JP2011225989A - Copper alloy tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy tube having improved high-temperature ductility and reduced the possibility of cracks during brazing while maintaining high strength.SOLUTION: A copper alloy tube for a heat exchanger contains 0.1 to 1.0 mass% of Sn and 0.005 to 0.1 mass% of P and further contains one or more elements selected from a group of Zr, Ti, and Cr in such a manner that when Zr is contained, the Zr content is 0.0001 to 0.01 mass% and the total content of each element is 0.0001 to 0.1 mass%, wherein the total content of S, Pb, Bi, Se, As, Te, and Sb is regulated to 0.003 mass% or less, the O content is regulated to 0.005 mass% or less, and the H content is regulated to 0.0002 mass% or less. Then, in a section including a tube axis, the average crystal particle size in the direction of the thickness is 30 μm or less and the drawing value at 800°C is 25% or more.

Description

  The present invention relates to a copper alloy tube having excellent resistance to heat cracking during brazing, and more particularly to a copper alloy tube for piping and a copper alloy tube for heat exchanger that are brazed in a state where tensile stress is applied.

  Phosphorus deoxidized copper pipe (JISH3300C1220T) is widely used in room air conditioners, packaged air conditioners, carbon dioxide refrigerant heat pump water heaters, refrigerators, showcases, heat exchangers such as vending machines, and in-machine piping and parts around compressors. It is used.

  For example, in a heat exchanger of a room air conditioner, a U-shaped copper tube bent into a hairpin shape (hereinafter referred to as a copper tube including a copper alloy tube) is passed through a through hole of an aluminum fin, and the copper tube is passed by a jig. By expanding the tube, the copper tube and the aluminum fin are brought into close contact with each other, the open end of the copper tube is expanded, and a copper return bend tube bent into a U-shape is inserted into the expanded portion, and a brazing material such as phosphor copper braze. The heat exchanger is manufactured by joining the expanded pipe part and the return bend pipe by connecting the hairpin-shaped copper pipe and the return bend pipe.

  In addition, in the in-machine piping connecting the compressor and the heat exchanger, a material obtained by arbitrarily bending a copper pipe is prepared, and if necessary, the pipe end is expanded or contracted, and the compressor and the heat exchanger are connected as described above. The room air conditioner is assembled by connecting with in-machine piping with brazing material such as phosphor copper brazing.

  On the other hand, HCFC (hydrochlorofluorocarbon) -based fluorocarbons have been widely used as refrigerants for room air conditioners and the like, but HCFC has a high ozone depletion coefficient, so HFC has a small value from the viewpoint of environmental protection. (Hydrofluorocarbon) fluorocarbons have been used. Furthermore, carbon dioxide, which is a natural refrigerant that is more environmentally friendly than HFC, has been used in heat pump water heaters and vending machines. For example, the design pressure of the refrigerant gas specified in the high pressure gas safety law refrigeration safety rule related example standard is 1.6 MPa in the HCFC R22 when the standard condensation temperature of the high pressure part is 43 ° C. HFC R410A increases to 2.6 MPa and carbon dioxide increases to 8.3 MPa.

  If the design pressure increases, it is necessary to increase the thickness of the copper tube of the heat exchanger or in-machine piping so that it can withstand the strength. However, from the viewpoint of effective use of resources and from the viewpoint of cost, there is a problem with increasing the thickness of the copper tube and increasing the amount of copper used. In order to solve this problem, a high-strength copper tube whose strength is increased by adding Sn, Co, etc., instead of the conventional phosphorous-deoxidized copper tube, has been developed and put on the market. This high-strength copper pipe has higher strength than conventional copper pipes, and accordingly, the thickness can be reduced, and the amount of copper used can be reduced, saving resources and reducing product costs. it can. In addition, this high-strength copper pipe is additionally registered in the Japanese Industrial Standard JISH3300 (July 20, 2009), and is expected as a new material to replace the conventional phosphorous deoxidized copper pipe.

For example, the applicant of the present application described in Patent Document 1 includes Sn: 0.1 to 1.0 mass%, P: 0.005 to 0.1 mass%, O: 0.005 mass% or less, and H: 0.00. A copper tube for a heat exchanger was proposed, which contains 0002 mass% or less, the balance being Cu and inevitable impurities, and an average crystal grain size of 30 μm or less. Further, the applicant of the present application described in Patent Document 2 is Sn: 0.1 to 2.0 mass%, P: 0.005 to 0.1 mass%, S: 0.005 mass% or less, O: 0.0. 005% by mass or less and H: 0.0002% by mass or less, with the balance being composed of Cu and unavoidable impurities, with a tensile strength of 255 N / mm ² or more, A copper alloy tube having an average crystal grain size measured in the direction perpendicular to the thickness direction of 30 μm or less, wherein the tensile strength of the copper alloy tube is αa, the breaking pressure is PFa, the same outer diameter as the copper alloy tube, and A copper alloy tube for a heat exchanger was proposed, where (PFa) / (σa)> (PFd) / (σd) where αd is the tensile strength of the thick phosphorous deoxidized copper tube and PFd is the breaking pressure.

