WO2014196183A1 - 熱交換器及び当該熱交換器用フィン材 - Google Patents
熱交換器及び当該熱交換器用フィン材 Download PDFInfo
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- WO2014196183A1 WO2014196183A1 PCT/JP2014/002909 JP2014002909W WO2014196183A1 WO 2014196183 A1 WO2014196183 A1 WO 2014196183A1 JP 2014002909 W JP2014002909 W JP 2014002909W WO 2014196183 A1 WO2014196183 A1 WO 2014196183A1
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- intermetallic compound
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
- F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
- F28F21/081—Heat exchange elements made from metals or metal alloys
- F28F21/084—Heat exchange elements made from metals or metal alloys from aluminium or aluminium alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
- B22D11/003—Aluminium alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
- B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/02—Alloys based on aluminium with silicon as the next major constituent
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
- C22F1/043—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with silicon as the next major constituent
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F1/00—Tubular elements; Assemblies of tubular elements
- F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
- F28F19/02—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings
- F28F19/06—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings of metal
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F1/00—Tubular elements; Assemblies of tubular elements
- F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
- F28F1/12—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element
Definitions
- the present invention relates to a heat exchanger in which a decrease in cooling performance is suppressed even in a highly corrosive environment, and a fin material used therefor, and more specifically, a heat exchanger for a room air conditioner, a heat exchanger for a car air conditioner, and these The present invention relates to a fin material used in a heat exchanger.
- Aluminum alloy heat exchangers made of aluminum alloy with good lightness and thermal conductivity are widely used as, for example, condensers for room air conditioners, evaporators, automobile condensers, evaporators, radiators, heaters, intercoolers, oil coolers, etc. Has been.
- the heat exchanger made of aluminum alloy is usually configured by joining a fin material and a tube material (a constituent member of a working fluid passage).
- Non-Patent Document 1 describes details of these clad brazing sheets and powder brazing materials.
- a structure in which a structure derived from wax is formed on at least one surface of a fin material or a tube material is used.
- a portion where a eutectic structure derived from wax appears on the surface of the tube This portion acts as a cathode site and promotes the progress of corrosion of the tube, leading to early refrigerant leakage.
- Patent Document 4 describes a method of using a single-layer brazing sheet instead of the above-described clad brazing sheet in order to omit the production of a brazing sheet and the process of producing and applying a powder brazing material.
- this method it has been proposed to use a single layer brazing sheet for a heat exchanger for the tube material and the tank material of the heat exchanger.
- Patent Document 5 in a method of manufacturing a joined body using a single-layer aluminum alloy material, by controlling the alloy composition, temperature during joining, pressurization, surface properties, etc., it is possible to obtain a good joint and deform. A joining method in which almost no occurrence occurs is described.
- Patent Document 6 describes that, in a joined body joined without using a joining member, a highly corrosion-resistant joined body can be obtained by controlling the difference in the pitting corrosion potential in the composition of one aluminum alloy material and the structure. ing.
- Such hollow corrosion is caused by the fact that the fins of the heat exchanger have a structure as shown in the schematic diagram of FIG. That is, an Al matrix (region A) in which fine Al—Fe—Mn—Si intermetallic compounds are dispersed in the core part, and there is no fine Al—Fe—Mn—Si intermetallic compound on the surface. It has a matrix (region B) layer. Further, the crystal grain boundary of the core material portion has a higher concentration of Si than the surrounding matrix. In this structure, a crystal grain boundary having a high Si concentration portion that becomes a strong cathode is most easily corroded. Therefore, intergranular corrosion occurs at an early stage (FIG. 8B).
- the area A of the Al matrix in which fine Al—Fe—Mn—Si intermetallic compounds are dispersed is likely to corrode. This is because the fine Al—Fe—Mn—Si intermetallic compound dispersed in the Al matrix acts as a cathode and the surrounding Al matrix dissolves. For this reason, the region A is more easily corroded than the surface layer (region B) having no cathode portion, and the internal corrosion proceeds (FIG. 8C). In such a state, even if the shape of the fin is maintained in appearance, there is a problem that the thermal performance is extremely lowered due to the presence of the hollow portion due to the hollow corrosion.
- the present inventors have controlled the heat exchanger structure to suppress the hollow corrosion of the fins even in a highly corrosive environment and maintain the cooling performance for a long time.
- the present inventors have found an exchanger and a fin material for the heat exchanger and have completed the present invention.
- the present invention is the heat exchanger according to claim 1, wherein the heat exchanger includes an aluminum tube through which a working fluid flows, and an aluminum fin metally joined to the tube.
- the heat exchanger includes an aluminum tube through which a working fluid flows, and an aluminum fin metally joined to the tube.
- region B Al-Fe-Mn-Si-based intermetallic compound having an equivalent circle diameter of 2.5 ⁇ m is present less than 5.0 ⁇ 10 4 cells / mm 2 around the grain boundaries and the area Area where 5.0 ⁇ 10 4 to 1.0 ⁇ 10 7 pieces / mm 2 of Al—Fe—Mn—Si intermetallic compound having an equivalent circle diameter of 0.1 to 2.5 ⁇ m exists around B It was set as the heat exchanger characterized by having A.
- the average area of the region B per grain boundary length is s ⁇ m, and 2 ⁇ s ⁇ 40 is satisfied.
- the area occupation ratio of the region A on the surface of the fin is 60% or more in the first or second aspect.
- the present invention is based on any one of claims 1 to 3, wherein no Al—Si eutectic structure exists on the surface of the tube other than the joint fillet.
- the crystal grain size of the Al matrix in the L-LT section of the fin is L ⁇ m
- the Al matrix in the L-ST section of the fin is The crystal grain size was T ⁇ m, and L ⁇ 100 and L / T ⁇ 2.
- the natural potential of the fin is ⁇ 910 mV or more, and the natural potential of the fin is the natural potential of the fillet at the joint between the fin and the tube. From 0 to 200 mV noble.
- the present invention provides the fin material used in the heat exchanger according to any one of claims 1 to 6, wherein Si: 1.0 to 5.0 mass%, Fe: 0.1 to 2 0.0% by mass, Mn: 0.1 to 2.0% by mass, the balance being made of an aluminum alloy consisting of Al and inevitable impurities, and an Si-based intermetallic compound having an equivalent circle diameter of 0.5 to 5 ⁇ m is 250 to 7 ⁇ 10 4 pieces / mm 2 exist and 10 to 1000 pieces / mm 2 of Al—Fe—Mn—Si intermetallic compounds having an equivalent circle diameter exceeding 5 ⁇ m are present in a single layer and heat-bonded. It was set as the fin material for heat exchangers which has a function.
- the present invention according to claim 8 is the invention according to claim 8, wherein the aluminum alloy is Mg: 2.0 mass% or less, Cu: 1.5 mass% or less, Zn: 6.0 mass% or less, Ti: 0.3 mass% or less, V : 0.3 mass% or less, Zr: 0.3 mass% or less, Cr: 0.3 mass% or less, and Ni: 2.0 mass% or less are further included.
- the present invention provides the fin material used in the heat exchanger according to any one of claims 1 to 6, wherein Si: 1.0 to 5.0 mass%, Fe: 0.01 to 2 250 to 7 ⁇ 10 5 pieces / mm 2 made of an aluminum alloy containing 0.0 mass% and made of inevitable impurities including the balance Al and Mn and having an equivalent circle diameter of 0.5 to 5 ⁇ m Heat bonding function with a single layer characterized in that 100 to 7 ⁇ 10 5 / mm 2 of Al—Fe—Mn—Si intermetallic compound having an equivalent circle diameter of 0.5 to 5 ⁇ m exists. It was set as the fin material for heat exchangers to have.
- the aluminum alloy includes Mn: 2.0 mass% or less, Mg: 2.0 mass% or less, Cu: 1.5 mass% or less, Zn: 6.0 mass% or less, Ti : 0.3 mass% or less, V: 0.3 mass% or less, Zr: 0.3 mass% or less, Cr: 0.3 mass% or less, and Ni: 2.0 mass% or less are further selected. It was supposed to contain.
- the present invention provides the fin material used in the heat exchanger according to any one of claims 1 to 6, wherein Si: 1.0 to 5.0 mass%, Fe: 0.01 to 2 containing .0Mass%, an aluminum alloy consisting of unavoidable impurities, including the remainder Al and Mn, Si-based intermetallic compound having an equivalent circle diameter of 5.0 ⁇ 10 [mu] m is present 200 / mm 2 or less, 0 Heat having a heat bonding function with a single layer characterized by the presence of 10 to 1 ⁇ 10 4 / ⁇ m 3 of Al—Fe—Mn—Si intermetallic compound having an equivalent circle diameter of 0.01 to 0.5 ⁇ m It was set as the fin material for exchangers.
- the aluminum alloy according to the twelfth aspect of the present invention includes: Mn: 0.05 to 2.0 mass%, Mg: 0.05 to 2.0 mass%, Cu: 0.05 to 1.5 mass%, Zn: 6.0 mass% or less, Ti: 0.3 mass% or less, V: 0.3 mass% or less, Zr: 0.3 mass% or less, Cr: 0.3 mass% or less, and Ni: 2.0 mass% or less 1 type or 2 types or more.
- the present invention will be described in detail below. 1. Number density of Al-Fe-Mn-Si intermetallic compounds in regions A and B
- the heat exchanger of the present invention controls the self-corrosion resistance of fins, particularly the hollow corrosion, by controlling the material and the structure of the fins during production. It is to suppress.
- a schematic diagram of the cross-sectional structure of the fin of the heat exchanger according to the present invention is shown in FIG. A matrix (hereinafter referred to as “region A”) in which fine Al—Fe—Mn—Si intermetallic compounds having an equivalent circle diameter of 0.1 to 2.5 ⁇ m serving as a cathode are dispersed exists from the surface to the inside. ing.
- region B a region where the fine Al—Fe—Mn—Si intermetallic compound is hardly dispersed.
- these structures are likely to be corroded in the order of the vicinity of the crystal grain boundary, the region A, and the region B. It is the least prone to corrosion). Therefore, the fin of the heat exchanger according to the present invention corrodes in the very vicinity of the grain boundary in a corrosive environment (FIG. 1 (b)), but there exists a region B where corrosion hardly proceeds outside. Therefore, the progress of corrosion from the vicinity of the crystal grain boundary into the matrix is suppressed.
- Al—Fe—Mn—Si based intermetallic compounds having an equivalent circle diameter of 0.1 to 2.5 ⁇ m are 5.0 ⁇ 10 4 to 1.0 ⁇ 10 7 pieces / mm 2 in number density.
- the Al—Fe—Mn—Si intermetallic compounds are specifically Al—Fe, Al—Mn, Al—Fe—Si, Al—Mn—Si, and Al—Fe—Mn.
- region A fine Al-Fe-Mn-Si intermetallic compounds that serve as cathodes are dispersed in a state of being separated from each other, so that corrosion does not proceed preferentially in one direction, but progresses uniformly throughout. To do. For this reason, although corrosion is more likely to occur than in the region B, the entire corrosion is caused and corrosion that causes a rapid loss of heat dissipation performance does not occur.
- the Al—Fe—Mn—Si intermetallic compound does not stably act as a cathode and corrosion occurs. The overall corrosion does not progress. In this area A, corrosion is more likely to occur than in area B. On the other hand, when it exceeds 1.0 ⁇ 10 7 pieces / mm 2 , the Al—Fe—Mn—Si intermetallic compound serving as the cathode is too much, so that the dissolution reaction proceeds and the overall corrosion progresses remarkably. There is a risk of doing.
- the equivalent circle diameter was limited to 0.1 to 2.5 ⁇ m for the following reason. Those with an equivalent circle diameter of less than 0.1 ⁇ m were excluded from the scope because they were too small to act as effective cathodes. On the other hand, when the equivalent circle diameter exceeds 2.5 ⁇ m, corrosion tends to occur at the matrix portion that acts as a cathode and is in contact with the intermetallic compound, but the corrosion does not proceed uniformly. Therefore, this was also excluded from the subject.
- Al—Fe—Mn—Si intermetallic compounds having an equivalent circle diameter of 0.1 to 2.5 ⁇ m are present in a number density of less than 5.0 ⁇ 10 4 pieces / mm 2 .
- Al—Fe—Mn—Si intermetallic compound serving as a cathode since there is almost no Al—Fe—Mn—Si intermetallic compound serving as a cathode, corrosion hardly occurs compared to the region A. Therefore, when the region A and the region B exist in the vicinity of the same member, the corrosion in the region A proceeds preferentially.
- this number density in the region B is 5.0 ⁇ 10 4 pieces / mm 2 or more, the region A is formed. Therefore, even if such a structure exists around the crystal grain boundary, it cannot exert an action that hinders the progress of corrosion from the crystal grain boundary to the inside of the matrix.
- this number density includes the case of 0 piece / mm ⁇ 2 >.
- the equivalent circle diameter was limited to 0.1 to 2.5 ⁇ m for the following reason. Those with an equivalent circle diameter of less than 0.1 ⁇ m were excluded from the scope because they were too small to work as effective cathodes and did not affect the corrosion inhibition effect in region B. On the other hand, those having an equivalent circle diameter exceeding 2.5 ⁇ m were excluded from the object for the same reason as in the region A.
- the number density of the Al—Fe—Mn—Si intermetallic compound in the above regions A and B is in an arbitrary cross section of the aluminum alloy material.
- the cross section along the thickness direction may be used.
- the cross section may be parallel to From the viewpoint of simplicity of material evaluation, it is preferable to adopt a cross section along the thickness direction.
- s is obtained by measuring the cross-sectional structure of the fin. That is, the total length of the crystal grain boundaries (L1 + L2 +... + Ln) and the total area of the region B in contact with the crystal grain boundaries (s1 + s2 +. (S1 + s2 +... + Sn) / (L1 + L2 +... + Ln) ⁇ ⁇ (1/2).
- the fixed visual field is preferably a visual field of at least 0.1 mm 2 or more.
- the average area s ⁇ m is less than 2 ⁇ m, the progress of the corrosion cannot be sufficiently suppressed, and the corrosion to the dispersed region A in the grains progresses, so that there is a possibility that the hollow corrosion occurs.
- the average area s ⁇ m exceeds 40 ⁇ m, there is no region A in which the fine intermetallic compound serving as the cathode is dispersed in the vicinity, so that pitting corrosion in the thickness direction occurs abruptly and hollow corrosion occurs. May occur.
- the region B existing around the crystal grain boundary occurs when the aluminum phase is kept above the solidus temperature and the liquid phase penetrates into the crystal grain boundary, and the crystal grain boundary moves as it is. To do.
- the Al-Fe-Mn-Si intermetallic compound and liquid phase existing in the forward direction are taken in, and the Al-Fe-Mn-Si intermetallics are taken behind.
- An Al phase in which no compound or liquid phase exists is formed.
- This Al phase is the region B, and the total area becomes (s1 + s2 +.
- the total area increases as the mobility of the grain boundaries increases.
- the total length of the crystal grain boundaries decreases as the mobility of the crystal grain boundaries increases and the crystal grains merge.
- the average area s ⁇ m of the region B existing around the grain boundary is measured as follows. (1) First, the L-ST cross section of the fin of the aluminum material is mirror-polished, and after Keller etching, observed at a plurality of positions with an optical microscope. (2) When the observation image is obtained, the crystal grain boundary in the image is first identified, and the sum of the lengths of all crystal grain boundaries (L1 + L2 +... + Ln) is obtained. In the sample in which the liquid phase penetrates into the crystal grain boundary, the part that is observed black on the line by Keller etching is the crystal grain boundary. Even if the portion observed in black on the line is partially discontinuous, if the straight line matches by drawing a virtual line, the blank portion is also regarded as a grain boundary.
- the crystal grain boundary can be determined by observing with the optical microscope after treating the same field of view with the anodizing method. Can be identified. In addition, the grain boundary can be identified by analysis by EBSP. (3) When the crystal grain boundary is identified, it is examined whether or not the region B exists in the periphery of the Keller etching observation image. In the region B, the Al—Fe—Mn—Si intermetallic compound is less than 5.0 ⁇ 10 4 pieces / mm 2 , so that at least one Al—Fe—Mn—Si in a square of 4.4 ⁇ m is used.
- the region where there is no intermetallic compound is the region B, and by connecting particles within a distance of 4.4 ⁇ m to each other, the boundary line between the region A and the region B can be drawn. did. However, in this method, the region B formed with a width of 4.4 ⁇ m or less along the grain boundary is not detected. As defined in claim 2 as 2 ⁇ s ⁇ 40 ⁇ m, it has been found that the region B formed around the grain boundary is effective when it exceeds 2 ⁇ m.
- the boundary line between the region A and the region B is drawn.
- the distance from the nth particle is 4.4 ⁇ m or less. This is a case where the particle is not found other than the (n ⁇ 1) th particle.
- the nth particle is a particle belonging to the region B, and no line is formed.
- both particle A and particle B are recognized as particles in region B.
- the (n ⁇ 1) th particle is also determined to belong to the region B when there is no particle within a distance of 4.4 ⁇ m other than the nth particle.
- region B which extends far beyond the distance of 40 ⁇ m from the grain boundary on the surface, suppresses the corrosion rate of the surface while preferentially causing internal corrosion and causing hollow-out corrosion. Measurement is performed separately from the region B.
- the region A is distributed from the surface layer to the inside of the fin in the thickness direction.
