JPH02122055A - Manufacture of rolled aluminum alloy sheet for forming - Google Patents

Abstract

PURPOSE:To manufacture a rolled Al alloy sheet excellent in formability, corrosion resistance, and weldability and having high strength by subjecting an ingot of Al alloy having a specific composition in which Si and Mg are incorporated and respective contents of impurities are limited to homogenizing treatment, to rolling, and then to specific heat treatment. CONSTITUTION:A molten alloy having a composition which contains 0.6-1.2% Si, and 0.6-1.11%, Mg and also contains, as impurities, <0.15% Fe, <0.05% Cu, <0.05% each of Mn, Cr, Zr, and V, and <0.05%, in total, of other impurities and in which the total content of the elements other than Al, Si, Mg, and Fe is regulated to <0.10% is subjected to semicontinuous casting, and the resulting ingot is subjected to homogenizing treatment at 450-590 deg.C for 1-48hr and then to hot and cold rollings. Process annealing is carried out at 260-450 deg.C for <=48hr in the course of the above procedure, and the cold rolled sheet is subjected to solution heat treatment at 450-590 deg.C and hardened at >=5 deg.C/sec cooling rate. After subjected to straightening, the rolled sheet is heated up to 60-360 deg.C, held at the above temp. for a time within a shaded region B, and then cooled. The above heating and cooling are carried out at heating and cooling rates within a shaded region A. By this method, the rolled Al alloy sheet of Al-Si-Mg type for forming excellent in formability, corrosion resistance, and weldability can be obtained.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a rolled aluminum alloy plate for forming work that has good corrosion resistance and weldability, and a method for manufacturing the same. The present invention relates to a method for manufacturing aluminum alloy rolled sheets for forming and processing, which are suitable for single-use applications such as automobile bodies.

(Prior Art) In the past, cold-rolled steel sheets were mainly used for the body sheets of automobile bodies, but recently, due to the demand for reducing the weight of car bodies, consideration has been given to using rolled aluminum alloy sheets. Body sheets for automobile bodies are press-formed, and as they are used extensively, they have excellent molding properties, especially the Lüders mark, which has excellent molding properties and has excellent appearance properties during molding. It is required that no flow lines occur, and since the baking coating is applied, the strength of the baked one-inch coating bond is required to be high.

By the way, there have been various types of aluminum alloy plates used for forming products that require strength, but the main types can be classified as follows depending on the alloy composition.

(a) 5052 alloy (Mg-2, 2-2.8%, Cr0115-0.35
% balance Si and unavoidable impurities) or the same <5182 alloy (Mn0.20-0.50%, Mg-1
, 0-5.0%, the remainder ρ and unavoidable impurities)
Material.

(b) 2036 alloy, which is a heat-treatable AR-Cu alloy (
Cu-2,2'-3,0%, Mno, i ~ o, ,
qqg, Mg-0.3-0.6%, balance, l and unavoidable impurities) TII treated material.

(c) Heat-treated A12 T4-treated material of MgZn-Cu alloy. Examples of this type of aluminum alloy include the alloy of JP-A No. 52-141409, the alloy of JP-A No. 53-1039
There are alloys such as No. 14 alloy and JP-A-57-98648 alloy.

Also, Nikkei New Material, 1986.4-7, No.
, 8. Al-t1.5Mg-0,38Cu1.46Zn-0 introduced on pages 63-72, especially page 64,
There is also 18Fe-0,09Si.

(d) 6009, which is a heat treatment type AR-Mg-Si alloy
Alloy (Mg-0.11-0.8%, Si-o, 6-1.
0%, Cu-0.15-0.6%, Mn-0.2-0.
8%, remaining Si and unavoidable impurities! i+i]) T4
Treated material and same <6010 alloy (Mg-0,6~1.0%
, Si-0.8~1°2%, Cu-0.15~0.6%
, MnO12~0-89'11, remainder Si and unavoidable impurities) T4 treated material. According to Japanese Patent Publication No. 59-39 TL 99 which proposes these alloys, 0.4 to 1.2
%Si, O14~1.1%Mg, 0.05~0.35%
In addition to Fe, 0.1-0.6% Cu, 0.2-0.
8% Mn, 0.1-0.3% Cr, and 0.05-0
．． A T4 or T6 treated material having a composition containing at least one of 15% Zr is disclosed.
(A) 1% Si, 0.6% M proposed in No. 15148
g, (B) 1.8%Si, 0.6%Mg, (C) 18
S 1.0, 2%'VI g, (D) 1.2%Si
, 4 points of 0.6% Mg? has a Si, Mg composition, and further contains 0.3% or less of Cr, Mn, Zr, or/
AC120 standardized material containing ' and Ti.

However, it has been difficult for these conventional aluminum alloys to fully satisfy all of the above-mentioned characteristics required for body sheets of automobile bodies.

That is, the alloy (a) has insufficient strength, has the problem of easily generating Lüders marks during molding, and further has the problem of reduced strength during the paint baking process. In addition, the alloy described above had poor formability and also had the problem that the strength of the paint baking process decreased depending on the process. Furthermore, the alloy (c) has problems in that the moldability, especially the bendability, is not sufficient, and the strength decreases during the paint baking process.

The alloy (d) has features such as being hard to produce Lüders marks and having strength equivalent to that of cold-rolled steel sheets due to its hardenability, but the elongation, which is a measure of formability, is lower than that of cold-rolled steel sheets. known to be significantly lower.