JP 2003-268467 A JP 2008-174785 A

  However, although the copper alloys disclosed in Patent Document 1 and Patent Document 2 achieve their intended purpose and the strength is improved by solid solution strengthening of Sn, the pipes and the like are brazed with phosphor copper brazing. On the other hand (800 to 950 ° C.), if a tensile stress is applied, a crack may occur very rarely.

  As shown in FIG. 1, when the reproduction test was performed under severe conditions (1 group n = 50 and 4 groups were tested), the phosphorous deoxidized copper tube was not cracked and the crack occurrence rate was 0%. The copper alloy tube of Patent Document 1 had a crack generation rate of 4 to 10%. When investigating the ductility of these copper alloy tubes at a high temperature, the copper alloy described in Patent Document 1 or 2 has a lower ductility than that of phosphorous-deoxidized copper at a temperature of 800 ° C. or higher. In a state where a tensile stress is applied, it is impossible to sufficiently deform and it is presumed that cracking has occurred.

  On the other hand, under such special circumstances, measures such as changing the manufacturing process so that tensile stress is not applied or adjusting the thermal power during brazing for each pipe shape are not realistic.

  The present invention has been made in view of such problems, and aims to provide a copper alloy tube that improves high-temperature ductility and reduces the possibility of cracking during brazing while maintaining high strength. To do.

  The copper alloy tube according to the present invention contains Sn: 0.1 to 1.0 mass% and P: 0.005 to 0.1 mass%, and is further selected from the group consisting of Zr, Ti, and Cr. In the case of containing one or more elements, Zr is 0.0001 to 0.01% by mass, the total amount of each element is 0.0001 to 0.1% by mass, and S , Pb, Bi, Se, As, Te, and Sb in a total amount of 0.003 mass% or less, O is regulated to 0.005 mass% or less, H is regulated to 0.0002 mass% or less, and the balance is Cu and A copper alloy tube material having a composition composed of inevitable impurities, and in the cross section including the tube axis, the average crystal grain size in the thickness direction is 30 μm or less, and the drawing value at 800 ° C. is 25% or more. It is characterized by.

  The other copper alloy tube according to the present invention may further include one or more elements selected from the group consisting of Mg, B, Y, Co, Fe, Ni, Al and Si in the above composition. In the case of 0.001 to 0.05 mass% or two or more elements, the total amount of each element is 0.001 to 0.1 mass%.

  Furthermore, another copper alloy tube according to the present invention contains Sn: 0.1 to 1.0% by mass and P: 0.005 to 0.1% by mass, and further Mg, B, Y, Co One or more elements selected from the group consisting of Fe, Ni, Al, and Si are 0.001 to 0.05% by mass in the case of a single element, and the total amount of each element is 0 in the case of two or more elements. 0.001 to 0.1% by mass, S, Pb, Bi, Se, As, Te, and Sb in a total amount of 0.003% by mass or less, O of 0.005% by mass or less, and H of 0 A copper alloy tube material having a composition composed of Cu and inevitable impurities, the balance of which is regulated to 0002 mass% or less, and in the cross section including the tube axis, the average crystal grain size in the thickness direction is 30 μm or less, The aperture value at 800 ° C. is 25% or more.

  Moreover, in the above-mentioned each copper alloy pipe | tube of this invention, Zn: 0.01 thru | or 1.0 mass% can be contained in the said composition.

  Furthermore, each above-mentioned copper alloy tube can be used for a heat exchanger.

  The average crystal grain size is determined by measuring the average crystal grain size in the thickness direction by a cutting method defined in JISH0501 in the cross section including the pipe axis of the copper alloy. It is measured at 10 points at 100 mm intervals in the direction, and the average value is obtained.

  According to the present invention, the strength and toughness are high even at the temperature when brazing with phosphor copper brazing, and the possibility of cracking can be significantly reduced even when a tensile stress is applied during brazing.

It is a schematic diagram which shows the method of a crack test.

  Hereinafter, the present invention will be described in detail. As a result of various experiments and researches by the present inventors to develop a copper alloy tube for a heat exchanger that further improves ductility and toughness (drawing value, elongation) at high temperatures, the Sn content, the P content, It has been found that a copper alloy tube having a further improved drawing value at a high temperature can be obtained by appropriately defining the content of other alloy elements and the average crystal grain size.

