JP2011137201A - Aluminum alloy sheet for heat insulator and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a heat insulator which has excellent strength and has excellent emboss formability and press formability as well even if a raw material blended with brazing sheet scrap is used, and to provide a method for producing the same. <P>SOLUTION: The aluminum alloy sheet for a heat insulator is composed of an aluminum alloy comprising, by mass, 0.4 to 2.0 Si, 0.2 to 0.6 Fe, 0.1 to 0.7% Cu, 0.5 to 1.5% Mn, 0.5 to 2.0% Mg and 0.05 to 1.0% Zn, and the balance Al with inevitable impurities. The aluminum alloy sheet has a recrystallized structure over the whole cross-section of the sheet thickness, and also has a recrystallized grain diameter of ≤50 μm and an electric conductivity of 43.0 to 49.5% IACS. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an aluminum alloy plate used for a heat insulator and a method for producing the same.

  A heat insulator is a general term for a cover (shielding material) for heat insulation or heat insulation provided in catalytic converters, exhaust guide parts around mufflers, transmission parts, engine mounts, etc. of transport equipment such as automobiles. It is. For example, as described in Patent Documents 1 and 2, an aluminum alloy plate (especially JIS 3004 alloy plate: Al—Mn—Mg alloy) is often used for this heat insulator.

  In recent years, for the purpose of reducing environmental impact, it has been studied to use aluminum alloy mixed with brazing sheet waste as a raw material for an aluminum alloy plate. At this time, various problems occur with changes in the chemical composition of the aluminum alloy. Here, the brazing sheet waste refers to, for example, a scrap material of a brazing sheet in which a side material is clad on one side or both sides of a core material used in a heat exchanger or a food can. And as a brazing sheet used for a heat exchanger, a core material made of 3000 series (Al-Mn series aluminum alloy), a side material for brazing material made of 4000 series (Al-Si series aluminum alloy), 7000 series A clad material clad with a side material for a sacrificial material made of (Al—Zn—Mg-based aluminum alloy), or 1000 series (pure aluminum) between the core material of the clad material and the side material (for the sacrificial material) The clad material which clad the side material for intermediate materials which consists of this is mentioned. Moreover, as a brazing sheet used for food cans, a core material made of 3000 series (Al-Mn series aluminum alloy) or 5000 series (Al-Mg series aluminum alloy) is used with a side material made of 1000 series (pure aluminum). The clad clad material is mentioned.

For example, in a heat insulator, a high material strength (for example, 160 MPa or more) is required to prevent breakage at a bolt fastening portion, but the material strength is reduced when the scrap mixing ratio is increased. There is a problem of doing. The cause of the strength decrease is that the amount of Si contained in the aluminum alloy increases with mixing of the scrap, and Si and Mg, Cu, etc. contained in the aluminum alloy are combined to form Mg ₂ Si, Al—Mg—Si. This is probably because an intermetallic compound such as a -Cu compound is formed, and Mg and Si are consumed to form this intermetallic compound, resulting in a decrease in the amount of solid solution Mg and the amount of solid solution Si that contribute to strength improvement. And as a means to compensate for the strength reduction, there is a solution such as increasing the thickness of the product, but an increase in mass and an increase in cost are inevitable.

  Moreover, in a heat insulator, in order to improve heat dissipation (heat-shielding property) and component rigidity, the aluminum alloy plate is often subjected to molding called embossing. Embossing is a molding method in which a plate material is pressed or roll-molded with a mold having a concavo-convex pattern opposite thereto, and a concavo-convex shape continuous to the plate material is formed by local stretch molding. And in order to maintain and improve high rigidity, it is required to form the uneven shape densely and highly. Due to the recent weight reduction of vehicle bodies and the increasing demand for cost reduction, it is required to reduce the thickness (0.5 mm or less) of the aluminum alloy plate constituting the heat insulator. There is a problem that an embossed shape (uneven shape) cannot be obtained. This promotes the generation of cracks when the aluminum alloy plate is press-molded into a product shape (heat insulator) after embossing, leading to a problem that it is difficult to obtain a desired final product.

The following techniques have been proposed as means for solving these problems.
First, an aluminum alloy plate for heat insulator as a technique for solving the strength reduction caused by the decrease in the amount of solid solution Mg and the amount of solid solution Si when using a raw material in which brazing sheet waste is mixed with an Al-Mn-Mg alloy. However, there is technology related to aluminum alloy plates for can bodies. For example, in Patent Document 3, the aluminum alloy ingot is subjected to a homogenization heat treatment at 600 to 640 ° C. for 1 hour or more to increase the solid solution amount of Mg and Si, and the processing heat generation is used in cold rolling. Thus, a technique has been proposed in which the cold rolling is finished so that the material temperature becomes 120 ° C. or more and the material is cooled at 10 ° C./hr or less.

In Patent Document 4, the coil wound after hot finish rolling is cooled with a fan (cooled at a cooling rate of 10 ° C./hr or more), so that the diameter of the aluminum alloy sheet after hot finish rolling is 0.1. A technique for reducing the number of ˜1 μm Mg ₂ Si precipitates to 10,000 / mm ² or less has been proposed.

