JP6792476B2 - Aluminum alloy plate and its manufacturing method - Google Patents

Description

The present invention relates to an aluminum alloy plate material having excellent corrosion resistance, particularly an aluminum alloy plate material suitable as a heat exchanger fin material, and a method for producing the same.

Cu and Al alloys with excellent conductivity are often used for the fins of industrial heat exchangers. In addition to conductivity, fin materials are required to have properties such as corrosion resistance, strength, and moldability. So far, various methods for improving the above characteristics have been studied. For example, as a method for improving strength, corrosion resistance, and conductivity, a method for controlling the amount and mass ratio of Mn, Si, Fe, and Zn has been proposed (Patent Document 1). Further, as a method for improving the moldability of the plate material, a method of controlling the distribution density of intermetallic compounds in the plate material has been proposed (Patent Document 2). Conductivity here means both thermal conductivity and electrical conductivity. In the case of metal, it is generally known that a material having high thermal conductivity also has high electrical conductivity.

However, heat exchangers, especially industrial heat exchangers, may be used in harsh corrosive environments, and conventional fin materials may have insufficient corrosion resistance. Since the life of the fin material is short, the fin material is frequently replaced, or a coating for improving corrosion resistance is required, which leads to an increase in cost.

Patent Document 3 describes an aluminum alloy in which a predetermined amount of Mn and Mg is blended with aluminum and a small amount of Cr and Ti are blended, and the thickness is 50 to 200 μm (0.05 to 0.2 mm) and the electrical resistivity value is 6. A technique for producing a foil of 0.0 μΩcm or more is disclosed. It has been proposed that the techniques described in this document provide aluminum alloy foils that are highly corrosion resistant, have low conductivity, and are suitable for food packaging that can be cooked with an electromagnetic cooker. In the examples of this document, an aluminum alloy having a Si content of 0.03% by mass and an Fe content of 0.05% by mass is used, and the Mn content is at least 2.0. It is mass%.

However, the aluminum alloy foil disclosed in Patent Document 3 is characterized by having a high electrical resistivity value, that is, having low conductivity, and is therefore suitable for heat exchanger fin materials that require high conductivity. Absent.

Non-Patent Document 1 and Non-Patent Document 2 describe numerical values indicating the influence of additive elements on the electrical resistance of aluminum, and these numerical values will be used later, and are therefore referred to here.

Japanese Patent No. 5578702 Japanese Unexamined Patent Publication No. 2014-224323 Japanese Patent No. 5413734

Masahiro Miki, Junzo Takao, "Electrical Resistance of Aluminum", Sumitomo Chemical Technical Magazine, Sumitomo Chemical Co., Ltd., 1975, Toku 1975-I, p.41-52 "Basics of Aluminum Materials and Industrial Technology", Japan Aluminum Association, October 25, 2010, 1st Edition, 4th Print, p.344

The present invention has been made against the background of the above-mentioned actual conditions, and an object of the present invention is to provide an aluminum alloy plate material having excellent strength and conductivity and excellent corrosion resistance.

In the first aspect of the present invention, the Mn content is 0.1% by mass or more and 2.0% by mass or less, and the Mg content is 1/16 times or more and 1.6% by mass or less of the Mn content on a mass basis. An aluminum alloy plate material in which the balance is composed of Al and unavoidable impurity elements, the total content of Mn and Mg is 0.6% by mass or more, and the total content of the unavoidable impurity elements is 0.04% by mass or less. Is.

Aspect 2 of the present invention is the aluminum alloy plate material according to Aspect 1, wherein the total content of the unavoidable impurity elements is 0.02% by mass or less.

In the third aspect of the present invention, the Fe content is 0.025% by mass or less, and the total content of Si, Cu, Ti, V, Cr, Ni, Zn and Ga is 0.02% by mass or less. The aluminum alloy plate material according to the first or second aspect.

In the fourth aspect of the present invention, the Fe content is 0.003% by mass or less, and the total content of Si, Cu, Ti, V, Cr, Ni, Zn and Ga is 0.015% by mass or less. The aluminum alloy plate material according to the third aspect.

Aspect 5 of the present invention is an embodiment in which the solid solution rate of Mn in the base material calculated from the conductivity of the plate material is 40% or less, assuming that Mg is completely dissolved in the base material. The aluminum alloy plate material according to any one of 1 to 4.

Aspect 6 of the present invention is a fin material for a heat exchanger made of the aluminum alloy plate material according to any one of aspects 1 to 5.

In aspect 7 of the present invention, the Mn content is 0.1% by mass or more and 2.0% by mass or less, and the Mg content is 1/16 times or more and 1.6% by mass or less of the Mn content on a mass basis. Aluminum alloy rolling in which the balance is composed of Al and unavoidable impurity elements, the total content of Mn and Mg is 0.6% by mass or more, and the total content of the unavoidable impurity elements is 0.04% by mass or less. An aluminum alloy including a step of producing a material for aluminum alloy, a rolling step of rolling the material for rolling an aluminum alloy, and a final annealing step of holding the material for rolling at 200 ° C. or higher and 450 ° C. or lower for 1 hour or longer after the rolling step. This is a method for manufacturing a plate material.