  Hereinafter, the reason for adding components and the reason for limiting the numerical values of the composition of the copper alloy tube of the present invention will be described.

“Sn: 0.1 to 1.0 mass%”
Sn improves the tensile strength by solid solution hardening and suppresses the coarsening of crystal grains against the thermal effects of brazing such as phosphor copper brazing, thereby improving the heat resistance of the copper alloy tube. However, it has been found that when heated at high temperatures, the Sn-containing alloy shows a decrease in ductility at high temperatures as the Sn content increases. The mechanism by which Sn lowers the high temperature ductility is not clear, but it seems that cracking has occurred by reducing the strength or ductility of the grain boundaries at or near the grain boundaries at high temperatures. When the Sn content exceeds 1.0% by mass, the ductility drop at high temperatures becomes large, and solidification segregation in the ingot becomes severe, and segregation is not completely eliminated by normal hot extrusion and / or processing heat treatment. In some cases, the structure, mechanical properties, bending workability of the copper alloy tube, unevenness of the structure and mechanical properties after brazing, deterioration of corrosion resistance, and the like are caused. Moreover, when Sn content exceeds 1.0 mass%, a required extrusion pressure will become high, and when it is going to extrude with the same extrusion pressure as a copper alloy whose Sn content is 1.0 mass% or less, extrusion temperature , Thereby increasing the surface oxidation of the extruded material, reducing the productivity and increasing the surface defects of the copper alloy tube. Further, when the Sn content in the copper alloy of the present invention is less than 0.1% by mass, it becomes impossible to obtain sufficient tensile strength and fine crystal grain size after annealing and brazing heating. The effect of suppressing strength reduction during brazing heating with copper brazing and the like and the effect of preventing grain coarsening will be insufficient. Therefore, it is necessary that the Sn content be 0.1 to 1.0 mass%.

“P: 0.005 to 0.1 mass%”
P, like Sn, reduces the hot ductility of the copper alloy tube, and promotes the reduction of hot ductility due to Sn. When the P content exceeds 0.1% by mass, the ductility drop of the copper alloy of the present invention becomes particularly high, the electrical conductivity is lowered, and hot workability and cold workability are hindered. . 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 tends to decrease. Therefore, it is necessary to make the P content 0.005 to 0.1% by mass.

“One or more elements selected from the group consisting of Zr, Ti, and Cr: 0.0001 to 0.1% by mass in total of each element, provided that Zr is 0. 0001 to 0.01% by mass "
As described above, the ductility of a copper alloy tube containing Sn and P decreases at a high temperature of 800 ° C. or higher. Although the mechanism is not clear, the inclusion of Zr dramatically restores ductility at high temperatures. Even if the Zr content is about 0.0001% by mass, the effect of improving the ductility of the copper alloy tube at a high temperature can be obtained. However, Zr is very easy to oxidize, and if the Zr content exceeds 0.01% by mass, the oxide scale is involved in casting, causing cracks during hot extrusion. If Zr is less than 0.0001% by mass, the effect of ductility recovery is insufficient. Therefore, the Zr content is set to 0.0001 to 0.01% by mass.

  Ti and Cr also have the same effect as Zr. When the content of Ti and Cr alone or in total exceeds 0.1% by mass, the strength becomes too high and the elongation decreases, which adversely affects extrudability and workability. In addition, when the content of Ti and Cr in the copper alloy tube of the present invention is less than 0.0001% by mass, the improvement in ductility at high temperatures becomes insufficient. Accordingly, the content of Ti and Cr is 0.0001 to 0.1% by mass alone or in total. When Zr is contained, the total amount of Zr, Ti, and Cr is 0.0001 to 0.1% by mass.

“S, Pb, Bi, Se, As, Te, and Sb in a total amount of 0.003 mass% or less”
S, Pb, Bi, Se, As, Te, and Sb are all not easily dissolved, but are easily concentrated at the grain boundary. Since each element has a low melting point, the strength of the grain boundary is significantly reduced. The ductility at high temperature of the copper alloy of this invention is reduced. S is present in the matrix by forming a compound with Cu in the copper alloy of the present invention. When the S content increases, ingot cracking during casting and hot extrusion cracking in the hot extrusion process increase. Also, even if hot extrusion cracking does not occur, when the extruded material is cold-rolled and drawn, the Cu-S compound inside the material expands in the axial direction of the tube and cracks occur at the interface of the Cu-S compound. In the product during and after the product processing, surface flaws, cracks, etc. occur and the product yield is reduced. Moreover, even when a crack does not generate | occur | produce at a Cu-S compound interface, when bending the copper alloy pipe | tube of this invention, it becomes a starting point of a crack generation and the frequency that a crack generate | occur | produces in a bending part becomes high.

