TWI490349B - Copper alloy seamless pipe - Google Patents

Description

Copper alloy jointless pipe

The present invention relates to a copper alloy seamless pipe used for a heat transfer tube or a refrigerant pipe for a heat exchanger for an air conditioner, a refrigerator, or the like.

In the heat transfer tubes or refrigerant pipes for air conditioner heat exchangers, refrigerators, etc., such as indoor air conditioners and box air conditioners, the jointless pipe is often used, and the strength, workability, and heat transfer are used. Phosphorus deacidified copper tube (JIS C1220T) with various physical properties and balance between material and processing cost.

In recent years, in such heat exchangers, it is necessary to make the seamless pipe thinner according to the requirements of weight reduction or cost reduction, and the conventional phosphorus deacidification copper pipe is difficult to be thinned due to low strength, and it is required to develop a replacement for it. Seamless joint made of copper alloy.

In the case of the seamless joint of the copper alloy, it is disclosed in the publication No. 2008/041777 (Patent Document 1) that the copper alloy is excellent in the workability, the strength is high, and the strength reduction due to brazing is small. Sewing tube.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: International Publication No. 2008/041777 (Application Patent Range)

According to Patent Document 1, it is possible to obtain a copper alloy seamless pipe having excellent workability, high strength, and low strength reduction due to brazing, but it is required to further improve performance. In particular, in the design of the compressive strength of a heat exchanger or the like, the thickness is determined based on the material strength of the heat-affected portion of the brazing, so that the heat strength caused by the brazing is less reduced, and the heat exchanger can be well maintained. In the case of the processability, the heat transfer tube and the refrigerant tube can be made thinner, and therefore, a copper alloy seamless tube having high strength and low strength reduction due to brazing is required.

Accordingly, the present invention is to provide a copper alloy seamless pipe having high strength and low strength reduction due to brazing.

The inventors of the present invention have found that in the copper alloy, a specific content is contained in a specific content, and the crystal grain size of the copper alloy and the size of the Zr-based precipitate are found in order to solve the problems in the prior art described above. When the distribution density is appropriate, a copper alloy seamless pipe having high strength and low strength reduction due to brazing can be obtained, and the present invention has been completed.

That is, the present invention (1) is a copper alloy seamless pipe which is obtained by processing a copper alloy, and is characterized in that the copper alloy contains one or more elements of Sn, Zn and Al, and 0.01 to 0.08. Zr of mass %, consisting of residual Cu and unavoidable impurities, and the content of Sn, Zn, Al and Zr in the copper alloy satisfies the following formula (1):

(1) 0.4≦A+2B≦0.85

(wherein, A represents the total content (% by mass) of Sn, Zn, and Al, and B represents the content (% by mass) of Zr), and the average crystal grain size of the copper alloy seamless pipe is 30 μm or less, and is 0.5 to 80 nm in size. The Zr-based precipitates are distributed at 10 to 600 / μm ² .

According to the present invention, it is possible to provide a copper alloy seamless pipe having high strength and low strength reduction due to brazing.

The copper alloy seamless pipe of the present invention is obtained by processing a copper alloy, characterized in that the copper alloy contains one or more elements of Sn, Zn and Al, and Zr of 0.01 to 0.08% by mass, and Part of Cu and inevitable impurities, the content of Sn, Zn, Al and Zr in the copper alloy satisfies the following formula (1):

(1) 0.4≦A+2B≦0.85

(wherein, A represents the total content (% by mass) of Sn, Zn, and Al, and B represents the content (% by mass) of Zr), and the average crystal grain size of the copper alloy seamless pipe is 30 μm or less, and is 0.5 to 80 nm in size. The Zr-based precipitates are distributed at 10 to 600 / μm ² .

The copper alloy in the copper alloy seamless pipe of the present invention contains one or more of Sn, Zn, and Al, and Zr of 0.01 to 0.08% by mass, and is composed of a residual portion of Cu and unavoidable impurities, and The content of Sn, Zn, Al and Zr in the copper alloy satisfies the following formula (1):

(1) 0.4≦A+2B≦0.85

(In the formula, A represents a copper alloy for a jointless tube in which the total content (% by mass) of Sn, Zn, and Al, and B represents the content (% by mass) of Zr).

In addition, the Sn alloy may contain only one of Sn, Zn, and Al, or may contain two or more of Sn, Zn, and Al. In addition, in the case of Sn, Zn, and Al, the copper alloy contains only one of Sn, Zn, and Al, and the A value includes the content of one element contained, and contains two or more of Sn, Zn, and Al. In the case of the case, the A value is the total content of the two or more elements contained.

In addition, the copper alloy may be a copper alloy containing Sn and substantially containing no Zn or Al, that is, a content of Sn of 0.01% by mass or more, a content of Zn, and a content of Al of less than 0.01% by mass. "a copper alloy containing Zn and substantially containing no Sn and Al, that is, a content of Zn of 0.01% by mass or more and a content of Sn and an Al content of less than 0.01% by mass" may also be "containing Al and substantially It does not contain Sn and Zn, that is, a copper alloy having a content of Al of 0.01% by mass or more and a content of Sn and a content of Zn of less than 0.01% by mass, or "containing Sn and Zn and substantially not containing Al" That is, a copper alloy in which the content of Sn and the content of Zn are both 0.01% by mass or more and the content of Al is less than 0.01% by mass, or "containing Sn and Al and substantially containing no Zn, that is, the content of Sn" And a copper alloy having a content of Al of 0.01% by mass or more and a content of Zn of less than 0.01% by mass, or "containing Zn and Al and substantially not containing Sn, that is, the content of Zn and the content of Al are both 0.01% by mass or more and the content of Sn is less than 0.01% by mass of the copper alloy, or "the content of Sn, the content of Zn, and the content of Al are 0.01. Copper alloy with a mass of more than 5%.