  Further, as a technique for preventing cracking in embossing, there is a technique related to an aluminum alloy sheet for embossing that is used for building materials such as siding materials, although it is not an aluminum alloy sheet for heat insulators. For example, in Patent Document 5, Mg: 1.2 to 2.1% by mass, Si: 0.3% by mass or less of an aluminum alloy plate (soft material), Patent Document 6 has Mg: 1.3 to 2.3%. An aluminum plate (soft material) containing mass% and Si: 0.3 mass% or less has been proposed.

JP 2000-136720 A JP 2002-38944 A Japanese Patent Laid-Open No. 06-2090 Japanese Patent No. 4060460 JP 2001-254137 A JP 2002-212661 A

However, the aluminum alloy plates of Patent Documents 3 and 4 are related to can body applications, and generally, a hard material (JIS-specified H material) that has been cold-rolled is used. Since the aluminum alloy plate used for heat insulators is embossed as described above, a soft material (JIS-standard O material) that has been annealed after cold rolling is generally used. . Therefore, the techniques for improving the strength of Patent Documents 3 and 4 cannot prevent the strength of the aluminum alloy plate for heat insulator made of a soft material from being reduced. In particular, when a raw material blended with brazing sheet waste is used, it is difficult to prevent strength reduction.

  In addition, the aluminum alloy plates of Patent Documents 5 and 6 have a very low Si addition amount of 0.3% by mass or less, so that the brazing sheet scrap mixing ratio in the raw material is low and the recyclability is low.

  Accordingly, the present invention was devised to solve the above-described problem, and even if a raw material blended with brazing sheet waste is used, the heat insulator has excellent strength and is excellent in embossing and press forming properties. It is an object of the present invention to provide an aluminum alloy plate for use and a method for producing the same.

  In order to solve the above-described problems, the aluminum alloy plate for heat insulator of the present invention has Si: 0.4 to 2.0 mass%, Fe: 0.2 to 0.6 mass%, Cu: 0.1 to 0. 7% by mass, Mn: 0.5-1.5% by mass, Mg: 0.5-2.0% by mass, Zn: 0.05-1.0% by mass, the balance being Al and inevitable impurities An aluminum alloy plate made of an aluminum alloy, wherein the aluminum alloy plate has a recrystallized structure over the entire cross section of the plate thickness, and has a recrystallized grain size of 50 μm or less, and conductivity: 43.0 to 49 .5% IACS.

  According to the above configuration, it contains a predetermined amount of Si, Fe, Cu, Mn, Mg and Zn and has a predetermined recrystallized structure, recrystallized grain size, and conductivity, thereby providing strength, embossability and press molding. Improves. In particular, by containing a predetermined amount of Si and Mg and having a predetermined conductivity, a sufficient solid solution Mg amount and solid solution Si amount can be secured, and strength, embossing formability and press formability are improved. Also, by containing Si: 0.4% by mass or more, Fe: 0.2% by mass or more and Zn: 0.05% by mass or more, the blending ratio of brazing sheet waste in the raw material can be increased, and the recyclability is improved. To do.

  The aluminum alloy plate for a heat insulator according to the present invention is characterized in that the aluminum alloy further contains at least one of Cr: 0.15% by mass or less and Zr: 0.15% by mass or less.

  According to the above-described configuration, by containing at least one of a predetermined amount of Cr and Zr, dispersed particles (dispersed phase) are generated during the homogenization heat treatment in manufacturing the aluminum alloy plate, and the recrystallized grains are refined. Embossability and press formability are improved.

  In the aluminum alloy plate for heat insulator of the present invention, the aluminum alloy plate has a total amount of solid solution Mg amount and solid solution Si amount of 0.8 to 1.5% by mass, and the solid solution Mg amount and solid solution Mg amount. The amount of dissolved Si is the amount of Mg and Si contained in a solution obtained by a residue extraction method using hot phenol and a precipitate having a particle size of 0.1 μm or less.

  According to the said structure, when the total amount of solid solution Mg amount and solid solution Si amount is a predetermined amount, intensity | strength improves and the outstanding embossing moldability and press moldability are obtained.

  The aluminum alloy plate for a heat insulator according to the present invention is characterized in that the aluminum alloy plate is provided with a concavo-convex shape continuous on its surface by embossing.

  According to the said structure, by providing the continuous uneven | corrugated shape, the surface area of an aluminum alloy plate increases and heat dissipation (heat-shielding property) improves.

  The method for producing an aluminum alloy plate for a heat insulator according to the present invention includes a casting process in which the aluminum alloy is melted and an ingot is produced from the molten metal by DC casting, and a homogenized heat treatment at 450 to 600 ° C. is performed on the ingot. A homogenization heat treatment step, a hot rolling step of hot rolling the ingot subjected to the homogenization heat treatment to produce a hot rolled sheet, and cold rolling the hot rolled sheet at a cold rolling rate of 70% or more. Including a cold rolling process for producing a cold-rolled sheet and an annealing process in which the cold-rolled sheet is subjected to continuous annealing within 5 minutes within a range of 400 to 500 ° C. and cooled at a cooling rate of 10 ° C./second or more. Features.

