JP4694527B2 - Copper alloy tube for heat-resistant and high-strength heat exchanger and method for producing the same - Google Patents

Description

  The present invention relates to a copper alloy tube for a heat-resistant and high-strength heat exchanger having excellent pressure fracture strength and productivity.

  For example, a heat exchanger of an air conditioner passes a U-shaped copper tube bent into a hairpin shape (hereinafter referred to as a copper tube also includes a copper alloy tube) through an aluminum fin through-hole and expands the copper tube with a jig. Then, the copper tube and aluminum fin are brought into close contact with each other, and the open end of the copper tube is expanded, and a copper tube (return bend) bent into a U-shape is inserted into the expanded portion, and a solder such as phosphor copper braze A heat exchanger in which a plurality of hairpin-shaped copper tubes are connected by a return bend copper tube is manufactured by brazing the copper tube (return bend) to the expanded portion of the hairpin-shaped copper tube with a material.

  For this reason, it is requested | required that the copper tube used for a heat exchanger should have favorable heat conductivity, bending workability, and brazing property. Therefore, phosphorus deoxidized copper having good characteristics and appropriate strength is widely used.

HCFC (hydrochlorofluorocarbon) fluorocarbons have been widely used as refrigerants for heat exchangers such as air conditioners. However, HCFC has a low ozone depletion coefficient, so its value is small in terms of protecting the global environment. HFC (hydrofluorocarbon) -based fluorocarbons have been used. Further, CO ₂ that is a natural refrigerant has come to be used in heat exchangers used in water heaters, automotive air conditioners, vending machines, and the like. In the heat exchanger, the pressure at which these refrigerants are used (pressure flowing through the heat transfer tubes of the heat exchanger) is maximized in the condenser (gas cooler in CO ₂ ). 8 MPa, the R410A of HFC-based fluorocarbons 4 MPa, also in CO ₂ refrigerant is about 7 to 14 MPa (supercritical state), the operating pressure of the newly adopted refrigerant is increased to 1.4 to 5 times that of the conventional refrigerant R22 is doing.

  When the burst pressure of the heat transfer tube is P, the outer diameter of the heat transfer tube is D, the tensile strength of the heat transfer tube is σ, and the wall thickness of the heat transfer tube is t (in the case of an internally grooved tube), Has a relationship of P = 2 × σ × t / (D−0.8t). When the above formula is arranged with respect to the wall thickness t, t = (D × P) / (2 × σ + 0.8P), and it can be seen that the wall thickness can be reduced as the tensile strength of the heat transfer tube is increased. Actually, when selecting a heat transfer tube, a heat transfer tube having a tensile strength and a thickness calculated with respect to the pressure obtained by multiplying the above P by a safety factor S (usually about 2.5 to 5) is used.

  In the case of a phosphorous deoxidized copper heat transfer tube, since the tensile strength is small, it is necessary to increase the thickness of the tube in order to cope with an increase in the operating pressure of the refrigerant. In addition, when assembling the heat exchanger, the brazed part is heated to a temperature of 800 ° C. or higher for several seconds to several tens of seconds. Therefore, it is necessary to make the wall thickness thicker. Thus, when phosphorous deoxidized copper is used as the heat transfer tube, the mass of the heat exchanger is increased and the price is increased. There has been a strong demand for heat tubes.

  In order to meet such demands, for example, Co: 0.02 to 0.2 mass%, P: 0.01 to 0.05 mass%, as a copper alloy tube having excellent 0.2% proof stress and fatigue strength , C: 1 to 20 ppm, the remainder being made of Cu and inevitable impurities, and oxygen of impurities is 50 ppm or less, and a seamless copper alloy tube for a heat exchanger (Patent Document 1) has been proposed. Also, Sn: 0.1 to 1.0 mass%, P: 0.005 to 0.1 mass%, O: 0.005 mass% or less and H: 0.0002 mass% or less, with the balance being Cu In addition, a copper alloy tube for heat exchanger (Patent Document 2) is proposed, which has a composition comprising unavoidable impurities and an average crystal grain size of 30 μm or less.

JP 2000-1728 A JP 2003-268467 A

  However, the copper alloy of Patent Document 1 has 0.2% proof stress and fatigue strength by precipitation strengthening with Co phosphide, but because the emphasis is on strength, the 0.2% proof stress value is high, and the heat exchanger When bending into a hairpin tube during assembly processing, cracks are likely to occur, causing a decrease in yield. In addition, Co phosphide, which is a strengthening mechanism of precipitation strengthening, is heated at a temperature higher than that of phosphor copper brazing, or even if the heating temperature is about the brazing temperature of phosphor copper brazing. There is a problem that the strength such as tensile strength, proof stress and breaking pressure after heating is reduced.