- the region B may also be mixed in spots from the surface layer to the inside in the thickness direction, for example, around crystallized particles having an equivalent circle diameter exceeding 1 ⁇ m.
- the area occupation ratio of the region A on the surface of the fin is 60% or more, the corrosion occurs from the surface layer as a whole, and no hollow corrosion or rapid corrosion progress in the thickness direction occurs. The overall corrosion proceeds from. Therefore, the area occupancy is preferably 60% or more.
- the area occupation ratio a of the region A on the surface decreases as the crystal grain boundary in a state where the liquid phase penetrates moves on the surface and the surface region B increases. Therefore, the larger the movement of the crystal grain boundary in the state where the liquid phase has permeated, the smaller the area occupation ratio a becomes. Furthermore, since the crystal grain boundary in contact with the surface increases as the crystal grain size becomes smaller, the generation rate of the region B due to the movement of the crystal grain boundary on the surface increases, and the area occupation ratio a becomes smaller. When a brazing filler metal layer is formed on the surface like a clad material, the area occupation ratio a is almost 0%.
- the area occupation ratio a of the region A on the surface can be obtained by drawing the boundary line between the region A and the region B in the same manner as when the average area s ⁇ m is obtained.
- the connection is started from the grain boundary, whereas when the area occupancy a of the region A is measured, it starts from the surface. Similar to the grain boundary, when the surface and the particle are connected, one having a distance of 2.0 ⁇ m or less is connected as shown in FIG. Next, particles within a distance of 4.4 ⁇ m from the particles are connected by a line. At that time, an infinite number of such particles are found on the region A side, so only the particles on the most region B side are connected.
- region A is defined as region A.
- Region B is defined as the distance between particles that are present apart from each other or between the grain boundary and the particle.
- the area occupancy a is calculated by dividing the total length (a1 + a2 +... + An) of the region A on the surface in the observation image by the surface length 2M. In this case, unlike the case where the average area s of the region B in contact with the grain boundary is obtained, it is not necessary to distinguish between the region B in contact with the grain boundary and the region B not in contact with the grain boundary.
- the heat exchanger of the present invention has the main point of the invention in particular to prevent the hollow-out corrosion of the fin, but since it is assumed to be used in a highly corrosive environment, the fin It is preferable that other parts also have high corrosion resistance.
- the tube material is preferably an extruded multi-hole tube or an electric resistance welded tube having a sacrificial anode material disposed on the surface.
- the structure may be a structure in which the amount of the additive element is reduced and the compound serving as the cathode site is small, or the structure is provided with a sacrificial anticorrosive layer (which is regarded as a single layer even if sprayed) on the surface.
- the Al in the L-LT cross section of the fin When the crystal grain size of the matrix is L ⁇ m and the average length in the plate thickness direction of the crystal grains of the Al matrix in the L-ST cross section of the fin is T ⁇ m, it is preferable that L ⁇ 100, and L / T ⁇ 2 Is preferable.
- the longitudinal direction is L
- the width direction is LT
- the plate thickness direction is ST
- the cross section consisting of the L direction and the LT direction is the L-LT cross section
- the cross section consisting of the L direction and the ST direction is L-ST section
- the grain boundaries are particularly susceptible to corrosion in the structure. If L ⁇ 100 ( ⁇ m), the fins may become very brittle at an early stage due to corrosion of crystal grain boundaries. Further, in the L-ST cross section, as the ratio of the length of the crystal grain boundary extending in the thickness direction is larger than the length of the crystal grain boundary extending in the longitudinal direction, the corrosion penetrates earlier in the thickness direction due to corrosion. The working fluid may leak or become brittle. If L / T ⁇ 2, corrosion that penetrates in the thickness direction may occur at an early stage.
- the upper limit values of L and L / T are not particularly specified, and are determined by the alloy composition and manufacturing conditions of the fin material and the joining conditions of the fin material and the tube material. In the present invention, the upper limit values of L are 5000 ⁇ m, L The upper limit of / T is 100.
- the crystal grain size L ( ⁇ m) of the Al matrix in the L-LT cross section can be measured by observing a sample etched by anodization after mirror polishing with an optical microscope and obtaining a crystal grain structure observation image.
- the average crystal grain size was measured based on ASTM E112-96 at the center of the plate thickness.
- the crystal grain size can be similarly obtained by obtaining a crystal grain structure observation image by analysis using EBSP or the like.
- the average length T ( ⁇ m) of crystal grains in the plate thickness direction of the Al matrix in the L-ST cross section is the average number of Al matrices existing in the plate thickness direction as shown in FIG. Calculate by dividing.
- the average number of Al matrices existing in the plate thickness direction is such that at least 10 cutting lines are drawn at equal intervals in the plate thickness direction at least in the observation field of 1 mm or more in the longitudinal direction, and how many crystal grains are in the cutting line shape. It is measured and averaged. It is desirable to perform the above measurements on at least five observation images and use averaged values.
- the natural potential of the fin is preferably ⁇ 910 mV or more. When the natural potential of the fin is less than ⁇ 910 mV, the corrosion of the fin may progress remarkably.
- the upper limit value of the natural potential of the fin is not particularly defined, and is determined by the alloy composition and manufacturing conditions of the fin material and the bonding conditions of the fin material and the tube material, but in the present invention, it is ⁇ 750 mV.
- the natural potential of the fin is preferably 0 to 200 mV nobler than the natural potential of the fillet at the joint between the fin and the tube. If this potential difference is less than 0 mV, the corrosion of the fin is promoted and the fin may be lost. On the other hand, when this potential difference exceeds 200 mV, the fillet disappears, and the fins may be peeled off from the tube, and the heat dissipation performance may not be maintained.
- a preferable range of this potential difference is 50 to 150 mV.
- the left side of the above (1) exceeds 200, the preferential corrosion due to the sacrificial anticorrosive action of the fillet is promoted too much, and the joint may be peeled off at an early stage.
- the left side of (2) is less than ⁇ 950 mV, the corrosion of the fillet is promoted and the joint may be peeled off at an early stage.
- the left side of (3) is less than 100 mV, the sacrificial anticorrosive action on the tube surface does not act, so that the tube can easily penetrate.
- the left side of (4) is less than ⁇ 950 mV, the corrosion rate of the tube surface is too high, and the sacrificial anticorrosive effect is lost at an early stage, so that there is a risk that penetration will be easier.
- Fin material (first form)
- the heat exchanger of the present invention can be obtained by manufacturing a fin material, which is a material before joining, using a single layer material having a joining function.
- the fin material according to the first embodiment includes, as the fin material, Si: 1.0 to 5.0 mass% (hereinafter, simply referred to as “%”), Fe: 0.1 to 2.0. %, Mn: 0.1 to 2.0% as an essential element, and an aluminum alloy composed of the balance Al and inevitable impurities is used.
- % 1.0 to 5.0 mass%
- Fe 0.1 to 2.0. %
- Mn 0.1 to 2.0%
- an aluminum alloy composed of the balance Al and inevitable impurities is used.
- Fe 0.1 to 2.0%
- Fe has an effect of dispersing as a crystallized substance and preventing a decrease in strength particularly at high temperatures.
- the content of Fe is less than 0.1%, not only the effects described above become insufficient, but also high-purity ingots need to be used, which increases costs.
- it exceeds 2.0% a coarse intermetallic compound is produced at the time of casting, causing a problem in manufacturability.
- the heat exchanger is exposed to a corrosive environment (particularly a corrosive environment in which a liquid flows), the corrosion resistance decreases.
- the addition amount of Fe is 0.1% to 2.0%.
- a preferable Fe content is 0.2% to 1.0%.
- Mn 0.1 to 2.0%
- Mn is an important additive element that forms an Al—Mn—Si-based intermetallic compound with Si and acts as dispersion strengthening, or is a solid additive that improves the strength by solid solution strengthening by solid solution in the aluminum matrix.
- Mn content is less than 0.1%, the above effects are insufficient, and when it exceeds 2.0%, a coarse intermetallic compound is easily formed and the corrosion resistance is lowered. Therefore, the Mn content is 0.1% to 2.0%.
- a preferable Mn content is 0.3% to 1.5%.
- the aluminum alloy used for this fin material is characterized in that there are 250 to 7 ⁇ 10 4 pieces / mm 2 of Si-based intermetallic compounds having a circle-equivalent diameter of 0.5 to 5 ⁇ m.
- the Si-based intermetallic compound includes (1) simple substance Si, and (2) a part of the simple substance Si containing other elements. Examples of other elements include Ca and P.
- Such Si-based intermetallic compounds contribute to liquid phase generation in the liquid phase generation process as described later.
- the number density is in an arbitrary cross section of the aluminum alloy material, and may be, for example, a cross section along the thickness direction or a cross section parallel to the plate material surface. From the viewpoint of simplicity of material evaluation, it is preferable to adopt a cross section along the thickness direction.
- dispersed particles of an intermetallic compound such as Si particles dispersed in an aluminum alloy material react with the surrounding matrix at the time of bonding to generate a liquid phase. Therefore, the finer the dispersed particles of the intermetallic compound, the larger the area where the particles and the matrix are in contact. Therefore, the finer the dispersed particles of the intermetallic compound, the more easily the liquid phase is generated at the time of bonding heating, and good bonding properties are obtained. Further, the finer the Si-based intermetallic compound, the more the shape of the aluminum alloy material can be maintained. This effect is more remarkable when the bonding temperature is close to the solidus or when the heating rate is high.
- the equivalent circle diameter is specified to be 0.5 to 5 ⁇ m, and the number density thereof is 250 to 7 ⁇ 10 4 pieces / mm 2. Need to be. If it is less than 250 pieces / mm 2 , the generated liquid phase is biased and good bonding cannot be obtained. If it exceeds 7 ⁇ 10 4 particles / mm 2 , the reaction area between the particles and the matrix is too large, so that the amount of liquid phase increases rapidly and deformation tends to occur.
- the number density of the Si-based intermetallic compound is 250 to 7 ⁇ 10 4 pieces / mm 2 .
- the number density is preferably 500 pieces / mm 2 or more and 5 ⁇ 10 4 pieces / mm 2 or less, and more preferably 1000 pieces / mm 2 or more and 2 ⁇ 10 4 pieces / mm 2 or less.
- the reason why the equivalent circle diameter is limited to 0.5 to 5 ⁇ m is as follows. There are Si-based intermetallic compounds that are smaller than 0.5 ⁇ m, but at the time of bonding heating, the bonding temperature forms a solid solution in the matrix before reaching the solidus and hardly exists at the time of liquid phase generation. It was excluded because it was not possible. Since there is almost no coarse Si-based intermetallic compound exceeding 5 ⁇ m, it is not considered.
- the aluminum alloy used for the fin material according to the present invention includes an Al—Fe—Mn—Si based intermetallic compound as dispersed particles in addition to the Si based intermetallic compound generated by the basic composition (Al—Si based alloy).
- Al—Fe—Mn—Si intermetallic compound includes Al—Fe, Al—Fe—Si, Al—Mn—Si, Al—Fe—Mn, Al—Fe—Mn—Si compounds, etc. , An intermetallic compound produced by Al and additive elements.
- these Al—Fe—Mn—Si-based intermetallic compounds do not contribute significantly to the formation of a liquid phase, but are dispersed particles that bear material strength together with the matrix.
- the Al-based intermetallic compound 10 to 1000 / mm 2 having an equivalent circle diameter exceeding 5 ⁇ m needs to be present. In the case of less than 10 pieces / mm 2 , deformation due to strength reduction occurs.
- the frequency of nucleation of recrystallized grains during bonding heating increases, and the crystal grain size decreases. When the crystal grains become small, the crystal grains slide at the grain boundary and are easily deformed, so that fin buckling occurs.
- the number density of the Al-based intermetallic compound is 10 to 1000 pieces / mm 2 .
- Al—Fe—Mn—Si intermetallic compound having an equivalent circle diameter of 5 ⁇ m or less. It contributes to the strength after bonding heating. However, those with an equivalent circle diameter of 5 ⁇ m or less are not eligible because they are easily dissolved in the matrix due to grain boundary movement during bonding heating and have little effect on the ease of deformation caused by the crystal grain size after heating. And In addition, Al—Fe—Mn—Si intermetallic compounds having an equivalent circle diameter of 10 ⁇ m or more are substantially excluded from the scope because they hardly exist.
- the number density is in an arbitrary cross section of the aluminum alloy material, similar to the Si-based intermetallic compound, and may be, for example, a cross section along the thickness direction or a cross section parallel to the plate material surface. From the viewpoint of simplicity of material evaluation, it is preferable to adopt a cross section along the thickness direction.
- the equivalent circle diameter of the dispersed particles can be determined by performing SEM observation (reflection electron image observation) of the cross section.
- the equivalent circle diameter means the equivalent circle diameter. It is preferable to obtain the equivalent circle diameter of the dispersed particles before joining by image analysis of the SEM photograph.
- the Si-based intermetallic compound and the Al-based intermetallic compound can also be distinguished by contrast contrast by SEM-reflection electron image observation.
- the metal species of the dispersed particles can be more accurately specified by EPMA (X-ray microanalyzer) or the like.
- the aluminum alloy used in the fin material according to the present invention which has the above-described characteristics in the alloy composition and metal structure, can be joined by its own joining property and can be used as a constituent member of various aluminum alloy structures.
- the heat exchanger according to the present invention can be obtained by applying this alloy material as a fin material.
- Alloy composition (selective additive element) In the aluminum alloy, Mg: 2.0% or less, Cu: 1.5% or less, Zn: 6.0% or less, Ti: 0.3% or less, V: 0.3% as selective additive elements
- Zr 0.3% or less
- Cr 0.3% or less
- Ni 2.0% or less
- Mg 2.0% or less Mg is age-hardened by Mg 2 Si after bonding heating, and the strength is improved by age-hardening.
- Mg is an additive element that exhibits the effect of improving the strength.
- the amount of Mg exceeds 2.0%, it reacts with the flux to form a high melting point compound. As a result, the flux cannot act on the oxide film, so that joining becomes extremely difficult. Therefore, the amount of Mg added is set to 2.0% or less.
- a preferable amount of Mg is 0.05% to 2.0%. More preferably, it is 0.1% to 1.5%.
- Cu 1.5% or less
- Cu is an additive element that improves the strength by solid solution in the matrix.
- the amount of Cu added is preferably 1.5% or less.
- a more preferable amount of Cu is 0.05% to 1.5%.
- Zn 6.0% or less
- Addition of Zn is effective in improving corrosion resistance due to sacrificial anticorrosive action.
- Zn is dissolved almost uniformly in the matrix, but when a liquid phase is generated, it dissolves into the liquid phase and the Zn in the liquid phase is concentrated. When the liquid phase oozes out to the surface, the Zn concentration in the portion increases, so that the corrosion resistance is improved by the sacrificial anodic action.
- the sacrificial anticorrosive action for preventing corrosion of tubes and the like can be exerted by using the aluminum alloy material of the present invention for fins. If the added amount exceeds 6.0%, the corrosion rate increases and the self-corrosion resistance decreases. Therefore, Zn is preferably 6.0% or less. A more preferable Zn addition amount is 0.05% to 6.0%.
- Ti and V have the effect of preventing the progress of corrosion in the plate thickness direction in addition to solid solution in the matrix and improving the strength. . In both cases, if it exceeds 0.3%, coarse crystals are generated, which impairs moldability and corrosion resistance. Accordingly, the Ti and V contents are each preferably 0.3% or less, and more preferably 0.05% to 0.3%.
- Zr 0.3% or less Zr precipitates as an Al—Zr-based intermetallic compound and exhibits the effect of improving the strength after bonding by dispersion strengthening.
- the Al—Zr-based intermetallic compound acts on the coarsening of crystal grains during heating. If it exceeds 0.3%, it becomes easy to form a coarse intermetallic compound, and the plastic workability is lowered. Therefore, the amount of Zr added is preferably 0.3% or less, and more preferably 0.05% to 0.3%.
- the amount of Cr added is preferably 0.3% or less, and more preferably 0.05% to 0.3%.
- Ni 2.0% or less Ni is crystallized or precipitated as an intermetallic compound, and exhibits the effect of improving the strength after bonding by dispersion strengthening.
- the Ni content is preferably in the range of 2.0% or less, and more preferably in the range of 0.05% to 2.0%. When the Ni content exceeds 2.0%, it becomes easy to form a coarse intermetallic compound, and the workability is lowered and the self-corrosion resistance is also lowered.
- a selective element for improving the corrosion resistance of the heat exchanger may be further added.
- Such elements are preferably Sn: 0.3% or less and In: 0.3% or less, and one or two of these are added as necessary.
- Sn and In have an effect of exerting a sacrificial anodic action.
- the added amount exceeds 0.3%, the corrosion rate is increased and the self-corrosion resistance is lowered. Therefore, the amount of each of these elements added is preferably 0.3% or less. A more preferable addition amount is 0.05% to 0.3%.
- a selective element for further improving the bondability may be further added by improving the liquid phase characteristics.
- these 1 type (s) or 2 or more types are added as needed. More preferable ranges of these elements are Be: 0.0001% to 0.1%, Sr: 0.0001% to 0.1%, Bi: 0.0001% to 0.1%, Na: 0 0.0001% to 0.1%, Ca: 0.0001% to 0.05%.
- These trace elements can improve the bondability by fine dispersion of Si particles, improvement in fluidity of the liquid phase, and the like.