  According to the above procedure, by performing the homogenization heat treatment step, the cold rolling step, and the annealing step under predetermined conditions, the total amount of solid solution Mg amount and solid solution Si amount becomes sufficient, and the conductivity is within a predetermined range. Become. Moreover, it has a recrystallized structure over the entire cross section of the thickness of the aluminum alloy plate, and the recrystallized grain size also falls within a predetermined range. As a result, the strength, embossing formability and press formability of the manufactured aluminum alloy plate are improved.

According to the aluminum alloy plate for heat insulator of the present invention, even if a raw material blended with brazing sheet waste is used, it has excellent strength and is excellent in embossing formability and press formability.
According to the method for producing an aluminum alloy plate for a heat insulator of the present invention, an aluminum alloy plate having excellent strength and excellent embossing and press forming properties can be obtained even when a raw material blended with brazing sheet waste is used. Manufactured.

It is a figure which shows the uneven | corrugated shape of the aluminum alloy plate for heat insulators which concerns on this invention. It is a front view of a square tube drawing die used for evaluating the press formability of an aluminum alloy plate. It is a crystal structure of an aluminum alloy plate, (a) is a recrystallized structure, (b) is an optical micrograph showing an unrecrystallized structure.

<Aluminum alloy plate for heat insulator>
The aluminum alloy plate for heat insulators according to the present invention will be described.
Aluminum alloy plate for heat insulator is Si: 0.4-2.0 mass%, Fe: 0.2-0.6 mass%, Cu: 0.1-0.7 mass%, Mn: 0.5- Aluminum alloy plate composed of an aluminum alloy containing 1.5% by mass, Mg: 0.5-2.0% by mass, Zn: 0.05-1.0% by mass, the balance being Al and inevitable impurities The aluminum alloy plate has a recrystallized structure over the entire cross section of the plate thickness, has a recrystallized grain size of 50 μm or less, and an electrical conductivity of 43.0 to 49.5% IACS. To do.

First, the reason for limiting the numerical value of each component of the aluminum alloy will be described.
(Si: 0.4-2.0 mass%)
Si is blended into the raw material by brazing sheet scraps, and is an element that generates an Al—Fe—Si-based or Mg ₂ Si-based intermetallic compound during casting and homogenization heat treatment. If the Si amount is less than 0.4% by mass, the amount of brazing sheet waste mixed with the raw material is reduced, and the recyclability is lowered. When the amount of Si exceeds 2.0% by mass, a coarse intermetallic compound is generated, which becomes a starting point of cracking in the embossing and subsequent press forming of the aluminum alloy plate, and the embossability and press formability are deteriorated.

(Fe: 0.2-0.6% by mass)
Fe is contained in brazing sheet scraps and raw materials, and crystallized substances such as Al ₇ Cu ₂ Fe, Al ₁₂ (Fe, Mn) ₃ Cu ₂ , and (Fe, Mn) Al ₆ during casting and homogenization heat treatment Is an element that generates If the Fe amount is less than 0.2% by mass, the amount of brazing sheet waste mixed with the raw material is reduced, and the recyclability is lowered. When the amount of Fe exceeds 0.6% by mass, a coarse crystallized product is generated, which becomes a starting point of cracking in the embossing and subsequent press forming of the aluminum alloy plate, and the embossability and press formability are lowered.

(Cu: 0.1 to 0.7% by mass)
Cu is an important element contributing to the strength, and is contained in the brazing sheet waste and the raw material, and improves the embossing formability and press formability. If the amount of Cu is less than 0.1% by mass, the strength decreases. Moreover, the brazing sheet waste mix | blended with a raw material decreases, and recyclability falls. When the amount of Cu exceeds 0.7% by mass, crystallized substances such as coarse Al ₇ Cu ₂ Fe and Al ₂ (Fe, Mn) ₃ Cu ₂ are generated, and the embossability and press formability deteriorate. , Remarkably deteriorate corrosion resistance and weldability.

(Mn: 0.5 to 1.5% by mass)
Mn is an element that generates dispersed particles (dispersed phase) during the homogenization heat treatment. These dispersed particles hinder grain boundary movement after recrystallization and refine the recrystallized grains, so that the embossing formability and press formability of the aluminum alloy plate are improved. When the amount of Mn is less than 0.5% by mass, the recrystallized grains are not refined and the embossing formability and press formability are lowered. If the amount of Mn exceeds 1.5% by mass, a coarse Al-Fe-Si-Mn intermetallic compound is formed during melting and casting, and becomes the starting point of fracture in embossing of aluminum alloy sheets and subsequent press forming. The embossing formability and press formability are reduced.

