JP4817693B2 - Copper alloy tube for heat exchanger and manufacturing method thereof - Google Patents

Description

  The present invention relates to a method for producing a copper alloy tube used in a heat exchanger such as an air conditioner and a large air conditioner, and in particular, heat exchange with excellent 0.2% proof stress and fatigue strength before and after brazing heating. The present invention relates to a copper alloy tube for use in a machine and a manufacturing method thereof.

  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. In this way, the copper pipe and the aluminum fin are brought into close contact with each other, and the open end of the copper pipe is subjected to secondary expansion and tertiary expansion, and a copper pipe (return bend pipe) bent into a U-shape is inserted into the expansion section. It is manufactured by brazing a copper tube to the expanded portion with phosphor copper brazing.

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

  Phosphor copper brazing (BCuP-2: Cu-0.68 to 0.75 mass% P) used for assembling the heat exchanger as described above has a melting point of 805 ° C. (liquidus temperature), and brazing The part is heated to a temperature of 800 ° C. or higher for several seconds to several tens of seconds. For this reason, the brazed part and the phosphorous deoxidized copper pipe in the vicinity thereof are in a state in which the crystal grains become coarser than the other parts, and the strength is reduced due to softening.

  By the way, HCFC (hydrochlorofluorocarbon) chlorofluorocarbon has been widely used as a heat medium (refrigerant) used in a heat exchanger such as an air conditioner. However, HFC (hydrofluorocarbon) -based chlorofluorocarbon has been used as an alternative refrigerant for HCFC-based chlorofluorocarbon because of the concern about the destruction of the ozone layer by chlorofluorocarbon. To maintain the same heat transfer performance as when HCFC-based fluorocarbons are used in heat exchangers that use HFC-based fluorocarbons such as R407C, the condensing pressure during operation should be 1.5 times that of HCFC-based fluorocarbons. It needs to be bigger.

  Moreover, in order to reduce the manufacturing cost of an air conditioner, the request | requirement of mass reduction is increasing with respect to the copper pipe which is a heat exchanger tube, and the thinning of a copper pipe is progressing. Along with the thinning of the copper pipe, the phosphorus deoxidized copper pipe that has been used conventionally has a problem of low fatigue strength. In addition, since a larger pressure acts on the in-machine piping of such a heat exchanger, the copper pipes used for the in-machine piping are more demanding for strength and fatigue strength.

  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 is made of Cu and inevitable impurities, and the oxygen of the impurities is 50 ppm or less, and an electric resistance welded copper alloy tube for heat exchanger has been proposed (Patent Document 1). Further, Fe: 0.005 to 0.8 mass%, P: 0.01 to 0.026 mass%, Zr: 0.005 to 0.3 mass%, and O: 3 to 30 ppm, with the balance being Cu. In addition, a seamless copper alloy tube for a heat exchanger having a composition composed of inevitable impurities has also been proposed (Patent Document 2).

  On the other hand, as a method for manufacturing a copper alloy base tube, a method in which a cylindrical ingot is manufactured by melt casting, cut into a predetermined length, and then hot extruded is widely used. Prior to this hot extrusion, the billet is heated to a predetermined temperature, and after extrusion, the blank tube is cooled by underwater extrusion or water-cooled extrusion. And an extrusion element pipe becomes a copper alloy pipe for heat exchangers through a rolling process, a drawing process, an annealing process (if needed), and also through an inner surface grooving process as needed.

  However, the above-described conventional copper alloy tube has improved strength and fatigue strength due to precipitation of Co phosphide or Zr. In order to give such a precipitation-type copper alloy the desired strength and fatigue strength, it is possible to control the heat treatment conditions such as quenching, heating temperature and heating rate within a narrow range in the copper alloy tube manufacturing process. As the above-mentioned variations in manufacturing conditions lead to instability in the characteristics of the copper alloy tubes to be manufactured, new production facilities have been remodeled and newly installed so that variations in heating temperature and heating speed will not occur. There is a problem that investment is required.

  In addition, the precipitation type copper alloy has excellent heat resistance when heated to about 600 ° C., but the precipitates dissolve in high temperature under brazing conditions, and the crystal grains grow rapidly. In addition, the decrease in fatigue strength may be larger than in a solid solution type copper alloy. For this reason, in the assembled heat exchanger, the target yield strength and fatigue strength cannot be maintained.

  Furthermore, in the method for producing a copper alloy tube, if the heating and cooling conditions for extrusion are unstable, it causes coarsening of crystal grains of the extruded raw tube and entrapment of oxides and the like.

  Therefore, the inventors of the present application have already proposed a copper alloy tube and a method for manufacturing the copper alloy tube that eliminate such drawbacks of the conventional copper alloy tube (Patent Document 3 and Patent Document 4).

JP 2000-199023 A Japanese Patent Publication No.58-39900 JP 2003-268467 A JP 2004-292917 A

  However, in the copper alloy pipe and the manufacturing method thereof described in Patent Documents 3 and 4, although the intended purpose has been achieved, the recent demand for further improvement in the proof stress and strength has been met. Absent.

  The present invention has been made in view of such problems, and provides a copper alloy tube for a heat exchanger excellent in brazability, proof stress before brazing heating and after brazing heating, and fatigue strength, and the copper. To provide a method for producing a copper alloy tube for a heat exchanger capable of producing an alloy tube without causing the occurrence of entrapment, cracking or breakage of an oxide or the like and without causing coarsening of crystal grains. Objective.

The copper alloy tube for a heat exchanger according to the present invention has Sn: 0.1 to 1.0 mass%, P: 0.005 to 0.1 mass%, Fe: 0.035 to 0.1 mass%, O: 0.005% by mass or less and H: 0.0002% by mass or less, with the balance being composed of Cu and inevitable impurities, an average crystal grain size of 30 μm or less, and a 0.2% proof stress of 95 Or 200 N / mm ² .

