JP2016017222A - Aluminum alloy clad material and heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy clad material adding corrosion resistance in a high cooling water side while having a layer structure of which both sides has a wax material, capable of forming complex structure and suppressing material manufacturing cost, a heat exchanger using the clad material.SOLUTION: An aluminum alloy clad material is an aluminum alloy clad material of which double faces of a core material is clad by a shell material, the shell material contains Si:3 mass% to 6 mass%, Zn:2 mass% to 4 mass% and the balance Al with inevitable impurities, a core material contains Mn:0.8 mass% to 1.8 mass%, Si:0.05 mass% to 0.5 mass%, Cu:0.05 mass% to 0.3 mass%, Fe:0.1 mass% to 0.6 mass% and the balance Al with inevitable impurities and crystal particle diameter of the core material after a heat treatment at 600°C to 610°C for 3 minutes to 15 minutes in a range of 50 μm to 200 μm.SELECTED DRAWING: None

Description

  The present invention relates to an aluminum alloy clad material used for automobile heat exchanger parts and the like and a heat exchanger using the clad material.

  In recent years, the demand for heat exchangers for cooling other parts and fluids has increased. Since these heat exchangers are cooled with water (or water + LLC), high corrosion resistance is required on the cooling water flow path side. Furthermore, since it is also necessary to join with other members, a brazing sheet made of a sacrificial material, a core material, and a brazing material is often used for the application.

The aluminum alloy clad material for heat exchanger disclosed in Patent Document 1 contains Mn, Cu as the core material, and the remaining alloy composed of Al and inevitable impurities is used. Alternatively, an Al—Si—Zn-based brazing material is clad, and the other surface contains one or two of Fe and Ni, and the remainder is clad with a sacrificial anode skin material made of Al and inevitable impurities.
The aluminum alloy clad material for a heat exchanger disclosed in Patent Document 2 contains Mn and Cu, and the remainder is Al-Si or Al-Si-Zn brazing on one side of a core material composed of Al and inevitable impurities. The material is clad, and the other surface is clad with a sacrificial anode skin material containing Mn and the remainder consisting of Al and inevitable impurities.
The aluminum alloy brazing sheet disclosed in Patent Document 3 contains Mn, Si, Cu, Fe, Mg, Zn, and the remainder contains Si and Zn on one side of the core material composed of Al and inevitable impurities. The rest is brazing material made of Al and unavoidable impurities, and the other surface is clad with a sacrificial material containing Zn, Mg, Mn, Si, and the remainder made of Al and unavoidable impurities.

JP 2000-297338 A JP 2000-297339 A Japanese Patent No. 382047

  However, the heat exchanger used for such an application takes various forms and may have a complicated structure. Therefore, when there is only a brazing material layer on one side, the structure is limited. There is. On the other hand, when brazing materials are arranged on both sides, the above problem is solved, but there is a problem that the corrosion resistance on the cooling water side becomes insufficient. In addition, a four-layer material in which a brazing material is further provided on the sacrificial material side of a brazing sheet made of a sacrificial material, a core material, and a brazing material can also be used. End up.

  The present invention has been made in view of such a background, and although it is a layered structure in which brazing material is arranged on both sides, it can provide high corrosion resistance on the cooling water side and can form a complicated structure. An object of the present invention is to provide an aluminum alloy clad material with reduced material production costs and a heat exchanger using the clad material.

  The aluminum alloy clad material of the present invention is an aluminum alloy clad material in which a skin material is clad on both sides of a core material, and the skin material is composed of Si: 3 mass% to 6 mass%, Zn: 2 mass% to 4% by mass, the balance is made of Al and inevitable impurities, and the core material is Mn: 0.8% by mass to 1.8% by mass, Si: 0.05% by mass to 0.5% by mass, Cu : 0.05% by mass to 0.3% by mass, Fe: 0.1% by mass to 0.6% by mass, with the balance consisting of Al and inevitable impurities, and further at 600 ° C to 610 ° C for 3 minutes to 15 The crystal grain size of the core material after heat treatment for 5 minutes is in the range of 50 μm to 200 μm.