  Moreover, the copper alloy of Patent Document 2 has improved strength due to solid solution strengthening of Sn, and the softening after brazing is also smaller than that of Patent Document 1, and when used in a heat transfer tube, the thickness of the tube can be reduced. Although it becomes possible, when Sn is contained until a predetermined strength is satisfied, there is a problem that hot deformation resistance is increased and productivity is lowered during extrusion.

  By the way, when hydrostatic pressure is applied to a copper pipe having a tensile strength σ and the breaking pressure when the pipe breaks is PF, PF and σ are normally in a proportional relationship, and PF / σ = α (α Is a proportionality constant). PFd / σd = αd, where σd is the tensile strength of the soft phosphorous deoxidized copper tube and PFd is its breaking pressure. When a light drawing process is applied to the soft phosphorus-deoxidized copper pipe, the tensile strength increases, σd ′ (σd ′> σd), and the rupture pressure increases accordingly, resulting in PFd ′ (PFd ′> PFd). . The ratios PFd / σd and PFd ′ / σd ′ of PF and σ are both αd, and the pressure strength PFd can be improved by improving the tensile strength σd of the phosphorous deoxidized copper pipe. However, when the tensile strength is improved, the ductility is drastically reduced, and cracks and wrinkles are likely to occur at the bent part of the heat transfer tube, and the part becomes the base point and breaks at a pressure lower than the predetermined breaking pressure. There is.

  The present invention has been made in view of such a problem, and has a ratio of fracture pressure / tensile strength exceeding the ratio of fracture pressure / tensile strength to a phosphorous deoxidized copper pipe, and has extrudability and bending. It aims at providing the copper alloy tube for heat-resistant high-strength heat exchangers which was excellent in heat resistance and heat resistance.

The copper alloy tube for heat-resistant and high-strength heat exchanger according to the present invention has a Zr of 0.005 to 0.2% by weight, Sn: 0.01 to 2.0% by weight, S: 0.005% by weight or less, O: 0.005 wt% or less, and H: 0.0002 wt% or less, with the balance being composed of Cu and inevitable impurities, the tensile strength after annealing is 250 N / mm due to precipitation of Zr by annealing ² or more, the elongation is 40% or more, and the average crystal grain size is 30 μm or less.
Moreover, the manufacturing method of the copper alloy tube for heat-resistant high-strength heat exchangers according to the present invention is as follows: Zr: 0.005 to 0.2% by weight, Sn: 0.01 to 2.0% by weight, S: 0.005% by weight %, O: 0.005% by weight or less, and H: 0.0002% by weight or less, and the billet having the composition consisting of Cu and unavoidable impurities in the remainder is punched after heating, and then 750 Hot extrusion at 950 ° C., after hot extrusion, quenching is performed so that the cooling rate until the surface temperature of the extruded tube reaches 300 ° C. is 10 ° C./second or more, and then the extruded tube is rolled and drawn Then, by annealing, Zr is precipitated by annealing, the tensile strength after annealing is 250 N / mm ² or more, the elongation is 40% or more, and the average crystal grain size is 30 μm or less. A copper alloy tube is obtained.

  This copper alloy tube for heat-resistant and high-strength heat exchangers preferably further contains P: 0.005 to 0.1% by weight.

  Further, it is preferable to contain Zn: 0.01 to 1.0% by weight.

  Furthermore, it is preferable to contain a total of less than 0.07% by mass of one or more elements selected from the group consisting of Fe, Ni, Mn, Mg, Cr, Ti and Ag.

  The copper alloy tube for a heat-resistant and high-strength heat exchanger according to the present invention has a tensile strength of the copper alloy tube of σa1, a breaking pressure of PFa1, and a tensile strength of a phosphorous deoxidized copper tube having the same outer diameter and thickness as the copper alloy tube. When the strength is σd1 and the breaking pressure is PFd1, it is preferable that PFa1 / σa1> PFd1 / σd1.

