CN116555632A

CN116555632A - Method for manufacturing aluminum alloy composite material for heat exchanger

Info

Publication number: CN116555632A
Application number: CN202210112268.9A
Authority: CN
Inventors: 绀谷亚耶
Original assignee: UACJ Corp
Current assignee: UACJ Corp
Priority date: 2022-01-29
Filing date: 2022-01-29
Publication date: 2023-08-08

Abstract

The method for manufacturing the aluminum alloy composite material for the heat exchanger comprises the following steps: forming a first material as a raw material of the core material by at least melting, casting, and surface cutting; forming a second material as a raw material of the sacrificial anticorrosive material by performing at least melting, casting, hot rolling, and cutting; and integrating the overlapped material obtained by laminating the first material and the second material in the thickness direction by at least hot cladding, wherein before the cladding, the overlapped material is heated at 460-500 ℃ for more than 2 hours, the temperature of the overlapped material at the beginning of the cladding is 420 ℃ or more, the temperature of the rolled material at the end of the cladding is 190-350 ℃, the thickness of the rolled material at the end of the cladding is 6mm or less, the annealing temperature is 350 ℃ or more, and the annealing time is3 hours or more.

Description

Method for manufacturing aluminum alloy composite material for heat exchanger

Technical Field

The present invention relates to a method for producing an aluminum alloy composite material for a heat exchanger suitable for an automotive heat exchanger.

Background

For example, as shown in fig. 1, a radiator of a heat exchanger for an automobile is manufactured by: the tube 1 through which the refrigerant flows, the corrugated fin 2, and a Header plate (Header plate) 3 are attached, and the attached body is brazed at a temperature of about 600 ℃. The radiator is provided with a tank 4 for collecting and dispensing the refrigerant.

Further, an aluminum alloy composite material for heat exchangers, in which a sacrificial anode material (Al-Zn alloy: JIS7072 alloy, etc.) is coated (Clad) on one surface of a core material (Al-Mn alloy: JIS3003 alloy, etc.) is used for the tube 1. When the tube does not have a Brazing filler metal, a Brazing sheet (Brazing sheet) fin in which a core material of pure Al, an al—mn alloy (JIS 3003 alloy, etc.) or the like is made and a Brazing filler metal (al—si alloy: JIS4045 alloy, etc.) is coated is used as the fin 2. The header plate 3 is made of a Clad (Clad) material in which a brazing filler metal (al—si alloy: JIS4045 alloy, etc.) is coated on one surface (atmosphere side) of a core material (al—mn alloy: JIS3003 alloy, etc.), and a sacrificial anode material (al—zn alloy: JIS7072 alloy, etc.) is coated on the other surface (refrigerant side).

In recent years, in order to reduce the weight of heat exchangers, it has been demanded to reduce the thickness of components. In such a thinned member, it is also necessary to ensure a certain strength, solderability, and corrosion resistance. Therefore, aluminum alloy composite materials for heat exchangers and the like have been proposed, which contain Cu in the core material or increase the Mn content of the core material. In this way, in addition to controlling the chemical composition of the alloy constituting the aluminum alloy composite material for heat exchangers, optimization of the manufacturing process has been proposed.

For example, by finely mixing intermetallic compounds in a material and blending a distribution state of the intermetallic compounds, conditions of cold rolling and annealing are strictly controlled, and thereby a uniform aluminum alloy composite material for heat exchangers is manufactured. This suppresses the variation in the overall plate thickness and the thickness of the sacrificial anode material, and prevents the local anticorrosive effect from becoming weak, thereby failing to achieve the target corrosion resistance.

Disclosure of Invention

Problems to be solved by the invention

However, there are the following problems: in the case of manufacturing an aluminum alloy composite material for heat exchangers using a large ingot industrially, the characteristics of the object cannot be satisfied.

The present invention has been made in view of the above-described problems, and an object thereof is to provide a technique capable of manufacturing an aluminum alloy composite material for heat exchangers excellent in characteristics using a large ingot.

Solution for solving the problem

The method for producing an aluminum alloy material according to the present invention is a method for producing an aluminum alloy composite material for a heat exchanger, the aluminum alloy composite material comprising: a core material formed of an aluminum alloy containing 0.9 mass% or less of Si, 0.75 mass% or less of Fe, 0.7 mass% or less of Cu, and 0.6 to 1.9 mass% of Mn, wherein the aluminum alloy contains one or more of 0.3 mass% or less of Mg, 0.3 mass% or less of Cr, 0.3 mass% or less of Zr, and 0.3 mass% or less of Ti; and a sacrificial anticorrosive material formed from an aluminum alloy containing 0.8 to 4.5 mass% of Zn.