The copper alloy of the copper alloy jointless pipe of the present invention preferably further satisfies the following formula (2):

(2) 0.40≦A

(In the formula, A is synonymous with the above), and the copper alloy for the jointless tube having a Zr content of 0.06% by mass or less.

The copper alloy of the copper alloy seamless pipe according to the present invention contains any one or two or more elements of Zr and Sn, Zn, and Al as essential elements, and is composed of residual Cu and unavoidable impurities. Copper alloy.

In the copper alloy seamless pipe of the present invention, Sn, Zn, and Al have an effect of improving the strength of the copper alloy by solid solution strengthening and an effect of improving ductility at normal temperature. Moreover, the case of these elements is advantageous in terms of manufacturing because it can be alloyed at a lower temperature.

In the copper alloy seamless pipe of the present invention, Zr has an effect of increasing the strength of the copper alloy by precipitation strengthening. Further, Zr is an effect of reducing the strength reduction by suppressing the coarsening of crystal grains by remaining Zr precipitates without excessively increasing the brazing temperature.

In the copper alloy of the copper alloy jointless pipe of the present invention, the content of Zr is 0.01 to 0.08% by mass. 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, and the strength reduction by the brazing is large, and the solid solution strengthening by the combination of Sn, Zn, and Al is combined. The precipitation strengthening caused by Zr and the strengthening of the copper alloy are not sufficient. 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. For example, problems such as hairpin bending processing under severe bending conditions and reduction in workability of pipe end pipe expansion processing occur.

In the copper alloy of the copper alloy jointless pipe of the present invention, A+2B is 0.4 to 0.85, that is, the following formula (1) is satisfied:

(1) 0.4≦A+2B≦0.85.

When the content of Zr in the copper alloy is 0.08% by mass or less, if the total content of Sn, Zn, and Al is too large, work hardening is remarkable, workability, particularly cold drawing workability, is deteriorated, and it is necessary to add an intermediate annealing step. As a result of the increase in cost, it is impossible to ensure sufficient processing degree of cold working to obtain a fine and uniform precipitation state by aging precipitation. Therefore, it is necessary to set A+2B to 0.85 or less. In addition, by setting A+2B to 0.4 or more and the content of Zr to 0.01% by mass or more, the strength of the copper alloy seamless pipe can be kept to a minimum even when severe workability is required. On the other hand, if A+2B is less than 0.4, the strength of the copper alloy jointless pipe is insufficient.

In the copper alloy of the copper alloy jointless pipe of the present invention, it is preferred that the system A is 0.40 or more, that is, the following formula (2) is satisfied:

(2) 0.40≦A,

And the content of Zr is 0.06 mass% or less; the special system A is 0.43 or more, that is, the following formula (2a) is satisfied:

(2a) 0.43≦A,

Further, the content of Zr is 0.06 mass% or less. In the case of a copper alloy containing a precipitation strengthening element such as Zr as in the case of the copper alloy of the copper alloy seamless pipe of the present invention, the strength is improved by aging, and the ductility is lowered. In the copper alloy of the copper alloy seamless pipe according to the present invention, in order to suppress the workability which is caused by the decrease in ductility, the content of Zr is limited to 0.08% by mass, and when severe workability is required, for example, In order to maintain sufficient workability, etc., in the case where the shape of the inner surface groove which is difficult to machine is produced by the transfer processing, the shape of the inner surface groove which is difficult to process is required to be processed by the hairpin type bending process under severe bending conditions It is expected to actively add Sn, Zn, and Al. As described above, Sn, Zn, and Al have an effect of improving ductility at normal temperature, and when the content of Zr is 0.01 to 0.06 mass%, the content of Zr is set to 0.06 mass% or less, and Sn, Zn, and Al are used. When the total amount is 0.40% by mass or more, the effect of improving the workability can be achieved.

The content of P in the copper alloy of the copper alloy jointless pipe of the present invention is preferably 0.004 to 0.040% by mass, and particularly preferably 0.015 to 0.030% by mass. The copper alloy contains 0.004% by mass or more of the P element, and the deacidification in the display material is sufficient. In addition, when the content of P in the copper alloy is too large, the thermal conductivity of the copper alloy is lowered. Therefore, in the case of the heat transfer tube, the content of P in the copper alloy is preferably 0.040% by mass or less.

In the copper alloy seamless pipe of the present invention, the copper alloy has an average crystal grain size of 30 μm or less, and the Zr-based precipitate having a size of 0.5 to 80 nm has a distribution density of 10 to 600 / μm ² . The copper alloy jointless pipe of the present invention is a jointless pipe for brazing in the manufacture of a heat exchanger or the like. As such a brazing method, there can be mentioned brazing in the furnace and hard brazing in the furnace, and the seamless pipe for brazing can be exposed to the extreme temperature of 750 to 900 ° C for a maximum of 900 seconds. Between the brazing, since the fine Zr-based precipitates are re-solidified, the crystal grains of the copper alloy are coarsened, and the strength of the jointless tube is lowered by brazing.

