WO2017170835A1 - Aluminum alloy sheet and aluminum alloy sheet manufacturing method - Google Patents

Aluminum alloy sheet and aluminum alloy sheet manufacturing method Download PDF

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Publication number
WO2017170835A1
WO2017170835A1 PCT/JP2017/013179 JP2017013179W WO2017170835A1 WO 2017170835 A1 WO2017170835 A1 WO 2017170835A1 JP 2017013179 W JP2017013179 W JP 2017013179W WO 2017170835 A1 WO2017170835 A1 WO 2017170835A1
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Prior art keywords
aluminum alloy
temperature
height
treatment
temperature range
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PCT/JP2017/013179
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French (fr)
Japanese (ja)
Inventor
久郎 宍戸
智之 北村
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株式会社神戸製鋼所
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Priority claimed from JP2016213789A external-priority patent/JP6306123B2/en
Application filed by 株式会社神戸製鋼所 filed Critical 株式会社神戸製鋼所
Priority to US16/088,679 priority Critical patent/US20190127825A1/en
Priority to CN201780016619.3A priority patent/CN108884524B/en
Priority to EP17775369.6A priority patent/EP3438302A4/en
Publication of WO2017170835A1 publication Critical patent/WO2017170835A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/05—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys of the Al-Si-Mg type, i.e. containing silicon and magnesium in approximately equal proportions
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working

Definitions

  • the present invention relates to a 6000 series aluminum alloy plate produced by ordinary rolling and having excellent formability and bake coating curability.
  • panels such as hoods, fenders, doors, roofs, trunk lids, etc., such as outer panels (outer plates) and inner panels (inner plates), are thin and high-strength aluminum alloy plates.
  • Al-Mg-Si based AA to JIS6000 (hereinafter also simply referred to as 6000) aluminum alloy plates are used.
  • This 6000 series (Al-Mg-Si series) aluminum alloy sheet contains Si and Mg as essential components, and especially the excess Si type 6000 series aluminum alloy has excellent age hardening ability during artificial aging treatment. .
  • the moldability is ensured by reducing the yield strength, and even with relatively low-temperature artificial aging treatment such as paint baking treatment of the panel after molding, the yield strength is improved, and as a panel
  • an outer panel of an automobile is manufactured by combining an aluminum alloy plate with a forming process such as an extension forming in a press forming or a bending forming.
  • a forming process such as an extension forming in a press forming or a bending forming.
  • a large outer panel such as a hood or a door is formed into a molded product shape as an outer panel by press molding such as overhanging, and then an inner panel is formed by hem (hemming) processing such as a flat hem at the outer peripheral edge of the outer panel.
  • hem hem
  • the exothermic peak height W1 in the temperature range of 100 to 200 ° C. is 50 ⁇ W or more, and the exotherm in the temperature range of 200 to 300 ° C.
  • the ratio between the peak height W2 and the exothermic peak height W1, W2 / W1 is defined to be 20 or less.
  • the exothermic peak height in the temperature range of 230 to 270 ° C. in the differential scanning calorimetry curve is A
  • the exothermic peak in the temperature range of 280 to 320 ° C is B
  • the exothermic peak height B is not less than 20 ⁇ W / mg
  • the exothermic peak height relative to the exothermic peak height B is The ratios of A and C are respectively defined as A / B of 0.45 or less and C / B of 0.6 or less.
  • a differential scanning calorimetry curve of a 6000 series aluminum alloy plate having a total amount of Mg and Si of 1.2% or less has an exothermic peak within a temperature range of 230 to 330 ° C. There are only two exothermic peaks having a temperature difference between the peaks of 50 ° C. or less, the height of the only one exothermic peak, or the only one of the two exothermic peaks. It defines that the exothermic peak height of the larger peak height is in the range of 20-50 ⁇ W / mg.
  • an endothermic peak in the temperature range of 150 to 230 ° C. as an endothermic peak corresponding to dissolution of Mg—Si clusters in a differential scanning calorimetry curve of a 6000 series aluminum alloy plate that requires Sn addition.
  • the peak height of the exothermic peak in the temperature range of 240 to 255 ° C. is the exothermic peak corresponding to the formation of the Mg—Si cluster, while the peak height of is 8 ⁇ W / mg or less (including 0 ⁇ W / mg). Is 20 ⁇ W / mg or more.
  • Patent Document 5 in a differential scanning calorimetry curve after tempering treatment including solution treatment and quenching treatment of an aluminum alloy material, in a temperature range of 150 to 250 ° C. corresponding to dissolution of Si / vacancy clusters (GPI).
  • the negative endothermic peak height is set to 1000 ⁇ W or less
  • the positive exothermic peak height in the temperature range of 250 to 300 ° C. corresponding to the precipitation of Mg / Si clusters (GPII) is set to 2000 ⁇ W or less
  • room temperature aging suppression and low temperature aging hardening ability are achieved. It is described that it is made excellent.
  • these conventional DSC endothermic peak and exothermic peak control techniques are intended to obtain high BH properties in response to the baking coating curing process for reducing the temperature and time of the automobile parts.
  • the heating temperature is 175 ° C. at the highest, and 150 ° C. in the low example.
  • the BH property in the baking finish hardening process at a high temperature such as 180 ° C. or higher is not intended. Therefore, in such a high temperature baking coating hardening process, it is still an improvement to have a good formability and high BH properties in an Al-Mg-Si aluminum alloy sheet after long-term aging at room temperature. There was room for.
  • the object of the present invention is to provide the conventional low-temperature baking coating curing, as well as good moldability and baking coating curing treatment at the high temperature, even after prolonged aging at room temperature. It is to provide a 6000 series aluminum alloy plate and a method for producing the same that can have high BH properties in processing.
  • the gist of the aluminum alloy plate excellent in formability and bake hardenability of the present invention is, by mass%, Mg: 0.3 to 1.5%, Si: 0.6 to 1 .5%, and the total of Mg content and Si content is more than 1.2%, and the balance is an aluminum alloy plate made of Al and unavoidable impurities.
  • an endothermic peak having a height A of 3 to 10 ⁇ W / mg exists in a temperature range of 150 to 230 ° C., and a height B of 20 to 20 in a temperature range of 230 ° C. or more and less than 330 ° C.
  • An exothermic peak of 50 ⁇ W / mg is present, and the ratio B / A of the maximum peak height B in the exothermic peak to the maximum peak height A in the endothermic peak is more than 3.5; It shall be less than 0.
  • the gist of the method for producing an aluminum alloy plate excellent in formability and bake hardenability of the present invention is mass%, Mg: 0.3 to 1.5%, Si: An aluminum alloy cold-rolled sheet containing 0.6 to 1.5% each, the total of the Mg content and the Si content is more than 1.2%, the balance being Al and inevitable impurities,
  • pre-aging treatment is performed at a temperature range of 30 ° C. to 60 ° C. for 5 hours or more and 500 hours or less.
  • an endothermic peak having a height A of 3 to 10 ⁇ W / mg is present in a temperature range of 150 to 230 ° C.
  • a height B is in a temperature range of 230 ° C. or more and less than 330 ° C.
  • Fever of 20-50 ⁇ W / mg A peak is present, and the ratio B / A between the exothermic peak height B and the endothermic peak height A is more than 3.5 and less than 15.0.
  • the present inventors have good moldability and high BH property even in the conventional low-temperature baking coating curing treatment as well as the high-temperature baking coating curing treatment, even after prolonged room temperature aging.
  • more than a certain number of clusters corresponding to the endothermic peak of the suggested heat curve within the temperature range of 150 to 230 ° C is necessary. did.
  • the baking temperature in the baking coating curing process varies greatly from high temperature to low temperature, in order to obtain a high BH amount at any baking temperature, the number of clusters corresponding to the endothermic peak of the suggested heat curve is reduced.
  • the differential thermal curve for obtaining high BH properties varies depending on the temperature especially in the baking coating curing conditions (artificial aging treatment conditions), and at a relatively low baking coating temperature of 175 ° C. or lower, 180 ° C. or higher. It was also found that it is necessary to control the differential heat curve more precisely than the relatively high baking coating temperature.
  • the present invention performs structure control to control the differential heat curve more precisely, and it can be said that the 6000 series aluminum alloy plates as materials for automobile members are mutually contradictory. Both have low-temperature BH properties.
  • the aluminum alloy plate (molding material plate) referred to in the present invention is a rolled plate such as a hot rolled plate or a cold rolled plate, and is subjected to tempering (T4) such as solution treatment and quenching treatment. It is a raw material aluminum alloy plate before being formed into an automobile member to be used and before being subjected to artificial aging treatment (artificial age hardening treatment) such as paint baking hardening treatment.
  • T4 tempering
  • It is a raw material aluminum alloy plate before being formed into an automobile member to be used and before being subjected to artificial aging treatment (artificial age hardening treatment) such as paint baking hardening treatment.
  • artificial age hardening treatment artificial age hardening treatment
  • paint baking hardening treatment paint baking hardening treatment.
  • aluminum is also referred to as aluminum or Al.
  • Aluminum alloy composition First, the chemical component composition of the aluminum alloy sheet of the present invention will be described below, including reasons for limiting each element. In addition,% display of content of each element means the mass% altogether.
  • the chemical component composition of the aluminum alloy plate of the present invention is determined so as to satisfy the required formability and bake hardenability from the composition of the 6000 series aluminum alloy as a material of an automobile member such as the automobile large body panel.
  • the chemical composition of the aluminum alloy sheet of the present invention includes, in mass%, Mg: 0.3 to 1.5% and Si: 0.6 to 1.5%, respectively, and the Mg content. And the Si content are over 1.2%, and the balance consists of Al and inevitable impurities.
  • Cu 0.02 to 0.8%
  • Fe 0.05 to 0.5%
  • Mn 0.05 to 0.3%
  • Zr 0.04 to 0.1%
  • V 0.02 to 0.1%
  • Ag 0.01 to 0.1%
  • Zn 0.01 to 0.3% The above may be included.
  • Si 0.6 to 1.5% Si, together with Mg, forms aging precipitates such as Mg-Si-based precipitates that contribute to strength improvement during solid solution strengthening and artificial aging treatment such as baking coating treatment, and exhibits age-hardening ability. It is an essential element for obtaining strength (yield strength). If the Si content is too small, the amount of solute Si before baking coating treatment (before artificial aging heat treatment) will decrease, and the amount of Mg-Si-based precipitates will be insufficient, resulting in a marked decrease in BH properties and strength. Run short.
  • the Si content is in the range of 0.6 to 1.5%, preferably in the range of 0.7 to 1.5%.
  • Mg 0.3-1.5% Mg and Si, together with solid solution strengthening, form aging precipitates such as Mg-Si-based precipitates that contribute to strength improvement during artificial aging heat treatment such as baking coating treatment, and show age-hardening ability. It is an essential element for obtaining strength. If the Mg content is too small, the amount of solid solution Mg before baking coating treatment is reduced, and the amount of Mg—Si based precipitates is insufficient, so that the BH property is remarkably lowered and the strength is insufficient. On the other hand, when there is too much Mg content, it will become easy to form a shear band at the time of cold rolling, and will cause the crack at the time of a raw material plate rolling. Therefore, the Mg content is in the range of 0.3 to 1.5%, preferably in the range of 0.4 to 0.8%.
  • the total of the Mg content and the Si content is over 1.2%.
  • the total is 1.2% or less as in Patent Document 3, even if the production conditions of the board are within a preferable range described later, an endothermic peak or an exothermic peak defined in the present invention cannot be generated, Artificial age-hardening ability is insufficient, and the required strength cannot be obtained.
  • the upper limit of the total of the Mg content and the Si content is determined by the limit at which the plate can be produced without causing hot rolling cracking, and is preferably 2.5%.
  • Cu can improve strength by solid solution strengthening. If the Cu content is too small, the effect is small, and if it is too much, the effect is saturated, and on the contrary, the corrosion resistance is deteriorated.
  • Fe forms a crystallized product, serves as a nucleus of recrystallized grains, prevents coarsening of crystal grains, and plays a role of improving strength. If the content is too small, the effect is small. If the content is too large, a coarse compound is formed, which becomes a starting point of destruction, and the strength and formability are lowered.
  • Mn, Zr, Cr, V contributes to strength improvement by refining the crystal grains of the ingot and final plate product. Further, these elements exist as dispersed particles, contribute to crystal grain refinement, and improve moldability. When each content is too small, the effect of improving strength and formability due to the refinement of crystal grains is insufficient. On the other hand, when there are too many of these elements, a coarse compound will be formed and ductility will deteriorate.
  • Ag has the effect of closely and finely precipitating aging precipitates that contribute to strength improvement by artificial aging heat treatment after molding of automobile parts, thereby promoting high strength. If the content is too small, the effect of improving the strength is small, and if the content is too large, various properties such as rollability and weldability are reduced, and the effect of improving the strength is saturated and expensive.
  • Zn is useful for improving artificial age-hardening ability (BH property), and has an effect of increasing the strength by promoting precipitation of a compound phase such as a GP zone in the crystal grains of the plate structure in the baking coating process. .
  • Ti and B are inevitable impurities. Ti, together with B, forms a coarse compound and degrades mechanical properties. However, since the inclusion of a small amount also has the effect of refining the crystal grains of the aluminum alloy ingot, each content in the range specified by the JIS standard is allowed as a 6000 series alloy. As an example of this allowable amount, Ti is 0.1% or less, preferably 0.05% or less. Further, B is set to 0.03% or less. Incidentally, in the present invention, Sn, which is essential in Patent Document 4, is not added.
  • the Mg-Si clusters are reduced on the contrary when the preferable production conditions for the plate are described later, the endothermic peak and the exothermic peak defined in the present invention cannot be generated, and the artificial age hardening ability is insufficient. As a result, the required strength may not be obtained.
  • the structure of an aluminum alloy plate is used as an index indicating in advance the state of artificial aging precipitates in a member made of this plate, and DSC obtained by differential scanning calorimetry ( Differential scanning calorimetry curve: DSC profile).
  • DSC differential scanning calorimetry curve: DSC profile
  • the present invention is capable of baking at a relatively low temperature as well as good formability and high BH property in a relatively high temperature baking coating curing process, which is the main target, even after prolonged room temperature aging.
  • DSC differential scanning thermal analysis curve: DSC profile
  • the clusters corresponding to the endothermic peaks are dissolved in an extremely short time, and then a strengthening phase is easily generated. It is presumed that even if a peak is present in advance, a high BH property can be obtained. For this reason, the endothermic peak can be increased under the relatively high temperature baking finish curing conditions targeted by the present invention, and the work curability can be enhanced by the presence of clusters corresponding to the endothermic peak. Therefore, if there is also an exothermic peak in the temperature range of 230 ° C. or higher and lower than 330 ° C. that enhances BH properties, both high work curability (formability) and BH properties can be achieved.
  • This relatively high temperature baking coating curing treatment condition means, for example, that the baking coating curing treatment is performed under the conditions of a heating temperature of 180 to 230 ° C. and a heating holding time of 10 to 30 minutes.
  • the heating temperature of the baking coating curing process is distinguished from at most 175 ° C. in particular at the heating temperature.
  • the balance between the peak heights as well as the respective peak heights is important. For example, when the ratio of the exothermic peak / endothermic peak is too small, the existence of clusters corresponding to the endothermic peak is too large and the BH property is too low, or the exothermic peak is too low and there are too many clusters that become the reinforcing phase. , Elongation will decrease. On the other hand, if the exothermic peak / endothermic peak is too large, the presence of clusters corresponding to the endothermic peak is too small and the work hardenability is inferior, or the exothermic peak is too high and there are too few clusters that become the reinforcing phase. Is too low.
  • the DSC before artificial aging treatment of the aluminum alloy sheet is within a temperature range of 150 to 230 ° C.
  • An endothermic peak having a height A of 3 to 10 ⁇ W / mg is present, and an exothermic peak having a height B of 20 to 50 ⁇ W / mg is present in a temperature range of 230 ° C. or higher and lower than 330 ° C., and
  • the ratio B / A between the exothermic peak height B and the endothermic peak height A is more than 3.5 and less than 15.0.
  • a peak is present, and the ratio B / A between the exothermic peak height B and the endothermic peak height A is more than 3.5 and less than 15.0. More preferably, the endothermic peak height A is 3 to 7 ⁇ W / mg, and the exothermic peak height B is 20 to 35 ⁇ W / mg.
  • the fact that the endothermic peak is high on the minus side means that the cluster is dissolved during the differential thermal analysis, in other words, there are many clusters corresponding to the endothermic peak.
  • the negative peak height A is as low as less than 3 ⁇ W / mg, the work curability is lowered and the moldability is lowered.
  • the negative peak height A is too high exceeding 10 ⁇ W / mg, the relatively high-temperature BH property decreases, and if it exceeds 7 ⁇ W / mg, the relatively low-temperature BH is decreased. The nature will decline.
  • a high exothermic peak means that many clusters that are the core of the reinforcing phase or the reinforcing phase are generated during the differential thermal analysis, in other words, the strengthening phase or the strengthening phase. This means that there are few core clusters. If the positive peak height B exceeds 50 ⁇ W / mg, the reinforcing phase or the core of the reinforcing phase is too few, and the BH property of baking coating curing at a relatively high temperature becomes low, resulting in 40 ⁇ W. If it exceeds / mg and is too high, the BH property of baking coating curing at a relatively low temperature will be low.
