KR101667504B1 - Aluminum alloy plate exhibiting excellent baking finish hardening properties - Google Patents

Aluminum alloy plate exhibiting excellent baking finish hardening properties Download PDF

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KR101667504B1
KR101667504B1 KR1020157006595A KR20157006595A KR101667504B1 KR 101667504 B1 KR101667504 B1 KR 101667504B1 KR 1020157006595 A KR1020157006595 A KR 1020157006595A KR 20157006595 A KR20157006595 A KR 20157006595A KR 101667504 B1 KR101667504 B1 KR 101667504B1
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atoms
clusters
atom
aluminum alloy
treatment
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KR1020157006595A
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KR20150038662A (en
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히사오 시시도
가츠시 마츠모토
야스히로 아루가
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가부시키가이샤 고베 세이코쇼
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Priority to JPJP-P-2012-205839 priority Critical
Priority to JP2012205839A priority patent/JP5852534B2/en
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Priority to PCT/JP2013/074700 priority patent/WO2014046010A1/en
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C21/00Alloys based on aluminium
    • C22C21/02Alloys based on aluminium with silicon as the next major constituent
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C21/00Alloys based on aluminium
    • C22C21/06Alloys based on aluminium with magnesium as the next major constituent
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C21/00Alloys based on aluminium
    • C22C21/06Alloys based on aluminium with magnesium as the next major constituent
    • C22C21/08Alloys based on aluminium with magnesium as the next major constituent with silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22FCHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/05Changing 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
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21BROLLING OF METAL
    • B21B3/00Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B21B2003/001Aluminium or its alloys

Abstract

It is an object of the present invention to provide a specific cluster of a specific 6000-series aluminum alloy plate having a large effect on BH property measured by a three-dimensional atom probe electric field ion microscope at a predetermined number of densities or more, , The ratio of clusters having a large number of atoms of Mg is controlled so as to further improve the BH property after room temperature aging. A 6000-series aluminum alloy plate which also has a BH property after aging at room temperature and a formability after aging at room temperature.

Description

[0001] ALUMINUM ALLOY PLATE EXHIBITING EXCELLENT BAKING FINISH HARDENING PROPERTIES [0002]
The present invention relates to an Al-Mg-Si-based aluminum alloy plate. The aluminum alloy sheet referred to in the present invention is a rolled sheet such as a hot rolled sheet or a cold rolled sheet and is subjected to tempering such as solution treatment and quenching treatment and then subjected to heat treatment such as baking paint hardening treatment, . In the following description, aluminum is also referred to as Al.
In recent years, the social demands for lightening the weight of vehicles such as automobiles have been increasingly increasing in the global environment. In order to meet such a demand, it has been desired to provide a material for a large-sized body panel (outer panel, inner panel) such as a car panel, particularly a hood, a door and a loop, Of aluminum alloys have been increasing.
Among these panels, panels such as an outer panel (outer plate) and an inner panel (inner plate) of a panel structure such as a hood, a fender, a door, a loop lid and the like of a car are thin and high strength aluminum alloy plates, Use of an Mg-Si-based to JIS 6000 series (hereinafter simply referred to as a 6000-series) aluminum alloy plate has been studied.
The 6000-series aluminum alloy plate essentially contains Si and Mg, and in particular, the excess Si-type 6000-series aluminum alloy has a composition of Si / Mg of 1 or more in mass ratio and has excellent age hardenability. Therefore, at the time of press forming or bending, the moldability is ensured by the lowering of the yield stress and the aging is cured by heating at the time of artificial aging (curing) treatment such as paint baking treatment of the molded panel, And baking paint hardenability (hereinafter, also referred to as baking hardness = BH property or baking hardenability) that can secure the necessary strength as a panel.
In addition, the 6000-series aluminum alloy sheet has a relatively small amount of the alloy element, compared with 5000-series aluminum alloy having a large amount of alloy such as Mg amount. Therefore, when scraps of these 6000-series aluminum alloy sheets are reused as aluminum alloy melting materials (dissolving raw materials), the original 6000-series aluminum alloy ingots are easily obtained and the recyclability is also excellent.
On the other hand, as is well known, an outer panel of an automobile is produced by combining an aluminum alloy plate with a molding process such as elongation molding in press molding or bending. For example, in a large-sized outer panel such as a hood or a door, a molded product is formed as an outer panel by press molding such as projection, and then, by hemming (hemming) such as flat hem of the outer panel, , And joining with the inner panel is performed to form a panel structure.
Here, the 6000-series aluminum alloy has an advantage of having excellent BH properties, but has an aging property at room temperature, and after the solution quenching treatment, the temperature is kept at room temperature for several months, , In particular, the bending workability is lowered. For example, when a 6000-series aluminum alloy sheet is used for an automobile panel, it is usually quenched with an aluminum maker (after manufacturing), molded into a panel by a car maker, (Left at room temperature), and during this time, the age hardening (room temperature aging) becomes considerable. Particularly, in an outer panel in which severe bending is performed, there is a problem that, even if it can be molded without any problem immediately after production, cracking occurs during heme processing after age hardening (room temperature aging).
 In addition, when such a room temperature aging is large, the BH property is lowered, and even when the panel is subjected to the artificial aging (curing) treatment such as the baking treatment of the panel after the molding, Problems also arise.
As a result, various proposals have heretofore been made for improving the BH property and the room temperature aging of the 6000-series aluminum alloy. For example, in Patent Document 1, proposals have been made to suppress the change in strength after 7 days to 90 days after the production at room temperature after the cooling step is changed stepwise during the solution treatment and the quenching treatment. Also, in Patent Document 2, proposals have been made to obtain BH performance and shape durability by holding at 50 to 150 ° C for 10 to 300 minutes within 60 minutes after solution treatment and quenching treatment. In Patent Document 3, proposals have been made to obtain BH performance and shape dynamics by defining the cooling temperature at the first stage and the cooling rate thereafter at the time of solution treatment and quenching treatment.
In Patent Document 4, it is proposed to improve the BH property by heat treatment after solution quenching. Patent Document 5 proposes improvement of BH property by the endothermic peak specification of DSC (Differential scanning calorimetry) method. In Patent Document 6, improvement of BH property by the exothermic peak specification of DSC is proposed similarly.
However, in these Patent Documents 1 to 6, clusters (aggregates of atoms) directly affecting the BH properties and the room temperature aging properties of the 6000-series aluminum alloy plates are merely indirectly analogous to their behaviors.