Therefore, the copper alloy jointless pipe of the present invention has an average crystal grain size before brazing and a size and a distribution density of the Zr-based precipitates in an appropriate range, that is, the average crystal grain size of the copper alloy is 30 μm or less. Further, the distribution density of the Zr-based precipitates having a size of 0.5 to 80 nm is set to 10 to 600 / μm ² , and the strength reduction of the copper alloy seamless pipe caused by brazing can be suppressed. By dispersing the fine Zr-based precipitates and suppressing the movement of the crystal grain boundaries by the stopper effect, the effect of suppressing the coarsening of the crystal grains is obtained. The fine Zr-based precipitates are partially solid-melted during brazing heating, so that the plugging effect is reduced and the crystal grains are grown. However, the copper alloy jointless pipe of the present invention is heated by brazing before the Zr-based precipitates. The size and distribution density are set to a suitable range, and the reduction of the stopper effect caused by the brazing heating can be reduced. Therefore, the copper alloy seamless pipe of the present invention can maintain the fineness of the crystal grains even after being kept at a high temperature by brazing, and can maintain the dispersion state of the Zr-based precipitates contributing to the strength.

The copper alloy of the copper alloy seamless pipe of the present invention has an average crystal grain size of 30 μm or less. As described above, the copper alloy seamless pipe of the present invention is subjected to brazing, so that the average grain size of the copper alloy after the aging treatment and before the brazing is 30 μm or less. When the average crystal grain size of the copper alloy exceeds the above range, the distribution of the Zr-based precipitates can be appropriately adjusted to suppress the coarsening of the crystal grains, and since the original crystal grains are large, the crystal grain size after brazing is exceeded. Preferred range.

The Zr-based precipitate of the copper alloy of the copper alloy jointless pipe of the present invention is composed of a precipitate composed of Zr and Cu such as Cu ₃ Zr or CuZr, or Zr and Cu and one or more other metal elements. The precipitate.

In the copper alloy seamless pipe of the present invention, the size of the Zr-based precipitate which exhibits a stopper effect even after brazing heating is 0.5 to 80 nm. If the size of the Zr-based precipitate is less than the above range, it will be solidified and disappeared during brazing heating, or may be reduced to a level that does not contribute to the improvement of strength. When the size of the Zr-based precipitates exceeds the above range, the stoppering effect of the crystal grain boundary cannot be sufficiently obtained at the time of brazing heating.

In the copper alloy of the copper alloy seamless pipe according to the present invention, the Zr-based precipitate having a size of 0.5 to 80 nm has a distribution density of 10 to 600 / μm ² . When the distribution density of the above-mentioned Zr-based precipitates is less than the above range, the number of precipitates which sufficiently obtain the plugging effect of the crystal grain boundary is insufficient, and the crystal grains are coarsened during the brazing heating, so the strength after brazing reduce. In addition, even if the distribution density of the above-mentioned Zr-based precipitates exceeds the above range, it is not expected that the bolt stopper effect is further improved, and the workability is lowered, and the hairpin bending workability and the pipe end pipe workability are improved. reduce. Specifically, for the crystal grain boundary stopper effect, it is effective that the distribution density of the Zr-based precipitate having a size of 0.5 to 10 nm is 100 to 600 / μm ² .

In the copper alloy of the copper alloy seamless pipe according to the present invention, Zr-based precipitates having a size less than the above range or Zr-based precipitates having a size exceeding the above range may be present. In other words, in the copper alloy, even if there are Zr-based precipitates having a size smaller than the above range or Zr-based precipitates having a size exceeding the above range, the distribution density of the Zr-based precipitates having a size within the above range may be within the above range. .

In the copper alloy seamless pipe of the present invention, since the size and dispersion state of the Zr-based precipitates are appropriately adjusted, the strength reduction by the brazing is small. Specifically, the strength reduction ratio represented by the following formula (3) is preferably 5% or less after heating at 800 ° C for 30 seconds. After heating at 800 ° C for 30 seconds, the strength reduction rate is 5% or less, which is an index which can be made thinner than the former.

Strength reduction rate (%) = ((strength before brazing - strength after brazing) / strength before brazing) × 100 (3)

(In the formula (3), the strength is tensile strength (unit: MPa)).

Further, the tensile strength before brazing and after brazing is preferably 245 MPa or more.

Moreover, since the copper alloy seamless pipe of the present invention is appropriately sized by the contents of Sn, Zn, Al, and Zr, the workability is good.

As an example of the form of the copper alloy seamless pipe of the present invention, there are an inner smooth pipe (bearing pipe) in which an inner groove is not formed, and an inner grooved pipe which forms an inner groove.

A method of manufacturing a copper alloy seamless pipe according to the present invention will be described. A method for producing a copper alloy seamless pipe according to a first aspect of the present invention is a method for producing a seamless pipe when the jointless pipe is an inner surface smooth pipe. Moreover, the method for producing a copper alloy seamless pipe according to a second aspect of the present invention is a method of manufacturing a jointless pipe which is a grooved pipe on the inner surface.

In the method for manufacturing a copper alloy jointless pipe according to the first aspect of the present invention, the casting step, the hot extrusion step, the cold working step, and the aging treatment are sequentially performed, and the hot extrusion step and the aging treatment are not performed. The intermediate annealing treatment, the method of manufacturing the copper alloy seamless pipe having a total working degree of 90% or more in the cold working step.

In the method for producing a copper alloy seamless pipe according to the first aspect of the present invention, the casting step, the hot extrusion step, the cold working step, and the aging treatment are sequentially performed. In addition, the sequential operation is performed not immediately after the casting step, the cold extrusion step is performed immediately after the hot extrusion step, and the aging treatment is performed immediately after the cold working step, The hot extrusion step is performed after the casting step, the cold working step is performed after the hot extrusion step, and the aging treatment is performed after the cold working step.

