CN103305728B - Aluminum alloy sheet excellent in baking finish hardenability - Google Patents

Aluminum alloy sheet excellent in baking finish hardenability Download PDF

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CN103305728B
CN103305728B CN201310073511.1A CN201310073511A CN103305728B CN 103305728 B CN103305728 B CN 103305728B CN 201310073511 A CN201310073511 A CN 201310073511A CN 103305728 B CN103305728 B CN 103305728B
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atom
cluster
temperature
aggregate
diameter
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CN103305728A (en
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宍户久郎
松本克史
有贺康博
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Kobe Steel Ltd
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Kobe Steel Ltd
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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
    • C22C21/06Alloys 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
    • 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
    • C22C2200/00Crystalline structure

Abstract

The present invention provides a 6000 series aluminum alloy sheet with both BH property and formability after long-term room temperature aging. The 6000 series aluminum alloy sheet comprises specific clusters with a number density within a certain range and having large effects on the BH property. The clusters are measured by a three dimensional atom probe ion microscope, and the average radius of the diameter of equivalent circle of the clusters is within a certain range. The BH property after long-term room temperature aging can be further improved by reducing the standard deviation of the radius of the diameter of equivalent circle.

Description

The aluminium alloy plate of coating baking hardening excellence
Technical field
The present invention relates to Al-Mg-Si-type aluminum alloy plate.The said aluminium alloy plate of the present invention is the milled sheet of hot-rolled sheet and cold-reduced sheet etc., refers to modified, the coating baking hardening aluminium alloy plate before treatment that implement solution treatment and quench treatment etc.In addition, in following description, also aluminium is called Al.
Background technology
In recent years, from the consideration of love global environment etc., the light-weighted social desirability of the vehicles such as automobile improves day by day.In order to reply this requirement, car panel, particularly as the large-scale body panel (exterior panel of hood, car door, roof etc., inner panel) material, except the ferrous materials of steel plate etc., plasticity and coating baking hardening excellence, more the application of the aluminium alloy material of light weight also increase.
Wherein, in the panel of the exterior panel (outside plate) and inner panel (inner panel) etc. of the panel structure of the hood, mud guard, car door, roof, luggage-boot lid etc. of automobile, as thin-walled and high-strength aluminium alloy plate, the use of AA to JIS6000 system (following, being all the only called 6000 is) aluminium alloy plate of Al-Mg-Si system is studied.
This 6000 line aluminium alloy plate, must contain Si, Mg, particularly 6000 line aluminium alloys of superfluous Si type, has the composition that this Si/Mg is more than 1 by quality ratio, and has excellent age hardening capability.For this reason, it is (following that it has coating baking hardening, all be called bake hardening=BH, baking hardenability), namely, when stamping and bending machining, plasticity can be guaranteed due to low-yield, and heating when being processed by the artificial aging (sclerosis) that low temperature is compared in the coating baking process etc. of counter plate after being shaped and carry out age hardening, yield strength improves, and can guarantee the intensity as panel necessity.
In addition, 6000 line aluminium alloy plates, measure with Mg and wait compared with 5000 other line aluminium alloys that alloy amount is many etc., alloying element amount is fewer.Therefore, when being recycled as aluminum alloy melting material (melt raw material) by the waste material of these 6000 line aluminium alloy plates, easily obtain 6000 original line aluminium alloy ingot bars, recirculation is also excellent.
On the other hand, the exterior panel of automobile as everyone knows, is for aluminium alloy plate, compound carry out stamping in stretch forming time and bending forming etc. formed machining and make.Such as, in the large-scale exterior panel of hood and car door etc., by stretch etc. stamping, become the molding shape as exterior panel, then, by crimping (hemming) processing of the flat flanging of this exterior panel periphery etc., carry out the joint with inner panel, become panel structure.
At this, 6000 line aluminium alloys, have and possess the such advantage of excellent BH, and the problem that another side exists is that it has room-temperature aging, after solution hardening process, age hardening is there is under the room temperature of several months keeps, intensity increases, and causes the plasticity of panel thus, and particularly bendability reduces.Such as; when 6000 line aluminium alloy plates are used for car panel purposes; (manufacture rear) from aluminium manufacturer after solution hardening process; until be formed in automobile factory be processed into panel; usually (room temperature placement) about 1 ~ 4 month can be placed at room temperature; therebetween, age hardening (room-temperature aging) is carried out largely.Particularly in the exterior panel entering strict bending machining, even if can be no problem through a postforming in month after manufacturing, but through three months, also have crimping and add the problem to crack man-hour etc.Therefore, car panel use, particularly in 6000 line aluminium alloy plates of exterior panel, needs the room-temperature aging in the suppression leap of about 1 ~ 4 month long period.
In addition, when such room-temperature aging is large, the problem that also can produce is, BH reduces, compared heating during artificial aging (sclerosis) process of low temperature by the coating baking process etc. of counter plate after described shaping, until as the necessary intensity of panel, yield strength all can not improve.
Therefore, all the time, about the raising of the BH of 6000 line aluminium alloys and the suppression of room-temperature aging, propose there is various motion.Such as, proposing in patent documentation 1, when solid solution and quench treatment, by making speed of cooling periodically change, to suppress under room temperature after fabrication after 7 days to the Strength Changes after 90 days.In addition, propose in patent documentation 2, after solid solution and quench treatment, within 60 minutes, remain on the temperature 10 ~ 300 minutes of 50 ~ 150 DEG C, obtain BH and shape freezing thus.In addition, propose in patent documentation 3, when solid solution and quench treatment, regulation first paragraph cooling temperature and speed of cooling thereafter, thus obtain BH and shape freezing.
In addition, propose in patent documentation 4, by the thermal treatment after solution hardening, BH is improved.Propose in patent documentation 5, improve BH by the endothermic peak regulation of DSC (Differential scanning calorimetry, differential scanning calorimetry) method.In patent documentation 6, same proposition improves BH by the heating peak value regulation of DSC.
But this patent documentation 1 ~ 6, for the cluster (aggregate of atom) of the BH and room-temperature aging that directly affect 6000 line aluminium alloy plates, is only indirectly analogize its movement eventually.
In contrast, in patent documentation 7, having attempted direct measurement affects the BH of 6000 line aluminium alloy plates and the cluster (aggregate of atom) of room-temperature aging and is specified.Namely, when analyzing organizing of 6000 line aluminium alloy plates with the transmission electron microscopes of 1,000,000 times, the average number density being the cluster of the scope of 1 ~ 5nm by equivalent diameter within viewed cluster (aggregate of atom) is defined in 4000 ~ 30000/μm 2scope, thus make BH excellent, suppress room-temperature aging.
[look-ahead technique document]
[patent documentation]
[patent documentation 1] JP 2000-160310 publication
[patent documentation 2] patent No. 3207413 publication
[patent documentation 3] patent No. 2614686 publication
[patent documentation 4] Unexamined Patent 4-210456 publication
[patent documentation 5] Unexamined Patent 10-219382 publication
[patent documentation 6] JP 2005-139537 publication
[patent documentation 7] JP 2009-242904 publication
Summary of the invention
But, in these prior aries, particularly about the suppression of room temperature rheological parameters' change with time, also have room for improvement.That is, in the car coating baking processing of these prior aries, after the coating baking of 170 DEG C × 20 minutes, the BH after long room-temperature aging counts about 60 ~ 70MPa with 0.2% yield strength, after long-time, still require higher BH.
In view of such problem, the object of the invention is to, a kind of Al-Si-Mg line aluminium alloy plate is provided, even the car coating baking processing after long room-temperature aging, also can give play to high BH and good processibility.
In order to reach this purpose, the main idea of the aluminium alloy plate of coating baking hardening excellence of the present invention is that one is in mass % containing Mg:0.2 ~ 2.0%, Si:0.3 ~ 2.0%, surplus forms Al-Mg-Si-type aluminum alloy plate by Al and inevitable impurity, wherein, as the aggregate of the atom measured by three-dimensional atom probe field-ion microscope, the aggregate of this atom contains Mg atom or Si atom any one or two kinds and adds up to more than 10, no matter with which atom of the Mg atom contained by it or Si atom for benchmark, distance each other as any one atom among the atom of this benchmark and other adjacent atom is below 0.75nm, with 6.0 × 10 23individual/m 3above, 25.0 × 10 23individual/m 3following average number density contains the aggregate of the atom meeting these conditions, and the mean radius meeting the diameter of equivalent circle of the aggregate of the atom of these conditions is more than 1.2nm, below 1.5nm, further, the standard deviation of the radius of this diameter of equivalent circle is below 0.35nm.