  Similarly, when the content of Pb, Bi, Se, As, Te, and Sb increases, ingot cracking during casting and hot extrusion cracking in the hot extrusion process occur, and during and after product processing. In the product, surface flaws and cracks occur, and the yield of the product is reduced. In order to improve such problems, the total content of S, Pb, Bi, Se, As, Te, and Sb in the copper alloy of the present invention is 0.003% by mass or less, preferably 0.002% by mass. In the following, it is more desirable to regulate the content to 0.001% by mass or less. Regarding S, it is further preferable to regulate the content to 0.0015% by mass or less, and further to 0.0010% by mass or less.

  S is relatively easy from copper bullion and 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 make the S content 0.0015% by mass or less because it is taken into the molten metal, the amount of low-grade Cu ingots and scrap is reduced, the SOx gas in the melting atmosphere is reduced, and an appropriate furnace It is effective to select a material and add a trace amount of an element having strong affinity for S, such as Mg and Ca, to the molten metal.

“O: 0.005 mass% or less (50 ppm or less)”
In the copper alloy tube of the present invention, Zr and Ti are added as elements to suppress oxidation, and Mg and B, which will be described later, are selectively added. When these elements are oxidized, these elements depend on the elements. The effect of inhibiting oxidation disappears. When the O content exceeds 0.005 mass%, the oxides of Cu and Sn are caught in the ingot, the soundness of the ingot is lowered, and the bending workability of the manufactured pipe is easily lowered. . On the other hand, if the O content exceeds 0.005% by mass, the risk of hydrogen embrittlement increases. 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 (2 ppm or less)”
When more hydrogen is taken into the molten metal at the time of melting and casting, the hydrogen collects at the grain boundary, and it becomes easy to promote a decrease in ductility at high temperatures. Further, when the amount of hydrogen taken into the molten metal increases, pinholes are likely to be generated, and when hydrogen is concentrated in the grain boundary and present in the ingot, cracks during hot extrusion are likely to occur. If hydrogen is excessive, blistering due to hydrogen tends to occur at the grain boundaries during annealing even after extrusion, resulting in a decrease in product yield. 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, the raw material at the time of melting and casting is dried, the molten metal is heated red, and the dew point of the atmosphere in contact with the molten metal is kept low. It is effective to take measures such as making the molten metal before adding phosphorus and oxidizing.

“Crystal grain size: average crystal grain size is 30 μm or less”
The grain size plays an important role in the strength of the material and workability such as bending. Generally, if the crystal grain size is small, the strength is high and the bending workability is improved. When the crystal grain size is large, the strength is lowered. 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. Therefore, the average crystal grain size is preferably 30 μm or less, more preferably 15 μm or less.

  In a state where tensile stress is applied at a high temperature, a smaller crystal grain size is advantageous for suppressing a decrease in hot ductility. In the alloy of the present invention, the crystal grain size after heating at 800 ° C. for 10 minutes is desirably 70 μm or less.

“Aperture value at 800 ° C is 25% or more”
It has been found that if the drawing value at 800 ° C. corresponding to the hard brazing temperature is less than 25%, there is a risk of cracking when a tensile stress is applied during brazing. For this reason, the aperture value at 800 ° C. needs to be 25% or more. It is more desirable that the aperture value at 900 ° C. is 25% or more and the aperture value at 950 ° C. is 20% or more. When a copper alloy tube is brazed as a pipe of a heat exchanger, it is usually brazed with a tensile stress applied. At this time, since the drawn value at 800 ° C. of the copper alloy tube of the present invention is 25% or more, the ductility at high temperature is extremely excellent, and even when stress is applied during brazing at 800 to 950 ° C. , Can prevent cracking. The term “drawing” refers to a ratio obtained by dividing the cross-sectional area of the fractured portion after the tensile test of the pipe by the cross-sectional area before the test. The higher this value, the higher the ductility.

“Selectively contains one or more elements selected from the group consisting of Mg, B, Y, Co, Fe, Ni, Al and Si: the content is 0.001 to 0.05 mass%, two kinds In the case of the above elements, the total amount of each element is 0.001 to 0.1 mass%. "
In the copper alloy pipe of the present invention, by containing appropriate amounts of Mg, B, Y, Co, Fe, Ni, Al and Si, the drawing value and elongation at high temperature are improved, and cracking during brazing is prevented. can do. Compared to the aforementioned Zr, Ti and Cr, the effects of crack suppression and ductility recovery at high temperatures are slightly inferior, and in order to obtain a sufficient effect, the content must be increased, but the above Mg, B, Y By adding Co, Fe, Ni, Al and Si, the effect of suppressing cracking at high temperature and recovering ductility can be obtained.

