JP5021905B2 - Aluminum alloy rolled sheet for painted roofing material and method for producing the same - Google Patents

Description

  This invention is used for rolled aluminum alloy sheets for applications that are used after being baked with paint, especially for roofing materials, building materials such as interior and exterior of buildings, housings for various electrical equipment and measuring instruments, panels for electrical equipment devices, etc. The present invention relates to a rolled aluminum alloy sheet and a manufacturing method thereof.

  As an aluminum alloy rolled sheet for a painted roofing material used after being subjected to a paint baking process, JIS A3005P-H24 of an Al—Mn—Mg alloy having a thickness of about 0.5 to 1.0 mm is frequently used.

  Acrylic resin, epoxy resin, polyester resin, etc. are used for these coatings, and the coating baking process is continuously carried out under the condition of no holding to 160 to 220 ° C. while holding the coiled rolled plate up to several seconds holding. Further, after leveling, it is cut into a predetermined size and subjected to bending or deep drawing (a part called a cap called a so-called cap attached to cover the connecting part between the processed plate and processed plate) as necessary. It is constructed from.

  However, the bending workability of the frequently used paint plate of JISA3005P-H24 is at a level where there is no practical problem with most current designs (180 ° bending with an inner bending radius of about 1.5 times the plate thickness). However, sharp designs that are becoming increasingly demanding and have a sharp bendability (bending at 180 ° with an inner bend radius of 0.5 times the plate thickness) may crack, and further improvements in bendability are required.

  In addition, the deep drawing ear rate of the paint plate of JISA3005P-H24, which is frequently used, is too high at 10-20%, so that the paint film peels off when the corners are pulled and compressed, and the peeled parts are hand-painted. Doing or unnecessary cutting of the ear high part will increase the cost and delay of construction, and also reduce the deep drawing ear rate (the ear rate is 6 to prevent the peeling of the paint film and the cutting of the ear high part). % Or less) is required.

For example, Patent Document 1 is disclosed as an aluminum alloy wrought material for roof materials using a 3000 series alloy plate.
Japanese Patent Laid-Open No. 11-347665

  However, although the invention described in Patent Document 1 discloses a method for forming a roof panel using a 3000 series alloy plate in detail, it does not disclose a manufacturing method and performance of the 3000 series alloy plate used. Therefore, it is difficult to know whether these strengths, bending workability and deep drawing ear rate satisfy the above requirements.

Patent Document 2 is an example of an aluminum alloy wrought material for painted building materials using a 3000 series alloy plate.
Japanese Patent No. 3274808

  However, the invention described in Patent Document 2 is a manufacturing method and performance of a rolled aluminum alloy sheet for resin-coated building materials that is subjected to high-temperature baking such as fluorine resin using a 3000 series alloy sheet (such as yield strength and bending workability by 135 ° bending). However, it is also difficult to know whether the tensile strength, bending workability by 180 ° bending, and deep drawing ear rate satisfy the above requirements, and this manufacturing method requires final annealing. Therefore, it becomes high cost.

  As described above, JIS A3005P-H24, which is frequently used as an aluminum alloy rolled sheet for painted roofing materials used after being subjected to paint baking treatment, is required to further improve the bending workability and reduce the deep drawing ear rate. .

  The present invention has been made against the background of the above circumstances, and it is an object of the present invention to provide an aluminum alloy rolled sheet having improved bending workability and reduced deep drawing ear ratio without impairing the strength after paint baking, and a method for producing the same. It is what.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive experiments and examinations. As a result, even if the component is an Al-Mn-Mg alloy, appropriate tempering is performed by applying appropriate process conditions. It was found that the problem as a rolled sheet for a painted roofing material can be solved by using the material, and the present invention has been made.

Specifically, it contains Mn 1.0 to 1.5%, Mg 0.2 to 0.6%, Si 0.6% or less, Fe 0.7% or less, Cu 0.30% or less, Zn 0. 25% or less, the balance is made of Al and inevitable impurities, the tensile strength of the final cold-rolled sheet is 175 N / mm ² or more, and the tensile strength after the baking treatment at 220 ° C. or less There 165 N / mm ² or more, the average crystal grain size 30μm or less, deep drawing, characterized in that the ear rate 6% or less, strength and bending workability and the aluminum alloy rolled sheet for excellent coating roofing material in low ear index is there.