On the other hand, in Patent Document 7, attempts have been made to directly measure and specify clusters (aggregates of atoms) affecting BH properties and room temperature aging properties of a 6000-series aluminum alloy plate. That is, the average number density of clusters having a circle equivalent diameter in the range of 1 to 5 nm among the clusters (aggregates of atoms) observed when the structure of the 6000-system aluminum alloy plate is analyzed by a transmission electron microscope with a transmission of 1 million times is from 4,000 to 30,000 / 2 , so that the BH property is excellent and the room temperature aging is suppressed.
Japanese Patent Application Laid-Open No. 2000-160310 Japanese Patent No. 3207413 Japanese Patent No. 2614686 Japanese Patent Application Laid-Open No. 4-210456 Japanese Patent Application Laid-Open No. 10-219382 Japanese Patent Application Laid-Open No. 2005-139537 Japanese Patent Application Laid-Open No. 2009-242904
However, the demand for improving the fuel efficiency of automobiles is higher than ever, and further weight reduction is being promoted. This tends to require thinning of the aluminum alloy sheet, but the BH property of the conventional aluminum alloy is insufficient. This is because these prior art techniques are based on the observation of the indirect behavior due to the characteristics and DSC measurement of aggregates of atoms (clusters), or the control of the size and number density of relatively large aggregates of atoms evaluated by TEM observation There is also something. In other words, these conventional techniques can not evaluate the aggregate of atoms in detail, and therefore, the precise control of the atomic assembly is also insufficient.
SUMMARY OF THE INVENTION It is an object of the present invention to provide an Al-Si-Mg-based aluminum alloy capable of exhibiting high BH performance and good processability even in a vehicle body baking treatment after room temperature aging, Plate.
In order to attain this object, the essential point of the aluminum alloy plate excellent in baking painting hardenability of the present invention is that it contains 0.2 to 2.0% of Mg and 0.3 to 2.0% of Si in mass%, the balance being Al and inevitable impurities Is an Al-Mg-Si-based aluminum alloy plate containing a total of 10 or more Mg atoms and / or Si atoms as aggregates of atoms measured by a three-dimensional atom probe electric field ion microscope , An atom which satisfies the condition that the distance between one atom of the reference atom and another atom adjacent to the atom is 0.75 nm or less even if either of the atoms of the Mg atom or Si atom included in these atoms is taken as an atom (Mg / Si) of at least 2/3 of the number of Mg atoms and Si atoms among the aggregates of atoms satisfying these conditions and having an average number density of 1.0 x 10 24 / m 3 or more, If the average ratio is greater than or equal to 0.65 .
In the present invention, it is presumed that many fine clusters having a distance of 0.75 nm or less among the atoms among the aggregates (clusters) of atoms measured by 3DAP are present. Further, among the elements constituting these fine clusters, the ratio of clusters having a large number of atoms of Mg is increased to increase the BH property.
The inventors of the present invention have found that clusters rich in Si atoms adversely affect BH properties, while clusters rich in Mg atoms promote BH properties, even if they are the same cluster. Therefore, in the present invention, it is controlled so as to increase the number of clusters whose distances between the atoms are small among the clusters measured by 3DAP, and in order to increase the ratio of clusters having a large number of atoms of Mg Increase BH province.
Thus, in the present invention, it is possible to provide an Al-Si-Mg-based aluminum alloy plate capable of exhibiting a higher BH property even at room temperature aging.
Hereinafter, the embodiments of the present invention will be described in detail for each of the requirements.
Cluster (cluster of atoms):
First, the meaning of the cluster in the present invention will be described. The cluster in the present invention refers to an aggregate (cluster) of atoms measured by 3DAP, which will be described later, and is mainly referred to as a cluster in the following description. In the 6000-series aluminum alloy, it is known that Mg and Si form aggregates of atoms called clusters after solution treatment and quenching treatment, at room temperature, or during heat treatment at 50 to 150 ° C. However, clusters formed during the holding at room temperature and the heat treatment at 50 to 150 占 폚 are completely different in behavior.
 The clusters formed in the room temperature holding suppress precipitation of the GP zone or the beta phase to increase the strength in the subsequent artificial aging or baking painting treatment. On the other hand, clusters (or Mg / Si clusters) formed at 50 to 150 占 폚 show, on the contrary, promoting precipitation in the GP zone or? 'Phase (see, for example, Yamada et al. ).
Incidentally, in Patent Document 7, it is described that, throughout the paragraphs 0021 to 0025, these clusters are conventionally analyzed by specific heat measurement or 3DAP (3D atom probe). At the same time, in the analysis of clusters by 3DAP, it is described that even though the presence of the clusters themselves is supported, the size and number density of clusters specified in the present invention can be measured only in an unknown or definite manner.
Obviously, in the 6000-series aluminum alloy, an attempt has been made to interpret the cluster by 3DAP (3D atom probe). However, as described in Patent Document 7, even if the presence of the cluster itself is supported, the size and number density of the cluster are unclear. This is because it is unclear whether the cluster of atoms (clusters) measured by 3DAP largely correlates with the BH property, and it is unclear which cluster of atoms largely related to the BH property is unclear.
On the contrary, in the Japanese Patent Application No. 2011-56960 filed by the present inventors, the present inventors clarified clusters largely related to the BH property. That is, in the clusters measured by 3DAP, a specific cluster containing a certain number of Mg atoms and Si atoms in total as specified above, and the distance between adjacent atoms included in the specific cluster is not more than a specific value, . It was also found that by increasing the number density of aggregates of atoms satisfying these conditions, high BH properties can be exerted even when the body paint is baked after room temperature aging.
Specifically, in the above-mentioned Japanese Patent Application No. 2011-56960, it is preferable that, in mass%, 0.2 to 2.0% of Mg and 0.3 to 2.0% of Si are contained, and the remaining amount of Al and Mg containing inevitable impurities -Si-based aluminum alloy plate, which is an aggregate of atoms measured by a three-dimensional atom probe electric field ion microscope, wherein the aggregate of the atoms contains at least 30 or more of Mg atoms and / or Si atoms in total, The distance between the reference atom and any other atom adjacent to the reference atom is 0.75 nm or less and the atom satisfying these conditions Having an average number density of 1.0 × 10 5 / μm 3 or more.
According to this Japanese Patent Application No. 2011-56960, the presence of a cluster including at least one of Mg atoms and Si atoms or a total of at least 30 atoms and the distance between atoms adjacent to each other is 0.75 nm or less, . By presenting these clusters in a certain amount or more, the Al-Si-Mg based aluminum alloy sheet which has been aged at room temperature can exhibit a higher BH property even in the case of the low temperature and short time baking of the body coating at 150 DEG C for 20 minutes It can be said.
On the contrary, the inventors of the present invention have found that, among the clusters measured by 3DAP, the presence of a large number of clusters surely improves the BH property, but the improvement effect is not sufficient by itself. In other words, although it is a prerequisite (necessary condition) for improving the BH property, it is not necessarily sufficient to provide the cluster in a large number.