The method for manufacturing the aluminum alloy material comprises the following steps: forming a first material as a raw material of the core material by at least melting, casting, and surface cutting; forming a second material as a raw material of the sacrificial anticorrosive material by performing at least melting, casting, hot rolling, and cutting; and integrating a stacked material obtained by stacking the first material and the second material in the thickness direction by at least hot cladding rolling, thereby forming a rolled material; a step of cold-rolling the rolled material; and annealing the rolled material after the cold rolling, wherein the overlapped material is heated at 460 to 500 ℃ for 2 hours or more before the clad rolling, the temperature of the overlapped material at the beginning of the clad rolling is 420 ℃ or more, the temperature of the rolled material at the end of the clad rolling is 190 to 350 ℃, the thickness of the rolled material at the end of the clad rolling is 6mm or less, the annealing temperature is 350 ℃ or more, and the annealing time is3 hours or more.

Effects of the invention

As described above, according to the present invention, an aluminum alloy composite material for heat exchangers excellent in characteristics can be produced using a large ingot.

Drawings

Fig. 1 is a schematic view of a heat exchanger for a radiator.

Fig. 2 is a flowchart showing a process for producing an aluminum alloy composite material for heat exchangers.

Fig. 3 is a schematic view showing the structure of an aluminum alloy composite material for heat exchangers according to an embodiment.

Detailed Description

1. Integral construction of aluminum alloy composite material for heat exchanger

The aluminum alloy composite material for heat exchangers manufactured by the manufacturing method according to one embodiment of the present invention has at least a core material and a sacrificial corrosion-preventing material. For example, an aluminum alloy composite material for heat exchangers is used for a plate material or the like, and the corrosion resistance is improved by disposing a sacrificial corrosion inhibitor on the outside air side of an evaporator to which moisture adheres or on the cooling water side of an inverter. The thickness of the aluminum alloy composite material for heat exchangers produced by the production method according to one embodiment of the present invention is300 to 600 μm, and is set to O-material quality control.

The proportion (cladding ratio) of the thickness of the sacrificial corrosion inhibitor in the entire plate thickness of the aluminum alloy composite material for heat exchangers produced by the production method according to one embodiment of the present invention is 5 to 25%. By adjusting the cladding ratio of the sacrificial corrosion inhibitor within the above range, corrosion resistance suitable for the constitution of the heat exchanger made of the aluminum alloy composite material for heat exchanger can be ensured.

When a defective portion that does not satisfy the target characteristics occurs in the production of the aluminum alloy composite material for heat exchangers, the manufacturability is deteriorated and the product rate is lowered. Even if the aluminum alloy composite material for heat exchangers is not defective in production, if the variation in the properties of the aluminum alloy composite material is large, the corrosion resistance, formability, etc. of the heat exchanger product may be adversely affected.

2. Chemical composition

2.1. Chemical composition of core material

The Si of the core material has an effect of forming fine intermetallic compounds of al—mn—si system and improving strength. The intermetallic compound can control recrystallization behavior during brazing heating, and can improve the corrosion resistance (Erosion) of the material. When the content of Si exceeds 0.9 mass%, the melting point of the alloy is lowered, and melting corrosion of the brazing filler metal during brazing heating becomes remarkable. Therefore, the content of Si is set to 0.9 mass% or less.

Industrially, fe of the core material is an inevitable element contained in the aluminum alloy. The Fe of the core material forms a crystal having a higher potential than the aluminum base material, and the crystal functions as a cathode side. When the amount of the crystal acting as the cathode side increases, the corrosion resistance deteriorates. Therefore, the content of Fe is 0.75 mass% or less.

The Cu of the core material improves the strength of the aluminum alloy composite material for heat exchangers. When the Cu content of the core material exceeds 0.9 mass%, the melting point is lowered, and melting occurs during brazing. Since Cu has a large solid solution limit and is present in the core material in a solid solution, cu is an element that has little influence on the effect of the present invention, i.e., the "reduction of characteristic variation of aluminum alloy composite material for heat exchanger". When the Cu content of the core material increases, the grain boundary corrosion sensitivity increases and the corrosion resistance deteriorates, so the Cu content of the core material is set to 0.7 mass% or less.

Mn of the core material increases strength by dispersion strengthening by forming fine intermetallic compounds in the core material. Mn is an element that coarsens recrystallized grains during brazing and improves brazability. Although fine intermetallic compounds precipitate in the homogenization after casting and cladding rolling steps, when there is a deviation in the distribution, mechanical properties are not uniform. As a result, the overall plate thickness and the skin thickness of the aluminum alloy composite material for heat exchangers vary. By setting the Mn content to 0.6 to 1.9 mass%, the distribution variation of the fine intermetallic compound can be reduced.

The above-described element is a main element contained in the core material, and one or two or more of Mg of 0.3 mass% or less, cr of 0.3 mass% or less, zr of 0.3 mass% or less, and Ti of 0.3 mass% or less may be contained in the core material.

Mg of the core material is an element whose strength is greatly improved by a small amount of addition. When soldering is performed by CAB (controlled atmosphere soldering) method using Flux (Flux), mg reacts with Flux during soldering heating, and the effect of Flux is hindered, so that the solderability is lowered. Therefore, the upper limit of the Mg content is set to 0.3 mass%. The smaller the Mg content, the lower the strength improving effect, but the reaction with the flux is reduced and the solderability is improved.