  • the structure defined by DSC at the stage of the material plate is very much affected by the generation behavior of the precipitated phase during the artificial aging treatment (at the time of BH) of the member such as the automobile panel manufactured from the material plate. There is a good correlation. As a result, it is possible to evaluate the formability and BH property of the material plate by controlling the DSC at the stage of the material plate without bothering manufacturing the member.
  • the structure defined by the DSC at the stage of the material plate can be an index of formability and BH property in a member using the material plate as a molding material.
  • Patent Document 1 there is no endothermic peak having a height of 3 to 10 ⁇ W / mg in the temperature range of 150 to 230 ° C., and conversely, an exothermic peak is present in the temperature range of 100 to 200 ° C.
  • Patent Document 2 as shown in FIG. 1, there is no endothermic peak having a height of 3 to 10 ⁇ W / mg within a temperature range of 150 to 230 ° C.
  • Patent Document 3 the total amount of Mg and Si is 1.2% or less, the endothermic peak and the exothermic peak defined in the present invention cannot be generated, the artificial age hardening ability is insufficient, and the necessary strength is obtained. It becomes impossible.
  • Patent Document 4 as shown in FIG.
  • the conventional DSC endothermic peak and exothermic peak control technique is different from the DSC endothermic peak and exothermic peak defined in the present invention.
  • the high elongation (formability) and bake coating curability of the 6000 series aluminum alloy plate after long-term aging at room temperature cannot be achieved.
  • Control of the structure specified by the DSC exothermic peak is performed as follows.
  • the aluminum alloy cold-rolled sheet is heated within a temperature range of 30 ° C. to 60 ° C. for 5 hours or more, 500 hours or less within 1 hour after solution treatment and quenching treatment.
  • Preliminary aging treatment at a low temperature for a long time is performed. Further, in order to increase the BH property at a relatively low temperature, as will be described later, it is maintained within a temperature range of 100 ° C. to 300 ° C. for 5 seconds or more and 300 seconds or less within 1 hour after the solution treatment and quenching treatment.
  • the preliminary aging treatment is performed. For this reason, there is an advantage that it can be controlled without greatly changing the composition of the 6000 series aluminum alloy already standardized as the automobile member of the rolled plate and without greatly changing the rolling process by a conventional method.
  • the 6000 series aluminum alloy sheet of the present invention is a cold-rolled sheet obtained by subjecting an ingot to hot rolling after soaking and then cold rolling, and further subjected to tempering such as solution treatment. Manufactured. That is, an aluminum alloy hot rolled sheet having a thickness of about 2 to 10 mm is manufactured through normal manufacturing processes such as casting, homogenization heat treatment, and hot rolling. Subsequently, it is cold-rolled to obtain a cold-rolled sheet having a thickness of 3 mm or less.
  • an ordinary molten casting method such as a continuous casting method and a semi-continuous casting method (DC casting method) is appropriately selected for the molten aluminum alloy adjusted to be dissolved within the above-mentioned 6000 series component composition range.
  • the average cooling rate at the time of casting is as large as possible (fast) from the liquidus temperature to the solidus temperature of 30 ° C./min. Is preferred.
  • the cooling rate in this high temperature region is inevitably slow.
  • the cast aluminum alloy ingot is subjected to a homogenization heat treatment prior to hot rolling.
  • This homogenization heat treatment (uniform heat treatment) is important for sufficiently dissolving Si and Mg in addition to the normal purpose of homogenizing the structure (eliminating segregation in crystal grains in the ingot structure). It is.
  • the homogenization heat treatment temperature is 500 ° C. or more and 580 ° C. or less, and the homogenization (retention) time is appropriately selected from a range of 1 hour or more to sufficiently dissolve Si and Mg. If the homogenization temperature is low, the solid solution amount of Si and Mg cannot be secured, and the DSC exothermic peak can be defined by the pre-aging treatment (reheating treatment) after the solution treatment and quenching treatment described later. Disappear. Further, segregation in the crystal grains cannot be sufficiently eliminated, and this acts as a starting point of fracture, so that formability is lowered.
  • the temperature of the ingot is not lowered to 450 ° C. or lower without lowering the temperature of the ingot. It is preferable to ensure the amount of solution.
  • Si and Mg are likely to precipitate, and there is a high possibility that the solid solution amount of Si and Mg cannot be secured for the purpose of the DSC. Become.
  • Hot rolling is composed of a rough rolling process of an ingot (slab) and a finish rolling process according to the thickness of the sheet to be rolled.
  • a reverse or tandem rolling mill is appropriately used.
  • hot finish rolling with an end temperature in the range of 250 to 360 ° C. is performed. If the soaking temperature or the finishing temperature of this finish rolling is too low, Mg and Si compounds are generated during soaking and hot rolling, and the balance of solid solution Mg / Si changes, It becomes difficult to make the DSC regulation.
  • Hot rolled sheet annealing Annealing of the hot-rolled sheet before cold rolling is not necessary, but may be performed.
  • Cold rolling In the cold rolling, the hot-rolled sheet is rolled to produce a cold-rolled sheet (including a coil) having a desired final thickness.
  • the cold rolling rate is desirably 60% or more, and intermediate annealing may be performed between cold rolling passes for the same purpose as the annealing.
  • the average cooling rate from the solution temperature to the quenching stop temperature at room temperature is desirably 20 ° C./s or more. If the average cooling rate of the quenching treatment to room temperature after the solution treatment is small, coarse Mg 2 Si and simple substance Si are generated during cooling, and bending workability is deteriorated. Moreover, the amount of solid solution after solution forming falls, and BH property will fall. In order to ensure this cooling rate, the quenching treatment is performed by selecting water cooling means and conditions such as air cooling such as a fan, mist, spray, and immersion, respectively.
  • Preliminary aging treatment reheating treatment
  • reheating treatment After such a solution treatment, it is preferable to quench the steel sheet and cool it to room temperature, and then subject the cold-rolled sheet to a pre-aging treatment (reheating treatment) within one hour.
  • This preliminary aging treatment is held at a temperature range of 30 ° C. to 60 ° C. for 5 hours or more and 500 hours or less as a lower temperature and longer time than the conventional method for the control of the structure specified by the DSC peak.
  • Mg—Si clusters with a good balance between Mg and Si are formed, and the structure specified by the DSC peak is obtained. Therefore, the high aging and the BH property at a relatively high temperature can be combined by the low-temperature long-time preliminary aging treatment.
  • the solution treatment and quenching treatment and the reheating treatment may be continued so that there is almost no time difference, and the lower limit time is not particularly set.
  • the preliminary aging temperature is less than 30 ° C. or the holding time is less than 5 hours, as in the case where this preliminary aging treatment is not performed, too many clusters corresponding to endothermic peaks are generated, BH property tends to be low.
  • the pre-aging condition exceeds 60 ° C. or exceeds 500 hours, the amount of clusters that form the core of the strengthening phase and the strengthening phase corresponding to the exothermic peak is too much, and the press before baking coating. The strength at the time of molding becomes too high, and the moldability tends to deteriorate.
  • the temperature is maintained at a temperature range of 100 ° C. to 300 ° C. for 5 seconds or more and 300 seconds or less. It is preferable to perform the preliminary aging treatment for a long time at a low temperature and immediately after the preliminary aging treatment for a short time at a high temperature.
  • the DSC can be reliably controlled by the low-temperature long-time pre-aging treatment, and the endothermic peak height A in the temperature range of 150 to 230 ° C. in the DSC is more preferably in the range of 3 to 8 ⁇ W / mg. The preferred range is 3 to 7 ⁇ W / mg.
  • the height B of the exothermic peak in the temperature range of 230 ° C. or higher and lower than 330 ° C. in DSC can be controlled to be a preferable range of 20 to 40 ⁇ W / mg, and a more preferable range of 20 to 35 ⁇ W / mg. If this high temperature and short time pre-aging treatment is not performed or if the above conditions are not met, the structure specified by the DSC peak may not be obtained or the structure may be relatively low. There is a possibility that the BH property of the resin becomes low.
  • the aluminum alloy plate of the present invention manufactured with the structure specified by the DSC peak is press-molded as a material on a large body panel or the like of an automobile and then baked after being painted.
  • the coating is hardened (artificial aging treatment) to increase the strength.
  • the baking coating curing treatment is preferably performed at a higher temperature in order to achieve the effects of the present invention, and examples include conditions of a heating temperature of 180 to 230 ° C. and a heating and holding time of 10 to 30 minutes. If the heating temperature is too low, for example, if the heating temperature is too low, the structure indicated by the differential heat curve needs to be more precisely controlled as described above.
  • 6000 series aluminum alloy plates having different structures defined by the DSC of the present invention were produced by making different compositions and production conditions. And after Assembling the board, after holding at room temperature for 100 days, As proof strength (proof strength before baking coating hardening treatment), AB proof strength (proof strength after baking coating hardening treatment), elongation at break, BH property (paint bake hardening property), respectively Measurement and evaluation. These results are shown in Tables 1 and 2.
  • the above-described method of making the samples was carried out by changing the pre-aging treatment conditions of the 6000 series aluminum alloy plate having the composition shown in Table 1 after solution treatment and quenching treatment as shown in Table 2.
  • the display of the content of each element in Table 1 the display in which the numerical value of each element is blank indicates that the content is below the detection limit.
  • the specific production conditions of the aluminum alloy plate were the same (same) as follows in each example except for the preliminary aging treatment conditions.
  • Aluminum alloy ingots having respective compositions shown in Table 1 were commonly melted by DC casting.
  • the average cooling rate during casting was set to 50 ° C./min from the liquidus temperature to the solidus temperature.
  • the ingot after chamfering as necessary is subjected to a soaking treatment at 550 ° C. for 10 hours, and then hot rough rolling is started at that temperature, and then the end temperature is set to 250 to 360 ° C.
  • a hot finish rolling was performed to obtain a hot rolled sheet.
  • This hot-rolled sheet was cold-rolled at a processing rate of 67% to obtain a cold-rolled sheet having a thickness of 1.0 mm.
  • each cold-rolled plate was subjected to a solution treatment for 1 minute at 550 ° C. using a glass furnace, and then cooled to room temperature by water cooling. Within 1 hour after this cooling, high temperature short time pre-aging using an oil bath and low temperature long time pre-aging using an atmospheric furnace are performed at the temperature (° C) and holding time (hr) shown in Table 2. After the preliminary aging treatment, air cooling was performed.
  • test plate 300 mm ⁇ 300 mm was cut out from the longitudinal end portion and the width center portion of the product, and the DSC of each test plate was cut. And properties were measured and evaluated. These results are shown in Table 2.
  • test equipment TG / DTA6300 manufactured by Seiko Instruments
  • standard material aluminum
  • sample container aluminum
  • temperature rise condition 10 ° C./min
  • atmosphere argon (50 ml / min)
  • sample weight 39.0 to 41.0 mg
  • the obtained differential thermal analysis profile ( ⁇ W) was divided by the sample weight ( ⁇ W / mg), and then the differential heat In the section of 0 to 100 ° C. in the analysis profile, the region where the profile of differential thermal analysis was horizontal was taken as a reference level of 0, and the endothermic peak height and exothermic peak height from this reference level were measured.
  • Paint bake hardenability As mechanical properties of the test plate, 0.2% yield strength (As yield strength) and elongation at break (%) were determined by a tensile test. In addition, each of these test plates is commonly used, and after 2% stretching simulating press molding on the automobile member, the coating baking and curing treatment at high temperature is 185 ° C. ⁇ 20 minutes, and the coating is performed at low temperature. The 0.2% yield strength (AB yield) of the test plate after each artificial age hardening treatment (after BH) of 170 ° C. ⁇ 20 minutes as the bake hardening treatment was determined by a tensile test.
  • AB yield 0.2% yield strength
  • the 0.2% proof stress after BH which evaluated the BH property of each test plate from the difference (increased proof stress) between these 0.2% proof stresses is the baking baking hardening process (185 degreeC * 20 at high temperature). 190) or more at a low temperature, and at least 170 MPa or more, preferably at 180 MPa or more, at a low temperature in a paint bake hardening process at a low temperature (170 ° C. ⁇ 20 minutes). It was. Note that the elongation at break, which is the evaluation of press formability, is only 1% difference between 24% and 25%. For example, corners and character lines with sharpened or complicated outer panel shapes of automobiles are distorted. It has a great influence on whether or not it can be molded with a beautiful and sharp curved surface structure without wrinkles.
  • No. 13A test piece (20 mm ⁇ 80 mmGL ⁇ plate thickness) of JISZ2201 was sampled from each test plate, and a tensile test was performed at room temperature.
  • the tensile direction of the test piece at this time was the direction perpendicular 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.
  • the test piece for measuring the yield strength after BH was subjected to the BH treatment after giving a pre-strain of 2% to the test piece by the tensile tester.
  • Invention Examples 1 to 8 are produced in the component composition range of the present invention and in a preferable condition range, and subjected to a pre-aging treatment at a low temperature for a long time in the preferable range. Therefore, as shown in Table 2, these invention examples are as defined by DSC in the present invention. Even after long-term room temperature aging, as shown in Table 2, the moldability and BH properties are excellent. ing. Specifically, it has a high elongation at break of at least 26%, a BH property of at least 192 MPa or higher (185 ° C. ⁇ 20 minutes), and a BH property of at least 162 MPa or more (170 ° C. ⁇ 20 minutes). have.
  • the inventive example 2 which was immediately subjected to the low temperature and the long time preliminary aging treatment was subjected to the preliminary aging treatment at a high temperature and a short time.
  • the BH property at a relatively low temperature is higher than that of Invention Example 1 in which only the preliminary aging treatment at a low temperature and a long time was performed without applying.
  • the invention examples 6, 7, and 8 that were subjected to the pre-aging treatment for a short time at a high temperature and immediately subjected to the pre-aging treatment for a long time at a low temperature were not subjected to the pre-aging treatment for a short time at a high temperature.
  • the BH property at a relatively low temperature is high on average although it depends on the difference in the alloy composition.
  • the invention examples 2, 6, 7, and 8 further added a pre-aging treatment at high temperature and short time, so that the endothermic peak height A in the temperature range of 150 to 230 ° C. in DSC is within a preferable range (3 ⁇ 8 ⁇ W / mg), more preferable range (3 to 7 ⁇ W / mg), and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. in DSC is also preferable range (20 to 40 ⁇ W / mg) In addition, it is because it can be controlled more precisely within a more preferable range (20 to 35 ⁇ W / mg).
  • Comparative Examples 1 to 6 in Table 2 use the same alloy example 1 as the invention example.
  • the production conditions such as the temperature of the preliminary aging treatment and the holding time are out of the preferable conditions.
  • DSC deviates from the range defined in the present invention, and either BH property or formability after long-term aging at room temperature is inferior to that of Invention Example 1 having the same alloy composition, and can be combined.
  • the elongation at break is 26% or more, the BH property at a high temperature (185 ° C. ⁇ 20 minutes) is less than 190 MPa, or the BH property at a high temperature (185 ° C. ⁇ 20 minutes) is 190 MPa or more.
  • the elongation at break is less than 25%, which does not satisfy the above acceptance criteria.
  • Comparative Example 1 is not subjected to preliminary aging treatment. Therefore, although an endothermic peak exists in the temperature range of 150 to 230 ° C., the height A is too high exceeding 10 ⁇ W / mg, and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. Is too high, exceeding 50 ⁇ W / mg. In Comparative Example 2, the time for the preliminary aging treatment on the low temperature side is too short. Therefore, although an endothermic peak exists in the temperature range of 150 to 230 ° C., the height A is too high exceeding 10 ⁇ W / mg, and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C.
  • Comparative Examples 7 and 8 in Table 2 are manufactured in a preferable range including the pre-aging conditions, Alloy Nos. 7 and 8 in Table 1 are used, respectively, and the alloy compositions are out of the scope of the present invention. ing. For this reason, as shown in Table 2, these comparative examples, as a result, DSC and the like are out of the range defined in the present invention. Either is inferior and cannot be combined. Specifically, even when the elongation at break is 25% or more, the BH property at a high temperature (185 ° C. ⁇ 20 minutes) is about 138 to 146 MPa, and the BH property at a low temperature (170 ° C. ⁇ 20 minutes) is 133- Only about 139 MPa.
  • the comparative example 7 is the alloy 7 of Table 1, and there is too little Mg and the quantity of the total content of Mg and Si is also too small. For this reason, although an endothermic peak exists in the temperature range of 150 to 230 ° C., the height A is too low as less than 3 ⁇ W / mg, and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. is also It is too low, less than 20 ⁇ W / mg.
  • the comparative example 8 is the alloy 8 of Table 1, Si is too little, and the total content of Mg and Si is too little.
  • the height A is too low as less than 3 ⁇ W / mg
  • the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. is also It is too low, less than 20 ⁇ W / mg.
  • FIG. 1 The DSC selected from these invention examples and comparative examples is shown in FIG.
  • the unit of the vertical axis indicated as “Heat Flow” is ⁇ W / m
  • the thick solid line indicates Invention Example 1 in Table 2
  • the thick dotted line (broken line) indicates Invention Example 2
  • the thin dotted line indicates Comparative Example 3.
  • an endothermic peak having a height A of 3 to 10 ⁇ W / mg exists in a temperature range of 150 to 230 ° C.