As mentioned above, since IK, aluminum alloys have the characteristics required for automobile body sheets, that is, they have excellent formability, especially excellent elongation and stretch formability, and there is no Lüders mark. In addition, research and development has been carried out to satisfy all the requirements of strength, especially high strength after coating f:f, and excellent corrosion resistance and weldability. Problem) In the Si-91-Mg alloy system to which the present invention belongs, alloys that satisfy the above requirements to a considerable extent are known, but they are less expensive than steel sheets commonly used for automobile body sheets. The demands on the performance of rolled aluminum alloy sheets, which are disadvantageous in terms of performance, must become stricter, and an aluminum alloy rolled sheet that satisfactorily meets these requirements has not yet been provided.

Specifically, first, the elongation, which is an index of moldability, is low, and therefore the moldability is still insufficient.

In addition, regarding the corrosion resistance of aluminum alloys used for body sheets of automobile bodies, the conventional opinion was that if there were no defects in Paint-F, the corrosion resistance of the aluminum alloy itself was superior to that of Sr1 sheets, so there was no problem (Nikkei cited above). New Materials), and JItsu@ (Japanese Patent Publication No. 59391199, cited above), which investigated the corrosion resistance of chrome plating films against blistering defects using CASS tests. Recently, however, the requirements for corrosion resistance of rolled aluminum alloy sheets for forming have become clearer, and specific properties that have not been considered in the past have been required. In other words, in addition to the corrosion resistance and pitting resistance of unpainted plates related to the properties of the A2 alloy itself, it is required that the coating film does not peel off (blister), thread-like corrosion, etc. occur after baking and painting.

However, there is no known aluminum alloy rolled sheet for forming that has such excellent corrosion resistance and also has both strength and formability.

Most of the welding of body sheets of automobile bodies is done by spot welding, but depending on the location, M I
There are parts where so-called arc welding using G or TIG welding is performed. Since relatively thin plates with a thickness of 2.0 mm or less are arc welded inside the shell, welding is generally difficult, so there is a need for rolled plates with good weldability.

This invention was made against the background of the above-mentioned circumstances, and has excellent molding processability, especially elongation and stretchability, and does not generate Lüders marks or flow lines, which are poor appearance during molding, and has high strength. However, in particular, there is no decrease in strength during the paint baking process after molding, but rather the strength increases through the paint baking process after molding, so that molded products with high strength can be obtained, and corrosion resistance and weldability are improved. improved aluminum alloy rolled plate,
The object of the present invention is to provide a method for producing the same.

(Means for Solving the Problems) The first aspect of the present invention is as an alloying element: SiO, 6 to 1.2
%, Mg-0.6~1.1%, as impurity: Fe-
Less than 0.15%, Cu-005%, Mn, Cr, Z
Each of r and ■ is less than 0.05%, the total amount of other impurity elements is less than 0.05%, Al2. Si, Mg, F
Half an alloy molten metal containing less than 0.10% of elements other than e! ! The ingot obtained by continuous casting was cast at 450
Heating at ~590°C for 1 to 48 hours to perform a homogenization treatment that also serves as rolling heating, followed by hot rolling and cold rolling, and holding temperature range 260 to 450 immediately after hot rolling or in the middle of cold rolling. A rolled plate formed by intermediate annealing for a holding time of 48 hours or less at ℃ and then cold rolling was
Solution treatment within the temperature range of 50-590℃, 5℃/
Quenched at a cooling rate of s e c or higher, then subjected to strain straightening, to a temperature within the range of I & 60 to 360°C.
Heating at a heating rate within the shaded area shown in the figure, holding at that temperature for a time within the shaded area shown in Figure 2, and then cooling at a cooling rate within the shaded area shown in Figure 1. The second aspect of the present invention is a method for producing an Ag-51Mg aluminum alloy rolled plate for forming, which is characterized by excellent formability, corrosion resistance, and weldability. 1.
2%, Mg0.6-1.1%, as impurity: Fe-0
．． Less than 15%, Cu-0°05%, Mn, Cr, Z
Each of r and ■ is less than 0.05%, the total of other impurity elements is less than 0.05%, Ag, Si, Mg, Fe
A molten alloy containing less than 0.10% of all other elements is cast by continuous casting, and the obtained coiled ingot is cold rolled to form a rolled plate, which is melted in a temperature range of 450 to 590°C. quenched at a cooling rate of 5°C/sec or higher, then subjected to strain correction, and then heated to 60 to 360°C.
heating at a heating rate within the shaded area shown in Figure 1 to a temperature within the range of , held at that temperature for a time within the shaded area shown in Figure 2, and then heated at a heating rate within the shaded area shown in Figure 1. Formability characterized by cooling at a cooling rate within a range,
This is a method for manufacturing an Al2-51-Mg aluminum alloy rolled sheet for forming process, which has excellent corrosion resistance and weldability.

First, the reason for limiting the composition of the present invention will be explained.

Si: A part of the amount added is A2 as metal Si particles.
It is present in alloys and improves formability, especially elongation properties. Further, some other Si forms Mg2Si together with Mg, and contributes to the strength direction -L by precipitation hardening. In particular, M
It is important for strength improvement to have a sufficient excess of Si from the stoichiometric composition of M g2 Si, which produces g, Si-, and to further produce metal Si particles. This excess Si particles are also effective in making recrystallized grains finer.

In addition, although the mechanism is unknown, Si
It also improves the weldability of arc welding such as G. Si content is 0
．． If the content is less than 6%, the effects of improving strength, formability and weldability are insufficient, and the content is 1.2%.
If the value exceeds , the thread rust resistance decreases.

As mentioned above, Mg+Mg becomes Mg due to the coexistence with Si.
Generates 2Si to impart strength.