Cr and Zr in the core material are contained for improving strength and controlling the size of recrystallization generated during brazing. The upper limit of the content of Cr and Zr is 0.3 mass%. This is because, when the content of Cr and Zr exceeds 0.3 mass%, coarse intermetallic compounds are generated, and formability is lowered.

The Ti of the core material may be contained as a main element of a grain refiner at the time of casting. In order to improve corrosion resistance, ti may be contained. When the Ti content exceeds 0.3 mass%, coarse intermetallic compounds are generated, and formability is lowered.

The content of the elements other than the above in the core material is set to 0.05 mass% or less and 0.2 mass% or less in total.

2.2. Chemical composition of sacrificial corrosion protection material

The sacrificial anticorrosive material contains 0.8 to 4.5 mass% Zn. This makes it possible to lower the potential of the sacrificial anticorrosive material and impart a sacrificial anticorrosive effect. Since the core material contains 0.7 mass% or less of Cu, cu diffuses from the core material to the sacrificial corrosion-resistant material during brazing. Since the potential of the sacrificial corrosion inhibitor increases due to Cu diffused from the core material, the sacrificial corrosion inhibitor cannot sufficiently exhibit the sacrificial corrosion inhibitor effect when the Zn content in the sacrificial corrosion inhibitor is 0.8 mass% or less. On the other hand, when the Zn content in the sacrificial corrosion inhibitor exceeds 4.5 mass%, the corrosion rate becomes too high, the self corrosion resistance of the sacrificial corrosion inhibitor decreases, and the corrosion resistance of the entire aluminum alloy composite material for heat exchangers decreases.

The sacrificial anticorrosive material may contain 12 mass% or less of Si, 1 mass% or less of Fe, and 1 mass% or less of Mn.

Industrially, si is an inevitable element contained in aluminum alloys. Si may be actively added to the sacrificial anticorrosive material to lower the melting point, thereby allowing the sacrificial anticorrosive material to function as a solder. When the sacrificial anticorrosive material is used as a brazing filler metal, the Si content is 12 mass% or less of the eutectic point composition.

Fe is an inevitable element contained in aluminum alloys in industry. Further, by adding a trace amount of Fe to the sacrificial corrosion inhibitor, the strength of the sacrificial corrosion inhibitor can be increased. The content of Fe in the sacrificial anticorrosive material is set to 1 mass% or less. The self-corrosion resistance of the sacrificial corrosion inhibitor whose Fe content exceeds 1 mass% is reduced, and the life of the sacrificial corrosion inhibitor as a skin material is shortened. The lower the content of Fe in the sacrificial anticorrosive material, the better the corrosion resistance, and therefore the lower limit is not set for the content of Fe in the sacrificial anticorrosive material.

In addition to the above elements, 3 mass% or less of Mg may be added to the sacrificial anticorrosive material in order to improve the strength.

2.3. Chemical composition of solder

The brazing filler metal is an aluminum alloy laminated by supplying a brazing filler metal when brazing an aluminum alloy composite for a heat exchanger in a furnace under a vacuum or a non-oxidizing atmosphere. In order to reduce the melting point of the brazing filler metal and ensure fluidity during brazing, the content of Si in the brazing filler metal is set to 5 to 12 mass%. When the Si content in the solder is less than 5 mass%, the fluidity of the solder becomes low, and sufficient solderability cannot be obtained. The content of Si in the brazing filler metal is 12 mass% or less of the eutectic point composition.

The Fe content in the brazing filler metal is 1 mass% or less. When the content of Fe in the brazing filler metal exceeds 1 mass%, the self corrosion resistance of the brazing filler metal decreases, and the life as a sheath decreases.

The content of Mg in the solder is 1.5 mass% or less. Mg is actively added to a brazing filler metal for an aluminum alloy composite material for heat exchangers used for vacuum brazing in a range of 1.5 mass% or less. However, when Mg is excessively added, a thick oxide film is formed and the brazability is reduced, so that the addition amount is set to 1.5% or less.

On the other hand, no active Mg addition was performed for the brazing filler metal of the aluminum alloy composite material for heat exchangers used for brazing in a furnace under a non-oxidizing atmosphere (CAB method). This is because the flux used in the CAB method reacts with Mg to hinder the action of the flux.

For the purpose of further improving the brazability, bi and Sr, or Bi monomers may be added to the brazing filler metal of the aluminum alloy composite material for heat exchangers used for vacuum brazing. In this case, the content of Bi in the solder is 0.2 mass% or less, and the content of Sr is 0.05 mass% or less. The Zn content in the brazing filler metal is 0.3 mass% or less. When the brazing filler metal contains more than 0.3 mass% Zn, the potential of the brazing filler metal decreases and the corrosion rate increases.