- the heat exchanger fin material according to the present invention has a relationship of T / To ⁇ 1.40, where T is the tensile strength of the base plate and To is the tensile strength after heating at 450 ° C. for 2 hours. Shall be satisfied.
- T is the tensile strength of the base plate
- To is the tensile strength after heating at 450 ° C. for 2 hours. Shall be satisfied.
- T / To represents the strength increase rate from the O material.
- this alloy material it is effective to reduce the final amount of cold rolling after annealing in the manufacturing process in order to increase the crystal grain size after bonding heating.
- T / To becomes a large value. In order to prevent the deformation by increasing the crystal grain size after the bonding heating, it is effective to set T / To as an index representing the final processing amount to 1.40 or less.
- the heat exchanger fin material according to the present invention preferably has a tensile strength of 80 to 250 MPa before joining and heating. If the tensile strength before heating is less than 80 MPa, the strength required to form the fin shape is insufficient, and the molding cannot be performed. If it exceeds 250 MPa, the shape retention after being formed into fins is poor, and when assembled into a heat exchanger, a gap is formed with other components, resulting in poor bondability.
- the heat exchanger fin material according to the present invention preferably has a tensile strength of 80 to 250 MPa after joining and heating. If the tensile strength after bonding heating is less than 80 MPa, the strength as a fin is insufficient, and deformation occurs when stress is applied to the heat exchanger itself. If it exceeds 250 MPa, the strength is higher than other constituent members in the heat exchanger, and there is a concern that the joint portion with other constituent members may break during use.
- the aluminum material when it exceeds 100 mm / min, the aluminum material is not sufficiently solidified during casting, and a normal ingot cannot be obtained.
- it is 30 to 80 mm / min.
- a casting speed can be adjusted according to the composition of the alloy material to manufacture.
- the cooling rate depends on the cross-sectional shape of the slab such as thickness and width, the cooling rate of 0.1 to 2 ° C./second can be achieved at the center of the ingot by setting the casting rate to 20 to 100 mm / min.
- the ingot (slab) thickness during DC continuous casting is preferably 600 mm or less. When the slab thickness exceeds 600 mm, a sufficient cooling rate cannot be obtained and the intermetallic compound becomes coarse. A more preferable slab thickness is 500 mm or less.
- the slab manufactured by the DC casting method is subjected to a heating process before hot rolling, a hot rolling process, a cold rolling process, and an annealing process.
- a homogenization treatment may be performed after casting and before hot rolling.
- the slab manufactured by the DC casting method is subjected to a heating process before hot rolling after homogenization or without being homogenized.
- the heating holding temperature is 400 to 570 ° C. and the holding time is about 0 to 15 hours.
- holding temperature is less than 400 degreeC, the deformation resistance of the slab in hot rolling is large, and there exists a possibility that a crack may generate
- holding temperature exceeds 570 degreeC, there exists a possibility that melting may arise locally.
- the holding time of 0 hour means that the heating is terminated immediately after reaching the heating holding temperature.
- Hot rolling process Following the heating process, the slab is subjected to a hot rolling process.
- the hot rolling process includes a hot sparse rolling stage and a hot finish rolling stage.
- the total rolling reduction in the hot rough rolling stage is 92 to 97%, and each pass of the hot rough rolling includes three or more passes where the rolling reduction is 15% or more.
- a coarse crystallized product is generated in the final solidified part.
- the crystallization product is subjected to shearing by rolling and is divided into small pieces, so that the crystallization product is observed in the form of particles after rolling.
- the hot rolling process includes a hot rough rolling stage for obtaining a plate having a certain thickness from the slab and a hot finish rolling stage for obtaining a thickness of about several mm. For fractionation of the crystallized product, it is important to control the rolling reduction in the hot rough rolling stage rolled from the slab.
- the slab thickness is rolled from 300 to 700 mm to about 15 to 40 mm, but the total rolling reduction in the hot rough rolling stage is 92 to 97%, and the hot rough rolling stage By including a pass having a rolling reduction of 15% or more three times or more, a coarse crystallized product can be finely divided.
- the Si-based intermetallic compound and the Al—Fe—Mn—Si-based intermetallic compound that are crystallized products can be refined, and the proper distribution state defined in the present invention can be obtained.
- the total rolling reduction in the hot rough rolling stage is less than 92%, the effect of refining the crystallized product cannot be obtained sufficiently.
- the thickness of the slab is substantially increased, and the cooling rate during casting is slowed down, so that the crystallized material is coarsened, and the crystallized material is sufficiently refined even when hot rough rolling is performed.
- the reduction rate in each pass in the hot rough rolling stage also affects the distribution of intermetallic compounds, and the crystallized product is divided by increasing the reduction rate in each pass. If the number of passes with a rolling reduction of 15% or more in each pass in the hot rough rolling stage is less than 3 times, the effect of refining the crystallized product is not sufficient.
- the reduction ratio is less than 15%, the reduction ratio is not sufficient and the crystallized material is not refined, so that it is not a target.
- the upper limit of the number of passes at which the rolling reduction is 15% or more is not particularly specified, but it is realistic that the upper limit is about 10 times.
- the hot rolled material is subjected to a cold rolling process.
- the conditions for the cold rolling process are not particularly limited.
- an annealing process is provided in which the cold rolled material is sufficiently annealed to have a recrystallized structure.
- the rolled material is subjected to final cold rolling to obtain a final thickness. If the processing rate ⁇ (plate thickness before processing ⁇ plate thickness after processing) / plate thickness before processing ⁇ ⁇ 100 (%) in the final cold rolling stage is too large, the driving force for recrystallization during joining heating is too high. By increasing the size and reducing the crystal grains, the deformation during the bonding heating increases. Therefore, as described above, the processing amount in the final cold rolling stage is set so that T / To is 1.40 or less.
- the processing rate in the final cold rolling stage is preferably about 10 to 30%.
- Fin material (second form) The heat exchanger of the present invention is obtained by manufacturing a fin material that is a material before joining using a material having a joining function with a single layer, but instead of the fin material according to the first embodiment, It can also be obtained by using a material having a bonding function in the single layer shown.
- the fin material is an aluminum alloy material containing Si: 1.0 to 5.0%, Fe: 0.01 to 2.0%, and inevitable impurities including the balance Al and Mn.
- Si-based intermetallic compounds having an equivalent circle diameter of 0.5 to 5 ⁇ m are present at 250 to 7 ⁇ 10 5 pieces / mm 2 in the cross section of the aluminum alloy material, and have an equivalent circle diameter of 0.5 to 5 ⁇ m.
- the aluminum alloy material is characterized in that Al—Fe—Mn—Si based dispersed particles are present at 100 to 7 ⁇ 10 5 particles / mm 2 in the cross section of the aluminum alloy material.
- Al—Fe—Mn—Si based dispersed particles are present at 100 to 7 ⁇ 10 5 particles / mm 2 in the cross section of the aluminum alloy material.
- Si is an element that generates an Al—Si based liquid phase and contributes to bonding.
- the Si concentration is defined as 1.0% to 5.0%.
- the Si concentration is preferably 1.5% to 3.5%, more preferably 2.0% to 3.0%.
- the amount of the liquid phase that oozes out increases as the plate thickness increases and the heating temperature increases, so the amount of liquid phase required during heating depends on the amount of Si and bonding required depending on the structure of the structure to be manufactured. It is desirable to adjust the heating temperature.
- Fe in addition to the effect of improving the strength by slightly dissolving in the matrix, Fe has the effect of dispersing as a crystallized substance and preventing a decrease in strength particularly at high temperatures.
- the addition amount of Fe is less than 0.01%, not only the above effect is small, but also high purity metal must be used and the cost increases.
- it exceeds 2.0% a coarse intermetallic compound is produced at the time of casting, causing a problem in manufacturability.
- the corrosion resistance decreases.
- the addition amount of Fe is set to 0.01% to 2.0%.
- a preferable addition amount of Fe is 0.2% to 1.0%.
- the aluminum alloy material according to the present invention is characterized in that 250 to 7 ⁇ 10 5 pieces / mm 2 of Si-based intermetallic compounds having a circle-equivalent diameter of 0.5 to 5 ⁇ m are present in the cross section.
- the Si-based intermetallic compound includes (1) simple substance Si and (2) a part of the simple substance Si containing elements such as Ca and P, and the liquid described in the liquid phase generation process described above. It is an intermetallic compound that contributes to phase formation.
- the cross section is an arbitrary cross section of the aluminum alloy material, for example, a cross section along the thickness direction or a cross section parallel to the plate material surface. From the viewpoint of simplicity of material evaluation, it is preferable to adopt a cross section along the thickness direction.
- dispersed particles of an intermetallic compound such as Si particles dispersed in an aluminum alloy material react with the surrounding matrix at the time of bonding to generate a liquid phase. Therefore, the finer the dispersed particles of the intermetallic compound, the larger the area where the particles and the matrix are in contact. Therefore, the finer the dispersed particles of the intermetallic compound, the more easily the liquid phase is generated at the time of bonding heating, and good bonding properties are obtained. This effect is more remarkable when the bonding temperature is close to the solidus or when the heating rate is high.
- the equivalent circle diameter is defined as 0.5 to 5 ⁇ m
- the existence ratio is 250 to 7 ⁇ 10 5 pieces / mm 2 in cross section. I need. If it is less than 250 pieces / mm 2 , the generated liquid phase is biased and good bonding cannot be obtained. If it exceeds 7 ⁇ 10 5 particles / mm 2 , the reaction area between the particles and the matrix is too large, so that the amount of liquid phase increases rapidly and deformation tends to occur.
- the existence ratio of the Si-based intermetallic compound is 250 to 7 ⁇ 10 5 pieces / mm 2 .
- the existence ratio is preferably 1 ⁇ 10 3 pieces / mm 2 or more and 1 ⁇ 10 5 pieces / mm 2 or less.
- an Al-based intermetallic compound exists as dispersed particles.
- This Al-based intermetallic compound is composed of Al-Fe-based, Al-Fe-Si-based, Al-Mn-Si-based, Al-Fe-Mn-based, Al-Fe-Mn-Si-based compounds, etc. It is an intermetallic compound to be formed.
- These Al-based intermetallic compounds unlike Si-based intermetallic compounds, do not contribute significantly to the liquid phase generation, but are dispersed particles that bear the material strength together with the matrix.
- the Al-based intermetallic compound having a circle equivalent diameter of 0.5 to 5 ⁇ m needs to be present at 100 to 7 ⁇ 10 5 pieces / mm 2 in the material cross section. In the case of less than 100 pieces / mm 2 , deformation due to strength reduction occurs. On the other hand, when it exceeds 7 ⁇ 10 5 pieces / mm 2 , the recrystallization nuclei increase, the crystal grains become fine, and deformation occurs. As described above, the Al-based intermetallic compound is present in an amount of 100 to 7 ⁇ 10 5 pieces / mm 2 .
- the existence ratio is preferably 1 ⁇ 10 3 pieces / mm 2 or more and 1 ⁇ 10 5 pieces / mm 2 or less.
- the equivalent circle diameter of the dispersed particles can be determined by performing SEM observation (reflection electron image observation) of the cross section.
- the equivalent circle diameter means the equivalent circle diameter. It is preferable to obtain the equivalent circle diameter of the dispersed particles before joining by image analysis of the SEM photograph.
- the Si-based intermetallic compound and the Al-based intermetallic compound can also be distinguished by contrast contrast by SEM-reflection electron image observation.
- the metal species of the dispersed particles can be more accurately specified by EPMA (X-ray microanalyzer) or the like.
- the aluminum alloy material characterized by the Si and Fe concentration ranges and the metal structure can be joined by its own joining property, and can be used as the fin material for the heat exchanger of the present invention.
- the aluminum alloy material has an additive amount defined by using Si, Fe, and Mn as essential elements in order to fulfill the basic function of bondability.
- the aluminum alloy material has a predetermined amount of Mn, Mg and Cu as additive elements in addition to Si and Fe which are essential elements. Further added.
- the surface density in the cross section of the Si-based intermetallic compound and the Al-based intermetallic compound is defined in the same manner as in the first aspect.
- Selective element Mn is an important additive element that forms an Al-Mn-Si intermetallic compound with Si and acts as dispersion strengthening, or is solid-solved in an aluminum matrix and improves strength by solid solution strengthening It is. If the amount of Mn added exceeds 2.0%, a coarse intermetallic compound is easily formed and the corrosion resistance is lowered. Therefore, the amount of Mn added is 2.0% or less. A preferable Mn addition amount is 0.05% to 2.0%. In the present invention, not only Mn but also other alloy components include 0% when the amount is less than a predetermined amount.
- Mg undergoes age hardening by Mg 2 Si after bonding heating, and the strength is improved by this age hardening.
- Mg is an additive element that exhibits the effect of improving the strength. If the amount of Mg added exceeds 2.0%, it reacts with the flux to form a high melting point compound, so that the bondability is significantly lowered. Therefore, the amount of Mg added is set to 2.0% or less. A preferable amount of Mg is 0.05% to 2.0%.
- Cu is an additive element that improves the strength by solid solution in the matrix.
- the amount of Cu added exceeds 1.5%, the corrosion resistance decreases. Therefore, the amount of Cu added is 1.5% or less.
- a preferable addition amount of Cu is 0.05% to 1.5%.
- Ti, V, Cr, Ni and Zr can be selectively added alone or in combination as additive elements other than the above-described additive elements.
- Each selective additive element is described below.
- Ti and V have the effect of preventing the progress of corrosion in the plate thickness direction by being dissolved in a layer, in addition to improving the strength by solid solution in the matrix. If it exceeds 0.3%, giant crystallized matter is generated, which impairs moldability and corrosion resistance. Therefore, the addition amount of Ti and V is preferably 0.3% or less, and more preferably 0.05% to 0.3%.
- the amount of Cr added is preferably 0.3% or less, and more preferably 0.05% to 0.3%.
- the amount of Ni added is preferably in the range of 2.0% or less, and more preferably in the range of 0.05% to 2.0%. When the Ni content exceeds 2.0%, it becomes easy to form a coarse intermetallic compound, and the workability is lowered and the self-corrosion resistance is also lowered.
- the amount of Zr added is preferably 0.3% or less, and more preferably 0.05% to 0.3%.
- selective additive elements for improving corrosion resistance may be added.
- selective additive elements for improving corrosion resistance include Zn, In, and Sn.
- Addition of Zn is effective in improving corrosion resistance due to sacrificial anticorrosive action.
- Zn is dissolved almost uniformly in the matrix, but when a liquid phase is generated, it dissolves into the liquid phase and concentrates in the liquid phase. When the liquid phase oozes out to the surface, the Zn concentration in the oozed portion increases, so that the corrosion resistance is improved by the sacrificial anodic action.
- the sacrificial anticorrosion action for preventing corrosion of tubes and the like can be exerted by using the aluminum alloy material of the present invention for fins. If the amount of Zn added exceeds 6.0%, the corrosion rate increases and the self-corrosion resistance decreases. Therefore, the amount of Zn added is preferably 6.0% or less, more preferably 0.05% to 6.0%.
- the addition amount of Sn and In is preferably 0.3% or less, and more preferably 0.05% to 0.3%.
- a selective element for further improving the bondability by improving the liquid phase characteristics may be further added.
- these 1 type (s) or 2 or more types are added as needed. More preferable ranges of these elements are Be: 0.0001% to 0.1%, Sr: 0.0001% to 0.1%, Bi: 0.0001% to 0.1%, Na: 0 0.0001% to 0.1%, Ca: 0.0001% to 0.05%.
- These trace elements can improve the bondability by fine dispersion of Si particles, improvement in fluidity of the liquid phase, and the like.
- both Fe and Mn together with Si form an Al—Fe—Mn—Si based intermetallic compound. Since Si that forms an Al—Fe—Mn—Si-based intermetallic compound has a small contribution to the formation of the liquid phase, the bondability is lowered. Therefore, when adding Fe and Mn in the aluminum alloy material according to the present invention, it is preferable to pay attention to the amount of Si, Fe, and Mn added. Specifically, when the contents (mass%) of Si, Fe, and Mn are S, F, and M, respectively, the relational expression of 1.2 ⁇ S ⁇ 0.3 (F + M) ⁇ 3.5 is satisfied. Is preferred. When S-0.3 (F + M) is less than 1.2, bonding is insufficient. On the other hand, when S-0.3 (F + M) is larger than 3.5, the shape is likely to change before and after joining.
- the manufacturing method of the aluminum alloy material used for fin material of the said 2nd form is demonstrated.
- This aluminum alloy material can be manufactured using a continuous casting method, a DC (Direct Chill) casting method, or an extrusion method.
- the continuous casting method is not particularly limited as long as it is a continuous casting method such as a twin roll type continuous casting and rolling method or a twin belt type continuous casting method.
- the twin-roll type continuous casting and rolling method is a method in which molten aluminum is supplied between a pair of water-cooled rolls from a refractory hot-water supply nozzle, and a thin plate is continuously cast and rolled.
- the Hunter method, the 3C method, and the like are known. ing.
- twin belt type continuous casting method is a method in which molten metal is poured between rotating belts facing each other up and down and solidified by cooling from the belt surface to form a slab.
- This is a continuous casting method in which a slab is continuously drawn out and wound into a coil.
- the cooling rate during casting is several to several hundred times faster than the DC casting method.
- the cooling rate in the DC casting method is 0.5 to 20 ° C./sec
- the cooling rate in the twin-roll continuous casting and rolling method is 100 to 1000 ° C./sec.