[Skin material ingredients]
Since Si lowers the melting point of the material, when added to the skin material, it has an effect of providing a function of melting and joining to other members during brazing heat treatment. If the amount is less than the lower limit, the effect is not sufficiently exhibited. If the upper limit is exceeded, the flowability of the molten braze becomes too high, and the brazing thickness remaining after brazing decreases and the surface Zn concentration decreases and the corrosion resistance deteriorates. .
Since Zn lowers the potential of the material, when it is added to the skin material, it has the effect of preventing the core material by lowering the potential of the skin material. If it is less than the lower limit, the effect is not sufficiently exhibited, and if it exceeds the upper limit, Zn is excessively concentrated in the joint portion and becomes preferentially corroded, so that the corrosion resistance of the joint portion is deteriorated.

[Core material component]
Mn forms an Al—Mn—Si, Al—Mn—Fe, and Al—Mn—Fe—Si intermetallic compound in the matrix and has the effect of increasing the strength of the material. If the amount is less than the lower limit, the effect is not sufficiently exhibited. If the amount exceeds the upper limit, a huge intermetallic compound is generated at the time of casting, so that the formability of the material is deteriorated.
Si has the effect of forming Al—Mn—Si, Al—Mn—Fe, and Al—Mn—Fe—Si intermetallic compounds in the matrix to increase the strength of the material. If the amount is less than the lower limit, the effect is not sufficiently exhibited. If the amount exceeds the upper limit, a huge intermetallic compound is generated at the time of casting, so that the formability of the material is deteriorated.
Cu is dissolved in the matrix and has the effect of increasing the strength of the material. If it is less than the lower limit, the effect is not sufficiently exhibited, and if it exceeds the upper limit, intergranular corrosion tends to occur and the corrosion resistance is lowered.
Fe has the effect of forming coarse Al—Mn—Fe and Al—Mn—Fe—Si intermetallic compounds in the matrix and reducing the crystal grain size after brazing heat treatment. If the amount is less than the lower limit, the effect is not sufficiently exhibited. If the amount exceeds the upper limit, a huge intermetallic compound is generated at the time of casting, so that the formability of the material is deteriorated.

[Crystal grain size of core material after heat treatment]
Grain boundaries become the starting point for wax erosion and become a resistance to the flow of molten wax. For this reason, when the crystal grain size of the core material just before the melting of the brazing is fine, the flowability of the brazing is lowered, and there is an effect of increasing the thickness of the brazing material remaining after brazing. Moreover, since the surface Zn density | concentration after brazing increases in connection with it, corrosion resistance improves.
The heat treatment conditions are assumed to be brazing conditions. When the crystal grain size of the core material after the heat treatment is less than the lower limit, the number of starting points of brazing erosion becomes excessive and significant erosion occurs. When the upper limit is exceeded, the effect of lowering the flowability of the wax becomes insufficient, the residual wax thickness becomes thinner, and the surface Zn concentration decreases to deteriorate the corrosion resistance. Furthermore, the solder tends to flow into the joint, the Zn concentration in the joint becomes too high, and the corrosion resistance of the joint decreases. It should be noted that the crystal grain structure immediately before the solder melting and the crystal grain structure after brazing hardly change.

  In the aluminum alloy clad material of the present invention, Al-Mn, Al-Mn-Si, Al-Mn-Fe, Al-Mn-Fe-, which are second phase particles excluding the crystallization phase in the core material. It is preferable that the circle-equivalent average diameter of the Si-based compound is in the range of 0.1 μm to 0.8 μm.

