JP2005163175A - Aluminum alloy rolling stock for coating, and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling stock having strength, bending workability and corrosion resistance required as those for a coating material by utilizing brazing sheet scrap as the raw material, and to provide a method for producing the same at a low cost. <P>SOLUTION: The ingot of an aluminum alloy using brazing sheet scrap as the raw material and having a composition comprising 1.0 to 3.2% Si and 0.1 to 1.2% Mn, and in which the content of Fe is controlled to ≤0.7%, Mg to ≤0.5%, Cu to ≤0.6% and Zn to ≤1.2% is subjected to homogenizing treatment in the temperature range of 450 to 570°C for 1 to 24 hr. Next, hot rolling is started at ≥400°C and is finished at ≤350°C, and further, cold rolling is performed at a rolling ratio of ≥65%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rolled aluminum alloy material for coating used by being subjected to a coating baking process and a method for producing the same, and in particular, Al- having excellent strength, bending workability, and corrosion resistance, which is manufactured at low cost using scraps of brazing sheets. The present invention relates to an Si-Mn-based rolled aluminum alloy for coating and a method for producing the same.

  Aluminum alloy rolled material for painting used by applying paint baking treatment to building roofing materials, interior / exterior panel materials, or composite panel inner / outer panel materials bonded to resin plates has a thickness of 0.1 to 2.0 mm. A ¼ hard to hard material such as an Al—Mg alloy (JIS 5052), an Al—Mn— (Mg) alloy (JIS 3003, 3004, 3005) or a pure Al alloy (JIS 1100) is used. Among them, JIS5052-H32 and H34 are those that are quantitatively large. An acrylic resin, an epoxy resin, a polyester resin, or the like is used for these coatings, and the coating baking process is performed under the condition that the coiled rolled plate is held for several seconds or less (including no holding) in a temperature range of 160 to 220 ° C. It is carried out continuously, and after leveling, it is cut into a predetermined dimension and subjected to processing such as bending as required. In general, some of the same alloy-based scrap may be used as a raw material for these alloys, but since most of them use new bullion, there is a problem that the raw material cost must be increased.

  Moreover, H32 and H34 tempered material of JIS5052 alloy, which is frequently used as a rolled sheet for coating, is hot rolling → primary cold rolling → intermediate annealing (recrystallization) → secondary cold rolling (cold rolling of H32 material). (The rate is about 20%, H34 material is about 40%) → It is manufactured through the process of stabilization annealing, but since the stabilization annealing is performed at a temperature of about 160 to 250 ° C. in the final process, the tension after paint baking Although the decrease in strength is small, there is a drawback that the manufacturing process is too long and the cost is high.

  On the other hand, although different from the coating material, brazing sheets are widely used for aluminum alloy heat exchangers, etc., and JIS3003 / 3N03 / 3N33 alloys such as Al-Mn alloys are used as the core material of the brazing sheets. JIS7072 alloy, which is partially Al—Zn alloy, is also used. As the brazing material, JIS4343 / 4004 / 4N45 alloy of Al—Si alloy is used, and this is clad on one side or both sides of the core (clad rate of about 5 to 15%). Therefore, when the scraps of these brazing sheets are melted, an Al-Si-Mn- (Cu)-(Zn) -based alloy is formed, which is used as a core alloy, brazing alloy or other wrought material for brazing sheets. It is difficult to recycle the alloy in terms of composition, and it is often reused as a part of the raw material of the high concentration Si-containing aluminum alloy casting that can only be obtained at low cost.

An aluminum alloy wrought material for building materials using scraps of brazing sheet is also disclosed (see Patent Document 1). In this material, although the strength and bending workability are excellent, the amount of Cu is 1. The amount is too much as 2 to 3.5%, which is not preferable in terms of corrosion resistance. In addition, an extruded material is subjected to an aging treatment of, for example, 180 ° C. × 3 hours, and a plate material is subjected to a solution treatment of, for example, 530 ° C. Therefore, there is a drawback that it is expensive.
Japanese Patent No. 3408213

  As mentioned above, the reuse of brazing sheets and scrap is limited in terms of alloy composition, but this can be reused as a coating alloy that uses a relatively wide variety of alloys to save energy and reduce costs. However, since the component system after melting of these scraps becomes an Al-Si-Mn- (Cu)-(Zn) -based alloy as described above, the mechanical performance necessary for coating is obtained. It was difficult to obtain and hesitated to use it as it was for painting.