  • an exothermic peak having a height B of 20 to 50 ⁇ W / mg Is present in a temperature range of 230 ° C. or more and less than 260 ° C., and in the temperature range of 260 ° C. or more and less than 330 ° C., no exothermic peak having a height of 20 ⁇ W / mg or more is present.
  • composition and DSC specified in the present invention are required to combine good moldability and high BH properties even after baking at room temperature for a long time or at a high temperature by baking.
  • the critical significance of each of these conditions is supported.
  • a 6000 series aluminum alloy plate that has both good formability and high BH properties even after baking at room temperature for a long time or at a high temperature by baking. That is, even after long-time aging at room temperature, it is possible to have both good moldability and high BH properties in the conventional low-temperature baking coating curing treatment as well as the conventional high-temperature baking coating curing treatment.
  • the application of a 6000 series aluminum alloy plate can be expanded as an automobile member including a panel material.

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Abstract

In a differential scanning calorimetric curve of an Al-Mg-Si aluminum alloy sheet with a specific composition in which the total content of Mg and Si is greater than 1.2%, the ratio (B/A) of an endothermic peak in the 150-230°C temperature range with a height A of 3-10 µW/mg to an exothermic peak in the 230°C to less than 330°C temperature range with a height B of 20-50 µW/mg is in a specified range.

Description

アルミニウム合金板及びアルミニウム合金板の製造方法Aluminum alloy plate and method for producing aluminum alloy plate
　本発明は、通常の圧延によって製造される６０００系アルミニウム合金板であって、成形性および焼付塗装硬化性に優れた６０００系アルミニウム合金板に関するものである。 The present invention relates to a 6000 series aluminum alloy plate produced by ordinary rolling and having excellent formability and bake coating curability.
　近年、地球環境などへの配慮から、自動車車体の軽量化の社会的要求はますます高まってきている。かかる要求に答えるべく、自動車車体のうち、大型ボディパネル（アウタパネル、インナパネル）に、それまでの鋼板等の鉄鋼材料に代えて、アルミニウム合金材料を適用することが行われている。 In recent years, due to consideration for the global environment, social demands for reducing the weight of automobile bodies are increasing. In order to meet such demands, an aluminum alloy material is applied to a large body panel (outer panel, inner panel) in an automobile body instead of a steel material such as a steel plate.
　前記大型ボディパネルの内、フード、フェンダー、ドア、ルーフ、トランクリッドなどのパネル構造体の、アウタパネル（外板）やインナパネル（内板）等のパネルには、薄肉でかつ高強度アルミニウム合金板として、Ａｌ－Ｍｇ－Ｓｉ系のＡＡ乃至ＪＩＳ６０００系（以下、単に６０００系とも言う）アルミニウム合金板が使用されている。 Among the large body panels, panels such as hoods, fenders, doors, roofs, trunk lids, etc., such as outer panels (outer plates) and inner panels (inner plates), are thin and high-strength aluminum alloy plates. Al-Mg-Si based AA to JIS6000 (hereinafter also simply referred to as 6000) aluminum alloy plates are used.
　この６０００系（Ａｌ－Ｍｇ－Ｓｉ系）アルミニウム合金板は、Ｓｉ、Ｍｇを必須として含み、特に過剰Ｓｉ型の６０００系アルミニウム合金は、人工時効処理時の優れた時効硬化能を有している。このため、プレス成形や曲げ加工時には低耐力化により成形性を確保するとともに、成形後のパネルの塗装焼付処理などの、比較的低温の人工時効処理であっても、耐力が向上し、パネルとしての必要な強度を確保できる焼付け塗装硬化性（以下、ベークハード性＝ＢＨ性、焼付硬化性とも言う）がある。 This 6000 series (Al-Mg-Si series) aluminum alloy sheet contains Si and Mg as essential components, and especially the excess Si type 6000 series aluminum alloy has excellent age hardening ability during artificial aging treatment. . For this reason, in press molding and bending processing, the moldability is ensured by reducing the yield strength, and even with relatively low-temperature artificial aging treatment such as paint baking treatment of the panel after molding, the yield strength is improved, and as a panel There is a bake hardenability (hereinafter also referred to as bake hard property = BH property, bake hardenability) that can secure the required strength of the resin.
　一方、自動車のアウタパネルなどは、周知の通り、アルミニウム合金板に対し、プレス成形における張出成形時や曲げ成形などの成形加工が複合して行われて製作される。例えば、フードやドアなどの大型のアウタパネルでは、張出などのプレス成形によって、アウタパネルとしての成形品形状となされ、次いで、このアウタパネル周縁部のフラットヘムなどのヘム（ヘミング）加工によって、インナパネルとの接合が行われ、パネル構造体とされる。 On the other hand, as is well known, an outer panel of an automobile is manufactured by combining an aluminum alloy plate with a forming process such as an extension forming in a press forming or a bending forming. For example, a large outer panel such as a hood or a door is formed into a molded product shape as an outer panel by press molding such as overhanging, and then an inner panel is formed by hem (hemming) processing such as a flat hem at the outer peripheral edge of the outer panel. Are joined to form a panel structure.
　前記自動車などのアウタパネルなどでは、軽量化のために、より薄肉化される傾向にあり、薄肉化した上で、耐デント性に優れるような、高強度化が求められる。したがって、プレス成形時には、アルミニウム合金板をより低耐力化させて、成形性を確保し、成形後のパネルの塗装焼付処理などの比較的低温の人工時効処理時の加熱により時効硬化して耐力が向上し、薄肉化した上でも必要な強度を確保できる人工時効硬化能（焼付け塗装硬化性）が、より必要とされる。 ¡Outer panels for automobiles and the like tend to be thinner for weight reduction, and are required to have high strength that is excellent in dent resistance after being thinned. Therefore, at the time of press forming, the aluminum alloy plate is made to have a lower yield strength, ensuring formability, and age hardening by heating at a relatively low temperature artificial aging treatment such as paint baking treatment of the panel after molding. There is a need for artificial age-hardening ability (baking paint curability) that can ensure the required strength even after being improved and thinned.
　従来から、このような自動車部材の素材としての６０００系アルミニウム合金板の焼付け塗装硬化性に対し、Ｍｇ－Ｓｉ系クラスタを制御することが、種々提案されている。そして、最近では、これらＭｇ－Ｓｉ系クラスタを、６０００系アルミニウム合金板の示差走査熱分析曲線（以下、ＤＳＣとも言う）の吸熱ピークや発熱ピークにて測定した上で制御する技術が提案されている（特許文献１～５参照）。 Conventionally, various proposals have been made to control Mg—Si clusters for the bake coating curability of 6000 series aluminum alloy plates as materials for such automobile parts. Recently, a technique has been proposed in which these Mg—Si-based clusters are controlled after being measured at an endothermic peak or an exothermic peak of a differential scanning calorimetry curve (hereinafter also referred to as DSC) of a 6000-based aluminum alloy plate. (See Patent Documents 1 to 5).
　例えば、特許文献１では、６０００系アルミニウム合金板の示差走査熱分析曲線において、１００～２００℃の温度範囲における発熱ピーク高さＷ１が５０μＷ以上であり、かつ、２００～３００℃の温度範囲における発熱ピーク高さＷ２と、前記発熱ピーク高さＷ１との比、Ｗ２／Ｗ１ が２０以下であることを規定している。 For example, in Patent Document 1, in the differential scanning calorimetry curve of a 6000 series aluminum alloy plate, the exothermic peak height W1 in the temperature range of 100 to 200 ° C. is 50 μW or more, and the exotherm in the temperature range of 200 to 300 ° C. The ratio between the peak height W2 and the exothermic peak height W1, W2 / W1 is defined to be 20 or less.
　特許文献２では、６０００系アルミニウム合金板の示差走査熱分析曲線において、示差走査熱分析曲線において、２３０～２７０℃の温度範囲における発熱ピーク高さをＡ、２８０～３２０℃の温度範囲における発熱ピーク高さをＢ、３３０～３７０℃の温度範囲における発熱ピーク高さをＣとした際に、前記発熱ピーク高さＢが２０μＷ／ｍｇ以上であるとともに、前記発熱ピーク高さＢに対する前記発熱ピーク高さＡ、Ｃの各比である、Ａ／Ｂを０．４５以下、Ｃ／Ｂを０．６以下と各々規定している。 In Patent Document 2, in the differential scanning calorimetry curve of a 6000 series aluminum alloy plate, the exothermic peak height in the temperature range of 230 to 270 ° C. in the differential scanning calorimetry curve is A, and the exothermic peak in the temperature range of 280 to 320 ° C. When the height is B and the exothermic peak height in the temperature range of 330 to 370 ° C. is C, the exothermic peak height B is not less than 20 μW / mg, and the exothermic peak height relative to the exothermic peak height B is The ratios of A and C are respectively defined as A / B of 0.45 or less and C / B of 0.6 or less.
　特許文献３では、６０００系アルミニウム合金板だが、ＭｇとＳｉとの合計量が１．２％以下である板の示差走査熱分析曲線において、２３０～３３０℃の温度範囲内に、発熱ピークが１つだけか、または、互いのピーク間の温度差が５０℃以下の発熱ピークが２つだけ存在し、前記１つだけの発熱ピークの高さか、または、前記２つだけの発熱ピークのうちのピーク高さが大きい方の発熱ピークの高さが２０～５０μＷ／ｍｇの範囲であることを規定している。 In Patent Document 3, a differential scanning calorimetry curve of a 6000 series aluminum alloy plate having a total amount of Mg and Si of 1.2% or less has an exothermic peak within a temperature range of 230 to 330 ° C. There are only two exothermic peaks having a temperature difference between the peaks of 50 ° C. or less, the height of the only one exothermic peak, or the only one of the two exothermic peaks. It defines that the exothermic peak height of the larger peak height is in the range of 20-50 μW / mg.
　特許文献４では、６０００系アルミニウム合金板だが、Ｓｎ添加を必須とする板の示差走査熱分析曲線において、Ｍｇ－Ｓｉクラスタの溶解に相当する吸熱ピークとして、１５０～２３０℃の温度範囲の吸熱ピークのピーク高さが８μＷ／ｍｇ以下（但し、０μＷ／ｍｇを含む）である一方で、Ｍｇ－Ｓｉクラスタの生成に相当する発熱ピークとして、２４０～２５５℃の温度範囲の発熱ピークのピーク高さが２０μＷ／ｍｇ以上であることを規定している。 In Patent Document 4, an endothermic peak in the temperature range of 150 to 230 ° C. as an endothermic peak corresponding to dissolution of Mg—Si clusters in a differential scanning calorimetry curve of a 6000 series aluminum alloy plate that requires Sn addition. The peak height of the exothermic peak in the temperature range of 240 to 255 ° C. is the exothermic peak corresponding to the formation of the Mg—Si cluster, while the peak height of is 8 μW / mg or less (including 0 μW / mg). Is 20 μW / mg or more.
　特許文献５では、アルミニウム合金材の溶体化および焼き入れ処理を含む調質処理後の示差走査熱分析曲線において、Ｓｉ／空孔クラスタ（ＧＰＩ）の溶解に相当する１５０～２５０℃の温度範囲におけるマイナスの吸熱ピーク高さを１０００μＷ以下とし、Ｍｇ／Ｓｉクラスタ（ＧＰＩＩ）の析出に相当する２５０～３００℃の温度範囲におけるプラスの発熱ピーク高さを２０００μＷ以下として、室温時効抑制と低温時効硬化能に優れさせることが記載されている。 In Patent Document 5, in a differential scanning calorimetry curve after tempering treatment including solution treatment and quenching treatment of an aluminum alloy material, in a temperature range of 150 to 250 ° C. corresponding to dissolution of Si / vacancy clusters (GPI). The negative endothermic peak height is set to 1000 μW or less, the positive exothermic peak height in the temperature range of 250 to 300 ° C. corresponding to the precipitation of Mg / Si clusters (GPII) is set to 2000 μW or less, and room temperature aging suppression and low temperature aging hardening ability are achieved. It is described that it is made excellent.
日本国特許第４１１７２４３号公報Japanese Patent No. 4117243 日本国特開２０１３－１６７００４号公報Japanese Unexamined Patent Publication No. 2013-167004 日本国特開２０１５－１９６８５２号公報Japanese Unexamined Patent Publication No. 2015-196852 日本国特開２０１５－１９６８５３号公報Japanese Unexamined Patent Publication No. 2015-196853 日本国特許第３８１９２６３号公報Japanese Patent No. 3819263
　しかし、これら従来の、ＤＳＣの吸熱ピークや発熱ピークの制御技術は、前記自動車部材の低温化短時間化する焼付け塗装硬化処理に対応して、高いＢＨ性を得ようとするものであり、その加熱温度は高くても１７５℃、低い例では１５０℃の焼付け塗装硬化処理としている。言い換えると、１８０℃以上などの高温での焼付け塗装硬化処理でのＢＨ性は意図していない。
　このため、このような高温での焼付け塗装硬化処理において、長時間の室温時効後のＡｌ－Ｍｇ－Ｓｉ系アルミニウム合金板に、良好な成形性と高いＢＨ性とを兼備させるには、未だ改善の余地があった。
　また、良好な成形性と前記高温での焼付け塗装硬化処理における高いＢＨ性とを兼備させた上で、更に、前記低温での焼付け塗装硬化処理においても高いＢＨ性を得ることも、未だ改善の余地があった。
　すなわち、互いに相矛盾すると言える、伸び、高温ＢＨ性、低温ＢＨ性をともに兼備させる技術課題には、未だ改善の余地があった。 However, these conventional DSC endothermic peak and exothermic peak control techniques are intended to obtain high BH properties in response to the baking coating curing process for reducing the temperature and time of the automobile parts. The heating temperature is 175 ° C. at the highest, and 150 ° C. in the low example. In other words, the BH property in the baking finish hardening process at a high temperature such as 180 ° C. or higher is not intended.
Therefore, in such a high temperature baking coating hardening process, it is still an improvement to have a good formability and high BH properties in an Al-Mg-Si aluminum alloy sheet after long-term aging at room temperature. There was room for.
Moreover, after combining the good moldability and the high BH property in the baking coating curing process at the high temperature, it is still improved to obtain the high BH property in the baking coating curing process at the low temperature. There was room.
That is, there is still room for improvement in the technical problem that can be said to be mutually contradictory, and that has both elongation, high temperature BH property, and low temperature BH property.
　このような状況に鑑み、本発明の目的は、長時間の室温時効後であっても、良好な成形性と、前記高温での焼付け塗装硬化処理は勿論、前記従来の低温での焼付け塗装硬化処理においても高いＢＨ性とを兼備できる、６０００系アルミニウム合金板およびその製造方法を提供することである。 In view of such circumstances, the object of the present invention is to provide the conventional low-temperature baking coating curing, as well as good moldability and baking coating curing treatment at the high temperature, even after prolonged aging at room temperature. It is to provide a 6000 series aluminum alloy plate and a method for producing the same that can have high BH properties in processing.
　この目的を達成するために、本発明の成形性と焼付け塗装硬化性に優れたアルミニウム合金板の要旨は、質量％で、Ｍｇ：０．３～１．５％、Ｓｉ：０．６～１．５％を各々含有するとともに、前記Ｍｇ含有量とＳｉ含有量との合計が１．２％超であり、残部がＡｌ及び不可避的不純物からなるアルミニウム合金板であって、この板の示差走査熱分析曲線において、１５０～２３０℃の温度範囲内に高さＡが３～１０μＷ／ｍｇである吸熱ピークが存在するとともに、２３０℃以上、３３０℃未満の温度範囲内に高さＢが２０～５０μＷ／ｍｇである発熱ピークが存在し、かつ前記発熱ピークの中の最大ピーク高さＢと、前記吸熱ピークの中の最大ピーク高さＡとの比Ｂ／Ａが３．５超、１５．０未満であることとする。 In order to achieve this object, the gist of the aluminum alloy plate excellent in formability and bake hardenability of the present invention is, by mass%, Mg: 0.3 to 1.5%, Si: 0.6 to 1 .5%, and the total of Mg content and Si content is more than 1.2%, and the balance is an aluminum alloy plate made of Al and unavoidable impurities. In the thermal analysis curve, an endothermic peak having a height A of 3 to 10 μW / mg exists in a temperature range of 150 to 230 ° C., and a height B of 20 to 20 in a temperature range of 230 ° C. or more and less than 330 ° C. An exothermic peak of 50 μW / mg is present, and the ratio B / A of the maximum peak height B in the exothermic peak to the maximum peak height A in the endothermic peak is more than 3.5; It shall be less than 0.