3. Method for manufacturing aluminum alloy composite material for heat exchanger

Fig. 2 shows a process of a method for producing an aluminum alloy composite material for heat exchangers according to an embodiment of the present invention. The method comprises the following steps: and a step of integrating an aluminum alloy ingot (first material) having a thickness of several hundred mm with a second material and a third material prepared by hot rolling or the like by cladding rolling. The present invention is to stabilize the quality of a product in clad rolling. In the following description, the second material and the third material are sometimes referred to as a skin material. In the following description, hot rolling performed in manufacturing the skin is described as hot rolling only, and hot rolling performed in integrating the first material and the skin is described as being distinguished from clad rolling.

3.1. Method for manufacturing leather

First, a method for manufacturing a skin material will be described. The skin material is a plate material laminated with the first material as a raw material of the core material, and is composed of a third material as a raw material of the brazing filler metal of the al—si alloy and a second material as a raw material of the sacrificial corrosion preventing material of the al—zn alloy or the like. The second material and the third material are manufactured by substantially the same method, and thus are described as common descriptions. In the method for producing an aluminum alloy composite material for a heat exchanger according to the present invention, at least the second material as a raw material of the sacrificial corrosion inhibitor may be produced as a skin material, and the third material as a raw material of the brazing filler metal is not necessarily produced.

Firstly, raw materials such as aluminum, aluminum alloy master alloy, aluminum alloy material and the like are mixed and melted to obtain an aluminum alloy melt. The melting and composition adjustment are performed in two furnaces, a melting furnace and a holding furnace. The molten aluminum alloy prepared in the melting furnace is transferred to a holding furnace, and the molten aluminum alloy is treated to finally adjust the composition. In the case of manufacturing the third material, the chemical composition of the brazing filler metal is adjusted so as to be the chemical composition of the brazing filler metal, and in the case of manufacturing the second material, the chemical composition of the sacrificial corrosion preventing material is adjusted so as to be the chemical composition of the sacrificial corrosion preventing material.

The temperature of the melt in the melting furnace is set to be in the temperature range of 700 to 850 ℃. In a melting furnace, raw materials such as aluminum and master alloy are melted to obtain an aluminum alloy melt. The obtained aluminum alloy melt is transferred to a holding furnace, and final composition adjustment and the like are performed.

In the holding furnace, the melt is kept at a temperature near 700 ℃ while dehydrogenation, removal of the material, and the like are performed by using a flux or blowing a gas such as Ar gas. The melt after these treatments was cast, but dehydrogenation treatment and melt treatment were also performed from the holding furnace to the casting machine. The dehydrogenation treatment can be performed by blowing Ar gas so as to disperse as bubbles. In the melt processing, the inclusions in the melt are removed by passing the melt through a ceramic filter.

In addition, al alloy wires containing Ti and B are generally added at a constant rate as a refiner between the holding furnace and the casting machine for miniaturization of the ingot structure. The casting of the skin is performed by DC casting (Direct Chill Casting: direct chill casting). The casting speed of the skin is typically 40-60 mm/min. The casting temperature of the third material as the raw material of the brazing filler metal is 630 to 700 ℃. The casting temperature of the second material as a raw material of the sacrificial anticorrosive material is 680 to 720 ℃.

In order to remove entanglement of oxide on the surface of the ingot of the skin formed by the above casting, the ingot was subjected to surface cutting. The surface cutting amount is set according to the surface state of the ingot as long as it is 3mm or more. The cutting of the beginning and/or ending portion of the casting is sometimes performed before the surface cutting. This is because the structure formed by casting is not stable at the beginning and/or end. The length of the cut is usually about 100 to 200 mm. In some cases, the header and/or the tail are cut in the hot rolling step without cutting at the stage of the ingot.

The slab ingot was heated by hot rolling, but the temperature was around 480 ℃. The heating to high temperature causes energy waste and also causes oxide film growth on the surface of the ingot. The heating time of the ingot is usually 2 hours or more.

The hot rolling of the skin material can be performed by a conventional method, and cutting is performed after rolling to obtain a skin material having a predetermined plate thickness. The predetermined plate thickness is a plate thickness determined based on the thickness of the ingot of the core material after the surface cutting and the cladding ratio of the skin material (the ratio of the thickness of the skin material to the total plate thickness), and a target plate thickness for hot rolling is set for each of the second material and the third material. The second material and the third material can be formed as a skin material as described above.

Before the skin material (second material, third material) and the ingot (first material) of the core material are stacked, the surface of the skin material may be subjected to a brushing treatment and a chemical conversion treatment in order to improve the skin adhesion during the compounding. In addition, the skin material may be cut in the width direction and the length direction by a saw before being stacked with the ingot (first material) of the core material.

3.2. Method for manufacturing core material

Next, a method for producing the first material, which is a raw material of the core material, will be described. The method of melt casting the first material may be the same as the above-described skin material, and the casting conditions (temperature, melt treatment, addition of a refiner, mold size, casting speed, etc.) may be adjusted to conditions suitable for the production of the first material. Wherein the width of the mold is set to 900mm or more to prevent the reduction of productivity.