If Mg is less than 0.6%, the strength is insufficient, and method 1.1
%, the elongation decreases, so the Mg content range is 0.6 to 1.1%. 9Cu has excellent corrosion resistance, especially yarn rust ff
Decreases rJi properties. If the Cu content exceeds 0.05%, the harmful effects become noticeable, so the Cu content should be set to 0.05%.
It was set to less than 0.05%.

Fe reduces yarn rust resistance and moldability. If the Fe content exceeds 0.20%, the amount of crystallized substances increases, and thread rust is likely to occur from these, and cracks are more likely to occur during molding9. Therefore, in terms of characteristics, the lower the Fe content, the more Although it is desirable, the upper limit of Fe is less than 0.15%, considering the economical point of view and the permissible level of occurrence of yarn rust.

The preferable upper limit of Fe is less than 0.05%.

Mn, Cr, Zr, and V are often added primarily for the purpose of converting crystal grains to aS, but it has been found that these elements reduce yarn rust resistance. Since these elements also reduce moldability, it is desirable that their content be as low as possible. The upper limit of its content needs to be less than 0.05%.

All other impurities have an adverse effect on yarn rust resistance. Considering the economic aspect, Mg.

It is important that the total amount of elements excluding Si-, Fe, and Si does not exceed 0.10%.

In addition, in ordinary aluminum alloys, a small amount of Ti or Ti and B may be added to refine the crystal grains of the ingot, and the rolled aluminum alloy sheet of the present invention also contains the remaining Si, alloy components, and impurities. may contain a trace amount of Ti or Ti and B,
However, when adding Ti, if it is less than 0.005%, the effect cannot be obtained, and if it is more than 0.15%, primary crystal TiSi3 will crystallize and impair moldability.
It is preferably within the range of 15%. In addition, when B is added together with Ti, if it is less than ippm, there is no effect, and if it exceeds 500 ppm, coarse particles of TiB2 will be mixed in, impairing the moldability, so it is preferable that B is within the range of 1 to 500 ppm. .

In the first starting step of the present invention, a molten metal having the above alloy composition is semi-continuously cast into an ingot having a rectangular cross section. The casting speed is not particularly determined as long as a rectangular ingot can be cast, but it is usually preferable to cast within a range of 25 mm/min to 250 mm/min.

This ingot is heated at 450 to 590°C for 1 to 48 hours prior to hot rolling. When heating an ingot, the purpose of which is to eliminate unevenness in the ingot and improve formability.
If the heating temperature is less than 450°C or the heating time is less than 1 hour, homogenization will be insufficient, if the heating temperature exceeds 590°C, local melting will occur, and if the heating time exceeds 48 hours, economic efficiency will decrease. And the homogenization effect is saturated.

Thereafter, the hot rolled aluminum alloy plate is successively cold rolled and reduced to a thickness of 3.0 to 0.5 mm.

Intermediate annealing is performed during cold rolling or between hot rolling and cold rolling to improve the properties of the aluminum alloy sheet, particularly its strength and formability, due to the effect of recrystallization. In other words, if coarse grains are generated during hot rolling, if the hot rolled sheet is cold rolled and solution treated without intermediate annealing,
A band structure is formed in which these coarse grains extend in the rolling direction,
Waviness called ridging or flow lines occurs during molding, which deteriorates the appearance of the molded product. Therefore, once recrystallization is caused by intermediate annealing, it becomes possible to eliminate the influence of coarse grains produced during hot rolling. here,
If the intermediate annealing temperature is less than 280°C, recrystallization does not occur, and if the temperature exceeds 450°C, grain coarsening tends to occur.

Moreover, intermediate annealing for which the holding time exceeds 48 hours is not economical.

In order to fully exhibit the characteristics of the above-mentioned alloy composition of the present invention, it is necessary to solution heat the rolled aluminum alloy plate at 450 to 590°C and cool it at a cooling rate of 5°C/sec or more. Through this solution treatment, the amount of solid solution Mg and Si necessary to obtain a predetermined strength and moldability can be obtained. If the temperature is less than L150°C, solutionization is insufficient,
Sufficient strength cannot be obtained after cooling and baking.

On the other hand, if the temperature exceeds 590°C, there is a risk of eutectic melting.

Further, if the quenching rate (cooling rate) is slower than 5°C/sec, not only the strength will be insufficient, but also the corrosion resistance against intergranular corrosion etc. will deteriorate. Therefore, a quenching rate of 5° C./sec or higher is required.

In consideration of mass productivity, etc., the solution treatment is preferably a technique in which the coil is subjected to continuous solution quenching treatment. The holding time may be 0 (cooling at the same time as the predetermined temperature is reached), but it is usually preferably 10 seconds or more.

When continuously solution hardening a coil, from an economical point of view, the upper limit of the holding time at the solution temperature is 5 minutes. When this continuous solution quenching is used, a heating rate of 5° C./sec or more is usually obtained, so crystal grains are refined and moldability is improved.

The original purpose of the solution treatment is to sufficiently dissolve alloy elements contributing to strengthening, such as Mg and Si, into a solid solution again. Therefore, in order to obtain the required strength, it is only necessary to re-dissolve the alloying elements that contribute to strengthening in the amount necessary to obtain the strength. Particularly in automotive molding applications where complete solution treatment is performed, moldability may have to be more important than strength depending on the part of the vehicle body.

In this case, a so-called incomplete solution treatment may be performed in which the Mg content and Si content are increased and MgSi is redissolved in an amount necessary for strengthening during the solution treatment.