  In order to solve the above-mentioned conventional problems in the reuse of brazing sheets and scraps, the inventors have conducted tests and examinations from various viewpoints. As a result, the components after melting of the brazing sheets and scraps are Al-Si-Mn. It has been found that even if it is a-(Cu)-(Zn) -based alloy, the necessary performance as a rolled material for coating can be obtained by applying an appropriate tempering material by applying an appropriate process condition.

  This invention has been made on the basis of the above knowledge, and its purpose is to use low-cost brazing sheet / scrap as a raw material, which has the strength and bending workability required for coating, An object of the present invention is to provide a rolled aluminum alloy material for coating having good corrosion resistance and a method for producing the same.

  The rolled aluminum alloy material for coating excellent in strength, bending workability and corrosion resistance according to claim 1 for achieving the above object is an aluminum alloy rolled material produced from brazing sheet scrap as a raw material, and comprises Si1. 0 to 3.2%, Mn 0.1 to 1.2%, Fe 0.7% or less, Mg 0.5% or less, Cu 0.6% or less, Zn 1.2% or less, the balance Al and unavoidable It is characterized by comprising an impurity.

The manufacturing method of the aluminum alloy rolled material for coating excellent in strength, bending workability, and corrosion resistance according to claim 2 is based on Si 1.0 to 3.2%, Mn 0.1 to 1.2 using brazing sheet scrap as a raw material. In an ingot of aluminum alloy composed of the balance Al and unavoidable impurities, 450 to 570, containing Fe in an amount of 0.7% or less, Mg 0.5% or less, Cu 0.6% or less, and Zn 1.2% or less. A homogenization treatment is performed at a temperature within a range of 1 to 24 hours, and then hot rolling is started at a temperature of 400 ° C. or more and finished at 350 ° C. or less, and further cold rolling is performed at a rolling rate of 65% or more. The tensile strength after application and cold rolling is 220 N / mm ² or more, and the tensile strength after coating baking at 220 ° C. or less is 200 N / mm ² or more.

  According to the present invention, low-cost brazing sheet scrap is used as a raw material, and the intermediate annealing, secondary cold rolling and final annealing steps are omitted and used in the state of being cold-rolled. Even if a low-cost manufacturing process is employed, it is possible to manufacture a rolled aluminum alloy material for coating having sufficient strength and bending workability and excellent corrosion resistance.

First, the reasons for limiting the component composition in the present invention will be described.
The present invention is characterized in that brazing sheet scrap is used as a raw material to achieve low cost. However, when there is not enough alloy composition scrap suitable for component adjustment, a small amount of new metal or A new mother alloy may be blended.

Si:
Si is an element contained in brazing sheet / scrap brazing material, and is also an element necessary for securing strength as a building material. If it is less than 1.0%, the strength is insufficient. On the other hand, if it exceeds 3.2%, the size of the Al—Si-based intermetallic compound is increased and the bending workability is deteriorated. A preferable content of Si is in the range of 1.0 to 3.2%.

Mn:
Mn is an element contained in the core material of the brazing sheet / scrap, and is also an element necessary for ensuring the strength as a coating material. If it is less than 0.1%, the strength is insufficient. On the other hand, if it exceeds 1.2%, the size of the Al—Mn—Fe-based intermetallic compound is increased and the bending workability is deteriorated. The preferable content of Mn is in the range of 0.1 to 1.2%.

Fe:
Fe is an impurity element contained in the core material and brazing material of the brazing sheet / scrap, and if it is too much, the size of the Al—Fe—Mn intermetallic compound becomes large and the bending workability deteriorates. The Fe content is preferably regulated to 0.7% or less.

Mg:
Mg is an element contained in a part of the brazing sheet / scrap brazing alloy, and if it is too much, the work hardenability increases and the bendability deteriorates. The Mg content is preferably regulated to 0.5% or less.

Cu:
Cu is an element contained in a part of the alloy of the core material of the brazing sheet / scrap. If it is too much, thread corrosion occurs and the corrosion resistance deteriorates. The Cu content is preferably regulated to 0.6% or less.

Zn:
Zn is an element contained in a brazing sheet / scrap core material, a part of brazing alloy, and a skin alloy as a sacrificial anode material. If it is too much, pitting corrosion occurs and corrosion resistance deteriorates. The Zn content is preferably regulated to 1.2% or less.

  If the impurity elements other than the above, such as Cr, Ti, and B, are each 0.15% or less, the performance of the rolled aluminum alloy for coating is not particularly impaired.