In this case, the copper alloy tube for a heat exchanger can further contain Zn: 0.01 to 1.0% by mass. Further, the copper alloy tube for a heat exchanger is, for example, an internally grooved tube having a plurality of spiral grooves formed on the inner surface of the tube and a plurality of fins formed between the adjacent spiral grooves. The copper alloy tube for an exchanger has an average crystal grain size of 100 μm or less after heating at 850 ° C. for 30 seconds, a 0.2% proof stress of 40 N / mm ² or more, and a repeated stress n of 92 MPa in a fatigue test. = 10 ⁷ It is preferable to have a fatigue strength that does not break after ⁷ times.

The method for producing a copper alloy tube for a heat exchanger according to the present invention includes Sn: 0.1 to 1.0% by mass, P: 0.005 to 0.1% by mass, Fe: 0.035 to 0.1% by mass. , O: 0.005% by mass or less and H: 0.0002% by mass or less, and the billet having a composition composed of Cu and inevitable impurities is heated to 750 to 1000 ° C. and hot extruded. Then, by cooling with water from a temperature of 750 ° C. or higher, cooling is performed so that the average cooling rate up to 100 ° C. is 1.5 ° C./second or more. Thereafter, rolling with a processing rate of 92% or less and one drawing There at least once rows drawing processing working ratio is less 40% in the processing, then, by heated 5 to 20 minutes at a temperature of 450 to 700 ° C. for annealing, 0.2% proof stress of 95 to 200 N / obtaining a copper alloy tube of mm ² And wherein the door.

The billet may further contain Zn: 0.01 to 1.0% by mass .

A method of manufacturing a copper alloy tube for a heat exchanger of the above, for example, between the drawing process and the annealing process, the drawing processing after inner grooved tube by facilities grooving the inner surface of the copper alloy tube of The grooving step includes arranging a floating plug in the pipe and a grooved plug connected to the floating plug via a connecting shaft and rotatable about the connecting shaft, and Engaging the reduced-diameter die with the grooved plug positioned at a position where at least one rolled ball is disposed along the circumferential direction of the tube; The process of pressing the plug into the diameter reducing die and the rolled ball sequentially reduces the diameter of the element pipe, and transferring the groove shape to the inner surface of the element pipe, and reducing the diameter of the element tube having the groove transferred to the inner surface by the shaping die. To process That having a and extent.

  In addition, the average crystal grain size is determined by measuring the average crystal grain size in the thickness direction with respect to a cross section parallel to the axial direction of the copper alloy tube by a cutting method defined in JISH0501, and measuring the average crystal grain size in the tube axis direction. The average was measured as the average crystal grain size. The 0.2% proof stress was determined according to JISZ2241. The fatigue strength was determined using a fatigue test method based on JISZ2273.

  ADVANTAGE OF THE INVENTION According to this invention, the copper alloy pipe | tube excellent in brazing property, the proof stress before brazing heating, and the proof stress and fatigue strength after brazing heating is obtained. In addition, according to the production method of the present invention, it is possible to produce a copper alloy tube without occurrence of entrainment of oxides, cracks or breakage, and without occurrence of coarsening of crystal grains.

  Hereinafter, the present invention will be described in detail. As a result of various experimental studies by the present inventors to develop a copper alloy tube for heat exchangers with excellent brazeability, yield strength after brazing heating and fatigue strength, the Sn content, the P content, By appropriately specifying the Fe content, oxygen content, hydrogen content, and average crystal grain size, it is possible to obtain a copper alloy tube having excellent brazeability, yield strength after brazing heating and fatigue strength. I found it.

  Hereinafter, the reasons for limiting the composition and content of the copper alloy tube of the present invention will be described.

Sn (tin): 0.1 to 1.0% by mass
If Sn is contained in an amount of more than 1.0% by mass, solidification segregation in the ingot becomes severe and deformation resistance during extrusion increases. This segregation in the ingot is not sufficiently eliminated even in the product, and the structure of the product pipe becomes non-uniform. Due to this non-uniform structure, mechanical properties and corrosion resistance are liable to occur. In order to eliminate the solidification segregation and to make the extrusion conditions capable of reducing the deformation resistance at the time of extrusion, the hot extrusion conditions according to claim 5 are insufficient, and the heating temperature and / or heating before the hot extrusion. It is necessary to increase the time, which increases the production cost. Moreover, when there is more content of Sn than 1.0 mass%, the wet-spreading property of wax will also fall. Therefore, the Sn content is 1.0% by mass or less.

  On the other hand, if Sn is less than 0.1% by mass, the 0.2% proof stress and fatigue strength after brazing heating will be insufficient. For this reason, Sn is contained by 0.1 mass% or more. Therefore, the Sn content is 0.1 to 1.0 mass%.

P (phosphorus): 0.005 to 0.1% by mass
When P added for the main purpose of deoxidation is contained in an amount of more than 0.1% by mass, cracking is likely to occur during hot extrusion, and the susceptibility to stress corrosion cracking is increased, thereby improving the reliability as a heat exchanger. Reduce. On the other hand, when P is less than 0.005% by mass, a large amount of Sn oxide is generated due to insufficient deoxidation, which reduces the soundness of the ingot and causes entrainment during hot extrusion, Inter-extrusion itself becomes difficult. Therefore, the P content is set to 0.005 to 0.1 mass%.