Specifically, it is sufficient to shorten the time or lower the temperature during solution treatment. In particular, when a continuous solution hardening device is used, it becomes possible to shorten the holding time, thereby increasing the line speed during continuous solution treatment, resulting in economical advantages. When the state of existence of Mg and Si before the incomplete solution treatment is changed, the amount of Mg and Si that is re-dissolved changes accordingly, and the m-type properties change. . Therefore, it is important to keep the presence state of Mg and Si constant before the solution treatment.

In order to control the presence of Mg and Si before solution treatment, it is necessary to strictly control the hot rolling conditions before hot rolling. It is even more preferable to include it in the process.

In aluminum alloy rolled plates that have undergone intermediate annealing at the temperatures described above, the M determined by the thermal history before intermediate annealing is
The existing state of Mg and Si- is stabilized and constant, and as a result, the amount of Mg and Si re-solid-dissolved by the incomplete solution treatment becomes stable, making it easier to stabilize mechanical performance.

Rapid heating during solution treatment and rapid cooling during quenching cause the rolled plate to deform and become strained, so in order to remove this strain, strain correction is performed after the solution death process f1m. This distortion correction includes leveling, tension leveling, skin bath,
Alternatively, it may be stretched or the like, and in either method, distortion is removed by applying a slight cold working. The degree of processing in the strain straightening process varies depending on the degree of strain after solution annealing and quenching, but usually by including the strain straightening process, the yield strength increases by more than 1 kg/mm2, and the formability improves. decreases by 0.2 mm or more in Erichsen value.

The rolled plate whose forming performance has been degraded due to the strain straightening process is then subjected to a final heat treatment (also referred to as fi final annealing) in which the sheet is heated to a temperature in the range of 60 to 360°C, held, or immediately cooled. This heat treatment is carried out in the 117th shaded area, that is, points A, B, and C, corresponding to the heating holding temperature.
, D, and E at a heating rate within the area surrounded by the straight line or curved line, and the line connecting the hatched area in Figure 2, that is, points a, b, c, and d, corresponds to the heating holding temperature. It is held for a time within the range surrounded by the curve, and further cooled at a cooling rate within the shaded area in FIG. 1 corresponding to the heating holding temperature. Here, the temperature and heating/cooling rate at each point A to E in FIG. 1 are as follows.

A: 60℃14X10-3℃/secB:14
0℃14X10-'℃/5ecC: 360℃13×1
0℃/secD: 230℃54X10'℃/
5ecE; 60℃14X10'℃/sec and second
The temperature and time at each point a to d in the figure are as follows.

a: 200°C, 0sec b: 360°C, 0sec c: 130°C, 105sec d: 60″C110's e c In this way, the ranges of heating rate, holding time, and cooling time were determined for the final heat treatment after straightening the strain. Explain why.

Since the Si-Mg-Si alloy targeted by this invention is a heat-treatable alloy, there is a possibility that not only the processing strain will be removed during heating, holding, and cooling, but also age hardening will occur, in which case the strength will decrease. There is a risk that moldability may decrease due to the increase in moldability, or the paint baking strength after molding or the strength after T6 treatment may decrease due to overaging. Therefore, it is necessary to eliminate processing distortion in the distortion straightening process while preventing these problems from occurring, and it is also necessary to consider other aspects such as maintaining flatness and economic efficiency. Each range was determined as follows.

(Heating rate) In the area below the straight line AI3 in Figure 1, there is no problem with the performance of the material, but if the temperature is heated more gradually than this, it will take an extremely long time to raise the temperature, resulting in a decrease in productivity and an economical It becomes irrelevant. Therefore, the heating rate was set above the straight line AB.

In the region where the heating rate is slow below the curve [3C in FIG. 1], age hardening occurs during heating and temperature rise, and although the strength increases, the moldability decreases. Therefore, the area was set above the song mBC.

Next, in the region above the straight line DC, heating is too rapid and distortion occurs during temperature rise, and the effect of distortion correction is lost. Therefore, the area was set below the straight line DC.

The area above the straight line DE is a heating rate that substantially exceeds the heating rate due to oil bath injection, and although higher heating rates are effective, they are not practical and are meaningless, so the area below the straight line DE is The area of

On the left side of the straight line EA, that is, at a low heating temperature of less than 60° C., the processing strain caused by strain correction cannot be completely removed regardless of the heating rate, so the area on the left side of the straight line EA was excluded.

From the above, although the range of the heating rate varies depending on the heating holding temperature, it is necessary to set it within the shaded area surrounded by points A, B, C, D, and E in FIG.

(Holding temperature/time) Regarding the straight line ab in Fig. 2, the holding temperature is 200~
At 360° C., even if cooling is started immediately after reaching that temperature range, that is, by setting the holding time to 0 seconds, the strain caused by processing can be removed. Therefore, in the holding temperature range of 200 to 360°C, the lower limit of the holding time was set to 0 seconds, that is, the straight line ab.

In addition, in the upper right region of curve bc, processing strain can be removed, but strength increases due to high temperature age hardening, and formability decreases.In addition, especially in the high temperature region, overaging occurs, and formability decreases. , predetermined strength cannot be obtained due to baking one-dimensional painting or T6 treatment after molding. Therefore, it is necessary to set the area to the lower left of the curve bc.

Above the straight line (d), processing strain can be removed and moldability can be restored, but the holding time exceeds 24 hours and it is economically meaningless, so it is set below the straight line cd.

In the region below and to the left of the curve da, the heat necessary to remove processing strain is not applied, and recovery of moldability is not observed.

Therefore, it is necessary to set it to the upper right area of the song 1ida.