  The size of the second phase particles excluding the crystallization phase in the core material affects the crystal grain size of the core material. If fine particles are distributed, annealing during the manufacturing process, and brazing heat treatment The recrystallization at the time is delayed to make the crystal grain size of the core material coarse. On the other hand, when coarse-sized particles are distributed, recrystallization is promoted to reduce the crystal grain size. If it is less than the lower limit, the crystal grain size becomes coarse. If the upper limit is exceeded, it becomes too fine and the wax erosion resistance decreases.

  In the aluminum alloy clad material of the present invention, the skin material further includes Mn: 0.05 mass% to 0.5 mass%, Fe: 0.05 mass% to 0.5 mass%, Sr: 0.05 mass%. One or more of ˜0.5 mass%, Ti: 0.05 mass% to 0.5 mass%, and Zr: 0.05 mass% to 0.5% may be contained.

  When Mn, Fe, Sr, Ti, Zr is added to the skin material (brazing material), there is an effect of reducing the fluidity of the brazing material. If it is less than the lower limit, the effect is not sufficiently exhibited, and if it exceeds the upper limit, a huge intermetallic compound may be formed.

  In the aluminum alloy clad material of the present invention, the core material may further contain one or more of Ti, Zr, and Cr in the range of 0.05% by mass to 0.3% by mass, respectively.

  When Ti, Zr, and Cr are added to the core material, there is an effect of improving the corrosion resistance by suppressing the progress of corrosion in the depth direction by making the corrosion form into a layer. If it is less than the lower limit, the effect is not sufficiently exhibited, and if it exceeds the upper limit, a huge intermetallic compound may be formed.

  In the heat exchanger of the present invention, at least a part of the aluminum alloy clad material of the present invention is brazed, and the Zn concentration of the surface of the aluminum alloy clad material in the unbrazed portion is 1.5 mass% to It is in the range of 3.0% by mass.

  The Zn concentration on the surface of the material after brazing is related to the magnitude of the anticorrosion performance of the skin against the core material. The higher the surface Zn concentration, the lower the potential of the skin material relative to the core material, and the anticorrosion of the core material. It's easy to do. If it is less than the lower limit, the anticorrosion performance with respect to the core material becomes insufficient, and the core material is likely to be corroded and the corrosion resistance is deteriorated. On the other hand, if the upper limit is exceeded, the corrosion rate of the skin material becomes too fast and the skin material is corroded and consumed at an early stage, thereby deteriorating the corrosion resistance.

  In the heat exchanger of the present invention, the maximum Zn concentration in the brazed joint of the aluminum alloy clad material is preferably less than 6% by mass.

  The maximum Zn concentration in the brazed joint is related to the corrosion rate of the joint (particularly the fillet), and the higher the maximum Zn concentration, the faster the corrosion rate. If the upper limit is exceeded, the corrosion rate will be too fast, and the fillet will be easily corroded and consumed.

  According to the present invention, by adjusting the components of the brazing material (Si content and Zn content) to predetermined values and controlling the metal structure of the core material, high corrosion resistance on the cooling water side while being brazing material. Can be granted. As a result, it is possible to provide a material that can form a complicated structure due to the presence of the brazing material on both sides, has excellent cooling water side corrosion resistance, and suppresses the material manufacturing cost.

It is a schematic diagram explaining the outline | summary of the sample prepared by the test for the effect confirmation of this invention.