Fe (iron): 0.035 to 0.1% by mass
Fe improves the yield strength of the copper alloy by precipitation hardening . In order to obtain the effect of improving the proof stress, the Fe content is set to 0.035 % by mass or more. On the other hand, when Fe is added in excess of 0.1% by mass, castability such as molten metal flow, cast skin and core cracking deteriorates and extrudability deteriorates. That is, by making Fe 0.1% by mass or less, deterioration of castability and extrudability is prevented, and productivity is improved. Moreover, deterioration of brazeability is also prevented by making Fe 0.1 mass% or less. These functions and effects are similarly achieved in both the inner surface grooved tube in which the groove is formed on the inner surface of the tube and the outer surface fin processed tube in which the fin is formed on the outer surface.

Oxygen (O): 0.005 mass% or less If oxygen is contained in an amount of more than 0.005 mass%, the formed Sn and Cu oxides are wound into the ingot, and the soundness of the ingot is reduced. In addition, hydrogen embrittlement is likely to occur in the annealing process during production, and the wettability of brazing, 0.2% proof stress and fatigue strength are also reduced. Accordingly, the oxygen content is set to 0.005 mass% or less.

Hydrogen (H): 0.0002 mass% or less If hydrogen is contained in an amount of more than 0.0002 mass%, cracking during hot extrusion and blistering during annealing are likely to occur, resulting in a decrease in product yield. Accordingly, the hydrogen content is set to 0.0002 mass% or less.

Zn: 0.01% to 1.0% by 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 tool wear during drawing and rolling, and has the effect of extending the life of the grooved plug. When the Zn content is 0.01% by mass or less, the above-described effects are not sufficient. On the other hand, when Zn is contained more than 1.0 mass%, the stress corrosion cracking sensitivity becomes high, and there is a concern about the possibility of stress corrosion cracking. Therefore, when Zn is added, the Zn content is 0.01 to 1.0 mass%.

  In addition, it is desirable that the total content of Cu, Sn and P or the total content of Cu, Sn, P and Zn is 99.95% by mass or more. In particular, the total of these is more preferably 99.98% by mass or more.

  Further, elements such as Fe, Ni, Co, Mn, Mg, Cr, Ti, Zr and Ag form an intermetallic compound with P contained in the copper alloy tube of the present invention, and precipitate in the matrix phase. If many phosphorus compounds other than Fe are formed, the structure and mechanical properties are likely to vary even when heat treatment is performed under the same conditions. Therefore, the total content of these elements excluding Fe is the total value of these elements. Is preferably 0.03% by mass or less.

  In addition, even if Al, Si, Pb, S, Li, Se, As, Ca, and In are added up to 0.01% by mass or less, the heat resistance, fatigue strength, etc. of the copper alloy tube of the present invention are included. It does not degrade the characteristics.

  Next, the reasons for limiting the average crystal grain size and various characteristics of the copper alloy tube of the present invention will be described.

Average crystal grain size The average crystal grain size is determined by measuring the average crystal grain size in the thickness direction of the cross section parallel to the axial direction of the copper alloy tube by the cutting method specified in JISH0501, and this is arbitrarily determined in the tube axis direction. The average of these was taken as the average crystal grain size.

  When the average crystal grain size exceeds 30 μm, cracks are likely to occur in the bent portion when the copper alloy tube is subjected to hairpin bending in the assembly process of a heat exchanger such as an air conditioner. Therefore, the average crystal grain size needs to be 30 μm or less. The average crystal grain size is more preferably 20 μm or less. Further, it is desirable that the measured crystal grain sizes at 10 locations are within ± 20% of the average value.

0.2% yield strength The copper alloy tube having the above-mentioned composition and average crystal grain size has a 0.2% yield strength of 95 to 200 N / mm ² . Preferably, the 0.2% proof stress is 100 to 150 N / mm ² . In the present invention, by containing Fe, the 0.2% proof stress can be increased as compared with the conventional case. And the variation of 0.2% yield strength can be suppressed by the annealing process mentioned later. When the 0.2% proof stress is less than 95 N / mm ² , the straightness of the tube is impaired during processing, there is a possibility of inconvenience in bendability and the fatigue strength may be reduced. On the other hand, if the 0.2% proof stress exceeds 200 N / mm ² , the tube becomes hard, bending workability and tube expansion workability are reduced, and cracking and buckling occur during processing.

Average crystal grain size after heating to 850 ° C. for 30 seconds The method for measuring the average crystal grain size when heated to 850 ° C. for 30 seconds is as described above. Heating to 850 ° C. for 30 seconds assumes the heating conditions at the time of brazing. If the average crystal grain size exceeds 100 μm due to this heating, the fatigue strength is increased at the brazed portion of the heat exchanger and in the vicinity thereof. If HFC-based chlorofluorocarbon, which requires a high pressure during operation of an air conditioner or the like, is used as a refrigerant, the copper alloy tube is likely to be broken during use. Accordingly, the average crystal grain size after heating at 850 ° C. for 30 seconds is desirably 100 μm or less. The average crystal grain size is more desirably 80 μm or less.

A 0.2% yield strength copper alloy tube after heating to 850 ° C. for 30 seconds is heated to 850 ° C. for 30 seconds, and then a tensile test is performed by a method according to JISZ2241, and a 0.2% yield strength is calculated by an offset method. When the 0.2% proof stress after heating at 850 ° C. for 30 seconds is less than 40 N / mm ² , fatigue failure tends to occur in the copper alloy tube when an HFC-based refrigerant having a high operating pressure is used. Therefore, it is desirable that the 0.2% yield strength after heating at 850 ° C. for 30 seconds is 40 N / mm ² or more.