Next, cutting of the beginning and/or ending portion of the casting of the ingot of the first material is performed. The reason for cutting the beginning and/or ending of the casting of the ingot of the first material is the same as for the skin. The length of the start and/or end of the casting of the cut ingot of the first material is about 100 to 200 mm. Instead of cutting the ingot of the first material, a portion corresponding to the start and/or end of casting may be cut in a clad rolling, cold rolling, slit (Slit) process, or the like. However, when cutting is performed after cladding rolling, scraps of a sheet material in which a skin material and a core material are integrated are formed, and recyclability is greatly reduced, so that it is preferable to cut a start portion and/or an end portion of casting in advance at the stage of casting of the first material.

When homogenizing the ingot of the core material, the temperature of the homogenizing treatment is 580 to 620 ℃. This temperature is the same as the heating temperature before cladding rolling described later. The homogenization treatment time is set to 6 hours or longer.

Desirably, the homogenization treatment of the ingot of the core material is performed before the surface cutting. This is because, when the homogenization treatment is performed after the surface cutting, the oxide film of the surface cutting face grows due to heating in the homogenization treatment. The upper and lower surfaces of the casting block are subjected to surface cutting of at least 3mm or more. The thickness of the ingot of the core material after the surface cutting is strictly set to control the cladding ratio, and the surface cutting is performed so as to be the thickness. In summary, an ingot (first material) of the core material can be formed.

In order to prevent edge breakage after cladding rolling, surface cutting of the end face of the core material in the width direction of the ingot may be performed. In this case, the width of the ingot of the core material after the surface cutting is equal to or more than the width of the skin material. In order to improve the pressure-bonding property in cladding rolling, the ingot of the core material after surface cutting may be brushed or etched with caustic soda or the like.

3.3. Superposition

The first material and the skin material (second material, third material) prepared as described above are stacked in the thickness direction to produce a stacked material. At this time, the overlapping order in which the first material is sandwiched by the second material and the third material in the thickness direction is set. In the subsequent heating process, the first material to the third material are usually fixed with Iron hoops (ironband) in such a manner that the first material to the third material are not offset from each other. The overlapping material can be welded, or welding and fixation by the iron hoop can be used in combination to replace fixation by the iron hoop.

3.4. Cladding rolling

When forming a rolled sheet in cladding rolling, the overlapped material is heated so as to be a cladding rolling temperature. In the present invention, the heating before cladding rolling is performed at 460 to 500 ℃ for 2 hours or more. This is because, when the heating temperature before cladding is lower than 460 ℃, it is difficult to set the cladding start temperature, which will be described later, to 420 ℃. The heating of the overlapping material in this temperature domain is done for the following purpose: setting the temperature to be capable of cladding rolling; and precipitating elements that are solid-dissolved during casting as fine intermetallic compounds, thereby improving the brazability and strength. When the heating temperature before cladding is higher than 500 ℃, the precipitation of intermetallic compounds is insufficient, and the amount of solid solution elements increases. Therefore, the intermetallic compound is precipitated during cladding rolling, and thus, the amount of the intermetallic compound varies between the end portions and the central portion in the longitudinal direction and the width direction, and the characteristic varies.

The heating time before cladding rolling is set to be more than 2 hours. After 2 hours have elapsed, the start of cladding rolling is generally waited in a heated state according to the operation conditions of the equipment after the subsequent steps, and the upper limit of the wait time is about 18 hours. By limiting the heating time in this way, variations in characteristics (mechanical characteristics, corrosion resistance) due to variations in heating time can be reduced.

Cladding rolling is performed on the heated overlapped material by a hot rolling mill, whereby integration by crimping is performed. The starting temperature of cladding rolling was 420 ℃ or higher. The starting temperature of cladding rolling may be measured at the side or upper surface (skin) or lower surface (skin) of the ingot. The rolling pass of cladding rolling was started within 5 minutes after the rolling start temperature was measured.

If the temperature difference from the completion of heating before cladding rolling to the start of cladding rolling is large, the cooling of the outside of the ingot is increased, and therefore, variation in characteristics is liable to occur. Therefore, the rolling start temperature of cladding rolling was 420 ℃ or higher.

Cladding rolling of overlapped material typically includes a rolling pass at a light reduction called a joint pass and a subsequent usual rolling pass. The joint pass is a rolling pass for bonding the skin material to the core material metal. The rough rolling and the finish rolling of the clad rolling may be performed by different rolling mills, or the rough rolling and the finish rolling of the clad rolling may be performed by the same rolling mill.

The finishing temperature of cladding rolling is set to 280-320 ℃. When the finishing temperature of cladding rolling exceeds 320 ℃, the cooling rate of the coil of the rolled sheet after finishing is different at the coil end portion from that at the center portion, and thus a difference in characteristics occurs. Further, by controlling the finishing temperature of cladding rolling to a narrow range of 280 ℃ or higher, variation in characteristics of rolled plates between coils is reduced.