Hereinafter, embodiments of the aluminum alloy clad material according to the present invention will be described.
This aluminum alloy clad material is used as an automotive heat exchanger component, and a skin material is clad on both sides of a core material. The skin material is Si: 3 mass% to 6 mass%, Zn: 2 mass%. -4 mass%, the balance is made of Al and inevitable impurities, and the core material is Mn: 0.8 mass% to 1.8 mass%, Si: 0.05 mass% to 0.5 mass%, Cu : 0.05% by mass to 0.3% by mass, Fe: 0.1% by mass to 0.6% by mass, the balance being made of a material of grade O consisting of Al and inevitable impurities, The crystal grain size of the core after heat treatment at 610 ° C. for 3 minutes to 15 minutes is in the range of 50 μm to 200 μm.
In this case, the circle equivalent average of the Al—Mn, Al—Mn—Si, Al—Mn—Fe, and Al—Mn—Fe—Si compounds, which are the second phase particles excluding the crystallization phase in the core material The diameter is preferably in the range of 0.1 μm to 0.8 μm.
In addition to the above basic composition, the skin material further comprises Mn: 0.05% by mass to 0.5% by mass, Fe: 0.05% by mass to 0.5% by mass, Sr: 0.05% by mass to 0.00%. You may contain 1 type (s) or 2 or more types in 5 mass%, Ti: 0.05 mass%-0.5 mass%, Zr: 0.05 mass%-0.5%.
Moreover, about core material, Ti, Zr, and Cr may contain 1 type (s) or 2 or more types in the range of 0.05 mass%-0.3 mass%, respectively.
Although these specific reasons are as above-mentioned, among these, as for Si content of a skin material, 4 mass%-5.5 mass%, and Zn content are further more preferable 3 mass%-4 mass%.

[Production method]
This aluminum alloy clad material is manufactured by the following method.
First, an aluminum alloy for a core material and an aluminum alloy for a skin material (brazing material) are cast by semi-continuous casting, and the ingot of the obtained core material is homogenized at a predetermined temperature.
This homogenization treatment is suitable at 530 ° C. to 610 ° C. for 3 hours to 20 hours, and by setting the temperature to a high temperature or a long time side, the second phase particles become coarse and the crystal grain size after brazing becomes fine. There is an effect. The skin material need not be homogenized, but may be homogenized.
After this homogenization treatment, the ingot of the core material is combined with the ingot of the skin material and hot-rolled to form a clad material, further rolled to the desired thickness by cold rolling, and further subjected to final annealing, for example By performing the treatment at 350 ° C. for 6 hours, a grade O cladding material is obtained. Hot rolling, cold rolling, and final annealing may be performed by conventional methods. However, a manufacturing process is not limited to this, It is also possible to add intermediate annealing in the middle of cold rolling.
The final configuration of the aluminum alloy clad material is a ratio of thickness, for example, skin material: core material: skin material = 10%: 80%: 10%, but is not limited to this. For example, The clad rate of the skin material may be 12%, 15% or 20%.

[Assembling to heat exchanger by brazing]
The aluminum alloy clad material manufactured in this way is used as a member for a heat exchanger of an automobile, and at least a part of one side or both sides thereof is brazed with other parts and assembled to the heat exchanger. The brazing conditions in this case are suitably held at 595 ° C. to 620 ° C. for 1 minute to 15 minutes.
In particular, by controlling the brazing condition at 595 ° C. to 610 ° C. for 1 minute to 7 minutes, the Zn concentration on the surface of the aluminum alloy clad material in the unbrazed portion after brazing is 1.5% by mass. It is in the range of -3.0% by mass, and the maximum Zn concentration in the brazed joint is less than 6% by mass.
With such a Zn concentration, the corrosion resistance to cooling water is further improved, and corrosion and wear are less likely to occur.

  The aluminum alloy for core material having the composition shown in Table 1 and the aluminum alloy for skin material (brazing material) having the composition shown in Table 2 were cast by semi-continuous casting, and the obtained core material was subjected to the homogenization treatment shown in Table 3. It was. The core material ingots are overlapped with the combinations shown in Table 3 on both sides of the core material ingot and hot-rolled, cold-rolled to a thickness of 0.6 mm, and further subjected to final annealing at 350 ° C. for 6 hours. An aluminum alloy clad material of O was produced. The composition of the clad material was the ratio of thickness: skin material: core material: skin material = 10%: 80%: 10%.