Fatigue strength after heating to 850 ° C. for 30 seconds After the copper alloy tube is heated to 850 ° C. for 30 seconds, the fatigue strength is measured by the fatigue test method defined in JISZ2273. The copper alloy tube of this test material is heated to 850 ° C. for 30 seconds, and then both ends of the copper alloy tube are fixed and a swing stress of 92 MPa is applied. In this case, when the fracture occurs after the number of repetitions of less than 10 ⁷ times, the reliability of the heat exchanger that uses HFC-based Freon, which requires a high pressure during operation, as the refrigerant is lowered. Accordingly, as the fatigue strength after heating at 850 ° C. for 30 seconds, when the fatigue test is performed with a repeated stress of 92 MPa, the number of repetitions is desirably 10 ⁷ times or more.

  Hereinafter, the manufacturing method of the copper alloy pipe concerning the embodiment of the present invention is explained. In addition, this manufacturing method manufactures copper alloy tubes, such as a smooth tube or an internally grooved tube.

  First, the raw electrolytic copper is dissolved under the charcoal coating. After the copper is dissolved, Sn, Fe and, if necessary, Zn are added in a predetermined amount, and further 15% by mass of P is contained for the purpose of deoxidation. Add copper alloy. In this way, after the component adjustment is completed, a billet having a predetermined size is produced by semi-continuous casting.

Billet heating conditions before hot extrusion: 750 ° C to 1000 ° C
The obtained billet is heated in a heating furnace and subjected to hot extrusion. In this case, the billet is heated to 750 to 1000 ° C. by a billet heater and / or an induction heater before hot extrusion. At this time, when heating at a temperature lower than 750 ° C., the segregation of Sn in the ingot is not sufficiently eliminated, the deformation resistance of the billet during extrusion increases, the capacity of the extruder is insufficient, This leads to an increase in basic unit and cost increase. In addition, when the billet heating temperature before hot extrusion is higher than 1000 ° C., the amount of oxide film on the billet surface increases, which tends to cause entrainment.

  Further, in order to eliminate segregation of the ingot, it is desirable to select a condition in which the heating time is maintained at a temperature of 750 ° C. or higher for 1 minute or longer.

  In addition, when measuring the heated billet temperature before hot extrusion, a radiation thermometer or a contact-type thermometer can be used.

Raw tube cooling conditions after hot extrusion: The extruded raw tube cooled from a temperature of 750 ° C. or higher to 100 ° C. at a cooling rate of 1.5 ° C./second or higher is extruded or extruded from a temperature of 750 ° C. or higher in water. By subsequent water cooling, cooling is performed so that the average cooling rate until the surface temperature reaches 100 ° C. is 1.5 ° C./second or more. When the cooling rate is 1.5 ° C./second or less, the crystal grains of the raw tube become coarse, and the final product tends to be coarse crystal grains or a mixed grain structure. ) Causes rough skin and cracks during bending.

Rolling: processing rate of 92% or less, drawing: processing rate of 40% or less (value in one drawing process)
The raw tube obtained by extrusion is subjected to rolling and drawing to produce a smooth tube. If each processing rate at this time exceeds 92% in the case of rolling, and if the processing rate in one drawing process exceeds 40% in the case of drawing, it may cause rolling breakage and drawing breakage, Product defects such as defects will increase. Note that the outer diameter and thickness of the pipe are reduced and the length is increased by rolling and drawing. The rolling processing rate and the drawing processing rate can be obtained by [(cross-sectional area of the tube before processing−cross-sectional area of the tube after processing) / cross-sectional area of the tube before processing] × 100 (%).

Annealing conditions “heat to 450 to 700 ° C. for 5 to 20 minutes”
In the drawing process, that is, the hard material has high tensile strength and 0.2% proof stress and small elongation, so that workability such as bending is low. Therefore, high workability can be imparted to bending and pipe expansion by softening the copper alloy tube as a uniform recrystallized structure by annealing treatment. For this reason, it is preferable to perform annealing by heating to a temperature of 450 to 700 ° C. for 5 to 20 minutes. By annealing the copper alloy tube of the present invention under these conditions, a copper alloy tube having a 0.2% proof stress of 95 to 200 N / mm ² can be easily obtained. In addition, the annealing treatment can suppress variations in the characteristics of the copper alloy tube due to variations in manufacturing process conditions.

For annealing treatment, continuous annealing by high-frequency heating, annealing in a coil by a roller hearth furnace, etc. may be used, and the operating conditions of the furnace so that the 0.2% proof stress after annealing is 95 to 200 Nmm ² according to the purpose of use. Should be selected.

  The smooth tube manufactured in this way can be used as it is for a heat exchanger, or can be used as a material for an internally grooved tube. When this smooth tube is used as the material for the internally grooved heat transfer tube, the annealing treatment may be performed to form a soft annealing tube, and then the groove may be formed, or the groove may be formed and then annealed.

  Next, the manufacturing method of the internally grooved tube according to the embodiment of the present invention will be described. In the present embodiment, a rolled ball is used. FIG. 1 is a cross-sectional view showing a manufacturing apparatus 41 for an internally grooved tube using this rolled ball. In the inner surface grooved pipe manufacturing apparatus 41, the reduced diameter portion 62, the rolled portion 43, and the shaping portion 64 are provided in a line in this order. Then, by drawing the metal tube 51 along the drawing direction 52, the metal tube 51 passes through the reduced diameter portion 62, the rolling portion 43, and the shaping portion 64 in this order, and is processed into the inner grooved tube 53. It has become.

  In the reduced diameter portion 62, a lubricating oil supply device 65 that supplies the lubricating oil 21 to the outer surface of the metal tube 51 is provided, and the outer surface of the metal tube 51 is located downstream of the lubricating oil supply device 65 in the drawing direction 52. A diameter-reducing die 66 is provided so as to be in contact with. The reduced diameter die 66 is an annular straight die, through which the metal tube 51 passes. Further, the inner diameter of the opening of the reduced diameter die 66 continuously decreases along the drawing direction 52. That is, the inner surface of the reduced diameter die 66 is tapered. Further, a reduced diameter plug 67 is provided at a position corresponding to the reduced diameter die 66 inside the metal tube 51, and is engaged with the reduced diameter die 66 through the metal tube 51. The reduced diameter plug 67 is a straight plug, and its outer surface is smooth. The diameter reducing die 66 and the diameter reducing plug 67 are for reducing the diameter of the metal tube 51.