Find in the present invention, among the aggregate (cluster) of the atom measured by 3DAP, as as described in regulation, add up to containing specific above Mg atom or Si atom, between adjacent atom contained by it, distance is each other the average number density of specific following so specific cluster, closely related with BH.
And moreover, the present invention also finds, the distribution meeting the size of the aggregate of the described specific atom of these conditions is also very important, and the standard deviation of the mean radius of diameter of equivalent circle and the radius of this diameter of equivalent circle produces great effect to BH.Namely found out that, in order to improve BH, the mean radius of the diameter of equivalent circle of the aggregate of described specific atom is more than 1.2nm, below the 1.5nm of specific scope, and standard deviation is little, is below 0.35nm, and this is required for BH improves.It according to the present invention, a kind of Al-Si-Mg line aluminium alloy plate can be provided, even if, when the long-time room-temperature aging of 100 days, also can give play to higher BH.
Accompanying drawing explanation
Fig. 1 is the explanatory view of the radius of the diameter of equivalent circle of the cluster representing aluminium alloy plate and the relation of number density.
Embodiment
Below, for embodiments of the present invention, important document is illustrated particularly one by one.
Cluster (aggregate of atom):
First, illustrate that in the present invention, what meaning is said cluster be.Said cluster in the present invention, refer to the aggregate (cluster) of the aftermentioned atom measured by 3DAP, in following description, main manifestations is cluster.In 6000 line aluminium alloys, after solid solution and quench treatment, to keep or in the thermal treatment of 50 ~ 150 DEG C, known Mg, Si form the aggregate being called as the atom of cluster in room temperature.But in the cluster that this room temperature keeps and generates in the thermal treatment of 50 ~ 150 DEG C, its movement (character) is difference completely.
Keep formed cluster by room temperature, in artificial aging thereafter or coating baking process, suppress the precipitation of GP district or the β ' phase making intensity increase.On the other hand, the cluster (or Mg/Si cluster) formed at 50 ~ 150 DEG C, shows on the contrary, promotes the precipitation (such as, hillside plot etc.: describe in light metal vol.51, the 215th page) of GP district or β ' phase.
In addition, in described patent documentation 7, describe about paragraph 0021 ~ 0025, these clusters are analyzed by specific heat measurement and 3DAP (three-dimensional atom probe) etc. now.But also describe, meanwhile, in the analysis of the cluster from 3DAP, by observing, even if the existence of cluster itself is confirmed, the size of the described cluster specified in the present invention and number density are still failed to understand or can only be measured with limitation.
Really, in 6000 line aluminium alloys, all attempt analyzing described cluster by 3DAP (three-dimensional atom probe) all the time.But as described in aforementioned patent literature 7, even if the existence of cluster itself is proved, the size of this cluster and number density are also unclear.This is because, among the aggregate of the atom measured by 3DAP (cluster), which cluster is failed to understand with the closely related degree of BH, and the aggregate being largely related to the atom of BH is which is also failed to understand.
In contrast, the present inventors, in No. 2011-56960, the patent application that the present inventors had previously applied for, the closely-related cluster with BH is made clear.Namely find, among the cluster measured by 3DAP, as described in regulation, add up to containing specific above Mg atom or Si atom, this distance each other containing adjacent atom of its institute is that specific so specific cluster below and BH are closely related.And find, by increasing the number density meeting the aggregate of the atom of these conditions, even if carry out the car coating baking processing of the condition of short period of time after room-temperature aging with low temperature, also can give play to high BH.
Specifically, No. 2011-56960, described patent application, as the aluminium alloy plate application one of coating baking hardening excellence in mass % containing Mg:0.2 ~ 2.0%, Si:0.3 ~ 2.0%, surplus forms Al-Mg-Si-type aluminum alloy plate by Al and inevitable impurity, wherein, as the aggregate of the atom measured by three-dimensional atom probe field-ion microscope, the aggregate of this atom contains Mg atom or Si atom any one or two kinds, add up to more than 30, no matter with which atom of the Mg atom contained by it or Si atom for benchmark, arbitrary atom among other the atom adjacent with the atom as this benchmark, its distance is each other below 0.75nm, with 1.0 × 10 5individual/μm 3above average number density, containing the aggregate of atom meeting these conditions.
According to No. 2011-56960, this patent application, any one or two kinds containing Mg atom or Si atom, add up to more than 30, the distance between atom adjacent one another are is that the existence of the cluster of below 0.75nm makes BH.And, make these clusters exist a certain amount of more than, even if for the Al-Si-Mg line aluminium alloy plate of room-temperature aging, with the low temperature of 150 DEG C × 20 minutes, when carrying out the car coating baking processing of short period of time, also can send out and make it to have given play to higher BH.
In contrast, found that of studying further of the present inventors, among the cluster measured by 3DAP, described cluster is existed in a large number, although can positively make BH improve, not much else, improve effect also insufficient.In other words, finding exactly described cluster is existed in a large number, although be the precondition (prerequisite) that BH improves, may not be sufficient condition.
Therefore, the present inventors, have applied for again No. 2011-199769, patent application (Heisei application on September 13rd, 23).That is, with 6.0 × 10 23individual/m 3above average number density, containing the aggregate of atom meeting described specific condition, as prerequisite, by meet the atom of these conditions aggregate among, the radius of maximum diameter of equivalent circle is limited in 10.0 × 10 lower than the average number density of the aggregate of the atom of 1.5nm size 23individual/m 3below, on the other hand, the radius of the diameter of equivalent circle making this maximum is lower than the average number density a of the aggregate of the atom of 1.5nm size, the ratio a/b being the average number density b of the aggregate of the atom of more than 1.5nm size with the radius of maximum diameter of equivalent circle is less than 3.5, and the radius in this way containing described maximum diameter of equivalent circle is the aggregate of the atom of more than 1.5nm size.
Why obtaining this discovery, is due in the cluster of any one or two kinds containing Mg atom or Si atom, its size (size) variant (distribution) certainly, and finds that the effect of the size of cluster to BH has a great difference.That is, the effect of size to BH of cluster has diametical difference, and the cluster of namely smaller size hinders BH, and on the other hand, the cluster of larger size promotes BH.Based on this, among described specific cluster, if reduce the cluster of smaller size, increase the cluster of larger size, then BH performance improves enough further.
The cluster of smaller size, although (when artificial age-hardening processes) disappears when BH process, when BH, hinders the precipitation to the high large cluster of strength-enhancing effect on the contrary, infers and BH is reduced.On the other hand, the cluster of larger size, grows when BH process, and the precipitation of precipitate during promotion BH process, infers and improve BH.
But find according to research thereafter further, excessive cluster, if grow when BH process, then size will become excessive, make BH reduce on the contrary, and BH intensity before treatment becomes too high, processibility deterioration.Namely also find, in order to not make processibility deterioration improve BH, have the cluster of best size to exist.The present invention also finds, although the distribution of the size of the aggregate of described specific atom is important, but these are as the mean radius of the diameter of equivalent circle of the mean sizes of the aggregate of described specific atom, and the standard deviation of the radius of this diameter of equivalent circle produces great effect to BH.Namely find, in order to improve BH, the mean radius of the diameter of equivalent circle of the aggregate of described specific atom is more than 1.2nm, below the 1.5nm of specific scope, and the standard deviation of the radius of this diameter of equivalent circle is little, for below 0.35nm, this is required for BH improves.
That is, in order to improve BH, the size existence on a large scale from small to large of the aggregate of described specific atom, its distribution of sizes does not have huge deviation, only has the cluster of best size to generate better.The mean radius of the so-called diameter of equivalent circle specified in the present invention is more than 1.2nm, below 1.5nm, and the standard deviation of the radius of this diameter of equivalent circle is below 0.35nm just means this.Thus, in the present invention, even if when car coating baking processing keeps 100 days for a long time with room temperature, the BH of Al-Mg-Si-type aluminum alloy plate also can be made to improve further.
(cluster regulation of the present invention)
Below, the regulation for cluster of the present invention is described particularly.