　また、前記目的を達成するために、本発明の成形性と焼付け塗装硬化性に優れたアルミニウム合金板の製造方法の要旨は、質量％で、Ｍｇ：０．３～１．５％、Ｓｉ：０．６～１．５％を各々含有するとともに、前記Ｍｇ含有量とＳｉ含有量との合計が１．２％超であり、残部がＡｌ及び不可避的不純物からなるアルミニウム合金冷延板を、溶体化および焼入れ処理後１時間以内に、３０℃～６０℃の温度域で５時間以上、５００時間以下保持する、低温長時間の予備時効処理を施し、この板の人工時効処理される前の示差走査熱分析曲線において、１５０～２３０℃の温度範囲内に高さＡが３～１０μＷ／ｍｇである吸熱ピークを存在させるとともに、２３０℃以上、３３０℃未満の温度範囲内に高さＢが２０～５０μＷ／ｍｇである発熱ピークを存在させ、かつ前記発熱ピーク高さＢと前記吸熱ピーク高さＡとの比Ｂ／Ａを３．５超、１５．０未満としたことである。 In order to achieve the above object, the gist of the method for producing an aluminum alloy plate excellent in formability and bake hardenability of the present invention is mass%, Mg: 0.3 to 1.5%, Si: An aluminum alloy cold-rolled sheet containing 0.6 to 1.5% each, the total of the Mg content and the Si content is more than 1.2%, the balance being Al and inevitable impurities, Within 1 hour after solution treatment and quenching treatment, pre-aging treatment is performed at a temperature range of 30 ° C. to 60 ° C. for 5 hours or more and 500 hours or less. In the differential scanning calorimetry curve, an endothermic peak having a height A of 3 to 10 μW / mg is present in a temperature range of 150 to 230 ° C., and a height B is in a temperature range of 230 ° C. or more and less than 330 ° C. Fever of 20-50 μW / mg A peak is present, and the ratio B / A between the exothermic peak height B and the endothermic peak height A is more than 3.5 and less than 15.0.
　本発明者らは、長時間の室温時効後であっても、良好な成形性と、前記高温での焼付け塗装硬化処理は勿論、前記従来の低温での焼付け塗装硬化処理においても高いＢＨ性とを兼備するためのクラスタにつき検討した。
　この結果、長時間の室温時効後であっても高い伸びを得るためには、１５０～２３０℃の温度範囲内での示唆熱曲線の吸熱ピークに相当するクラスタが一定以上必要であることを知見した。
　また、焼付け塗装硬化処理における焼付け処理温度が、高温から低温まで大きく異なったとしても、いずれの焼付け処理温度でも高いＢＨ量を得るためには、示唆熱曲線の吸熱ピークに相当するクラスタを少なくする、または２３０℃～３３０℃の温度範囲の発熱ピークに相当するクラスタを多くすることを知見した。
　すなわち、１５０～２３０℃の温度範囲内での示唆熱曲線の吸熱ピークと２３０℃～３３０℃の温度範囲の発熱ピークを精緻に制御することにより、長時間の室温時効後であっても、高い伸びを得るとともに、焼付け処理温度が、高温から低温まで大きく異なったとしても、いずれの焼付け処理温度でも高いＢＨ性が得られることを知見した。
　また、焼付塗装硬化条件（人工時効処理条件）の特に温度によって、高いＢＨ性を得るための、示差熱曲線が異なることを知見し、１７５℃以下の比較的低い焼付塗装温度では、１８０℃以上の比較的高温の焼付塗装温度と比較して、より精緻に示差熱曲線を制御する必要があることも知見した。 The present inventors have good moldability and high BH property even in the conventional low-temperature baking coating curing treatment as well as the high-temperature baking coating curing treatment, even after prolonged room temperature aging. We examined a cluster to combine the two.
As a result, in order to obtain high elongation even after prolonged aging at room temperature, it has been found that more than a certain number of clusters corresponding to the endothermic peak of the suggested heat curve within the temperature range of 150 to 230 ° C is necessary. did.
Moreover, even if the baking temperature in the baking coating curing process varies greatly from high temperature to low temperature, in order to obtain a high BH amount at any baking temperature, the number of clusters corresponding to the endothermic peak of the suggested heat curve is reduced. Or clusters that correspond to exothermic peaks in the temperature range of 230 ° C. to 330 ° C. were found to increase.
That is, by precisely controlling the endothermic peak of the suggested heat curve within the temperature range of 150 to 230 ° C. and the exothermic peak of the temperature range of 230 ° C. to 330 ° C., it is high even after prolonged aging at room temperature. As well as obtaining elongation, it has been found that even if the baking temperature varies greatly from high temperature to low temperature, high BH properties can be obtained at any baking temperature.
In addition, it was found that the differential thermal curve for obtaining high BH properties varies depending on the temperature especially in the baking coating curing conditions (artificial aging treatment conditions), and at a relatively low baking coating temperature of 175 ° C. or lower, 180 ° C. or higher. It was also found that it is necessary to control the differential heat curve more precisely than the relatively high baking coating temperature.
　これらの知見を土台に、本発明は、より精緻に示差熱曲線を制御する組織制御を行って、自動車部材の素材としての６０００系アルミニウム合金板に、互いに相矛盾すると言える、伸び、高温ＢＨ性、低温ＢＨ性をともに兼備させたものである。 Based on these findings, the present invention performs structure control to control the differential heat curve more precisely, and it can be said that the 6000 series aluminum alloy plates as materials for automobile members are mutually contradictory. Both have low-temperature BH properties.
本発明アルミニウム合金板の示差走査熱分析曲線を示す説明図である。It is explanatory drawing which shows the differential scanning calorimetry curve of this invention aluminum alloy plate.
　本発明で言うアルミニウム合金板（成形素材板）とは、熱間圧延板や冷間圧延板などの圧延板で、この圧延板に溶体化処理および焼入れ処理などの調質（Ｔ４）が施された板であって、使用される自動車部材に成形される前であって、塗装焼付硬化処理などの人工時効処理（人工時効硬化処理）される前の、素材アルミニウム合金板を言う。以下の記載ではアルミニウムをアルミやＡｌとも言う。 The aluminum alloy plate (molding material plate) referred to in the present invention is a rolled plate such as a hot rolled plate or a cold rolled plate, and is subjected to tempering (T4) such as solution treatment and quenching treatment. It is a raw material aluminum alloy plate before being formed into an automobile member to be used and before being subjected to artificial aging treatment (artificial age hardening treatment) such as paint baking hardening treatment. In the following description, aluminum is also referred to as aluminum or Al.
　以下に、本発明の実施の形態につき、要件ごとに具体的に説明する。 Hereinafter, the embodiment of the present invention will be specifically described for each requirement.
アルミニウム合金組成：
　先ず、本発明アルミニウム合金板の化学成分組成について、各元素の限定理由を含めて、以下に説明する。なお、各元素の含有量の％表示は全て質量％の意味である。 Aluminum alloy composition:
First, the chemical component composition of the aluminum alloy sheet of the present invention will be described below, including reasons for limiting each element. In addition,% display of content of each element means the mass% altogether.
　本発明アルミニウム合金板の化学成分組成は、前記自動車大型ボディパネルなどの自動車部材の素材として、要求される成形性や焼付塗装硬化性を、６０００系アルミニウム合金の組成から満たすために決定される。
　この観点から、本発明アルミニウム合金板の化学成分組成は、質量％で、Ｍｇ：０．３～１．５％、Ｓｉ：０．６～１．５％を各々含有するとともに、前記Ｍｇ含有量とＳｉ含有量との合計が１．２％超であり、残部がＡｌ及び不可避的不純物からなるものとする。 The chemical component composition of the aluminum alloy plate of the present invention is determined so as to satisfy the required formability and bake hardenability from the composition of the 6000 series aluminum alloy as a material of an automobile member such as the automobile large body panel.
From this point of view, the chemical composition of the aluminum alloy sheet of the present invention includes, in mass%, Mg: 0.3 to 1.5% and Si: 0.6 to 1.5%, respectively, and the Mg content. And the Si content are over 1.2%, and the balance consists of Al and inevitable impurities.
　この組成に、更に、Ｃｕ：０．０２～０．８％、Ｆｅ：０．０５～０．５％、Ｍｎ：０．０５～０．３％、Ｚｒ：０．０４～０．１％、Ｃｒ：０．０４～０．３％、Ｖ：０．０２～０．１％、Ａｇ：０．０１～０．１％、Ｚｎ：０．０１～０．３％のうちの一種または二種以上を含んでも良い。 In addition to this composition, Cu: 0.02 to 0.8%, Fe: 0.05 to 0.5%, Mn: 0.05 to 0.3%, Zr: 0.04 to 0.1%, One or two of Cr: 0.04 to 0.3%, V: 0.02 to 0.1%, Ag: 0.01 to 0.1%, Zn: 0.01 to 0.3% The above may be included.
Ｓｉ：０．６～１．５％
　ＳｉはＭｇとともに、固溶強化と、焼付け塗装処理などの人工時効処理時に、強度向上に寄与するＭｇ－Ｓｉ系析出物などの時効析出物を形成して、時効硬化能を発揮し、必要な強度（耐力）を得るための必須の元素である。
　Ｓｉ含有量が少なすぎると、焼付け塗装処理前（人工時効熱処理前）の固溶Ｓｉ量が減少し、Ｍｇ－Ｓｉ系析出物の生成量が不足するため、ＢＨ性が著しく低下し、強度が不足する。一方、Ｓｉ含有量が多すぎると、粗大な晶出物および析出物が形成されて、延性が低下し、素材板圧延の際の割れの原因となる。したがって、Ｓｉの含有量は０．６～１．５％の範囲、好ましくは、０．７～１．５％の範囲とする。 Si: 0.6 to 1.5%
Si, together with Mg, forms aging precipitates such as Mg-Si-based precipitates that contribute to strength improvement during solid solution strengthening and artificial aging treatment such as baking coating treatment, and exhibits age-hardening ability. It is an essential element for obtaining strength (yield strength).
If the Si content is too small, the amount of solute Si before baking coating treatment (before artificial aging heat treatment) will decrease, and the amount of Mg-Si-based precipitates will be insufficient, resulting in a marked decrease in BH properties and strength. Run short. On the other hand, when there is too much Si content, a coarse crystallized substance and a precipitate will be formed, ductility will fall, and it will become the cause of the crack in the case of raw-material plate rolling. Therefore, the Si content is in the range of 0.6 to 1.5%, preferably in the range of 0.7 to 1.5%.
Ｍｇ：０．３～１．５％
　ＭｇもＳｉとともに、固溶強化と、焼付け塗装処理などの人工時効熱処理時に、強度向上に寄与するＭｇ－Ｓｉ系析出物などの時効析出物を形成して、時効硬化能を発揮し、必要な強度を得るための必須の元素である。Ｍｇ含有量が少なすぎると、焼付け塗装処理前の固溶Ｍｇ量が減少し、Ｍｇ－Ｓｉ系析出物の生成量が不足するため、ＢＨ性が著しく低下し、強度が不足する。一方、Ｍｇ含有量が多すぎると、冷間圧延時にせん断帯が形成されやすくなり、素材板圧延時の割れの原因となる。したがって、Ｍｇの含有量は０．３～１．５％の範囲、好ましくは０．４～０．８％の範囲とする。 Mg: 0.3-1.5%
Mg and Si, together with solid solution strengthening, form aging precipitates such as Mg-Si-based precipitates that contribute to strength improvement during artificial aging heat treatment such as baking coating treatment, and show age-hardening ability. It is an essential element for obtaining strength. If the Mg content is too small, the amount of solid solution Mg before baking coating treatment is reduced, and the amount of Mg—Si based precipitates is insufficient, so that the BH property is remarkably lowered and the strength is insufficient. On the other hand, when there is too much Mg content, it will become easy to form a shear band at the time of cold rolling, and will cause the crack at the time of a raw material plate rolling. Therefore, the Mg content is in the range of 0.3 to 1.5%, preferably in the range of 0.4 to 0.8%.
　また、パネルへの成形後の塗装焼き付け処理での優れた人工時効硬化能を発揮させるために、Ｍｇ含有量とＳｉ含有量との合計は１．２％超とする。この合計が、前記特許文献３のように、１．２％以下では、例え板の製造条件が後述する好ましい範囲であったとしても、本発明で規定する吸熱ピークや発熱ピークを生成できず、人工時効硬化能が不足して、必要な強度が得られなくなる。ただ、Ｍｇ含有量とＳｉ含有量との合計の上限は、板を、熱延割れを生じずに、製造できる限度によって決まり、好ましくは２．５％とする。 Also, in order to exhibit the excellent artificial age hardening ability in the paint baking process after forming on the panel, the total of the Mg content and the Si content is over 1.2%. When the total is 1.2% or less as in Patent Document 3, even if the production conditions of the board are within a preferable range described later, an endothermic peak or an exothermic peak defined in the present invention cannot be generated, Artificial age-hardening ability is insufficient, and the required strength cannot be obtained. However, the upper limit of the total of the Mg content and the Si content is determined by the limit at which the plate can be produced without causing hot rolling cracking, and is preferably 2.5%.
Ｃｕ、Ｆｅ、Ｍｎ、Ｚｒ、Ｃｒ、Ｖ、Ａｇ、Ｚｎのうちの一種または二種以上
　これらの元素は、共通して板を高強度化させる効果があるので、本発明では同効元素と見なせ、必要により選択的に含有させるが、その具体的な機構には、共通する部分も、異なる部分も勿論ある。 One or more of Cu, Fe, Mn, Zr, Cr, V, Ag, Zn These elements have the effect of increasing the strength of the plate in common. Of course, it is selectively contained as necessary, but there are of course a common part and a different part in the specific mechanism.
　Ｃｕは固溶強化により強度を向上させることができる。Ｃｕの含有量が少なすぎると、その効果が小さく、多すぎてもその効果は飽和し、却って耐食性などを劣化させる。 Cu can improve strength by solid solution strengthening. If the Cu content is too small, the effect is small, and if it is too much, the effect is saturated, and on the contrary, the corrosion resistance is deteriorated.
　Ｆｅは晶出物を生成して、再結晶粒の核となり、結晶粒の粗大化を阻止し、強度を向上させる役割を果たす。含有量が少なすぎると、その効果が小さく、多すぎると、粗大な化合物を形成し、破壊の起点となり、強度や成形性が低下する。 Fe forms a crystallized product, serves as a nucleus of recrystallized grains, prevents coarsening of crystal grains, and plays a role of improving strength. If the content is too small, the effect is small. If the content is too large, a coarse compound is formed, which becomes a starting point of destruction, and the strength and formability are lowered.
　Ｍｎ、Ｚｒ、Ｃｒ、Ｖは、鋳塊及び最終板製品の結晶粒を微細化して強度向上に寄与する。また、これらの元素は分散粒子として存在して、結晶粒微細化に寄与して、成形性も向上させる。各々の含有量が少なすぎると、これらの結晶粒微細化による、強度や成形性の向上効果が不足する。一方、これらの元素が多すぎると、粗大な化合物を形成し、延性を劣化させる。 Mn, Zr, Cr, V contributes to strength improvement by refining the crystal grains of the ingot and final plate product. Further, these elements exist as dispersed particles, contribute to crystal grain refinement, and improve moldability. When each content is too small, the effect of improving strength and formability due to the refinement of crystal grains is insufficient. On the other hand, when there are too many of these elements, a coarse compound will be formed and ductility will deteriorate.
　Ａｇは、自動車部材への成形加工後の人工時効熱処理によって強度向上に寄与する時効析出物を緊密微細に析出させ、高強度化を促進する効果がある。含有量が少なすぎると強度向上効果が小さく、多すぎると、圧延性及び溶接性などの諸特性を却って低下させ、また、強度向上効果も飽和し、高価となる。 Ag has the effect of closely and finely precipitating aging precipitates that contribute to strength improvement by artificial aging heat treatment after molding of automobile parts, thereby promoting high strength. If the content is too small, the effect of improving the strength is small, and if the content is too large, various properties such as rollability and weldability are reduced, and the effect of improving the strength is saturated and expensive.
　Ｚｎは人工時効硬化能（ＢＨ性）を向上させるのに有用で、焼付け塗装処理で、板組織の結晶粒内へのＧＰゾーンなどの化合物相の析出を促進させて高強度化する効果がある。 Zn is useful for improving artificial age-hardening ability (BH property), and has an effect of increasing the strength by promoting precipitation of a compound phase such as a GP zone in the crystal grains of the plate structure in the baking coating process. .
　したがって、これらＣｕ、Ｆｅ、Ｍｎ、Ｚｒ、Ｃｒ、Ｖ、Ａｇ、Ｚｎは、含有させる場合には、前記した通り、Ｃｕ：０．０２～０．８％、Ｆｅ：０．０５～０．５％、Ｍｎ：０．０５～０．３％、Ｚｒ：０．０４～０．１％、Ｃｒ：０．０４～０．３％、Ｖ：０．０２～０．１％、Ａｇ：０．０１～０．１％、Ｚｎ：０．０１～０．３％の範囲で、一種または二種以上を含有させる。 Therefore, when Cu, Fe, Mn, Zr, Cr, V, Ag, and Zn are contained, as described above, Cu: 0.02 to 0.8%, Fe: 0.05 to 0.5 %, Mn: 0.05 to 0.3%, Zr: 0.04 to 0.1%, Cr: 0.04 to 0.3%, V: 0.02 to 0.1%, Ag: 0.0. In the range of 01 to 0.1% and Zn: 0.01 to 0.3%, one kind or two or more kinds are contained.