Further, in the method for producing a copper alloy seamless pipe according to a second aspect of the present invention, the casting step, the hot extrusion step, the cold working step, the intermediate annealing treatment (A), the conversion processing step, and the aging treatment are sequentially performed. An intermediate annealing treatment is not performed between the hot extrusion step and the intermediate annealing treatment (A), and the total processing degree of the cold working step is 90% or more of a copper alloy seamless pipe manufacturing method.

A method for producing a copper alloy jointless pipe according to a second aspect of the present invention is the step of performing the casting step, the hot extrusion step, the cold working step, the intermediate annealing treatment (A), the conversion processing step, and This aging treatment. In addition, the sequential extrusion process is not performed immediately after the casting step, the cold working step is performed immediately after the hot extrusion step, and the intermediate annealing treatment (A) is performed immediately after the cold working step. The conversion processing step is performed immediately after the intermediate annealing treatment (A), and the aging treatment is performed immediately after the conversion processing step, and the hot extrusion step is performed after the casting step. Thereafter, the cold working step is performed, the intermediate annealing treatment (A) is performed after the cold working step, the conversion processing step is performed after the intermediate annealing treatment (A), and the aging treatment is performed after the conversion processing step.

The casting step from the casting step of the copper alloy seamless joint pipe manufacturing method according to the first aspect of the present invention to the cold working step, and the method of manufacturing the copper alloy seamless joint pipe according to the second aspect of the present invention to the cold working The steps are the same.

The method for producing a copper alloy jointless pipe according to a first aspect of the present invention and the method for producing a copper alloy seamless pipe according to a second aspect of the present invention are obtained by melting, casting, and obtaining according to a conventional method. The step of assigning a slab of the specified element to the specified content. In the casting step, for example, bare metal of copper and a bare metal of the copper alloy containing the element of the copper alloy jointless tube of the present invention or an alloy of the element and copper, so that the copper alloy of the present invention is not connected The content of the copper alloy in the seam tube is adjusted to the specified content, and the composition is adjusted. Next, the billet is cast using a high-frequency melting furnace or the like.

Since Zr is an active metal, the oxidative loss during melting is increased. Therefore, in the composition adjustment, it is necessary to consider the oxidative loss during the Zr melting.

Further, in the casting step, the fluidity of the melt is increased by blending P, so that the castability is increased, the occurrence of casting defects such as gas holes is suppressed, and the deacidification effect is obtained, so that the Zr melting can be reduced. Oxidation loss. When the amount of P is too large, the content of the P element in the copper alloy becomes too large, so that the thermal conductivity is low. Therefore, in the casting step, it is preferable to blend P so that the content of P in the copper alloy is 0.004 to 0.040% by mass, and it is particularly preferable to blend P to be 0.015 to 0.030% by mass.

In detail, in the casting step, the chemical composition of the seamless tube obtained by performing the aging treatment of the final step becomes the chemical composition of the seamless joint of the copper alloy of the present invention, and the adjustment is performed by The chemical composition of the slab obtained by the casting step. The slab contains one or more elements of Sn, Zn, and Al, and Zr of 0.01 to 0.08% by mass, and is composed of a residual portion of Cu and unavoidable impurities, and the contents of Sn, Zn, Al, and Zr satisfy the following. Formula 1):

(1) 0.4≦A+2B≦0.85

(In the formula, A represents the total content (% by mass) of Sn, Zn, and Al, and B represents the content (% by mass) of Zr).

Preferably, the content of Sn, Zn, Al and Zr in the steel slab further satisfies the following formula (2):

(2) 0.40≦A

(In the formula, A is synonymous with the above), and the content of Zr is 0.06 mass% or less. Further, the slab may contain P, and the content of P at this time is 0.004 to 0.04% by mass.

In the method for producing a copper alloy seamless pipe according to the first aspect of the present invention and the method for producing a copper alloy seamless pipe according to the second aspect of the present invention, secondly, the steel slab obtained by performing the casting step is subjected to This hot extrusion step of hot extrusion processing. In the hot extrusion step, the slab is heated at a predetermined temperature before the hot extrusion process, and then the hot extrusion process is performed. This hot extrusion process is carried out by mandrel extrusion. That is, before the heating, the slab which was previously cold-punched, or the slab which was thermally perforated before extrusion, was hot-extruded in a state of being inserted into a mandrel to obtain a jointless hot extruded tube.

A homogenization treatment can be performed before the hot extrusion step. Further, the slab before the hot extrusion processing may be heated to have a homogenization treatment.

The seamless hot extrudate tube obtained by performing the hot extrusion step is rapidly cooled after the hot extrusion step. This cooling is carried out by extruding the seamless hot extrudate tube into water or by putting the hot-extruded seamless joint extrudate tube into water. The time from the completion of the extrusion of the hot extrusion step to the start of cooling, that is, the time from when the slab passes through the extrusion die until the extrusion of the seamless hot extrusion tube initially contacts the cooling water Long, it will cause Zr to precipitate in between. Further, the precipitate at this time is larger than the precipitate precipitated after the aging treatment, and the dispersion state is also sparse, and there is no effect of preventing the movement of the grain boundary at the subsequent brazing heating, and further, the subsequent aging The treatment consumes Zr for fine precipitation, so it is necessary to avoid such precipitation as much as possible. Therefore, it is preferable to shorten the time from the completion of extrusion to the start of cooling as much as possible. Specifically, the time from the completion of extrusion to the start of cooling is preferably 2 seconds or less.