For this reason, the present inventors filed a Japanese Patent Application No. 2011-199769 (filed on September 13, 2011). That is, on the premise that the aggregate of atoms satisfying the above-mentioned specific condition is contained at an average number density of 6.0 x 10 23 atoms / m 3 or more, the radius of the circle equivalent diameter which becomes the maximum among the aggregates of atoms satisfying these conditions is 1.5 for regulating the mean number density of the aggregates of a size of less than atom nm to less than 10.0 × 10 23 gae / m 3 the other hand, the average of the maximum to the phosphorus atom aggregate size of less than the radius of the circle-equivalent diameter of 1.5nm which a number density (a) And a ratio (a / b) of the atomic aggregate average number density (b) having a maximum circle diameter of 1.5 nm or more to a maximum is 3.5 or less, and the radius of the circle- Phosphorus atom aggregates.
This application is based on the idea that there is a difference (distribution) in the size (size) of the clusters containing either one or both of the Mg atom and the Si atom and that there is a large difference in the effect on the BH- . There is a diametrically opposite difference in the effect of the cluster size on the BH property that a cluster of relatively small size inhibits BH property while a cluster of relatively large size promotes BH property. On the basis of this, it is possible to improve the BH property by reducing the number of clusters of a relatively small size and increasing the number of clusters of a relatively large size among the specific clusters. Clusters of a relatively small size disappear at the time of BH treatment (artificial age hardening treatment), but rather at the time of BH, precipitation of large clusters, which are highly effective in improving the strength, is inhibited and the BH property is lowered. On the other hand, clusters of relatively large size grow at the time of BH treatment, promote precipitation of precipitates at the time of BH treatment, and increase the BH property.
However, according to the succeeding research, even if the clusters are relatively large in size, clusters that are too large grow too large in size when grown at the time of BH treatment, which in turn deteriorates the BH property and the strength before BH treatment becomes too high It was also found that the workability deteriorates. That is, in order to increase the BH property without deteriorating workability, there is a cluster of the optimum size. Although the distribution of the size of the specific atom aggregate is important, the average radius of the circle-equivalent diameter, which is the average size of the cluster of the specific atoms, and the standard deviation of the radius of the circle- Respectively. The present inventors have also filed this application as Japanese Patent Application No. 2012-051821 (filed on Mar. 8, 2012). This Japanese Patent Application No. 2012-051821 discloses that the average radius of the circle equivalent diameter of the clusters is 1.2 nm or more and 1.5 nm or less and the standard deviation of the radius of the circle equivalent diameter is 0.35 nm or less, Only clusters are generated.
However, as a result of further studies, it has been found that, even in the same clusters as described above, the influence on the BH property differs depending on the composition, the clusters rich in Si atoms adversely affect the BH properties, while the clusters rich in Mg atoms have BH properties . This is the thinking mode of the present invention. Thus, according to the present invention, it is possible to control so that the number of clusters having small distances between the atoms among the clusters measured by 3DAP increases, and in this cluster, To increase the BH property.
(Cluster specification of the present invention)
Hereinafter, the cluster specification of the present invention will be described in detail.
As described above, the aluminum alloy plate defining the clusters of the present invention is a plate after a series of tempering such as solution solidification, quenching treatment, reheating treatment, etc. is performed after rolling and is subjected to artificial aging hardening treatment such as baking painting hardening treatment Refers to the previous aluminum alloy plate. However, in order to press-mold the automobile panel or the like, it is often left at room temperature over a relatively long period of about 0.5 to 4 months after the production of the plate. Therefore, even in the state of the plate after being left at room temperature over the long term, it is preferable to make the structure specified in the present invention. In this regard, when the characteristics after long-term room temperature aging is a problem, it is expected that the characteristics will not change and the structure will not change after a lapse of about 100 days at room temperature, so that the above series of tempering It is more preferable to investigate and evaluate the structure and properties of the plate after 100 days or more have passed.
(Definition of cluster of the present invention)
The structure of this aluminum alloy plate at an arbitrary plate thickness central portion is measured by a three-dimensional atom probe electric field ion microscope. As a cluster existing in the measured tissue, in the present invention, it is assumed that the cluster contains at least 10 or more of Mg atoms and / or Si atoms in total. The upper limit of the number of Mg atoms and Si atoms contained in this cluster is not particularly limited, but from the viewpoint of the production limit, the upper limit of the number of Mg atoms and Si atoms contained in this cluster is roughly It is about 10,000.
In Japanese Patent Application No. 2011-56960, it is supposed that the cluster includes at least 30 or more of Mg atoms and Si atoms in total. However, according to the present invention, as described above, the clusters of a relatively small size inhibit the BH property, so that it is regulated to be smaller. For this reason, in order to control the cluster of a relatively small size to be regulated in a measurable range, it is specified that at least 10 or more of Mg atoms and / or Si atoms are included in total.
In the present invention, similar to the above-mentioned Japanese Patent Application No. 2011-56960, even if one of the atoms of the Mg atom and the Si atom included in these clusters is used as a reference, any of atoms adjacent to the reference atom (Clusters) of atoms (satisfying the requirements of the present invention) defined in the present invention are set so that the distance between one atom and each other is 0.75 nm or less. The distance of 0.75 nm between them ensures that the distances between atoms of Mg and Si are close to each other and that the number density of large size clusters having BH property improving effect after room temperature aging is ensured and conversely, This is the figure we set to control water density. The inventors of the present invention have studied in detail the relationship between an aluminum alloy plate capable of exhibiting high BH property in a body coating baking treatment and an atomic level aggregate. As a result, it has been found that the number density of the atomic aggregates defined in the above- (BH). Therefore, although the technical meaning of the distance of 0.75 nm between atoms is not fully understood, it is necessary for strictly ensuring the density of the atomic aggregates exhibiting high BH properties, and is a numerical value determined for this purpose.
The cluster specified in the present invention most often includes both Mg atoms and Si atoms, but includes a case including a Mg atom but not including a Si atom, and a case including a Si atom but not including a Mg atom do. In addition, it is not limited to Mg atoms or Si atoms alone, but includes Al atoms at a very high probability.
 In addition, depending on the composition of the aluminum alloy sheet, the valence clusters of Fe, Mn, Cu, Cr, Zr, V, Ti, Zn or Ag contained as the alloying elements or impurities are included in clusters. As shown in Fig. However, even if these other atoms (derived from alloying elements or impurities) are included in the cluster, they are at a lower level than the total number of Mg atoms and Si atoms. Therefore, even when such other atoms are included in a cluster, the cluster of the present invention which satisfies the above-described condition (function) functions in the same manner as a cluster containing only Mg atoms and Si atoms. Therefore, the clusters defined in the present invention may contain any atoms other than those described above even if they satisfy the above-mentioned rule.