  As for each selected element, when its content exceeds 0.05 mass%, productivity is hindered due to a decrease in extrudability, and cracks and the like are generated during processing. Accordingly, the individual content of each selected element needs to be 0.05% by mass or less. When there are two or more selected elements, the total amount can be up to 0.1 mass.

  On the other hand, when the content of each selected element is less than 0.001% by mass, improvement of the drawing is not observed. For this reason, when adding each element, it is necessary to contain 0.001 mass% or more. Even when two or more types are added in combination, the minimum content is 0.001% by mass in total.

“Zn: 0.01 to 1.0 mass%”
By containing 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 inclusion 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., reducing production costs. Contribute.

  In addition, by including Zn, in the heat exchanger assembly process, the wear of the mandrel during the hairpin bending process of the copper alloy tube, and the copper alloy tube is inserted into the opening of the aluminum fin to expand the copper alloy tube. Thus, the wear of the expanded burette during the expansion process when the copper alloy tube is brought into close contact with the fin can be reduced. Furthermore, Zn is effective in suppressing the penetration of hydrogen into the molten metal during casting.

  If the Zn content exceeds 1.0% by mass, the tool wear suppression effect and the hydrogen penetration suppression effect are saturated. Further, when the Zn content is less than 0.01% by mass, the above-described effects are not sufficient. Therefore, when adding Zn, it is necessary to make the Zn content 0.01 to 1.0 mass%.

  Hereinafter, an example of the manufacturing method of the copper alloy pipe of the present invention will be described. The manufacturing method shown below is for a smooth tube, but in the case of an internally grooved tube, a well-known internal grooved process is added.

  First, the raw electrolytic copper is dissolved under the charcoal coating. After the copper is dissolved, a predetermined amount of Sn and necessary additive elements are added, and further, deoxidation is performed with a Cu-15 mass% P intermediate alloy. Add P. At this time, it is desirable that an additive element such as Zr that is easily oxidized be added as an intermediate alloy in order to add a predetermined amount uniformly and appropriately. After the component adjustment is completed, a billet having a predetermined size is produced by semi-continuous casting. The obtained billet is heated in a heating furnace and homogenized. Prior to hot extrusion, the billet is held at 750 to 950 ° C. for about 1 minute to 2 hours to improve segregation by homogenization. Thereafter, the billet is perforated by piercing and hot extruded at 750-950 ° C.

  In order to manufacture the copper alloy pipe of the present invention, it is essential to eliminate Sn segregation and to refine the structure of the product pipe. For this reason, the cross-sectional reduction rate by hot extrusion is 88% or more, preferably 93% or more, and the raw tube after hot extrusion is cooled to a surface temperature of 300 ° C. by a method such as water cooling. It is preferable to cool so that the speed is 10 ° C./second or more, desirably 15 ° C./second or more, and more desirably 20 ° C./second or more. However, the cross-sectional reduction rate is determined as [drilled billet donut area-cross-sectional area of raw tube after hot extrusion] / [drilled billet donut area] × 100%.

  Thereafter, the extruded element tube is rolled. By setting the processing rate at this time to 92% or less in terms of the cross-section reduction rate, product defects during rolling can be reduced. Subsequently, the rolling raw tube is subjected to a drawing process to manufacture a raw tube having a predetermined size. Usually, drawing is performed using a plurality of drawing machines, but surface defects and internal cracks in the raw pipe can be reduced by reducing the processing rate (cross-sectional reduction rate) by each drawing machine to 35% or less. .

  If necessary, the drawing tube is annealed. In order to manufacture the copper alloy tube of the present invention, the body temperature of the drawing tube is heated to 400 to 700 ° C. by continuous annealing with a roller hearth furnace, and the temperature is maintained for about 10 minutes to 1 hour. It is desirable to anneal. Moreover, it is desirable to heat so that 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. In place of the continuous annealing by the roller hearth furnace, a high-frequency induction heating furnace may be used to perform rapid heating, rapid cooling, and short-time heating annealing.

  Next, the effect of the Example of the copper alloy of this invention is demonstrated compared with the comparative example which remove | deviates from the scope of the present invention.

"First test example"
First, a first test example of the present invention will be described. This test example is for the copper alloy tube of claim 1. In order to obtain the copper alloy materials of the compositions of Examples A1 to A61 and Comparative Examples A1 to A23 and Conventional Example A1 having the compositions shown in Tables 1 to 6 below, vacuum melting furnaces or charcoal were used as small amounts of test materials, respectively. A 7 kg copper alloy billet was cast by coating. Further, each billet was processed into a cake-like block having a length of 50 mm, a width of 50 mm, and a length of 300 mm by hot forging at a temperature of 700 to 900 ° C. Further, each block was chamfered and bored to produce a cylindrical billet having a diameter of 40 mm, a thickness of 5 mm, and a length of 300 mm. Next, each billet was rolled to finally produce a tube having an outer diameter of 9.52 mm, a wall thickness of 0.80 mm, and a length of 300 mm. Thereafter, these tubes were annealed at a temperature of 400 to 700 ° C. and subjected to an evaluation test.