(Mg: 0.5-2.0% by mass)
Mg is an element that contributes to strength. If the amount of Mg is less than 0.5% by mass, a compound is formed as Mg ₂ Si, and the amount of solid solution Mg that substantially contributes to strength decreases, and the strength required for the heat insulator cannot be obtained. When the amount of Mg exceeds 2.0% by mass, the strength becomes excessive and the elongation decreases, and the embossing formability and press formability of the aluminum alloy plate deteriorate. Moreover, the addition of Mg exceeding a predetermined amount also increases the cost.

(Zn: 0.05 to 1.0% by mass)
Zn is an element blended into the raw material by brazing sheet waste. If the Zn content is less than 0.05% by mass, the amount of brazing sheet waste mixed with the raw material is reduced and the recyclability is lowered. When the amount of Zn exceeds 1.0% by mass, an Al—Zn-based compound is generated, which becomes a starting point of cracking in the embossing and subsequent press forming of the aluminum alloy plate, and the embossing formability and press formability are reduced. Corrosion resistance is significantly reduced.

(Inevitable impurities)
Inevitable impurities are impurity elements such as Bi, Sn, Ga, V, Co, Ni, Ca, Mo, Be, Pb, and W, which are mixed from brazing sheet scraps, and are used in aluminum alloy plates for heat insulators. Contains as long as the properties are not impaired. Specifically, the content of inevitable impurities is preferably 0.15% by mass or less in terms of the total amount of the impurity elements.

In the present invention, the aluminum alloy may further contain at least one of Cr and Zr in the above components. Moreover, you may further contain Ti and B in the said component.
(Cr: 0.15 mass% or less, Zr: 0.15 mass% or less)
The transition elements Cr and Zr, like Mn, have the effect of generating dispersed particles (dispersed phase) during the homogenization heat treatment and making the recrystallized grains finer. However, if Cr and Zr are contained in an amount exceeding 0.15% by mass, a coarse intermetallic compound is generated, and the embossing formability and press formability are lowered, and the corrosion resistance is remarkably lowered.

(Ti: 0.007 to 0.1% by mass)
Ti and B have the effect of refining the ingot structure. Usually, when adding Ti, the ingot refining agent (TiB) in the ratio of Ti: B = 5: 1 is melted in the form of a waffle or a rod (melting furnace, inclusion filter, degassing device, Since it is added to any one of the molten metal flow rate control devices, the B corresponding to the content ratio is inevitably added. By adding 0.007% by mass or more of Ti, the ingot crystal grains are refined, and the embossing formability and press formability of the aluminum alloy plate are improved. On the other hand, when the content of either Ti or B exceeds 0.1% by mass, the coarse crystallized product is formed, and the embossability and press molding of the aluminum alloy plate are formed. Sex is reduced.

Next, each characteristic of the aluminum alloy plate will be described.
(Recrystallized structure)
The aluminum alloy plate of the present invention is recrystallized over the entire cross section of the plate thickness in a soft material (O material), that is, a crystal structure observed with an optical microscope, in order to perform press molding without any trouble in a desired product shape as a heat insulator. It has a structure (see FIG. 3 (a)), and an unrecrystallized structure (see FIG. 3 (b)) is not recognized. The non-recrystallized structure decreases work hardening ability and decreases embossing formability and press formability. Such a recrystallized structure is achieved by controlling the annealing conditions in the production of the aluminum alloy sheet.

(Recrystallized grain size: 50 μm or less)
The coarsening of the recrystallized grain size decreases the embossing formability and press formability. Therefore, the recrystallized grain size needs to be 50 μm or less. Moreover, it is preferably 40 μm or less.
In addition, adjustment of a recrystallized grain size is achieved by controlling the cold rolling rate and annealing conditions in manufacture of an aluminum alloy plate. The recrystallized grain size is measured by observation with an optical microscope as will be described later.

(Conductivity: 43.0-49.5% IACS)
The conductivity indicates the solid solution and precipitation state of additive elements in the aluminum alloy plate, particularly Mg and Si. And in order to ensure the intensity | strength requested | required as an aluminum alloy plate for heat insulators, it is necessary to make the solid solution state of Mg and Si into an appropriate range, and it sets it as conductivity: 43.0-49.5% IACS. . When the electrical conductivity is less than 43.0% IACS, the solid solution Mg amount and the solid solution Si amount described later become excessive, the strength of the aluminum alloy plate becomes excessive, and the embossing formability and press formability are lowered. When the electrical conductivity exceeds 49.5% IACS, the solid solution Mg amount and the solid solution Si amount become insufficient, and the strength of the aluminum alloy plate is lowered. In addition, adjustment of electrical conductivity is achieved by controlling the amount of Mg and Si in the aluminum alloy, the homogenizing heat treatment condition and the annealing condition in the production of the aluminum alloy sheet. The conductivity is measured by an eddy current conductivity measuring device as will be described later.

Moreover, in this invention, it is preferable that the total amount of the solid solution Mg amount and solid solution Si amount of an aluminum alloy plate is a predetermined amount.
(Total amount of solid solution Mg amount and solid solution Si amount: 0.8 to 1.5 mass%)
The amount of solid solution Mg and the amount of solid solution Si greatly contribute to the strength of the aluminum alloy plate. And in order to obtain the strength required as an aluminum alloy plate for heat insulators, it is not sufficient to define only the addition amount of Mg and Si as in the prior art (see Patent Documents 5 and 6). It is necessary to control the solid solution and precipitation state.