The present invention specifies the aluminium alloy plate of cluster, as aforementioned, be after rolling, implement solid solution and quench treatment, reheat process etc. a series of modified after plate, can be described as the plate before being processed into panel that is shaped by stamping grade.In order to suppress stamping before the room temperature of leap about 0.5 ~ 4 month longer-term place time room-temperature aging, certainly, before needing that this room temperature is placed, implement described modified after the structural state of plate become tissue given to this invention.
(definition of cluster of the present invention)
So, utilize three-dimensional atom probe field-ion microscope measure room temperature place before, implement described solid solution and quench treatment etc. modified after the tissue of arbitrary thickness of slab central part of Al-Mg-Si-type aluminum alloy plate.As the cluster be present in this measured tissue, in the present invention, first, this cluster contains any one or two kinds of Mg atom or Si atom, adds up to more than 10.Further, the Mg atom contained by the aggregate of this atom and the number of Si atom The more the better, its upper limit does not have special stipulation, if but from manufacturing limit, then the upper limit of the Mg atom contained by this cluster and the number of Si atom is probably about 10000.
In No. 2011-56960, described patent application, any one or two kinds that this cluster contains Mg atom or Si atom add up to more than 30.But the present invention is as aforementioned, because the cluster of smaller size hinders BH, so limited it and make it to reduce.Therefore, in order to the cluster of smaller size should carrying out this restriction controls in measurable scope, any one or two kinds of regulation containing Mg atom or Si atom add up to more than 10.
In the present invention, same with No. 2011-56960, described patent application, in addition, no matter with which atom of the Mg atom contained by these clusters or Si atom for benchmark, arbitrary atom among other the atom adjacent with the atom as this benchmark, its distance is each other below 0.75nm, it can be used as the aggregate (cluster) of (meeting regulation of the present invention) given to this invention atom.This distance 0.75nm each other, close in order to ensure Mg and Si interatomic distance each other, BH is had to improve the number density of large-sized cluster of effect and the numerical value that specifies under between the low-temperature short-time after long-term room-temperature aging, otherwise, being to limit undersized cluster, number density being controlled less and the numerical value of regulation.The present inventors, have studied up to now so that the relation of the aluminium alloy plate of high BH and the aggregate of atomic level also can be played in the car coating baking processing under the condition changed between low-temperature short-time in detail, consequently find through experiment, the number density of the atom set body of above-mentioned definition defined is large, is the tissue morphology playing high BH.Therefore, the meaning of the technology of interatomic distance 0.75nm is not fully aware of, but for the number density that tightly ensures the atom set body playing high BH, is the numerical value determined for this reason.
The cluster specified in the present invention, although the situation containing Mg atom and Si atom two side is maximum, to comprise containing Mg atom but not containing the situation of Si atom, and containing Si atom but not containing the situation of Mg atom.In addition, be not defined as only by Mg atom and Si atomic building, in addition, also contain Al atom with very high probability.
In addition, the one-tenth according to aluminium alloy plate is grouped into, and the atom of Fe, Mn, Cu, Cr, Zr, V, Ti, Zn or Ag etc. of containing as alloying element and impurity is included in cluster, certainly leads to when these other atom is added up being analyzed by 3DAP.But, even if these other atom (alloying element and impurity origin) is included in cluster, if compare with the sum of Mg atom with Si atom, be then still in low-level.Therefore, such situation containing other atom in cluster, meets described regulation (condition), also as cluster of the present invention, and only in the same manner as the cluster of Mg atom and Si atomic building, plays function.Therefore, the cluster specified in the present invention, as long as meet described regulation, in addition can containing which type of atom.
In addition, what is called of the present invention " with which atom of the Mg atom contained by it or Si atom for benchmark; any one atom among other the atom adjacent with the atom as this benchmark; its distance is each other below 0.75mm ", be meant to the whole Mg atoms and the Si atom that are present in cluster, at least there is Mg atom and Si atom that a distance is each other below 0.75nm around it.
In cluster of the present invention, being defined as of distance between atom, no matter with which atom of the Mg atom contained by it or Si atom for benchmark, the distance of atoms whole among other the atom adjacent with the atom as this benchmark also not exclusively can be in below 0.75nm separately, on the contrary, also all below 0.75nm can be in separately.In other words, also distance can be had adjacent with Si atom more than other Mg atoms of 0.75nm, around specific (as benchmark) Mg atom or Si atom, meet other the Mg atom of this predetermined distance (interval) or Si atom is minimum one.
Then, meet other the adjacent Mg atom of this predetermined distance or Si atom when having one, meet the condition of distance, the Mg atom that should add up or the quantity of Si atom, comprise specific (as benchmark) Mg atom or Si atom and become two.In addition, meet other the adjacent Mg atom of this predetermined distance or Si atom when having two, meet the condition of distance, the Mg atom that should add up or the quantity of Si atom, comprise specific (as benchmark) Mg atom or Si atom and become three.
Cluster described above is aforementioned, and details are in described later, modified after rolling in addition, keeps process and make it the cluster that generates by the temperature after the quenching under solid solution and high temperature stops.Namely, cluster of the present invention, keep process by the temperature after quenching under solid solution and high temperature stops and making it the aggregate of the atom generated, any one or two kinds containing Mg atom or Si atom, add up to more than 10, no matter with which atom of the Mg atom contained by it or Si atom for benchmark, any one atom among other the atom adjacent with the atom as this benchmark, its distance is each other the cluster of below 0.75nm.
Up to now provided information is, in artificial aging or coating baking process, promoting the cluster of the precipitation of GP district or the β ' phase making intensity increase, is Mg/Si cluster as aforementioned, and this cluster is formed through the thermal treatment of 50 ~ 150 DEG C after solid solution and quench treatment.Relative to this, in artificial aging process or coating baking process, the cluster suppressing the precipitation of GP district or β ' phase is rich Si cluster, this cluster keeps (room-temperature aging) through room temperature and is formed (such as after solution hardening, in: describe in light metal vol.56, the 595th page).
But, when the present inventors analyze artificial aging process in detail or coating baking process time intensity and the relation of cluster, it found that, when contributing to artificial aging process or coating baking process time the organizational factor of intensity, be not the kind (composition) of cluster, but through the modifier treatment of plate and the distribution of the size of the cluster generated.In addition, the distribution of the size of this cluster, after also analyzing with aforesaid definition, with during artificial aging process or coating baking thermal treatment time corresponding the becoming of intensity make clear.
Relative to this, the cluster formed under described room temperature keeps (room-temperature aging), in the measurement undertaken by three-dimensional atom probe field-ion microscope, even the aggregate of atom, still there is the number of atom outside the described regulation of the present invention of disengaging and the number density of cluster.Therefore, the regulation of cluster of the present invention (atom set body), distinguish to some extent with the cluster keeping (room-temperature aging) to be formed in described room temperature, and be also prevent in this cluster, the regulation that (containing) Mg and Si of interpolation is consumed.
(density of cluster)
The cluster that the present invention of meeting described above defines to the cluster of precondition, with 6.0 × 10 23individual/m 3above, 25.0 × 10 23individual/m 3following average number density contains.If the average number density of this cluster compares 6.0 × 10 23individual/m 3very few, then long-standing room temperature through time in can regenerate too small cluster, cause the reduction of BH and the deterioration of processibility.On the other hand, if compare 25.0 × 10 23individual/m 3and too much, then BH intensity before treatment becomes too high, consequently processibility deterioration.
If the average number density of the cluster that the present invention defines is few, then mean that the formation volume of this cluster itself is insufficient, in the cluster formed through described room-temperature aging, the major part of (containing) Mg and Si of interpolation is consumed.Therefore, even if promote the precipitation of GP district or β ' phase, the effect improving BH such as has, and after placing (room-temperature aging) through long-term room temperature, the raising of BH also can rest on existing about 30 ~ 40MPa in 0.2% yield strength.Therefore, in such a situa-tion, the BH of higher expectation can not be obtained.
(the distribution of sizes regulation of cluster of the present invention)
The cluster defined to make the present invention exists described a certain amount of (more than average number density), BH is improved as prerequisite, the present invention meet the aggregate of the atom of these conditions, the mean radius of diameter of equivalent circle is more than 1.2nm, below 1.5nm, and the standard deviation of the radius of this diameter of equivalent circle is below 0.35nm.