  Further, the rolling unit 43 is provided with a lubricating oil supply device 68 that supplies the lubricating oil 42 to the outer surface of the metal pipe 51, and the downstream side in the drawing direction 52 as viewed from the lubricating oil supply device 8 is processed. A head 39 is provided. The machining head 39 is connected to a motor (not shown) and rotates around the metal tube 51. A plurality of rolling balls 70 are provided on the processing head 39 so as to be in contact with the outer surface of the metal tube 51, and the rolling balls 70 are in rolling contact with the outer surface of the metal tube 51 as the processing head 39 rotates. It is designed to rotate around the planet. A grooved plug 72 is provided inside the metal tube 51. The grooved plug 72 is rotatably connected to the reduced-diameter plug 67 via a plug shaft 73 and is disposed at a position corresponding to the rolled ball 70. A spiral groove is formed on the outer surface of the grooved plug 72. The rolling ball 70 and the grooved plug 72 form a groove on the inner surface of the metal tube 51.

  Further, the shaping unit 64 is provided with a lubricating oil supply device 74 that supplies the lubricating oil 23 to the outer surface of the metal pipe 51, and a shaping die is disposed downstream of the drawing direction 52 as viewed from the lubricating oil supply device 74. 75 is provided. The shape of the shaping die 75 is an annular shape, and the metal tube 51 passes through the opening. The inner surface of the shaping die 75 is tapered, and the inner diameter of the opening decreases along the drawing direction 52. The shaping die 75 is for shaping the metal tube 51.

  Furthermore, on the upstream side in the drawing direction 52 as seen from the reduced diameter portion 62, there is a delivery portion (not shown) for sequentially feeding the metal tube 51 from a basket in which the annealed metal tube 51 is wound in a coil shape. A drawing device (not shown) for drawing the metal tube 51 in the drawing direction 52 and a manufactured inner grooved tube 53 are wound around the basket on the downstream side of the drawing direction 52 as viewed from the shaping portion 64. A take-up device (not shown) is provided.

  Next, a method for manufacturing an internally grooved tube using the above-described apparatus will be described. First, the metal tube 51 is inserted into the inner surface grooved tube manufacturing apparatus 41, and a tool in which the reduced diameter plug 67, the plug shaft 73 and the grooved plug 72 are connected to each other is placed inside the metal tube 51, Inject lubricating oil for rolling. Thereafter, a drawing device (not shown) pulls the metal tube 51 in the drawing direction 52. As a result, the metal pipe 51 is fed out from a delivery device (not shown) and starts moving along the drawing direction 52. Then, the metal tube 51 is processed into the inner grooved tube 53 by sequentially passing through the reduced diameter portion 62, the rolling portion 63 and the shaping portion 64. Hereinafter, the process which a certain part of the metal pipe 51 performs with a movement is demonstrated in order.

  In the processing of the reduced diameter portion, rolled portion and shaping portion described below, the role of the lubricating oil supplied to the outer surface of the metal tube is to reduce friction and wear, to suppress seizure, to cool, etc. In addition to these functions, the oil is required not to remain when the processed metal tube (inner grooved tube) is annealed and to have a low fuming property. Based on these roles and required characteristics, many types of lubricating oils have been developed, such as oil-based oils based on mineral oil and water-soluble oils whose characteristics such as density and kinematic viscosity are variously changed. An appropriate lubricating oil is selected in accordance with the required processing rate and processing speed.

  First, in the reduced diameter portion 62, the lubricating oil supply device 65 supplies the lubricating oil 21 to the outer surface of the metal pipe 51. At this time, the lubricating oil 21 is generally a lubricating oil (hereinafter referred to as a mineral oil-based lubricating oil) having a synthetic polymer compound, an oiliness improver, etc. added to improve the lubricity and viscosity based on a mineral oil. Next, the diameter reducing die 66 and the diameter reducing plug 67 reduce the diameter of the metal pipe 51 and remove the lubricating oil 21 from the outer surface of the metal pipe 51. The removed lubricating oil 21 is recovered and reused.

  Next, in the rolling unit 43, the lubricating oil supply device 68 supplies the lubricating oil 42 to the outer surface of the metal pipe 51. As the lubricating oil 42, the same type of mineral oil as the lubricating oil 21 is used. Next, when the machining head 39 rotates around the metal tube 51, the rolling ball 70 presses the metal tube 51 toward the grooved plug 72 while rotating around the metal tube 51 as a planet. As a result, the groove on the outer surface of the grooved plug 72 is transferred to the inner surface of the metal tube 51, and a spiral groove is formed on the inner surface of the metal tube 51. At this time, as the metal tube 51 moves, the lubricating oil 42 is taken out to the shaping portion 64 beyond the position where the rolling ball 70 is in contact with the outer surface of the metal tube 51.

  Next, in the shaping unit 64, the lubricating oil supply device 74 supplies the lubricating oil 23 to the outer surface of the metal pipe 51. At this time, the same kind of mineral oil as the lubricating oils 21 and 42 is used for the lubricating oil 23. Then, the lubricating oil 42 and the lubricating oil 23 are mixed on the outer surface of the metal pipe 51. Next, the shaping die 75 shapes the metal tube 51 and removes the mixed oil of the lubricating oils 23 and 42 from the outer surface of the metal tube 51. Thereby, the inner surface grooved tube 53 is manufactured. The removed mixed oil of the lubricating oils 23 and 42 is recovered and reused.