From the above, although the heating holding time differs depending on the heating holding temperature, it is ultimately necessary to keep it within the shaded area surrounded by points abcd in FIG. 2.

(Cooling Rate) Like the heating rate, the cooling rate must be within the shaded area surrounded by ABCD in FIG.

In the region below the straight line AB, there is no problem with the performance of the material, but slow cooling beyond this is not economical because cooling takes a significantly long time, so the region above the straight line AB was selected.

In the region below the curve BC where the cooling rate is slow, aging precipitation occurs during cooling, reducing formability, and due to over-aging, it becomes impossible to obtain the specified strength by baking painting or T6 treatment after forming. . Therefore, the area was set above curve BC. If the cooling rate is above the straight line DC, the cooling rate will be too high and cause distortion in the material.
The effect of strain correction before the final heat treatment is lost. Therefore, the area was set below the straight line DC.

In the region above the straight line DE, the cooling rate substantially exceeds water cooling and is practically meaningless, so the cooling rate is set below the straight line DE.

On the left side of straight line EA, regardless of the cooling rate,
Processing distortion cannot be removed. Therefore, the area was set to the right of the straight line EA.

Therefore, the cooling rate and the heating rate vary depending on the heating and holding temperature, but the shaded area surrounded by ABCDH in FIG. 1 is used.

If the final heat treatment under the above conditions is performed after the strain correction process, the processing strain introduced in the strain correction process will be removed, and the formability, especially the stretchability, deteriorated due to the strain correction will be restored, and the solution process will be improved. It is possible to restore the T4 tempered state obtained by treatment quenching to a state with good moldability, especially stretchability. In addition, in this final heat treatment, appropriate conditions are set so that age hardening and over-aging do not occur, so there is no deterioration in molding workability due to these conditions, and there is no need for post-molding 1-inch painting or T6 treatment. The required strength can be obtained by Furthermore, since the final heat treatment line CI- is set so as not to cause new distortion due to rapid heating and cooling, the flatness improvement effect of the previous distortion correction process can be maintained.

After that, surface cleaning, chemical conversion treatment, molding, welding, painting, baking hardening, etc. are performed.

(Left below) Instead of a large semi-continuously cast ingot, in the second aspect of the present invention, molten metal is continuously supplied between two rolls to produce a continuously cast plate or coil. In this case, there is no particular restriction on casting speed.

In addition, although cold rolling is usually performed without hot rolling, in order to promote homogenization prior to rolling and improve cold rollability,
0-b You can preheat it. Subsequently, the plate is cold rolled to a thickness of 3.0 to 0.5 mm.

Intermediate annealing may be performed at the beginning of cold rolling or in the middle of cold rolling, but this differs from the first case of the present invention in which rolling is performed through semi-continuous casting. It is omitted when there is no risk of these rolling troubles. Here, when the temperature of intermediate annealing is less than 280°C, rolling workability is improved,
Moreover, when the temperature exceeds 450°C, coarsening of crystal grains tends to occur. Moreover, intermediate annealing for which the holding time exceeds 48 hours is not economical.

Furthermore, in consideration of mass productivity, etc., it is preferable to use a technique in which the coil is continuously subjected to solution hardening treatment. The holding time may be 0 (cooling at the same time as the predetermined temperature is reached), but it is usually preferably 10 seconds or more.

When continuously solution hardening a coil, from an economical point of view, the upper limit of the holding time at the solution temperature is 5 minutes. When using this continuous solution quenching, the temperature is usually 5℃/s.e.c.
Since the above heating rate can be obtained, the grain strength is reduced and moldability is improved.

Solution treatment was originally applied to Mg,! The purpose of this is to sufficiently re-dissolve alloy elements that contribute to strengthening, such as 9i. Therefore, in order to dissolve the necessary amount of reinforcing elements into solid solution, it is necessary to perform solution treatment at a temperature of 450 to 590°C9.For economic reasons, it is better to keep the holding time at the solution treatment temperature short. preferable. On the other hand, as is conventionally known, in continuous casting, the molten metal is directly cast into a plate having a thickness of 11 to 10 mm, so the cooling rate during casting is higher than in semi-continuous casting. Therefore, in continuous casting, the amount of solid solution of Mg and Si in the casting stage and subsequent stages becomes larger than in semi-continuous casting. In addition, according to continuous casting, Mg and Si
The intermetallic compounds produced during casting are significantly smaller than in semi-continuous casting. Due to these features of continuous casting, plates obtained by continuous casting have the following properties:
The intermetallic compound is easily dissolved, the amount of solid solution is increased, and as a result, the solution treatment is easier to proceed. therefore,
Even if a short-time solution treatment in a continuous furnace is applied to a plate obtained from a continuously cast material, the strength decreases less than in the case of a semi-continuously cast material. On the contrary, during solution treatment (assuming that 'F- is the same), the strength of continuous cast material is improved compared to that of semi-continuous cast material.

Soaking treatment and intermediate annealing are performed when it is necessary to improve cold rollability. If the temperature of soaking and intermediate annealing exceeds 400"C, coarse Mg and Si will precipitate, and as a result, the advantage of continuous casting with forced solid solution of Mg2Si will be lost.However, at temperatures exceeding 400"C, these Even if the above treatment is performed, properties equivalent to those of semi-continuously cast material can be obtained, so temperatures exceeding 1100° C. are allowed as in the first case.

In the second case, the conditions for the final heat treatment after straightening the strain and the reasons for their limitations are the same as in the first case.

(Effect) Solution death ■! The properties of the aluminum alloy rolled sheet of the present invention in the artificially aged (T4) state after 1T are as follows.