Further, the tensile strength after heating at 800 ° C. for 15 seconds is 235 N / mm ² or more, the average crystal grain size is 100 μm or less, the tensile strength is σa 2, the breaking pressure is PFa 2, the same outer diameter and meat It is preferable that PFa2 / σa2> PFd2 / σd2 when the tensile strength of the thick phosphorous deoxidized copper pipe is σd2 and the breaking pressure is PFd2.

Furthermore, the copper alloy tube is useful as an internally grooved tube.
May be.

  The average crystal grain size is measured at 10 arbitrary locations in the tube axis direction by measuring the crystal grain size in the thickness direction by the cutting method defined in JISH0501 in a cross section parallel to the axis direction of the tube. The average value of the measured values was used.

  Since the copper alloy tube for a heat exchanger of the present invention has a predetermined composition, it has a ratio α = PFa1 / σa1 which exceeds the ratio αd (= PFd1 / σd1) between the fracture pressure and the tensile strength in phosphorous deoxidized copper. Since the pressure strength (breaking pressure PFa1) can be increased without increasing the tensile strength σa1 of the copper alloy tube, high ductility can be ensured at the same time even if the breaking pressure is increased. For this reason, when processing a copper alloy tube, the generation of cracks and wrinkles can be prevented. In the present invention, since the ratio α = PFa1 / σa1 is high, even if the thickness of the copper alloy tube is reduced, the tensile strength is reduced by that amount, but a predetermined pressure resistance can be ensured. .

  Hereinafter, the present invention will be described in detail. As a result of various experimental studies by the present inventors, a copper alloy tube capable of solving the problems of the present invention can be obtained by appropriately specifying the Zr content, Sn content, S content, tensile strength, etc. I found.

“Zr: 0.005 to 0.2 mass%”
Zr is a component capable of improving the tensile strength and the strength by forming a precipitate of Zr in the copper alloy of the present invention. If the content of Zr exceeds 0.2% by mass, the strength becomes too high and the elongation is lowered, which adversely affects extrudability and workability. Further, when the Zr content in the alloy of the present invention is less than 0.005% by mass, a predetermined strength cannot be obtained. Therefore, the Zr content needs to be 0.005 to 0.2% by mass.

“Sn: 0.01 to 2.0 mass%”
Sn improves the tensile strength by solid solution hardening and suppresses the coarsening of the crystal grain size against the heat effect of brazing such as phosphor copper brazing, thereby improving the heat resistance. When the Sn content exceeds 2.0% by mass, solidification segregation in the ingot becomes severe, and segregation may not be completely eliminated by normal hot extrusion and / or thermomechanical treatment. , Mechanical properties, bendability, texture after brazing and non-uniformity of mechanical properties. Moreover, in order to increase the extrusion pressure and make the extrusion pressure the same as that of the Sn ≦ 2.0 mass% alloy, it is necessary to increase the extrusion temperature, thereby increasing the surface oxidation of the extruded material and increasing the productivity. And the surface defects of the copper alloy tube increase. Further, when the Sn content in the alloy of the present invention is less than 0.01% by mass, it becomes impossible to obtain sufficient tensile strength and fine crystal grain size after annealing and after brazing heating. The effect of suppressing the decrease in strength during brazing heating due to the above and the like and the effect of preventing the coarsening of the crystal grains become insufficient. Therefore, it is necessary that the Sn content be 0.01 to 2.0 mass%.

“S: 0.005 mass% or less”
S is present in the matrix by forming a compound with Cu in the alloy of the present invention. When the S content increases, ingot cracking and hot extrusion cracking during ingot increase. Moreover, even if hot extrusion cracking does not occur, when the extruded material is cold-rolled and drawn, the Cu-S compound inside the material stretches in the axial direction of the tube, and cracking is likely to occur at the Cu-S compound interface, It may cause surface flaws, cracks, etc. during product processing and in products, reducing product yield. Even when cracks do not occur at the Cu-S compound interface, when bending the alloy pipe of the present invention, it becomes a starting point of crack generation, and the frequency of occurrence of cracks at the bent portion increases. In order to improve such problems, the S content in the alloy of the present invention needs to be 0.005% or less, desirably 0.003% or less, and more desirably 0.0015% or less. S is relatively simpler than copper metal, raw materials such as scrap, oil adhering to scrap, melting casting atmosphere (charcoal / flux covering molten metal, SOx gas in furnace atmosphere, furnace material, etc.) In order to reduce the S content to 0.005% by mass or less because of being incorporated into the steel, the amount of low-grade Cu ingots and scrap used is reduced, the SOx gas in the melting atmosphere is reduced, the selection of appropriate furnace materials, Mg, Measures such as addition of trace amounts of elements such as Ca, which have a strong affinity for S, to the molten metal are effective.