In addition, the ingot of the aluminum alloy having the chemical composition according to claim 1 is subjected to a homogenization treatment at a temperature within a range of 450 to 630 ° C. for 1 to 24 hours, and then hot rolling is performed to 400. After starting at a temperature not lower than 300 ° C. and ending at not higher than 300 ° C., and further performing primary cold rolling at a rolling rate of not less than 30%, a continuous annealing furnace having an average heating rate and an average cooling rate of 3-50 ° C./sec Then, intermediate annealing is performed at an annealing temperature of 400 to 630 ° C. without holding or holding for 1 minute or less, and finally, 15 to 30% of cold rolling is performed, whereby the tensile strength of the final cold rolled sheet is 175 N / mm. ^2. Strength and bending, characterized in that tensile strength after paint baking at 220 ° C. or less is 165 N / mm ² or more, average crystal grain size is 30 μm or less, and deep drawing ear ratio is 6% or less. Painted roof with excellent workability and low ear coverage It is a manufacturing method of the aluminum alloy rolled sheet for materials.

  According to the present invention, by using an Al-Mn-Mg alloy and applying an appropriate tempering material by applying an appropriate process condition, the bending workability can be improved and the deep drawing ear rate can be improved without losing strength. By reducing the number, it is possible to manufacture a rolled aluminum alloy sheet for a painted roofing material that can be designed with a sharper bending process, shorten the work period, and reduce the construction cost.

  First, the reasons for limiting the component composition in the present invention will be described.

Mn:
Mn is an element necessary for securing the strength as a roofing material. If it is less than 1.0%, the strength is insufficient. On the other hand, if it exceeds 1.5%, the size of the Al—Mn—Fe intermetallic compound increases. Bending workability deteriorates. Therefore, the Mn content is in the range of 1.0 to 1.5%.

Mg:
Mg is also an element necessary for ensuring the strength as a roofing material. If it is less than 0.2%, the strength is insufficient, and if it exceeds 0.6%, the work hardenability increases and the bending workability deteriorates. Therefore, the Mg content is in the range of 0.2 to 0.6%.

Si:
Si is an impurity element contained in aluminum scrap, aluminum ingot, etc. If it is too much, the size of the Al-Si intermetallic compound becomes large and bending workability deteriorates. Therefore, the Si content is restricted to 0.6% or less.

Fe:
Fe is an impurity element contained in aluminum scrap, aluminum ingot, etc. If it is too much, the size of the Al—Fe—Mn intermetallic compound becomes large and bending workability deteriorates. Therefore, the amount of Fe is restricted to 0.7% or less.

Cu:
Cu is an impurity element contained in aluminum scrap or the like, and if it is too much, thread corrosion occurs and the corrosion resistance deteriorates. Therefore, the amount of Cu is restricted to 0.30% or less.

Zn:
Zn is an impurity element contained in aluminum scrap or the like, and if it is too much, pitting corrosion occurs and the corrosion resistance deteriorates. Therefore, the Zn content is restricted to 0.25% or less.

  If impurity elements other than the above, such as Cr and V, are each 0.10% or less, the performance of the rolled aluminum alloy sheet for painted roofing material is not particularly impaired.

  Moreover, Ti and B are elements effective for preventing the ingot from cracking by uniformly refining the crystal grains of the ingot, so Ti: 0.005 to 0.10%, B: 0.0001 to 0.01% added It is preferable to do this. If each is less than the lower limit, the effect is not sufficiently obtained, and if the upper limit is exceeded, coarse crystallized matter is formed and the moldability is lowered.

  Furthermore, in this invention, the characteristic value of the final cold-rolled board obtained by rolling and the coating board which carried out the coating baking process is prescribed | regulated, and these are demonstrated below.

In the present invention, the final cold-rolled sheet has a tensile strength of 175 N / mm ² or more and 220 ° C. or less, and a tensile strength after coating baking of 165 N / mm ² or more, an average crystal grain size of 30 μm or less, and a deep drawing ear The rate is specified as 6% or less. The reason is as follows.