Aspect 8 of the present invention is the method for producing an aluminum alloy plate material according to Aspect 7, wherein the total content of the unavoidable impurity elements is 0.02% by mass or less.

Aspect 9 of the present invention is the method for producing an aluminum alloy plate material according to aspect 7 or 8, further comprising an intermediate annealing step of holding at 500 ° C. or higher for 5 hours or longer in the middle of the rolling step.

The aluminum alloy plate material of the present invention has excellent strength and conductivity, and also has excellent corrosion resistance. From such an aluminum alloy plate material, it is possible to provide a fin material for a heat exchanger having good properties.
Further, according to the production method of the present invention, it is possible to produce an aluminum alloy plate material having excellent strength and conductivity and excellent corrosion resistance.

FIG. 1 is a diagram showing the relationship between the Mn content and the Mg content in an aluminum alloy. FIG. 2 is an equation expressing the relationship between the atomic% and the mass% of the additive element X in aluminum.

The aluminum alloy plate used as the conventional heat exchanger fin material is an alloy made from aluminum having a purity of about 99% by mass, and contains some unavoidable impurity elements such as Fe. The present inventors have stated that such an unavoidable impurity element, particularly Fe, forms an intermetallic compound with Al and other alloying elements as a base material and becomes a starting point of corrosion, thereby lowering the corrosion resistance of the obtained aluminum alloy plate material. I focused on being there.
Then, by producing an aluminum alloy plate material using high-purity aluminum as a raw material, the content of unavoidable impurity elements such as Fe is sufficiently reduced, and further, Mn and Mg are contained as alloy elements in predetermined amounts. It has been found that an aluminum alloy plate material having excellent strength and conductivity can be obtained while maintaining the high corrosion resistance of high-purity aluminum.
That is, in order to obtain an aluminum alloy plate material having the strength and conductivity required for the heat exchanger fin material and further having sufficiently excellent corrosion resistance, the purity of aluminum used as a raw material is simply increased. It is not enough to reduce the content of unavoidable impurity elements that are the starting point of corrosion. By using high-purity aluminum as a raw material and adding Mn and Mg as alloying elements in predetermined amounts, unavoidable impurity elements The present inventors have found that the content of high-purity aluminum can be sufficiently reduced, the formation of an intermetallic compound which is a starting point of corrosion can be sufficiently suppressed, and the high corrosion resistance of high-purity aluminum can be maintained.
The high-purity aluminum used here is high-purity aluminum having a purity of 99.99% by mass or more (9 consecutive numbers from the beginning in the mass percent notation indicating purity, followed by N, which is an acronym for nine, and "4N". It is described as "-Al" and is sometimes called "four nine aluminum". Usually, this expression is used when there are three or more 9's).

Hereinafter, an aluminum alloy plate material according to the present invention and a mode for realizing the manufacturing method thereof will be described. First, each component and plate material constituting this aluminum alloy will be described, and then the production method will be described.

1. 1. Composition of Aluminum Alloy Plate The composition of the aluminum alloy plate according to the embodiment of the present invention will be described below.
(1) Mn
Mn is an element that improves the strength of the aluminum alloy without significantly reducing the corrosion resistance. Therefore, the Mn content is set to 0.1% by mass or more. The Mn content is preferably 0.3% by mass or more, more preferably 0.4% by mass or more. However, if the Mn content is too high, the intermetallic compounds increase, and these become the starting points of corrosion, and the corrosion easily progresses. Also, the conductivity is reduced. From the above viewpoint, the Mn content is set to 2.0% by mass or less. The Mn content is preferably 1.8% by mass or less, more preferably 1.5% by mass or less.

(2) Mg
Mg is an element that improves the strength of an aluminum alloy without significantly reducing the corrosion resistance. By containing Mg in a certain ratio or more with respect to Mn, the formation of an intermetallic compound containing Mn, which is the starting point of corrosion, can be suppressed, and the deterioration of the corrosion resistance of the aluminum alloy can be suppressed. Such an effect can be obtained if Mg is contained so as to satisfy the relationship of Mg content (mass%) / Mn content (mass%) ≥ 1/16. On the other hand, if the Mg content is too high, the base metal is likely to be corroded and the conductivity is lowered. Therefore, the Mg content is set to 1/16 times or more and 1.6% by mass or less of the Mn content on a mass basis. The Mg content is preferably 1.2% by mass or less, more preferably 0.8% by mass or less.

Further, by setting the total content of Mn and Mg to a predetermined value or more, the strength required for the heat exchanger fin material can be obtained. Therefore, the total content of Mn and Mg is set to 0.6% by mass or more. From the viewpoint of ensuring the moldability required for the heat exchanger fin material, the total content of Mn and Mg is preferably 2.5% by mass or less, more preferably 2.0% by mass or less. ..