Further, in the present invention, the distance between any one atom of the reference atom and another atom adjacent to the reference is 0.75 mm or less even if either of the Mg atom or the Si atom contained in these atoms is referred to Means that all Mg atoms and Si atoms present in the cluster have at least one Mg atom or Si atom whose distance therebetween is 0.75 nm or less.
The distances between the atoms in the cluster of the present invention are defined so that the distances of all the atoms among atoms other than the reference atom and the reference atom are the same It may not be 0.75 nm or less in all, or may be 0.75 nm or less in all cases. In other words, other Mg atoms or Si atoms having a distance exceeding 0.75 nm may be adjacent to each other, and Mg atoms and Si atoms which are adjacent to a specific (reference) Mg atom or Si atom, At least one Si atom is required.
When there is one adjacent Mg atom or Si atom satisfying the specified distance, the number of Mg atoms and Si atoms to be counted that satisfy the distance condition is not limited to a specific (standard) Mg atom or 2 atoms including Si atoms. When there are two adjacent Mg atoms or two Si atoms satisfying the specified distance, the number of Mg atoms and Si atoms to be counted, which satisfy the distance condition, 3 atoms including Si atoms.
The clusters described above are clusters produced by the above-mentioned solution-forming in the tempering after rolling and the temperature holding treatment after quenching at high temperature, which will be described later and more specifically, to be described later. That is, the clusters in the present invention are aggregates of atoms formed by solution treatment and temperature holding treatment after quenching at high temperature, and contain at least 10 or more of Mg atoms and Si atoms in total, Is a cluster in which the distance between any one atom of the reference atom and another atom adjacent to the reference atom is 0.75 nm or less even if either of the Mg atom or the Si atom contained in the reference atom is referred to.
Up to now, clusters that promote precipitation in the GP zone or on the? 'Phase that increase the strength in the artificial aging or baking coating process are Mg / Si clusters as described above, . On the other hand, clusters which inhibit precipitation of the GP zone or β 'phase in the artificial aging treatment or the baking coating treatment are Si-rich clusters, which have been reported to be formed at room temperature (room temperature aging) after solution quenching For example, Sato: Light Metal vol.56, page 595).
However, in the general aluminum alloy manufacturing process, as described above, since it is usually left at room temperature for about one to four months until it is molded into a panel by a car maker after manufacturing the plate (left at room temperature) It is difficult to produce only Mg-Si clusters that promote BH properties, because Mg-Si clusters produced at the time of plate production and Si rich clusters generated at room temperature aging coexist.
Therefore, in order to improve the BH property, the inventors believe that it is important to control the ratio of Si-rich clusters adversely affecting BH properties and Mg-Si clusters promoting BH properties. And the cluster type for improving the BH property was revealed.
(Density of cluster)
In the present invention, clusters satisfying the defined clusters or prerequisites described above are included at an average number density of 1.0 x 10 24 / m 3 or more. If the average number density of the clusters is less than 1.0 x 10 24 pieces / m 3 , clusters that are too small in size at the time of room temperature decrease are formed, resulting in deterioration of BH property and deterioration of workability. On the other hand, although the upper limit of the average number density of the clusters is not particularly specified, from the viewpoint of the production limit, the average number density is about 25.0 x 10 23 / m 3 (about 2.5 x 10 24 / m 3 ).
When the average number density of the clusters defined in the present invention is small, it means that the formation amount of the clusters themselves becomes insufficient, and Mg and Si added (contained) are consumed in the clusters formed at the room temperature aging. Thus, even if there is an effect of promoting precipitation of the GP zone or β 'phase and improving the BH property, the improvement of the BH property remains at about 30 to 40 MPa with 0.2% proof strength after leaving at room temperature (room temperature aging). Therefore, under such conditions, a higher desired BH property can not be obtained.
(Specification of composition of the present invention cluster)
Even in a cluster satisfying the cluster or the precondition defined in the present invention, the influence on the BH property varies depending on the composition as described above. Clusters rich in Si atoms adversely affect the BH properties, but this is because Si-rich clusters are produced at the time of baking, and the difference between the Mg / Si composition and the strengthening phase such as β '' or β ' So that it does not promote the formation of the reinforcing phase at the time of baking, but rather suppresses the formation of the reinforcing phase.
On the other hand, clusters rich in Mg atoms improve the BH property, but Mg-rich clusters are produced at the time of baking coating and Mg / Si composition is relatively close to that of the strengthening phase such as β '' or β ' , Thereby promoting the formation of reinforcing phases in baking painting.
In the present invention, on the basis of the compositional relationship of these clusters, the ratio of clusters having a large number of atoms of Mg in the clusters is controlled to increase the BH property. Accordingly, in the present invention, it is preferable that at least 10 or more of the Mg atom and / or the Si atom are contained in total, and even if one of the Mg atom and the Si atom included in these atoms is used as a reference, The ratio of the atomic mass which is rich in Mg atoms having a Mg / Si ratio of 2/3 or more among the aggregates of atoms satisfying the condition that the distance between any atom adjacent to the atom and the adjacent atom is 0.75 nm or less is defined as 0.65 or more do. If the proportion of the atomic aggregates having a Mg / Si ratio of 2/3 or more is less than 0.65, the number of clusters rich in Si atoms increases, and the BH property tends to be small due to the above mechanism.
Here, the upper limit of the ratio of the atomic aggregates having a Mg / Si ratio of 2/3 or more is not particularly defined, but about 0.90 is the manufacturing limit.
(Measurement principle and measurement method of 3DAP)
3DAP (3D atom probe) is a FIM (Time-of-flight mass spectrometer) installed in a field ion microscope (FIM). With this arrangement, it is a local analysis apparatus capable of observing individual atoms of a metal surface by an electric field ion microscope and identifying these atoms by flight time mass spectrometry. In addition, since 3DAP can simultaneously analyze the type and position of atoms emitted from the sample, it is a very effective means for analyzing the structure of the aggregate of atoms. As a result, as described above, it is used for analyzing a structure of a magnetic recording film, an electronic device, or a steel material. In addition, recently, as described above, it is also used for discrimination of a cluster of a structure of an aluminum alloy plate.
In this 3DAP, the ionization phenomenon of a sample atom under a high electric field called electric field evaporation is utilized. When a high voltage is applied to a sample required for evaporation of the sample atomic electric field, atoms are ionized from the surface of the sample, and this exits the probe hole and reaches the detector.