  In the evaluation test, the temperature was raised from room temperature to 800 ° C., 900 ° C. and 950 ° C. in 15 minutes, and held at each temperature for 10 minutes. The elongation and the drawing value were measured. The tensile strength, elongation and drawing value were calculated based on the definitions described in JISZ2241. The drawing after high-temperature tension is {(cross-sectional area of the tube before the tensile test−cross-sectional area of the fractured surface after the tensile fracture) / (cross-sectional area of the pipe before the tensile test)} × 100%, The subsequent cross-sectional area was calculated by measuring the outer diameter and thickness of the fracture surface. Further, as a crack test for simulating brazing in a state where a tensile stress was applied, a fixed load crack test shown in FIG. 1 was performed. That is, a stainless steel pipe 2 having an outer diameter of 11 mm and an inner diameter of 9.8 mm is fixed to the fixing base 1 with its axial direction horizontal, and the outer diameter is 9.52 mm as described above. A test tube 3 having a wall thickness of 0.80 mm and a length of 300 mm was inserted. The insertion length of the test tube 3 was 150 mm. As shown in FIG. 1, a 1 kg weight 4 was attached to a position 50 mm from the end of the 150 mm portion protruding from the tube 2. Then, the portion of the test tube 3 in the vicinity of the tube 2 was heated to about 900 ° C. by the acetylene oxygen burner 5. The distance between the acetylene oxygen burner and the tube 2 was 5 cm. A K thermocouple was spot welded to the position where the acetylene oxygen burner hits, and the temperature of the test tube during heating was measured. Heating with an acetylene oxygen burner was adjusted to 900 ° C. in 8 to 12 seconds after heating. The weight 4 applies a tensile stress of about 20 MPa to the test tube in the heating portion of the test tube 3.

  Tables 1 to 4 below show compositions of Examples A1 to A61 of the present invention, and Tables 5 and 6 show compositions of Comparative Examples A1 to A23 of the present invention and Conventional Example A1. Tables 7 and 8 show the measured values of the crystal grain sizes and high-temperature tensile tests (drawings) of Examples A1 to A61 of the present invention and the test results of the crack test, and Table 9 shows comparative examples of the present invention. The crystal grain size of A1 to A23 and the conventional example A1, the measured value of the high temperature tensile test (drawing), and the test result of the crack test are shown.

  As described in Table 7 and Table 8, in Examples A1 to A61 of the present invention, no crack occurred in the crack test. On the other hand, as shown in Table 9, Comparative Examples A1, A3, A5, A7, A9, A11, A13 lack the content of the third element such as Zr, and Conventional Example A1 contains the third element. There was no cracking. In Comparative Example A16, the Sn content was as high as 1.2% by mass, and the reduction in ductility at high temperatures could not be suppressed by the addition of the third element, so that the drawing value at 800 ° C. was as low as 18% and cracking occurred. Comparative Example A20 had a large amount of Sn, and the aperture value at 800 ° C. was as low as 19%, so cracking occurred. Comparative Example A4 is good in terms of ductility at high temperature, cracking test, and coarsening of the crystal grain size, but since Ti is large, the strength at room temperature is large and the elongation is small. In addition, a large force is required, and the bending radius that can be bent without causing cracks in the tube has increased. Further, in Comparative Example A4, since melting casting was performed with charcoal coating, the surface flaws of the pipe, which seem to be caused by Ti oxide generated during melting casting, occurred. For this reason, the surface defects reduce yield, pressure resistance, corrosion resistance, tube manufacturing yield, and the like. Comparative Example A6 is good in terms of ductility at high temperature, cracking test, and coarsening of the crystal grain size, but because of the large amount of Cr, the amount of pushing force increases, making extrusion difficult and the extrusion temperature must be increased. The surface wrinkles increased. Therefore, as in Comparative Example A4, the yield, pressure resistance, corrosion resistance, tube manufacturing yield, and the like decrease. Comparative Examples A2, A8, A12, and A14 are good in terms of ductility at high temperature, cracking test, and coarsening of crystal grain size, but since Zr is large, melting casting was performed with charcoal coating. Entrapment of Zr oxide occurred in the lump, and surface flaws of the tube that seemed to be caused by Zr oxide occurred. For this reason, the surface defects reduce yield, pressure resistance, corrosion resistance, tube manufacturing yield, and the like. In Comparative Examples A17 to A20, the Sn and P contents were out of the scope of the present invention, so the average crystal grain size was out of the scope of the present invention, and the strength was insufficient. Since Comparative Example A23 has a large amount of Zn, the time cracking test defined in JISH3300 was conducted. As a result, the holding time until cracking occurred was 2 / compared with Example A2 in which the Sn, P, and Zr contents were equal. It became 3 or less.