  In addition to the solid solution Mg and Si content, precipitates with a particle size of 0.1 μm or less contribute significantly to the strength of the aluminum alloy sheet, as does the solid solution Mg content and Si content. To do. For this reason, in the present invention, the total amount of Mg and Si contained in precipitates having a solid solution amount of Mg and Si and a particle size of 0.1 μm or less is calculated as the total amount of solid solution Mg and solid solution. It is defined as the total amount of Si, and the total amount is 0.8 to 1.5% by mass. The adjustment of the solid solution Mg amount and the solid solution Si amount is achieved by controlling the Mg amount and Si amount in the aluminum alloy, the homogenization heat treatment condition and the annealing condition in the production of the aluminum alloy sheet.

  The amounts of solid solution Mg and solid solution Si were determined by measuring the amounts of Mg and Si contained in the residue obtained by the residue extraction method using hot phenol (filter mesh size = 0.1 μm) by ICP emission analysis. Values obtained by dividing the total Mg and Si contained in the alloy plate were used.

  When the total amount of the solute Mg amount and the solute Si amount is less than 0.8% by mass, the strength of the aluminum alloy plate is lowered. When the total amount exceeds 1.5% by mass, the strength of the aluminum alloy plate becomes excessive, and the embossing formability and press formability deteriorate. Further, as described later, the total amount exceeding 1.5% by mass is due to an excess amount of Mg or an excessive heat treatment temperature (homogenization heat treatment temperature and annealing temperature), which leads to an increase in cost.

The aluminum alloy plate for heat insulator according to the present invention preferably has a continuous uneven shape provided on the surface of the aluminum alloy plate by embossing.
In the present invention, the concavo-convex shape is one in which a concave portion and a convex portion are repeatedly provided in a planar manner along two intersecting directions so as to form a lattice-like regular arrangement as shown in FIG. It is preferable. And in FIG. 1, by providing a convex part in the center part of the grating | lattice which four adjacent convex parts form, or a convex part in the center part of the grating | lattice which four adjacent concave parts form, both surfaces of an aluminum alloy plate are provided. Concave and convex shapes are provided in the direction.

  And although the dimension of uneven | corrugated shape is suitably set with the intensity | strength and board | plate thickness which are requested | required as an aluminum alloy plate for heat insulators, for example, the distance a or the distance b which connected the vertex of the adjacent convex part is 5-15 mm ( The distance between the apexes of adjacent concave portions is also 5 to 15 mm), and the height h of the convex portion (concave portion) is 1 to 2.5 mm. Note that the distance a and the distance b may be set to different lengths.

  Moreover, the aluminum alloy plate for insulators according to the present invention is not limited to those provided with uneven shapes along two intersecting directions, but may be provided along one direction although not shown. Furthermore, it is not limited to what is provided in the double-sided direction of the aluminum alloy plate, although not shown in the figure, a flat part without unevenness or a convex part having a different height is provided in the central part of the lattice formed by the convex part, An uneven shape may be provided on one side of the aluminum alloy plate.

<Method for producing aluminum alloy plate for heat insulator>
Next, the manufacturing method of the aluminum alloy plate for heat insulators is demonstrated.
The manufacturing method according to the present invention includes a casting process, a homogenization heat treatment process, a hot rolling process, a cold rolling process, and an annealing process. Moreover, you may include the chamfering process of chamfering the ingot obtained after the casting process. Hereinafter, each step will be described.

(Casting process)
The casting step is a step of melting the aluminum alloy and producing an ingot by DC casting. In addition, about a DC casting method, it carries out in accordance with a conventional method.

(Homogenization heat treatment process)
The homogenization heat treatment step is a step of subjecting the ingot obtained in the above step to a homogenization heat treatment at 450 to 600 ° C. The homogenization heat treatment step is an important step for improving the embossing formability by improving the strength by solid solution of Mg and Si and by refining the recrystallized grains by controlling the dispersed particles.

  When the temperature of the homogenization heat treatment is lower than 450 ° C., the solid solution Mg amount and the solid solution Si amount are decreased, and the strength is decreased. Further, the homogenization treatment is not sufficient, and an inhomogeneous structure remains, which tends to be a crack starting point during emboss molding and press molding. As a result, embossing formability and press formability are reduced. Moreover, it takes too much time to homogenize, and productivity is lowered. When the homogenization heat treatment temperature exceeds 600 ° C., the ingot surface swells and local melting occurs. The homogenization heat treatment is preferably performed for 1 to 24 hours.

(Hot rolling process)
A hot rolling process is a process of producing a hot-rolled sheet by hot-rolling the ingot subjected to the homogenization heat treatment in the above process. About a hot rolling method, it carries out in accordance with a conventional method. The hot rolling may be performed immediately after the homogenization heat treatment or may be performed after the homogenization heat treatment is once cooled and the ingot is heated again. The hot rolling start temperature is preferably 400 to 600 ° C.