The mean radius E (r) of the diameter of equivalent circle of the aggregate of atom:
The mean radius E (r) (nm) meeting the diameter of equivalent circle of the aggregate of the atom of described precondition is represented by E (r)=(1/n) ∑ r.At this, n is the number of the aggregate of the atom meeting described precondition.R is the radius (nm) of the diameter of equivalent circle of the aggregate of each atom meeting described precondition.
The size itself meeting the aggregate of the atom of described precondition is first very important to raising BH.The aggregate (cluster) of the atom that the mean radius E (r) of described diameter of equivalent circle is too small, when BH process, (when artificial age-hardening processes) disappears, when this BH, inhibition strength improves the high β of effect " or the precipitation of intermediate precipitate that β ' waits, hinder BH.On the other hand, the aggregate (cluster) of the atom that the mean radius E (r) of diameter of equivalent circle is excessive, also can before BH process when (eve or in advance), under room-temperature aging, become β " or the intermediate precipitate that waits of β ' and separating out; make the intensity before BH too high on the contrary, hinder press formability and bendability.In addition, if the intermediate precipitate that the moment before BH process has become β " or the intermediate precipitate that waits of β ' and separating out, then, when BH, can suppress new β " or β ' waits is separated out, or BH is hindered.In addition, described β ", β ' is all middle precipitated phases, they be all Mg2Si, but crystal structure (arrangement mode of atom) is different.Be difficult to difference performance so just, when therefore " ' " can not use, β ' is called that symbol (prime) is divided at β angle, β " is called β rad symbol (dubble prime).
Relative to this, meet the aggregate of the atom of described precondition, its size counts the scope of more than 1.2nm, below 1.5nm with the mean radius E (r) of diameter of equivalent circle, when this BH, become (contribute to intensity improve) β that strength-enhancing effect is high " or the intermediate precipitate that waits of β ' and separating out.Therefore, it is possible to have stamping low with stage strength that is bending machining, processibility is good, and after BH, intensity starts the characteristic uprised.Therefore, the size of the aggregate of the atom of described regulation, counts more than 1.2nm, below 1.5nm with the mean radius E (r) of diameter of equivalent circle.
The standard deviation of the diameter of equivalent circle of the aggregate of atom:
In addition, meet the standard deviation of the diameter of equivalent circle of the aggregate of the atom of described precondition, according to the mean radius E (r) of described diameter of equivalent circle, by σ 2=(1/n) ∑ [r-E (r)] 2represent.
Meet the size of the aggregate of the atom of described precondition, namely the mean radius E (r) of diameter of equivalent circle is also very important, but meet the standard deviation of the mean radius E (r) of mean sizes, the i.e. diameter of equivalent circle of the aggregate of the specific atom of described precondition, as the distribution of the size of the aggregate of atom, also there is great effect to BH.Namely, in order to improve BH, the mean radius of the diameter of equivalent circle of the aggregate of described specific atom is more than 1.2nm, below the 1.5nm of specific scope, and the standard deviation of the radius of this diameter of equivalent circle is little, for below 0.35nm, this is required for BH improves.
That is, in order to improve BH, the size of the aggregate of described specific atom, does not have large deviation from small to large, only has the cluster of best size to generate better.The mean radius of described diameter of equivalent circle is more than 1.2nm, below 1.5nm, and the standard deviation of the radius of this diameter of equivalent circle is below 0.35nm is exactly this meaning.Thus, in the present invention, even if car coating baking processing is when carrying out after long room temperature keeps, the BH of Al-Mg-Si-type aluminum alloy plate also can be made to improve further.
In the present invention, by the mean radius of the diameter of equivalent circle of the aggregate of the atom of described regulation this two side of standard deviation with the radius of this diameter of equivalent circle, specify the distribution of sizes of the aggregate of the atom of described regulation, the quantity of the aggregate (cluster) of the atom that the size among the aggregate increasing the atom of described regulation is similar or ratio.Thus, even if car coating baking processing is when carrying out after long room temperature keeps, the BH of Al-Mg-Si-type aluminum alloy plate also can be made to improve further.
Even the cluster of described regulation, if hinder the cluster that the size of BH is little many, then among described regulation, the mean radius of diameter of equivalent circle also can diminish and lower than 1.2nm.In addition, the standard deviation of the radius of diameter of equivalent circle becomes large and more than 0.35nm.
On the other hand, even the cluster specified in the present invention, hinder the cluster that the size of BH is large many, among described regulation, the mean radius of diameter of equivalent circle also can become large and more than 1.5nm.In addition, the standard deviation of the radius of diameter of equivalent circle also becomes large and more than 0.35nm.
The aggregate (cluster) of the atom that the mean radius of diameter of equivalent circle is too small, when BH process, (when artificial age-hardening processes) disappears, when this BH, inhibition strength improves high (the contribute to intensity improve) β of effect " or the precipitation of intermediate precipitate that β ' waits, hinder BH.On the other hand, the aggregate (cluster) of the atom that the mean radius of diameter of equivalent circle is excessive, also can before BH process when, under room-temperature aging, become β " or the intermediate precipitate that waits of β ' and separating out, make the intensity before BH too high, hinder bendability.In addition, if the intermediate precipitate that the moment before BH process has become β " or the intermediate precipitate that waits of β ' is separated out, then, when BH, will suppress new β " or β ' waits is separated out, still BH is hindered.
(measuring principle of 3DAP and measuring method)
3DAP (three-dimensional atom probe) is on field-ion microscope (FIM), installs time-of-flight type mass analyzer.It is a kind of by such structure, can observation each atom of metallic surface, according to time of flight mass analysis, identify the local analysis device of these atoms with field-ion microscope.In addition, 3DAP can analyze kind and the position of the atom launched from test portion simultaneously, is therefore very effective means in the tectonic analysis of the aggregate of atom.Therefore, as known technology, as aforementioned, be used to the fabric analysis etc. of magnetic recording film and electron device or steel.In addition, recently, as described in, be also used to the differentiation etc. of the cluster of the tissue of aluminium alloy plate.
In this 3DAP, utilization is called as the ionization phenomenon of the test portion atom under the high electric field of field evaporation itself.For the additional high-voltage carrying out field evaporation for test portion atom of test portion, atom is ionized from test portion surface, and it arrives detector by inspecting hole.
This detector is position sensing type detector, according to the mass analysis (qualification as the element of atomic species) of each ion, and arriving the flight time of detector by measuring each ion, this position detected (atomic structre position) can be determined simultaneously.Therefore, 3DAP can measure position and the atomic species of the atom of test portion front end simultaneously, therefore has the speciality of the atomic structre of test portion front end being carried out three-dimensional reconstruction, observation.In addition, because field evaporation occurs successively from the front end face of test portion, so can distribute with the depth direction of the resolution of atomic level investigation from the atom of test portion front end.
Because this 3DAP utilizes high electric field, so the test portion analyzed needs the electroconductibility of metal etc. high, and in general the shape of test portion, needs for point diameter is 100nm about φ or following superfine needle-like.Therefore, extract test portion from the thickness of slab central part etc. of the aluminium alloy plate as measuring object, cut and this test portion of electrolytic polishing with precision cutting device, make the test portion with the superfine needle-like leading section analyzed.As measuring method, it such as uses " LEAP3000 " of Imago Scientific Instruments society, for the aluminium alloy plate test portion making its front end be configured as needle-like, the high pulse voltage of additional 1kV level, makes the atom ionization constantly of millions of from test portion front end.Ion is detected by position sensing type detector, and applying pulse voltage, after each ion of test portion front end flies out, according to the flight time reaching detector, carries out the mass analysis (qualification as the element of atomic species) of ion.
In addition, utilize the character that field evaporation occurs successively regularly from the front end face of test portion, two-dimensional map for the arrival place representing ion is suitable for the coordinate giving depth direction, use analysis software " IVAS ", carry out three-dimensional mapping (three-dimensional atomic structre: constructing of atom map).Thereby, it is possible to obtain the Three-dimensional atom map of test portion front end.
For this Three-dimensional atom map, re-use method, i.e. Maximum Separation Method (maximum separation method) that definition belongs to the atom of precipitate and cluster, carry out the analysis of the aggregate (cluster) of atom.When carrying out this analysis, the quantity (adding up to more than 10) of any one or two kinds of Mg atom or Si atom is provided, and the distance (interval) between Mg atom adjacent one another are or Si atom, and the quantity of the Mg atom or Si atom with described specific narrow intervals (below 0.75nm) is as parameter.