FIG. 1 shows the relationship between the Mn content and the Mg content in the aluminum alloy constituting the plate material of the present invention described above. Further, FIG. 1 shows the compositions of Examples and Comparative Examples described later. The range surrounded by the thick line in the figure means the composition of the aluminum alloy described above. These five thick straight lines are the boundaries in the following equations (a) to (e), that is, straight lines connecting the left side and the right side with equality.
Mn content (mass%) ≥ 0.1 (a)
Mg content (mass%) ≤ 1.6 (b)
Mn content (mass%) ≤ 2.0 (c)
Mg content (mass%) / Mn content (mass%) ≧ 1/16 (d)
Mn content (mass%) + Mg content (mass%) ≥ 0.6 (e)

(3) Al
In addition to the above, the components of the aluminum alloy plate material are composed of Al and unavoidable impurity elements in the balance. The total content of unavoidable impurity elements is allowed up to 0.04% by mass, preferably 0.03% by mass or less, more preferably 0.02% by mass or less, further preferably 0.015% by mass or less, 0.01. It is even more preferably mass% or less. By setting the content of the unavoidable impurity element in such a range, it is possible to suppress the formation of an intermetallic compound which is a starting point of corrosion, and it is possible to improve the corrosion resistance of the aluminum alloy plate material.

An aluminum alloy plate material produced from aluminum having a purity of about 99% by mass usually contains about 1% by mass of unavoidable impurity elements, and such a high content of unavoidable impurity elements is the starting point of corrosion. This reduces the corrosion resistance of the aluminum alloy plate material.
Since the aluminum alloy plate material according to the present invention suppresses the amount of unavoidable impurity elements such as Fe low, the aluminum alloy constituting the plate material of the present invention usually has a purity of 99.99% by mass or more of high-purity aluminum (4N-Al). ) Is used as a raw material, and manganese and magnesium, which are alloying elements, are added to this. By using such high-purity aluminum as a raw material, the content of unavoidable impurity elements including Fe is 0.04% by mass or less, preferably 0.03% by mass or less, more preferably 0.02% by mass or less, and further. It can be preferably reduced to 0.015% by mass or less, and even more preferably to 0.01% by mass or less.
When a commercially available high-purity aluminum (4N-Al) is used as a raw material and manganese and magnesium, which are alloying elements, are added to prepare an aluminum alloy plate material according to the present invention, the content of unavoidable impurity elements is 0.02% by mass. The following aluminum alloy plate materials can be obtained.
An aluminum alloy plate material obtained by using high-purity aluminum having a higher purity, for example, 99.999% by mass or more (also referred to as "5N-Al" and sometimes referred to as "five nine aluminum") as a raw material. The amount of unavoidable impurity elements contained in the aluminum can be further reduced, and the corrosion resistance can be further enhanced.

As described above, the aluminum alloy constituting the plate material of the present invention requires the three components of Al, Mn, and Mg, and the other elements are basically unavoidable impurity elements, but these unavoidable impurity elements are consciously used. Needless to say, such aluminum alloys are not excluded as long as the provisions of the scope of patent claims are satisfied.

By using high-purity aluminum as a raw material in the aluminum alloy plate material according to the present invention, the total content of unavoidable impurity elements can be reduced and the corrosion resistance can be improved. When the content of Fe is particularly high in the aluminum alloy plate material, Al-Fe-based or Al-Mn-Fe-Si-based intermetallic compounds are likely to be generated, and these intermetallic compounds generally adversely affect the corrosion resistance. Is known for Therefore, it is preferable to reduce the content of Fe, which is a main unavoidable impurity element contained in the conventional aluminum alloy plate material. As will be described later, by reducing the Fe content, the corrosion resistance of the aluminum alloy plate material can be further enhanced.

(4) Fe
The content of Fe, which is a main unavoidable impurity element, is preferably 0.025% by mass or less, more preferably 0.02% by mass or less, and further preferably 0.015% by mass or less. , 0.003% by mass or less, more preferably. Within such a range, the formation of intermetallic compounds containing Al and Fe (Al-Fe type, Al-Mn-Fe-Si type, etc.) can be further suppressed, and the progress of corrosion in the aluminum alloy plate material can be suppressed. Can be further suppressed. Therefore, the Fe content is preferably 0.025% by mass or less, more preferably 0.02% by mass or less, further preferably 0.015% by mass or less, and 0.003% by mass or less. Is even more preferable. When a commercially available high-purity aluminum (4N-Al) is used as a raw material and manganese and magnesium, which are alloying elements, are added thereto to prepare an aluminum alloy according to the present invention, aluminum having an Fe content of 0.003% by mass or less is produced. An alloy plate material can be obtained. The lower limit of the Fe content in an aluminum alloy is zero, but in relation to the purification efficiency of aluminum, even when aluminum of the highest industrial purity is used as a raw material, it is at least about 0.1 mass ppm. include.
A conventional aluminum alloy plate material produced from aluminum having a low purity usually contains about 0.7% by mass of Fe.

(5) Other unavoidable impurity elements As described above, after setting the Fe content to 0.025% by mass or less, other unavoidable impurity elements Si, Cu, Ti, V, Cr, Ni, Zn and Ga The total content of the above is preferably 0.02% by mass or less, further 0.015% by mass or less, further 0.01% by mass or less, and particularly preferably 0.005% by mass or less.
When a commercially available high-purity aluminum (4N-Al) is used as a raw material and manganese and magnesium, which are alloying elements, are added to prepare an aluminum alloy according to the present invention, Si, Cu, and Ti, which are unavoidable impurity elements excluding Fe, are produced. , V, Cr, Ni, Zn and Ga can be obtained as an aluminum alloy plate material having a total content of 0.015% by mass or less.
Si is the main unavoidable impurity element next to Fe in aluminum, but from the viewpoint of further suppressing the formation of intermetallic compounds such as the above-mentioned Al-Mn-Fe-Si system, its content is set to 0. It is preferably 015% by mass or less, more preferably 0.01% by mass or less, and further preferably 0.005% by mass or less.