In the method for producing a copper alloy seamless pipe according to the first aspect of the present invention and the method for producing a copper alloy seamless pipe according to the second aspect of the present invention, the second embodiment is a seamless jointless extruded tube The cold working step of cold working and thinning the outer diameter and thickness of the tube. This cold working is cold working such as calendering and drawing. Further, in the cold working step, cold working such as the rolling process and the drawing process may be performed several times. Further, in the method for producing a copper alloy seamless pipe according to the first aspect of the present invention and the method for producing a copper alloy seamless pipe according to the second aspect of the present invention, the cold working step means all processing by cold. .

After the cold working step, the method for producing a copper alloy seamless pipe according to the first aspect of the present invention is different from the method for producing a copper alloy seamless pipe according to the second aspect of the present invention.

In the method for producing a copper alloy seamless pipe according to the first aspect of the present invention, after the cold working step, the aging treatment of the seamless tube after the cold working obtained by the cold working step is performed. The treatment temperature of the aging treatment is a temperature of 400 to 650 ° C, and the aging treatment at a treatment temperature of 400 to 650 ° C can obtain the size and distribution density of the appropriate Zr-based precipitates and the crystal grain size of the suitable copper alloy. The copper alloy jointless pipe of the present invention. In addition, the treatment temperature and the treatment time of the aging treatment are appropriately selected in such a manner that the size and distribution density of the Zr-based precipitates to be appropriate and the crystal grain size of the copper alloy to be used are appropriately selected.

Further, in order to perform the aging treatment, it is necessary to perform a melt treatment for solidifying Zr in a copper matrix before performing the aging treatment, and in the method for producing a copper alloy seamless joint pipe according to the first aspect of the present invention, The heating before the hot extrusion step has both the melting treatment.

Further, in the method for producing a copper alloy seamless pipe according to the first aspect of the present invention, between the hot extrusion step and the aging treatment, the intermediate annealing treatment is not performed, and the total processing degree of the cold working step therebetween ( The reduction rate of the section is more than 90%. In addition, the total degree of processing of the cold working step refers to the degree of processing of the seamless tube after the final cold working in the cold working step with respect to the seamless tube before the cold working which is initially performed in the cold working step. It is represented by the reduction ratio of the section shown by the following formula (4).

Section reduction rate (%) = ((sectional area before tube processing - sectional area after tube processing) / (breaking area before tube processing)) × 100 (4)

In the method for producing a first copper alloy jointless pipe according to the present invention, after the hot extrusion step, the intermediate annealing treatment is not performed until the aging treatment is performed, and the total processing is performed via the cold working step. When the degree is within the above range, the Zr-based precipitate having a size of 0.5 to 80 nm can be distributed at a distribution density of 10 to 600 / μm ² , preferably a Zr-based precipitate having a size of 0.5 to 10 nm. The distribution density is 100 to 600 pieces/μm ² , and the crystal grains after the aging treatment can be made fine, that is, the average crystal grain size of the copper alloy is 30 μm or less. Since the processing stress introduced by the cold working is a deposition place of the Zr-based precipitate which is subjected to the aging treatment, the introduced processing stress is uniform and fine by increasing the degree of processing of the cold working, and a fine and uniform Zr system is precipitated. Precipitates.

As described above, the copper alloy seamless pipe of the present invention can be obtained by the method for producing a copper alloy seamless pipe according to the first aspect of the present invention.

In the method for producing a copper alloy seamless pipe according to a second aspect of the present invention, after the cold working step, the seamless alloy pipe obtained by performing the cold working step is subjected to a seamless process at 500 to 850 ° C. This intermediate annealing treatment (A) is heated. By performing the intermediate annealing treatment (A), the conversion processing of the conversion processing step can be easily performed. The holding temperature and the holding time in the intermediate annealing treatment (A) are the minimum conditions at which the specified inner groove can be formed by the conversion processing step, that is, the temperature is lowered as much as possible, and the time is shortened as much as possible. In the method for producing a copper alloy seamless pipe according to a second aspect of the present invention, after the intermediate annealing treatment (A) is performed, no other heat treatment is performed until the conversion processing step is performed. That is, the intermediate annealing treatment (A) is a heat treatment before the conversion processing step.

In the method for producing a copper alloy seamless pipe according to a second aspect of the present invention, the transfer processing step of converting the seamless pipe after the intermediate annealing treatment (A) is performed. The conversion processing is performed on the inner surface of the tube material, and the step of forming the inner surface groove is performed in the seamless joint tube after the intermediate annealing treatment (A), and the outer surface is provided with a spiral groove. The processed plug is converted into a ball by a plurality of high-speed rotations, and is pressed by the outside of the tube, and is transferred to the groove on the inner surface of the tube (see Japanese Patent Laid-Open Publication No. 2003-191006). Further, usually, after the intermediate annealing treatment (A) is performed, the conversion processing step is performed after the diameter reduction processing.

In the method for producing a copper alloy seamless pipe according to a second aspect of the present invention, the aging treatment of the inner surface grooved pipe obtained by performing the conversion processing step is performed. The treatment temperature of the aging treatment is a temperature of 400 to 650 ° C, and the aging treatment at a treatment temperature of 400 to 650 ° C can obtain the size and distribution density of the appropriate Zr-based precipitates and the crystal grain size of the suitable copper alloy. The copper alloy jointless pipe of the present invention. In addition, the treatment temperature and the treatment time of the aging treatment are appropriately selected in such a manner that the size and distribution density of the Zr-based precipitates and the crystal grain size of the copper alloy are appropriately selected.