(Cold rolling process)
A cold rolling process is a process of cold-rolling the hot-rolled sheet obtained at the said process, and producing a cold-rolled sheet. The cold rolling process is an important process for controlling the recrystallized grain size of the aluminum alloy sheet.

In this step, the cold rolling may be performed a plurality of times (repeatedly), or after the end of hot rolling (before the start of cold rolling) or during the cold rolling is repeated (for example, batch annealing). If it is, if it is continuous annealing at 250-500 degreeC for 0.5 to 24 hours, you may perform 0 (cooling after arrival)-intermediate annealing for 5 minutes at 300-500 degreeC. Furthermore, the cold rolling rate (final cold rolling rate) means the rolling rate at the time of final cold rolling, and is calculated by the following formula (1).
[(T1-T2) / T1] × 100 (1)
In formula (1), T1: sheet thickness after hot rolling or before final cold rolling, and T2: sheet thickness after final cold rolling.

  When the cold rolling rate is less than 70%, the recrystallized grain size becomes coarse, and the embossing formability and press formability of the aluminum alloy plate are lowered. Moreover, since productivity will fall when a cold rolling rate is too high, it is usually 95% or less of a cold rolling rate. Therefore, the cold rolling rate is preferably 70 to 95%.

(Annealing process)
The annealing step is a step of subjecting the cold-rolled sheet obtained in the above step to continuous annealing (final annealing) within a range of 5 minutes within a range of 400 to 500 ° C. and cooling at a cooling rate of 10 ° C./second or more. The annealing process is a process of recrystallizing the cold-rolled sheet to make a soft material (O material, recrystallized structure). The electrical conductivity of the aluminum alloy plate (solid solution Mg amount and solid solution Si amount), recrystallized grains This is an important process for controlling the diameter. And in batch annealing, since an intensity | strength deficiency arises in an aluminum alloy plate, it needs to be continuous annealing. The heating rate up to the final annealing temperature for refining the recrystallized grain size is preferably 5 ° C./second or more.

  When the final annealing temperature is less than 400 ° C., a sufficient recrystallized structure cannot be obtained, or Mg and Si compounds are difficult to be re-dissolved, and the solid solution Mg amount and the solid solution Si amount are reduced, and the conductivity is reduced. The strength is increased and the strength of the aluminum alloy sheet is lowered. Specifically, an unrecrystallized structure remains at 350 ° C. or lower, and a recrystallized structure is obtained at a temperature higher than 350 ° C. and lower than 400 ° C., but the strength is insufficient. When the final annealing temperature exceeds 500 ° C., the surface of the aluminum alloy plate is swollen, the amount of solid solution Mg and the amount of solid solution Si is increased, the conductivity is decreased, and the strength of the aluminum alloy plate is excessive. Embossing formability and press formability are reduced. When the final annealing time exceeds 5 minutes, the effect is saturated and productivity is lowered.

  When the cooling rate is less than 10 ° C./second, the re-dissolved Mg and Si are precipitated again as a compound during cooling, the solid solution Mg amount and the solid solution Si amount are reduced, the conductivity is increased, and the aluminum alloy plate The strength of is reduced.

  In the manufacturing method according to the present invention, the casting step may be performed by thin plate casting instead of DC casting. In that case, the homogenizing heat treatment step and the hot rolling step can be omitted. Further, in the cold rolling step, annealing may be performed before cold rolling or during repeated cold rolling.

  In addition, in the manufacturing method which concerns on this invention, you may include another process between each said process, or the back and front in the range which does not have a bad influence on each said process. For example, you may perform the process process which provides the uneven | corrugated shape continuous by embossing on the surface of the cold rolled sheet in which the final annealing was given after the annealing process.

Next, examples of the present invention will be described.
Ingots having respective compositions shown in Table 1 were melted by DC casting. The average cooling rate during casting was 50 ° C./min from the melting temperature (about 700 ° C.) to the solidus temperature. Subsequently, the ingot was subjected to homogenization heat treatment and hot rolling shown in Table 2. The hot rolling end temperature was 250 to 350 ° C. Then, after cold rolling or intermediate annealing (continuous annealing), cold rolling was performed to obtain a cold-rolled sheet having a thickness of 0.4 mm. Each cold-rolled sheet was subjected to final annealing (continuous annealing) shown in Table 2 to obtain test materials. In addition, since alloys A, B, E, F, and K to P containing Ti used TiB for addition of Ti, they contain B together with Ti. In addition, in the homogenization heat treatment, when the homogenization heat treatment was performed at a temperature exceeding the upper limit (abbreviation No. in Table 2), burning occurred in the ingot, and subsequent production was impossible.

  The crystal structure of each test material was confirmed. Next, the recrystallized grain size, electrical conductivity, and the total amount of solute Mg and solute Si were measured by the following method. The results are shown in Table 3. In Tables 1 to 3, the underlined characters indicate that the claims are not satisfied.