Mechanical properties: proof stress (σ, 4□) - 11 kg/mm2 or more, tensile strength - (σ,) about 25 kg/mm2 or more, and elongation about 29% or more.

Formability: Erichsen value - equivalent to or higher than 6010 alloy,
Minimum bending (180°) - Equivalent to 6010 alloy, no appearance defects such as tool L, Lüders marks, flow lines, etc.

Bake hardenability: When heat treated at 175°C for 1 hour, assuming 1 inch of paint baking, the yield strength increases by 1 kg/mm2 or more.

Corrosion resistance: The corrosion resistance of the painted plate after the normal three-coat coating for automobile bodies consisting of electrodeposited undercoat, intermediate coat, and topcoat is 601.
Superior to 0 alloy, equivalent to or better than 5182 alloy.

Weldability: The weldability is better than, for example, a thin plate of 6009 alloy, which has been conventionally TIG or MIG welded.

The aluminum alloy rolled sheet for forming processing obtained by the manufacturing method of the present invention having the above characteristics has a better balance of various properties as a body sheet material for automobile bodies than conventional rolled sheets, and has a significantly increased a property. ing.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

(Example) Example 1 A molten aluminum alloy having the composition shown in Table 1 was cut into 500 cross sections.
Semi-continuous casting was performed at a casting speed of 60 mm/min into a slab of x1000 mm. Subsequently, after performing homogenization treatment at 530°C for 10 hours, [J! Deep rolled to 14 mm,
Subsequently, the plate was cold-rolled to J″: J-3mm.Here, as shown in Table 2, some of the cold-rolled plates were heated at 350°C
Intermediate annealing was performed for hr. Subsequently, cold rolling was performed to a plate thickness of 1 mm. Next, the cold rolled plate coils were solution heat treated and hardened by continuous solution heat treatment under the conditions shown in Table 2. Here, since some comparative alloys are non-heat treated alloys, they were not subjected to continuous solution quenching, but were subjected to normal batch annealing (350
Solution treatment was carried out at ℃×2 hr). The coils subjected to continuous solution treatment were subsequently corrected for deformation by tension leveling. Next, a part of the straightened plate was left as is, and another part was subjected to final annealing as shown in Table 2, and then made into a final rolled plate. The various final rolled plates obtained in this way have mechanical properties, formability,
Tests were conducted on 1-inch hardenability, Lüders mark, flow line, weld cracking resistance, steel properties, etc.

(Left below) Table 3 shows the mechanical properties and moldability of these materials.

In addition, proof stress and tensile strength are kg/mm2, elongation is 5°≦,
Erichsen values and minimum surface run-outs are expressed in mm.

A notch Erichsen test was conducted for the Zünders mark, and a 100φ ball head overhang test was conducted for the flow line, and the appearance was observed and judged based on the following criteria.

○: Not at all Δ: Recognized (cannot be used for applications with severe appearance) ×: Strong (blank below) As is clear from Table 3, AB and C according to the present invention both have excellent stretchability and bendability. Moreover, it can be seen that there are no Luders marks or flow lines.

Symbols D to J are alloys of the present invention processed by a method that does not meet the requirements of the method of the present invention.

The flow line is defective because there is no intermediate annealing.

In the case of symbol E, final annealing was not performed, so that the formability deteriorated due to leveling of the solution-treated plate.

Symbols F to J have final annealing conditions outside the scope of the present invention.

. In the case of symbol G, the holding time is short compared to the temperature, so that there is little recovery of the deteriorated moldability.

For samples F, H, and I, aging has progressed too much and moldability has deteriorated. With F, the heating rate is too slow compared to the temperature, and with I (because the holding time is too long compared to the temperature,
In case (2), the cooling rate is too slow relative to the temperature, so aging progresses excessively.

Although recovery of moldability was achieved with symbol J,
Because the cooling rate is too high, the deformation that was corrected by leveling is occurring again. Therefore, it is clear that performance such as moldability and deformation will deteriorate unless the method of the present invention is used.

In addition, for materials with symbols A to Q, for plates after aging at room temperature,
In order to investigate the change in strength due to the paint baking process after molding, 5% cold processing, which corresponds to product molding, was 10%.
175 which corresponds to °6 cold working and further paint baking
℃ × 1 hour heat treatment without cold working (0% cold worked material), 5% cold worked material, 10?
≦This was done on cold-worked materials, and the strength at each stage was investigated.

The results are shown in Table 4.

(Hereinafter, blank space) From 71 to
It is clear that the process-ζ intensity is in the direction of FJ-.

Next, we TIG welded the fishbone crack test piece and calculated the cracking rate. Beta. The results are shown in Table 5.

The TIG welding conditions are: TIG automatic welding (no overlay)
;Current 60A;Traveling 25cm/min;? b, fffi
Tungsten'2.4mmφ; Ar air flow; arc length 3
It was mm.

The dimensions of the fin sheet T and bone test piece are shown in Figure 3.

(Margin below) Next page Weldability Here, the cracking rate is calculated by dividing Lb by the following formula.

Table 5 shows that the invention alloy has excellent weldability.

Summarizing the results of 1- above, we find the following.

Comparative example L (composite #1 with a composition of low Si, high Mg, and high Cu)
L5) has poor strength, poor formability, poor weldability, and high C.
Comparative example K (alloy 71) of u has poor weldability 7f, S
i. Comparative Example M (alloy 6), which has a high Mg composition, has poor formability.

N-Q is a typical conventional molding material.