Further, in order to perform the aging treatment, it is necessary to perform a melt treatment for solidifying Zr in a copper matrix before performing the aging treatment, and in the method for producing a copper alloy seamless joint pipe according to a second aspect of the present invention, The heating before the hot extrusion step has both the melting treatment.

In the method for producing a copper alloy seamless pipe according to a second aspect of the present invention, the intermediate annealing treatment is not performed between the hot extrusion step and the intermediate annealing treatment (A), and the total processing degree of the cold working step therebetween ( The reduction in section is more than 90%. Further, the total degree of processing of the cold working step means the degree of processing of the seamless tube after the cold working at the end of the cold working step with respect to the seamless joint pipe before the cold working performed in the cold working step.

In the method for producing a copper alloy seamless pipe according to a second aspect of the present invention, after the hot extrusion step, the intermediate annealing treatment is not performed until the intermediate annealing treatment (A) is performed, and When the total processing degree of the cold working step is set to the above range, the Zr-based precipitate having a size of 0.5 to 80 nm can be distributed at a distribution density of 10 to 600 / μm ² , preferably 0.5 to 10 nm in size. The Zr-based precipitates are distributed at a distribution density of 100 to 600 / μm ² , and the crystal grains after the aging treatment can be made fine, that is, the average crystal grain size of the copper alloy can be 30 μm or less. Since the processing stress introduced by the cold working is a deposition place of the Zr-based precipitate which is subjected to the aging treatment, the processing stress of the cold working is increased, and the introduced processing stress is uniform and fine, and fine and uniform Zr-based precipitation is precipitated. Things. Further, by performing the intermediate annealing treatment (A), the copper alloy is recrystallized, and in order to keep the recrystallized grains as fine as possible, and to maintain such uniform and fine processing stress as much as possible, the hot extrusion step is performed. Thereafter, the intermediate annealing treatment was not performed until the intermediate annealing treatment (A) was performed.

As described above, the copper alloy seamless pipe of the present invention can be obtained by the method for producing a copper alloy seamless pipe according to the second aspect of the present invention.

The copper alloy seamless pipe (inner smooth pipe) of the present invention produced by the method for producing a copper alloy seamless pipe according to the first aspect of the present invention is wound into a coil shape, and is mainly used for supplying a refrigerant pipe. Further, the copper alloy seamless pipe (inner grooved pipe) of the present invention produced by the method for producing a copper alloy seamless pipe according to the second aspect of the present invention is wound into a coil shape and used as a heat exchanger. The heat transfer tube is supplied to the cross-fin tube type heat exchanger.

<The case where the copper alloy seamless pipe of the present invention is supplied to the heat transfer pipe for the cross fin type heat exchanger>

The cross-fin tube type heat exchanger is configured by integrally assembling an air-side aluminum plate fin and a heat-transfer tube on the refrigerant side.

The manufacturing steps of the cross finned tube heat exchanger will be described. In the manufacturing step of the cross-fin tube type heat exchanger, first, an aluminum plate fin formed with a plurality of designated assembly holes is formed by press working or the like.

Next, after the obtained aluminum plate fins are laminated, the heat transfer tubes are inserted into the inside of the assembly holes. This heat transfer tube is produced by cutting a copper alloy seamless pipe of the present invention having a groove formed on the inner surface thereof through the transfer processing step, and cutting it at a predetermined size and bending it by a hairpin type.

Next, the heat transfer tube is expanded and fixed to the aluminum plate fin, and the end of the heat transfer tube opposite to the side where the hairpin bending process is performed is expanded, and the U bend is inserted and hardened. Welding, making heat exchangers.

In such a manufacturing step, since the jointless pipe is subjected to the strong processing of the hairpin type bending process and the pipe end pipe expansion process, it is necessary to have good workability. As the opposite side with good workability, it is desirable that the strength is not excessively high. Therefore, for the jointless pipe, the strength reduction caused by the brazing must be minimized. Further, in the copper alloy seamless pipe of the present invention, as described above, since the size and dispersion density of the Zr-based precipitates are made appropriate, the strength reduction due to brazing is small.

<When the copper alloy jointless pipe of the present invention is supplied to the refrigerant piping>

The refrigerant piping is used, for example, in a liquid dispenser using a carbon dioxide refrigerant to connect a compressor, an evaporator, an expansion valve, and a radiator that constitute a heat pump cycle. In such a pipe connection portion, one pipe end is expanded, and the other pipe end is inserted into the pipe expansion portion, and then brazing can be performed. This case is also the same as the case of using as a heat transfer tube, and since the strong processing of the tube end expansion processing is performed, the workability is good.

[Examples]

The invention is further illustrated by the following examples, which are purely illustrative and not limiting of the invention.

An example of the inner smooth tube in the copper alloy seamless pipe of the present invention will be described.

Example 1 (No. 1 to 6, 9, 17 to 26) and Comparative Example 1 (No. 10 to 16)

A bare metal or a scrap of Cu, Sn, Zn, and Al, a Cu-Zr master alloy, and a Cu-P master alloy were used, and the components shown in Table 1 were blended, and an ingot having a diameter of 254 mm was produced using a high-frequency melting furnace.

Next, the ingot was heated at 930 ° C, and then hot extruded at this temperature to prepare a tube having an outer diameter of 81 mm × a thickness of 8 mm (extrudate tube). In addition, hot extrusion is carried out by extrusion in water. Further, the heat treatment before hot extrusion has a melt treatment.

Next, cold rolling and cold drawing were carried out to obtain a tube having an outer diameter of 9.52 mm and a thickness of 0.8 mm (cold drawing tube).

Next, in a batch furnace, in a non-oxidizing environment, aging treatment was performed at 600 ° C for 30 minutes to obtain a jointless tube.