"Other impurities"
In addition, the impurity elements As, Bi, Sb, Pb, Se, and Te other than S similarly decrease the soundness of the ingot, the hot extruded material, and the cold work material, and impair the bending workability of the pipe. Therefore, the total content of these elements is preferably 0.0015% or less, desirably 0.0010% or less, and more desirably 0.0005% or less.

“O: 0.005 mass% or less”
In the copper alloy pipe of the present invention, when the O content exceeds 0.005 mass%, the oxides of Cu and Sn are entrained in the ingot, the soundness of the ingot is lowered, and the manufactured pipe Bending workability tends to decrease. For this reason, it is necessary to make content of O 0.005 mass% or less. In order to further improve the bending workability, the O content is desirably 0.003% by mass or less, and more desirably 0.0015% or less.

“H: 0.0002 mass% or less”
When more hydrogen is taken into the molten metal during melt casting, it is present in the ingot in a state of pinhole and grain boundary enrichment, and cracks are generated during hot extrusion. Further, even after the extrusion, blistering of H is likely to occur at the grain boundaries during annealing, and the product yield decreases. For this reason, in the copper alloy pipe | tube of this invention, it is necessary to make content of H 0.0002 mass% or less. In order to further improve the product yield, the H content is desirably 0.0001% by mass or less.

  In addition, in order to make the H content 0.0002% by mass or less, drying of the raw material at the time of melting and casting, red hotness of the melt-coated charcoal, reduction of the dew point of the atmosphere in contact with the molten metal, oxidation of the molten metal before adding phosphorus Measures such as making a little difference are effective.

“Tensile strength: 250 N / mm ² or more”
When the tensile strength is less than 250 N / mm ² , the strength when incorporated in a heat exchanger such as an air conditioner is insufficient, and the strength after brazing cannot be sufficiently maintained. Therefore, the tensile strength of the tube needs to be 250 N / mm ² or more. Here, the tensile strength is the tensile strength in the tube axis direction of the copper alloy tube of the present invention that has been annealed to be a soft material.

“Elongation: 40% or more”
Elongation indicates the workability of the tube. If the elongation is less than 40%, the tube does not sufficiently extend during the hairpin bending process, cracking occurs in the bent portion, and inconvenience occurs during the processing of the in-machine piping. Therefore, the elongation needs to be 40% or more.

“Crystal grain size: average grain size is 30 μm or less”
The grain size plays an important role in the strength and workability of the material. In general, if the crystal grain size is small, the strength is high but the workability is lowered. If the crystal grain size is large, the strength is lowered and the workability is improved. When the crystal grain size exceeds 30 μm, the strength decreases, the pressure resistance when incorporated in a heat exchanger such as an air conditioner becomes insufficient, and the strength after brazing cannot be sufficiently maintained. For the average crystal grain size, the average crystal grain size in the thickness direction was measured for the cross section parallel to the axial direction of the copper alloy tube by the cutting method defined in JISH0501, and this was measured at any 10 locations in the pipe axis direction. The average value was measured as the average grain size.

“P: 0.005 to 0.1 mass%”
In the copper alloy of the present invention, P is a component that can form precipitates with a compound with Zr as described above to improve the tensile strength or improve the strength. When the P content in the copper alloy of the present invention exceeds 0.1% by mass, the electrical conductivity is lowered, and hot workability and cold workability are inhibited. On the other hand, if the P content is less than 0.005% by mass, the predetermined strength cannot be obtained, and deoxidation becomes insufficient, the oxide is caught in the ingot, and the soundness of the ingot is reduced. At the same time, the bending workability of the manufactured pipe is likely to deteriorate. Therefore, it is necessary to make the P content 0.005 to 0.1% by mass.

“Zn: 0.01 to 1.0 mass%”
By adding Zn, the strength, heat resistance and fatigue strength can be improved without greatly reducing the thermal conductivity of the copper alloy tube. In addition, the addition of Zn can reduce the wear of tools used for cold rolling, drawing, rolling, etc., and has the effect of extending the life of drawing plugs, grooved plugs, etc., contributing to the reduction of production costs. . Also, in the heat exchanger assembly process, wear of the expanded burette during tube expansion when the heat transfer tube is brought into close contact with the mandrel or aluminum fin during bending of the hairpin can also be reduced.