This detector is a position sensitive detector that measures the time of flight up to the individual ion detectors together with the individual ion mass analysis (identification of atomic species) So that it can be decided. Therefore, the 3DAP can characterize the atomic structure of the tip of the sample three-dimensionally and can be observed because the atomic position and atomic species of the sample tip can be measured at the same time. Since the electric field evaporation occurs sequentially from the front end face of the sample, the depth direction distribution of atoms from the sample tip can be irradiated at the atomic level resolution.
Since the 3DAP uses a high electric field, a sample to be analyzed needs to have a high conductivity such as a metal. In addition, the shape of the sample is generally to be a fine needle shape having a tip diameter of about 100 nm or less There is a need. Therefore, a sample is taken from the central portion of the plate thickness of the aluminum alloy plate to be measured, and the sample is cut and electrolytically polished by a precision cutting device to prepare a sample having an ultrathin needle tip for analysis. As a measurement method, for example, "LEAP3000" manufactured by Imago Scientific Instruments is used, a high pulse voltage of 1 kV order is applied to an aluminum alloy plate sample whose tip is formed into a needle shape, and millions of atoms Is continuously ionized. The ion is detected by the position sensitive detector, and the pulse voltage is applied. From the flight time until each ion is ejected from the tip of the sample and reaches the detector, mass analysis of the ion ).
 Using the property that the electric field evaporation occurs regularly from the front end of the specimen in order, the coordinates in the depth direction are appropriately given to the two-dimensional map indicating the arrival position of the ions and the analysis software "IVAS" is used , And performs three-dimensional mapping (atomic structure in three dimensions: construction of atom map). Thereby, a three-dimensional atom map at the tip of the sample is obtained.
The cluster of atoms is analyzed by using the 3-D atom map and the Maximum Separation Method, which is a method of defining atoms belonging to a precipitate or a cluster. In this analysis, the number of Mg atoms and / or Si atoms (10 or more in total), the distances (intervals) between adjacent Mg atoms and Si atoms, and the specific narrow intervals (0.75 nm Or less) is given as a parameter.
It is to be noted that, even if one or both of the Mg atom and the Si atom are included in a total of 10 or more, and either of the Mg atom or the Si atom included in these atoms is used as a reference, Is 0.75 nm or less, and a cluster satisfying these conditions is defined as a cluster of atoms of the present invention. Moreover, by evaluating the atomic aggregate dispersion state suitable for the definition, an aggregate number density of the atoms, measured by sample number average three or more, is measured as per the average density of 1m 3 (pieces / m 3), and quantifying .
(Detection efficiency of atoms by 3DAP)
At present, the detection efficiency of atoms by these 3DAPs is limited to about 50% of the ionized atoms, and the remaining atoms can not be detected. If the detection efficiency of the atoms by this 3DAP greatly changes, such as improvement in the future, there is a possibility that the measurement result by 3DAP of the average number density (number / 탆 3 ) of clusters of each size specified by the present invention have. Therefore, in order to have reproducibility in this measurement, it is preferable that the detection efficiency of the atoms by 3DAP is made approximately constant at about 50%.
(Chemical composition)
Next, the chemical composition of the 6000-series aluminum alloy sheet will be described below. The 6000-series aluminum alloy plate to which the present invention is applied is required to have various properties such as excellent formability, BH property, strength, weldability, corrosion resistance, etc.
In order to satisfy such a demand, it is assumed that the composition of the aluminum alloy plate contains 0.2 to 2.0% of Mg and 0.3 to 2.0% of Si in terms of% by mass, and the remaining amount includes Al and inevitable impurities. In addition, the percentages of the content of each element are all expressed in% by mass.
It is preferable that the 6000-series aluminum alloy plate to which the present invention is applied is an excess Si-type 6000-series aluminum alloy plate having a better BH property and a Si / Mg mass ratio (Si / Mg) of 1 or more. The 6000-series aluminum alloy sheet secures formability by lowering the stress at the time of press forming or bending, and is hardened by aging due to heating during artificial aging such as coating baking of the panel after molding to improve the strength And has excellent age hardenability (BH property) which can secure necessary strength. Among them, the excess Si-type 6000-series aluminum alloy plate is superior to the 6000-series aluminum alloy plate in which the mass ratio (Si / Mg) is less than 1, and this BH property is more excellent.
In the present invention, these other elements other than Mg and Si are basically impurities or elements which may be contained, and they are the content (permissible amount) of each element level according to the AA to JIS standards and the like.
Namely, from the viewpoint of resource recycling, in the present invention, as a raw material for dissolution of an alloy, a 6000-series alloy containing a large amount of other elements other than Mg and Si as an additive element (alloying element) Alloy scrap material, low-purity aluminum and the like are used in large quantities, the following other elements are inevitably incorporated in the raw mass. In addition, the refining itself which reduces these elements drastically increases the cost, and it is necessary to allow the inclusion to some extent. In addition, even if it contains a real mass, there is a content range which does not impair the purpose and effect of the present invention.
Therefore, in the present invention, the following elements are allowed (regulated) to be contained within the upper limit amount in accordance with the AA to JIS standards specified below. Concretely, the content of Mn is not more than 1.0% (but does not include 0%), preferably not more than 0.8%, Cu: not more than 1.0% (but not including 0%), preferably not more than 0.8% Fe: not more than 1.0% (but not including 0%), preferably not more than 0.5%, Cr: not more than 0.3% (but not including 0%), preferably not more than 0.1% (But not including 0%), preferably not more than 0.1%, V: not more than 0.3% (but not including 0%), preferably not more than 0.1%, Ti: not more than 0.1% Preferably not more than 0.05%, more preferably not more than 0.03%, Zn: not more than 1.0% (but not including 0%), preferably not more than 0.5%, and Ag: not more than 0.2% (But not including 0%), preferably not more than 0.1%, in addition to the basic composition described above in this range. The content range of each element in the 6000-series aluminum alloy, or the tolerable amount thereof will be described below.
Si: 0.3 to 2.0%
Si, together with Mg, is an important element of the cluster formation defined in the present invention. Further, it is an essential element for achieving aging hardenability by forming an aged precipitate which contributes to strength improvement during artificial aging such as solid solution strengthening and paint baking treatment, and to obtain the strength (proof strength) required for an outer panel of an automobile . In addition, in the 6000 series aluminum alloy sheet of the present invention, it is the most important element to combine various properties such as total elongation which affects the press formability.
Further, in order to exhibit excellent age hardening ability in the coating baking treatment after molding on the panel, it is necessary to set the Si / Mg ratio to 1.0 or more in terms of the mass ratio, Based aluminum alloy composition.