In addition, no intermediate annealing was performed between hot extrusion and aging treatment. Moreover, at this time, the total cold working degree of cold rolling and cold drawing, that is, the total processing degree (section reduction rate) of the cold working step was 98.8%.

(assessment) 1. The structure of the jointless pipe before brazing <Average crystal grain size>

With respect to the jointless pipes of Example 1 and Comparative Example 1, the crystal grain size was measured in the circumferential cross section of the tube by a comparison method prescribed in JIS H0501, and the average crystal grain size was determined by an average value of any ten points. The results are shown in Table 2.

<Distribution density of precipitates of Zr system>

The distribution density of the Zr-based precipitates was evaluated by observation through a transmission electron microscope.

For the preparation of the sample for observation by electron microscopy, the sample cut out from the seamless tube of the above-mentioned Example 1 and Comparative Example 1 was first made to have a thickness of 0.2 mm by wet polishing using sandpaper, and then phosphoric acid and methanol were used. A solution in which the volume ratio is 1:3 is subjected to electrolytic polishing to form a film.

Next, the obtained film was observed by a transmission electron microscope at an acceleration voltage of 200 kV.

In the observation by a transmission electron microscope, the number of precipitates having a size of 0.5 to 80 nm and the number of precipitates having a size of 0.5 to 10 nm were calculated from a field of view of 0.5 μm × 0.4 μm of an electron microscope photograph photographed at a magnification of 20,000 times. When the precipitate was calculated, the average film thickness was determined under the assumption that the film thickness was changed to a linear shape by a film thickness measurement method using equal-thickness interference fringes, and the volume ratio was converted into an area ratio.

Further, the Zr-based precipitates have a disk-like shape, and may be imaged into an elongated shape in an electron microscope photograph. Therefore, the longest diameter (long diameter) is defined as the size of the precipitate in one precipitate image.

Further, when the number of precipitates is calculated, in the case of more than 200, the image is taken at a magnification of 100,000 times from a field of view of 0.5 μm × 0.4 μm, and three narrow fields of view of 0.1 μm × 0.08 μm are arbitrarily selected and performed in this field of view. The calculation of the precipitates was evaluated by their average values.

The density of the precipitates was evaluated on the following scale.

Level 1: Less than 10 / μm ²

Level 2: 10~100/μm ²

Level 3: 100~600/μm ²

Level 4: More than 600 / μm ²

Further, the density of precipitates having a size of 0.5 to 80 nm, grade 2, and grade 3 fall within the scope of the present invention. The results are shown in Table 2.

2. Processability

The jointless pipe before brazing was subjected to a workability test by a pipe expansion test through a conical plug. Even if the outer diameter of the pipe end is expanded to three times the outer diameter before pipe expansion, those who have no cracks are regarded as qualified "○", and those who have cracked are regarded as unsatisfactory "x". The results are shown in Table 2.

3. Mechanical properties before and after brazing

As a condition equivalent to the temperature rise of the tube at the time of brazing, heating was performed at 800 ° C for 30 seconds, and the mechanical properties (tensile strength and elongation) before and after the heating were evaluated.

The mechanical properties were evaluated by a tensile test, and tensile strength and elongation were measured in accordance with JIS Z2241. The results are shown in Table 3.

Moreover, the average crystal grain size of the seamless pipe structure after brazing was treated and measured in the same manner as the measurement of the average crystal grain size of the seamless pipe structure before brazing. The results are shown in Table 3.

Example 2 (No. 27 to 29) and Comparative Example 2 (No. 30 to 32)

The ingot of the chemical composition shown in Table 4 was used, and then the ingot was heated at a suitable temperature of 930 ° C, and then hot extruded at this temperature to prepare a tube having an outer diameter of 81 mm × a thickness of 8 mm (extrudate tube). . In addition, hot extrusion is carried out by extrusion in water. Further, the heat treatment before hot extrusion has a melt treatment.

Next, cold rolling and cold drawing were carried out to obtain a tube having an outer diameter of 9.52 mm and a thickness of 0.8 mm (cold drawing tube).

Next, in a batch furnace, in a non-oxidizing environment, aging treatment was carried out under the treatment conditions shown in Table 4 to obtain a jointless tube.

Further, in Nos. 27 to 31, intermediate annealing was not performed between hot extrusion and aging treatment. No. 32 was subjected to intermediate annealing between the hot extrusion and the aging treatment under the conditions shown in Table 4.

Further, at this time, the total degree of cold working of the cold rolling and the cold drawing, that is, the total working degree (section reduction rate) of the cold working step is shown in Table 4. In addition, No. 32 is the total cold working degree after the aging treatment after the intermediate annealing.

(assessment)

The microstructure of the jointless pipe before the brazing (average crystal grain size, distribution density of Zr-based precipitates), workability, and mechanical properties of the jointless pipe before and after brazing were the same as in Example 1 and Comparative Example 1. to evaluate. The results are shown in Table 5.

An example of the inner surface grooved pipe in the copper alloy seamless pipe of the present invention will be described.

Example 3 (No. 33~38)

Using bare metal or scrap of Cu, Sn, Zn, and Al, and Cu-Zr master alloy and Cu-P master alloy, the ingot of the chemical composition shown in Table 6 was used, and then, the ingot was heated at 930 °C. Thereafter, hot extrusion was carried out at this temperature to prepare a tube having an outer diameter of 81 mm and a thickness of 8 mm (extrudate tube). In addition, hot extrusion is carried out by extrusion in water. Further, the heat treatment before hot extrusion has a melt treatment.