その他の元素：
　これら記載した以外の、Ｔｉ、Ｂなどのその他の元素は不可避的な不純物である。Ｔｉは、Ｂとともに、粗大な化合物を形成して機械的特性を劣化させる。ただ、微量の含有によって、アルミニウム合金鋳塊の結晶粒を微細化する効果もあるので、６０００系合金としてＪＩＳ規格などで規定する範囲での各々の含有を許容する。この許容量の例として、Ｔｉは０．１％以下、好ましくは０．０５％以下とする。また、Ｂは０．０３％以下とする。ちなみに、本発明では、前記特許文献４で必須としているＳｎは添加しない。Ｓｎを添加した場合には、後述する好ましい板の製造条件とした場合に、却ってＭｇ－Ｓｉクラスタを減少させ、本発明で規定する吸熱ピークや発熱ピークを生成できず、人工時効硬化能が不足して、必要な強度が得られなくなる可能性がある。 Other elements:
Other than these elements, other elements such as Ti and B are inevitable impurities. Ti, together with B, forms a coarse compound and degrades mechanical properties. However, since the inclusion of a small amount also has the effect of refining the crystal grains of the aluminum alloy ingot, each content in the range specified by the JIS standard is allowed as a 6000 series alloy. As an example of this allowable amount, Ti is 0.1% or less, preferably 0.05% or less. Further, B is set to 0.03% or less. Incidentally, in the present invention, Sn, which is essential in Patent Document 4, is not added. In the case where Sn is added, the Mg-Si clusters are reduced on the contrary when the preferable production conditions for the plate are described later, the endothermic peak and the exothermic peak defined in the present invention cannot be generated, and the artificial age hardening ability is insufficient. As a result, the required strength may not be obtained.
（素材板組織）
　以上の合金組成を前提に、本発明では、アルミニウム合金板の組織を、この板を素材とする部材における人工時効析出物の存在状態を予め示す指標として、示差走査熱分析で得られたＤＳＣ（示差走査熱分析曲線：ＤＳＣプロファイル）により規定する。
　すなわち、本発明は、長時間の室温時効後であっても、良好な成形性と、主たる対象とする比較的高温の焼付け塗装硬化処理での高いＢＨ性は勿論、比較的低温での焼付け塗装硬化処理においても高いＢＨ性とを兼備するために、示差走査熱分析で得られたＤＳＣ（示差走査熱分析曲線：ＤＳＣプロファイル）により規定する。 (Material board structure)
Based on the above alloy composition, in the present invention, the structure of an aluminum alloy plate is used as an index indicating in advance the state of artificial aging precipitates in a member made of this plate, and DSC obtained by differential scanning calorimetry ( Differential scanning calorimetry curve: DSC profile).
In other words, the present invention is capable of baking at a relatively low temperature as well as good formability and high BH property in a relatively high temperature baking coating curing process, which is the main target, even after prolonged room temperature aging. In order to have high BH property also in the curing process, it is defined by DSC (differential scanning thermal analysis curve: DSC profile) obtained by differential scanning thermal analysis.
　比較的低温の焼付塗装条件では、１５０～２３０℃の温度範囲内での吸熱ピークが存在した場合には、高いＢＨ量が得られにくいが、本発明が主たる対象とする比較的高温の焼付塗装条件では、前記吸熱ピークがある程度存在しても、高いＢＨ量が得られる。これは、従来の比較的低温の焼付塗装条件では、焼付塗装処理中に、前記吸熱ピークに相当するクラスタが溶解しても、その後の強化相が新たに生成しにくいため、高いＢＨ性が得られないものと推考される。 Under relatively low-temperature baking coating conditions, if there is an endothermic peak in the temperature range of 150 to 230 ° C., it is difficult to obtain a high amount of BH, but the relatively high-temperature baking coating that is the main object of the present invention. Under the conditions, even if the endothermic peak is present to some extent, a high BH amount can be obtained. This is because, under the conventional relatively low-temperature baking coating conditions, even if a cluster corresponding to the endothermic peak is dissolved during the baking coating process, it is difficult for a subsequent strengthening phase to be newly generated, so that a high BH property is obtained. It is assumed that it is not possible.
　これに対して、本発明が主たる対象とする比較的高温の焼付塗装条件では、前記吸熱ピークに相当するクラスタが極短時間で溶解して、その後強化相が新たに生成しやすいため、前記吸熱ピークが予め存在しても、高いＢＨ性が得られると推考される。このため、本発明が対象とする比較的高温の焼付塗装硬化条件においては、前記吸熱ピークを高くすることができ、この吸熱ピークに相当するクラスタの存在によって、加工硬化性を高めることができる。したがって、ＢＨ性を高める、２３０℃以上、３３０℃未満の温度範囲内の発熱ピークも併せて存在させれば、高い加工硬化性（成形性）とＢＨ性との両立が可能である。
　この比較的高温の焼付塗装硬化処理条件とは、例えば、加熱温度１８０～２３０℃、加熱保持時間１０～３０分の条件で焼付け塗装硬化処理されることを言い、従来の比較的低温短時間の焼付け塗装硬化処理の加熱温度の、高くても１７５℃とは、特に加熱温度において区別される。 On the other hand, under relatively high-temperature baking coating conditions, the main subject of the present invention, the clusters corresponding to the endothermic peaks are dissolved in an extremely short time, and then a strengthening phase is easily generated. It is presumed that even if a peak is present in advance, a high BH property can be obtained. For this reason, the endothermic peak can be increased under the relatively high temperature baking finish curing conditions targeted by the present invention, and the work curability can be enhanced by the presence of clusters corresponding to the endothermic peak. Therefore, if there is also an exothermic peak in the temperature range of 230 ° C. or higher and lower than 330 ° C. that enhances BH properties, both high work curability (formability) and BH properties can be achieved.
This relatively high temperature baking coating curing treatment condition means, for example, that the baking coating curing treatment is performed under the conditions of a heating temperature of 180 to 230 ° C. and a heating holding time of 10 to 30 minutes. The heating temperature of the baking coating curing process is distinguished from at most 175 ° C. in particular at the heating temperature.
　この発熱ピークと吸熱ピークを併せて存在させる場合、各々のピーク高さとともに、互いのピーク高さのバランスも重要となる。例えば、発熱ピーク／吸熱ピークの比が小さすぎる場合は、吸熱ピークに相当するクラスタの存在が大きすぎて、ＢＨ性が低くなりすぎるか、発熱ピークが低すぎて強化相となるクラスタが多すぎ、伸びが低下してしまう。一方、発熱ピーク／吸熱ピークが大き過ぎる場合には、吸熱ピークに相当するクラスタの存在が小さすぎて、加工硬化性に劣るか、発熱ピークが高すぎて強化相となるクラスタが少なすぎ、ＢＨ性が低くなりすぎる。 When this exothermic peak and endothermic peak are present together, the balance between the peak heights as well as the respective peak heights is important. For example, when the ratio of the exothermic peak / endothermic peak is too small, the existence of clusters corresponding to the endothermic peak is too large and the BH property is too low, or the exothermic peak is too low and there are too many clusters that become the reinforcing phase. , Elongation will decrease. On the other hand, if the exothermic peak / endothermic peak is too large, the presence of clusters corresponding to the endothermic peak is too small and the work hardenability is inferior, or the exothermic peak is too high and there are too few clusters that become the reinforcing phase. Is too low.
　このような知見に基づき、本発明では、高い伸びと比較的高温のＢＨ性との両立のために、アルミニウム合金板の人工時効処理される前のＤＳＣにおいて、１５０～２３０℃の温度範囲内に高さＡが３～１０μＷ／ｍｇである吸熱ピークが存在するとともに、２３０℃以上、３３０℃未満の温度範囲内に高さＢが２０～５０μＷ／ｍｇである発熱ピークが存在し、かつ、前記発熱ピーク高さＢと前記吸熱ピーク高さＡの比Ｂ／Ａが３．５超、１５．０未満であることとする。
　また、前記比較的高温の場合だけでなく、比較的低温のＢＨ性においても、高い伸びと両立させるために、アルミニウム合金板の人工時効処理される前のＤＳＣにおいて、１５０～２３０℃の温度範囲内に高さＡが、好ましくは３～８μＷ／ｍｇである吸熱ピークを存在させるとともに、２３０℃以上、３３０℃未満の温度範囲内に高さＢが、好ましくは２０～４０μＷ／ｍｇである発熱ピークを存在させ、かつ、前記発熱ピーク高さＢと前記吸熱ピーク高さＡの比Ｂ／Ａが３．５超、１５．０未満であることとする。更に、より好ましくは、前記吸熱ピークの高さＡが３～７μＷ／ｍｇであり、前記発熱ピークの高さＢが２０～３５μＷ／ｍｇであることとする。 Based on such knowledge, in the present invention, in order to achieve both high elongation and relatively high BH properties, the DSC before artificial aging treatment of the aluminum alloy sheet is within a temperature range of 150 to 230 ° C. An endothermic peak having a height A of 3 to 10 μW / mg is present, and an exothermic peak having a height B of 20 to 50 μW / mg is present in a temperature range of 230 ° C. or higher and lower than 330 ° C., and The ratio B / A between the exothermic peak height B and the endothermic peak height A is more than 3.5 and less than 15.0.
In addition, in the DSC before the artificial aging treatment of the aluminum alloy sheet, in order to make it compatible with high elongation not only in the case of the relatively high temperature but also in the BH property at a relatively low temperature, a temperature range of 150 to 230 ° C. An endothermic peak having a height A of preferably 3 to 8 μW / mg, and an exotherm having a height B of preferably 20 to 40 μW / mg within a temperature range of 230 ° C. or higher and lower than 330 ° C. A peak is present, and the ratio B / A between the exothermic peak height B and the endothermic peak height A is more than 3.5 and less than 15.0. More preferably, the endothermic peak height A is 3 to 7 μW / mg, and the exothermic peak height B is 20 to 35 μW / mg.
　前記吸熱ピークについて、吸熱ピークがマイナス側に高いということは、示差熱分析中にクラスタが溶解していることを意味しており、言い換えれば、吸熱ピークに相当するクラスタが多いことを意味する。そのマイナス側のピークの高さＡが３μＷ／ｍｇ未満と低ければ、加工硬化性が低くなり、成形性が低下する。一方で、そのマイナス側のピークの高さＡが１０μＷ／ｍｇを超えて高くなりすぎると、比較的高温のＢＨ性が低下し、７μＷ／ｍｇを超えて高くなりすぎると、比較的低温のＢＨ性が低下してしまう。 Regarding the endothermic peak, the fact that the endothermic peak is high on the minus side means that the cluster is dissolved during the differential thermal analysis, in other words, there are many clusters corresponding to the endothermic peak. If the negative peak height A is as low as less than 3 μW / mg, the work curability is lowered and the moldability is lowered. On the other hand, if the negative peak height A is too high exceeding 10 μW / mg, the relatively high-temperature BH property decreases, and if it exceeds 7 μW / mg, the relatively low-temperature BH is decreased. The nature will decline.
　前記発熱ピークについて、発熱ピークが高いということは、示差熱分析中に強化相または強化相の核となるクラスタが多く生成していることを意味しており、言い換えると、強化相または強化相の核となるクラスタが少ないことを意味する。そのプラス側のピークの高さＢが５０μＷ／ｍｇを越えて高すぎると、強化相または強化相の核となるクラスタが少なすぎ、比較的高温での焼付塗装硬化のＢＨ性が低くなり、４０μＷ／ｍｇを越えて高すぎると、比較的低温での焼付塗装硬化のＢＨ性が低くなってしまう。一方で、そのプラス側のピークの高さＢが２０μＷ／ｍｇを未満と低すぎると、強化相または強化相の核となるクラスタが多すぎて、伸びが低下してしまう。ちなみに、これらの傾向は、板の合金組成が本発明範囲を満たすことが前提である。 With respect to the exothermic peak, a high exothermic peak means that many clusters that are the core of the reinforcing phase or the reinforcing phase are generated during the differential thermal analysis, in other words, the strengthening phase or the strengthening phase. This means that there are few core clusters. If the positive peak height B exceeds 50 μW / mg, the reinforcing phase or the core of the reinforcing phase is too few, and the BH property of baking coating curing at a relatively high temperature becomes low, resulting in 40 μW. If it exceeds / mg and is too high, the BH property of baking coating curing at a relatively low temperature will be low. On the other hand, if the positive peak height B is too low, less than 20 μW / mg, the reinforcing phase or the core of the reinforcing phase is too many, and the elongation is lowered. Incidentally, these tendencies are based on the premise that the alloy composition of the plate satisfies the scope of the present invention.
　このように、素材板の段階でＤＳＣにて規定した組織は、この素材板から製造された、前記自動車パネルなどの部材の、人工時効処理時（ＢＨ時）の析出相の発生挙動に非常に良く相関している。この結果、前記部材をわざわざ製造せずとも、この素材板の段階で上記ＤＳＣを制御してやれば、この素材板の成形性とＢＨ性とを評価することができる。言い換えると、この素材板の段階で前記ＤＳＣにて規定される組織は、この素材板を成形素材とした部材における成形性やＢＨ性の指標となりうる。 As described above, the structure defined by DSC at the stage of the material plate is very much affected by the generation behavior of the precipitated phase during the artificial aging treatment (at the time of BH) of the member such as the automobile panel manufactured from the material plate. There is a good correlation. As a result, it is possible to evaluate the formability and BH property of the material plate by controlling the DSC at the stage of the material plate without bothering manufacturing the member. In other words, the structure defined by the DSC at the stage of the material plate can be an index of formability and BH property in a member using the material plate as a molding material.
　例えば、前記特許文献１では、１５０～２３０℃の温度範囲内に高さが３～１０μＷ／ｍｇである吸熱ピークが無く、反対に１００～２００℃の温度範囲に発熱ピークが存在している。前記特許文献２では、その図１の通り、１５０～２３０℃の温度範囲内に高さが３～１０μＷ／ｍｇである吸熱ピークが無い。前記特許文献３では、ＭｇとＳｉの合計量が１．２％以下であり、本発明で規定する吸熱ピークや発熱ピークを生成できず、人工時効硬化能が不足して、必要な強度が得られなくなる。前記特許文献４では、その図１の通り、１５０～２３０℃の温度範囲内に高さが３～１０μＷ／ｍｇである吸熱ピークが無く、２６０℃を超え、３３０℃以下の温度範囲内に、高さが２０μＷ／ｍｇを超える発熱ピークが存在している。前記特許文献５では、その図１の通り、１５０～２３０℃の温度範囲内に高さが３～１０μＷ／ｍｇである吸熱ピークがあり、２６０℃の位置に発熱ピークが存在しているが、発熱ピーク／吸熱ピークの比が３．５未満と小さ過ぎ、吸熱ピークの割合が高すぎる。 For example, in Patent Document 1, there is no endothermic peak having a height of 3 to 10 μW / mg in the temperature range of 150 to 230 ° C., and conversely, an exothermic peak is present in the temperature range of 100 to 200 ° C. In Patent Document 2, as shown in FIG. 1, there is no endothermic peak having a height of 3 to 10 μW / mg within a temperature range of 150 to 230 ° C. In Patent Document 3, the total amount of Mg and Si is 1.2% or less, the endothermic peak and the exothermic peak defined in the present invention cannot be generated, the artificial age hardening ability is insufficient, and the necessary strength is obtained. It becomes impossible. In Patent Document 4, as shown in FIG. 1, there is no endothermic peak having a height of 3 to 10 μW / mg in the temperature range of 150 to 230 ° C., and the temperature range is over 260 ° C. and below 330 ° C. There is an exothermic peak whose height exceeds 20 μW / mg. In Patent Document 5, as shown in FIG. 1, there is an endothermic peak having a height of 3 to 10 μW / mg within a temperature range of 150 to 230 ° C., and an exothermic peak is present at a position of 260 ° C. The ratio of exothermic peak / endothermic peak is too small, less than 3.5, and the ratio of endothermic peak is too high.
　したがって、これら従来のＤＳＣの吸熱ピークや発熱ピークの制御技術は、本発明で規定するＤＳＣの吸熱ピークや発熱ピークとは異なり、本発明が対象とする比較的高温の焼付塗装硬化条件においては、長時間の室温時効後の６０００系アルミニウム合金板の、高い伸び（成形性）と焼付塗装硬化性との両立ができない。 Therefore, the conventional DSC endothermic peak and exothermic peak control technique is different from the DSC endothermic peak and exothermic peak defined in the present invention. The high elongation (formability) and bake coating curability of the 6000 series aluminum alloy plate after long-term aging at room temperature cannot be achieved.
（ＤＳＣで規定する組織の制御方法）
　前記ＤＳＣの発熱ピークにより特定された組織の制御は、後述する通り、アルミニウム合金冷延板を、溶体化および焼入れ処理後１時間以内に、３０℃～６０℃の温度域で５時間以上、５００時間以下保持する、低温長時間の予備時効処理を施して行う。
　また、比較的低温でのＢＨ性を高くするためには、後述する通り、前記溶体化および焼入れ処理後１時間以内に、１００℃～３００℃の温度域で５秒以上、３００秒以下保持する、高温短時間の予備時効処理を施した上で、前記予備時効処理までを施して行う。このため、圧延板の、前記自動車部材として既に規格化されている６０００系アルミニウム合金組成を大きく変更することなく、また、常法による圧延工程を大きく変更することなく、制御できる利点がある。 (Organization control method prescribed by DSC)
Control of the structure specified by the DSC exothermic peak is performed as follows. The aluminum alloy cold-rolled sheet is heated within a temperature range of 30 ° C. to 60 ° C. for 5 hours or more, 500 hours or less within 1 hour after solution treatment and quenching treatment. Preliminary aging treatment at a low temperature for a long time is performed.