In Comparative Example A10, the total amount of Ti and Cr exceeded 0.1% by mass, so the extrudability was poor. In Comparative Example A15, Sn was less than 0.1% by mass, and the effect of suppressing crystal grain growth by heating was insufficient, so the average crystal grain size was large and the strength was insufficient. In Comparative Example A21, Pb exceeded the range of the present invention, so that cracking occurred. Comparative Example A22 was hydrogen embrittled because O exceeded the scope of the present invention. That is, after holding at 850 ° C. for 30 minutes in an H ₂ air stream, a tensile test was performed, and the specimen broke without substantially extending immediately after the start of loading.

"Second test example"
Next, a second test example of the present invention will be described. This test example relates to the invention according to claim 2. That is, this test example contains one or more elements selected from the group consisting of Zr, Ti, and Cr, and includes Mg, B, Y, Co, Fe, Ni, Al, and Si. It contains one or more elements selected from the group. In the production of the test material, the other conditions were the same as in the first test example, except that the material was coated with charcoal and melted to produce a 7 kg ingot. Moreover, this test example differs only in the composition of the copper alloy tube, and other test conditions are the same as those of the first test example.

  Tables 10 to 15 below show the compositions of Examples B1 to B83 of the present invention, and Tables 16 and 17 show the compositions of Comparative Examples B1 to B14 of the present invention and Conventional Example B1. Tables 18 to 20 show measured values of crystal grain sizes and high-temperature tensile tests (drawings) of Examples B1 to B83 of the present invention, and test results of crack tests. Table 21 shows comparative examples of the present invention. The measured values of the crystal grain size and high-temperature tensile test (drawing) of B1 to B14 and Conventional Example B1 and the test results of the crack test are shown.

As described in Table 18 and Table 20, in Examples B1 to B83 of the present invention, no crack occurred in the crack test. On the other hand, as shown in Table 21, Comparative Examples B1 and B3 lacked the content of the third element such as Zr, and Conventional Example B1 did not contain the third element. In Comparative Example B6, Sn was abundant and the drawing value at 800 ° C. was as low as 18%, so cracking occurred. In Comparative Example B10, Sn and P were abundant, and the drawing value at 800 ° C. was as low as 19%, so cracking occurred. Comparative Example B2 is good in terms of ductility at high temperature, cracking test, and coarsening of the crystal grain size, but because the amount of Zr is too large, the strength at room temperature is large and the elongation is small, so bending workability In this case, a large force is required, and the bending radius that can be bent without causing cracks in the tube has increased. Moreover, the surface flaw of the pipe | tube considered to be attributed to the Zr oxide generated at the time of melt casting occurred. For this reason, the surface defects reduce the yield, pressure resistance, corrosion resistance, tube manufacturing yield, and the like. Since Comparative Example B4 has a lot of Y, it is good in terms of ductility at high temperature, cracking test, and coarsening of crystal grain size as in Comparative Example B2, but the strength at room temperature is large and the elongation is small. In bending workability, a large force is required, and the bending radius that can be bent without causing cracks in the pipe has increased. Since Comparative Example B5 has a large average crystal grain size, it does not satisfy the function as a high-strength copper tube that is an object of the present invention. In Comparative Examples B7 and B9, the amount of P was small and the average grain boundary was large. Therefore, deoxidation was insufficient at the time of casting, and oxides of additive elements were generated. Since Comparative Example B8 contained a large amount of P, cracks were generated during hot forging, and no subsequent test was performed. Since Comparative Example B11 contained a large amount of Bi, cracks occurred during hot forging, and therefore no subsequent test was performed. Comparative Example B12 showed hydrogen embrittlement due to the large amount of O. That is, when a tensile test was carried out after holding at 850 ° C. for 30 minutes in an H ₂ air stream, it broke almost without elongation immediately after the start of load application. Since Comparative Example B13 contained a large amount of H, cracks occurred during hot forging, so no subsequent test was performed. Comparative Example B14 is good in terms of ductility at high temperature, cracking test, and coarsening of crystal grain size, but because of the large amount of Zn, the time cracking test specified in JIS 3300 was conducted. As a result, Sn, P, Zr Compared to Example B14 having the same content, the holding time until cracking was ½ or less.