That is, as described above, since the rolled sheet for painted roofing material that is frequently used is JISA3005P-H24, when the strength level of JISA3005P-H24 or more is targeted, the tensile strength after the coating baking process is 165 N / mm ² or more. In order to improve bending workability, the average grain size is preferably 30 μm or less, and the ear draw ratio is required to be 6% or less in order to eliminate the need for peeling of the coating film and the removal of the high-pitched portion at the deep drawing ear ratio. is there. Here, the deep drawing ear rate is the same conditions as described in the examples, blank diameter 62.0 mmΦ, punch diameter 32.0 mmΦ, clearance 20-40%, wrinkle presser pressure 250 kg (with lubricating oil applied) The ear rate was determined after deep drawing under the conditions of Ear rate is expressed as a percentage (%) by dividing the difference between the average height of four ears (mm) and the average height of four valleys (mm) by the average value of four valley heights (mm). ).

In addition, according to the experiment, when the final cold rolling rate is relatively small, about 15 to 30%, the reduction in tensile strength due to the coating baking process is about 10 N / mm ² or less. The tensile strength of the cold-rolled sheet is 175 N / mm ² or more, which is obtained by adding 10 N / mm ² for the reduction in tensile strength due to the paint baking process to the target 165 N / mm ² for the tensile strength after the paint baking process. Condition.

  Also, the bending workability of JISA3005P-H24 paint baking treatment plate, which is often used as a roofing material, is cracked in both the coating film and the substrate even if it is bent 180 ° with an inner bending radius of about 1.5 times the plate thickness. It is difficult, but if it is bent with an inner bending radius less than that, the coating film and the substrate may crack, and even if it is bent with an inner bending radius of 0.5 times the plate thickness, the coating film and substrate will be The target condition of the present invention was not to break.

  In addition, as for corrosion resistance, the neutral salt spray test using a scratched specimen is free of thread-like corrosion and pitting corrosion in 2000 hours, which is a general characteristic required for painted building materials including painted roofing materials. The invention also aimed at this property.

  Next, the manufacturing method of the aluminum alloy rolled sheet for painted roofing materials of this invention is demonstrated.

  The characteristics of the aluminum alloy rolled sheet for painted roofing material according to the present invention are characterized by the fact that the intermediate annealing is carried out in a continuous annealing furnace, the bending workability is improved by recrystallized grain refinement, and the cube orientation is appropriately controlled by the deep drawing ear. The desired strength, bending workability, and deep drawing ear rate are achieved by reducing the rate and further defining the final cold rolling rate after intermediate annealing in a small and narrow range.

  First, an aluminum alloy as described above is melted and cast by DC casting or the like according to a conventional method.

  The obtained ingot is subjected to homogenization treatment and then subjected to hot rolling, further subjected to primary cold rolling, then subjected to intermediate annealing, and finally subjected to final cold rolling to about 0.5 to 1.0 mm. Product thickness.

  Here, the homogenization treatment is performed at a temperature in the range of 450 to 630 ° C. for 1 to 24 hours. If the homogenization temperature is less than 450 ° C., homogenization is insufficient and the recrystallized grains during intermediate annealing become coarse and bending workability is poor. On the other hand, if the temperature exceeds 630 ° C., there is a possibility of melting. 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.

  Although hot rolling is started immediately after homogenization as described above, the hot rolling start temperature is set to 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, the end temperature of hot rolling shall be 300 degrees C or less. When the hot rolling finish temperature exceeds 300 ° C., partial recrystallization and complete recrystallization occur, the rolling strain in the primary cold rolling becomes insufficient, the recrystallized grains during intermediate annealing become coarse, and the bending workability deteriorates.

  The primary cold rolling performed after hot rolling is performed at a rolling rate of 30% or more. If the primary cold rolling rate is less than 30%, the cold strain is insufficient, the recrystallized grains during intermediate annealing become coarse, and the bending workability deteriorates.

  Further, as described above, the intermediate annealing performed after the primary cold rolling is not maintained at an annealing temperature of 400 to 630 ° C. in a continuous annealing furnace having an average heating rate and an average cooling rate of 3 ° C./sec to 50 ° C./sec, or Hold for 1 minute or less. If it is within the range of the conditions, the deep drawing ear ratio can be reduced by improving the bending workability by recrystallizing grains and controlling the cube orientation appropriately. When the annealing temperature is less than 400 ° C., recrystallization is insufficient and the strength is excessively improved, the bending workability is deteriorated, and the deep drawing ratio is deteriorated. On the other hand, if the annealing temperature exceeds 630 ° C, eutectic melting may occur, which is not preferable.