Then, any one or two kinds containing Mg atom or Si atom add up to more than 10, using any one atom of the Mg atom contained by it or Si atom as benchmark, any one atom among other the atom adjacent with the atom as this benchmark, its distance is each other below 0.75nm, the cluster meeting these conditions is defined as the aggregate of atom of the present invention.Then, evaluate the dispersion state meeting the aggregate of the atom of this definition, measuring test portion quantity is more than three, makes the number density equalization of the aggregate of atom, as every 1m 3mean density (individual/m 3) carry out measurement and quantification.
That is, utilize the intrinsic analysis software that described 3DAP originally has, according to following formula 1, try to achieve when the aggregate of the described atom as measuring object is considered as ball, its maximum turning radius l g.
[formula 1]
l g = Σ i = 1 n [ ( x i - x ‾ ) 2 + ( y i - y ‾ ) 2 + ( z i - z ‾ ) 2 ] n
In this formula 1, l git is the turning radius automatically calculated by the intrinsic software of three-dimensional atom probe field-ion microscope.X, y, z is x, y, z axle constant in the measurement layout of three-dimensional atom probe field-ion microscope.Xi, yi, zi are under the length of this x, y, z axle, form the volume coordinate of Mg, Si atom of the aggregate of described atom.Complete with " mean value symbol (the x bar) " of "-" etc. respectively on " x " " y " " z ", be also the length of this x, y, z axle, but be the center-of-mass coordinate of the aggregate of described atom.N is the quantity of Mg, Si atom of the aggregate forming described atom.
Then, according to following formula 2, r g=√ (5/3) l grelation, by this turning radius l gbe converted into Gu Nie (Guinier) radius r g.
[formula 2]
r G = 5 3 · l g
By ancient Nie's radius r of this conversion gbe considered as the radius of the aggregate of atom, calculate each maximum diameter of equivalent circle r of the aggregate of the described atom as measuring object.In addition, the number n meeting the aggregate of the atom of described precondition is also calculated.In addition, the average number density (individual/m of the aggregate of the atom meeting described precondition can also be calculated according to number n 3).
The measurement of these clusters of being undertaken by 3DAP, for implemented described modified after the position of arbitrary thickness of slab central part of Al-Mg-Si-type aluminum alloy plate carry out 10 places, make each observed value (calculated value) equalization described in these, as each average value specified in the present invention.
Then, according to the maximum diameter of equivalent circle r of this calculating and the number n of aggregate of atom meeting described precondition, by the formula of aforementioned E (r)=(1/n) ∑ r, try to achieve the mean radius E (r) (nm) of the diameter of equivalent circle of the aggregate of described atom.
In addition, by the mean radius E (r) of described diameter of equivalent circle, according to aforementioned σ 2=(1/n) ∑ [r-E (r)] 2formula, try to achieve the standard deviation of the diameter of equivalent circle of the aggregate of the atom meeting described precondition.
Further, the calculating formula of the radius of the aggregate of described atom, from turning radius l gto ancient Nie's radius r gmeasurement and conversion method, quote M.K.Miller:Atom Probe Tomography, (Kluwer Academic/Plenum Publishers, New York, 2000), 184 pages.Subsidiary one, the calculating formula of the radius of the aggregate of atom, in addition, also describes in a lot of documents.Such as in 140 pages " (2) three-dimensional atom probe analyses " of the microstructure of the low alloy steel of ion exposure " change " (a rattan well gram man of virtue and ability, good fortune paddy plough the loyal Wins of department, greatly Kubo, precious wild and rich etc.), just comprise description have described formula 1 and Gu Nie radius r G conversion formula (but turning radius l gmark describe as rG).
(detection efficiency from the atom of 3DAP)
From the detection efficiency of the atom of these 3DAP, at present, among Ionized atom about 50% is the limit, and remaining atom can not detect.The detection efficiency of the atom of this 3DAP, waits if improve in the future and significantly changes, then exist the cluster of each size of the present invention's regulation mean number density (individual/μm 3) the possibility of 3DAP measuring result change.Therefore, in order to make this measurement keep reproducibility, the detection efficiency of the atom of preferred 3DAP is roughly fixed as about 50%.
(chemical composition composition)
Then, below the chemical composition composition of 6000 line aluminium alloy plates is described.The present invention, as 6000 line aluminium alloy plates of object, as the plate etc. of the outside plate of described automobile, requires excellent plasticity and BH, intensity, welding property, all characteristics of erosion resistance etc.
In order to meet such requirement, the composition of aluminium alloy plate is in mass % containing Mg:0.2 ~ 2.0%, Si:0.3 ~ 2.0%, and surplus is made up of Al and inevitable impurity.Further, the % of the content of each element represents it is all the meaning of quality %.
The present invention as 6000 line aluminium alloy plates of object, be preferably BH more excellent, the mass ratio Si/Mg of Si and Mg is 6000 line aluminium alloy plates of more than 1 such superfluous Si type.6000 line aluminium alloy plates have excellent age hardening capability (BH), namely, it utilizes low-yield when stamping and bending machining and guarantees plasticity, and heating when comparing the artificial aging process of low temperature by the coating baking process etc. of panel after being shaped and carry out age hardening, thus yield strength improves, the intensity needed can be guaranteed.Wherein, 6000 line aluminium alloy plates of superfluous Si type, with mass ratio Si/Mg lower than 1 6000 line aluminium alloy plates compared with, this BH is more excellent.
In the present invention, the element that other the element except this Mg, Si is substantially impurity or also can contains is the content (allowance) of each element level along AA to JIS specification etc.
Namely, from the view point of resource recirculation, in the present invention, as the melt raw material of alloy, not only use high purity Al ingot, and a large amount of use using the element of other beyond Mg, Si contain in a large number as Addition ofelements (alloying element) 6000 be alloy and other aluminium alloy scraps, low-purity Al block etc. time, following other element certainty ground is like this mixed into real mass.And this refining initiatively reducing these elements itself brings cost increase, thus needs permission to contain.In addition, real mass contains, also have do not damage the object of the invention and effect containing scope.
Therefore, in the present invention, allow to contain in the scope of so following element respectively below the upper limit amount of AA to the JIS specification along following provisions etc.Specifically, in this scope, except above-mentioned essentially consist, also can also contain below Mn:1.0% (but, not containing 0%), below Cu:1.0% (but, not containing 0%), below Fe:1.0% (but, not containing 0%), below Cr:0.3% (but, not containing 0%), below Zr:0.3% (but, not containing 0%), below V:0.3% (but, not containing 0%), below Ti:0.05% (but, not containing 0%), below Zn:1.0% (but, not containing 0%), below Ag:0.2% (but, not containing 0%) one or more.Below, illustrate each element in above-mentioned 6000 line aluminium alloys containing scope and meaning or allowance.
Si:0.3~2.0%
Si and Mg is all the important elements of the described cluster of formation specified in the present invention.In addition, during artificial aging process under the described low temperature of solution strengthening and coating baking process etc., be formed with the precipitation helping intensity and improve, being for playing age hardening capability, obtaining the necessary element as the intensity (yield strength) required for the exterior panel of automobile.In addition, in the present invention 6000 line aluminium alloy plate, it still makes it the most important element of all characteristics possessed the breaking elongation that press formability has an impact etc.
In addition, after plate forms over there, with more low temperature, through the short period of time coating baking process and given play to excellent age hardening capability, preferably Si/Mg is made to be more than 1.0 by quality ratio, compare general said superfluous Si type, the 6000 line aluminium alloys compositions further superfluously relative to Mg containing Si.
If Si content is very few, then the absolute magnitude of Si is not enough, and therefore only can not form described cluster given to this invention with the number density of regulation, coating baking hardening significantly reduces.In addition, all characteristics of the breaking elongation required by each purposes etc. can not be had both.On the other hand, if Si content is too much, then form thick crystallisate and precipitate, bendability and breaking elongation etc. significantly reduce.In addition, weldability is also significantly impaired.Therefore, Si is the scope of 0.3 ~ 2.0%.
Mg:0.2~2.0%
Mg is also the important element being the described cluster of formation given to this invention together with Si.In addition, when the described artificial aging process of solution strengthening and coating baking process etc., being formed with the precipitation helping intensity and improve together with Si, is for playing age hardening capability, obtains the necessary element as yield strength needed for panel.