  When the Zn content exceeds 1.0 wt%, the stress corrosion cracking sensitivity becomes high. Further, when the Zn content is less than 0.01% by mass, the above-described effects are not sufficient. Therefore, the Zn content needs to be 0.01 to 1.0 mass%.

“Total of less than 0.07 mass% of one or more elements selected from the group of Fe, Ni, Mn, Mg, Cr, Ti and Ag”
Fe, Ni, Mn, Mg, Cr, Ti, and Ag all improve the strength, pressure breakdown strength, and heat resistance of the copper alloy of the present invention, refine crystal grains, and improve bending workability. When the total content of the elements exceeds 0.07% by mass, the extrusion pressure increases. Therefore, when extrusion is performed with the same pressing force as that without adding these elements, the hot extrusion temperature is increased. Is required. Thereby, since the surface oxidation of the extruded material increases, surface defects frequently occur in the copper alloy tube of the present invention, and the product yield decreases. Therefore, it is desirable that the total of one or more elements selected from the group of Fe, Ni, Mn, Mg, Cr, Ti, and Ag is less than 0.07% by mass. The content is more preferably less than 0.05%, and still more preferably less than 0.03% by mass.

“When the tensile strength of the copper alloy pipe is σa1, the pressure breaking pressure is Pfa1, the tensile strength of the phosphorous deoxidized copper pipe having the same outer diameter and thickness as the copper alloy pipe is σd1, and the pressure breaking pressure is PFd1, Pfa1 / Σa1> PFd1 / σd1 ”
In the copper alloy pipe of the present invention, the ratio Pfa1 / σa1 between the pressure breaking pressure Pfa1 and the tensile strength σa1 is larger than the PFd1 / σd1 between the pressure breaking pressure PFd1 and the tensile strength σd1 of the phosphorous deoxidized copper pipe. For example, even when pipes having the same tensile strength and the same wall thickness are used, the copper alloy pipe of the present invention can guarantee a higher pressure strength. Further, if the tensile strength of the phosphorus-deoxidized copper pipe and the copper alloy pipe of the present invention are the same, the copper alloy pipe of the present invention has a larger elongation, so that cracking due to bending of the pipe is less likely to occur, and it is more severe. Bending (bending with a small bending radius) can be performed.

  In addition, since the ratio between the pressure breaking pressure and the tensile strength is the same alloy, even if the tempering is changed, the ratio is almost the same, so here, for example, the annealed phosphorus deoxidized copper pipe and the copper alloy pipe of the present invention Can be determined by measuring the tensile strength and pressure fracture strength.

“Tensile strength after heating at 800 ° C. for 15 seconds: 235 N / mm ² or more”
When processed into a heat exchanger, if the tensile strength after heating for 15 seconds at 800 ° C. due to the heat effect of brazing is less than 235 N / mm ² , the operating pressure of the HFC-based CFC refrigerant and carbon dioxide refrigerant is high. Sometimes fatigue failure tends to occur.

“Average crystal grain size after heating at 800 ° C. for 15 seconds: 100 μm or less”
When processed into a heat exchanger, the crystal grain size becomes coarse after heating at 800 ° C. for 15 seconds due to the heat effect of brazing, but when the value exceeds 100 μm, the pressure strength is greatly reduced at the brazed part. When used in a heat exchanger for HFC-based chlorofluorocarbon refrigerant and carbon dioxide refrigerant having a high operating pressure, the reliability decreases. Therefore, the average crystal grain size is preferably 100 μm or less, and more preferably 60 μm or less.

“The tensile strength of the copper alloy tube after heating at 800 ° C. for 15 seconds is σa2, the pressure breaking pressure is PFa2, the tensile strength of the phosphorus deoxidized copper tube having the same outer diameter and thickness as the copper alloy tube is σd2, the pressure resistance PFa2 / σa2> PFd2 / σd2 when the burst pressure is PFd2 "
After the copper alloy tube of the present invention is heated to 800 ° C. for 15 seconds, the ratio PFa2 / σa2 between the pressure breaking pressure PFa2 and the tensile strength σa2 is equal to the pressure breaking pressure PFd2 and the tensile strength σd2 of the phosphorous deoxidized copper tube. Therefore, even when pipes having the same tensile strength and the same wall thickness are used, for example, the copper alloy pipe of the present invention can guarantee a higher pressure strength.