The thickness of the cladding rolled sheet is 6mm or less. When cold rolling is started with a plate thickness thicker than 6mm, the rolling reduction when the target plate thickness is reduced by cold rolling is increased to a desired level or more. As a result, the crystal grains after cold rolling are refined, and thus, corrosion occurs during brazing. Further, the number of cold rolling passes for rolling down to the target plate thickness increases, and the manufacturing cost increases.

3.5. Cold rolling/annealing

The coil of the rolled sheet obtained by cladding rolling is subjected to several passes of cold rolling, whereby the sheet thickness of the product (aluminum alloy composite material for heat exchanger) is set. The number of cold rolling passes may be determined according to the rolling capability of the rolling mill. Then, annealing is performed on the rolled sheet of the final pass in which the cold rolling is completed. The number of times of annealing may be one or more, or may be two or more. In addition, the annealing conditions may be selected to be the most suitable conditions for the aluminum alloy composite material for each heat exchanger to be produced.

Specifically, the material is annealed at 350 to 400 ℃ for 3 hours or longer to obtain an O material. When the annealing temperature is 350 ℃ or lower, the tempering cannot be changed to an O material. On the other hand, when the annealing temperature is 400 ℃ or higher, formation of sparse second layer particles, zn evaporation from the skin material, and the like occur, and mechanical properties and corrosion resistance are lowered. In addition, in the case where the annealing time is less than 3 hours, the difference between the time at which the annealing temperature is maintained in the vicinity of the surface of the coil and the vicinity of the winding core becomes large, and therefore, the variation in mechanical properties and corrosion resistance of the material becomes large.

3.6. Surface treatment

For the purpose of brazability and formability, a coil before annealing and a coil after cold rolling may be subjected to surface treatment. In the present invention, no provision is made for surface treatment. This is because the surface treatment affects the state of the coil surface, but the present invention obtains the effect of the present invention by controlling the metal structure inside the material, and the surface treatment is not relevant to the present invention.

3.7. Slitting process

The cold rolled (annealed) coil is processed into a coil of a predetermined plate width for use in the manufacture of a heat exchanger by slitting. Since it is necessary to precisely perform the fine slitting for obtaining the product coil, a slitting process called rough slitting may be performed before the slitting process. Rough cutting is a process of cutting the width and length of a cold rolled (annealed) coil in accordance with the number and diameter of coils completed by finish cutting.

Slitting is a cutting process that does not affect the effects of the present invention. That is, the present invention obtains the effect of the present invention by controlling the metal structure in the material, and therefore the slitting process may be performed by a conventional method, and the method is not particularly limited.

4. Application method of aluminum alloy composite material for heat exchanger

The aluminum alloy composite material for heat exchangers produced in the above manner is used as a refrigerant passage component member such as an evaporator and an inverter of an automotive heat exchanger. The flow path is formed by bending, and the flow path is combined with a box material, a fin material, or the like to form a core shape of the heat exchanger, and then integrated by a brazing process. Soldering is performed by a so-called CAB method in which heating is performed in a non-oxidizing atmosphere using a non-corrosive flux. Alternatively, brazing may be performed by a VB (vacuum brazing) method in which heating is performed under a vacuum atmosphere without using a flux.

Examples (example)

Through the process shown in fig. 2, an aluminum alloy composite material for heat exchangers having a three-layer structure shown in fig. 3 was produced. The following is a detailed description.

1. Production of third Material as Material for brazing Material

To produce an Al-10.2 mass% Si alloy ingot, an aluminum alloy melt was obtained by blending and using a melting furnace. The temperature of the melt is set to 700-850 ℃. The obtained melt was transferred to a holding furnace, and casting was started after dross removal and composition and temperature adjustment were performed. Between the holding furnace and the casting machine, degassing and the de-chucking treatment by the ceramic filter were performed.

Casting is performed by vertical semi-continuous casting (so-called DC casting). Using a mold having a thickness of 500mm and a width of 1460mm, an ingot of about 3.9 tons was obtained. The casting temperature was set at 630 to 670℃and the casting speed was set at 45 to 55 mm/min. The temperature of the holding furnace was set to 660 to 700 ℃.

The composition of the resulting ingots is shown in table 1.

TABLE 1

In the table, the unit is mass%, and the remainder excluding unavoidable impurities is Al.

The content of the element not shown in table 1 is 0.02 mass% or less. After 10mm surface cutting was performed on the upper and lower surfaces of the ingot, heating was performed at 470 to 490 ℃ for hot rolling. The third material is manufactured by hot rolling until the thickness of the sheet is set for the lamination step, and cutting the sheet into a predetermined length.

2. Production of a second Material as a raw Material for sacrificial anticorrosive Material

To produce an Al-10.2 mass% Si-2.7 mass% Zn alloy ingot, an aluminum melt was obtained by blending and using a melting furnace. The obtained melt was transferred to a holding furnace at a temperature of 700 to 850 ℃ and casting was started after dross removal and composition and temperature adjustment.