- the dispersed particles generated during casting have a feature of being finely and densely distributed as compared with the DC casting method.
- the dispersed particles distributed at a high density react with a matrix around the dispersed particles at the time of bonding, and can easily generate a large amount of liquid phase, thereby obtaining good bonding properties.
- the speed of the rolled plate at the time of casting by the twin roll type continuous casting and rolling method is preferably 0.5 m / min or more and 3 m / min or less.
- the casting speed affects the cooling rate. When the casting speed is less than 0.5 m / min, a sufficient cooling rate cannot be obtained and the compound becomes coarse. On the other hand, when it exceeds 3 m / min, the aluminum material is not sufficiently solidified between rolls during casting, and a normal plate-shaped ingot cannot be obtained.
- the molten metal temperature when casting by the twin roll type continuous casting and rolling method is preferably in the range of 650 to 800 ° C.
- the molten metal temperature is the temperature of the head box immediately before the hot water supply nozzle.
- 650 ° C. huge intermetallic compound dispersed particles are generated in the hot water supply nozzle, and these are mixed into the ingot to cause a sheet break during cold rolling.
- the molten metal temperature exceeds 800 ° C., the aluminum material is not sufficiently solidified between the rolls during casting, and a normal plate-shaped ingot cannot be obtained.
- a more preferable molten metal temperature is 680 to 750 ° C.
- the thickness of the cast plate is preferably 2 mm to 10 mm. In this thickness range, the solidification rate at the central portion of the plate thickness is fast, and a uniform structure can be easily obtained.
- the cast plate thickness is less than 2 mm, the amount of aluminum passing through the casting machine per unit time is small, and it becomes difficult to stably supply the molten metal in the plate width direction.
- the cast plate thickness exceeds 10 mm, winding with a roll becomes difficult.
- a more preferable cast plate thickness is 4 mm to 8 mm.
- annealing may be performed once or more.
- Appropriate tempering is selected according to the application. Usually, it is H1n or H2n tempered to prevent erosion, but an annealed material may be used depending on the shape and usage.
- the casting speed of the slab or billet during casting it is preferable to control the casting speed of the slab or billet during casting. Since the casting speed affects the cooling rate, it is preferably 20 mm / min or more and 100 m / min or less. When the casting speed is less than 20 mm / min, a sufficient cooling rate cannot be obtained and the compound becomes coarse. On the other hand, when it exceeds 100 m / min, the aluminum material is not sufficiently solidified during casting, and a normal ingot cannot be obtained. A more preferable casting speed is 30 mm / min or more and 80 mm / min or less.
- the slab thickness during DC continuous casting is preferably 600 mm or less. When the slab thickness exceeds 600 mm, a sufficient cooling rate cannot be obtained and the intermetallic compound becomes coarse. A more preferable slab thickness is 500 mm or less.
- tempering is performed according to the application. This tempering is usually H1n or H2n to prevent erosion, but a soft material may be used depending on the shape and usage.
- Fin material (third form)
- the heat exchanger of the present invention is obtained by manufacturing a fin material that is a material before joining using a material having a single layer joining function, but instead of the fin materials according to the first and second embodiments. It can also be obtained by manufacturing using a material having a bonding function in a single layer shown below. Specifically, Al—Fe—Mn comprising inevitable impurities including Si concentration: 1.0 to 5.0% and Fe: 0.01 to 2.0% as essential elements and the balance Al and Mn. 4.
- Si is an element that generates an Al—Si based liquid phase and contributes to bonding.
- Si concentration is defined as 1.0% to 5.0%.
- the Si concentration is preferably 1.5% to 3.5%, more preferably 2.0% to 3.0%. Since the amount of the liquid phase that oozes out increases as the volume increases and the heating temperature increases, the amount of the liquid phase required during heating depends on the amount of Si required for the structure of the structure to be manufactured and the bonding heating. It is desirable to adjust the temperature.
- Fe has the effect of improving the strength by being slightly dissolved in the matrix, and also has the effect of preventing the strength from being lowered particularly at high temperatures by being dispersed as a crystallized product or a precipitate. .
- the addition amount of Fe is less than 0.01%, not only the above effect is small, but also high purity metal must be used and the cost increases.
- it exceeds 2.0% a coarse intermetallic compound is produced at the time of casting, causing a problem in manufacturability.
- the corrosion resistance decreases.
- the addition amount of Fe is set to 0.01% to 2.0%.
- a preferable addition amount of Fe is 0.2% to 1.0%.
- the aluminum alloy material according to the present invention is heated to the solidus temperature or higher during bonding heating by the MONOBRAZE method. At this time, the aluminum alloy material is deformed mainly by grain boundary sliding. Therefore, as the metal structure, (1) it is desirable that the crystal grains become coarse during bonding heating. (2) Further, when a liquid phase is generated at the grain boundary, deformation due to the grain boundary slip is likely to occur, so that it is desirable to suppress generation of the liquid phase at the grain boundary. In the present invention, the crystal structure after heating becomes coarse, and the metal structure in which the liquid phase generation at the grain boundary is suppressed is defined.
- an Al-based intermetallic compound having an equivalent circle diameter of 0.01 to 0.5 ⁇ m exists as dispersed particles.
- This Al-based intermetallic compound is composed of Al-Fe-based, Al-Fe-Si-based, Al-Mn-Si-based, Al-Fe-Mn-based, Al-Fe-Mn-Si-based compounds, etc. It is an intermetallic compound to be formed.
- An Al-based intermetallic compound having a circle-equivalent diameter of 0.01 to 0.5 ⁇ m does not become a recrystallization nucleus when heated, but functions as pinning particles that suppress the growth of grain boundaries.
- the aluminum alloy material according to the present invention has an Al-based intermetallic compound having an equivalent circle diameter of 0.01 to 0.5 ⁇ m, the recrystallization nuclei are prevented from growing innumerably during heating, and the limited recrystallization nuclei. Since only the crystal grows, the crystal grains after heating become coarse. Further, by collecting solid solution Si in the grains, liquid phase generation at the grain boundaries is relatively suppressed.
- the effects of the Al-based intermetallic compound are more reliably exhibited when the volume density of the Al-based intermetallic compound is in an appropriate range. Specifically, it exists at a volume density of 10 to 1 ⁇ 10 4 pieces / ⁇ m 3 in any part of the material. When the volume density is less than 10 particles / ⁇ m 3 , the pinning effect is too small, so that the number of recrystallized grains that can be grown increases and coarse crystal grains are hardly formed. In addition, since the nuclei for liquid phase generation are reduced, the action of collecting the solid solution Si within the grains is not sufficiently exerted, and the ratio of the solid solution Si within the grains contributing to the growth of the liquid phase generated at the grain boundaries increases. In addition, the deformation resistance is reduced.
- the volume density is within the above range.
- the volume density is preferably 50 to 5 ⁇ 10 3 pieces / ⁇ m 3 , and more preferably 100 to 1 ⁇ 10 3 pieces / ⁇ m 3 .
- Al-based intermetallic compounds with an equivalent circle diameter of less than 0.01 ⁇ m are excluded from the scope of measurement because they are substantially difficult to measure.
- Al-based intermetallic compounds having an equivalent circle diameter of more than 0.5 ⁇ m exist, they do not act effectively as pinning particles, so the effects according to the present invention are small and are not regulated.
- An Al-based intermetallic compound having an equivalent circle diameter of more than 0.5 ⁇ m can act as a nucleus for liquid phase formation.
- an Al-based intermetallic compound having an equivalent circle diameter exceeding 0.5 ⁇ m reduces the effect of collecting solute Si per volume of the compound. Also excluded from the scope.
- the equivalent circle diameter of the Al-based intermetallic compound can be determined by TEM observation of a thin-walled sample by electrolytic polishing.
- the equivalent circle diameter means the equivalent circle diameter. It is preferable to obtain the equivalent circle diameter before joining by analyzing the TEM observation image as a two-dimensional image in the same manner as the SEM observation image.
- the film thickness of the sample is also measured using the EELS method or the like in each field of view observed by TEM. After image analysis of the TEM observation image as a two-dimensional image, the measurement volume is obtained by multiplying the measurement area of the two-dimensional image by the film thickness measured by the EELS method, and the volume density is calculated.
- Si-based intermetallic compounds and Al-based intermetallic compounds can be more accurately distinguished by elemental analysis using EDS or the like.
- the aluminum alloy material having a heat bonding function with a single layer according to the present invention having characteristics in the Si and Fe concentration ranges and the metal structure is in a semi-molten state to supply a liquid phase during bonding heating. This makes it possible to join and has excellent deformation resistance.
- Si type intermetallic compound In addition to the prescription
- Si-based intermetallic compounds having a circle-equivalent diameter of 5.0 to 10 ⁇ m are present in a cross section in the material of 200 pieces / mm 2 or less.
- the Si-based intermetallic compound includes (1) elemental Si, and (2) an element such as Ca or P in part of elemental Si.
- the cross section in the material is an arbitrary cross section of the aluminum alloy material, for example, a cross section along the thickness direction, or a cross section parallel to the plate material surface. From the viewpoint of simplicity of material evaluation, it is preferable to adopt a cross section along the thickness direction.
- the Si-based intermetallic compound having an equivalent circle diameter of 5.0 ⁇ m to 10 ⁇ m becomes a nucleus of recrystallization when heated. For this reason, when the surface density of the Si-based intermetallic compound exceeds 200 / mm 2 , the crystal grains become fine because of many recrystallization nuclei, and the deformation resistance during bonding heating decreases. If the surface density of the Si-based intermetallic compound is 200 pieces / mm 2 or less, since the number of recrystallized nuclei is small, only specific crystal grains grow and coarse crystal grains are obtained, which is resistant to deformation during bonding heating. Improves. The surface density is preferably 20 pieces / mm 2 or less. Note that the smaller the amount of Si-based intermetallic compound having an equivalent circle diameter of 5.0 ⁇ m to 10 ⁇ m, the better the deformation resistance. Therefore, the surface density is most preferably 0 piece / mm 2 .
- the equivalent circle diameter of the Si-based intermetallic compound is limited to 5.0 ⁇ m to 10 ⁇ m is as follows. Although Si-based intermetallic compounds having an equivalent circle diameter of less than 5.0 ⁇ m exist, they were excluded from the subject because they do not work as recrystallization nuclei. In addition, Si-based intermetallic compounds having an equivalent circle diameter exceeding 10 ⁇ m cause cracks during production and are difficult to produce. Therefore, since the Si-based intermetallic compound having such a large equivalent circle diameter is not present in the aluminum alloy, it was also excluded from the object.
- the equivalent circle diameter of the Si-based intermetallic compound can be determined by performing SEM observation (reflection electron image observation) of the cross section.
- the equivalent circle diameter means the equivalent circle diameter. It is preferable to obtain the equivalent circle diameter of the dispersed particles before joining by image analysis of the SEM photograph. The surface density can be calculated from the image analysis result and the measurement area. Further, the Si-based intermetallic compound and the Al-based intermetallic compound can also be distinguished by contrast contrast by SEM-reflection electron image observation. Further, the metal species of the dispersed particles can be more accurately specified by EPMA (X-ray microanalyzer) or the like.
- Si solid solution amount is prescribed
- the aluminum alloy material according to the present invention preferably has a Si solid solution amount of 0.7% or less before bonding by the MONOBRAZE method.
- the Si solid solution amount is a measured value at room temperature of 20 to 30 ° C.
- solute Si diffuses in the solid phase during heating and contributes to the growth of the surrounding liquid phase. If the amount of solute Si is 0.7% or less, the amount of liquid phase generated at the grain boundary due to diffusion of solute Si is reduced, and deformation during heating can be suppressed.
- solute Si is 0.6% or less.
- the lower limit of the amount of solute Si is not specifically limited, it naturally depends on the Si content of the aluminum alloy and the manufacturing method, and is 0% in the present invention.
- a single layer aluminum alloy material having a heat bonding function according to the present invention has a predetermined amount of Si as an essential element in order to improve deformation resistance during bonding heating. And Fe.
- Si as an essential element
- Fe in order to further improve the strength, in addition to the essential elements Si and Fe, one or more selected from a predetermined amount of Mn, Mg and Cu are further added as the first selective additive element. Is done. Even when such a first selective additive element is contained, the volume density of the Al-based intermetallic compound and the surface density of the Si-based intermetallic compound are defined as described above.
- Mn forms Al—Mn—Si, Al—Mn—Fe—Si, and Al—Mn—Fe intermetallic compounds together with Si and Fe and acts as dispersion strengthening, or in the aluminum matrix It is an important additive element that improves the strength by solid solution strengthening by solid solution strengthening. If the amount of Mn added exceeds 2.0%, a coarse intermetallic compound is easily formed and the corrosion resistance is lowered. On the other hand, if the amount of Mn added is less than 0.05%, the above effect is insufficient. Therefore, the amount of Mn added is 0.05 to 2.0% or less. A preferable Mn addition amount is 0.1% to 1.5%.
- Mg undergoes age hardening by Mg 2 Si after bonding heating, and the strength is improved by this age hardening.
- Mg is an additive element that exhibits the effect of improving the strength. If the amount of Mg added exceeds 2.0%, it reacts with the flux to form a high melting point compound, so that the bondability is significantly lowered. On the other hand, if the amount of Mg added is less than 0.05%, the above effect is insufficient. Therefore, the amount of Mg added is 0.05 to 2.0%. A preferable amount of Mg is 0.1% to 1.5%.
- Cu is an additive element that improves the strength by solid solution in the matrix.
- the addition amount of Cu is set to 0.05 to 1.5%.
- a preferable Cu addition amount is 0.1% to 1.0%.
- Second selective additive element in order to further improve the corrosion resistance, in addition to the essential element and / or the first selective additive element, a predetermined amount of Zn, In and Sn is selected. One kind or two or more kinds are further added as a second selective additive element. Even when such a second selective additive element is contained, the volume density of the Al-based intermetallic compound and the surface density of the Si-based intermetallic compound are defined as described above.
- Addition of Zn is effective in improving corrosion resistance due to sacrificial anticorrosive action.
- Zn is dissolved almost uniformly in the matrix, but when a liquid phase is generated, it dissolves into the liquid phase and concentrates in the liquid phase. When the liquid phase oozes out to the surface, the Zn concentration in the oozed portion increases, so that the corrosion resistance is improved by the sacrificial anodic action.
- the sacrificial anticorrosion action for preventing corrosion of tubes and the like can be exerted by using the aluminum alloy material of the present invention for fins. If the amount of Zn added exceeds 6.0%, the corrosion rate increases and the self-corrosion resistance decreases. Therefore, the Zn addition amount is set to 6.0% or less. A preferable Zn addition amount is 0.05% to 6.0%.
- Sn and In have an effect of exerting a sacrificial anodic action.
- the addition amounts of Sn and In are each 0.3% or less.
- a preferable addition amount of Sn and In is 0.05% to 0.3%, respectively.
- the third selective additive element in order to further improve the strength and corrosion resistance, in addition to at least one of the essential element, the first selective additive element and the second selective additive element, One or more selected from a predetermined amount of Ti, V, Cr, Ni and Zr is further added as a third selective additive element. Even when such a third selective additive element is contained, the volume density of the Al-based intermetallic compound and the surface density of the Si-based intermetallic compound are defined as described above.
- Ti and V have the effect of preventing the progress of corrosion in the plate thickness direction by being dissolved in a layer, in addition to improving the strength by solid solution in the matrix.
- the added amount exceeds 0.3%, coarse crystals are generated, which impairs moldability and corrosion resistance. Therefore, the added amounts of Ti and V are each 0.3% or less.
- a preferable addition amount of Ti and V is 0.05% to 0.3%, respectively.
- Cr improves strength by solid solution strengthening, and acts on coarsening of crystal grains after heating by precipitation of Al—Cr intermetallic compounds.
- the addition amount of Cr exceeds 0.3%, it becomes easy to form a coarse intermetallic compound, and the plastic workability is lowered. Therefore, the addition amount of Cr is set to 0.3% or less.
- a preferable addition amount of Cr is 0.05% to 0.3%.
- the amount of Ni added is in the range of 2.0% or less, preferably in the range of 0.05% to 2.0%. When the Ni content exceeds 2.0%, it becomes easy to form a coarse intermetallic compound, and the workability is lowered and the self-corrosion resistance is also lowered.
- Zr precipitates as an Al—Zr intermetallic compound, and exhibits the effect of improving the strength after bonding by dispersion strengthening.
- the Al—Zr-based intermetallic compound acts on the coarsening of crystal grains during heating.
- the addition amount exceeds 0.3%, it becomes easy to form a coarse intermetallic compound, and the plastic workability is lowered. Therefore, the amount of Zr added is set to 0.3% or less.
- a preferable Zr addition amount is 0.05% to 0.3%.
- the fourth selective additive element In the aluminum alloy material according to the present invention, in order to further improve the bondability by improving the characteristics of the liquid phase, the essential elements and the first to third selective additive elements are added. In addition to at least one, one or more selected from a predetermined amount of Be, Sr, Bi, Na, and Ca may be further added as the fourth selective additive element. Even when such a fourth selective additive element is contained, the volume density of the Al-based intermetallic compound and the surface density of the Si-based intermetallic compound are defined as described above.
- Such elements include Be: 0.1% or less, Sr: 0.1% or less, Bi: 0.1% or less, Na: 0.1% or less, and Ca: 0.05% or less. Two or more kinds are added as necessary.