Further, in order to increase the BH property at a relatively low temperature, as will be described later, it is maintained within a temperature range of 100 ° C. to 300 ° C. for 5 seconds or more and 300 seconds or less within 1 hour after the solution treatment and quenching treatment. After the preliminary aging treatment at a high temperature for a short time, the preliminary aging treatment is performed. For this reason, there is an advantage that it can be controlled without greatly changing the composition of the 6000 series aluminum alloy already standardized as the automobile member of the rolled plate and without greatly changing the rolling process by a conventional method.
（製造方法）
　本発明の６０００系アルミニウム合金板は、鋳塊を均熱処理後に熱間圧延され、更に冷間圧延された冷延板であって、更に溶体化処理などの調質が施される、常法によって製造される。即ち、鋳造、均質化熱処理、熱間圧延の通常の各製造工程を経て製造され、板厚が２～１０ｍｍ程度であるアルミニウム合金熱延板とされる。次いで、冷間圧延されて板厚が３ｍｍ以下の冷延板とされる。 (Production method)
The 6000 series aluminum alloy sheet of the present invention is a cold-rolled sheet obtained by subjecting an ingot to hot rolling after soaking and then cold rolling, and further subjected to tempering such as solution treatment. Manufactured. That is, an aluminum alloy hot rolled sheet having a thickness of about 2 to 10 mm is manufactured through normal manufacturing processes such as casting, homogenization heat treatment, and hot rolling. Subsequently, it is cold-rolled to obtain a cold-rolled sheet having a thickness of 3 mm or less.
（溶解、鋳造）
　先ず、溶解、鋳造工程では、上記６０００系成分組成範囲内に溶解調整されたアルミニウム合金溶湯を、連続鋳造法、半連続鋳造法（ＤＣ鋳造法）等の通常の溶解鋳造法を適宜選択して鋳造する。ここで、本発明の規定範囲内にクラスタを制御するために、鋳造時の平均冷却速度について、液相線温度から固相線温度までを３０℃／分以上と、できるだけ大きく（速く）することが好ましい。このような、鋳造時の高温領域での温度（冷却速度）制御を行わない場合、この高温領域での冷却速度は必然的に遅くなる。すると、この高温領域での温度範囲で粗大に生成する晶出物の量が多くなって、鋳塊の板幅方向、厚さ方向での晶出物のサイズや量のばらつきも大きくなる。この結果、本発明の範囲に前記ＤＳＣを制御することができなくなる可能性が高くなる。 (Melting, casting)
First, in the melting and casting process, an ordinary molten casting method such as a continuous casting method and a semi-continuous casting method (DC casting method) is appropriately selected for the molten aluminum alloy adjusted to be dissolved within the above-mentioned 6000 series component composition range. Cast. Here, in order to control the cluster within the specified range of the present invention, the average cooling rate at the time of casting is as large as possible (fast) from the liquidus temperature to the solidus temperature of 30 ° C./min. Is preferred. When such temperature (cooling rate) control in the high temperature region during casting is not performed, the cooling rate in this high temperature region is inevitably slow. As a result, the amount of crystallized material generated roughly in the temperature range in this high temperature region increases, and the size and amount of crystallized material vary in the plate width direction and thickness direction of the ingot. As a result, there is a high possibility that the DSC cannot be controlled within the scope of the present invention.
　次いで、前記鋳造されたアルミニウム合金鋳塊に、熱間圧延に先立って、均質化熱処理を施す。この均質化熱処理（均熱処理）は、通常の目的である、組織の均質化（鋳塊組織中の結晶粒内の偏析をなくす）の他に、ＳｉやＭｇを充分に固溶させるために重要である。 Next, the cast aluminum alloy ingot is subjected to a homogenization heat treatment prior to hot rolling. This homogenization heat treatment (uniform heat treatment) is important for sufficiently dissolving Si and Mg in addition to the normal purpose of homogenizing the structure (eliminating segregation in crystal grains in the ingot structure). It is.
　均質化熱処理温度は、５００℃以上で、５８０℃以下、均質（保持）時間は１時間以上の範囲から適宜選択して、ＳｉやＭｇを充分に固溶させる。この均質化温度が低いと、ＳｉやＭｇの固溶量を確保できず、後述する溶体化・焼入れ処理後の予備時効処理（再加熱処理）によっても、前記したＤＳＣの発熱ピークの規定とできなくなる。また、結晶粒内の偏析を十分に無くすことができず、これが破壊の起点として作用するために、成形性が低下する。 The homogenization heat treatment temperature is 500 ° C. or more and 580 ° C. or less, and the homogenization (retention) time is appropriately selected from a range of 1 hour or more to sufficiently dissolve Si and Mg. If the homogenization temperature is low, the solid solution amount of Si and Mg cannot be secured, and the DSC exothermic peak can be defined by the pre-aging treatment (reheating treatment) after the solution treatment and quenching treatment described later. Disappear. Further, segregation in the crystal grains cannot be sufficiently eliminated, and this acts as a starting point of fracture, so that formability is lowered.
　この均質化熱処理を行った後、熱間圧延を行うが、均質化熱処理後の熱間での粗圧延開始まで、４５０℃以下には、鋳塊の温度を下げずに、ＳｉやＭｇの固溶量を確保することが好ましい。粗圧延開始までに、４５０℃以下に鋳塊の温度が下がった場合、ＳｉやＭｇが析出して、前記ＤＳＣの規定とするための、ＳｉやＭｇの固溶量が確保できない可能性が高くなる。 After this homogenization heat treatment, hot rolling is performed, but until the start of the hot rough rolling after the homogenization heat treatment, the temperature of the ingot is not lowered to 450 ° C. or lower without lowering the temperature of the ingot. It is preferable to ensure the amount of solution. When the temperature of the ingot is lowered to 450 ° C. or less by the start of rough rolling, Si and Mg are likely to precipitate, and there is a high possibility that the solid solution amount of Si and Mg cannot be secured for the purpose of the DSC. Become.
（熱間圧延）
　熱間圧延は、圧延する板厚に応じて、鋳塊（スラブ）の粗圧延工程と、仕上げ圧延工程とから構成される。これら粗圧延工程や仕上げ圧延工程では、リバース式あるいはタンデム式などの圧延機が適宜用いられる。 (Hot rolling)
Hot rolling is composed of a rough rolling process of an ingot (slab) and a finish rolling process according to the thickness of the sheet to be rolled. In these rough rolling process and finish rolling process, a reverse or tandem rolling mill is appropriately used.
　熱間粗圧延の開始から終了までの圧延中には、４００℃以下には温度を下げることなく、ＳｉやＭｇの固溶量を確保することが必要である。熱間粗圧延中に、４００℃以下に粗圧延板の温度が下がった場合、ＳｉやＭｇが析出して、前記ＤＳＣの規定とするための、ＳｉやＭｇの固溶量が確保できない、可能性が高くなる。 During rolling from the beginning to the end of hot rough rolling, it is necessary to secure a solid solution amount of Si or Mg without lowering the temperature to 400 ° C. or lower. During hot rough rolling, when the temperature of the rough rolled plate falls below 400 ° C., Si and Mg are precipitated, and it is not possible to secure a solid solution amount of Si or Mg for prescribing the DSC. Increases nature.
　このような熱間粗圧延後に、終了温度を２５０～３６０℃の範囲とした熱間仕上圧延を行う。前記した均熱温度や、この仕上げ圧延の終了温度が低すぎる場合には、均熱や熱延中に、Ｍｇ、Ｓｉ系の化合物が生成し、固溶Ｍｇ／Ｓｉのバランスが変化して、前記ＤＳＣの規定とすることが難しくなる。 After such hot rough rolling, hot finish rolling with an end temperature in the range of 250 to 360 ° C. is performed. If the soaking temperature or the finishing temperature of this finish rolling is too low, Mg and Si compounds are generated during soaking and hot rolling, and the balance of solid solution Mg / Si changes, It becomes difficult to make the DSC regulation.
（熱延板の焼鈍）
　この熱延板の冷間圧延前の焼鈍は必要ではないが、実施しても良い。 (Hot rolled sheet annealing)
Annealing of the hot-rolled sheet before cold rolling is not necessary, but may be performed.
（冷間圧延）
　冷間圧延では、上記熱延板を圧延して、所望の最終板厚の冷延板（コイルも含む）に製作する。但し、結晶粒をより微細化させるためには、冷間圧延率は６０％以上であることが望ましく、また前記焼鈍と同様の目的で、冷間圧延パス間で中間焼鈍を行っても良い。 (Cold rolling)
In the cold rolling, the hot-rolled sheet is rolled to produce a cold-rolled sheet (including a coil) having a desired final thickness. However, in order to further refine the crystal grains, the cold rolling rate is desirably 60% or more, and intermediate annealing may be performed between cold rolling passes for the same purpose as the annealing.
（溶体化および焼入れ処理）
　冷間圧延後、溶体化処理と、これに続く、室温までの焼入れ処理を行う。この溶体化焼入れ処理について、Ｍｇ、Ｓｉなどの各元素の十分な固溶量を得るためには、５００℃以上、溶融温度以下の溶体化処理温度に加熱することが望ましい。 (Solution and quenching)
After the cold rolling, solution treatment and subsequent quenching to room temperature are performed. In order to obtain a sufficient amount of solid solution of each element such as Mg and Si, it is desirable to heat to a solution treatment temperature not lower than 500 ° C. and not higher than a melting temperature.
　また、成形性を低下させる粗大な粒界化合物形成を抑制する観点から、溶体化温度から、室温の焼入れ停止温度までの平均冷却速度を２０℃／ｓ以上とすることが望ましい。溶体化処理後の室温までの焼入れ処理の平均冷却速度が小さいと、冷却中に粗大なＭｇ２Ｓｉおよび単体Ｓｉが生成してしまい、曲げ加工性が劣化してしまう。また、溶体化後の固溶量が低下し、ＢＨ性が低下してしまう。この冷却速度を確保するために、焼入れ処理は、ファンなどの空冷、ミスト、スプレー、浸漬等の水冷手段や条件を各々選択して用いる。 Further, from the viewpoint of suppressing the formation of coarse grain boundary compounds that lower the moldability, the average cooling rate from the solution temperature to the quenching stop temperature at room temperature is desirably 20 ° C./s or more. If the average cooling rate of the quenching treatment to room temperature after the solution treatment is small, coarse Mg 2 Si and simple substance Si are generated during cooling, and bending workability is deteriorated. Moreover, the amount of solid solution after solution forming falls, and BH property will fall. In order to ensure this cooling rate, the quenching treatment is performed by selecting water cooling means and conditions such as air cooling such as a fan, mist, spray, and immersion, respectively.
（予備時効処理：再加熱処理）
　このような溶体化処理後に焼入れ処理して室温まで冷却した後、１時間以内に冷延板を予備時効処理（再加熱処理）することが好ましい。この予備時効処理は、前記ＤＳＣのピークにより特定された組織の制御のために、常法よりも、低温、長時間として、３０℃～６０℃の温度域で５時間以上、５００時間以下保持する、低温長時間の予備時効処理を施して行うことが好ましい。これによって、ＭｇとＳｉのバランスが良いＭｇ－Ｓｉクラスタが形成され、前記ＤＳＣのピークにより特定された組織となる。したがって、低温長時間の予備時効処理によって、高い伸びと比較的高温でのＢＨ性が兼備できる。 (Preliminary aging treatment: reheating treatment)
After such a solution treatment, it is preferable to quench the steel sheet and cool it to room temperature, and then subject the cold-rolled sheet to a pre-aging treatment (reheating treatment) within one hour. This preliminary aging treatment is held at a temperature range of 30 ° C. to 60 ° C. for 5 hours or more and 500 hours or less as a lower temperature and longer time than the conventional method for the control of the structure specified by the DSC peak. It is preferable to perform a low-temperature long-time preliminary aging treatment. As a result, Mg—Si clusters with a good balance between Mg and Si are formed, and the structure specified by the DSC peak is obtained. Therefore, the high aging and the BH property at a relatively high temperature can be combined by the low-temperature long-time preliminary aging treatment.
　室温までの焼入れ処理終了後、予備時効処理開始（加熱開始）までの室温保持時間が長すぎると、室温時効により、吸熱ピークに対応するクラスタが多く生成しすぎてしまい、ＢＨ性が低くなりやすい。したがって、この室温保持時間は短いほど良く、溶体化および焼入れ処理と再加熱処理とが、時間差が殆ど無いように連続していても良く、下限の時間は特に設定しない。 If the room temperature holding time from the completion of the quenching treatment to room temperature until the start of the pre-aging treatment (heating start) is too long, too many clusters corresponding to endothermic peaks are generated due to room temperature aging, and the BH property tends to be low. . Accordingly, the shorter the room temperature holding time is better, the solution treatment and quenching treatment and the reheating treatment may be continued so that there is almost no time difference, and the lower limit time is not particularly set.
　また、前記予備時効温度が３０℃未満か、または保持時間が５時間未満であると、この予備時効処理をしない場合と同様となって、吸熱ピークに対応するクラスタが多く生成しすぎてしまい、ＢＨ性が低くなりやすい。一方、前記予備時効条件が６０℃を超える、または、５００時間を超えては、発熱ピークに相当する強化相および強化相の核となるクラスタの生成量が多すぎてしまい、焼付け塗装前のプレス成形時の強度が高くなりすぎ、成形性が劣化しやすい。 Further, if the preliminary aging temperature is less than 30 ° C. or the holding time is less than 5 hours, as in the case where this preliminary aging treatment is not performed, too many clusters corresponding to endothermic peaks are generated, BH property tends to be low. On the other hand, if the pre-aging condition exceeds 60 ° C. or exceeds 500 hours, the amount of clusters that form the core of the strengthening phase and the strengthening phase corresponding to the exothermic peak is too much, and the press before baking coating. The strength at the time of molding becomes too high, and the moldability tends to deteriorate.
　ここで、更に比較的低温でのＢＨ性を高くするためには、前記溶体化および焼入れ処理後１時間以内に、先ず、１００℃～３００℃の温度域で５秒以上、３００秒以下保持する、高温短時間の予備時効処理までを施した上で、直ちに前記低温長時間の予備時効処理を施して行うことが好ましい。これによって、前記低温長時間の予備時効処理によるＤＳＣの制御を確実なものとでき、ＤＳＣにおける１５０～２３０℃の温度範囲内の吸熱ピーク高さＡを、好ましい３～８μＷ／ｍｇの範囲、より好ましい３～７μＷ／ｍｇの範囲と制御できる。また、同じくＤＳＣにおける２３０℃以上、３３０℃未満の温度範囲内の発熱ピークの高さＢを、好ましい２０～４０μＷ／ｍｇの範囲、より好ましい２０～３５μＷ／ｍｇの範囲と制御できる。この高温短時間の予備時効処理を行わないか、行っても前記条件を外れた場合には、合金組成や製造履歴によっては、前記ＤＳＣのピークにより特定された組織とならない、あるいは比較的低温でのＢＨ性が低くなる可能性が生じる。 Here, in order to further improve the BH property at a relatively low temperature, first, within 1 hour after the solution treatment and the quenching treatment, first, the temperature is maintained at a temperature range of 100 ° C. to 300 ° C. for 5 seconds or more and 300 seconds or less. It is preferable to perform the preliminary aging treatment for a long time at a low temperature and immediately after the preliminary aging treatment for a short time at a high temperature. As a result, the DSC can be reliably controlled by the low-temperature long-time pre-aging treatment, and the endothermic peak height A in the temperature range of 150 to 230 ° C. in the DSC is more preferably in the range of 3 to 8 μW / mg. The preferred range is 3 to 7 μW / mg. Similarly, the height B of the exothermic peak in the temperature range of 230 ° C. or higher and lower than 330 ° C. in DSC can be controlled to be a preferable range of 20 to 40 μW / mg, and a more preferable range of 20 to 35 μW / mg. If this high temperature and short time pre-aging treatment is not performed or if the above conditions are not met, the structure specified by the DSC peak may not be obtained or the structure may be relatively low. There is a possibility that the BH property of the resin becomes low.
　このように、前記ＤＳＣのピークにより特定された組織とされて製造された本発明のアルミニウム合金板は、素材として、自動車などの大型ボディパネルなどにプレス成形された上で、塗装された後に焼付け塗装硬化処理（人工時効処理）されて高強度化される。この焼付け塗装硬化処理は、前記した通り、本発明の効果達成のためには、高温の方が好ましく、加熱温度１８０～２３０℃、加熱保持時間１０～３０分の条件が例示される。この焼付け塗装硬化処理条件から外れて、加熱温度が低すぎるなどすると、示差熱曲線で示す組織を前記した通り、より精緻に制御する必要がある。 As described above, the aluminum alloy plate of the present invention manufactured with the structure specified by the DSC peak is press-molded as a material on a large body panel or the like of an automobile and then baked after being painted. The coating is hardened (artificial aging treatment) to increase the strength. As described above, the baking coating curing treatment is preferably performed at a higher temperature in order to achieve the effects of the present invention, and examples include conditions of a heating temperature of 180 to 230 ° C. and a heating and holding time of 10 to 30 minutes. If the heating temperature is too low, for example, if the heating temperature is too low, the structure indicated by the differential heat curve needs to be more precisely controlled as described above.