If the Si content is too small, the absolute amount of Si is insufficient, so that it is not possible to form only water densities defining the above-described clusters defined in the present invention, and the coating baking hardenability is remarkably lowered. Furthermore, it can not combine various properties such as total elongation required for each application. On the other hand, when the Si content is too large, coarse crystals and precipitates are formed, and the bending workability, the total elongation, and the like remarkably decrease. In addition, the weldability is remarkably hindered. Therefore, Si is set in the range of 0.3 to 2.0%, preferably in the range of 0.5% to 1.5%, more preferably in the range of 0.6% to 1.2%.
Mg: 0.2 to 2.0%
Mg, together with Si, are important elements of the cluster formation specified in the present invention. It is an indispensable element for forming an aged precipitate that contributes to the improvement of strength together with Si during artificial aging treatment such as solid solution strengthening and paint baking treatment to exhibit an age hardening ability and to obtain a required strength as a panel.
If the Mg content is too small, the absolute amount of Mg is insufficient, so that it is not possible to form only water densities defining the clusters specified in the present invention, and the coating baking hardenability is markedly reduced. As a result, the required strength as a panel can not be obtained. On the other hand, if the Mg content is too large, coarse crystals and precipitates are formed, and the bending workability, the total elongation, and the like remarkably decrease. Therefore, the Mg content is in the range of 0.2 to 2.0%, preferably 0.3 to 1.0%, more preferably 0.3 to 0.7%. It is also preferable that Si / Mg is in an amount such that Si / Mg is 1.0 or more in a mass ratio.
(Manufacturing method)
Next, a method of producing the aluminum alloy sheet of the present invention will be described below. The aluminum alloy sheet of the present invention is a conventional method or a known method. The aluminum alloy ingot having the composition of the 6000 series composition is subjected to homogenization heat treatment after casting, and subjected to hot rolling and cold rolling to become a predetermined thickness , And also a crude treatment such as solvent quenching is performed.
However, in order to control the clusters of the present invention in order to improve the BH property in these production steps, the solution-cooling and quenching process and the proper quenching (cooling) quenching temperature and the maintenance in the temperature range are more appropriate It needs to be controlled. In other processes, there are also preferable conditions for controlling the clusters within the scope of the present invention.
(Melting, casting cooling rate)
First, in the melting and casting steps, the molten aluminum alloy which is dissolved and adjusted within the composition range of the above 6000 system component is appropriately selected and cast by a conventional melt casting method such as a continuous casting method or a semi-continuous casting method (DC casting method). Here, in order to control the clusters within the specified range of the present invention, it is preferable that the average cooling rate at the time of casting is as large as possible (as fast as possible) from the liquidus temperature to the solidus temperature of 30 DEG C / min or more.
If the temperature (cooling rate) control in the high temperature region at the time of casting is not carried out, the cooling rate in this high temperature region is inevitably slowed down. When the average cooling rate in the high temperature region is slowed as described above, the amount of the crystals to be produced in a large temperature range in the high temperature region becomes large, and the size and the amount of deviation of the crystals in the plate width direction and thickness direction It grows. As a result, there is a high possibility that the regulated cluster can not be controlled within the scope of the present invention.
(Homogenization heat treatment)
Subsequently, the cast aluminum alloy ingot is subjected to homogenization heat treatment prior to hot rolling. This homogenization heat treatment (cracking treatment) is intended to homogenize the structure, that is, to eliminate segregation in crystal grains in the ingot texture. The condition for achieving this object is not particularly limited, and may be a normal one-time or one-step processing.
The homogenization heat treatment temperature is suitably selected from the range of 500 DEG C or higher and lower than the melting point, and the homogenization time is 4 hours or longer. If the homogenization temperature is low, segregation in the crystal grains can not be sufficiently eliminated and this acts as a starting point of fracture, so that elongation flangeability and bending workability are deteriorated. Thereafter, even if the hot rolling is immediately started or the hot rolling is started after cooling to an appropriate temperature, the number of clusters defined in the present invention can be controlled.
After the homogenization heat treatment is performed, the temperature between 300 ° C and 500 ° C is cooled to room temperature at an average cooling rate of 20-100 ° C / h, followed by cooling to 350 ° C to 450 ° C at an average heating rate of 20-100 ° C / Reheating, and hot rolling may be started in this temperature range.
If the conditions of the average cooling rate after the homogenization heat treatment and the reheating rate thereafter are exceeded, there is a high possibility that a coarse Mg-Si compound is formed.
(Hot rolling)
Hot rolling consists of rough rolling (ingot rolling) and finish rolling in accordance with the sheet thickness to be rolled. In these rough rolling and finishing rolling processes, a rolling machine such as a reverse type or tandem type is suitably used.
At this time, under the condition that the hot rolling (rough rolling) start temperature exceeds the solidus temperature, burning occurs, so that hot rolling itself becomes difficult. If the hot rolling start temperature is less than 350 占 폚, the load during hot rolling becomes too high, and hot rolling itself becomes difficult. Therefore, the hot-rolling start temperature is in the range of 350 占 폚 to the solidus line temperature, more preferably 400 占 폚 to the solidus line temperature.
(Annealing of hot rolled sheet)
The annealing (coarse annealing) before cold rolling of the hot-rolled sheet is not necessarily required, but may be actually carried out in order to further improve properties such as formability in accordance with miniaturization of crystal grains and optimization of aggregate structure.
(Cold rolling)
In the cold rolling, the hot-rolled sheet is rolled and formed into a cold-rolled sheet (including a coil) having a desired final sheet thickness. However, in order to make the crystal grains finer, the cold rolling rate is preferably 60% or more, and intermediate annealing may be performed between the cold rolling passes for the same purpose as the coarse annealing.
(Solubilization and quenching treatment)
After cold rolling, a solution quenching treatment is carried out. Solution treatment The quenching treatment is not particularly limited, as long as it is heating and cooling by a usual continuous heat treatment line. However, in order to obtain a sufficiently high capacity of each element and as described above, it is preferable that the crystal grains be finer, and the crystal grains are heated at a heating rate of 5 deg. C / sec or more at a solution treatment temperature of 520 deg. To 10 seconds.
From the viewpoint of suppressing the formation of coarse grain boundary compounds that decrease the formability and the hempability, it is preferable that the average cooling rate from the solution temperature to the quenching stop temperature is 3 DEG C / s or more. If the cooling rate of the solution is small, coarse Mg 2 Si and single Si are produced during cooling, and the formability is deteriorated. Further, the amount of the solution after the solution is lowered, and the BH property is lowered. In order to secure the cooling rate, the quenching process is performed by selecting and using water cooling means such as air cooling, mist, spray, immersion, etc. of a fan or the like.