If Mg content is very few, then the absolute magnitude of Mg is not enough, and therefore only can not form described cluster given to this invention with the number density of regulation, coating baking hardening significantly reduces.Therefore can not get as the yield strength required for panel.On the other hand, if Mg content is too much, then thick crystallisate and precipitate are formed, and bendability and breaking elongation etc. significantly reduce.Therefore, the content of Mg is the scope of 0.2 ~ 2.0%, and Si/Mg is the amount of more than 1.0 by quality ratio.
(manufacture method)
Then, below the manufacture method of aluminium alloy plate of the present invention is described.Aluminium alloy plate of the present invention, manufacturing process itself is ordinary method or known method, it manufactures is carry out homogenizing thermal treatment for the aluminium alloy ingot bar of above-mentioned 6000 set members compositions after casting, implements hot rolling, cold rolling and become set thickness of slab, then implements the modifier treatment of solution hardening etc.
But, in these manufacturing processes, in order to make BH improve, in order to control cluster of the present invention, as aftermentioned, needing to control solid solution and quench treatment and suitable quenching (cooling) more rightly and stopping temperature, and the maintenance in this temperature range.In addition, in other operation, also have for described cluster is controlled the preferred condition in specialized range of the present invention.
(fusing, casting cooling speed)
First, in fusing, casting process, be suitable for the common melt-casting method selecting Continuous casting process, semicontinuous casting method (DC casting) etc., the casting fusing aluminium alloy adjusted in above-mentioned 6000 set member compositing ranges melts soup.At this, in order to cluster be controlled in specialized range of the present invention, in the average cooling rate when casting, preferably making liquidus temperature to solidus temperature large as far as possible (soon), is more than 30 DEG C/minute.
When temperature (speed of cooling) under high-temperature area when casting like this controls, the speed of cooling of this high-temperature area is inevitable slack-off.So when the average cooling rate of high-temperature area is slow, in the temperature range of this high-temperature area, the quantitative change of the crystallisate of thick generation is many, and the size of the plate width direction of ingot bar, the crystallisate of thickness direction and the deviation of amount also become large.Consequently, described regulation cluster can not be controlled to uprise in the possibility of scope of the present invention.
(homogenize thermal treatment)
Next, for the aluminium alloy ingot bar of described casting, before hot rolling, implement to homogenize thermal treatment.This thermal treatment that homogenizes (equal thermal treatment) its object is to homogenizing of tissue, that is, eliminate the segregation in the crystal grain in ingot bar tissue.As long as reach the condition of this object, be not particularly limited, once common or one section process can be carried out.
The thermal treatment temp that homogenizes is lower than fusing point more than 500 DEG C, and the time that homogenizes is selected from the scope of more than 4 hours is suitable.If this homogenization temperature is low, then fully can not eliminate the segregation in crystal grain, it works as the starting point destroyed, and therefore stretch flangeability and bendability reduce.Afterwards, start hot rolling immediately or start hot rolling after the cooling of suitable temperature keeps, also can control the number density into cluster given to this invention.
After carrying out this thermal treatment that homogenizes, between 300 DEG C ~ 500 DEG C, be cooled to room temperature with the average cooling rate of 20 ~ 100 DEG C/h, then reheat to 350 DEG C ~ 450 DEG C with the average heating rate of 20 ~ 100 DEG C/h, also can start hot rolling at this temperature field.
If the condition of the average cooling rate departed from after this thermal treatment that homogenizes and the speed that reheats thereafter, then the possibility of thick Mg-Si compound formation uprises.
(hot rolling)
Hot rolling, according to the thickness of slab of rolling, is made up of the roughing operation of ingot bar (slab) and finishing rolling step.In this roughing operation and finishing rolling step, be suitable for the milling train using reversible or tandem etc.
At this moment, start under temperature exceedes the condition of solidus temperature, because there is scaling loss, so hot rolling itself is difficult in hot rolling (roughing).In addition, when hot rolling starts temperature lower than 350 DEG C, load during hot rolling is too high, hot rolling difficulty itself.Therefore, it is 350 DEG C ~ solidus temperature that hot rolling starts temperature, is more preferably the scope of 400 DEG C ~ solidus temperature.
(annealing of hot-rolled sheet)
Although this hot-rolled sheet not necessarily needs the annealing (black annealing) before cold rolling, in order to make the characteristic of plasticity etc. improve further by the miniaturization of crystal grain and the optimization of set tissue, also can implement.
(cold rolling)
In cold rolling, the above-mentioned hot-rolled sheet of rolling, is made into the cold-reduced sheet (also comprising coiled material) of the final thickness of slab of expectation.But in order to make crystal grain more miniaturization, preferred cold rolling rate is more than 60%, in addition for the object same with described black annealing, also process annealing can be carried out between cold rolling mill train.
(solid solution and quench treatment)
After cold rolling, carry out solution hardening process.In solution treatment quench treatment, can be undertaken heating, cooling by common continuous heat-treatment lines, be not particularly limited.But, from expecting to obtain the sufficient solid solution capacity of each element, and make that crystal grain is finer to set out as aforementioned, preferably carry out with following condition, that is, be heated to more than 520 DEG C, solid solution temperature below melt temperature with the rate of heating of more than 5 DEG C/sec, and keep 0 ~ 10 second.
In addition, from the view point of the thick crystal boundary compound formation suppressing to make plasticity and crimping processibility reduce, preferably from solid solubility temperature to the average cooling rate of quench stop temperature be 3 DEG C/more than s.If the speed of cooling of solid solution is little, then thick Mg2Si and monomer Si is had to generate in cooling, plasticity deterioration.Solid solution capacity in addition after solid solution reduces, and BH reduces.
In order to ensure this speed of cooling, the air cooling of quench treatment difference choice for use fan etc., the magnetism servo-electric motor water-cooling of spraying, water spray, impregnating and condition.
(temperature after quenching stopping keeps process)
This quench treatment, be not by solution treatment after plate be cooled to room temperature, but temperature field T stopping cooling (quenching) of 80 ~ 130 DEG C is reached at plate, certain hour tr is only kept to keep process in this temperature range, no matter let cool thereafter or force the cooling body of cooling etc. and be cooled to room temperature.Maintenance (process) at this temperature of 80 ~ 130 DEG C, by heating, also can pass through non-heated, can be that isothermal keeps, also can have thermograde.But the relation of the hold-time t at this temperature and described quench stop temperature T, determines in the mode meeting following formula.
2.3×10 4×exp[-0.093×T]<t<2.0×10 5×exp[-0.096×T]
In the present invention, just for obtain the distribution of sizes of the set cluster of regulation, the stop condition of this quench treatment, stop the relation of temperature, hold-times etc. to carry out probe about various quenching.It found that, the distribution of sizes of the cluster during the temperature after quenching stops keeps, is subject to the diffusion length tremendous influence of Mg and Si, according to analytical results, preferably makes the diffusion length of Mg and Si 1.8 × 10 -9m ~ 4.8 × 10 -9the scope of m.
The diffusion length of this Mg and Si, is represented by following formula 3.In this formula, D 0being the spread coefficient represented by formula 4, is 6.2 × 10 -6(m 2/ s).Q is the activation energy of diffusion, is 11500 (J/mol).R is gas law constant, is 8.314.
The quench stop temperature and the temperature hold-time after stopping that quenching that are reused for the scope of the preferred diffusion length obtaining this Mg and Si arrange, according to the relation with quench stop temperature T, determine higher limit and the lower value of the temperature hold-time t after quenching stopping in the mode of described formula.
[formula 3]
D 0 exp [ - Q RT ] t
[formula 4]
J mol · K
Keep process by the cooling stopping under the high temperature of the comparison of this quench treatment and temperature, the distribution of sizes of the set cluster specified in the present invention can be obtained.In addition, also 6.0 × 10 can be obtained 23individual/m 3above, 25.0 × 10 23individual/m 3the average number density of the aggregate of following atom given to this invention.This is because, cooling stopping under the ratio higher temperatures of this quench treatment and temperature keep in the operation of process, the major part of the aggregate of the atom specified in the present invention, its size is formed impartial or similar.