The materials of the invention are superior to these in terms of overall properties. In other words, the material of the present invention has moldability, elongation, sinterability (= f hardenability, and weldability) for 2036 (symbol 0), and for A12-Mg-ZnCu (symbol Q),
It is superior to 6010 (symbol P) in elongation, formability and weldability in terms of hardenability and weldability.

Next, rolled plate A, [1, C, L, L N,
Cut O, P, and Q to make 7016Illx150II+
A test piece of No. 1 was prepared and a corrosion resistance experiment was conducted.

Experiment 1: Corrosion resistance test of unpainted plate The surface of the rolled plate was degreased with 10% NaOH aqueous solution (50°C) for 1 minute, washed with distilled water, and further degreased with 15% HNO
] Remove smut using an aqueous solution and do not wash.

Regarding rolled plates treated in this way, JIS Z
A salt spray test was conducted using 2371. Spray time is 1
000 hours. Corrosion resistance was evaluated by visual inspection based on the following criteria.

◎: No bits at all O: Several pits △　; Quite a bit X: Bits on the entire surface The results are shown in Table 6.

(Margin below) Table 6 Judgment Results Experiment 2: Corrosion of blisters and thread rust after painting The above cut and rolled plates were degreased with alkali, washed with water, and then treated with zinc phosphate. After washing with water and drying, apply cationic electrodeposition of epoxy paint to a thickness of 20 μm.
The mold was baked at 160°C for 30 minutes.

This electrodeposition coating was coated with 30 μm thick melamine alkyd paint as an intermediate coat, and baked at 1110°C for 25 minutes.
Next, apply melamine alkyd paint as a top coat to a thickness of 35 μm.
and baked for 25 minutes at 15°C. A cross cut was then made on the surface of each test piece and a salt spray test was conducted for 48 hours in accordance with J I 52371. In addition, a humidity test was conducted at a temperature of 45° C. and a humidity of 95% for 30 days, and surface blisters and filamentous corrosion (or thread rust) were evaluated according to the following criteria (Table 7). Table 8 shows the results.

(Hereinafter in the margins) Table 7 Evaluation criteria (hereinafter in the margins) Table 8 Judgment results The alloy manufactured by the manufacturing method of the present invention is superior to the manufacturing method of the comparative example and the conventional example in both the corrosion resistance of unpainted plates and the corrosion resistance after painting. 5, which is said to have good corrosion resistance among conventional alloys.
It is clear that the corrosion resistance is equivalent to or higher than that of the 182-0 material (symbol N).

Combining the results of Examples below, the material manufactured by the manufacturing method of the present invention has the strength, formability, appearance, and weldability required for aluminum alloy rolled sheets for automobiles due to the exquisite combination of one alloy component and manufacturing process. It is clear that it is a material with a good balance of these properties.

Example 2 A molten alloy having the chemical composition shown in Table 9 was poured between two cooling rolls and continuously cast, resulting in a thickness of 6 + nm.
A plate having a width of 1200 mm was wound up to form a cast coil. Among these cast coils, Alloy 1.2 was treated without homogeneous death TT, and Alloy 3 was treated at 530℃×10hr.
9 which was homogenized and cold rolled to a plate thickness of 3 mm.
The cold rolled plate was intermediately annealed at 350° C. for 2 hours, and then finally cold rolled to a thickness of 1 mm. The final cold rolled plate was heated to 550°C at a heating rate of 30°C/sec, and
Immediately after reaching 50°C (holding time: 0 sec), it was cooled.

The cooling rate was 30°C/sec. The coil thus solution-treated was significantly thermally deformed due to rapid cooling.

Therefore, these coils were straightened to form a flat plate through a tension leveling line. Note that samples were taken from each coil before correction. After correction, samples were taken again from each coil and processed as follows. Alloys 1 and 3 were heated to 230°C at a heating rate of 30°C/sec, and immediately after heating (holding time Qsec) at 30°C/sec.
Continuous annealing was performed by cooling at a cooling rate of . These heat treated strips 1'F were within the scope of the invention shown in FIGS. 1 and 2. Alloy 2 was cut into plates after straightening, and then heated to 110°C at an average heating rate of 8 x 10-3°C/Sec.
Batch annealing was performed in which the temperature was raised to 110°C, held for 2 hours, and then cooled at an average cooling rate of 1.5×10 −2°C/Sec. These heat treatment conditions were also within the scope of the present invention as shown in Section 11':A and FIG. Properties of Alloys 1 and 2 treated as described above: (Table 9 (blank below)) Table (alloy composition) Table 10 Mechanical properties Formability From Table 10, Alloy 1 It can be seen that in both cases, the good elongation and formability expressed by Erichsen's directivity, which were lost due to leveling, were restored to the level before leveling by final annealing.The degree of deformation and flow of these final annealed plates were Lines, Lüders marks, etc. were also evaluated in the same manner as in Example 1, and all were found to be good.

Since Alloys 1 and 2 do not undergo precipitation due to homogenization treatment, solution treatment progresses to a high degree even though the solution treatment was performed continuously for a short period of time. These Alloy 1.2 and the materials with symbols B and C of Example 1 have almost the same composition, and the manufacturing methods are the same except for the casting method, but when comparing them, the continuous cast material is semi-continuous yI It can be seen that the moldability is the same as that of artificial materials, and the strength is improved.

Next, Table 11 shows the results of examining the change in strength due to the process of painting and baking after molding each material of this example in the same manner as in Example 1. It is clear that the strength is improved in the painting process after molding compared to Flcll.

Next, a welding test and a corrosion resistance test were conducted on each material of this example in the same manner as in Example 1. As shown in Table 12, better properties were obtained from all the materials compared to the conventional alloy shown in Example 1.