(Crystal structure)
Samples were taken from five locations of the test material, and after polishing the plate thickness cross-sectional direction (perpendicular to the rolling direction) to a mirror state, the surface anodized using Barker's liquid was observed with an optical microscope, It was confirmed whether or not a recrystallized structure (see FIG. 3A) was observed over the entire cross section of the plate thickness. The test material No. In 1 to 24, an unrecrystallized structure (see FIG. 3B) was not confirmed, and a recrystallized structure was obtained.

(Recrystallized grain size)
The recrystallized grain size referred to here is the maximum diameter of the recrystallized grains in the longitudinal direction (rolling direction) of the specimen. The recrystallized grain size was measured by a line intercept method in the longitudinal direction by observing the surface of the test material which had been mechanically polished by 0.05 to 0.1 mm and electrolytically etched using an optical microscope. One measurement line length was 0.95 mm, a total of 5 fields were observed with 3 lines per field, and the average value of the measured recrystallized grain sizes was calculated.

(conductivity)
The conductivity was measured by a commercially available eddy current conductivity measuring device. In addition, the measurement of the conductivity was performed at any five locations on the surface of the test material with a space of 100 mm or more between each other. The electrical conductivity in the present invention is obtained by averaging the measured electrical conductivities.

(Solution Mg amount and solute Si amount)
The amount of Mg and the amount of Si in the solution obtained by the residue extraction method using hot phenol and the precipitate having a particle size of 0.1 μm or less were measured. Specifically, the amount of Mg and Si contained in the residue obtained by the residue extraction method with hot phenol (filter mesh size = 0.1 μm) was measured by ICP emission analysis, and the total Mg contained in the aluminum alloy plate was The value removed from the amount of Si was used.

  Next, the strength (mechanical properties), embossing formability, press formability, corrosion resistance, and recyclability of each test material were evaluated by the following methods. The results are shown in Tables 3 and 4.

(mechanical nature)
In the tensile test for measuring mechanical properties, No. 5 test piece (25 mm × 50 mmGL × plate thickness) of JISZ2201 was sampled from each test material, and a room temperature tensile test was performed. The tensile direction of the test piece at this time was set to a direction parallel to the rolling direction. The tensile speed was 5 mm / min up to 0.2% proof stress and 20 mm / min after proof stress. The N number for the measurement of mechanical properties was 5, and each was calculated as an average value. And the thing whose tensile strength is 160 Mpa or more was made into the pass ((circle)), and the thing less than 160 Mpa was made into the rejection (x).

(Embossing formability)
In the embossing formability test, a rectangular blank (size: 200 mm × 200 mm) was cut out from the test material. The rectangular blank was embossed using an uneven embossing mold shown in FIG. Of the 100 vertices of the concavo-convex portion, the number of occurrence of cracks was defined as the crack occurrence rate. The crack occurrence rate at this time was 60% or less as pass (◯), and over 60% was rejected (x). In addition, as uneven | corrugated shape, it was set as the distance a = 10mm between convex-part vertices, distance b = 10mm, and the height h of a convex part = 2.4mm. Further, the distance between the concave vertices and the height of the concave are the same as those of the convex.

(Press formability)
In the press molding test, a rectangular blank (size: 150 mm × 150 mm) was cut out from a test material that was embossed under processing conditions (the height of the concavo-convex part = 1.8 mm) in which no cracks occurred at the top of the concavo-convex part. . As shown in FIG. 2, punch 5: □ 90 mm (shoulder R: 10 mm, corner: 10 mm), die 6: □ 97.5 mm (shoulder R: 10 mm, corner: 10.75 mm) with respect to the rectangular blank 1. Using a mold, square tube drawing was performed by using the crease presser plate 3 and the spacer 4 so that the clearance C on the die face surface was adjusted to the height including the height of the concavo-convex portions of each rectangular blank 1 and the plate thickness. The molding limit height at the time of rectangular tube drawing was 23 mm or more as pass (◯), and less than 23 mm was rejected (x). In addition, general rust preventive oil was applied as lubricating oil.

(Corrosion resistance)
A salt spray test (JIS Z2371) was performed on each specimen. The occurrence of corrosion after 1000 hours was judged visually. Those with significant corrosion were evaluated as rejected (×), those with a moderate degree were evaluated as acceptable (Δ), and those with minor corrosion were evaluated as acceptable (◯).

  From the results of Tables 1 to 4, the test material No. In order to satisfy the claims, Nos. 1 to 7 were acceptable in any of mechanical properties, embossing formability, press formability, and corrosion resistance.

  On the other hand, the test material No. No. 8, since the Si amount exceeds the upper limit, the electrical conductivity is less than the lower limit, and the total amount of the solid solution Mg amount and the solid solution Si amount (hereinafter referred to as the solid solution amount) exceeds the upper limit value. Any press formability was not acceptable. Test material No. In No. 9, since the amount of Fe exceeded the upper limit, the embossing formability and press formability were unacceptable.

  Specimen No. No. 10 is an aluminum alloy plate that is inferior in recyclability because the amount of Cu is less than the lower limit, and the electrical conductivity exceeds the upper limit and the mechanical properties are not acceptable. Specimen No. No. 11 failed in any of embossing formability, press formability, and corrosion resistance because the amount of Cu exceeded the upper limit.