"Third test example"
Next, a third test example of the present invention will be described. This test example is for claim 3. That is, instead of one or more elements selected from the group consisting of the third elements Zr, Ti, and Cr in the first test example, Mg, B, Y, Co, Fe, Ni, Al, and One or more elements selected from the group consisting of Si are added. The production conditions of the test material are the same as in the second test example. Moreover, this test example differs only in the composition of the copper alloy tube, and other test conditions are the same as those of the first test example.

  Tables 22 to 23 below show the compositions of Examples C1 to C27 of the present invention, and Tables 24 and 25 show the compositions of Comparative Examples C1 to C11 of the present invention and Conventional Example C1. Table 26 shows the measured values of the crystal grain size and high-temperature tensile test (drawing) of Examples C1 to C27 of the present invention and the test results of the crack test. Table 27 shows Comparative Examples C1 to C11 of the present invention. In addition, the crystal grain size and the measurement value of the high-temperature tensile test (drawing) of Conventional Example C1 and the test result of the crack test are shown.

  As described in Table 26, in Examples C1 to C27 of the present invention, no crack was generated in the crack test. On the other hand, as shown in Table 27, Comparative Examples C1 to C3 lacked the content of the third element such as Mg, and Conventional Example C1 did not contain the third element. In Comparative Example C4, cracks occurred because of a large amount of Sn. In Comparative Example C7, since Sn and P were abundant, cracking occurred. In Comparative Example C5, since there was little P, deoxidation was insufficient during casting, oxides of additive elements were generated, and the bending workability of the tube was lowered. Since Comparative Example C6 has a small amount of Sn and P, it does not satisfy the function as a high-strength copper tube that is an object of the present invention. Since Comparative Example C8 contained a large amount of Te, cracks were generated during hot forging, and therefore no subsequent test was performed. Comparative Example C9 showed hydrogen embrittlement due to the large amount of O. Since Comparative Example C10 contained a large amount of H, cracks were generated during hot forging, so no subsequent test was performed. Since Comparative Example C11 has a large amount of Zn, the time cracking test specified in JIS 3300 was conducted. As a result, the holding time until cracking was halved compared to Example C14 having the same Sn, P, and Zr contents. It became the following.

"4th example"
Next, as a fourth test example of the present invention, a result of a test performed on an actual factory production line will be described. Test pipes having the above-mentioned sizes were collected from copper alloy pipes manufactured by actual machines, and tests similar to those described above were performed. The test results are shown in Table 4 below.

  As shown in Table 30, Examples D1 and D2 were not cracked in the crack test, and Comparative Example D1 was cracked because the amounts of Zr and Mg were small. Since Conventional Example D1 did not contain Zr, Mg, or the like, cracks occurred in the crack test.

1: Fixing base 2: Tube 3: Test tube 4: Weight 5: Acetylene oxygen burner

Claims (5)

Sn: 0.1 to 1.0% by mass and P: 0.005 to 0.1% by mass, and one or more elements selected from the group consisting of Zr, Ti, and Cr When Zr is contained, Zr is 0.0001 to 0.01% by mass, the total amount of each element is 0.0001 to 0.1% by mass, and S, Pb, Bi, Se, As, Te and Sb are total amounts of 0.003% by mass or less, O is controlled to 0.005% by mass or less, H is controlled to 0.0002% by mass or less, and the remainder has a composition consisting of Cu and inevitable impurities A copper alloy tube, characterized by having an average crystal grain size in the thickness direction of 30 μm or less and a drawing value at 800 ° C. of 25% or more in a cross-section including a tube axis. One or more elements selected from the group consisting of Mg, B, Y, Co, Fe, Ni, Al, and Si, 0.001 to 0.05 mass% when used alone, or two or more elements The copper alloy tube according to claim 1, wherein 0.001 to 0.1% by mass is contained in a total amount of each element. Sn: 0.1 to 1.0% by mass and P: 0.005 to 0.1% by mass, and further selected from the group consisting of Mg, B, Y, Co, Fe, Ni, Al and Si In the case of a single element, 0.001 to 0.05% by mass, and in the case of two or more elements, the total amount of each element is 0.001 to 0.1% by mass. The total amount of Pb, Bi, Se, As, Te, and Sb is 0.003% by mass or less, O is 0.005% by mass or less, H is 0.0002% by mass or less, and the balance is Cu and inevitable. A copper alloy tube material having a composition composed of mechanical impurities, wherein in the cross section including the tube axis, the average crystal grain size in the thickness direction is 30 μm or less, and the drawing value at 800 ° C. is 25% or more. Features copper alloy tube. The copper alloy tube according to any one of claims 1 to 3, wherein Zn: 0.01 to 1.0 mass% is contained. The copper alloy tube according to any one of claims 1 to 4, wherein the copper alloy tube is used in a heat exchanger.

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