- the preferred ranges of these elements are Be: 0.0001% to 0.1%, Sr: 0.0001% to 0.1%, Bi: 0.0001% to 0.1%, Na: 0.0. 0001% to 0.1%, Ca: 0.0001% to 0.05%.
- These trace elements can improve the bondability by fine dispersion of Si particles, improvement in fluidity of the liquid phase, and the like. If these trace elements are less than the above-mentioned preferable specified range, effects such as fine dispersion of Si particles and improvement of fluidity of the liquid phase may be insufficient. On the other hand, when the above preferred range is exceeded, adverse effects such as a decrease in corrosion resistance occur.
- the aluminum alloy material preferably has a tensile strength before joining by MONOBRAZE method of 80 to 250 MPa. If the tensile strength is less than 80 MPa, the strength required for molding into a product shape is insufficient, and molding cannot be performed. If this tensile strength exceeds 250 MPa, the shape retention after molding is poor, and when assembled as a joined body, a gap is formed between the other members and the jointability deteriorates.
- the tensile strength before bonding by the MONOBRAZE method is a value measured at room temperature of 20 to 30 ° C.
- the ratio (T / T0) of the tensile strength (T0) before joining by the MONOBRAZE method to the tensile strength (T) after joining is preferably in the range of 0.6 to 1.1. If (T / T0) is less than 0.6, the strength of the material may be insufficient, and the function as a structure may be impaired. If it exceeds 1.1, precipitation at the grain boundary becomes excessive, and the grain boundary Corrosion may occur easily.
- the amount of solid solution Si in the matrix decreases due to the formation of an Al—Fe—Mn—Si intermetallic compound having an equivalent circle diameter of 0.01 ⁇ m to 0.5.
- the amount of solute Si supplied to the grain boundary during bonding heating is further reduced, generation of a liquid phase at the grain boundary is suppressed, and deformation resistance is improved.
- the continuous casting method is not particularly limited as long as it is a method of continuously casting a plate-shaped ingot such as a twin roll type continuous casting and rolling method or a twin belt type continuous casting method.
- the twin-roll type continuous casting and rolling method is a method in which molten aluminum is supplied between a pair of water-cooled rolls from a refractory hot-water supply nozzle, and a thin plate is continuously cast and rolled.
- the Hunter method, the 3C method, and the like are known.
- the twin belt type continuous casting method is a method in which molten metal is poured between rotating belts facing each other up and down and solidified by cooling from the belt surface to form a slab. This is a continuous casting method in which a slab is continuously drawn out and wound into a coil.
- the cooling rate during casting is several to several hundred times faster than the semi-continuous casting method.
- the cooling rate in the semi-continuous casting method is 0.5 to 20 ° C./second
- the cooling rate in the twin roll type continuous casting and rolling method is 100 to 1000 ° C./second.
- the dispersed particles generated during casting have a feature that they are finely and densely distributed as compared with the semi-continuous casting method.
- the generation of coarse crystals is suppressed, and the crystal grains during bonding heating become coarse.
- the cooling rate is high, the amount of solid solution of the additive element can be increased.
- the cooling rate in the twin roll continuous casting and rolling method is preferably 100 to 1000 ° C./second. If it is less than 100 ° C./second, it is difficult to obtain a target metal structure, and if it exceeds 1000 ° C./second, stable production becomes difficult.
- the speed of the rolled plate when casting by the twin roll type continuous casting and rolling method is preferably 0.5 to 3 m / min.
- the casting speed affects the cooling rate.
- a sufficient cooling rate as described above cannot be obtained and the compound becomes coarse.
- it exceeds 3 m / min the aluminum material is not sufficiently solidified between rolls during casting, and a normal plate-shaped ingot cannot be obtained.
- the molten metal temperature when casting by the twin roll type continuous casting and rolling method is preferably in the range of 650 to 800 ° C.
- the molten metal temperature is the temperature of the head box immediately before the hot water supply nozzle.
- 650 ° C. coarse intermetallic compound dispersed particles are generated in the hot water supply nozzle, and they are mixed into the ingot to cause a sheet break during cold rolling.
- the molten metal temperature exceeds 800 ° C., the aluminum material is not sufficiently solidified between the rolls during casting, and a normal plate-shaped ingot cannot be obtained.
- a more preferable molten metal temperature is 680 to 750 ° C.
- the plate thickness of the plate-shaped ingot cast by the twin roll continuous casting and rolling method is preferably 2 mm to 10 mm. In this thickness range, the solidification rate at the central portion of the plate thickness is fast, and a uniform structure can be easily obtained.
- the plate thickness is less than 2 mm, the amount of aluminum passing through the casting machine per unit time is small, and it becomes difficult to stably supply the molten metal in the plate width direction.
- the plate thickness exceeds 10 mm, winding with a roll becomes difficult.
- a more preferable plate thickness of the plate-shaped ingot is 4 mm to 8 mm.
- annealing is performed at 250 to 550 ° C. for 1 to 10 hours. This annealing may be performed in any process except the final cold rolling in the manufacturing process after casting, and it is necessary to perform it once or more.
- the upper limit of the number of times of annealing is preferably 3 times, more preferably 2 times. This annealing is performed in order to soften the material and make it easy to obtain the desired material strength by final rolling. By this annealing, the size and density of the intermetallic compound in the material and the solid solution amount of the additive element are optimally adjusted. I can do it.
- the annealing temperature is less than 250 ° C.
- the softening of the material is insufficient, and the TS before brazing heating becomes high.
- TS before brazing heating is high, since the moldability is inferior, the core dimensions are deteriorated, and as a result, the durability is lowered.
- annealing is performed at a temperature exceeding 550 ° C.
- the amount of heat input to the material during the manufacturing process becomes too large, so that the intermetallic compounds are coarsely and sparsely distributed. Coarse and loosely distributed intermetallic compounds are difficult to incorporate solid solution elements, and the amount of solid solution in the material is difficult to decrease. Further, the above effect is not sufficient at an annealing temperature of less than 1 hour, and the above effect is saturated at an annealing time exceeding 10 hours, which is economically disadvantageous.
- the tempering may be O material or H material.
- the final cold rolling rate is important.
- the final cold rolling rate is 50% or less, and the preferable final cold rolling rate is 5% to 50%.
- the final cold rolling rate exceeds 50%, a large number of recrystallization nuclei are generated during heating, and the crystal grain size after bonding heating becomes fine.
- the final cold rolling reduction is less than 5%, the manufacture may be substantially difficult.
- Aluminum coating is a film composed mainly of aluminum and aluminum oxide.
- the aluminum coating formed on the roll surface during casting improves the wetting between the roll surface and the molten metal and improves the heat transfer between the roll surface and the molten metal.
- twin roll continuous casting and rolling may be performed with a molten aluminum of 680 to 740 ° C. at a rolling load of 500 N / mm or more, or before the start of twin roll continuous casting and rolling.
- the wrought aluminum alloy sheet heated to 300 ° C. or higher may be rolled twice or more at a rolling reduction of 20% or more.
- the molten aluminum or aluminum alloy plate used for forming the aluminum coating is particularly preferably a 1000 series alloy with few additive elements, but the coating can be formed using other aluminum alloy systems.
- the thickness of the aluminum coating always increases, so boron nitride or carbon release agent (graphite spray or soot) is applied to the roll surface at 10 ⁇ g / cm 2 to suppress further formation of the aluminum coating. It can also be physically removed with a brush roll or the like.
- the aluminum coating thickness is preferably 1 to 500 ⁇ m. Thereby, the cooling rate of the molten metal is optimally adjusted, and it becomes possible to cast an aluminum alloy having an intermetallic compound density and an Si solid solution amount that are excellent in deformation resistance during bonding heating. If the aluminum coating thickness is less than 1 ⁇ m, the wettability between the roll surface and the molten metal is poor, and the contact area between the roll surface and the molten metal becomes small. Thereby, the heat transferability between the roll surface and the molten metal deteriorates, and the cooling rate of the molten metal decreases. As a result, the intermetallic compound becomes coarse and a desired intermetallic compound density cannot be obtained.
- the roll surface and the molten metal may be locally non-contact. In that case, the ingot is remelted and the molten metal having a high solute concentration oozes out to the surface of the ingot to cause surface segregation, and there is a possibility that a coarse intermetallic compound is formed on the surface of the ingot.
- the aluminum coating thickness exceeds 500 ⁇ m, the wettability between the roll surface and the molten metal is improved, but the heat transferability between the roll surface and the molten metal is significantly deteriorated because the coating is too thick.
- the aluminum coating thickness is more preferably 80 to 410 ⁇ m.
- FIGS. In the twin roll type continuous casting and rolling method, as shown in FIGS. It is carried out by injecting a molten aluminum alloy 1 through a nozzle tip 4 made of refractory.
- the region 2 during continuous casting can be roughly divided into a rolled region 5 and a non-rolled region 6.
- the aluminum alloy in the rolling region 5 has been solidified to become an ingot, and a roll separating force is generated against the rolling of the roll.
- the center portion of the plate thickness exists as an unsolidified molten metal, so that no roll separation force is generated.
- the position of the solidification start point 7 hardly moves even if the casting conditions are changed.
- the cooling rate can be controlled by measuring the rolling load 8, which is the vertical component of the roll separation force, that is, the increase / decrease of the rolling region.
- the molten metal sump is a solid-liquid interface between the solidified part and the unsolidified part at the time of casting, and when this interface deeply penetrates in the rolling direction to form a valley shape, the sump is deep, On the other hand, if the interface is nearly flat without entering the rolling direction, the sump is shallow.
- the rolling load is preferably 500 to 5000 N / mm.
- the rolling region 4 is small and the melt sump is deep. Thereby, a cooling rate becomes low, a coarse crystallized substance is easy to be formed, and it becomes difficult to form a fine precipitate.
- the number of recrystallized grains having coarse crystallized crystals as nuclei increases during bonding heating, and the crystal grains become finer, so that they are easily deformed.
- an appropriate pinning effect cannot be obtained, and the amount of Si solid solution increases, so that the liquid phase generated at the grain boundary during bonding heating increases and is likely to deform. .
- solute atoms gather at the center of the plate thickness and cause centerline segregation.
- members other than the fin material are not particularly defined as materials used in the manufacture of the heat exchanger of the present invention, but the following forms are preferable.
- the tube material combined with the fin material may be a brazing aluminum alloy material that does not have a brazing material on the outer surface.
- a brazing aluminum alloy material that does not have a brazing material on the outer surface.
- 3000-series and 1000-series extruded multi-hole pipes, and ERW pipes in which a 7000-series sacrificial anode material is clad on the outer surface of a 3000-series core material are used.
- these tube materials may be further coated with Zn spraying or Zn substitution flux on the surface.
- the header material arranged at both ends of the tube material is preferably an aluminum alloy member to which a brazing material for joining the tube material is supplied.
- Extruded / drawn material clad with a material, or a 3000 series extruded / drawn material coated with paste braze or the like is used.
- these materials may be further subjected to cladding of a sacrificial anode material, Zn spraying on the surface, application of Zn substitution flux, and the like. These materials are pressed and used as header materials.
- the heat exchanger according to the present invention is manufactured by assembling each of the above members into the shape of a heat exchanger, then performing a treatment such as flux application, and performing heat bonding in a furnace.
- the manufacturing method of the heat exchanger according to the present invention particularly the joining method will be described in detail below.
- the heat exchanger according to the present invention without using a brazing material, it utilizes the joining ability exhibited by the fin material of the aluminum alloy itself, but considering the use as a fin material of the heat exchanger, The deformation of the fin material itself is a big issue.
- the metal structure of the above-mentioned heat exchanger fin is formed during this joining. Therefore, it is important to manage the bonding heating conditions.
- the temperature is higher than the solidus temperature at which the liquid phase is generated in the fin material used in the present invention and lower than the liquidus temperature, and the liquid phase is generated in the fin material, resulting in a decrease in strength.
- heating is performed for a time required for joining at a temperature below the temperature at which the shape cannot be maintained.
- the ratio of the mass of the liquid phase generated in the aluminum alloy material to the total mass of the aluminum alloy material as the fin material is 5% or more. It is necessary to join at a temperature of 35% or less. Since joining is difficult when the liquid phase is small, the liquid phase ratio is preferably 5% or more. When the liquid phase ratio exceeds 35%, the amount of the liquid phase to be generated is too large, and the aluminum alloy material is greatly deformed at the time of bonding and heating, so that the shape cannot be maintained.
- a preferable liquid phase ratio is 5 to 30%, and a more preferable liquid phase ratio is 10 to 20%.
- the time during which the liquid phase ratio is 5% or more is 30 seconds or more and 3600 seconds or less. Is preferred. More preferably, the time during which the liquid phase ratio is 5% or more is 60 seconds or more and 1800 seconds or less, whereby further sufficient filling is performed and reliable bonding is performed. If the time during which the liquid phase ratio is 5% or more is less than 30 seconds, the joint may not be sufficiently filled with the liquid phase. Furthermore, there is a possibility that the region B around the crystal grain boundary is not sufficiently formed and sufficient corrosion resistance cannot be obtained.
- the time during which the liquid phase ratio is 5% or more exceeds 3600 seconds, the deformation of the aluminum alloy material may proceed. Furthermore, there is a possibility that the region B around the crystal grain boundary is excessively formed. In the bonding method according to the present invention, the liquid phase moves only in the very vicinity of the bonded portion, so that the time required for filling does not depend on the size of the bonded portion.
- the bonding temperature may be 580 to 640 ° C.
- the holding time at the bonding temperature may be about 0 to 10 minutes.
- 0 minutes means that the cooling is started as soon as the temperature of the member reaches a predetermined joining temperature.
- the holding time is more preferably 30 seconds to 5 minutes.
- the bonding temperature is set to a temperature at which the prescribed liquid phase ratio is obtained from the composition.
- the liquid phase ratio defined in the present invention can be usually obtained by lever principle from the alloy composition and the maximum attainable temperature using an equilibrium diagram.
- the phase diagram can be used to determine the liquid phase ratio using the principle of leverage.
- the liquid phase ratio can be obtained using equilibrium calculation diagram software.
- the equilibrium calculation phase diagram software incorporates a technique for determining the liquid phase ratio based on the lever principle using the alloy composition and temperature.
- Equilibrium calculation state diagram software includes Thermo-Calc; Thermo-Calc Software AB, etc.
- the heating atmosphere in the heat treatment is preferably a non-oxidizing atmosphere substituted with nitrogen, argon or the like.
- better bondability can be obtained by using a non-corrosive flux.
- non-corrosive flux coating method examples include a method of sprinkling the flux powder after assembling the members to be joined, a method of spraying the flux powder suspended in water, and the like.
- the adhesion of the coating can be improved by mixing and applying a binder such as an acrylic resin to the flux powder.
- the non-corrosive flux used for obtaining a normal flux function include KAlF 4 , K 2 AlF 5 , K 2 AlF 5 .H 2 O, K 3 AlF 6 , AlF 3 , KZnF 3 , K 2 SiF 6 and the like.
- cesium-based fluxes such as Cs 3 AlF 6 , CsAlF 4 .2H 2 O, Cs 2 AlF 5 .H 2 O, and the like.
- the aluminum alloy material for heat exchanger fins according to the present invention can be satisfactorily bonded by the heat treatment and the control of the heating atmosphere as described above.
- the fin material is a thin material, the shape may not be maintained if the stress generated inside is too high.
- the stress generated in the fin material can be maintained at a relatively small stress so that a good shape can be maintained.
- the maximum value of the stress generated in the fin material is P (kPa) and the liquid phase ratio is V (%), P ⁇ 460 ⁇ If the condition of 12V is satisfied, a very stable junction can be obtained.
- the value indicated by the right side (460-12V) of this equation is the critical stress, and if a stress exceeding this value is applied to the fin material, there is a possibility that a large deformation will occur.
- the stress generated in the fin material is obtained from the shape and load. For example, it can be calculated using a structural calculation program or the like.
- First Example Fins, tubes, and headers were formed using the following materials, assembled into the shape of a heat exchanger as shown in FIG. 5, and then joined and heated to produce a heat exchanger.
- the total rolling reduction was 93%, and the roll was rolled to a thickness of 27 mm at this stage. Furthermore, in the hot rough rolling stage, the pass having a reduction rate of 15% or more was set to 5 times.
- the rolled material was further rolled to a thickness of 3 mm through a hot finish rolling stage.
- the rolled plate was rolled to a thickness of 0.09 mm. Further, the rolled material was subjected to an intermediate annealing process at 380 ° C. for 2 hours, and finally rolled to a final thickness of 0.07 mm in the final cold rolling stage to obtain a test material.
- a cast ingot was produced by a twin-roll continuous casting and rolling method (CC).
- the melt temperature at the time of casting by the twin roll type continuous casting and rolling method was 650 to 800 ° C., and the casting speed was 0.6 m / min.
- the cooling rate is in the range of 300 to 700 ° C./second by controlling the aluminum coating thickness and controlling the sump in the molten metal by rolling load. it is conceivable that.
- a cast ingot having a width of 130 mm, a length of 20000 mm, and a thickness of 7 mm was obtained.
- the obtained plate-shaped ingot is cold-rolled to 0.7 mm, after intermediate annealing at 420 ° C. ⁇ 2 hours, cold-rolled to 0.071 mm, and then annealed at 350 ° C. ⁇ 3 hours for the second time. Later, it was rolled to 0.050 mm at a final cold rolling rate of 30% to obtain a test material.