  Note that the ratio PFa2 / σa2 between the pressure breaking pressure PFa2 and the tensile strength σa2 is almost the same value even if the tempering is different, so if the relationship of claims 1 to 4 is satisfied, the heat treatment of claim 5 The same relationship is maintained for later ratio relationships.

“The copper alloy tube is an internally grooved tube”
Since the copper alloy tube of the present invention can have a higher tensile strength and a smaller crystal grain size than a phosphorous deoxidized copper tube, it is suitable for the production of an internally grooved tube by rolling. In particular, since the tensile strength is large, it is difficult to stretch in the drawing direction during rolling, so that the groove of the grooved plug is smoothly filled with the alloy tube meat, and the inner surface grooved tube having a good fin shape is provided. It becomes possible to process at high speed.

  Next, the method for producing a copper alloy tube of the present invention will be described below by taking the case of a smooth tube or an internally grooved tube as an example.

  First, the raw electrolytic copper is dissolved in a reducing atmosphere. After the copper is dissolved, a predetermined amount of Zr and Sn are added, and further, P is added by adding Cu-15 mass% P intermediate alloy as required. To do. The molten metal composition is adjusted to a predetermined composition, and then cast into billets having a predetermined dimension. Thereafter, the billet is heated to 750 to 950 ° C.

  The heated billet is then perforated and hot extruded at 750 to 950 ° C. The processing rate of hot extrusion ([cross-sectional area of the perforated billet−cross-sectional area of the raw tube after hot extrusion] / [cross-sectional area of the perforated billet] × 100%) is desirably 80% or more. , More preferably 90% or more.

  Thereafter, rapid cooling is performed. In order for the copper alloy tube of the present invention to exhibit predetermined characteristics, it is necessary to dissolve Co after extrusion and to prevent the crystal grains from becoming coarse due to recrystallization. The hot extruded material is quenched by the method. After hot extrusion, cooling is performed so that the cooling rate until the surface temperature of the extruded tube reaches 300 ° C. is 10 ° C./second or more, preferably 15 ° C./second or more, more preferably 20 ° C./second or more. Is preferred.

  Then, the extrusion element tube is rolled. By reducing the rolling processing rate to 95% or less, preferably 90% or less in terms of cross-sectional reduction, product defects can be reduced.

  Thereafter, the rolling raw tube is subjected to a drawing process to manufacture a raw tube having a predetermined size. Usually, drawing is performed using several drawing machines, but surface defects and internal cracks can be reduced by setting the processing rate (cross-sectional reduction rate) by each drawing machine to 40% or less.

  Furthermore, the copper alloy tube after the drawing process is annealed. At this time, the drawing tube is annealed under conditions where recrystallization and Zr precipitation occur. Elongation is restored by recrystallization, the workability of the tube is improved, and the intended tensile strength and proof stress can be maintained by the precipitation of Zr. In order to produce the copper alloy tube of the present invention, it is desirable to hold the drawing tube at a substantial temperature of 400 to 700 ° C. for about 5 to 120 minutes. The average rate of temperature increase from room temperature to a predetermined temperature is 5 ° C./min or more, preferably 10 ° C./min or more. Normally, continuous annealing with a roller hearth furnace is performed, but high-frequency heating, short-time heating, high-speed cooling, and short-time heating annealing may be performed using a high-frequency induction heating furnace. Thereby, a smooth tube is manufactured.

  Next, when manufacturing an inner surface grooved tube, the smooth tube manufactured as described above is used as a base tube, and the inner surface is grooved. That is, a grooved rolling process is performed on the annealed smooth tube to produce an internally grooved tube. Next, the grooved inner grooved tube is annealed as necessary. The annealing conditions are the same as described above. Thereby, an internally grooved tube is manufactured.

  Next, examples of the present invention will be described in comparison with comparative examples that are out of the scope of the present invention.

(First embodiment)
The first embodiment is for a smooth tube. After adding Zn and Sn to the molten metal in which electrolytic copper was dissolved, a Cu-P master alloy was added to prepare a molten metal having a predetermined composition and cast into a billet having a diameter of 300 mm. Next, after the billet was heated to 850 to 950 ° C., the billet center was pierced, and an extruded element tube having an outer diameter of 100 mm and a wall thickness of 10 mm was produced by hot extrusion. This cross-sectional reduction rate was 90% or more. The raw tube after extrusion was rapidly cooled, and the average cooling rate up to 300 ° C. was estimated to be 20 ° C./second or more from the time from immediately after extrusion to water cooling and the surface temperature of the extruded raw tube after water cooling. The extruded element tube was rolled and drawn to produce an element tube having an outer diameter of 9.52 mm and a wall thickness of 0.80 mm. The cross-sectional reduction rate in rolling was 90% or less, and the processing rate per pass in drawing was 40% or less. In a roller hearth furnace in a reducing gas atmosphere, the drawing tube was heated to 550 to 650 ° C. (substance temperature) (average heating rate of 10 to 25 ° C./min) and held at that temperature for 30 to 80 minutes. The specimen was cooled to room temperature.