　次に本発明の実施例を説明する。本発明のＤＳＣで規定する組織が異なる６０００系アルミニウム合金板を、組成や製造条件を変えて作り分けて製造した。そして、板製造後室温に１００日間保持後の、Ａｓ耐力（焼付け塗装硬化処理前の耐力）やＡＢ耐力（焼付け塗装硬化処理後の耐力）、破断伸び、ＢＨ性（塗装焼付け硬化性）を各々測定、評価した。これらの結果を表１、２に示す。 Next, examples of the present invention will be described. 6000 series aluminum alloy plates having different structures defined by the DSC of the present invention were produced by making different compositions and production conditions. And after Assembling the board, after holding at room temperature for 100 days, As proof strength (proof strength before baking coating hardening treatment), AB proof strength (proof strength after baking coating hardening treatment), elongation at break, BH property (paint bake hardening property), respectively Measurement and evaluation. These results are shown in Tables 1 and 2.
　具体的な前記作り分け方は、表１に示す組成の６０００系アルミニウム合金板を、表２に示すように、溶体化および焼入れ処理後の、予備時効処理条件を種々変えて行った。ここで、表１中の各元素の含有量の表示において、各元素における数値をブランクとしている表示は、その含有量が検出限界以下であることを示す。 Specifically, the above-described method of making the samples was carried out by changing the pre-aging treatment conditions of the 6000 series aluminum alloy plate having the composition shown in Table 1 after solution treatment and quenching treatment as shown in Table 2. Here, in the display of the content of each element in Table 1, the display in which the numerical value of each element is blank indicates that the content is below the detection limit.
（アルミニウム合金板の製造条件）
　アルミニウム合金板の具体的な製造条件は、前記予備時効処理条件を除き、各例とも以下の通り共通（同じ）とした。表１に示す各組成のアルミニウム合金鋳塊を、ＤＣ鋳造法により共通して溶製した。この際、各例とも共通して、鋳造時の平均冷却速度について、液相線温度から固相線温度までを５０℃／分とした。続いて、必要により面削を施した後の鋳塊を、５５０℃×１０時間の均熱処理をした後、その温度で熱間粗圧延を開始し、その後、終了温度を２５０～３６０℃の間とする熱間仕上圧延を行って熱間圧延板とした。この熱間圧延板を、加工率６７％の冷間圧延を行い、厚さ１．０ｍｍの冷延板とした。 (Production conditions for aluminum alloy sheets)
The specific production conditions of the aluminum alloy plate were the same (same) as follows in each example except for the preliminary aging treatment conditions. Aluminum alloy ingots having respective compositions shown in Table 1 were commonly melted by DC casting. At this time, in common with each example, the average cooling rate during casting was set to 50 ° C./min from the liquidus temperature to the solidus temperature. Subsequently, the ingot after chamfering as necessary is subjected to a soaking treatment at 550 ° C. for 10 hours, and then hot rough rolling is started at that temperature, and then the end temperature is set to 250 to 360 ° C. A hot finish rolling was performed to obtain a hot rolled sheet. This hot-rolled sheet was cold-rolled at a processing rate of 67% to obtain a cold-rolled sheet having a thickness of 1.0 mm.
　更に、この各冷延板を、硝石炉を用いて５５０℃にて１分の溶体化処理を行い、その後水冷を行うことで室温まで冷却した。この冷却後１時間以内に、表２に示す温度（℃）、保持時間（ｈｒ）にて、オイルバスを用いた高温短時間の予備時効および大気炉を用いた低温長時間の予備時効を行い、予備時効処理後は空冷を行った。 Further, each cold-rolled plate was subjected to a solution treatment for 1 minute at 550 ° C. using a glass furnace, and then cooled to room temperature by water cooling. Within 1 hour after this cooling, high temperature short time pre-aging using an oil bath and low temperature long time pre-aging using an atmospheric furnace are performed at the temperature (° C) and holding time (hr) shown in Table 2. After the preliminary aging treatment, air cooling was performed.
　これら調質処理後、１００日間室温放置した後の各最終製品板から、供試板（ブランク）３００ｍｍ×３００ｍｍを、製品の長手端部、幅中央部から、切り出し、各供試板の前記ＤＳＣや特性を測定、評価した。これらの結果を表２に示す。 After these tempering treatments, from each final product plate after standing at room temperature for 100 days, a test plate (blank) 300 mm × 300 mm was cut out from the longitudinal end portion and the width center portion of the product, and the DSC of each test plate was cut. And properties were measured and evaluated. These results are shown in Table 2.
（ＤＳＣ測定）
　前記供試板の板厚中央部の３箇所における組織の前記ＤＳＣを測定し、これら３箇所の平均値にて、この板のＤＳＣ（示差走査熱分析曲線）において、吸熱ピークの温度（℃）と高さ（μＷ／ｍｇ）、発熱ピークの温度（℃）と高さ（μＷ／ｍｇ）とを、各々測定した。なお、この結果を示した表２では、便宜的に１５０～２３０℃の温度範囲内の吸熱ピークを単に「吸熱ピーク」、２３０℃以上、３３０℃未満の温度範囲内の発熱ピークを「発熱ピーク」としている。 (DSC measurement)
The DSC of the structure at the three locations in the central part of the thickness of the test plate was measured, and the average value of these three locations was the endothermic peak temperature (° C) in the DSC (differential scanning calorimetry curve) of this plate. And height (μW / mg), exothermic peak temperature (° C.) and height (μW / mg) were measured. In Table 2 showing the results, for the sake of convenience, the endothermic peak in the temperature range of 150 to 230 ° C. is simply referred to as “endothermic peak”, and the exothermic peak in the temperature range of 230 ° C. or higher and lower than 330 ° C. is referred to as “exothermic peak”. "
　これらの前記供試板の各測定箇所における示差熱分析においては、試験装置：セイコ－インスツルメンツ製ＴＧ／ＤＴＡ６３００、標準物質：アルミ、試料容器：アルミ、昇温条件：１０℃／ｍｉｎ、雰囲気：アルゴン（５０ｍｌ／ｍｉｎ）、試料重量：３９．０～４１．０ｍｇの同一条件で各々行い、得られた示差熱分析のプロファイル（μＷ）を試料重量で割った（μＷ／ｍｇ）後に、前記示差熱分析プロファイルでの０～１００℃の区間において、示差熱分析のプロファイルが水平になる領域を０の基準レベルとし、この基準レベルからの吸熱ピーク高さ及び発熱ピーク高さを測定した。 In differential thermal analysis at each measurement location of these test plates, test equipment: TG / DTA6300 manufactured by Seiko Instruments, standard material: aluminum, sample container: aluminum, temperature rise condition: 10 ° C./min, atmosphere: argon (50 ml / min), sample weight: 39.0 to 41.0 mg, respectively. The obtained differential thermal analysis profile (μW) was divided by the sample weight (μW / mg), and then the differential heat In the section of 0 to 100 ° C. in the analysis profile, the region where the profile of differential thermal analysis was horizontal was taken as a reference level of 0, and the endothermic peak height and exothermic peak height from this reference level were measured.
塗装焼付硬化性
　前記供試板の機械的特性として、０．２％耐力（Ａｓ耐力）と破断伸び（％）を引張試験により求めた。また、これらの各供試板を各々共通して、前記自動車部材へのプレス成形を模擬した２％のストレッチ後に、高温での塗装焼付硬化処理として１８５℃×２０分、また、低温での塗装焼付硬化処理として１７０℃×２０分の、各人工時効硬化処理を各々施した後（ＢＨ後）の、供試板の０．２％耐力（ＡＢ耐力）を引張試験により求めた。そして、これら０．２％耐力同士の差（耐力の増加量）から各供試板のＢＨ性を評価したＢＨ後の０．２％耐力は、高温での塗装焼付硬化処理（１８５℃×２０分）では１９０ＭＰａ以上、低温での塗装焼付硬化処理（１７０℃×２０分）では最低でも１６０ＭＰａ以上、好ましくは１８０ＭＰａ以上で合格とし、プレス成形性の評価であるに破断伸びは２５％以上で合格とした。なお、プレス成形性の評価である破断伸びは、２４％と２５％との、わずか１％の違いが、例えば、自動車のアウタパネルの形状が先鋭化あるいは複雑化したコーナー部やキャラクターラインを、ひずみやしわがなく、美しく鮮鋭な曲面構成で成形できるかどうかに大きく影響する。 Paint bake hardenability As mechanical properties of the test plate, 0.2% yield strength (As yield strength) and elongation at break (%) were determined by a tensile test. In addition, each of these test plates is commonly used, and after 2% stretching simulating press molding on the automobile member, the coating baking and curing treatment at high temperature is 185 ° C. × 20 minutes, and the coating is performed at low temperature. The 0.2% yield strength (AB yield) of the test plate after each artificial age hardening treatment (after BH) of 170 ° C. × 20 minutes as the bake hardening treatment was determined by a tensile test. And the 0.2% proof stress after BH which evaluated the BH property of each test plate from the difference (increased proof stress) between these 0.2% proof stresses is the baking baking hardening process (185 degreeC * 20 at high temperature). 190) or more at a low temperature, and at least 170 MPa or more, preferably at 180 MPa or more, at a low temperature in a paint bake hardening process at a low temperature (170 ° C. × 20 minutes). It was. Note that the elongation at break, which is the evaluation of press formability, is only 1% difference between 24% and 25%. For example, corners and character lines with sharpened or complicated outer panel shapes of automobiles are distorted. It has a great influence on whether or not it can be molded with a beautiful and sharp curved surface structure without wrinkles.
　前記引張試験は、前記各供試板から、各々ＪＩＳＺ２２０１の１３号Ａ試験片（２０ｍｍ×８０ｍｍＧＬ×板厚）を採取し、室温にて引張り試験を行った。このときの試験片の引張り方向を圧延方向の直角方向とした。引張り速度は、０．２％耐力までは５ｍｍ／分、耐力以降は２０ｍｍ／分とした。機械的特性測定のＮ数は５とし、各々平均値で算出した。なお、前記ＢＨ後の耐力測定用の試験片には、この試験片に２％の予歪をこの引張試験機により与えた後に、前記ＢＨ処理を行った。 In the tensile test, No. 13A test piece (20 mm × 80 mmGL × plate thickness) of JISZ2201 was sampled from each test plate, and a tensile test was performed at room temperature. The tensile direction of the test piece at this time was the direction perpendicular 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. The test piece for measuring the yield strength after BH was subjected to the BH treatment after giving a pre-strain of 2% to the test piece by the tensile tester.
　表１、２に各々示す通り、発明例１～８は、本発明の成分組成範囲内で、かつ好ましい条件範囲で製造され、好ましい範囲で低温長時間の予備時効処理を施されている。このため、これら各発明例は、表２に示す通り、ＤＳＣが本発明で規定する通りであり、長期期間の室温時効後であっても、表２に示す通り、成形性やＢＨ性に優れている。
　具体的には、最低でも２６％以上の高い破断伸びと、最低でも１９２ＭＰａ以上の高温（１８５℃×２０分）のＢＨ性と、最低でも１６２ＭＰａ以上の低温（１７０℃×２０分）のＢＨ性を有している。
　更に、表２の発明例同士の比較において、高温短時間の予備時効処理を施した上で、直ちに前記低温長時間の予備時効処理を施した発明例２は、高温短時間の予備時効処理を施さず、低温長時間の予備時効処理のみを施した発明例１に比して、比較的低温でのＢＨ性が高くなっている。同じく、高温短時間の予備時効処理を施した上で、直ちに前記低温長時間の予備時効処理を施した発明例６、７、８は、高温短時間の予備時効処理を施さず、低温長時間の予備時効処理のみを施した発明例３、４、５に比して、合金組成の違いにもよるが、比較的低温でのＢＨ性が平均的に高くなっている。
　これは、発明例２、６、７、８が、高温短時間の予備時効処理を更に付加することで、ＤＳＣにおける１５０～２３０℃の温度範囲内の吸熱ピーク高さＡを、好ましい範囲（３～８μＷ／ｍｇ）や、より好ましい範囲（３～７μＷ／ｍｇ）、同じくＤＳＣにおける２３０℃以上、３３０℃未満の温度範囲内の発熱ピークの高さＢを、好ましい範囲（２０～４０μＷ／ｍｇ）や、より好ましい範囲（２０～３５μＷ／ｍｇ）に、より精緻に制御できていることによる。 As shown in Tables 1 and 2, Invention Examples 1 to 8 are produced in the component composition range of the present invention and in a preferable condition range, and subjected to a pre-aging treatment at a low temperature for a long time in the preferable range. Therefore, as shown in Table 2, these invention examples are as defined by DSC in the present invention. Even after long-term room temperature aging, as shown in Table 2, the moldability and BH properties are excellent. ing.
Specifically, it has a high elongation at break of at least 26%, a BH property of at least 192 MPa or higher (185 ° C. × 20 minutes), and a BH property of at least 162 MPa or more (170 ° C. × 20 minutes). have.
Furthermore, in the comparison between the inventive examples in Table 2, after the preliminary aging treatment at a high temperature and a short time was performed, the inventive example 2 which was immediately subjected to the low temperature and the long time preliminary aging treatment was subjected to the preliminary aging treatment at a high temperature and a short time. The BH property at a relatively low temperature is higher than that of Invention Example 1 in which only the preliminary aging treatment at a low temperature and a long time was performed without applying. Similarly, the invention examples 6, 7, and 8 that were subjected to the pre-aging treatment for a short time at a high temperature and immediately subjected to the pre-aging treatment for a long time at a low temperature were not subjected to the pre-aging treatment for a short time at a high temperature. Compared to Inventive Examples 3, 4 and 5 where only the preliminary aging treatment was performed, the BH property at a relatively low temperature is high on average although it depends on the difference in the alloy composition.
This is because the invention examples 2, 6, 7, and 8 further added a pre-aging treatment at high temperature and short time, so that the endothermic peak height A in the temperature range of 150 to 230 ° C. in DSC is within a preferable range (3 ~ 8 μW / mg), more preferable range (3 to 7 μW / mg), and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. in DSC is also preferable range (20 to 40 μW / mg) In addition, it is because it can be controlled more precisely within a more preferable range (20 to 35 μW / mg).
　これに対して、表２の比較例１～６は、発明例と同じ合金例１を用いている。しかし、これら各比較例は、表２に示す通り、予備時効処理の温度や保持時間などの製造条件が、好ましい条件を外れている。この結果、ＤＳＣが本発明で規定する範囲から外れ、同じ合金組成である発明例１に比して、長期間の室温時効後のＢＨ性か成形性かのいずれかが劣っており、兼備できていない。具体的には、破断伸びが２６％以上であっても、高温（１８５℃×２０分）でのＢＨ性が１９０ＭＰａ未満か、高温（１８５℃×２０分）でのＢＨ性が１９０ＭＰａ以上であっても、破断伸びが２５％未満となって、前記した合格基準を満足していない。 On the other hand, Comparative Examples 1 to 6 in Table 2 use the same alloy example 1 as the invention example. However, in each of these comparative examples, as shown in Table 2, the production conditions such as the temperature of the preliminary aging treatment and the holding time are out of the preferable conditions. As a result, DSC deviates from the range defined in the present invention, and either BH property or formability after long-term aging at room temperature is inferior to that of Invention Example 1 having the same alloy composition, and can be combined. Not. Specifically, even when the elongation at break is 26% or more, the BH property at a high temperature (185 ° C. × 20 minutes) is less than 190 MPa, or the BH property at a high temperature (185 ° C. × 20 minutes) is 190 MPa or more. However, the elongation at break is less than 25%, which does not satisfy the above acceptance criteria.
　このうち、比較例１は、予備時効処理していない。このため、１５０～２３０℃の温度範囲内に吸熱ピークが存在するものの、その高さＡが１０μＷ／ｍｇを超えて高すぎ、２３０℃以上、３３０℃未満の温度範囲内の発熱ピーク高さＢも５０μＷ／ｍｇを超えて高すぎる。
　比較例２は、低温側の予備時効処理の時間が短すぎる。このため、１５０～２３０℃の温度範囲内に吸熱ピークが存在するものの、その高さＡが１０μＷ／ｍｇを超えて高すぎ、２３０℃以上、３３０℃未満の温度範囲内の発熱ピーク高さＢも５０μＷ／ｍｇを超えて高すぎる。
　比較例３は、低温側の予備時効処理の温度が高すぎる。このため、１５０～２３０℃の温度範囲内に高さＡが３～１０μＷ／ｍｇである吸熱ピークが存在するものの、２３０℃以上、３３０℃未満の温度範囲内の発熱ピーク高さＢが２０μＷ／ｍｇ未満と低すぎる。
　比較例４は、低温側の予備時効処理の時間が長すぎる。このため、１５０～２３０℃の温度範囲内に吸熱ピークが存在するものの、その高さＡが３μＷ／ｍｇ未満と低すぎ、２３０℃以上、３３０℃未満の温度範囲内の発熱ピーク高さＢも２０μＷ／ｍｇ未満と低すぎる。
　比較例５は、高温側の予備時効処理の時間が長すぎる。このため、１５０～２３０℃の温度範囲内に吸熱ピークが存在するものの、その高さＡが３μＷ／ｍｇ未満と低すぎ、２３０℃以上、３３０℃未満の温度範囲内の発熱ピーク高さＢも２０μＷ／ｍｇ未満と低すぎる。
　比較例６は、低温側の予備時効処理の温度が高すぎる。このため、１５０～２３０℃の温度範囲内に吸熱ピークが存在するものの、その高さＡが３μＷ／ｍｇ未満と低すぎ、２３０℃以上、３３０℃未満の温度範囲内の発熱ピーク高さＢとの比Ｂ／Ａが１５．０を超えて大きすぎる。 Of these, Comparative Example 1 is not subjected to preliminary aging treatment. Therefore, although an endothermic peak exists in the temperature range of 150 to 230 ° C., the height A is too high exceeding 10 μW / mg, and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. Is too high, exceeding 50 μW / mg.