- the grain refiner was added at a molten metal temperature of 680 ° C to 750 ° C. At that time, the molten metal flowing through the tub connecting between the molten metal holding furnace and the head box just before the hot water supply nozzle was continuously charged at a constant speed using a wire-shaped crystal grain refining agent rod.
- the crystal grain refining agent an Al-5Ti-1B alloy was used, and the addition amount was adjusted to be 0.002% in terms of B amount.
- a two-layer brazing sheet was obtained by cladding the above-described DC casting ingot having a width of 1000 mm, a length of 3000 mm, and a thickness of 400 mm with a skin material (brazing material) shown in Table 1.
- Cold rolling after cladding, intermediate annealing, and cold rolling were performed, and the second annealing and final cold rolling were performed in the same manner as other fin materials.
- the number density of Al—Fe—Mn—Si intermetallic compounds in the produced plate those with an equivalent circle diameter of less than 0.01 to 0.5 ⁇ m are cross sections along the plate thickness direction. This was measured by TEM observation. A sample for TEM observation was prepared using electrolytic etching. A field of view having an average film thickness of 50 to 200 ⁇ m was selected and observed. The Si-based intermetallic compound and the Al-based intermetallic compound can be distinguished by performing mapping by STEM-EDS. Observation was performed 10 times at 100000 times for each sample, and the number of Al—Fe—Mn—Si intermetallic compounds having an equivalent circle diameter of 0.01 to less than 0.5 ⁇ m was measured by image analysis of each TEM photograph. The number density was calculated by dividing by the measurement area.
- the Al—Fe—Mn—Si intermetallic compounds in the manufactured plate material those of 0.5 to less than 5 ⁇ m, those of 5 to 10 ⁇ m, and those of 0.5 to 5 ⁇ m and over 5 ⁇ m
- the number density of the ⁇ 10 ⁇ m Si intermetallic compound was measured by SEM observation of a cross section along the plate thickness direction.
- the Si-based intermetallic compound and the Al—Fe—Mn—Si-based intermetallic compound were distinguished using SEM-backscattered electron image observation and SEM-secondary electron image observation. In the backscattered electron image observation, an Al-based intermetallic compound provides a strong white contrast, and an Si-based intermetallic compound provides a low white contrast.
- Si-based intermetallic compound Since the Si-based intermetallic compound has a weak contrast, it may be difficult to distinguish fine particles. In this case, a sample etched for about 10 seconds with a colloidal silica suspension after surface polishing was observed with a SEM-secondary electron image. Particles that provide a strong black contrast are Si-based intermetallic compounds. Observation is performed for each 5 fields, and SEM photographs of each field are subjected to image analysis. Al-Fe-Mn-Si intermetallic compounds with equivalent circle diameters of 0.5 to 5 ⁇ m and 5 to 10 ⁇ m in the samples are observed. And the number density of Si-based intermetallic compounds of 0.5 ⁇ m to 5 ⁇ m and more than 5 ⁇ m to 10 ⁇ m were examined.
- Table 1 also shows the number density of the Al—Fe—Mn—Si intermetallic compound and the Si intermetallic compound.
- a corrugated fin material having a fin thickness of 8 mm, a fin pitch of 3 mm, and a length of 400 mm was obtained by corrugating a fin material having a thickness of 0.07 mm.
- test material having the alloy composition shown in Table 2 was used for the tube. As shown in Table 2, an extruded multi-hole tube having a length of 440 mm was used as a tube material. The state of the outer surface of the tube material is also shown in Table 2.
- a clad pipe core material + skin material (brazing material) having a thickness of 1.3 mm and a diameter of 20 mm shown in Table 3 is cut into a length of 400 mm, and a total of 30 tubes are arranged according to the tube thickness and fin height. What processed the insertion hole was used.
- L / T was obtained as described above, assuming that the crystal grain size of the Al matrix in the L-LT cross section of the fin was L ⁇ m and the crystal grain diameter of the Al matrix in the L-ST cross section was T ⁇ m.
- the natural potential of the fin after heating and the natural potential of the fin ⁇ the natural potential of the fillet were measured. The natural potential was measured in a solution in which 5% by weight NaCl was dissolved in pure water and pH was adjusted to 3 by adding acetic acid using an Ag / AgCl electrode.
- part (fin or fillet) was used for the sample to measure.
- a SWATT test was conducted as a corrosion test on the heat exchanger manufactured as described above.
- the test time was 1000 hours, and the presence or absence of leakage of the tube was evaluated after the test was completed. Thereafter, a sample as shown in FIG. 7 was cut out from the central portion of the heat exchanger where there was no leakage of the tube, the corrosion product was removed, the sample was embedded in a resin, and the cross section was observed after the cross section was polished. Then, from the cross section of the field of view having a total fin length of 2 mm, the presence or absence of a hollow corrosion portion defined as shown in FIG. 7 was observed.
- the cross-section of the fin after the corrosion test was observed, and the presence and extent of hollow-out corrosion was determined based on whether or not there was corrosion above a predetermined level inside the outermost portion of the fin within the field of view.
- the L150 ⁇ m ⁇ t70 ⁇ m guide fits even at one place in the field of view, there is no corrosion that becomes ⁇ in the field of view, but there is one corrosion in which the L150 ⁇ m ⁇ t30 ⁇ m guide fits in the field of view.
- Second Example Fins, tubes, and headers were formed using the following materials, assembled into the shape of a heat exchanger in the same manner as in the first example, and then joined and heated to produce a heat exchanger.
- Test materials having the alloy composition shown in Table 5 were used for the fin material.
- “ ⁇ ” in the alloy composition indicates that it is below the detection limit, and “remainder” includes inevitable impurities.
- the influence of a trace amount of additive element in the fin material was examined.
- a cast ingot was manufactured using the above test material.
- F5 to F30 were processed in the same manner as F1 and F3 in the first example.
- plate material was also performed similarly to 1st Example.
- Table 6 shows the number density of the measured Al—Fe—Mn—Si intermetallic compound and Si intermetallic compound.
- a corrugated fin material was processed in the same manner as in the first example, and a heat exchanger was created by combining with the same tube material and header material used in the first example.
- the heat exchanger thus produced was evaluated in the same manner as in the first example. Table 7 shows the evaluation results.
- Third Example Fins, tubes, and headers were formed using the following materials, assembled in the shape of a heat exchanger as in the first example, and then joined and heated to produce a heat exchanger.
- the influence of the main additive element was examined.
- the total rolling reduction was 93%, and the roll was rolled to a thickness of 27 mm at this stage. Furthermore, in the hot rough rolling stage, the pass having a reduction rate of 15% or more was set to 5 times.
- the rolled material was further rolled to a thickness of 3 mm through a hot finish rolling stage.
- the rolled plate was rolled to a thickness of 0.145 mm.
- the rolled material was subjected to an intermediate annealing process at 380 ° C. for 2 hours, and finally rolled to a final sheet thickness of 0.115 mm in the final cold rolling stage to obtain a test material.
- a cast ingot was produced by a twin roll continuous casting and rolling method (CC).
- the melt temperature at the time of casting by the twin roll type continuous casting and rolling method was 650 to 800 ° C., and the casting speed was 0.6 m / min.
- the cooling rate is in the range of 300 to 700 ° C./second by controlling the aluminum coating thickness and controlling the sump in the molten metal by rolling load. it is conceivable that.
- a cast ingot having a width of 130 mm, a length of 20000 mm, and a thickness of 7 mm was obtained.
- the obtained plate-shaped ingot was cold-rolled to 0.7 mm, and after intermediate annealing at 420 ° C. ⁇ 2 hours, it was cold-rolled to 0.1 mm and subjected to the second annealing at 350 ° C. ⁇ 3 hours. Later, it was rolled to 0.07 mm at a final cold rolling rate of 30% to obtain a test material.
- the grain refiner was added at a molten metal temperature of 680 ° C to 750 ° C. At that time, the molten metal flowing through the tub connecting between the molten metal holding furnace and the head box just before the hot water supply nozzle was continuously charged at a constant speed using a wire-shaped crystal grain refining agent rod.
- the crystal grain refining agent an Al-5Ti-1B alloy was used, and the addition amount was adjusted to be 0.002% in terms of B amount.
- the particle distribution evaluation of the manufactured plate material was performed in the same manner as in the first example.
- Table 9 shows the number density of the measured Al—Fe—Mn—Si intermetallic compound and Si intermetallic compound.
- the fin material was a corrugated fin material obtained by corrugating a fin material having a plate thickness of 0.115 mm and having a fin crest height of 8 mm, a fin pitch of 3 mm, and a length of 400 mm.