(Second embodiment)
The second embodiment is for an internally grooved tube. The rolled tube after the extrusion of the first example (smooth tube) was used as a raw tube for inner surface grooving.

  This rolled blank was drawn to produce a rolled rolled blank. The base tube for grooved rolling was subjected to intermediate annealing with an induction heater. Next, the grooved rolling element tube subjected to intermediate annealing was subjected to grooved rolling to produce an internally grooved tube having an outer diameter of 7 mm and a bottom wall thickness of 0.23 mm. This inner surface groove has a fin height of 0.16 mm, a lead angle of 35 °, and a number of peaks of 55. Thereafter, the inner grooved tube was passed through a heating zone in an reducing furnace in a reducing gas atmosphere at an ambient temperature of 600 ° C. for 120 minutes and then gradually cooled to room temperature through a cooling zone.

(Test method)
The test shown below was implemented about the above-mentioned Example and comparative example. The conventional product is JISH3300C1220T, a phosphorous deoxidized copper tube. The breaking pressure was measured by sealing one end of the specimen cut to a length of 300 mm and applying the water pressure from the other end to burst the specimen.

  Extrudability was determined by visual inspection of the presence or absence of cracks when an ingot having an outer diameter of 8 mm and a length of 12 mm was crushed at a strain rate of 0.1 / S. The thing was set as x.

  The stress corrosion cracking test was carried out by the following method. A 75 mm long test piece was cut from the tube, degreased and dried, and then separated from the liquid surface by a desiccator containing 11.8% or more of ammonia water diluted with an equal amount of pure water as specified in JIS K8085. And hold in this ammonia atmosphere at room temperature for 2 hours. Thereafter, the test piece was crushed to 50% of the original outer diameter, and cracking was visually determined. No cracking was indicated by ○, and cracking was indicated by ×.

  In the hydrogen embrittlement test, the test piece was heated at 850 ° C. for 30 minutes in a hydrogen stream, then polished and etched, and magnified 100 times with a microscope to confirm the presence or absence of embrittlement. No embrittlement is indicated by ○, and embrittlement is indicated by ×.

  These test results are shown in Tables 1 to 4 below.

  Table 1 relates to the smooth tube (annealed material) of the first embodiment. As shown in Table 1, in Examples 1 to 10 of the present invention, PFa1 / σa1 was higher than those of Comparative Examples 1 to 13 and the conventional example, and the results of the stress corrosion cracking test and the hydrogen embrittlement test were also excellent. It was. On the other hand, in Comparative Examples 1 to 9, PFa1 / σa1 was low, stress corrosion cracking occurred, or hydrogen embrittlement occurred. Further, the conventional example has a low PFa1 / σa1.

  Table 2 shows the characteristics after the smooth tube (annealed material) of the first example was heated at 800 ° C. for 15 seconds. As shown in Table 2, even after the annealed material was heated at 800 ° C. for 15 seconds, Examples 1 to 10 of the present invention had a sufficiently high PFa2 / σa2 value, and the tensile strength and breaking pressure were also high. It was expensive.

  Table 3 relates to the internally grooved tube (annealed material) of the second example, and Examples 11, 12, 13, and 14 of the present invention have higher PFa1 / σa1 than Comparative Example 10 and the conventional example, and stress corrosion. The results of the cracking test and hydrogen embrittlement test were also excellent. On the other hand, in the case of the comparative example 1 and the conventional example, PFa1 / σa1 was low, and the tensile strength and the fracture pressure were low.

  Table 4 shows the characteristics after heating the internally grooved tube (annealed material) of the second example at 800 ° C. for 15 seconds. As shown in Table 4, Examples 15, 16, 17, and 18 of the present invention have a sufficiently high PFa2 / σa2 value even after heating at 800 ° C. for 15 seconds, and the tensile strength and breaking pressure are also high. It was expensive.