In Comparative Example 2, the time for the preliminary aging treatment on the low temperature side is too short. Therefore, although an endothermic peak exists in the temperature range of 150 to 230 ° C., the height A is too high exceeding 10 μW / mg, and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. Is too high, exceeding 50 μW / mg.
In Comparative Example 3, the temperature of the preliminary aging treatment on the low temperature side is too high. Therefore, although an endothermic peak having a height A of 3 to 10 μW / mg exists in a temperature range of 150 to 230 ° C., an exothermic peak height B in a temperature range of 230 ° C. or higher and lower than 330 ° C. is 20 μW / mg. It is too low with less than mg.
In Comparative Example 4, the time for the preliminary aging treatment on the low temperature side is too long. For this reason, although an endothermic peak exists in the temperature range of 150 to 230 ° C., the height A is too low as less than 3 μW / mg, and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. is also It is too low, less than 20 μW / mg.
In Comparative Example 5, the time for the pre-aging treatment on the high temperature side is too long. For this reason, although an endothermic peak exists in the temperature range of 150 to 230 ° C., the height A is too low as less than 3 μW / mg, and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. is also It is too low, less than 20 μW / mg.
In Comparative Example 6, the temperature of the pre-aging treatment on the low temperature side is too high. Therefore, although an endothermic peak exists in the temperature range of 150 to 230 ° C., the height A is too low as less than 3 μW / mg, and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. The ratio B / A exceeds 15.0 and is too large.
　表２の比較例７、８は、前記予備時効処理条件を含めて好ましい範囲で製造しているものの、表１の合金番号７、８を各々用いており、合金組成が各々本発明範囲を外れている。このため、これら比較例は、表２に示す通り、この結果、ＤＳＣなどが本発明で規定する範囲から外れ、発明例に比して、長期間の室温時効後のＢＨ性か成形性かのいずれかが劣っており、兼備できていない。具体的には、破断伸びが２５％以上であっても、高温（１８５℃×２０分）でのＢＨ性が１３８～１４６ＭＰａ程度、および低温（１７０℃×２０分）でのＢＨ性が１３３～１３９ＭＰａ程度しかない。 Although Comparative Examples 7 and 8 in Table 2 are manufactured in a preferable range including the pre-aging conditions, Alloy Nos. 7 and 8 in Table 1 are used, respectively, and the alloy compositions are out of the scope of the present invention. ing. For this reason, as shown in Table 2, these comparative examples, as a result, DSC and the like are out of the range defined in the present invention. Either is inferior and cannot be combined. Specifically, even when the elongation at break is 25% or more, the BH property at a high temperature (185 ° C. × 20 minutes) is about 138 to 146 MPa, and the BH property at a low temperature (170 ° C. × 20 minutes) is 133- Only about 139 MPa.
　比較例７は、表１の合金７であり、Ｍｇが少なすぎ、ＭｇとＳｉとの合計含有量の量も少なすぎる。このため、１５０～２３０℃の温度範囲内に吸熱ピークが存在するものの、その高さＡが３μＷ／ｍｇ未満と低すぎ、２３０℃以上、３３０℃未満の温度範囲内の発熱ピーク高さＢも２０μＷ／ｍｇ未満と低すぎる。
　比較例８は、表１の合金８であり、Ｓｉが少なすぎ、ＭｇとＳｉの合計含有量も少なすぎる。このため、１５０～２３０℃の温度範囲内に吸熱ピークが存在するものの、その高さＡが３μＷ／ｍｇ未満と低すぎ、２３０℃以上、３３０℃未満の温度範囲内の発熱ピーク高さＢも２０μＷ／ｍｇ未満と低すぎる。 The comparative example 7 is the alloy 7 of Table 1, and there is too little Mg and the quantity of the total content of Mg and Si is also too small. For this reason, although an endothermic peak exists in the temperature range of 150 to 230 ° C., the height A is too low as less than 3 μW / mg, and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. is also It is too low, less than 20 μW / mg.
The comparative example 8 is the alloy 8 of Table 1, Si is too little, and the total content of Mg and Si is too little. For this reason, although an endothermic peak exists in the temperature range of 150 to 230 ° C., the height A is too low as less than 3 μW / mg, and the exothermic peak height B in the temperature range of 230 ° C. or higher and lower than 330 ° C. is also It is too low, less than 20 μW / mg.
　これら発明例、比較例から選択したＤＳＣを図１に示す。図１において「Ｈｅａｔ　Ｆｌｏｗ」と記した縦軸の単位はμＷ／ｍであり、太い実線が表２の発明例１、太い点線（破線）が発明例２、細い点線が比較例３を示す。図１の通り、これら発明例では、１５０～２３０℃の温度範囲内に高さＡが３～１０μＷ／ｍｇである吸熱ピークが存在するとともに、高さＢが２０～５０μＷ／ｍｇである発熱ピークは２３０℃以上、２６０℃未満の温度範囲内に存在し、かつ、２６０℃以上、３３０℃未満の温度範囲には、高さが２０μＷ／ｍｇ以上の発熱ピークが存在していないことが分かる。 The DSC selected from these invention examples and comparative examples is shown in FIG. In FIG. 1, the unit of the vertical axis indicated as “Heat Flow” is μW / m, the thick solid line indicates Invention Example 1 in Table 2, the thick dotted line (broken line) indicates Invention Example 2, and the thin dotted line indicates Comparative Example 3. As shown in FIG. 1, in these inventive examples, an endothermic peak having a height A of 3 to 10 μW / mg exists in a temperature range of 150 to 230 ° C., and an exothermic peak having a height B of 20 to 50 μW / mg. Is present in a temperature range of 230 ° C. or more and less than 260 ° C., and in the temperature range of 260 ° C. or more and less than 330 ° C., no exothermic peak having a height of 20 μW / mg or more is present.
　以上の実施例の結果から、長時間の室温時効後や高温での焼付け塗装硬化処理であっても、良好な成形性と高いＢＨ性とを兼備するための、本発明で規定する組成やＤＳＣの各条件の臨界的な意義が裏付けられる。 From the results of the above examples, the composition and DSC specified in the present invention are required to combine good moldability and high BH properties even after baking at room temperature for a long time or at a high temperature by baking. The critical significance of each of these conditions is supported.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　本発明を詳細にまた特定の実施態様を参照して説明したが、本発明の精神と範囲を逸脱することなく様々な変更や修正を加えることができることは当業者にとって明らかである。
　本出願は、２０１６年３月３０日出願の日本特許出願（特願２０１６－０６７００７）、２０１６年１０月３１日出願の日本特許出願（特願２０１６－２１３７８９）に基づくものであり、その内容はここに参照として取り込まれる。 Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on March 30, 2016 (Japanese Patent Application No. 2016-067007) and a Japanese patent application filed on October 31, 2016 (Japanese Patent Application No. 2016-213789). Incorporated herein by reference.
　本発明によれば、長時間の室温時効後や高温での焼付け塗装硬化処理であっても、良好な成形性と高いＢＨ性とを兼備させた６０００系アルミニウム合金板を提供できる。すなわち、長時間の室温時効後であっても、良好な成形性と、前記高温での焼付け塗装硬化処理は勿論、前記従来の低温での焼付け塗装硬化処理においても高いＢＨ性とを兼備できる。この結果、パネル材を含めた自動車部材として、６０００系アルミニウム合金板の適用を拡大できる。 According to the present invention, it is possible to provide a 6000 series aluminum alloy plate that has both good formability and high BH properties even after baking at room temperature for a long time or at a high temperature by baking. That is, even after long-time aging at room temperature, it is possible to have both good moldability and high BH properties in the conventional low-temperature baking coating curing treatment as well as the conventional high-temperature baking coating curing treatment. As a result, the application of a 6000 series aluminum alloy plate can be expanded as an automobile member including a panel material.

Claims (9)

  1. 　質量％で、Ｍｇ：０．３～１．５％、Ｓｉ：０．６～１．５％を各々含有するとともに、前記Ｍｇ含有量とＳｉ含有量との合計が１．２％超であり、残部がＡｌ及び不可避的不純物からなるアルミニウム合金板であって、この板の示差走査熱分析曲線において、１５０～２３０℃の温度範囲内に高さＡが３～１０μＷ／ｍｇである吸熱ピークが存在するとともに、２３０℃以上、３３０℃未満の温度範囲内に高さＢが２０～５０μＷ／ｍｇである発熱ピークが存在し、かつ前記発熱ピークの中の最大ビーク高さＢと、前記吸熱ピークの中の最大ピーク高さＡとの比Ｂ／Ａが３．５超、１５．０未満であることを特徴とする成形性と焼付け塗装硬化性に優れたアルミニウム合金板。 In mass%, Mg: 0.3-1.5% and Si: 0.6-1.5% are contained, respectively, and the total of the Mg content and the Si content exceeds 1.2%. The balance is an aluminum alloy plate made of Al and inevitable impurities, and in the differential scanning calorimetry curve of this plate, an endothermic peak having a height A of 3 to 10 μW / mg within a temperature range of 150 to 230 ° C. And an exothermic peak having a height B of 20 to 50 μW / mg exists in a temperature range of 230 ° C. or higher and lower than 330 ° C., and the maximum beak height B in the exothermic peak, and the endothermic peak An aluminum alloy plate excellent in formability and bake hardenability, wherein the ratio B / A to the maximum peak height A is more than 3.5 and less than 15.0.
  2. 　前記吸熱ピークの高さＡが３～８μＷ／ｍｇであり、前記発熱ピークの高さＢが２０～４０μＷ／ｍｇである請求項１に記載の成形性と焼付け塗装硬化性に優れたアルミニウム合金板。 2. The aluminum alloy plate having excellent formability and bake hardenability according to claim 1, wherein the endothermic peak height A is 3 to 8 μW / mg, and the exothermic peak height B is 20 to 40 μW / mg. .
  3. 　前記アルミニウム合金板が、更に、質量％で、Ｃｕ：０．０２～０．８％、Ｆｅ：０．０５～０．５％、Ｍｎ：０．０５～０．３％、Ｚｒ：０．０４～０．１％、Ｃｒ：０．０４～０．３％、Ｖ：０．０２～０．１％、Ａｇ：０．０１～０．１％、Ｚｎ：０．０１～０．３％のうちの一種または二種以上を含有する請求項１または２に記載の成形性と焼付け塗装硬化性に優れたアルミニウム合金板。 The aluminum alloy plate is further, in mass%, Cu: 0.02 to 0.8%, Fe: 0.05 to 0.5%, Mn: 0.05 to 0.3%, Zr: 0.04. ~ 0.1%, Cr: 0.04 ~ 0.3%, V: 0.02 ~ 0.1%, Ag: 0.01 ~ 0.1%, Zn: 0.01 ~ 0.3% The aluminum alloy plate excellent in formability and baking coating curability according to claim 1 or 2, containing one or more of them.
  4. 　質量％で、Ｍｇ：０．３～１．５％、Ｓｉ：０．６～１．５％を各々含有するとともに、前記Ｍｇ含有量とＳｉ含有量との合計が１．２％超であり、残部がＡｌ及び不可避的不純物からなるアルミニウム合金冷延板を、溶体化および焼入れ処理後１時間以内に、３０℃～６０℃の温度域で５時間以上、５００時間以下保持する、低温長時間の予備時効処理を施すことによって、この板の人工時効処理される前の示差走査熱分析曲線において、１５０～２３０℃の温度範囲内に高さＡが３～１０μＷ／ｍｇである吸熱ピークを存在させるとともに、２３０℃以上、３３０℃未満の温度範囲内に高さＢが２０～５０μＷ／ｍｇである発熱ピークを存在させ、かつ前記発熱ピーク高さＢと前記吸熱ピーク高さＡとの比Ｂ／Ａを３．５超、１５．０未満としたことを特徴とする成形性と焼付け塗装硬化性に優れたアルミニウム合金板の製造方法。 In mass%, Mg: 0.3-1.5% and Si: 0.6-1.5% are contained, respectively, and the total of the Mg content and the Si content exceeds 1.2%. Hold the aluminum alloy cold-rolled sheet consisting of Al and inevitable impurities in the temperature range of 30 ° C. to 60 ° C. for 5 hours or more and 500 hours or less within 1 hour after solution treatment and quenching treatment. In the differential scanning calorimetry curve before artificial aging treatment of this plate, an endothermic peak having a height A of 3 to 10 μW / mg exists in a temperature range of 150 to 230 ° C. And an exothermic peak having a height B of 20 to 50 μW / mg is present in a temperature range of 230 ° C. or higher and lower than 330 ° C., and the ratio B between the exothermic peak height B and the endothermic peak height A / A over 3.5, 15.0 not A method for producing an aluminum alloy plate excellent in formability and bake hardenability, characterized by being filled.
  5. 　前記アルミニウム合金板が、更に、質量％で、Ｃｕ：０．０２～０．８％、Ｆｅ：０．０５～０．５％、Ｍｎ：０．０５～０．３％、Ｚｒ：０．０４～０．１％、Ｃｒ：０．０４～０．３％、Ｖ：０．０２～０．１％、Ａｇ：０．０１～０．１％、Ｚｎ：０．０１～０．３％のうちの一種または二種以上を含有する請求項４記載の成形性と焼付け塗装硬化性に優れたアルミニウム合金板の製造方法。 The aluminum alloy plate is further, in mass%, Cu: 0.02 to 0.8%, Fe: 0.05 to 0.5%, Mn: 0.05 to 0.3%, Zr: 0.04. ~ 0.1%, Cr: 0.04 ~ 0.3%, V: 0.02 ~ 0.1%, Ag: 0.01 ~ 0.1%, Zn: 0.01 ~ 0.3% The manufacturing method of the aluminum alloy plate excellent in the moldability and baking coating curability of Claim 4 containing 1 type or 2 types or more of them.
  6. 　前記溶体化および焼入れ処理後１時間以内に、１００℃～３００℃の温度域で５秒以上、３００秒以下保持する高温短時間の予備時効処理を施した上で、前記低温長時間の予備時効処理までを施す、請求項４または５に記載の成形性と焼付け塗装硬化性に優れたアルミニウム合金板の製造方法。 Within one hour after the solution treatment and quenching treatment, a high temperature short time pre-aging treatment is performed in a temperature range of 100 ° C. to 300 ° C. for 5 seconds or more and 300 seconds or less, and then the low temperature long time pre aging treatment is performed. The method for producing an aluminum alloy plate excellent in formability and bake hardenability according to claim 4 or 5, wherein the processing is performed.
  7. 　前記アルミニウム合金板が、成形された後で塗装され、加熱温度１８０～２３０℃、加熱保持時間１０～３０分の条件で焼付け塗装硬化処理される請求項４に記載の成形性と焼付け塗装硬化性に優れたアルミニウム合金板の製造方法。 5. The formability and bake-coating curability according to claim 4, wherein the aluminum alloy sheet is coated after being formed and subjected to a bake-coating hardening process under conditions of a heating temperature of 180 to 230 ° C. and a heating and holding time of 10 to 30 minutes. Method for producing an aluminum alloy sheet excellent in the thickness.
  8. 　前記アルミニウム合金板が、成形された後で塗装され、加熱温度１８０～２３０℃、加熱保持時間１０～３０分の条件で焼付け塗装硬化処理される請求項５に記載の成形性と焼付け塗装硬化性に優れたアルミニウム合金板の製造方法。 6. The formability and bake-coating curability according to claim 5, wherein the aluminum alloy sheet is coated after being formed and subjected to a bake-coating hardening process under conditions of a heating temperature of 180 to 230 ° C. and a heating and holding time of 10 to 30 minutes. Method for producing an aluminum alloy sheet excellent in the thickness.
  9. 　前記アルミニウム合金板が、成形された後で塗装され、加熱温度１８０～２３０℃、加熱保持時間１０～３０分の条件で焼付け塗装硬化処理される請求項６に記載の成形性と焼付け塗装硬化性に優れたアルミニウム合金板の製造方法。 The formability and bake-coating curability according to claim 6, wherein the aluminum alloy sheet is coated after being formed and subjected to a bake-coating curing treatment under conditions of a heating temperature of 180 to 230 ° C and a heating and holding time of 10 to 30 minutes. Method for producing an aluminum alloy sheet excellent in the thickness.
PCT/JP2017/013179 2016-03-30 2017-03-30 Aluminum alloy sheet and aluminum alloy sheet manufacturing method WO2017170835A1 (en)

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CN112410628A (en) * 2020-12-03 2021-02-26 河南永通铝业有限公司 High-strength aluminum alloy plate for curtain wall and preparation method thereof

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CN111247260A (en) * 2017-10-23 2020-06-05 诺维尔里斯公司 High-strength highly-formable aluminum alloy and manufacturing method thereof
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