Namely, any one or two kinds containing Mg atom or Si atom add up to more than 10, no matter with which atom of the Mg atom contained by it or Si atom for benchmark, any one atom among other the atom adjacent with the atom as this benchmark, its distance is each other the interior major part of the aggregate of the atom of below 0.75nm, and the cooling stopping under the ratio higher temperatures of this quench treatment and temperature keep being formed in the operation of process.Simultaneously, because keep the most size of the aggregate of the atom all formed in process impartial or similar in this temperature, so have the isotropism of the size of satisfied following condition, namely, the mean radius of diameter of equivalent circle is more than 1.2nm, below 1.5nm, and the standard deviation of the radius of this diameter of equivalent circle is below 0.35nm.
Thus, through keeping the plate of process than the cooling stopping under higher temperatures and temperature in this quench treatment, after this temperature keeps process, the little alumina cluster formed because of room-temperature aging at room temperature, room-temperature aging also tails off.Therefore, comprise bendability, press formability improves, even if after keeping between at room temperature long-term, by the heating during artificial aging process of 170 DEG C × 20 minutes such as the coating baking process of panel afterwards, still there is before and after BH the BH of the excellence that 0.2% yield strength difference is more than 90MPa.
To reheat after first for common plate quench cooled to room temperature and keep reheat in process, size given to this invention also forms impartial or similar cluster certainly, but keep processing the formation number brought with the cooling stopping under the ratio higher temperatures of described quench treatment and temperature to compare, the quantity formed is few utterly.
Even if this is because, shorten some terminate from quench cooled after to reheat process room temperature keep (placements) time, therebetween also can cluster major part formation.And its distribution of sizes of this cluster to vary etc. various, and size is unequal, there is deviation.
Therefore, even if the size specified in the present invention is impartial or similar cluster is formed, its absolute number is also few, the mean radius that can not meet the diameter of equivalent circle of the aggregate of atom is more than 1.2nm, below 1.5nm, and the standard deviation of the radius of its diameter of equivalent circle is in the regulation of below 0.35nm.Consequently, the processibility particularly after long-term room-temperature aging reduces, and can not have the poor BH such for more than 90MPa of 0.2% yield strength before and after BH in addition.
(temperature cools after keeping process)
To the cooling of room temperature after described temperature maintenance process, can let cool, and the efficient activity in order to produce, cooling body during aforementioned quenching also can be used to carry out pressure chilling.That is, occurring completely to make the impartial or similar cluster of the size that specifies in the present invention keep process by described temperature, not needing the existing such pressure chilling of process that reheats, and relate to the control of average cooling rate of complexity of several sections.
Below, enumerate embodiment and further illustrate the present invention, but the present invention does not limit by following embodiment certainly, also suitably can be changed enforcement in the scope stating aim before and after can be applicable to, these all quote in the scope of technology of the present invention.
[embodiment]
Following explanation embodiments of the invention.When solid solution and quench treatment, by the maintenance process stopped than the quenching under higher temperatures and at this temperature, manufacture respectively for 6000 different line aluminium alloy plates of the cluster condition specified in the present invention, evaluate respectively and at room temperature keep after 7 days and keep the BH (coating baking hardening) after 100 days.Meanwhile, also press formability and the crimping processibility as bendability is evaluated.
The cluster condition that so-called described the present invention specifies is the standard deviation of the average number density of the aggregate of atom, the mean radius of diameter of equivalent circle, the radius of this diameter of equivalent circle.And, the aggregate of this atom so-called, the aggregate of the atom of satisfied following condition: any one or two kinds containing Mg atom or Si atom add up to more than 10, no matter with which atom of the Mg atom contained by it or Si atom for benchmark, any one atom among other the atom adjacent with the atom as this benchmark, its distance is each other all below 0.75nm.
In addition, describedly to make respectively, as shown in table 2, be after making solid solution and quench treatment reheat treatment condition, Heating temperature (DEG C, describe in table 2 as arriving temperature), there is various change, thus manufacture 6000 line aluminium alloy plates of the composition shown in table 1 in hold-time (h) and the cooling conditions after particularly making this heating keep.Further, in the expression of the content of each element in Table 1, the numerical value of each element shows as blank, represents that its content is below detection is critical.
The concrete manufacturing condition of aluminium alloy plate is as follows.By DC casting, the aluminium alloy ingot bar of each composition shown in common melting table 1.At this moment, each example is all common, about average cooling rate during casting, is 50 DEG C/minute from liquidus temperature to solidus temperature.Then, each example is all common, after carrying out equal thermal treatment in 540 DEG C × 4 hours, starts hot roughing for ingot bar.Then, each example is common, and then by finish rolling, the thick 3.5mm of hot rolling, becomes hot-rolled sheet (coiled material).For the aluminium alloy plate after hot rolling, each example is all common, and after implementing the black annealing of 500 DEG C × 1 minute, cancel the process annealing in cold rolling mill train way, carry out the cold rolling of working modulus 70%, each example is all common, becomes the cold-reduced sheet (coiled material) of thick 1.0mm.
In addition, each example is all common, and each cold-reduced sheet (coiled material) reeled with the equipment for Heating Processing of continous way, batches, and carries out modifier treatment (T4) continuously on one side.Specifically, be 10 DEG C/sec to the average heating rate of 500 DEG C, be heated to the solid solution temperature described in table 2, cool with the average cooling rate described in table 2 immediately, carry out solid solution and quench treatment.At this moment, at high temperature stop quenching (cooling), and carry out each example of the maintenance process at this temperature, until room temperature does not carry out quench cooled, but stopping quenching (cooling) under quench stop temperature T shown in table 2, the temperature of carrying out hold-time t (unit h) with this temperature keeps processing.This temperature keeps process, carries out in the maintenance stove under each quench stop temperature in the equipment for Heating Processing remaining on described continous way.In addition, temperature hold-time (actual measurement hold-time) t of the plate (coiled material) of this reality, according to the relational expression with described quench stop temperature T, to meet 2.3 × 10 4× exp [-0.093 × T] < t > 2.0 × 10 5the mode of × exp [-0.096 × T] determines.The lower limit calculated according to each quench stop temperature T with this formula and the hold-time of the upper limit, with the hold-time (surveying the hold-time) of the plate (coiled material) of reality, all in unit h (time), display is in table 2.Cooling after this temperature keeps, has carried out each example that this temperature keeps, and all uses cooling body during described quenching, carries out pressure chilling with the speed of cooling of 100 DEG C/S.
In order to compare, the quenching do not carried out under described high temperature stops, but as at present, carry out reheating the comparative example of process (anneal) after being quenched to room temperature (20 DEG C), in other words, cooling when quenching exactly stops temperature too low and reaches the comparative example (7,14,21 of table 2) of room temperature, tests in the mode shown in table 2 simultaneously.
After these modifier treatment, room temperature is placed each end article plate after 7 days and 100 days, and cutting is lower to test plate (panel) (blank), measures each characteristic for test plate (panel), and evaluates.The structure observation of 3DAP is used only to implement for the test portion after after modifier treatment 7 days in addition.The display of its result in table 3.
(cluster)
First, analyzed the tissue of the described thickness of slab central part for test plate (panel) by described 3DAP method, described method tries to achieve the average number density (× 10 of the cluster specified in the present invention separately respectively 23individual/m 3), the standard deviation of the mean radius (nm) of diameter of equivalent circle, the radius of this diameter of equivalent circle.The display of these results in table 3.In addition, show in FIG, the radius (transverse axis: cluster radius) of the diameter of equivalent circle of the described cluster of the example 1 of table 3, the aluminium alloy plate of comparative example 4 and the relation of number density (longitudinal axis).In FIG, example 1 represents with heavy line, and comparative example 4 is represented by dotted lines.
Further, in table 2, among the cluster condition that described the present invention specifies, any one or two kinds containing Mg atom or Si atom add up to more than 10, only simply turn to " more than 10, Mg, Si atom " and are described.In addition, no matter with which atom of the Mg atom contained by it or Si atom for benchmark, any one atom among other the atom adjacent with the atom as this benchmark, its equal below 0.75nm's of distance each other, only simply turn to " below distance 0.75nm " and described.