  About the obtained aluminum alloy clad material, the circle equivalent average diameter of the second phase particles in the core material, the crystal grain size of the core material after heat treatment, the Zn concentration of the surface after brazing, the Zn concentration of the brazed joint Measurements were made to evaluate wax erosion resistance, bondability and internal erosion.

[Average equivalent circle diameter of second phase particles in the core]
The prepared sample was exposed in the vicinity of the center of the core material by alkali etching with caustic soda and mechanical polishing, a thin film was prepared by mechanical polishing and electrolytic polishing by a conventional method, and a photograph was taken with a TEM at a magnification of 10,000 times. Image analysis was performed on five fields of photographed photographs to determine the average size of the second phase particles. At that time, those having a size of 1 μm or more were judged as crystallized substances and excluded from the measurement.

[Crystal grain size of core material after heat treatment]
As shown in FIG. 1A, a 1.0 mm-thick plate 1 made of O material of JIS3003 aluminum alloy and a clad material sample 2 are prepared, and these are subjected to heat treatment under the conditions shown in Table 3 as shown in FIG. And brazed as shown in FIG. A sample is taken from the non-joined part 4 of the brazed joined body 3, and a longitudinal section parallel to the rolling direction of the material is filled with resin, then polished to a mirror surface by emery polishing and buff polishing, and then an anode using Barker's liquid Crystal grains were revealed by oxidation, and the crystal grain structure of the core material was observed with a polarizing microscope. The photographing magnification was set to 100 times, and when the observation became difficult when the crystal grains were fine or coarse, 200 times or 50 times was selected. The number of fields of view was three, and the crystal grain size was measured by a cutting method in the rolling direction from the photograph taken.

[Zn concentration on the surface after brazing]
A sample is taken from the non-joined portion 4 of the brazed joined body 3, and after filling the portion with resin, it is polished to a mirror surface by emery polishing and buff polishing, and then the Zn diffusion state is investigated by EPMA line analysis (the step size is 1 μm), the average Zn concentration at a position of 3 μm to 7 μm from the surface of the material was determined and used as the surface Zn concentration. The Zn concentration was measured at five locations, and the average was obtained.

[Zn concentration in brazed joints]
A sample is taken from the joint portion 5 of the brazed joint 3 and the cross-section of the joint portion is polished to a mirror surface by emery polishing and buffing after filling in the resin, and then the Zn diffusion state is investigated by EPMA line analysis. (Step size is 1 μm) and the maximum Zn concentration to be measured was determined. The maximum Zn concentration was measured at five locations and the average was determined.

[Wax erosion resistance]
A sample is taken from the joined part 5 of the brazed joined body 3, and after filling the part with resin, the cross-section of the joined part is polished to a mirror surface by emery polishing and buffing, and then observed with an optical microscope. The state of erosion of erosion (erosion depth) was investigated.
The case where the erosion depth was 50 μm or more was rated as x, and the case where the erosion depth was less than 50 μm was rated as ◯.

[Jointability]
A sample is taken from the joined part 5 of the brazed joined body 3, the portion is filled with resin, the cross section of the joined part is polished to a mirror surface by emery polishing and buffing, and then observed with an optical microscope. The length was measured, and “(joining length excluding voids) / (contact length before brazing)” was evaluated as a joining rate from the relationship with the contact length before brazing.
The case where the joining rate was less than 80% was rated as x, the case where it was 80% or more and less than 90% was marked as ◯, and the case where it was 90% or more was marked as 〇.