In this way, an annealed soft smooth tube is used as a material, and a floating plug and a grooved plug that is connected to the floating plug via a connecting shaft and is rotatable around the connecting shaft are arranged in the tube. The inner surface grooved tube can be manufactured by pressing the outer side of the tube corresponding to the position of the grooved plug with a rolling ball or a rolling roll rotating in the circumferential direction. In this case, the floating plug is engaged with the reduced diameter die to hold the groove plug in a predetermined position. Further, the raw tube is reduced in diameter when passing through the reduced diameter die, further reduced in diameter by a forming die behind the rolling roll, and shaped so that its cross-sectional shape becomes a circle. When processing an internally grooved tube by such a rolling method, it is desirable that the 0.2% proof stress of the soft smooth tube is 50 to 150 N / mm ² .

Also in the manufacturing method of the above-mentioned inner surface grooved tube, it is preferable to perform an annealing treatment after the groove formation. As described above, the annealing process is performed by heating at a temperature of 450 to 700 ° C. for 5 to 20 minutes as described above. By including Fe and annealing, a 0.2% proof stress is 95 to 200 N / mm ² of copper. An alloy tube can be obtained.

  Hereinafter, the result of having compared the characteristic with the comparative example which remove | deviates from the range of this invention about the smooth tube of the Example of this invention or the inner surface grooved pipe is demonstrated.

  In addition, the average crystal grain size is determined by measuring the average crystal grain size in the thickness direction with respect to a cross section parallel to the axial direction of the copper alloy tube by a cutting method defined in JISH0501, and measuring the average crystal grain size in the tube axis direction. The average was measured as the average crystal grain size. The 0.2% proof stress was determined according to JISZ2241. The fatigue strength was determined using a fatigue test method based on JISZ2273.

First embodiment (smooth tube)
The sample material was manufactured by the following process.
(1) Using copper as a raw material, predetermined Sn and Fe were added to the molten metal, Zn was further added as required, and then a Cu-P master alloy was added to prepare a molten metal having a predetermined composition. .
(2) An ingot having a diameter of 300 × length of 3000 mm was semi-continuously cast at a casting temperature of 1130 ° C.
(3) A billet having a length of 480 mm was cut out from the ingot.
(4) The billet was heated in a billet heater maintained at 900 ° C., and after reaching 900 ° C., the billet was maintained for 1.5 hours and homogenized.
(5) Thereafter, the cooled billet was heated with an induction heater, and after reaching 960 ° C., the billet was held for 3 minutes, and then extruded to produce an extruded element tube having an outer diameter of 94 mm and a wall thickness of 10 mm. After extrusion, the extruded tube was cooled with water, and the average cooling rate was 3.5 ° C./second from a temperature of 750 ° C. to 100 ° C.
(6) The extruded element tube was rolled to produce a rolled element tube having an outer diameter of 43 mm and a wall thickness of 2.2 mm.
(7) The rolled blank was drawn and drawn five times, and was drawn to an outer diameter of 9.52 mm and a wall thickness of 0.80 mm at a processing rate of 28 to 33%.
(8) The drawing element tube was annealed in a roller hearth furnace in an annealing furnace to obtain a test material.
(9) About the said test material, brazing heating was assumed and the test material was hold | maintained for 30 seconds in the salt bath furnace of 850 degreeC.

  Therefore, in this first embodiment, the heating temperature of the billet used for the hot extrusion process is 960 ° C., and the cooling rate from 750 ° C. or higher to 100 ° C. is 3.5 ° C./second. The rolling rate of the extruded blank was 89%, the drawing rate of the rolled blank was 35% or less for each drawing in multiple times, and the total rate of drawing was about 92%.

The test items are as follows.
(1) Component: A predetermined amount of a sample was taken from the test material, and the composition was analyzed.
(2) Average crystal grain size: measured by the method described above.
(3) Bending test: Ten tubes having a length of 1000 mm were sampled from the test material, subjected to hairpin bending at a pitch of 25 mm, and the presence or absence of cracks in the bent portion was confirmed.
(4) 0.2% yield strength: measured by the method described above.
(5) Fatigue test: Tested by the method described above. The bending stress at the limit at which cracks do not occur at the number of repetitions of 10 ⁷ times and the presence or absence of cracks when a stress of 92 MPa was applied were confirmed.
(6) Brazing test: A 300 mm-long test material tube was halved in the axial direction, and a phosphor copper brazing (BCuP-2) having a diameter of 1.6 mm and a length of 10 mm was placed on the inner surface. Holding at 850 ° C. for 10 minutes in an air stream, the spreading length of the wax was measured. In addition, the thickness of the oxide film measured before heating was all 500 nm or less in terms of Cu ₂ O.

  The above test results are shown in Tables 1 and 2 below. Examples 1 to 9 are examples that satisfy Claim 1 of the present invention, and Example 10 is an example that satisfies Claim 2 of the present invention. Comparative Examples 11 to 14 are Comparative Examples of Claim 1 and Comparative Example 15 is Comparative Example of Claim 2. Table 1 shows the characteristics after annealing before heating assuming brazing, and Table 2 shows the characteristics after heating for 30 seconds at 850 ° C. assuming brazing. Items underlined in the table are numerical values outside the scope of the present invention, indicating that they are comparative examples. In the “wax spreading length” column, ○ indicates good and Δ indicates slightly poor.

Examples 1 to 10 all have a 0.2% proof stress of 95 to 200 N / mm ² , satisfying a sufficiently high range that can be practically processed. In addition, Examples 1 to 10 have excellent bending workability and wax spreadability, and excellent fatigue strength. In Examples 1 to 10, even after heating to 850 ° C. for 30 seconds, the coarsening of crystal grains is small and the decrease in yield strength is small.