(Processing with a deformation amount of 0.1 to 5%)
Here, in order to further improve the BH property, it is preferable to perform the processing of 0.1 to 5% in deformation amount from the completion of the solution treatment and the quenching treatment to the reheating treatment to be described later. The means is appropriately selected by leveler correction, skin pass rolling and the like. By performing the processing of 0.1 to 5% in deformation amount from the termination of the solution treatment and the quenching treatment to the reheating treatment, clusters rich in Mg atoms are formed in the cluster of atoms satisfying the above-mentioned prescribed conditions, So that the ratio of the atomic aggregates having a Mg / Si ratio of 2/3 or more can be easily set to 0.65 or more. On the other hand, if the amount of deformation is larger than 5%, the hem forming ability tends to deteriorate. Although this mechanism is still unclear, it is presumed as follows. That is, by performing the processing of 0.1 to 5% in deformation amount on the plate after the solution treatment, the frozen voids of the plate subjected to the solution treatment are reduced, and as a result, diffusion at room temperature is suppressed. This makes it difficult to produce Si-rich clusters generated at room temperature, and makes it possible to make the ratio of the atomic aggregates having a Mg / Si ratio of 2/3 or more to 0.65 or more.
(Maintained at room temperature)
In order to further increase the BH property, it is preferable that the room temperature holding time from the completion of the solution treatment and the quenching treatment to the start of the reheating treatment including the processing step of 0.1 to 5% Do. By shortening the room temperature holding time, the ratio of the atomic aggregates having a Mg / Si ratio of 2/3 or more is likely to become 0.65 or more. The room temperature holding time is preferably as short as possible, and the solution treatment, quenching treatment and reheating treatment may be continuous so that there is little time difference, and the time of the lower limit is not particularly set.
(Reheating treatment)
It is preferable that the reaching temperature of the reheating treatment is in a temperature range of 80 to 160 占 폚 and the holding time is in a range of 3 to 24 hours. If the reaching temperature of the reheating is 80 DEG C or less or less than 3 hours, Mg-Si clusters promoting the BH property are not sufficiently generated, and as a result, the ratio of clusters having a Mg / Si ratio of 2/3 or more tends to be less than 0.65. On the other hand, under conditions where the reheating temperature reaches 160 DEG C or the holding time exceeds 24 hours, some intermetallic compound phases such as beta '' and beta 'are formed differently from the clusters, It's easy, the BH castle gets too low. In addition, due to β '' and β ', the moldability tends to deteriorate.
The cooling to the room temperature after the reheating treatment may be forced quenching using cooling means at the time of quenching for efficient production even in the air cooling. Namely, since uniform or similar clusters having the same size as defined in the present invention are produced by the temperature holding treatment, forced quenching such as the conventional reheating treatment and control of the complicated average cooling rate over various stages are unnecessary.
Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is of course not limited by the following Examples, but it is also possible to carry out the present invention by appropriately modifying it within the range satisfying the purpose of the description before and after , All of which are included in the technical scope of the present invention.
(Example)
Next, an embodiment of the present invention will be described. The 6000-series aluminum alloy plate having different composition or cluster conditions specified in the present invention is subjected to a skin pass rolling process until the time from the completion of the solution treatment and the quenching treatment to the start of the reheating treatment and from the completion of the solution treatment and quenching treatment to the start of the reheating treatment And the processing rate of each of them. Then, the BH properties (coating baking hardenability) after holding for 100 days at room temperature in each of these examples were evaluated. In addition, the hem forming property as the bending workability was also evaluated.
In the display of the content of each element in Table 1 showing the composition of the 6000-series aluminum alloy plate of each example, the indication in which the value in each element is a blank indicates that the content thereof is below the detection limit.
Specific manufacturing conditions of the aluminum alloy plate were as follows. Aluminum alloy ingots of the respective compositions shown in Table 1 were commonly dissolved by the DC casting method. At this time, in all of the examples, the average cooling rate during casting was set at 50 ° C / minute from the liquidus temperature to the solidus temperature. Subsequently, the ingot was subjected to a crack treatment at 540 DEG C for 4 hours in all the examples in common, and hot rolling was started. In all of the examples, hot rolled sheets were hot rolled to a thickness of 3.5 mm in the subsequent finish rolling. The aluminum alloy sheet after hot rolling was subjected to coarse annealing at 500 DEG C for 1 minute in all of the examples, followed by cold rolling at a machining ratio of 70% without intermediate annealing during the cold rolling pass. In all the examples, 1.0 mm cold rolled sheet.
These cold-rolled sheets were subjected to a solution treatment at 550 ° C in a quartz stone furnace in common to each of the examples, retained for 10 seconds after reaching the target temperature, and quenched by water cooling. After the quenching treatment was completed, skin pass rolling with a deformation amount of 0 to 5% shown in Table 2 was immediately applied to the rolling mill and maintained at room temperature until the start of the reheating treatment for the time shown in Table 2. Thereafter, the annealing furnace was used to carry out the reheating treatment at the temperature and the holding condition shown in Table 2, and held for a predetermined time, followed by water cooling.
After these tempering treatments, a blank (blank) was cut out from each final product plate after being left at room temperature for 100 days, and the properties of each blank were measured and evaluated. In addition, tissue observation using 3DAP was performed only for the sample after 100 days from the tempering treatment. The results are shown in Table 3.
(cluster)
First, the structure at the center of the thickness of the plate was analyzed by the above-mentioned 3DAP method, and the average number density (× 10 23 pieces / m 3 ) of clusters defined in the present invention, the ratio of the number of Mg atoms to the number of Si atoms Mg / Si) of not less than 2/3 were respectively obtained by the above-mentioned methods. The results are shown in Table 3.
In Table 3, the cluster conditions of the present invention described above include at least 10 or more of Mg atoms and / or Si atoms in total, and are simply described as "at least 10 atoms of Mg and Si" have. It is to be noted that even if any one of the Mg atom and the Si atom contained in these atoms is used as a reference, the distance between any atom of the reference atom and another atom adjacent to the atom is 0.75 nm or less, nm or less ".
(Coating baking hardenability)
The 0.2% proof stress (As proof strength) was determined by a tensile test as the mechanical properties of each of the release boards after the tempering treatment and left at room temperature for 100 days. Each of these publicly known plates was subjected to artificial aging and curing treatment at 185 ° C for 20 minutes after aging at room temperature for 100 days in common. The 0.2% proof stress (post-BH) of the release plate after (BH) Tensile test. Then, the BH property of each of the noticed plates was evaluated from the difference between the 0.2% proof stresses (increase in proof stress).
In the tensile test, a No. 5 test piece (25 mm x 50 mm GL x plate thickness) of JISZ2201 was taken from each of the above disclosed boards and subjected to a tensile test 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 set to 5 mm / min to 0.2% proof stress and to 20 mm / min after proof stress. The number of N of the mechanical property measurement was 5, and the average value was calculated. In the test piece for measuring the strength after BH, 2% preliminary deformation simulating the press forming of the plate was applied to the test piece by the tensile tester, and then the BH treatment was performed.