[Internal corrosion resistance]
After masking the end of the joined body 3 and the side opposite to the evaluation surface, 80 ° C. × 8 hours → room temperature × in an aqueous solution containing Cl ⁻ : 195 ppm, SO ₄ ²⁻ : 60 ppm, Cu ²⁺ : 1 ppm, Fe ³⁺ : 30 ppm. The immersion test was conducted for 10 weeks with a 16 hour cycle. The sample after the corrosion test was immersed in a boiled phosphoric acid chromic acid mixed solution to remove the corrosion products, and then a cross-sectional observation was performed on each of the joint and non-joint to measure the corrosion state.
Regarding the corrosion resistance of the non-joined part 4, the case where the corrosion depth exceeded 150 μm was evaluated as “X”, the case where it exceeded 100 μm and was 150 μm or less was rated as “◯”, and the case where it was 100 μm or less was rated as “◯”.
With respect to the corrosion resistance of the joint 5, the corrosion length is 1/2 or more with respect to the length of the joint 5, and the corrosion resistance of less than 1/2 is 1/3 or more is 1/3. Those that were less than 0 were marked as 0.

[Comprehensive evaluation]
Of the above evaluation items, one of which was x, x, all of which were ○ or ○ ○, those of which the erosion depth was 0 and the others were ○○ XX.
These results are shown in Table 4.

In Table 4, no. Since the joining rate in the brazed joined body 3 was as low as 50% due to the low Si content of the skin material component 1, the corrosion resistance of the joint was set to “Not evaluated”. No. On the other hand, 5 is inferior in corrosion resistance because the skin material has too much Si content. No. No. 6 is inferior in the anticorrosive effect on the core material because the Zn content of the skin material is small. On the other hand, since the Zn content of the skin material is too large, the corrosion resistance of the joint is inferior. No. No. 22 has a large erosion depth because the core has a small crystal grain size. Since No. 26 has a large crystal grain size, the corrosion resistance of the surface (non-bonded portion) is inferior. No. In No. 28, since the crystal grain size of the core material is too large, the surface Zn concentration is low and the surface corrosion resistance is poor.
The clad materials other than these had a comprehensive evaluation of ◯ or higher, and both the bondability and corrosion resistance were good.

  In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.

1 plate 2 clad material 3 joined body 4 non-joined part 5 joined part

Claims (6)

  An aluminum alloy clad material in which a skin material is clad on both sides of a core material, wherein the skin material contains Si: 3% by mass to 6% by mass, Zn: 2% by mass to 4% by mass, and the balance It consists of Al and inevitable impurities, and the core material has Mn: 0.8% by mass to 1.8% by mass, Si: 0.05% by mass to 0.5% by mass, Cu: 0.05% by mass to 0.00%. 3% by mass, Fe: 0.1% by mass to 0.6% by mass, the balance is made of Al and inevitable impurities, and the core crystal after heat treatment at 600 ° C. to 610 ° C. for 3 minutes to 15 minutes An aluminum alloy clad material having a particle size in the range of 50 μm to 200 μm.   Among the second phase particles excluding the crystallization phase in the core material, the equivalent circle average diameter of Al-Mn, Al-Mn-Si, Al-Mn-Fe, and Al-Mn-Fe-Si compounds. The aluminum alloy clad material according to claim 1, wherein is in the range of 0.1 μm to 0.8 μm.   The skin material further includes Mn: 0.05 mass% to 0.5 mass%, Fe: 0.05 mass% to 0.5 mass%, Sr: 0.05 mass% to 0.5 mass%, Ti: The aluminum alloy according to claim 1 or 2, characterized by containing one or more of 0.05% by mass to 0.5% by mass and Zr: 0.05% by mass to 0.5%. Clad material.   4. The core material according to claim 1, further comprising Ti, Zr, and Cr in a range of 0.05 mass% to 0.3 mass%, respectively. The aluminum alloy clad material described.   The aluminum alloy clad material according to any one of claims 1 to 4, wherein at least a part of the aluminum alloy clad material is brazed, and the Zn concentration of the surface of the aluminum alloy clad material in the unbrazed portion is 1.5 mass%. A heat exchanger characterized by being in the range of -3.0% by mass.   The heat exchanger according to claim 5, wherein the maximum Zn concentration in the brazed joint of the aluminum alloy clad material is less than 6 mass%.

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