  On the other hand, Comparative Example 11 is a Sn copper alloy that does not contain Fe, but has a 0.2% lower proof stress than the copper alloy tubes of Examples 1 to 10. In Comparative Example 11, the coarsening of the crystal grains after heating at 850 ° C. for 30 seconds is large, and the 0.2% yield strength is greatly reduced.

  In Comparative Example 12, the contents of both Sn and Fe are larger than the upper limit values of 1.0% and 0.1% of the present invention, respectively. Cracks occurred in the test. Moreover, since the comparative example 12 has much content of Sn and Fe, castability, extrudability, etc. are bad, and it is the cause of productivity fall. Furthermore, Comparative Example 12 has a slightly poor wax spreading property.

  In Comparative Example 13, since the Fe content was less than 0.03%, a sufficient 0.2% proof stress value could not be secured.

  In Comparative Example 14, the Sn content was less than 0.1%, so the desired 0.2% proof stress could not be satisfied.

  In Comparative Example 15, since the Zn content was more than 1.0%, the wax spreading length was slightly reduced.

Second embodiment (inner grooved tube)
Using a rolling blank having the composition shown in Table 3 below, an internally grooved tube was manufactured by the method shown below. The steps (1) to (6) are the same as in the case of the smooth tube. Therefore, the manufacturing conditions up to the smooth tube are the same as in the first embodiment.
(7) The rolled rough tube was drawn to produce a raw tube having a processing rate of 40% or less, an outer diameter of 12.7 mm, and a wall thickness of 0.34 mm.
(8) The grooved rolling element tube was subjected to intermediate annealing with an induction heater.
(9) The annealed grooved rolling element tube was subjected to grooved rolling with a rolling ball to produce an internally grooved tube having an outer diameter of 9.52 mm and a bottom wall thickness of 0.26 mm. This inner surface groove has an internal fin height of 0.2 mm, a lead angle of 30 °, and an internal fin number of 55. The manufactured internally grooved tube was annealed and used as a test material. The test items were the same as in the case of the smooth tube except that the brazing test was not performed.

  The above test results are shown in Tables 3 and 4 below. Examples 16 to 18 are examples that satisfy Claim 1 of the present invention, and Comparative Examples 19 and 20 are comparative examples that deviate from Claim 1. Table 3 shows the characteristics after annealing before heating assuming brazing, and Table 4 shows the characteristics after heating for 30 seconds at 850 ° C. assuming brazing. Items underlined in the table are numerical values outside the scope of the present invention, indicating that they are comparative examples.

Examples 16 to 18 are the copper alloy tubes of the present invention, and all of them have a high 0.2% proof stress of 92 to 200 N / mm ² and satisfy the practically workable range. In addition, Examples 16 to 18 have excellent bending workability and excellent fatigue strength. Further, in Examples 16 to 18, even after heating to 850 ° C. for 30 seconds, there is little coarsening of crystal grains and a decrease in yield strength is small.

  On the other hand, Comparative Example 19 is an Sn copper alloy tube that does not contain Fe, but has a 0.2% yield strength lower than those of Examples 16 to 18. In Comparative Example 19, the coarsening of the crystal grains after heating at 850 ° C. for 30 seconds is large, and the yield strength is greatly reduced.

  Further, in Comparative Example 20, since the Fe content was more than 0.1%, the 0.2% proof stress was too larger than the practical range, and cracking occurred in the bending test. Moreover, since there was much content of Fe, castability and extrudability were bad, and productivity fell.

Third embodiment (manufacturing conditions)
Hereinafter, the result of comparing the manufacturing method of the smooth tube or the inner surface grooved tube of the example satisfying the manufacturing condition of the present invention with the manufacturing method of the comparative example in which the manufacturing condition deviates from the present invention will be described. Sample materials were prepared by the following steps, and the quality and defects in each step shown in Table 5 below were investigated.
(1) Using copper as a raw material, a predetermined amount of Sn and Fe is added to the molten metal, and then a Cu-P master alloy is added to obtain Cu-0.60% Sn-0.06% Fe-0.020. A molten metal having a composition of% P was prepared.
(2) An ingot having a diameter of 300 × length of 3000 mm was semi-continuously cast at a casting temperature of 1130 ° C.
(3) A billet having a length of 480 mm was cut out from the ingot. At this time, when a structure perpendicular to the casting direction of the ingot was observed, the crystal grains were refined and the equiaxed crystals were dominant.
(4) The billet was heated using a billet heater and an induction heater until the heating temperature before extrusion described in Table 5 below was reached. Thereafter, an extruded element tube having an outer diameter of 94 mm and a wall thickness of 10 mm was produced by hot extrusion. After the extrusion process, the extruded element tube was water-cooled and cooled at a cooling rate shown in Table 5 to cool it from 750 ° C. or higher to 100 ° C.
(5) The extruded element tube was rolled at each rolling processing rate shown in Table 5 below to produce a rolled element tube.
(6) This rolled blank was drawn at the drawing rate shown in Table 7 to produce a drawn blank having an outer diameter of 9.52 mm and a wall thickness of 0.3 mm.
(7) The drawn element tube was annealed in an annealing furnace so that the 0.2% proof stress was 150 ± 5 N / mm ² to obtain a test material.
(8) Using this specimen, the same bending test as described above was performed, and the presence or absence of cracks during hot rolling bending was examined.

The test items are as follows.
(1) Presence / absence of entrainment:
The extruded element tube was visually inspected for the presence of entrainment defects. When it occurs, it tends to occur frequently at the rear end portion of the raw tube, and when flowing to the next process, the range that can be visually confirmed is cut and removed.
(2) Crystal grain size of extruded tube:
Measurement was performed by the method described above.
(3) Presence or absence of rolling and drawing fracture:
It was confirmed that rolling and drawing could be performed without breaking in the set process. The breakage of the mouthpiece was also taken as a break.
(4) Bending test:
This was confirmed by the method described above.