The amount of Mn, Mg and unavoidable impurity elements contained in the aluminum alloy plate can be quantified by, for example, glow discharge mass spectrometry (GDMS), solid emission spectroscopic analysis or ICP emission spectroscopic analysis.

2. 2. Solid solution ratio of Mn in the base material For the aluminum alloy plate material according to the embodiment of the present invention, the conditions of rolling and heat treatment are appropriately selected, and the solid solution state of Mn in the aluminum base material and Al- By controlling the precipitation state of the intermetallic compound such as Mn, in addition to the above-mentioned excellent corrosion resistance and strength, the conductivity can be further improved, and the moldability can also be improved.

Specifically, for an aluminum alloy plate material satisfying the above-mentioned composition, the Mn solid solution rate in the base material is 40% or less, which is calculated on the assumption that Mg is completely dissolved in the base material. It is preferable to have. Within such a range, the conductivity and moldability of the aluminum alloy plate material can be further improved.

The mechanism by which the conductivity and moldability of the aluminum alloy plate material can be further improved by reducing the Mn solid solution ratio in aluminum to 40% or less is as follows.

Mn in the aluminum alloy plate material exists in both a state of being solid-solved in aluminum as a base material and a state of being precipitated as an intermetallic compound. The greater the amount of precipitates as intermetallic compounds, the finer the crystal grains when the final annealing step described later was performed, and as a result, the resulting aluminum alloy plate material was further improved while maintaining high strength. It can have conductivity and moldability. Assuming that all of Mg is solid-solved in the base metal, the solid solution rate of Mn in the base metal calculated using the calculation formulas (1) to (3) described later is 40% or less. For example, the effect of grain refinement after the final annealing step can be easily obtained, and the conductivity and moldability can be further improved while maintaining the above-mentioned high strength. The solid solution ratio of Mn in the base metal is more preferably 30% or less.

Further, by appropriately selecting the conditions of rolling and heat treatment and controlling the solid solution state of Mn in the base material aluminum and the precipitation state as a compound such as Al-Mn, the crystal grains of the aluminum alloy plate material are controlled. Can be made finer, and the average crystal grain size can be reduced. The average crystal grain size of the aluminum alloy plate is preferably about 100 μm or less. When the average crystal grain size is in such a range, the conductivity and moldability of the aluminum alloy plate material can be further improved. The average crystal grain size is the average value of the crystal grain length in the direction perpendicular to the rolling direction and the crystal grain length in the direction parallel to the rolling direction, which is measured by etching the cross section of the alloy plate with hydrofluoric acid. Say.

It is generally known from the phase diagram that Mg is easily dissolved in Al. For example, from the Al-Mn-Mg ternary phase diagram, it can be seen that when the amount of Mn is up to 2% by mass specified in the present invention, up to about 2% by mass of Mg is solid-solved in Al. Therefore, the above assumption that the entire amount of Mg is solid-solved in the base metal is considered to be valid as long as the upper limit of the amount of Mg specified in the present invention is up to 1.6% by mass.

-Method of calculating the solid solution rate of Mn in the base material About the method of obtaining the solid solution rate of Mn in the base material from the conductivity of the plate material, assuming that Mg is completely dissolved in the base material. explain. As one of the units of conductivity, there is "% IACS", and this unit is adopted in this specification. IACS stands for International Annealed Copper Standard, which the conductivity of internationally adopted have been annealed standard soft copper (volume resistivity = 1.7241 × 10 ^-2 μΩm) and 100% IACS. Since conductivity is proportional to the reciprocal of electrical resistance, for example if 50% IACS, the volume resistivity (hereinafter, also referred to as "electrical resistance" or simply "resistance") is, 1.7241 × 10 ^{- It} can be converted as ² μΩm × 100/50 = 3.4482 × 10 ^-2 μΩm = 3.4482 × 10 ^-8 Ωm. Further, as described above, 100% conductivity IACS corresponds to an electric resistance value of 1.7241 × 10 ^-2 μΩm = 1.7241 × 10 ^-8 Ωm, but here, the number of significant figures is 3 digits and the conductivity is 100% IACS. The calculation formula is shown assuming that the electric resistance value corresponds to 1.72 × 10 ^-8 Ωm.

First, the increase in electrical resistance due to the addition of Mn and Mg to aluminum is calculated by the following equation (1). Next, of the obtained increase in electrical resistance value, the increase due to the addition of Mn (referred to as “Mn resistance contribution”) is calculated by the following formula (2). Finally, the solid solution ratio of the added Mn to the base material (referred to as "Mn solid solution ratio") is calculated by the following formula (3). For example, when the conductivity of an aluminum alloy plate produced by adding 1.2% by mass of Mn and 0.1% by mass of Mg to 4N-Al is 40% IACS, the solid solution rate of Mn is 40.5%. Become.