(coating baking hardening)
After described modifier treatment, place the characteristic of each machinery for test plate (panel) after 7 days or 100 days as room temperature, try to achieve 0.2% yield strength (As yield strength) and breaking elongation (As breaking elongation) according to tension test.In addition, pass through tension test, try to achieve after jointly making these respectively carry out the room-temperature aging of the room-temperature aging of 7 days and 100 days for test plate (panel)s respectively, then the artificial age-hardening carrying out 170 DEG C × 20 minutes process after 0.2% yield strength (after BH yield strength) for test plate (panel) of (after BH).Then, each BH for test plate (panel) is evaluated according to the difference (increasing amount of yield strength) between its 0.2% yield strength.
Described tension test, is from described each for test plate (panel), extracts No. 5 test films (25mm × 50mmGL × thickness of slab) of JISZ2201 respectively, at room temperature carry out tension test.Using the right angle orientation of the draw direction of test film at this moment as rolling direction.Draw speed to 0.2% yield strength is that 5mm/ divides, and yield strength is later for 20mm/ divides.The N number of the feature measurement of machinery is 5, respectively with mean value calculation.Further, in the measuring test film of the yield strength after described BH, utilize this tensile testing machine, after this test film being applied to the prestrain of stamping 2% of mimic panel, carry out described BH process.
(crimping processibility)
Crimping processibility, only places each test plate (panel) that supplies after 7 days or 100 days for room temperature after described modifier treatment capable.The narrow strip test film that test uses 30mm wide, after 90 ° of bending machining of carrying out interior bending R1.0mm to lower hem, clamp the inside that 1.0mm is thick, make folded bent portion further towards inner side, order carries out the pre-curl processing of folded bent to about 130 degree, 180 degree folded bent and end and the flat flanging that touches of inside are processed.
The condition of surface of the generation of the orange peel of the bend (curled portion) of this flat flanging of visual observation, small crackle, large crackle etc., carries out visual assessment according to following standard.0; Flawless, orange peel, 1; Slight orange peel, 2; Very dark orange peel, 3; Tiny area crackle, 4; Wire continuous print surface crack, 5; Fracture
As the alloy numbering 0 ~ 12 of table 1, table 2 numbering 0,1,8,15,22 ~ 30 respectively shown in, each example is in present component compositing range, and carry out manufacturing in preferred condition and range, modifier treatment.Therefore, these each examples are as shown in table 2, meet cluster condition given to this invention.Consequently, even if after the long-term room-temperature aging of each example after described modifier treatment, and the coating baking hardening through between low-temperature short-time, BH is also excellent.In addition, even if after the long-term room-temperature aging after described modifier treatment, crimping processibility is also excellent.Namely, according to the present invention's example, knownly can provide a kind of Al-Si-Mg line aluminium alloy plate, even if it is after the long-term room temperature timeliness of 100 days, when being implemented the car coating baking processing of 170 DEG C × 20 minutes again, higher BH and plasticity (bendability) that yield strength difference is more than 90MPa also can be given play to.
The comparative example 2,9,16 of table 2, uses the invention alloy example 1,2,3 of table 1.But these each comparative examples, as shown in table 2, the speed of cooling of solution treatment departs from preferred condition and too small.Consequently, the mean radius standard deviation of the cluster specified in the present invention is not inconsistent, compared with the example 1 as identical alloy composition, room temperature through time large, spy be room temperature keep the processibility after 100 days or BH poor.
The comparative example 3 ~ 6,10 ~ 13,17 ~ 20 of table 2, uses the invention alloy example 1 of table 1.But these each comparative examples, as shown in table 2, the temperature after described quenching stops keeps treatment condition to depart from preferred scope.Consequently, the cluster condition specified in the present invention is not inconsistent, compared with the example 1 as identical alloy composition, particularly room temperature keep the processibility after 100 days or BH poor.
The comparative example 7,14,21 of table 2, uses the invention alloy example 1,2,3 of table 1.But, these each comparative examples, as shown in table 2, do not carry out at preferred temperature quenching stop, such as, as patent documentation 4, carry out be carry out reheating after being quenched to room temperature (20 DEG C) and anneal reheat process.Consequently, the mean radius standard deviation of the cluster specified in the present invention is not inconsistent, compared with the example 1 as identical alloy composition, room temperature through time large, particularly room temperature keep the processibility after 100 days or BH poor.
In addition, the comparative example 31 ~ 38 of table 2, although I keeps treatment condition interior containing the temperature after described quenching stopping, although manufacture in preferred scope, but use the alloy numbering 13 ~ 20 of table 1, the content of Mg or Si of element must depart from the scope of the invention respectively, or impurity element amount is too much.Therefore, these comparative examples 31 ~ 38, as shown in table 3, compared with each example, BH and crimping poor in processability.
Comparative example 31 is that the alloy 13, Si of table 1 is very few.
Comparative example 32 is that the alloy 14, Si of table 1 is too much.
Comparative example 33 is that the alloy 15, Fe of table 1 is too much.
Comparative example 34 is that the alloy 16, Mn of table 1 is too much.
Comparative example 35 is that the alloy 17, Cr of table 1 and Ti are too much.
Comparative example 36 is that the alloy 18, Cu of table 1 is too much.
Comparative example 37 is that the alloy 19, Zn of table 1 is too much.
Comparative example 38 is that the alloy 20, Zr of table 1 and V are too much.
The mean standard deviation of the radius of the diameter of equivalent circle of the described cluster of described example 1, as table 3, is 0.29 in specialized range, the described mean standard deviation of described comparative example 4, as table 3, is above 0.58 of upper limit regulation.This comparative example 4, as described in shown in Fig. 1 dotted line, the mean radius of diameter of equivalent circle be more than 1.2nm, below 1.5nm quantity (number density) than described example more than 1, the peak value of the longitudinal axis is high.But, compared with the example 1 in described Fig. 1 shown in solid line, the distribution of the size of described cluster, especially to region (right side of Fig. 1) expansion that cluster radius is large, larger than the mean standard deviation of example 1, exceed upper limit regulation.Result is also known thus, in order to make the BH after long-term room-temperature timeliness improve, not only needing the mean radius of the diameter of equivalent circle of described regulation cluster to meet regulation, and needing to make its mean standard deviation little of below 0.35nm.
Therefore, the result according to above embodiment confirms, for the BH improved after long-term room-temperature timeliness, meets each condition necessity existing of the cluster specified in described the present invention completely.Also confirm in addition, for obtaining the critical meaning of such cluster condition and each important document of becoming to be grouped into BH etc., of the present invention or preferred manufacturing condition so that effect.
Table 1
* the empty hurdle of the numerical value of each element represents below detection boundary.
Table 2
Table 3
[utilizability in industry]
According to the present invention, the 6000 line aluminium alloy plates that the BH under condition and the plasticity after long-term room-temperature timeliness between the low-temperature short-time after a kind of long-term room-temperature timeliness all have both can be provided.Consequently, as the component of the Transport Machinery of automobile, boats and ships or vehicle etc., family's electrical article, building, works and component use, in addition, the application of 6000 line aluminium alloy plates can particularly can be expanded in the component of the Transport Machinery of automobile etc.

Claims (2)

1. an aluminium alloy plate for coating baking hardening excellence, is characterized in that, is in mass % containing Mg:0.2 ~ 2.0%, Si:0.3 ~ 2.0%, the Al-Mg-Si-type aluminum alloy plate that surplus is made up of Al and inevitable impurity, wherein,
As the aggregate of the atom measured by three-dimensional atom probe field-ion microscope, the aggregate of this atom contains any one or two kinds of the Mg atom that adds up to more than 10 or Si atom, with any one atom of wherein contained Mg atom or Si atom for benchmark time, mutual distance as any one atom among the atom of this benchmark and other adjacent atom is below 0.75nm
Further, with 6.0 × 10 23individual/m 3above, 25.0 × 10 23individual/m 3following average number density contains the aggregate of the atom meeting these conditions, the mean radius meeting the diameter of equivalent circle of the aggregate of the atom of these conditions is more than 1.2nm, below 1.5nm, further, the standard deviation of the radius of its diameter of equivalent circle is below 0.35nm.
2. the aluminium alloy plate of coating baking hardening excellence according to claim 1, wherein, described aluminium alloy plate in mass % also containing, for example under one or more element: below Mn:1.0% but containing 0%, below Cu:1.0% but containing 0%, below Fe:1.0% but containing 0%, below Cr:0.3% but containing 0%, below Zr:0.3% but containing 0%, below V:0.3% but containing 0%, below Ti:0.05% but containing 0%, below Zn:1.0% but containing 0%, below Ag:0.2% but not containing 0%.
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