  The final cold rolling performed after the intermediate annealing is performed at a rolling rate of 15 to 30%. If the final cold rolling rate is less than 15%, the strength is insufficient, and if it exceeds 30%, the strength is excessively improved, the bending workability is deteriorated and the deep drawing ear rate is increased, which is not preferable.

  The alloys shown in Alloy Nos. 1 to 11 in Table 1 were melted by a conventional method and cast into ingots each having a thickness of 450 mm, a width of 1080 mm, and a length of 2800 mm by a DC casting method.

  The obtained ingots were combined with the conditions of production process numbers A to I in Table 2 to obtain final cold rolled sheets (coil shapes having a width of 1000 mm) of sample numbers 1A to 11B shown in Table 3, and then Was painted and baked to obtain a coated plate.

  There are various coating methods depending on the choice of degreasing treatment liquid, chemical conversion treatment liquid, and paint. As an example of a general method, degreasing treatment while rewinding the coil (sulfuric acid) → water washing → chemical conversion treatment (phosphate chromate) → Undercoat of polyester resin 5 μm on both sides → Baking process (215 ° C., no holding, temperature rise and cooling rate is about 10 ° C./sec) → Furthermore, one side is overcoated with polyester resin 15 μm, and the other side is polyester resin Top coating of 10 μm (surface to be used is the surface of 5 μm undercoat + 15 μm top coating) → baking process (215 ° C, no holding, temperature rise and cooling rate is about 10 ° C / sec) → leveling → cutting to a specified size It was done in.

  About each final cold-rolled board and a coated board, 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 coated plate in this case was determined after the paint was peeled off with sulfuric acid.

  Each coated plate was subjected to a 180 ° bending test with a JIS No. 3 bending test piece cut in a direction perpendicular to the rolling direction (a direction inferior in bendability). The 180 ° bending test is performed under the condition that the surface of the polyester resin 5 μm + polyester resin 15 μm faces the outside at an inner bend radius of 0.5 times the plate thickness. If neither the coating film nor the substrate was cracked, it was accepted (O), and the cracked material was rejected (X).

  Furthermore, the average crystal grain size of each coated plate is determined by mirror polishing of the rolled surface → anodic oxide film treatment with 1.8% borofluoric acid (18 ° C., DC 30 V × 90 seconds) → photographing of crystal grains with a deflection microscope ( Photo magnification: 200 times, photo size: 70 mm × 90 mm) → The crystal grain sizes in three directions (vertical, horizontal, diagonal) were determined by a cutting method and averaged.

  The deep drawing ratio of each painted plate was deep drawing under the conditions of blank diameter 62.0mmΦ, punch diameter 32.0mmΦ, clearance 20-40%, wrinkle presser pressure 250Kg (lubricating oil applied). Later, the ear rate was determined. Ear rate is expressed as a percentage (%) by dividing the difference between the average height of four ears (mm) and the average height of four valleys (mm) by the average value of four valley heights (mm). )

  Furthermore, the corrosion resistance of each coated plate is evaluated in accordance with the JIS Z 2371 salt spray test method. The test piece is prepared by scratching the surface of the polyester resin 5 μm + polyester resin 15 μm deep enough to reach the substrate (cross cut with a cutter knife). ) And a neutral salt spray test was conducted for 2000 hours. If no filiform corrosion or pitting corrosion occurred, the test was accepted (O), and if filiform corrosion or pitting corrosion occurred, the test was rejected (x).

  The respective results are also shown in Table 3.

In Table 3, the final cold-rolled plate and the coated plate of sample numbers 1A, 1B, 1C, 2B, and 3B are all invention examples that satisfy both the component composition and the manufacturing process that satisfy the conditions defined in the present invention. The tensile strength of the cold-rolled sheet is 175 N / mm ² or more, the tensile strength of the coated sheet after the coating baking process is as high as 165 N / mm ² or more, comparable to JIS A3005P-H24, and bending workability It is clear that the material is excellent in low ear rate and corrosion resistance.