  Specimen No. No. 12 failed in both embossing formability and press formability because the amount of Mn exceeded the upper limit. Specimen No. In No. 13, since the Mg amount was less than the lower limit and the conductivity exceeded the upper limit, the mechanical properties were unacceptable. Specimen No. In No. 14, since the Mg amount exceeded the upper limit value, the conductivity was less than the lower limit value, and the solid solution amount exceeded the upper limit value, both emboss formability and press formability were unacceptable.

  Specimen No. No. 15 was an aluminum alloy plate with poor recyclability because the Zn content was less than the lower limit. Specimen No. No. 16 failed in any of embossing formability, press formability, and corrosion resistance because the Zn amount exceeded the upper limit. Specimen No. 17 or No. No. 18 failed in any of emboss formability, press formability, and corrosion resistance because the Cr amount or Zr amount exceeded the upper limit.

  Specimen No. In No. 19, the annealing process is batch annealing (the annealing time is long), so a recrystallized structure is obtained. However, the cooling rate is less than the lower limit value, and the electrical conductivity exceeds the upper limit value. Met. Moreover, since the heating rate of the annealing process was slow and the recrystallized grain size exceeded the upper limit, the embossing formability and press formability were also unacceptable. Specimen No. No. 20 had a final annealing temperature of 380 ° C. lower than the lower limit value and an electric conductivity exceeding the upper limit value, but the recrystallized structure was obtained, but the mechanical properties were unacceptable. Specimen No. In No. 21, since the final annealing temperature in the annealing process exceeded the upper limit value, the electrical conductivity was less than the lower limit value, the solid solution amount exceeded the upper limit value, and both the embossing formability and press formability were rejected.

  Specimen No. No. 22, because the homogenization heat treatment temperature of the homogenization heat treatment step is less than the lower limit value, the electrical conductivity exceeds the upper limit value, and the solid solution amount becomes less than the lower limit value, and any of mechanical properties, embossing formability and press formability Also failed. Specimen No. No. 23 is an aluminum alloy plate of Patent Document 6, which has an inferior recyclability because the Si amount and the Fe amount are less than the lower limit values. In addition, since the annealing process is batch annealing (annealing time is long), even if the final annealing temperature is 350 ° C. below the lower limit, a recrystallized structure is obtained, but the cooling rate is less than the lower limit, Since the solid solution amount was also the lower limit, the mechanical properties were unacceptable. Furthermore, since the cold rolling ratio (final cold rolling ratio) in the cold rolling process is less than the lower limit value and the heating rate in the annealing process is slow, the recrystallized grain size exceeds the upper limit value. It was a failure. Specimen No. In No. 24, the cooling rate in the annealing process was less than the lower limit value, the electrical conductivity exceeded the upper limit value, and the solid solution amount was also less than the lower limit value.

a, b Distance 1 Rectangular blank 3 Wrinkle presser plate 4 Spacer 5 Punch 6 Die C Clearance

Claims (5)

Si: 0.4-2.0 mass%, Fe: 0.2-0.6 mass%, Cu: 0.1-0.7 mass%, Mn: 0.5-1.5 mass%, Mg: An aluminum alloy plate comprising 0.5 to 2.0% by mass, Zn: 0.05 to 1.0% by mass, the balance being made of an aluminum alloy composed of Al and inevitable impurities,
The aluminum alloy plate has a recrystallized structure over the entire cross section of the plate thickness, has a recrystallized grain size of 50 μm or less, and an electrical conductivity of 43.0 to 49.5% IACS. Aluminum alloy plate.   The aluminum alloy plate for a heat insulator according to claim 1, wherein the aluminum alloy further contains at least one of Cr: 0.15 mass% or less and Zr: 0.15 mass% or less.   In the aluminum alloy plate, the total amount of solid solution Mg and solid solution Si is 0.8 to 1.5% by mass, and the solid solution Mg amount and solid solution Si amount are determined by a residue extraction method using hot phenol. The aluminum alloy plate for a heat insulator according to claim 1 or 2, wherein the obtained solution and the amount of Mg and Si contained in a precipitate having a particle size of 0.1 µm or less.   The aluminum alloy plate for heat insulator according to any one of claims 1 to 3, wherein the aluminum alloy plate is provided with a continuous uneven shape on its surface by embossing. A casting step of melting the aluminum alloy according to claim 1 or claim 2, and producing an ingot by DC casting from the molten metal,
A homogenization heat treatment step of subjecting the ingot to a homogenization heat treatment at 450 to 600 ° C .;
A hot rolling step of hot rolling the ingot subjected to homogenization heat treatment to produce a hot rolled sheet;
A cold rolling step of cold rolling the hot rolled sheet at a cold rolling rate of 70% or more to produce a cold rolled sheet;
A method for producing an aluminum alloy plate for heat insulator, comprising: subjecting the cold-rolled sheet to a continuous annealing within 5 minutes within a range of 400 to 500 ° C. and cooling at a cooling rate of 10 ° C./second or more. .