- the tube and header used were the same as those used in the first example.
- the heat exchanger thus produced was evaluated in the same manner as in the first example.
- Table 10 shows the evaluation results.
- a heat exchanger in which a working fluid does not leak over a long period of time even in a highly corrosive environment, and a decrease in cooling performance due to corrosion is suppressed.
- a heat exchanger for room air conditioners and a heat exchanger for car air conditioners is suitably used for a heat exchanger for room air conditioners and a heat exchanger for car air conditioners.
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Abstract
Description
特許文献5には、単層のアルミニウム合金材を用いて接合体を製造する方法において、合金組成や接合中の温度、加圧、表面性状などを制御することで、良好な接合を得ると共に変形がほとんど起こらない接合方法が記載されている。
特許文献6には、接合部材を用いることなく接合した接合体において、一方のアルミニウム合金材の成分と組織中の孔食電位差を制御することで、高耐食性の接合体が得られることが記載されている。
1.領域A及びBにおけるAl-Fe-Mn-Si系金属間化合物の数密度
本発明の熱交換器は、製造時の材料とフィンの組織を制御することによりフィンの自己耐食性、特に中抜け腐食を抑制するものである。本発明に係る熱交換器のフィンの断面組織の模式図を、図1(a)に示す。カソードとなる円相当径0.1~2.5μmの微細なAl-Fe-Mn-Si系金属間化合物が分散しているマトリクス(以下、「領域A」という)が、表面から内部に存在している。また、マトリクスの結晶粒界の周囲には、この微細なAl-Fe-Mn-Si系金属間化合物がほとんど分散していない領域(以下、「領域B」という)が存在している。これら組織は、図8の組織と同様に、結晶粒界のごく近傍、領域A、領域Bの順で腐食が発生し易い(結晶粒界のごく近傍が最も腐食が発生し易く、領域Bが最も腐食が発生し難い)。従って、本発明に係る熱交換器のフィンは、腐食環境下において、まず結晶粒界のごく近傍が腐食するが(図1(b))、その外側に腐食が進行し難い領域Bが存在しているため、結晶粒界近傍からマトリクス内への腐食の進行が抑制される。一方、表面には領域Bより腐食され易い領域Aが存在しており、表面から腐食が進行する(図1(c))。この領域Aでは、カソードとなるAl-Fe-Mn-Si系金属間化合物が微細に分散しているため、厚さ方向への腐食の優先的な進行が抑制され三次元全体に拡がる腐食形態となる。従って、本発明の熱交換器のフィンでは、粒界腐食が発生した後に表面から領域Aで全体的に腐食が進行し、フィンにろうクラッド材を用いた従来の熱交換器のようなフィンの中抜け腐食は発生しない。
本発明の熱交換器のフィンでは、結晶粒界の長さ当たりにおける領域Bの平均面積をsμmとして、sが2<s<40を満たすのが好ましい。図2に示すように、sは、フィンの断面組織の測定によって求められる。すなわち、一定の視野のフィン断面より、結晶粒界の合計長さ(L1+L2+・・・+Ln)と、結晶粒界に接する領域Bの合計面積(s1+s2+・・・+sn)を測定し、s={(s1+s2+・・・+sn)/(L1+L2+・・・+Ln)}×(1/2)によって求められる。なお、一定の視野とは、少なくとも0.1mm2以上の視野であることが望ましい。
(1)まず、アルミニウム材のフィンのL-ST断面を鏡面研磨し、ケラーエッチングの後に光学顕微鏡にて複数個所観察する。
(2)観察像が得られたら、その像にある結晶粒界を最初に同定し、全ての結晶粒界の長さの和(L1+L2+・・・+Ln)を求める。結晶粒界に液相が浸透している試料では、ケラーエッチングで線上に黒く観察される部位が結晶粒界である。線上に黒く観察される部位は、部分的に不連続であっても、仮想線を引くことで直線が一致する場合は、空白部も粒界とみなす。結晶粒界への液相の浸透が少ないサンプルであり、結晶粒界が不明瞭である場合には、同じ視野を陽極酸化法にて処理した後に光学顕微鏡にて観察することで結晶粒界を同定することができる。また、EBSPによる分析によって結晶粒界を同定することもできる。
(3)結晶粒界が同定されたら、ケラーエッチング観察像にて、その周囲に領域Bが存在するかどうかを調べる。領域BはAl-Fe-Mn-Si系金属間化合物が5.0×104個/mm2未満であることから、4.4μm四方の正方形の中に1個もAl-Fe-Mn-Si系金属間化合物(以下、「粒子」と呼ぶ)がない領域が領域Bであるとし、距離4.4μm以内にある粒子を互いに結んでいくことで、領域Aと領域Bの境界線を引けるとした。ただし、その方法では粒界に沿って幅4.4μm以下に形成されている領域Bが検出されない。請求項2に2<s<40μmと規定されるように、粒界の周囲に形成される領域Bは2μmを超えれば効果を奏することがわかっている。そこで、粒子と粒子の場合は距離4.4μm以内にあるもの同士を線で結ぶのに対して、粒界と粒子においては距離2.0μm以内にある粒子と線を引くことで領域Aと領域Bの境界線を引くこととした。
(4)境界線を引く際は、図9のグレー部に示すように、粒界の周囲に距離4.4μm以内に粒子が互いに存在しないようなB候補をまず見つける。そして、図10に示すように、領域B候補と接する粒界の一方の端部において、結晶粒界と結晶粒界から距離2.0μm以内にある粒子を線で結ぶ。次に、その粒子から距離4.4μm以内にある粒子を線で結ぶ。その際、領域A側には無数にそのような粒子が見つかるので、もっとも領域B側にある粒子だけを結べばよい。上記の行為を繰り返し、もう一方の粒界端部に到達したら、その結線と粒界で囲まれた領域が粒界の周囲に存在する領域Bである。
(5)上記のようにして、観察像中にある全ての「粒界の周囲に存在する領域B」を同定し、その面積の和(s1+s2+・・・+sn)を求める。この面積の和を、同じ観察像中にある結晶粒界の長さの和(L1+L2+・・・+Ln)で割り、更に1/2とすることで、平均面積sμmを求めることができる。
(6)なお、領域Aと領域Bの境界線を引く際に留意すべきことがある。1つ目は、図10の粒子Aに示すように、距離4.4μm以内の粒子を1、2、3・・・個と結んでいく際に、n番目の粒子から距離4.4μm以内の粒子が、(n-1)番目の粒子以外に見つからない場合である。この場合は、n番目の粒子は領域B中に属する粒子と判断して線を結ばないこととする。図10を例にすると、粒子Aと粒子Bはともに領域B中の粒子と認識される。また、(n-1)番目の粒子も、n番目の粒子以外に距離4.4μm以内に粒子がない場合は、同様に領域B中に属すると判断する。これは、粒界から距離2μm以内にある粒子を結ぶ際も同様である。2つ目は、図11に示すように、粒界の一方の端部から線を結んでいった際に、もう一方の端部が粒界ではなく表面になってしまった場合である。この場合は、図11のグレー部に示すように粒界から距離40μmまでの領域Bを「粒界の周囲に存在する領域B」として測定する。表面において粒界から距離40μmを超えて遠くまで続く領域Bは、表面の腐食速度を抑制する一方で、内部の腐食を優先的に起こし、中抜け腐食の原因となることから、ここではその他の領域Bと区別して測定する。
また、本発明において領域Aは表層からフィンの厚さ方向の内部まで分布しているが、図1(a)に示すように、結晶粒界の周囲や円相当径1μmを超える晶出物粒子の周りなどに、領域Bも表層から厚さ方向の内部まで斑に混在する場合がある。しかしながら、フィンの表面における領域Aの面積占有率が60%以上であれば、腐食は表層から全面腐食的に起こり、中抜け腐食や厚さ方向への急速な腐食の進展は発生せず、表層から全体的な腐食が進行する。従って、上記面積占有率を60%以上とするのが好ましい。
本発明の熱交換器は特にフィンの中抜け腐食を防ぐことを発明の要点としているが、高腐食環境下で使用されることを想定しているため、フィン以外の部位も高い耐食性を有するのが好ましい。
更に本発明の熱交換器で、フィンのL-LT断面でのAlマトリクスの結晶粒径をLμm、フィンのL-ST断面におけるAlマトリクスの結晶粒の板厚方向の平均長さをTμmとした場合、L≧100とするのが好ましく、また、L/T≧2とするのが好ましい。なお、板状フィンの場合に、長手方向をL、幅方向をLT、板厚方向をSTと定め、L方向とLT方向からなる断面をL-LT断面、L方向とST方向からなる断面をL-ST断面とそれぞれ定めている。
更に本発明の熱交換器では、フィンの自然電位が-910mV以上であるのが好ましい。フィンの自然電位が-910mV未満の場合は、フィンの腐食が顕著に進行する虞がある。フィンの自然電位の上限値は特に規定するものではなく、フィン材の合金組成と製造条件、フィン材とチューブ材との接合条件によって決まるが、本発明では、-750mVである。
(1)TS-Fillet≦200mV、
(2)Fillet≧-950mV
(3)TB-TS≧100mV
(4)TS≧-950mV
本発明の熱交換器は、接合する前の材料であるフィン材に単層で接合機能を有する材料を用いて製造することにより得られる。第1の形態に係るフィン材は、具体的には、フィン材として、Si:1.0~5.0質量%(以下、単に「%」と記す)、Fe:0.1~2.0%、Mn:0.1~2.0%を必須元素として含有し、残部Al及び不可避的不純物からなるアルミニウム合金を用いる。更に、このアルミニウム合金において、0.5~5μmの円相当径を有するSi系金属間化合物が250~7×104個/mm2存在し、5μmを超える円相当径を有するAl-Fe-Mn-Si系金属間化合物が10~1000個/mm2存在する。以下、このアルミニウム合金の特徴について詳細に説明する。
Si:1.0~5.0%
SiはAl-Si系の液相を生成し、接合に寄与する元素である。但し、Si含有量が1.0%未満の場合は十分な量の液相を生成することができず、液相の染み出しが少なくなり、接合が不完全となる。一方、5.0%を超えるとアルミニウム合金材中の液相の生成量が多くなるため、加熱中の材料強度が極端に低下し、熱交換器の形状維持が困難となる。従って、Si含有量を1.0%~5.0%と規定する。このSi含有量は、好ましくは1.5%~3.5%であり、より好ましくは2.0%~3.0%である。尚、染み出す液相の量は板厚が厚く、加熱温度が高いほど多くなるので、加熱時に必要とする液相の量は、製造する熱交換器の構造に応じて必要となるSi含有量や接合加熱温度を調整することが好ましい。
Feはマトリクスに若干固溶して強度を向上させる効果を有するのに加えて、晶出物として分散して特に高温での強度低下を防ぐ効果を有する。Feは、その含有量が0.1%未満の場合、上記各効果が不十分となるだけでなく、高純度の地金を使用する必要がありコストが増加する。また、2.0%を超えると、鋳造時に粗大な金属間化合物が生成し、製造性に問題が生じる。また、熱交換器が腐食環境(特に液体が流動するような腐食環境)に曝された場合には耐食性が低下する。更に、接合時の加熱によって再結晶した結晶粒が微細化して粒界密度が増加するため、接合前後で寸法変化が大きくなる。従って、Feの添加量は0.1%~2.0%とする。好ましいFe含有量は、0.2%~1.0%である。
Mnは、SiとともにAl-Mn-Si系の金属間化合物を形成し、分散強化として作用し、或いは、アルミニウム母相中に固溶して固溶強化により強度を向上させる重要な添加元素である。Mn含有量が0.1%未満では上記各効果が不十分となり、2.0%を超えると粗大金属間化合物が形成され易くなり耐食性を低下させる。従って、Mn含有量は0.1%~2.0%とする。好ましいMn含有量は、0.3%~1.5%である。
次に、本発明の熱交換器用のフィン材の金属組織における特徴について説明する。このフィン材に用いるアルミニウム合金は、0.5~5μmの円相当径を有するSi系金属間化合物が、数密度で250~7×104個/mm2存在することを特徴とする。ここで、Si系金属間化合物とは、(1)単体Si、及び(2)単体Siの一部に他の元素を含むものであり、他の元素としては、Ca、Pなどが挙げられる。このようなSi系金属間化合物は、後述するように液相発生プロセスにおいて液相生成に寄与する。なお、上記数密度は、アルミニウム合金材の任意の断面におけるものであり、例えば厚さ方向に沿った断面でもよく、板材表面と平行な断面でもよい。材料評価の簡便性の観点から、厚さ方向に沿った断面を採用するのが好ましい。
なお、上記アルミニウム合金は、選択的添加元素としてMg:2.0%以下、Cu:1.5%以下、Zn:6.0%以下、Ti:0.3%以下、V:0.3%以下、Zr:0.3%以下、Cr:0.3%以下及びNi:2.0%以下から選択される1種又は2種以上を更に含有してもよい。
Mgは、接合加熱後においてMg2Siによる時効硬化が生じ、この時効硬化によって強度向上が図られる。このように、Mgは強度向上の効果を発揮する添加元素である。Mg添加量が、2.0%を超えるとフラックスと反応して、高融点の化合物を形成し、結果としてフラックスが酸化皮膜に作用できなくなるため、接合が著しく困難となる。従って、Mgの添加量は2.0%以下とする。好ましいMgの添加量は、0.05%~2.0%である。さらに好ましくは0.1%~1.5%である。
Cuは、マトリクス中に固溶して強度向上させる添加元素である。但し、Cu添加量が1.5%を超えると耐食性が低下する。従って、Cuの添加量は1.5%以下とするのが好ましい。より好ましいCuの添加量は0.05%~1.5%である。
Znの添加は、犠牲防食作用による耐食性向上に有効である。Znはマトリクス中にほぼ均一に固溶しているが、液相が生じるとその中に溶け出して液相のZnが濃化する。液相が表面に染み出すと、その部分はZn濃度が上昇するため、犠牲陽極作用によって耐食性が向上する。また、本発明のアルミニウム合金材を熱交換器に応用する場合、本発明のアルミニウム合金材をフィンに使うことで、チューブ等を防食する犠牲防食作用を働かせることもできる。添加量が6.0%を超えると腐食速度が速くなり自己耐食性が低下する。従って、Znは6.0%以下とするのが好ましい。より好ましいZn添加量は、0.05%~6.0%である。
Ti及びVは、マトリクス中に固溶して強度向上させる他に、層状に分布して板厚方向の腐食の進展を防ぐ効果がある。いずれも0.3%を超えると粗大晶出物が発生し、成形性、耐食性を阻害する。従って、Ti及びVの含有量はそれぞれ0.3%以下とするのが好ましく、0.05%~0.3%とするのがより好ましい。
ZrはAl-Zr系の金属間化合物として析出し、分散強化によって接合後の強度を向上させる効果を発揮する。また、Al-Zr系の金属間化合物は加熱中の結晶粒粗大化に作用する。0.3%を超えると粗大な金属間化合物を形成し易くなり、塑性加工性を低下させる。よって、Zrの添加量は0.3%以下とするのが好ましく、0.05%~0.3%とするのがより好ましい。
Crは、固溶強化により強度を向上させ、またAl-Cr系の金属間化合物の析出により、加熱後の結晶粒粗大化に作用する。0.3%を超えると粗大な金属間化合物を形成し易くなり、塑性加工性を低下させる。よって、Crの添加量は0.3%以下とするのが好ましく、0.05%~0.3%とするのがより好ましい。
Niは、金属間化合物として晶出又は析出し、分散強化によって接合後の強度を向上させる効果を発揮する。Niの含有量は、2.0%以下の範囲とするのが好ましく、0.05%~2.0%の範囲とするのがより好ましい。Niの含有量が2.0%を超えると、粗大な金属間化合物を形成し易くなり、加工性を低下させ自己耐食性も低下する。
Sn、Inは、犠牲陽極作用を発揮する効果がある。添加量が0.3%を超えると腐食速度が速くなり自己耐食性が低下する。従って、これら元素のそれぞれの添加量は、0.3%以下とするのが好ましい。より好ましい添加量は0.05%~0.3%である。
本発明に係る熱交換器用フィン材は、素板の引張強さをT、450℃で2時間加熱した後の引張強さをToとした場合、T/To≦1.40の関係を満たすものとする。450℃で2時間加熱することにより、本発明に係る熱交換器用フィン材は十分に焼き鈍され、O材となる。T/ToはO材からの強度上昇割合を表している。本合金材の場合、接合加熱後の結晶粒径を大きくするために、製造工程における焼鈍後の最終の冷間圧延加工量を小さくすることが有効である。最終の加工量が大きいと、再結晶の駆動力が大きくなり、接合加熱時の結晶粒が微細化する。最終の加工量を大きくすればするほど強度は上昇するので、T/Toは大きな値となる。接合加熱後の結晶粒径を大きくして変形を防ぐためには、最終の加工量を表す指標となるT/Toを1.40以下とすることが有効である。
7-5-1.鋳造工程
上記第1の形態のフィン材に用いるアルミニウム合金材の製造方法について説明する。このアルミニウム合金材は、DC(Direct Chill)鋳造法を用いて鋳造され、鋳造時のスラブの鋳造速度を下記のように制御する。鋳造速度は、冷却速度に影響を及ぼすので、20~100mm/分とする。鋳造速度が20mm/分未満の場合は、十分な冷却速度が得られず、Si系金属間化合物やAl-Fe-Mn-Si系金属間化合物といった晶出する金属間化合物が粗大化する。一方、100mm/分を超える場合は、鋳造時にアルミニウム材が十分に凝固せず、正常な鋳塊が得られない。好ましくは、30~80mm/分である。そして、本発明が特徴とする金属組織を得るために、鋳造速度は製造する合金材の組成に応じて調整することができる。冷却速度は厚みや幅といったスラブの断面形状によるが、上記20~100mm/分の鋳造速度とすることで、鋳塊中央部で0.1~2℃/秒の冷却速度とすることができる。
加熱工程に続いて、スラブは熱間圧延工程にかけられる。熱間圧延工程は、熱間疎圧延段階と熱間仕上圧延段階を含む。ここで、熱間粗圧延段階における総圧下率を92~97%とし、かつ、熱間粗圧延の各パス中において圧下率が15%以上となるパスが3回以上含まれるものとする。
熱間圧延工程終了後は、熱間圧延材を冷間圧延工程にかける。冷間圧延工程の条件は、特に限定されるものではない。冷間圧延工程の途中において、冷間圧延材を十分に焼き鈍して再結晶組織とする焼鈍工程が設けられる。焼鈍工程後は、圧延材を最終冷間圧延にかけて最終板厚とする。最終冷間圧延段階での加工率{(加工前の板厚-加工後の板厚)/加工前の板厚}×100(%)が大き過ぎると、接合加熱中の再結晶の駆動力が大きくなり結晶粒が小さくなることで、接合加熱中の変形が大きくなる。よって、前述のとおり、T/Toが1.40以下となるように最終冷間圧延段階における加工量が設定される。最終冷間圧延段階における加工率は、10~30%程度とするのが好ましい。
本発明の熱交換器は、接合する前の材料であるフィン材に単層で接合機能を有する材料を用いて製造することにより得られるが、第1の形態に係るフィン材に代えて以下に示す単層で接合機能を有する材料を用いて製造することによっても得られる。具体的には、フィン材として、Si:1.0~5.0%、Fe:0.01~2.0%を含有し、残部Al及びMnを含む不可避的不純物からなるアルミニウム合金材であって、0.5~5μmの円相当径を有するSi系金属間化合物が、前記アルミニウム合金材断面において250~7×105個/mm2存在し、0.5~5μmの円相当径を有するAl-Fe-Mn-Si系の分散粒子が、前記アルミニウム合金材断面において100~7×105個/mm2存在することを特徴とするアルミニウム合金材である。以下、このアルミニウム合金の特徴について詳細に説明する。
Si濃度について、SiはAl-Si系の液相を生成し、接合に寄与する元素である。但し、Si濃度が1.0%未満の場合は充分な量の液相を生成することができず、液相の染み出しが少なくなり、接合が不完全となる。一方、5.0%を超えるとアルミニウム合金材中の液相の生成量が多くなるため、加熱中の材料強度が極端に低下し、構造体の形状維持が困難となる。従って、Si濃度を1.0%~5.0%と規定する。このSi濃度は、好ましくは1.5%~3.5%であり、より好ましくは2.0%~3.0%である。尚、染み出す液相の量は板厚が厚く、加熱温度が高いほど多くなるので、加熱時に必要とする液相の量は、製造する構造体の構造に応じて必要となるSi量や接合加熱温度を調整することが望ましい。
次に、本発明に係るアルミニウム合金材の金属組織における特徴について説明する。本発明に係るアルミニウム合金材は、0.5~5μmの円相当径を有するSi系金属間化合物が、その断面において250~7×105個/mm2存在することを特徴とする。ここで、Si系金属間化合物とは、(1)単体Si、及び(2)単体Siの一部にCaやPなどの元素を含むものであり、上述の液相発生のプロセスで説明した液相生成に寄与する金属間化合物である。尚、断面とは、アルミニウム合金材の任意の断面であり、例えば厚さ方向に沿った断面でもよく、板材表面と平行な断面でもよい。材料評価の簡便性の観点から、厚さ方向に沿った断面を採用するのが好ましい。
Mnは、SiとともにAl-Mn-Si系の金属間化合物を形成し、分散強化として作用し、或いは、アルミニウム母相中に固溶して固溶強化により強度を向上させる重要な添加元素である。Mn添加量が2.0%を超えると、粗大金属間化合物が形成され易くなり耐食性を低下させる。従って、Mn添加量は2.0%以下とする。好ましいMn添加量は、0.05%~2.0%である。なお、本発明においては、Mnのみならず他の合金成分においても、所定添加量以下という場合は0%も含むものとする。