Next, the manufacturing method of the aluminum alloy rolled material for coating of this invention is demonstrated.
The feature of the method for producing a rolled aluminum alloy material for painting of the present invention is that it omits intermediate annealing, secondary cold rolling and final annealing steps, and is energy-saving and low-cost to be used in the state of cold rolling. It is intended to improve the bending workability after the paint baking process by softening using the heat during the paint baking process.

  First, the brazing sheet scrap as described above is melted and cast by DC casting or the like according to a conventional method.

  The obtained ingot is homogenized and then hot-rolled and further cold-rolled to a product plate thickness of about 0.1 to 2.0 mm.

  The homogenization treatment is preferably carried out at a temperature in the range of 450 to 570 ° C. for 1 to 24 hours. If the homogenization temperature is less than 450 ° C., homogenization is insufficient and bending workability is poor. If the holding time is less than 1 hour, homogenization is insufficient, and holding for more than 24 hours is economically wasteful because the homogenization is saturated.

  After homogenizing as described above, hot rolling is started immediately. In this case, the hot rolling start temperature is preferably 400 ° C. or higher. If the hot rolling start temperature is less than 400 ° C., the hot workability is poor, and cracks may occur during hot rolling. Hot rolling may be started by once lowering the ingot after homogenization to room temperature and then heating it to 400 ° C. or higher.

  Moreover, it is preferable that the end temperature of hot rolling shall be 350 degrees C or less. When the hot rolling finish temperature exceeds 350 ° C., partial recrystallization or complete recrystallization occurs, and the strength of the cold rolled material may be insufficient.

  The cold rolling performed after hot rolling is desirably performed at a rolling rate of 65% or more. If the cold rolling rate is less than 65%, the work hardening is insufficient and the strength may be insufficient.

In the present invention, the tensile strength after cold rolling (hereinafter, cold-rolled material) is 220 N / mm ² or more and 220 ° C. or less, and the tensile strength is 200 N / mm ^2. As specified above. The reason is as follows.

That is, as described above, the rolling material for painting that is frequently used is H24 tempered material of JIS3005 alloy. Therefore, when the material or more is targeted, the tensile strength after the coating baking process is 200 N / mm ² or more. It becomes. According to the experiment, the larger the cold rolling rate is, the larger the margin of reduction in tensile strength due to the coating baking process is. The reduction margin when the cold rolling rate is about 65% is about 20 N / mm ² , and the cold rolling rate is about 90%. The reduction allowance is about 35 N / mm ² . Since the cold rolling rate is often about 65%, in the present invention, for the sake of convenience, the tensile strength in the case of the cold rolling rate of 65% by the coating baking process is set to the target 200 N / mm ² of the tensile strength after the coating baking process. It was specified to be 220 N / mm ² or more plus a reduction allowance of 20 N / mm ² .

  In addition, the bendability of paints that have been baked is not cracked in the coating film or the substrate when bent 180 ° with an inner bend radius that is twice the plate thickness, and the corrosion resistance is not scratched. The fact that no filiform corrosion or pitting corrosion occurs in 1000 hours in a neutral salt spray test using an attached test piece is a general characteristic required for coating materials, and the present invention also aimed at this characteristic.

  Examples of the present invention will be described below in comparison with comparative examples. In addition, these Examples show one embodiment of this invention, and this invention is not limited to these.

Examples and Comparative Examples The alloys shown in Alloy Nos. 1 to 12 in Table 1 are melted by changing the blending ratio of various brazing sheets and scraps, respectively, and thickness is 450 mm × width 1100 mm × length 3000 mm by the DC casting method. This is cast into an ingot.

  The obtained ingots were combined with the conditions of production process numbers A to E in Table 2 to obtain cold rolled materials (coil shapes having a width of 1000 mm) of sample numbers 1A to 12A shown in Table 3, and then The cold-rolled material was continuously baked in the following steps to obtain a coating material.

  There are various coating methods depending on the selection of the degreasing treatment solution, the chemical conversion treatment solution, and the coating material. In this example, the following general method was adopted. That is, degreasing treatment while rewinding the coil (sulfuric acid) → washing with water → chemical conversion treatment (phosphate chromate) → undercoating of 5 μm epoxy resin on both sides → baking process (200 ° C, no holding, temperature rise and cooling rate is about (10 ° C / sec) → Furthermore, only one side of the polyester resin 15μm is overcoated (before actual use) → Baking treatment (210 ° C, no holding, temperature rise and cooling rate is about 10 ° C / sec) → Leveling → Predetermined dimensions It was performed in the process of cutting.