The meanings of the above equations (1) to (3) and the basis for calculating the numerical values appearing therein will be described.

The formula (1) means the amount of increase in the electric resistance value due to the addition of Mn and Mg to Al. In the first item on the right side, "1.72 x 10 ^-8 x 100 / (conductivity of alloy plate material (% IACS))", the measured conductivity (% IACS) of the alloy plate material is converted to the electrical resistance value (Ωm). In the second term, "2.64 x 10 ^-8 " is a value obtained by actually measuring the electric resistance value (Ωm) of pure aluminum (4N-Al).

The formula (2) means the amount of increase in the electric resistance value due to Mn among the added Mn and Mg, and the resistance due to Mg described below from the total increase in the electric resistance value calculated by the formula (1). The value is obtained by subtracting the value increase. The second term on the right side means the increase in resistance value due to Mg as described above, and the “specific resistance contribution coefficient of Mg” = 5.5 × 10 ^-9 Ωm / mass% that appears there is calculated as follows. In Table 2 on page 49 of Non-Patent Document 1 (Sumitomo Chemical Technical Journal, Tokushu 1975-I) mentioned above, the resistivity contribution per 1 atom% of the solid solution amount of Mg in aluminum is 0.5 × 10. ^-6 It is stated that it is Ωcm / atomic%. The relationship between the atomic% and mass% of the additive element X in aluminum is as shown in FIG. 2. When the additive element X is Mg, as shown in Calculation 1 of FIG. 2, the relationship of Mg 1 atomic% = 0.9019 mass%. It is in. Therefore, the above-mentioned specific resistance contribution of solid solution Mg 0.5 × 10 ^-6 Ωcm / atomic% is converted into “Ωm / mass%”.
0.5 × 10 ^-6 Ω cm / atomic% = 0.5 × 10 ^-6 Ω × 10 ^-2 m / 0.9019 mass%
= 5.5 × 10 ^-9 Ωm / mass%
Got This is the resistivity contribution coefficient of Mg that appears in the second term on the right side of the above equation (2).

In the formula (3), the Mn resistance contribution calculated by the formula (2), that is, the amount of increase in the electric resistance value contributed by Mn in the actual alloy plate material is used as a molecule, and the total amount of Mn is solid-solved in aluminum. The ratio of the amount of increase in electrical resistance value as the denominator when it is assumed that the value is increased by 100 to make it in%. The increase in electrical resistance (molecule) contributed by Mn in the actual alloy plate is smaller than the increase in electrical resistance (denominator) when it is assumed that Mn is completely dissolved in aluminum. Since it is caused by the fact that Mn is precipitated without solid solution in the actual alloy plate material, this ratio was regarded as the Mn solid solution ratio. If the amount of increase in electrical resistance (numerator) contributed by Mn in an actual alloy plate material is equal to the denominator, the Mn solid solution rate is 100%.

The “resistive resistivity contribution coefficient of Mn in the solid solution state” = 3.3 × 10 ^-8 Ωm / mass% appearing in the formula (3) was calculated as follows. In Table 2 on page 49 of Non-Patent Document 1 (Sumitomo Chemical Technical Journal, Tokushu 1975-I) mentioned above, the resistivity contribution per 1 atomic percent of the solid solution amount of Mn in aluminum is 6.7 ×. It is stated that it is 10 ^-6 Ωcm / atomic%. Then, as shown in Calculation 2 of FIG. 2, since there is a relationship of Mn 1 atomic% = 2.0154 mass%, the above-mentioned specific resistance contribution of solid solution Mn is 6.7 × 10 ^-6 Ωcm / atomic% as “Ωm /”. Converted to "mass%" unit,
6.7 x 10 ^-6 Ω cm / atomic% = 6.7 x 10 ^-6 Ω x 10 ^-2 m / 2.0154 mass%
= 3.3 × 10 ^-8 Ωm / mass%
Got This is the resistivity contribution coefficient of Mn appearing in the above formula (3) in the solid solution state.

In Table 25 on page 344 of Non-Patent Document 2 (“Basics of Aluminum Materials and Industrial Technology”) described above, the increase in average resistivity in the precipitated state of Mn affecting the electrical resistance of aluminum is 0.34 μΩcm / mass%. It is described as (= 3.4 × 10 ^-9 Ωm / mass%), which is an order of magnitude smaller than the above-mentioned resistivity contribution coefficient 3.3 × 10 ^-8 Ωm / mass% in the solid-dissolved state. There is. Therefore, the amount of increase in the electric resistance value due to Mn is substantially brought about by Mn in the solid solution state, and the influence of Mn in the precipitated state is considered to be negligible, and the above calculation is performed.

The solid solubility of Mn in the base metal calculated from the conductivity has been described above, but as shown in the formula (1), after converting the conductivity into an electrical resistivity value (also referred to as an electrical resistivity value). Since it is calculated, the meaning of "the solid solubility of Mn in the base metal calculated from the electrical resistivity value" has the same meaning.