上記第2の形態のフィン材に用いるアルミニウム合金材の製造方法について説明する。このアルミニウム合金材は、連続鋳造法、DC(Direct Chill)鋳造法又は押出法を用いて製造することができる。連続鋳造法としては、双ロール式連続鋳造圧延法や双ベルト式連続鋳造法等の連続的に板材を鋳造する方法であれば特に限定されるものではない。双ロール式連続鋳造圧延法とは、耐火物製の給湯ノズルから一対の水冷ロール間にアルミニウム溶湯を供給し、薄板を連続的に鋳造圧延する方法であり、ハンター法や3C法等が知られている。また、双ベルト式連続鋳造法は、上下に対峙し水冷されている回転ベルト間に溶湯を注湯してベルト面からの冷却で溶湯を凝固させてスラブとし、ベルトの反注湯側より該スラブを連続して引き出してコイル状に巻き取る連続鋳造方法である。
本発明の熱交換器は、接合する前の材料であるフィン材に単層で接合機能を有する材料を用いて製造することにより得られるが、第1、2の形態に係るフィン材に代えて以下に示す単層で接合機能を有する材料を用いて製造することによっても得られる。具体的には、必須元素としてSi濃度:1.0~5.0%及びFe:0.01~2.0%を含有し、残部Al及びMnを含む不可避的不純物からなるAl-Fe-Mn-Si系のアルミニウム合金を基本組成とし、その金属組織において、0.01~0.5μmの円相当径を有するAl系金属間化合物が10~1×104個/μm3存在し、5.0~10μmの円相当径を有するSi系金属間化合物が200個/mm2以下存在するアルミニウム合金を用いるものである。以下に、これらの特徴について説明する。
Si濃度について
Si濃度について、SiはAl-Si系の液相を生成し、接合に寄与する元素である。但し、Si濃度が1.0%未満の場合は充分な量の液相を生成することができず、液相の染み出しが少なくなり、接合が不完全となる。一方、5.0%を超えるとアルミニウム合金材中の液相の生成量が多くなるため、加熱中の材料強度が極端に低下し、構造体の形状維持が困難となる。従って、Si濃度を1.0%~5.0%と規定する。このSi濃度は、好ましくは1.5%~3.5%であり、より好ましくは2.0%~3.0%である。尚、染み出す液相の量は体積が大きく、加熱温度が高いほど多くなるので、加熱時に必要とする液相の量は、製造する構造体の構造に応じて必要となるSi量や接合加熱温度を調整することが望ましい。
Fe濃度について、Feはマトリクスに若干固溶して強度を向上させる効果を有するのに加えて、晶出物や析出物として分散して特に高温での強度低下を防止する効果を有する。Feは、その添加量が0.01%未満の場合、上記の効果が小さいだけでなく、高純度の地金を使用する必要がありコストが増加する。また、2.0%を超えると、鋳造時に粗大な金属間化合物が生成し、製造性に問題が生じる。また、本接合体が腐食環境(特に液体が流動するような腐食環境)に曝された場合には耐食性が低下する。更に、接合時の加熱によって再結晶した結晶粒が微細化して粒界密度が増加するため、接合前後で寸法変化が大きくなる。従って、Feの添加量は0.01%~2.0%とする。好ましいFeの添加量は、0.2%~1.0%である。
次に、本発明に係るアルミニウム合金材の金属組織における特徴について説明する。本発明に係るアルミニウム合金材は、MONOBRAZE法による接合加熱時に固相線温度以上に加熱される。この時、アルミニウム合金材は主に粒界すべりによって変形する。そこで、金属組織としては、(1)接合加熱時に結晶粒が粗大になることが望ましい。(2)また、粒界に液相が生成すると粒界すべりによる変形が起こり易くなるため、粒界での液相生成が抑制されることが望ましい。本発明では、加熱後の結晶粒が粗大になり、粒界での液相生成が抑制される金属組織を規定する。
本発明に係るアルミニウム合金材では、上記Al系金属間化合物に関する規定に加えて、Si系金属間化合物に関しても規定する。本発明に係るアルミニウム合金材では、5.0~10μmの円相当径を有するSi系金属間化合物が、材料中の断面において200個/mm2以下存在する。ここで、Si系金属間化合物とは、(1)単体Si、及び(2)単体Siの一部にCaやPなどの元素を含むものである。尚、材料中の断面とは、アルミニウム合金材の任意の断面であり、例えば厚さ方向に沿った断面でもよく、板材表面と平行な断面でもよい。材料評価の簡便性の観点から、厚さ方向に沿った断面を採用するのが好ましい。
また、上記アルミニウム合金材では、上記Al系金属間化合物及びSi系金属間化合物の規定に加え、Si固溶量が規定される。本発明に係るアルミニウム合金材は、MONOBRAZE法による接合前において、Si固溶量が0.7%以下であることが好ましい。なお、このSi固溶量は、20~30℃の室温における測定値である。上述のように固溶Siは加熱中に固相拡散し、周囲の液相の成長に寄与する。固溶Si量が0.7%以下であれば、固溶Siの拡散によって粒界に生成する液相量が少なくなり、加熱中の変形を抑制できる。一方、固溶Si量が0.7%を超えると、粒界に生成した液相に取り込まれるSiが増加する。その結果、粒界に生成する液相量が増加して、変形が起こり易くなる。より好ましい固溶Si量は、0.6%以下である。なお、固溶Si量の下限値は特に限定するものではないが、アルミニウム合金のSi含有量及び製造方法によって自ずと決まり、本発明では0%である。
上述のように、本発明に係る単層で加熱接合機能を有するアルミニウム合金材は、接合加熱中の耐変形性の向上のために、必須元素として所定量のSi及びFeを含有する。そして、強度を更に向上させるために、必須元素であるSi及びFeに加えて、所定量のMn、Mg及びCuから選択される1種又は2種以上が第1の選択的添加元素として更に添加される。なお、このような第1の選択的添加元素を含有する場合においても、Al系金属間化合物の体積密度及びSi系金属間化合物の面密度については、上記の通りに規定される。
本発明においては、耐食性を更に向上させるために、上記必須元素及び/又は第1の選択的添加元素に加えて、所定量のZn、In及びSnから選択される1種又は2種以上が第2の選択的添加元素として更に添加される。なお、このような第2の選択的添加元素を含有する場合においても、Al系金属間化合物の体積密度及びSi系金属間化合物の面密度については、上記の通りに規定される。
本発明においては、強度や耐食性を更に向上させるために、上記必須元素、第1の選択的添加元素及び第2の選択的添加元素の少なくともいずれかに加えて、所定量のTi、V、Cr、Ni及びZrから選択される1種又は2種以上が第3の選択的添加元素として更に添加される。なお、このような第3の選択的添加元素を含有する場合においても、Al系金属間化合物の体積密度及びSi系金属間化合物の面密度については、上記の通りに規定される。
本発明に係るアルミニウム合金材では、液相の特性改善を図ることにより接合性を更に良好にするために、上記必須元素及び第1~3の選択的添加元素の少なくともいずれかに加えて、所定量のBe、Sr、Bi、Na及びCaから選択される1種又は2種以上を第4の選択的添加元素として更に添加してもよい。なお、このような第4の選択的添加元素を含有する場合においても、Al系金属間化合物の体積密度及びSi系金属間化合物の面密度については、上記の通りに規定される。
ところで、Fe及びMnはいずれも、Siと共にAl-Fe-Mn-Si系の金属間化合物を形成する。Al-Fe-Mn-Si系金属間化合物を生成するSiは液相の生成への寄与が小さいため、接合性が低下することになる。そのため、本発明に係るアルミニウム合金材でFe及びMnを添加する場合には、Si、Fe、Mnの含有量について留意することが好ましい。具体的には、Si、Fe、Mnの含有量(mass%)をそれぞれS、F、Mとしたとき、1.2≦S-0.3(F+M)≦3.5の関係式を満たすことが好ましい。S-0.3(F+M)が1.2未満の場合は、接合が不十分となる。一方、S-0.3(F+M)が3.5より大きい場合は、接合前後で形状が変化し易くなる。
また、上記アルミニウム合金材は、MONOBRAZE法による接合前の引張強さが80~250MPaであるものが好ましい。この引張強さが80MPa未満であると、製品の形状に成形するために必要な強度が足りず、成形することができない。この引張強さが250MPaを超えると、成形した後の形状保持性が悪く、接合体として組み立てたときに他の部材との間に隙間ができて接合性が悪化する。なお、MONOBRAZE法による接合前の引張強さは、20~30℃の室温での測定値をいう。また、MONOBRAZE法による接合前の引張強さ(T0)と接合後の引張強さ(T)の比(T/T0)が、0.6~1.1の範囲であることが好ましい。(T/T0)が0.6未満の場合には、材料の強度が不足し、構造体としての機能が損なわれる場合があり、1.1を超えると粒界での析出が過剰となり粒界腐食が起こりやすくなる場合がある。
9-11-1.鋳造工程
上記第3の形態のフィン材に用いるアルミニウム合金材の製造方法について説明する。このアルミニウム合金材は、連続鋳造法を用いて製造される。連続鋳造法では、凝固時の冷却速度が速いため、粗大な晶出物が形成され難く、円相当径5.0μm~10μmのSi系金属間化合物の形成が抑制される。その結果、再結晶核の数が少なくできるため特定の結晶粒のみが成長し、粗大な結晶粒が得られる。また、Mn、Feなどの固溶量が大きくなるため、その後の加工工程で円相当径0.01μm~0.5μmのAl-Fe-Mn-Si系金属間化合物の形成が促進される。このように、適切な強さのピン止め効果と、粒内の固溶Siを集める効果が得られる円相当径0.01μm~0.5のAl-Fe-Mn-Si系金属間化合物が形成されることにより、限られた結晶粒のみが成長し、粗大な結晶粒が得られ、かつ粒界での液相生成が抑制され、耐変形性が向上する。
上述の双ロール式連続鋳造圧延法とその後の製造工程により、半連続鋳造に比べて分散粒子を微細にすることが可能である。しかしながら、本発明に係るアルミニウム合金材の金属組織を得るためには、凝固時の冷却速度をより精密に制御することが重要となる。本発明者らは、上記冷却速度の制御が、アルミコーティング厚みの制御及び圧延荷重による溶湯内サンプ制御によって可能であることを見出した。
アルミコーティングとは、アルミニウム及び酸化アルミニウムを主成分とする皮膜である。鋳造中にロール表面に形成されるアルミコーティングは、ロール表面と溶湯の濡れを良くし、ロール表面と溶湯間の熱伝達を向上させる。アルミコーティングを形成するためには、680~740℃のアルミニウム溶湯を500N/mm以上の圧延荷重にて双ロール式連続鋳造圧延を実施してもよく、或いは、双ロール式連続鋳造圧延開始前に300℃以上に加熱した展伸材用アルミニウム合金板を圧下率20%以上で2回以上圧延させてもよい。アルミコーティング形成に使用するアルミニウム溶湯又はアルミニウム合金板は、添加元素の少ない1000系合金が特に好ましいが、その他のアルミニウム合金系を用いてもコーティング形成は可能である。鋳造中、アルミコーティング厚みは常に増加するため、窒化ホウ素、または炭素系離型剤(グラファイトスプレー、もしくは煤)をロール表面に10μg/cm2で塗布し、アルミコーティングの更なる形成を抑制する。また、ブラシロール等で物理的に除去することも可能である。
連続鋳造板の金属間化合物密度については、本来凝固時の冷却速度を制御して操作することが望ましい。但し、鋳造中の冷却速度測定は非常に困難であり、オンラインで計測できるパラメータにて金属間化合物密度を制御することが必要とされる。
双ロール式連続鋳造圧延法においては、鋳造中に鋳塊がロールを押し上げる力と、鋳造前から鋳造中まで上下ロール間にかかる一定の力が発生する。これら2つの力の和は、ロール中心線に平行な成分として、油圧式シリンダにて計測することが可能である。したがって、圧延荷重は、鋳造開始前と鋳造中におけるシリンダ圧の増加分を力に変換し、鋳造板の幅で割ることで求められる。例えば、シリンダ数が2個、シリンダ径が600mm、1つのシリンダ圧の増加が4MPa、鋳造中の圧延板の幅が1500mmであった場合、板状鋳塊の単位幅あたりの圧延荷重は、下記式から1508N/mmとなる。
4×3002×π÷1500×2=1508N/mm
また、本発明の熱交換器の製造に用いる材料としてフィン材以外の部材については、特に規定しないが以下のような形態であるのが好ましい。
本発明に係る熱交換器は、上記各部材を熱交換器の形状に組んだ後、フラックス塗布などの処理を施し、炉で加熱接合を行い製造される。
フィン、チューブ及びヘッダを下記材料を用いて形成し、これらを図5に示すような熱交換器の形状に組み付けた後、全体を接合加熱し、熱交換器を製造した。
表1の合金組成の試験材を用いた。表1において、合金組成の「-」は検出限界以下であることを示すものであり、「残部」は不可避的不純物を含む。上記試験材を用いて、鋳造鋳塊を製造した。F1、F3については、DC鋳造法で厚さ400mm、幅1000mm、長さ3000mmのサイズで鋳造した。鋳造速度は40mm/分とした。鋳塊を面削して厚さを380mmとした後、熱間圧延前の加熱保持工程として鋳塊を500℃まで加熱してその温度で5時間保持し、次いで熱間圧延工程にかけた。熱間圧延工程の熱間粗圧延段階では、総圧下率を93%としこの段階で厚さ27mmまで圧延した。更に、熱間粗圧延段階において、15%以上の圧下率となるパスを5回とした。熱間粗圧延段階後に、圧延材を更に熱間仕上圧延段階にかけて3mm厚まで圧延した。その後の冷間圧延工程において、圧延板を0.09mm厚まで圧延した。更に、圧延材を380℃で2時間の中間焼鈍工程にかけ、最後に最終冷間圧延段階にて最終板厚0.07mmまで圧延して供試材とした。
フィン、チューブ及びヘッダを下記材料を用いて形成し、第1実施例と同様に熱交換器の形状に組み付けた後、全体を接合加熱し、熱交換器を製造した。
フィン、チューブ及びヘッダを下記材料を用いて形成し、第1実施例と同様に熱交換器の形状に組み付けた後、全体を接合加熱し、熱交換器を製造した。この第3実施例では、主要添加元素の影響を検討した。
まず、表8に示す合金組成の鋳造鋳塊を製造した。表8において、合金組成の「-」は検出限界以下であることを示すものであり、「残部」は不可避的不純物を含む。F31、F33~F43については、DC鋳造法で厚さ400mm、幅1000mm、長さ3000mmのサイズで鋳造した。鋳造速度は40mm/分とした。鋳塊を面削して厚さを380mmとした後、熱間圧延前の加熱保持工程として鋳塊を500℃まで加熱してその温度で5時間保持し、次いで熱間圧延工程にかけた。熱間圧延工程の熱間粗圧延段階では、総圧下率を93%としこの段階で厚さ27mmまで圧延した。更に、熱間粗圧延段階において、15%以上の圧下率となるパスを5回とした。熱間粗圧延段階後に、圧延材を更に熱間仕上圧延段階にかけて3mm厚まで圧延した。その後の冷間圧延工程において、圧延板を0.145mm厚まで圧延した。更に、圧延材を380℃で2時間の中間焼鈍工程にかけ、最後に最終冷間圧延段階にて最終板厚0.115mmまで圧延して供試材とした。
2・・・領域
2A・・・ロール
2B・・・ロール
3・・・ロール中心線3
4・・・ノズルチップ
5・・・圧延領域
6・・・非圧延領域
7・・・凝固開始点
8・・・圧延荷重
9・・・メニスカス部
n・・・結晶粒数
t・・・板厚
T・・・L-ST断面におけるAlマトリクスの板厚方向の結晶粒の平均長さ
Claims (12)
- 作動流体が流通するアルミニウム材のチューブと、当該チューブに金属的に接合されたアルミニウム材のフィンとを含む熱交換器であって、前記フィンが、0.1~2.5μmの円相当径を有するAl-Fe-Mn-Si系金属間化合物が5.0×104個/mm2未満存在する領域Bを結晶粒界の周囲に有し、かつ、当該領域Bの周囲に、0.1~2.5μmの円相当径を有するAl-Fe-Mn-Si系金属間化合物が5.0×104~1.0×107個/mm2存在する領域Aを有することを特徴とする熱交換器。
- 結晶粒界の長さ当たりにおける前記領域Bの平均面積をsμmとして、2<s<40を満たす、請求項1に記載の熱交換器。
- 前記フィンの表面における前記領域Aの面積占有率が60%以上である、請求項1又は2に記載の熱交換器。
- 接合部フィレット以外の前記チューブ表面にAl-Si共晶組織が存在しない、請求項1~3のいずれか一項に記載のアルミニウム合金熱交換器。
- 前記フィンのL-LT断面でのAlマトリクスの結晶粒径をLμmとし、前記フィンのL-ST断面でのAlマトリクスの結晶粒径をTμmとして、L≧100、かつ、L/T≧2である、請求項1~4のいずれか一項に記載のアルミニウム合金熱交換器。
- 前記フィンの自然電位が-910mV以上であり、当該フィンの自然電位が、前記フィンとチューブの接合部のフィレットの自然電位より0~200mV貴である、請求項1~5のいずれか一項に記載のアルミニウム合金熱交換器。
- 請求項1~6のいずれか一項に記載の熱交換器に用いるフィン材であって、Si:1.0~5.0mass%、Fe:0.1~2.0mass%、Mn:0.1~2.0mass%を含有し、残部Al及び不可避的不純物からなるアルミニウム合金からなり、0.5~5μmの円相当径を有するSi系金属間化合物が250~7×104個/mm2存在し、5μmを超える円相当径を有するAl-Fe-Mn-Si系金属間化合物が10~1000個/mm2存在することを特徴とする単層で加熱接合機能を有する熱交換器用フィン材。
- 前記アルミニウム合金が、Mg:2.0mass%以下、Cu:1.5mass%以下、Zn:6.0mass%以下、Ti:0.3mass%以下、V:0.3mass%以下、Zr:0.3mass%以下、Cr:0.3mass%以下及びNi:2.0mass%以下から選択される1種又は2種以上を更に含有する、請求項7に記載の熱交換器用フィン材。
- 請求項1~6のいずれか一項に記載の熱交換器に用いるフィン材であって、Si:1.0~5.0mass%、Fe:0.01~2.0mass%を含有し、残部Al及びMnを含む不可避的不純物からなるアルミニウム合金からなり、0.5~5μmの円相当径を有するSi系金属間化合物が250~7×105個/mm2存在し、0.5~5μmの円相当径を有するAl-Fe-Mn-Si系金属間化合物が100~7×105個/mm2存在することを特徴とする単層で加熱接合機能を有する熱交換器用フィン材。
- 前記アルミニウム合金が、Mn:2.0mass%以下、Mg:2.0mass%以下、Cu:1.5mass%以下、Zn:6.0mass%以下、Ti:0.3mass%以下、V:0.3mass%以下、Zr:0.3mass%以下、Cr:0.3mass%以下及びNi:2.0mass%以下から選択される1種又は2種以上を更に含有する、請求項9に記載の熱交換器用フィン材。
- 請求項1~6のいずれか一項に記載の熱交換器に用いるフィン材であって、Si:1.0~5.0mass%、Fe:0.01~2.0mass%を含有し、残部Al及びMnを含む不可避的不純物からなるアルミニウム合金からなり、5.0~10μmの円相当径を有するSi系金属間化合物が200個/mm2以下存在し、0.01~0.5μmの円相当径を有するAl-Fe-Mn-Si系金属間化合物が10~1×104個/μm3存在することを特徴とする単層で加熱接合機能を有する熱交換器用フィン材。
- 前記アルミニウム合金が、Mn:0.05~2.0mass%、Mg:0.05~2.0mass%、Cu:0.05~1.5mass%、Zn:6.0mass%以下、Ti:0.3mass%以下、V:0.3mass%以下、Zr:0.3mass%以下、Cr:0.3mass%以下及びNi:2.0mass%以下から選択される1種又は2種以上を更に含有する、請求項10に記載の熱交換器用フィン材。
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JP2018090840A (ja) * | 2016-11-30 | 2018-06-14 | 株式会社Uacj | 熱交換器用アルミニウム合金フィン材、当該熱交換器用アルミニウム合金フィン材を用いた熱交換器用アルミニウム合金フィン材コイル、当該熱交換器用アルミニウム合金フィン材又は熱交換器用アルミニウム合金フィン材コイルを用いて製造されるコルゲートフィン材、ならびに、これらコルゲートフィン材を用いて製造される熱交換器 |
WO2022176420A1 (ja) * | 2021-02-16 | 2022-08-25 | 株式会社Uacj | アルミニウム合金板、その製造方法及び熱交換器 |
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WO2023243630A1 (ja) * | 2022-06-17 | 2023-12-21 | 株式会社Uacj | ろう付用単層アルミニウム合金材、その製造方法、アルミニウム構造体及び熱交換器 |
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EP3006888A4 (en) | 2016-09-28 |
JPWO2014196183A1 (ja) | 2017-02-23 |
US20160116234A1 (en) | 2016-04-28 |
JP5698416B1 (ja) | 2015-04-08 |
BR112015030144A2 (pt) | 2017-07-25 |
CN105264327A (zh) | 2016-01-20 |
EP3006888B1 (en) | 2020-08-05 |
MX2015016401A (es) | 2016-04-13 |
CN105264327B (zh) | 2017-07-04 |
MY177830A (en) | 2020-09-23 |
US10408550B2 (en) | 2019-09-10 |
KR102212299B1 (ko) | 2021-02-03 |
EP3006888A1 (en) | 2016-04-13 |
KR20160015229A (ko) | 2016-02-12 |
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