  On the other hand, the final cold-rolled plates and painted plates of sample numbers 1D, 1E, 1F, 1G, 1H, and 1I are alloys that satisfy the component composition conditions defined in the present invention, but the manufacturing process conditions are defined in the present invention. This is a comparative example that deviates from the conditions to be performed.

In 1D, since the amount of hot rolling oil injected was small, cooling became insufficient, the hot rolling finish temperature increased, and recrystallization occurred, and the recrystallization grains during intermediate annealing were coarse due to insufficient rolling strain in primary cold rolling. As a result, the bendability of the coated plate has deteriorated.
In addition, since the primary cold rolling rate of 1E was insufficient, the recrystallized grains became coarse by intermediate annealing, and the bending workability of the coated plate was deteriorated.
Furthermore, 1F has an intermediate annealing temperature that is too low, so recrystallization is insufficient (non-recrystallized structure), the strength of the coated plate is improved too much, the bending workability is deteriorated, and the deep drawing ratio is also deteriorated. It was.
Further, 1G had batch annealing, so that the recrystallized grains were coarsened, the bendability of the coated plate was deteriorated, and the deep drawing ear rate was deteriorated to be higher.
Furthermore, since the final cold rolling rate was insufficient for 1H, the tensile strength of the final cold rolled sheet and the coated sheet was lowered.
Furthermore, since the final cold rolling rate of 1I was too high, the tensile strength of the final cold rolled sheet and the coated sheet was improved so that the bending workability deteriorated.

  Furthermore, although the final cold-rolled plate and the coated plate of sample numbers 4B to 11B satisfy the manufacturing process conditions defined in the present invention, they are comparative examples that do not satisfy the component composition conditions.

4B had too much Mn, so the size of the Al—Mn—Fe intermetallic compound was too large, 8B had too much Si, and the size of the Al—Si intermetallic compound, and 9B had too much Fe, so that Al— The size of the Fe—Mn intermetallic compound increased, and the bending workability deteriorated.
In addition, since the amount of Mg in 6B was too large, the work hardenability increased and the bending workability deteriorated.
The amount of Mn in 5B and the amount of Mg in 7B were too small, so the tensile strength of the final cold-rolled plate and the coated plate was lowered.
In addition, since 10B had too much Cu, thread corrosion occurred in the salt spray test, and 11B had too much Zn, resulting in pitting corrosion, and the corrosion resistance of both deteriorated.

Claims (3)

Mn 1.0-1.5% (mass%, the same shall apply hereinafter), Mg 0.2-0.6%, Si 0 . 18 to 0.6%, Fe 0.7% or less, Cu 0.30% or less, Zn 0.25% or less, the balance is made of Al and inevitable impurities, and the tensile strength of the final cold rolled sheet and the strength of 175 N / mm ² or more, a tensile strength after paint baking at 220 ° C. or less 165 N / mm ² or more, the average crystal grain size 30μm or less, or less deep drawing ears 6% An aluminum alloy rolled sheet for painted roofing materials with excellent strength, bending workability and low ear coverage. Furthermore, the aluminum alloy rolled sheet for coating roof materials of Claim 1 containing Ti0.005-0.10% and B0.0001-0.01%. The ingot of the aluminum alloy having the chemical composition according to claim 1 or 2 is subjected to a homogenization treatment at a temperature in a range of 450 to 630 ° C for 1 to 24 hours, and then hot rolling is performed at a temperature of 400 ° C or more. After starting and finishing at 300 ° C. or less, and further performing primary cold rolling at a rolling rate of 30% or more, the annealing temperature is 400 in a continuous annealing furnace having an average heating rate and an average cooling rate of 3 to 50 ° C./sec. -Hold at 630 ° C, or perform intermediate annealing for 1 minute or less, and finally perform cold rolling at a rolling rate of 15-30%, whereby the tensile strength of the final cold rolled sheet is 175 N / mm ² or more Strength and bending workability, characterized in that the tensile strength after the baking treatment at 220 ° C. or less is 165 N / mm 2 or more, the average crystal grain size is 30 μm or less, and the deep drawing ear ratio is 6% or less. For painted roofing material with excellent low ear rate Method for producing aluminum alloy rolled sheet.