3. 3. Plate thickness of aluminum alloy plate material The plate thickness of the aluminum alloy plate material can be 0.1 mm or more and 5 mm or less. If the plate thickness is within such a range, it can be applied as a fin material for a heat exchanger or the like. The smaller the plate thickness, the more the weight of the plate material itself is reduced and the size of various products applied to the heat exchanger is reduced. Therefore, the plate thickness is preferably 2 mm or less, more preferably 1 mm or less. Further, if the plate thickness is 0.1 mm or more, the strength can be maintained, but if necessary, it can be 0.2 mm or more, and further 0.25 mm or more.

4. Manufacturing Method of Aluminum Alloy Plate Material The manufacturing method of the aluminum alloy plate material according to the present invention includes the rolling material manufacturing step, the rolling step and the final annealing step described below, and it is preferable to perform an intermediate annealing step in the middle of the rolling step. Hereinafter, each of these steps will be described.

(Rolling material manufacturing process)
The rolling material manufacturing process is a process of melting and casting an aluminum alloy to produce an aluminum alloy ingot. In the rolling material manufacturing step, an ingot having a predetermined shape is manufactured from a molten metal in which an aluminum alloy having the above-mentioned chemical components is melted. The method for melting and casting the aluminum alloy is not particularly limited, and a conventionally known method may be used. Further, a step of heat-treating the rolled material (homogenization heat treatment step) may be included.
Here, it is preferable to use high-purity aluminum having a purity of 99.99% by mass or more as a raw material for the aluminum alloy. The method for obtaining such high-purity aluminum is not particularly limited, but for example, the document "High-purity aluminum" (Harumi Asakusa et al., Sumitomo Chemical Technical Magazine, Sumitomo Chemical Co., Ltd., 1988, 1988-II, P.69-86 ), It is preferable to obtain by either the three-layer electrolysis method or the segregation method. With such a method, high-purity aluminum such as 4N-Al can be stably obtained, and the finally obtained aluminum alloy plate material can be efficiently produced.
In preparing an aluminum alloy having the above-mentioned chemical components, an aluminum-manganese mother alloy may be used as a manganese source, or an aluminum-magnesium mother alloy may be used as a magnesium source, as long as the amount of unavoidable impurity elements does not exceed the specified value. It can also be used.

(Rolling process)
The rolling step is a step of rolling the rolled material with a rolling processing rate of 90% or more. The rolling processing ratio referred to here is the value obtained by subtracting the thickness of the final plate obtained by rolling from the thickness of the rolled material (that is, the thickness before rolling) (that is, the thickness reduced by rolling). Percentage of the value divided by the thickness of the material,
Rolling rate (%) = [(Thickness before rolling-Thickness after rolling) / Thickness before rolling] x 100
Is calculated by. For example, if a rolled material having a thickness of 10 mm is rolled into a plate material having a thickness of 1 mm, the rolling processing rate is 90%.

It is preferable that the rolled material is rolled a plurality of times to obtain the final plate thickness. By setting the rolling process ratio to 90% or more, coarsening of recrystallized grains after final annealing can be suppressed, leading to suppression of deterioration of moldability. Therefore, the rolling ratio is preferably 90% or more. Since the higher the rolling rate is, the more preferable it is, no upper limit is set. Further, the temperature at the time of rolling is not specified in particular.

The rolling method may be either cold rolling or hot rolling. Hot rolling and cold rolling can be combined. For example, among the rolling processes performed a plurality of times, the initial stage may be hot rolling and the latter half may be cold rolling.

(Intermediate annealing process)
The intermediate annealing step is a step of holding at 500 ° C. or higher for 5 hours or longer in the middle of the rolling step. In the method for producing an aluminum alloy sheet metal according to the present invention, by performing such an intermediate annealing step in the middle of the rolling step, the amount of Mn precipitated in the state of an intermetallic compound increases, and recrystallized grains after final annealing are produced. It can be miniaturized. As a result, an aluminum alloy plate material having excellent conductivity and moldability in addition to strength and corrosion resistance can be obtained. By setting the temperature of the intermediate annealing to 500 ° C. or higher, the recrystallized grains after the final annealing can be made finer. Further, by setting the annealing time to 5 hours or more, the recrystallized grains after the final annealing can be made finer. Therefore, it is desirable to hold the intermediate annealing step at 500 ° C. or higher for 5 hours or longer. The temperature of the intermediate annealing may be a temperature at which the aluminum alloy does not melt, but is preferably 600 ° C. or lower from the viewpoint of cost. Even if the intermediate annealing time is lengthened, there is no problem in characteristics, but from the viewpoint of cost, up to about 20 hours is sufficient.

When the rolling process ratio after the intermediate annealing step is 60% or more, it is easy to suppress the coarsening of recrystallized grains after the final annealing. Therefore, the rolling process ratio after the intermediate annealing step is preferably 60% or more, and more preferably 80% or more. The rolling processing ratio after the intermediate annealing step here is the value obtained by subtracting the thickness of the final plate material obtained by the subsequent rolling from the thickness of the plate material when the rolling process is restarted after the intermediate annealing is completed. It means the percentage of the value divided by the thickness of the plate material at the time of resumption, that is, the rate of decrease in thickness due to rolling after intermediate annealing.