Next, cold rolling and cold drawing were carried out to obtain a tube having an outer diameter of 9.5 mm and a thickness of 0.5 mm (cold drawing tube).

Next, intermediate annealing (A) was carried out under the following conditions.

<Conditions of Intermediate Annealing (A)>

Minimum heating rate from 500 ° C to 730 ° C: 10 ° C / sec

Maximum arrival temperature: 800 ° C

750 ° C ~ 800 ° C retention time: 2 seconds

Minimum cooling rate from 730 ° C to 500 ° C: 10 ° C / sec

Next, the transfer processing was performed to obtain an inner surface grooved pipe having an outer diameter of 7 mm. The dimensions of the inner grooved pipe obtained are shown in Table 8.

Next, in a batch furnace, in a non-oxidizing environment, aging treatment was performed at 600 ° C for 30 minutes to obtain a jointless tube.

Further, between the hot extrusion and the intermediate annealing (A), no intermediate annealing was performed. Further, at this time, the total cold working degree of the cold rolling and the cold drawing, that is, the total working degree (section reduction rate) of the cold working step was 99.2%.

(assessment)

The microstructure of the jointless pipe before the brazing (average crystal grain size, distribution density of Zr-based precipitates), workability, and mechanical properties of the jointless pipe before and after brazing were the same as in Example 1 and Comparative Example 1. to evaluate. The results are shown in Table 7.

(Example 1, Comparative Example 1)

No. 1 to 6, 9, and 17 to 26 are examples of the present invention. Since the crystal grain size before brazing and the density of precipitates having a size of 0.5 to 80 nm are appropriate, the workability, the strength before and after brazing, and the strength reduction rate after brazing are good.

The No. 1 to 5, 9, 17 to 26 and the precipitate density of 0.5 to 10 nm were also good.

Since No. 18 has a high content of P, the electrical conductivity is slightly lower than that of No. 2, and the thermal conductivity is slightly inferior.

Since No. 17 has a low content of P, the deacidification is insufficient as compared with No. 2, and the possibility of hydrogen embrittlement is higher than that of No. 2, so that it is not preferable in use.

In No. 10 to 12, since the content of Zr is too high, the density of precipitates having a size of 0.5 to 80 nm is too high, and the workability is not good.

In No. 13, since the content of Zr is too low, the density of precipitates having a size of 0.5 to 80 nm is too low, and crystal grains are coarsened during brazing heating, and the strength is low.

No.14 and 15 have low strength because the A+2B value is too low.

No. 16 has a low processability because the A+2B value is too high.

(Example 2, Comparative Example 2)

No. 27 to 29 are examples of the present invention. Since the crystal grain size before brazing and the density of precipitates having a size of 0.5 to 80 nm are appropriate, the workability, the strength before and after brazing, and the strength reduction rate after brazing are good.

In No. 30, since the density of precipitates of 0.5 to 80 nm is too low, crystal grains are coarsened during brazing heating, and the strength is also lowered.

No. 31 has a high process density due to an excessively high density of precipitates having a size of 0.5 to 80 nm.

Since No. 32 has an excessively large crystal grain size before brazing, even if the density of the precipitate is appropriate, the crystal grain size after brazing is large and the strength is low.

(Example 3)

No. 33 to 38 are examples of the present invention. Since the crystal grain size before brazing and the density of precipitates having a size of 0.5 to 80 nm are appropriate, the workability, the strength before and after brazing, and the strength reduction rate after brazing are good.

(industrial availability)

In the design of the compressive strength of a heat exchanger or the like, the tube thickness is determined based on the material strength of the heat affected portion of the brazing. However, the copper alloy jointless pipe of the present invention has a high strength and a small decrease in strength due to brazing. Therefore, according to the present invention, the heat transfer tube and the refrigerant tube can be made thinner without the influence of the hard solder heat. It is not necessary to increase the unnecessary strength, and it is possible to ensure good workability by suppressing the decrease in workability as the opposite side of the strength.

t. . . thickness

h. . . Wing height

α. . . Wing angle

Fig. 1 is a view showing the shape of a groove after the transfer processing of the third embodiment.

Claims (5)

A copper alloy jointless pipe obtained by processing a copper alloy, characterized in that the copper alloy contains one or more elements of Sn, Zn and Al, and Zr of 0.01 to 0.06 mass%, and the residual portion Cu and inevitable impurities are formed, and the content of Sn, Zn, Al, and Zr in the copper alloy satisfies the following formula (1) and the following formula (2): (1) 0.4 ≦ A + 2 B ≦ 0.85 (2) 0.40≦A (wherein, A represents the total content (% by mass) of Sn, Zn, and Al, and B represents the content (% by mass) of Zr), and the average crystal grain size of the copper alloy jointless tube is 30 μm or less, 0.5~ The 80 nm-sized Zr-based precipitates are distributed at 10 to 600 / μm ² . The copper alloy seamless joint pipe according to the first aspect of the patent application, wherein the content of Sn is 0.01% by mass or more, and the content of Zn and the content of Al are less than 0.01% by mass. The copper alloy seamless joint pipe according to the first aspect of the patent application, wherein the content of Zn is 0.01% by mass or more, and the content of Sn and the content of Al are less than 0.01% by mass. For example, the copper alloy jointless pipe of the first application patent scope, wherein the content of Al is 0.01% by mass or more, and the content of Sn and the content of Zn are not satisfied. 0.01% by mass. The copper alloy seamless pipe according to any one of claims 1 to 4, wherein the content of P is 0.004 to 0.04% by mass.