same, the average crystal grain size is about the same. However, it was found that the number density of precipitates was decreased by increasing the annealing temperature following this, and the average crystal grain size and the number density of precipitates could be individually controlled.

  No. 19 has a Co content of less than the lower limit, and No. 21 has a P content of less than the lower limit, so that the effect of crystal refining is small and the average crystal grain size exceeds 50 μm. became. For this reason, these were inferior in tensile strength.

  In No. 20, the Co content exceeded the upper limit value, and in No. 22, the P content exceeded the upper limit value.

No. 26 was not subjected to a solution treatment, and the annealing temperature was relatively low at 550 ° C., so no recrystallization occurred. As a result, bending workability was inferior.
No. 27 was not subjected to solution treatment, and the annealing temperature was 650 ° C., which was higher than that of No. 26. Therefore, recrystallization occurred and the average crystal grain size was within the specified range. However, since recrystallization and precipitation of the intermetallic compound occur simultaneously, the growth rate of the precipitate increases. As a result, the average diameter of the precipitate increases, and the average diameter of the precipitate exceeds the upper limit of the present invention. At the same time, the number density of the precipitates was below the lower limit of the present invention. As a result, the tensile strength was inferior.

In No. 28, since the solution treatment temperature was lowered to 700 ° C., the average crystal grain size was within the specified range. However, as the average diameter of the precipitates exceeded the upper limit of the present invention, the number density of the precipitates fell below the lower limit of the present invention. As a result, the tensile strength was inferior.
In No. 29, the solution treatment temperature was 600 ° C. lower than that of No. 12, and the solution treatment time was increased to 1800 seconds, so the average crystal grain size was within the specified range. However, as the average diameter of the precipitates exceeded the upper limit of the present invention, the number density of the precipitates fell below the lower limit of the present invention. As a result, the tensile strength was inferior.

  In No. 30, since the solution treatment temperature was as high as 950 ° C., the average crystal grain size greatly exceeded the upper limit of the present invention. As a result, bending workability was inferior.

In No. 31, since the annealing temperature was lowered to 450 ° C., the average crystal grain size and the number density of precipitates were within the specified range of the present invention. However, since the average diameter of the precipitate was too small, the tensile strength was inferior.
In No. 32, since the annealing temperature was increased to 700 ° C., the average diameter of the precipitate exceeded the upper limit of the present invention, and the number density of the precipitate was not more than the lower limit of the present invention. As a result, the tensile strength was inferior.

[Example 2]
As shown in Table 1, No. 5 to No. 10 are compared with No. 23 and No. 24 in their physical properties in any measurement items of tensile strength, bending workability, and stress corrosion cracking. The mechanical properties were found to be excellent. These exhibit characteristics superior to those of the prior art when used in a small apparatus having many bent portions such as a heat exchanger.
No. 5 is No.5. The amount of addition of 1 and Co and P was almost the same, but the amount of precipitation strengthening was increased by adding Ni, so the average crystal grain size was reduced. As a result, no. 5 is No.5. Compared with 24, the tensile strength is large.

No. 6 is No.6. No. 1 and the addition amounts of Co and P are almost the same, and the addition amount of Sn is close to the lower limit value. Same as 1.
No. 7 is No. 7. No. 6 and the addition amounts of Co and P are almost the same. Since the addition amount of Sn was increased more than No. 6, Compared with 6, excellent tensile strength.

No. No. 9 is No.9. Although the amount of addition of 1 and Co and P was almost the same, the average crystal grain size was reduced because Sn and Zn were added to enhance the solid solution. As a result, no. No. 9 is No.9. Compared with 1, the tensile strength is slightly superior.
No. 10 is No. No. 9 was added to increase the precipitation strengthening amount. No. 10 is No. Compared to 9, the tensile strength is slightly superior.

  No. 23 had an Sn content of 1.51%, which exceeded the upper limit of the present invention, and therefore, extrusion was not possible and productivity was inferior.

  No. 24 has a Zn content of 2.51%, which greatly exceeds the upper limit of the present invention, so the average crystal grain size, the average diameter of the precipitates, and the number density of the precipitates are within the specified range of the present invention. However, the corrosion resistance was poor.

[Example 3]
As shown in Table 1, it was found that No. 11 to No. 16 were superior in physical properties in bending workability and stress corrosion cracking compared with No. 25. It was also found that No. 11 to No. 16 satisfied the specified values of the present invention in terms of tensile strength and were excellent in physical properties. These exhibit characteristics superior to those of the prior art when used in a small apparatus having many bent portions such as a heat exchanger.

  No. 25 has a Cr content of 0.18%, which exceeds the upper limit, so the average crystal grain size, the average diameter of the precipitates, and the number density of the precipitates are within the specified range of the present invention, but bending The sex was inferior.

Claims (3)

Co: 0.16% by mass or more and 0.30% by mass or less,
P: 0.02% by mass or more and 0.1% by mass or less,
The balance has an alloy component consisting of Cu and inevitable impurities,
The average crystal grain size is 5 μm or more and 40 μm or less,
The average diameter of the precipitate is 3 nm or more and 10 nm or less, and
A high-strength copper alloy tube, wherein the number density of precipitates having a diameter of 1 nm or more and 10 nm or less is 5000 pieces / μm ³ or more. As the component,
Ni: 0.005 mass% or more and 0.10 mass% or less,
Zn: 0.005 mass% or more and 1.0 mass% or less, and
The high-strength copper alloy tube according to claim 1, further comprising at least one of Sn: 0.05% by mass and 1.0% by mass. As the component,
It further contains at least one selected from Fe, Mn, Mg, Cr, Ti, Zr, and Ag, and the total amount thereof is less than 0.10% by mass. The high-strength copper alloy pipe according to claim 2.