The rolling processing rate from the rolled material to the intermediate annealing, that is, the reduction rate of the thickness by rolling until the intermediate annealing is started, is 20% or more from the viewpoint of effectively exhibiting the effect of the intermediate annealing, and further. Is preferably 30% or more.

Further, by performing such intermediate annealing, the crystal grain size of the aluminum alloy plate material obtained through the subsequent rerolling step and final annealing step can be reduced to about 50 μm on average. As a result, it is possible to obtain an aluminum alloy plate material having excellent conductivity and moldability in addition to corrosion resistance and strength.

(Final annealing process)
The final annealing step is a step of performing finish annealing at a temperature of 200 ° C. or higher and 450 ° C. or lower for 1 hour or more and 10 hours or less after the rolling step. By setting the final annealing temperature to 200 ° C. or higher, a sufficient structure recovery effect can be obtained, and an aluminum alloy plate material having good strength, conductivity, moldability and corrosion resistance can be obtained. On the other hand, by setting the temperature to 450 ° C. or lower, coarsening of recrystallized grains during annealing can be suppressed, and an aluminum alloy plate material having good strength, conductivity, moldability and corrosion resistance can be obtained. Therefore, the annealing temperature is preferably 200 ° C. or higher and 450 ° C. or lower. Further, by setting the annealing time to 1 hour or more, a sufficient structure recovery effect can be obtained, and an aluminum alloy plate material having good moldability can be obtained. Even if the annealing time is lengthened, there is no problem in characteristics, but from the viewpoint of cost, up to about 10 hours is sufficient. Therefore, the annealing time is preferably 1 hour or more and 10 hours or less.

The aluminum alloy plate material thus obtained is excellent in strength, conductivity and corrosion resistance, and can be used for various applications such as a structure of a portion in contact with a highly corrosive fluid. The aluminum alloy plate material according to the present invention can be particularly preferably used as a fin material for a heat exchanger.

(Fin material molding)
A molding method when the aluminum alloy plate material according to the present invention is used as a fin material will be described. By press-molding the aluminum alloy plate material obtained through the above-mentioned steps, a fin material for a heat exchanger can be produced. Before press-molding the aluminum alloy plate material, at least one surface of the aluminum alloy plate material may be coated with a resin or the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the Examples.

(Examples 1 to 11, Comparative Examples 1 to 9)
The aluminum alloy having the composition shown in Table 1 (measured by solid-state emission spectroscopic analysis) was melted and cast into an ingot. The obtained ingot was subjected to a homogenizing heat treatment of holding at 430 ° C. for 5 hours and then at 580 ° C. for 4 hours, and then face-cut, and the plate shown in the column of "rolled material" in Table 1 was subjected to. A thick rolled material was used. This rolled material was cold-rolled to obtain a cold-rolled plate having a plate thickness of 0.5 mm. In some examples and comparative examples, cold rolling is temporarily interrupted at the plate thickness shown in the column of "intermediate annealing" in Table 1, and the obtained intermediate rolled material is held at 560 ° C. for 11 hours. Annealed. After all the rolling was completed, the cold-rolled plate was subjected to final annealing at the temperature shown in the column of "final annealing" in Table 1 for 7 hours to obtain a test plate material, which was used for evaluation. The relationship between the Mg content and the Mn content of the samples of Examples 1 to 11 and Comparative Examples 4 to 9 in which the total content of the unavoidable impurity elements is 0.04% by mass or less is as shown in FIG. In FIG. 1, a black circle indicates an embodiment, and an X character indicates a comparative example. In addition, the black circle and the reference numeral attached to the X character represent the numbers of Examples and Comparative Examples.

(Corrosion resistance)
The erosion rate of the alloy plate produced above was measured as an index of corrosion resistance as follows. First, it was immersed in a 3.5 mass% NaCl aqueous solution at 30 ° C. adjusted to pH 3 with acetic acid for 72 hours. After the test, the corrosion weight loss after removing the corrosion products was measured, and the erosion rate was determined from the value assuming uniform corrosion over the entire surface. In the above evaluation, those having an erosion rate of 0.1 mm / year or less were evaluated as good (◯), and those having an erosion rate of more than 0.1 mm / year were evaluated as poor (x), and the results are summarized in Table 2.

(Conductivity)
With respect to the alloy plate material produced above, the conductivity was measured at a temperature of 293 K (20 ° C.) as an index of conductivity. Regarding the measurement results, those having a conductivity of 35% IACS or more were evaluated as good (◯), and those having a conductivity of less than 35% IACS were evaluated as defective (x), and the results are summarized in Table 2. Further, from each conductivity, according to the above formulas (1) to (3), the solid solution ratio of Mn in the base material when it is assumed that all of Mg is solid-solved in the base material (hereinafter, simply (Displayed as "Mn solid solution rate") was calculated, and the value is also shown in Table 2. In Comparative Example 4, as shown in Table 1, the Mn content is zero and the denominator in the above formula (3) is zero, so the Mn solid solution ratio is not calculated.