  The above test results are also shown in Table 5 below. In Example 21, manufacturing conditions fall within the scope of the present invention, and in Comparative Examples 22 to 27, manufacturing conditions fall outside the scope of the present invention. Items underlined in the table indicate numerical values outside the scope of the present invention.

  Example 21 relates to a copper alloy tube manufactured under conditions that fall within the scope of the method of the present invention. There is no entanglement of oxide or the like, the crystal grain of the extruded element tube is fine, and there is no breakage during rolling and drawing. In the hot rolling bending test, no cracks occurred.

  On the other hand, in Comparative Example 22, the heating temperature before extrusion was as high as 1050 ° C., and it was predicted that the oxide film on the billet surface before extrusion became thick, and oxide entrainment occurred. The entrained part was cut and removed and supplied to the next process. However, due to the effect of entrainment that could not be seen with the naked eye, drawing breakage occurred even during drawing. Many parts were cut and removed, which led to an increase in cost due to a decrease in yield.

  In Comparative Example 23, the extrusion temperature was high, and the cooling rate was as low as 1.0 ° C./second. As a result, oxide was involved, and the crystal grain of the extruded element tube was as coarse as 0.7 mm. As described above, drawing fracture occurred, and the crystal grains of the final product became coarse, and cracking occurred in the hot rolling bending test.

  In Comparative Example 24, the extrusion temperature was low, and when the deformation resistance of the ingot and the press capability of the extruder were calculated, the extrusion became impossible and the test was abandoned because of fear of clogging.

  Since the cooling rate of Comparative Example 25 was as low as 1.0 ° C./second, the crystal grains of the extruded element tube were coarse as described above, and cracks occurred in the hot rolling bending test.

  In Comparative Example 26, the processing rate at the time of rolling was as high as 95%, and it broke at the butt portion during rolling. Therefore, rolling became impossible and the test was completed.

  In Comparative Example 27, the processing rate during drawing was as high as 43%, and fractured several times during drawing.

It is a figure which shows the apparatus which manufactures the inner surface grooved pipe of embodiment of this invention with a rolling ball.

Explanation of symbols

41; Manufacturing apparatus 62; Reduced diameter part 43; Rolled part 64; Shaping part 65, 68, 74; Lubricating oil supply device 66; Reduced diameter die 67; Reduced diameter plug 70; Rolled ball 72; Plug shaft 75; shaping die

Claims (7)

Sn: 0.1 to 1.0 mass%, P: 0.005 to 0.1 mass%, Fe: 0.035 to 0.1 mass%, O: 0.005 mass% or less, and H: 0.0002 It has a composition comprising a mass% or less, the balance being Cu and inevitable impurities, an average crystal grain size of 30 μm or less, and a 0.2% proof stress of 95 to 200 N / mm ^2. Copper alloy tube for heat exchanger. Furthermore , it contains Zn: 0.01 thru | or 1.0 mass%, The copper alloy pipe for heat exchangers of Claim 1 characterized by the above-mentioned. The copper alloy tube for a heat exchanger according to claim 1 or 2, wherein the tube is an internally grooved tube having a plurality of spiral grooves on the inner surface of the tube and a plurality of fins formed between the adjacent spiral grooves. When the average grain size after heating at 850 ° C. for 30 seconds is 100 μm or less, the 0.2% proof stress is 40 N / mm ² or more, and the repetition stress is 92 MPa in the fatigue test, the number of repetitions is n = 10 ⁷ times and no fracture occurs It has fatigue strength, The copper alloy pipe for heat exchangers of any one of Claim 1 thru | or 3 characterized by the above-mentioned. Sn: 0.1 to 1.0 mass%, P: 0.005 to 0.1 mass%, Fe: 0.035 to 0.1 mass%, O: 0.005 mass% or less, and H: 0.0002 A billet containing less than or equal to mass% and having the balance consisting of Cu and inevitable impurities is heated to 750 to 1000 ° C. and hot-extruded, and then water-cooled from a temperature of 750 ° C. or higher to obtain 100 ° C. Until the average cooling rate is 1.5 ° C./second or higher, and then at least one rolling process with a processing rate of 92% or less and a drawing process with a processing rate of 40% or less in one drawing process. row have, then, by annealing treatment by heating 5 to 20 minutes at a temperature of 450 to 700 ° C., the heat exchanger, characterized in that 0.2% proof stress obtained copper alloy tube of 95 to 200 N / mm ² Method for producing copper alloy pipe The said billet contains Zn: 0.01 thru | or 1.0 mass% further, The manufacturing method of the copper alloy tube for heat exchangers of Claim 5 characterized by the above-mentioned. Between the drawing process and the annealing process, comprising the step of obtaining the inner grooved tube by facilities the groove on the inner surface of the copper alloy tube after the drawing process, the groove processing step, the floating plug in the tube And a grooved plug connected to the floating plug via a connecting shaft and rotatable about the connecting shaft, and the floating plug is engaged with a reduced diameter die to connect the grooved plug in the pipe circumferential direction. A step of positioning at least one rolling ball disposed along the groove, and pressing the raw tube against the grooved plug by the rolling ball and reducing the diameter successively by a diameter reducing die and the rolling ball. while processing and transferring the inner surface groove shape of the raw tube, groove on said inner surface by shaping the die is characterized in that chromatic and a step of diameter reduction of the raw pipe has been transferred according to claim 5 or 6 described in Method of manufacturing a copper alloy tube for a heat exchanger.

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