Between the holding furnace and the casting machine, degassing and the de-chucking treatment by the ceramic filter were performed. Casting was performed by vertical semi-continuous casting (so-called DC casting), and a mold having a thickness of 500mm and a width of 1240mm was used, to obtain an ingot of about 3.7 tons. The casting temperature was set at 630 to 670℃and the casting speed was set at 45 to 55 mm/min. The temperature of the holding furnace was set to 660 to 700 ℃. The composition of the resulting ingots of the second material is shown in table 1. The content of the element not shown in the table is 0.02 mass% or less.

Surface cutting was performed after cutting 0.1m from the casting start (bottom) of the ingot and removal. After 10mm surface cutting was performed on the upper and lower surfaces of the ingot, 470 to 490 ℃ heating was performed for hot rolling. The second material is manufactured by performing hot rolling until the plate thickness set for the compounding step is reached and cutting the plate to a predetermined length.

3. Production of first Material as Material for core Material

To manufacture an ingot of the first material, the aluminum melt is obtained by compounding and using a melting furnace. The temperature of the melt is 700-850 ℃. The obtained melt was transferred to a holding furnace, and casting was started after dross removal and composition and temperature adjustment were performed.

A rod containing a refiner of Al-5Ti-1B was used for refining an ingot structure by performing a degassing treatment and a ceramic filter treatment between a holding furnace and a casting machine. Casting was performed by vertical semi-continuous casting (so-called DC casting), and a mold having a thickness of 420mm and a width of 1300mm was used, to obtain an ingot of about 5.6 tons (length of about 3.9 m). The casting temperature is 680-720 ℃ and the casting speed is 45-55 mm/min.

The composition of the resulting ingots is shown in table 1. The content of the element not shown in the table is 0.02 mass% or less. About 0.2m was cut from the casting start portion (bottom) and casting end portion (head) of the ingot, and an ingot having a length of 3.75m was produced. Then, a homogenization treatment is performed at 605 to 615 ℃. The minimum holding time for the homogenization treatment was 6 hours.

The ingot subjected to the homogenization treatment was subjected to surface cutting, and the thickness of the ingot was set to 400mm. In addition, in order to prevent breakage of the end face, the end face was subjected to surface cutting of only 4mm to manufacture the first material.

4. Superposition

The first material having a length of 3.75m and a width of 1.3m and a thickness of 0.4m, the second material having a length of 3.6m and a thickness of 0.1m, and the third material having a length of 3.6m and a thickness of 0.07m were stacked in the thickness direction. And fixing the overlapped materials by using iron hoops. The width of the overlapped material was set to 1.3m and the thickness was set to 0.57m.

5. Cladding rolling

Next, a rolled sheet is formed by cladding rolling of the overlapped material. Heating at 460-500 deg.c before cladding, placing overlapping material on the conveying line of hot rolling mill, and unloading the iron hoop for cladding. After the joining pass at a start temperature of 450℃and a soft reduction was performed, a hot-rolled coil was obtained by winding up a sheet having a width of 1160mm by performing a usual clad-rolling pass. The coil temperature at the end of cladding rolling was 290 ℃.

6. Cold rolling/annealing

The coil of the rolled sheet obtained by cladding rolling was subjected to several passes of cold rolling, whereby a sheet having a thickness of 0.57mm after the final rolling pass was produced, and the sheet was wound to produce a coil. The standard deviation of the plate thickness after the final rolling pass was 1.62. Mu.m. Annealing was performed by holding the coil at 360 to 380 ℃ for 4 hours. Annealing is performed in a non-oxidizing atmosphere.

7. Slitting process

Next, the coil is divided into two in the width direction by slitting processing. In the slitting process, the beginning and end of the coil whose plate thickness becomes unstable are each cut by about 100mm.

8. Evaluation results

Samples were collected from the beginning and end of the coil of the aluminum alloy composite material for heat exchanger manufactured as described above, and tensile tests were performed, respectively. The tensile strength of the sample collected from the beginning of the coil was 121MPa, the yield strength was 47MPa, and the elongation was 33%. The tensile strength of the sample collected from the end of the coil was 121MPa, the yield strength was 49MPa, and the elongation was 33%. From this, it is clear that the aluminum alloy composite material for heat exchangers of the present invention has small variation in characteristics.

The aluminum alloy composite material for heat exchangers of this example was subjected to bending processing to be formed into a header shape, and then combined with a pipe, a box material, or the like, and brazed to produce an evaporator. Brazing uses a fluoride-based non-corrosive flux and heating is performed in nitrogen at a temperature in the range of 590 to 610 ℃. Since the Si content of the sacrificial resist (second material) of this embodiment is the same as that of the solder (third material), solder is produced from the sacrificial resist and the solder, respectively, and soldering can be performed on each surface side. In the evaporator using any one of the above-mentioned strips, the brazed core is free from leakage, and the evaporator can be used as a practical automotive heat exchanger without any problem in terms of strength and corrosion resistance.