(Strength)
The Vickers hardness (HV0.05) of the alloy plate produced above was measured using a Micro Vickers hardness tester as an index of strength. The Vickers hardness is a value measured according to JIS Z2244: 2009 "Vickers hardness test-test method", and remains on the surface after a regular square pyramid diamond indenter is pushed into the surface of the test piece to release the test force. Calculated from the diagonal length of the depression. In this standard, it is stipulated that the hardness symbol is changed according to the test force, and here, the Micro Vickers hardness HV0.05 when the test force is 0.05 kgf (= 0.4903 N) is adopted. Regarding the measurement results, those with a Vickers hardness of 25 or more were regarded as good (◯), those with a Vickers hardness of less than 25 were regarded as poor (x), and the results are summarized in Table 2.

As is clear from Table 2, the aluminum alloy plates of Examples 1 to 11 in which the total content of unavoidable impurity elements and the relationship between the Mn content and the Mg content satisfy the provisions of the present invention are all corrosion resistant and conductive. It was a material with excellent properties and strength.

In Examples 1 and 2, intermediate annealing was not performed and the amount of Mn was as small as 0.4% by mass, so that the solid solution rate of Mn was large. It is considered that if intermediate annealing is performed with this composition, the Mn solid solution ratio of the finally obtained plate material becomes small, the crystal grains become finer, and the moldability and conductivity are improved. Although intermediate annealing was not performed in Example 3, since the amount of Mn in this example was as large as 1.5% by mass, the solid solution rate of Mn was also correspondingly small. It is considered that if intermediate annealing is performed with this composition, the Mn solid solution ratio of the finally obtained plate material becomes smaller, the crystal grains become finer, and the moldability and conductivity are further improved.

As one of the indexes for evaluating the moldability, there is an Eriksen value measured according to JIS Z2247: 2006 “Eriksen test method”. The plate materials of Examples 4 to 11 which were intermediate-annealed during the rolling process gave a high Eriksen value and were excellent in moldability.

The alloy plate material of Comparative Example 1 had good conductivity and strength, but its corrosion resistance was lowered. This is because the total content of unavoidable impurity elements exceeds 0.04% by mass, and the Mg content is less than 1/16 times the Mn content.
In the alloy plate material of Comparative Example 2, the relationship between the Mn content and the Mg content satisfied the provisions of the present invention, but the corrosion resistance was lowered. This is because the total content of unavoidable impurity elements exceeded 0.04% by mass.
In Comparative Example 3, the relationship between the Mn content and the Mg content satisfied the provisions of the present invention, but the corrosion resistance and conductivity were lowered. This is because the total content of the unavoidable impurity elements exceeded 0.04% by mass, and the solid solution rate of Mn exceeded 40%.
The alloy plates of Comparative Examples 4 and 5 had good corrosion resistance and conductivity, but their strength was reduced. This is because the total content of Mn and Mg was less than 0.6% by mass.
The alloy plate material of Comparative Example 6 had good corrosion resistance and strength, but its conductivity was lowered. This is because the Mg content was excessive.
The alloy plates of Comparative Examples 7 to 9 had good conductivity and strength, but their corrosion resistance was lowered. This is because the Mg content was less than 1/16 times the Mn content.

Claims (9)

The Mn content is 0.1% by mass or more and 2.0% by mass or less.
The Mg content is 1/16 times or more and 1.6% by mass or less of the Mn content on a mass basis.
The rest consists of Al and unavoidable impurity elements
The total content of Mn and Mg is 0.6% by mass or more,
An aluminum alloy plate material having a total content of the unavoidable impurity elements of 0.04% by mass or less. The aluminum alloy plate material according to claim 1, wherein the total content of the unavoidable impurity elements is 0.02% by mass or less. Fe content is 0.025% by mass or less,
The aluminum alloy plate material according to claim 1 or 2, wherein the total content of Si, Cu, Ti, V, Cr, Ni, Zn and Ga is 0.02% by mass or less. The Fe content is 0.003% by mass or less,
The aluminum alloy plate material according to claim 3, wherein the total content of Si, Cu, Ti, V, Cr, Ni, Zn and Ga is 0.015% by mass or less. Any of claims 1 to 4, wherein the solid solution rate of Mn in the base material calculated from the conductivity of the plate material is 40% or less, assuming that all of Mg is solid-solved in the base material. The aluminum alloy plate material described in. A fin material for a heat exchanger made of the aluminum alloy plate material according to any one of claims 1 to 5. The Mn content is 0.1% by mass or more and 2.0% by mass or less, the Mg content is 1/16 times or more and 1.6% by mass or less of the Mn content on a mass basis, and the balance is Al and A step of producing a material for rolling an aluminum alloy, which is composed of unavoidable impurity elements and has a total content of Mn and Mg of 0.6% by mass or more and a total content of the unavoidable impurity elements of 0.04% by mass or less. ,
The rolling process for rolling the aluminum alloy rolling material and
After the rolling step, a final annealing step of holding at a temperature of 200 ° C. or higher and 450 ° C. or lower for 1 hour or longer, and
A method for manufacturing an aluminum alloy plate, including. The method for producing an aluminum alloy plate material according to claim 7, wherein the total content of the unavoidable impurity elements is 0.02% by mass or less. The method for producing an aluminum alloy plate material according to claim 7 or 8, further comprising an intermediate annealing step of holding at 500 ° C. or higher for 5 hours or longer in the middle of the rolling step.

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