Table 12 From the above results of Example 2, it is clear that the continuous casting material treated by the method of the present invention is an excellent plate for automobiles. In particular, continuous casting materials that do not go through homogenization have superior strength properties than semi-continuous casting materials, but other properties are the same, so they can be used in a wider range of applications, can be thinner (thinner), and can be used for aluminum 15 plate materials. You can make better use of its features.

In addition, since continuous casting materials can be manufactured without hot rolling, they are more economically advantageous.9 (Effects of the Invention) As is clear from the above examples, the aluminum alloy for forming according to the invention Rolled plates have excellent stretchability and bendability, and have no appearance defects such as Lüders marks or flow lines, and have excellent formability. Furthermore, they have sufficient strength, and are especially suitable for baking coating in the forming process. When performing paint baking, the strength increases during the process and it is possible to finally obtain a baking-painted molded product with extremely high strength. It is ideal for high-strength molded products that are used once.

Furthermore, it has excellent corrosion resistance after painting and TIG and MIG weldability. The rolled aluminum alloy plate of the present invention only contains 51Mg, which is most widely used in ordinary rolled plates, extruded plates, castings, etc., as a main element.
It is easy to use the scrap of other alloys, and conversely, it is also easy to use the scrap of the rolled plate of this invention for other alloys and other uses, and the scrap processing property is good. It is also economically advantageous.

The aluminum alloy rolled sheet manufactured by the method of the present invention is ideal for use as body sheets for automobile bodies as described above, but it can also be used for other applications of molded products that require strength, such as wheels and oil tanks. , automotive parts such as air cleaners, various caps and blinds,
Of course, aluminum λL can also exhibit excellent performance when used in household items, instrument covers, chassis of electrical equipment, etc.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the range of heating temperature, speed, non-cooling temperature and speed in the maximum P-heat treatment after straightening the strain, Figure 2 is a diagram showing the range of holding temperature and time, and Figure 3 is a diagram of the fishbone test piece ( The unit of numbers is mm).

Claims (1)

[Claims] 1. As alloying elements: Si-0.6 to 1.2%, Mg-
0.6-1.1%, as impurities: Fe - less than 0.15%, Cu - less than 0.05%, Mn, Cr, Zr and V
A molten alloy containing less than 0.05% of each of the above, less than 0.05% in total of other impurity elements, and less than 0.10% in total of elements other than Al, Si, Mg, and Fe is cast by semi-continuous casting. , the obtained ingot was heated to 1 to 450 to 590℃.
Heating for 48 hours to perform homogenization treatment that also serves as rolling heating, followed by hot rolling and cold rolling, and holding temperature range 260 immediately after hot rolling or in the middle of cold rolling.
Perform intermediate annealing at ~450°C for a holding time of 48 hours or less,
After that, the rolled plate formed by cold rolling is heated to 450 to 590℃.
Solution treatment is carried out within the temperature range of
Heating at a heating rate within the shaded area shown in Figure 1 to a temperature within the range of 0°C, holding at that temperature for a time within the shaded area shown in Figure 2, then heating as shown in Figure 1. A method for producing an Al-Si-Mg aluminum alloy rolled sheet for forming process, which has excellent formability, corrosion resistance, and weldability, characterized by cooling at a cooling rate within a shaded area. 2. Formability, corrosion resistance, and welding according to claim 1, wherein the solution treatment is performed using a continuous solution hardening device using a coil for a solution treatment time of 0 seconds or more and 5 minutes or less. A method for producing an Al-Si-Mg-based aluminum alloy rolled sheet for forming process with excellent properties. 3. As alloying elements: Si-0.6-1.2%, Mg-
0.6-1.1%, as impurities: Fe - less than 0.15%, Cu - less than 0.05%, Mn, Cr, Zr and V
A molten alloy consisting of less than 0.05% of each of the above, less than 0.05% in total of other impurity elements, and less than 0.10% in total of elements other than Al, Si, Mg, and Fe is cast by continuous casting, The resulting coiled ingot was then cold-rolled to form a rolled plate, which was then solution-treated at a temperature range of 450 to 590°C, quenched at a cooling rate of 5°C/sec or more, and then subjected to strain straightening. The product is then heated to a temperature within the range of 60 to 360°C at a heating rate within the shaded area shown in Figure 1, held at that temperature for a time within the shaded area shown in Figure 2, and then A method for manufacturing an Al-Si-Mg aluminum alloy rolled sheet for forming process, which is characterized by cooling at a cooling rate within the shaded area shown in FIG. 1 and having excellent formability, corrosion resistance, and weldability. 4. Holding temperature range 260-45 in the middle of cold rolling
4. The aluminum alloy having excellent formability, corrosion resistance, and weldability according to claim 3, wherein intermediate annealing is performed at 0° C. for a holding time of 48 hours or less, and the solution treatment is performed after subsequent cold rolling. A method for producing a Si-Mg-based rolled aluminum alloy plate for forming processing. 5. Formability and corrosion resistance according to claim 3 or 4, wherein the solution treatment is performed using a continuous solution hardening device using a coil for a solution treatment time of 0 seconds or more and 5 minutes or less. and a method for manufacturing an Al-Si-Mg-based aluminum alloy rolled sheet for forming process with excellent weldability. 6. During continuous casting and cold rolling, the coiled ingot is
The Al-Si-Mg molding having excellent moldability, corrosion resistance, and weldability according to claim 3, 4, or 5, characterized in that it is homogenized by heating in a temperature range of ~590°C for 1 to 48 hours. A method for producing a rolled aluminum alloy plate for processing.