  About each cold-rolled material and coating material, the tensile strength of the direction parallel to a rolling direction was calculated | required with the JIS5 tension test piece. The tensile strength of the coating material in this case was measured after removing the paint with sulfuric acid.

  Each coated plate was subjected to a 180 ° bending test using a JIS No. 3 bending test piece cut out in a direction perpendicular to the rolling direction (direction inferior in bendability). The 180 ° bending test is performed under the condition that the surface of epoxy resin (thickness 5 μm) + polyester resin (thickness 15 μm) is on the outer side with an inner bending radius that is twice the plate thickness. When observed with a 10-fold magnifier, no crack occurred in the coating film or the base material, and the case where the crack occurred was judged as unacceptable (X).

  Furthermore, the corrosion resistance of each coating material is evaluated in accordance with the JIS Z 2371 salt spray test method, and the test piece is prepared with a depth that reaches the surface of the epoxy resin (thickness 5 μm) + polyester resin (thickness 15 μm). Insert a scratch (cross-cut with a cutter knife) and perform a neutral salt spray test for 1000 hours. If no filiform corrosion or pitting corrosion occurs, pass (○); (X). The respective results are also shown in Table 3.

In Table 3, the cold rolled sheets and coating materials of sample numbers 1A, 1B, 1C, 2A, 3A, 4A, and 5A are all invention examples that satisfy both the component composition and the manufacturing process that satisfy the conditions defined in the present invention. Yes, these cold-rolled materials have a tensile strength of 220 N / mm ² or more, and a tensile strength after paint baking treatment has a high strength of 200 N / mm ² or more, comparable to JIS 3005-H24, and also has bending workability. The material was found to be excellent in corrosion resistance.

  On the other hand, the cold rolled material and the coating material of sample numbers 1D and 1E are alloys satisfying the component composition conditions defined in the present invention, but are comparative examples in which the manufacturing process conditions deviate from the conditions defined in the present invention. . In 1D, since the injection amount of hot rolling oil was reduced, cooling became insufficient, the hot rolling end temperature increased, recrystallization occurred, and the tensile strength of the cold rolled material and coating material decreased. Moreover, since the cold rolling rate was insufficient for 1E, the tensile strength of the cold rolled material and the coating material was lowered.

  The cold-rolled materials and coating materials of sample numbers 6A to 13A are comparative examples that satisfy the manufacturing process conditions specified in the present invention but do not satisfy the component composition conditions. 6A had too much Si, so the size of the Al—Si based intermetallic compound, 8A had too much Mn, so the size of the Al—Mn—Fe based intermetallic compound, 10A had too much Fe, and Al— The size of the Mn—Fe intermetallic compound is increased, and the bending workability is deteriorated in all cases. Moreover, since 11A had too much Mg content, work hardening property increased and bending workability deteriorated. Since the amount of Si in 7A and the amount of Mn in 9A were too small, the tensile strengths of the cold-rolled material and the coating material both decreased. Moreover, since 12A has too much Cu, filamentous corrosion occurs in the salt spray test, and 13A has too much Zn, resulting in pitting corrosion. Both have deteriorated corrosion resistance.

Claims (2)

Aluminum alloy rolled material produced from brazing sheet scrap as raw material, containing Si 1.0-3.2% (mass%, the same applies hereinafter), Mn 0.1-1.2%, Fe 0.7% Hereinafter, aluminum alloy for coating excellent in strength, bending workability and corrosion resistance, characterized by being controlled to Mg 0.5% or less, Cu 0.6% or less, Zn 1.2% or less, and remaining Al and inevitable impurities Rolled material. It contains Si 1.0-3.2% and Mn 0.1-1.2% using brazing sheet scrap as a raw material, Fe 0.7% or less, Mg 0.5% or less, Cu 0.6% or less, Zn 1. The aluminum alloy ingot consisting of the remaining Al and inevitable impurities is subjected to a homogenization treatment at a temperature in the range of 450 to 570 ° C. for 1 to 24 hours, and then hot rolling is performed to 400 ° C. It starts at the above temperature and ends at 350 ° C. or less, and further cold-rolls at a rolling rate of 65% or more, and the tensile strength after cold rolling is 220 N / mm ² or more, and is baked at 220 ° C. or less. A method for producing a rolled aluminum alloy material for coating excellent in strength, bending workability, and corrosion resistance, wherein the tensile strength after treatment is 200 N / mm ² or more.