Another embodiment

The aluminum alloy composite material for heat exchangers manufactured by the manufacturing method of the present invention is not limited to the constitution of the embodiment. Specifically, the chemical composition of the sacrificial resist material is also not limited to that of the embodiments. By adjusting the Si content in the sacrificial resist to about 9 to 12 mass%, solder can be supplied from the sacrificial resist in the same manner as in the above-described example. In addition, in the case where the solder is not supplied from the sacrificial resist either, the Si content in the sacrificial resist may be adjusted to be less than 9 mass%.

Further, the aluminum alloy composite material for heat exchangers manufactured by the manufacturing method of the present invention is not limited to the layer structure of the embodiment. Specifically, the aluminum alloy composite material for heat exchangers may have a two-layer structure or a four-layer structure.

For example, the brazing filler metal may be omitted from the layer structure of the embodiment, or an aluminum alloy composite material for heat exchangers having a two-layer structure composed of a sacrificial corrosion-preventing material whose Si content is suppressed and a core material may be produced. Although the solder cannot be supplied from such an aluminum alloy composite material for heat exchangers, the heat exchanger can be formed by combining the aluminum alloy composite material with a brazing sheet provided with the solder.

Further, by adding a brazing filler metal to the layer composition of the above-described embodiment, an aluminum alloy composite material for a heat exchanger having a four-layer structure can be produced. Specifically, the solder may be laminated on the sacrificial resist in the above-described embodiment so that the solder is laminated on both sides of the aluminum alloy composite material for heat exchangers. In this case, the necessity of supplying solder from the sacrificial resist is reduced, and therefore the Si content in the sacrificial resist can also be made smaller than in the embodiment.

In the production of the above-described aluminum alloy composite materials for heat exchangers, the aluminum alloy composite material for heat exchangers having excellent characteristics can be produced using a large ingot by applying the present invention.

Description of the reference numerals

1: a tube; 2: a fin; 3: a header plate; 4: a box.

Claims

1. A method for producing an aluminum alloy composite material for a heat exchanger, wherein the aluminum alloy composite material for a heat exchanger comprises:

a core material formed of an aluminum alloy containing 0.9 mass% or less of Si, 0.75 mass% or less of Fe, 0.7 mass% or less of Cu, and 0.6 to 1.9 mass% of Mn, wherein the aluminum alloy contains one or more of 0.3 mass% or less of Mg, 0.3 mass% or less of Cr, 0.3 mass% or less of Zr, and 0.3 mass% or less of Ti; and

the sacrificial anticorrosive material is formed of an aluminum alloy containing 0.8 to 4.5 mass% of Zn,

the method for manufacturing the aluminum alloy composite material for the heat exchanger comprises the following steps:

forming a first material as a raw material of the core material by at least melting, casting, and surface cutting;

forming a second material as a raw material of the sacrificial anticorrosive material by performing at least melting, casting, hot rolling, and cutting;

integrating a stacked material obtained by stacking the first material and the second material in the thickness direction by at least hot cladding rolling, thereby forming a rolled material;

a step of cold-rolling the rolled material; and

annealing the rolled material after the cold rolling,

heating the overlapped material for more than 2 hours at 460-500 ℃ before cladding rolling,

the temperature of the overlapped material at the beginning of the cladding rolling is 420 ℃ or higher,

the temperature of the rolled material at the end of the cladding rolling is 190 to 350 ℃,

the thickness of the rolled material at the end of the cladding rolling is 6mm or less,

the annealing temperature is above 350 ℃, and the annealing time is above 3 hours.

2. The method for producing an aluminum alloy composite material for heat exchangers according to claim 1, wherein,

the sacrificial corrosion barrier material has a thickness of 5 to 25% of the overall sheet thickness,

the sacrificial anticorrosive material contains 12 mass% or less of Si, 1.0 mass% or less of Fe, 1.0 mass% or less of Mn, and 0.8 to 4.5 mass% of Zn, and contains one or more of 0.5 mass% or less of Cu, 0.6 mass% or less of Mg, 0.3 mass% or less of Cr, 0.3 mass% or less of Zr, and 0.3 mass% or less of Ti.

3. The method for producing an aluminum alloy composite material for heat exchangers according to claim 1 or 2, wherein,

a brazing filler metal made of an aluminum alloy is laminated on at least one surface,

the aluminum alloy has a thickness of 5 to 25% of the overall plate thickness,

the aluminum alloy contains 5 to 12 mass% of Si, 1.0 mass% or less of Fe, 1.5 mass% or less of Mg, 0.3 mass% or less of Zn, 0.2 mass% or less of Bi and 0.05 mass% or less of Sr, and contains one or more of 0.5 mass% or less of Cu, 0.3 mass% or less of Mn, 0.3 mass% or less of Zn, 0.3 mass% or less of Cr, 0.3 mass% or less of Zr and 0.3 mass% or less of Ti,

forming a third material as a raw material of the brazing filler metal by at least melting, casting, hot rolling, and cutting,

the overlapped material obtained by overlapping the first material, the second material, and the third material in the thickness direction is integrated by at least cladding rolling.