  Since the copper alloy tube of the present invention is excellent in pressure breakdown strength, a heat transfer tube (smooth tube and internally grooved tube) of a heat exchanger using a refrigerant such as carbon dioxide and chlorofluorocarbon, an evaporator and a condenser of the heat exchanger are provided. It can be used as a refrigerant pipe, an in-machine pipe to be connected, a part of the heat exchanger, a four-way valve, an accumulator or the like. In addition, since the copper alloy pipe of the present invention has an excellent pressure fracture strength even after brazing heating, a heat transfer pipe having a brazed portion, an in-machine pipe, a refrigerant pipe, a heat exchanger member, a water pipe, a kerosene pipe, and a heat pipe , Four-way valve, control copper pipe, etc.

Claims (11)

Zr: 0.005 to 0.2 wt%, Sn: 0.01 to 2.0 wt%, S: 0.005 wt% or less, O: 0.005 wt% or less, and H: 0.0002 wt% It has the following composition, the balance is composed of Cu and inevitable impurities, the tensile strength after annealing is 250 N / mm ² or more due to the precipitation of Zr by annealing, the elongation is 40% or more, the average grain size Is a copper alloy tube for heat-resistant and high-strength heat exchangers, characterized by being 30 μm or less. The copper alloy tube for heat-resistant and high-strength heat exchangers according to claim 1, further comprising P: 0.005 to 0.1% by weight. The copper alloy tube for heat-resistant and high-strength heat exchangers according to claim 1 or 2, further comprising Zn: 0.01 to 1.0% by weight. Furthermore, one or more elements selected from the group consisting of Fe, Ni, Mn, Mg, Cr, Ti and Ag are contained in a total amount of less than 0.07% by mass. 2. A copper alloy tube for heat-resistant and high-strength heat exchangers according to item 1. When the tensile strength of the copper alloy pipe is σa1, the breaking pressure is PFa1, the tensile strength of a phosphorous deoxidized copper pipe having the same outer diameter and thickness as the copper alloy pipe is σd1, and the breaking pressure is PFd1, PFa1 / The copper alloy tube for a heat-resistant and high-strength heat exchanger according to any one of claims 1 to 4, wherein σa1> PFd1 / σd1. Further, the tensile strength after heating at 800 ° C. for 15 seconds is 235 N / mm ² or more, the average crystal grain size is 100 μm or less, the tensile strength is σa2, the breaking pressure is PFa2, the same outer diameter and the meat 6. The high heat resistance according to claim 1, wherein when the tensile strength of the thick phosphorous deoxidized copper pipe is σd2 and the breaking pressure is PFd2, PFa2 / σa2> PFd2 / σd2. Copper alloy tube for strength heat exchanger. The copper alloy tube for heat-resistant and high-strength heat exchangers according to any one of claims 1 to 6, wherein the copper alloy tube is an internally grooved tube. Zr: 0.005 to 0.2 wt%, Sn: 0.01 to 2.0 wt%, S: 0.005 wt% or less, O: 0.005 wt% or less, and H: 0.0002 wt% A billet having the following composition, the balance of which is composed of Cu and inevitable impurities, is heated and then subjected to perforation, and then hot extruded at 750 to 950 ° C. After hot extrusion, the surface temperature of the extruded element tube is Quench rapidly so that the cooling rate until it reaches 300 ° C. is 10 ° C./second or more, then roll and draw the extruded element tube, and then anneal to precipitate Zr, tensile strength after annealing A method for producing a copper alloy tube for heat-resistant and high-strength heat exchangers, characterized by obtaining a copper alloy tube having a thickness of 250 N / mm ² or more, an elongation of 40% or more, and an average crystal grain size of 30 μm or less. Furthermore, P: 0.005 thru | or 0.1 weight% is contained, The manufacturing method of the copper alloy tube for heat-resistant high intensity | strength heat exchangers of Claim 8 characterized by the above-mentioned. Furthermore, Zn: 0.01 thru | or 1.0 weight% is contained, The manufacturing method of the copper alloy tube for heat-resistant high intensity | strength heat exchangers of Claim 8 or 9 characterized by the above-mentioned. Furthermore, one or more elements selected from the group consisting of Fe, Ni, Mn, Mg, Cr, Ti and Ag are contained in a total amount of less than 0.07% by mass. The manufacturing method of the copper alloy pipe | tube for heat-resistant high intensity | strength heat exchangers of Claim 1.