(Hem-forming property)
The hempability was measured for each of the publicly known plates after the tempering treatment and after being left for 100 days. In the test, a rectangular test piece having a width of 30 mm was used, and a 90-degree bend of internal bending (R) of 1.0 mm was carried out by a down flange. Then, a 1.0 mm thick inner part was inserted and the bending part was further inwardly Preheme processing for bending, 180 degree bending, and flat hem processing for bringing the end portion into close contact with the inner portion was performed.
Surface conditions such as surface roughness, minute cracking, and occurrence of large cracks were visually observed at the bend (bent portion) of the flat hems and visually evaluated under the following criteria.
0; Cracks, no surface roughness, 1; Surface hardness, 2; Deep surface blend, 3; Minute surface cracks, 4; Continuous surface cracks in a line, 5; Fracture
As shown in the alloy numbers 0 to 9 in Table 1 and the numbers (0, 1, 7, 13, 19 to 24) in Table 2, each embodiment is within the composition range of the present invention, Manufacturing, and tempering processes. As a result, each of these inventive examples satisfies the cluster condition defined in the present invention, as shown in Table 2. That is, the ratio of the number of Mg atoms to the number of Si atoms (in the aggregate of atoms satisfying these conditions and the average number density of the aggregates of atoms satisfying the predetermined conditions in the present invention is 1.0 × 10 24 / m 3 or more) Mg / Si) of 2/3 or more is 0.65 or more. As a result, as shown in Table 3, each example of the invention is excellent in BH property even after room temperature aging after the tempering treatment. Further, even after room temperature aging after the tempering treatment, the hem-forming property is excellent.
In Comparative Examples 2, 8 and 14 of Table 2, Inventive Alloys Examples 1, 2 and 3 of Table 1 are used. However, in each of these Comparative Examples, as shown in Table 2, the time taken from the completion of the solution treatment and the quenching treatment to the start of the reheating treatment is too long. As a result, as shown in Table 3, the average number density (x 10 23 pieces / m 3 ) of the clusters defined in the present invention satisfies the requirement, but the ratio of the number of Mg atoms to the number of Si atoms (Mg / Si) / 3 or more is too small and the change with time in the room temperature is large compared with Examples 1, 2 and 3, which are the same alloy composition, and the BH property deteriorates.
In Comparative Examples 3, 9 and 15 of Table 2, Inventive Alloys Examples 1, 2 and 3 of Table 1 are used. However, as shown in Table 2, these comparative examples are manufactured under preferable manufacturing conditions except for skin pass rolling after solution quenching treatment. For this reason, the average number density (x 10 23 pieces / m 3 ) of the clusters defined in the present invention satisfies the requirement. However, since skin pass rolling is not performed, as shown in Table 3, among the aggregates of atoms satisfying these conditions, an atom aggregate (Mg / Si) having a ratio of the number of Mg atoms to the number of Si atoms (Mg / Si) And the BH property deteriorates due to the large change in the room temperature over time as compared with Examples 1, 2 and 3 which are the same alloy compositions.
Comparative Examples 4 to 6, 10 to 12, and 16 to 18 in Table 2 use inventive alloys Examples 1, 2, and 3 shown in Table 1. However, in each of these comparative examples, as shown in Table 2, the conditions for the reheating treatment are out of a preferable range. As a result, it was found that the average number density of the atomic aggregates or the average ratio of the atomic aggregates having the ratio of the number of Mg atoms to the number of Si atoms (Mg / Si) of 2/3 or more was too small, The BH property and the heme processability are lowered.
In Comparative Examples 25 to 32 shown in Table 2, alloys Nos. 10 to 17 shown in Table 1 are used, and Mg or Si of the essential elements are contained in the present invention Out of range, or the amount of impurity element is too much. As a result, as shown in Table 3, these comparative examples have lower BH properties and heme processability than those of the respective examples.
Comparative Example 25 is the alloy 10 of Table 1, and Si is too small.
Comparative Example 26 is the alloy 11 of Table 1, and Si is too much.
Comparative Example 27 is the alloy 12 of Table 1, and Fe is too much.
Comparative Example 28 is the alloy 13 of Table 1, and Mn is too much.
Comparative Example 29 is the alloy 14 of Table 1, and Cr is too much.
Comparative Example 30 is the alloy 15 shown in Table 1, and Cu is too much.
Comparative Example 31 is the alloy 16 of Table 1, and Zn is too much.
Comparative Example 32 is the alloy 17 of Table 1, and Zr and V are too much.
From the results of the above examples, it is confirmed that the BH property improvement after room temperature aging needs to satisfy all the conditions of the clusters defined in the present invention. Further, the critical significance or effect of each component requirement or preferable production conditions in the present invention for obtaining such cluster conditions and BH properties is also supported.
Figure 112015025127951-pct00001
Figure 112015025127951-pct00002
Figure 112015025127951-pct00003
INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a 6000-series aluminum alloy plate having BH properties and moldability after room temperature aging. As a result, it is possible to expand the application of 6000-series aluminum alloy plates to transportation devices such as automobiles, ships or vehicles, home appliances, structures and structures, and particularly to members of transportation vehicles such as automobiles.

Claims (2)

  1. Mg-Si based aluminum alloy plate containing 0.2 to 2.0% of Mg and 0.3 to 2.0% of Si and the balance of Al and inevitable impurities in terms of mass% Or more of the Mg atom and the Si atom as the aggregate of at least one of the Mg atom and the Si atom contained in the aggregate, the distance of each other of any atom of Mg atoms or Si atoms adjacent to the atoms and the average number density of the aggregate, the atomic satisfying 0.75nm or less at 1.0 × 10 24 gae / m 3 or higher is also the condition, Wherein an average ratio of aggregates of atoms having a ratio (Mg / Si) of Mg atoms to Si atoms of 2/3 or more in an aggregate of satisfying atoms is 0.65 or more.
  2. The method according to claim 1,
    Wherein the aluminum alloy sheet further contains not more than 1.0% of Mn (not including 0%), not more than 1.0% of Cu (but not including 0%), not more than 1.0% of Fe (Not including 0%), Zr: not more than 0.3% (but not including 0%), V: not more than 0.3% (but not including 0% Ti: not more than 0.1% (but not including 0%), Zn: not more than 1.0% (but not including 0%), Ag: not more than 0.2% (but not including 0% Wherein the aluminum alloy plate has excellent baking painting hardenability.
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CN104641012B (en) 2016-10-19
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