JPH0480109B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a rolled aluminum alloy plate for forming with good corrosion resistance and weldability, and a method for manufacturing the same, and particularly for applications where strength is required and where baking is applied, such as automobiles. The present invention relates to a rolled aluminum alloy plate for forming processing suitable for automobile bodies, etc., and a method for manufacturing the same. [Prior Art] In the past, cold-rolled steel plates were often used for the body sheets of automobile bodies, but recently, due to the demand for lighter vehicle bodies, consideration has been given to using rolled aluminum alloy plates. . Since body sheets for automobile bodies are used after being press-formed, they are required to have excellent molding properties, especially excellent elongation and extrusion properties, and no reuders marks during the molding process. It is also essential to have high strength.
In particular, since baking is applied, high strength is required after baking. By the way, there have been various types of aluminum alloy plates used for forming products that require strength, but the main ones can be classified as follows depending on the alloy composition system. (a) O material of 5052 alloy (Mg 2.2 to 2.8%, Cr 0.15 to 0.35% balance Al and unavoidable impurities), which is a non-heat treatment type Al-Mg alloy, or 5182 alloy (Mn 0.20 to 0.50%) , Mg1.0~5.0%, balance Al
and unavoidable impurities). (b) 2036 alloy, which is a heat-treatable Al-Cu alloy (Cu2.2-3.0%, Mn0.1-0.4%, Mg0.3-0.6%,
(Remaining Al and unavoidable impurities) T4 treated material. (c) T4 treated material of heat-treated Al-Mg-Zn-Cu alloy. Examples of this type of aluminum alloy include the alloy of JP-A-52-141409, the alloy of JP-A-53-141409,
There are alloys such as No. 103914 and JP-A No. 57-98648. Also, Al−4.5Mg−0.38Cu−1.46Zn− introduced in Nikkei New Material, 1986.4−7.No.8, pages 63−72, especially page 64.
0.18Fe−0.09Si is also available. (d) 6009 alloy, which is a heat-treatable Al-Mg-Si alloy (Mg0.4-0.8%, Si0.6-1.0%, Cu0.15-0.6%,
Mn0.2~0.8%, balance Al and unavoidable impurities)
T4 treated material and 6010 alloy (Mg0.6~1.0%,
Si0.8~1.2%, Cu0.15~0.6%, Mn0.2~0.8%,
(Remaining Al and unavoidable impurities) T4 treated material.
According to Japanese Patent Publication No. 59-39499 proposing these alloys, 0.4~1.2% Si, 0.4~1.1% Mg, 0.05~
0.35% Fe, 0.1~0.6% Cu, plus 0.2~0.8
T4 or T6 with a composition containing at least one of %Mn, 0.1 to 0.3% Cr, and 0.05 to 0.15% Zr
A treated material is disclosed. Furthermore, (A) 1 proposed in Special Publication No. 61-15148
%Si, 0.6%Mg, (B) 1.8%Si, 0.6%Mg, (C) 1.8%
It has a Si, Mg composition surrounded by four points: Si, 0.2%Mg, (D) 1.2%Si, 0.6%Mg, and 0.3% or less Cr,
AC120 standardized material containing Mn, Zr, or/and Ti. However, with these conventional aluminum alloys, it has been difficult to fully satisfy all of the above-mentioned characteristics required for body sheets of automobile bodies. In other words, alloy (a) has insufficient strength;
Furthermore, there was a problem in that reuders marks were likely to occur during the molding process, and furthermore, there was a problem in that the strength was reduced due to the paint baking process. Furthermore, the alloy (b) had problems of poor formability and reduced strength due to the paint baking process. Furthermore, the alloy (c) had insufficient formability, especially bendability, and also had the problem of reduced strength during the paint baking process. The alloy (d) has features such as being less likely to generate Lyuders' marks and having the same strength as cold-rolled steel sheets due to its bake hardenability, but its elongation, which is a measure of formability, is significantly lower than that of cold-rolled steel sheets. It is known. As mentioned above, conventionally, aluminum alloys
The properties required for automobile body sheets include excellent moldability, especially excellent elongation and stretch moldability, and no reuders marks, and high strength, especially after paint baking. Research and development has been carried out in order to satisfy all of the requirements for excellent corrosion resistance and weldability. [Problems to be solved by the invention] Al-Si-Mg alloys to which the present invention belongs are known, which satisfy the above requirements to a considerable extent, but they are not commonly used in body sheets for automobiles. The performance requirements for aluminum alloy rolled sheets, which are disadvantageous in terms of price than conventional steel sheets, 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 automobile body sheets, the conventional opinion was that unless there were defects in the coating, the corrosion resistance of the aluminum alloy itself was superior to that of steel sheets, so there was no problem (Nikkei New Materials cited above). )or,
Corrosion resistance against blistering defects in chrome-plated films
Experiments investigated in the CASS test
39499) etc. However, recently, 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 are required. i.e.
In addition to corrosion resistance and pit resistance related to the properties of the Al alloy itself, it is also required that the coating film does not peel off (blister) or cause filiform corrosion after baking. 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 automobile body seats is done by spot welding.
Depending on the location, so-called arc welding using MIG or TIG welding is performed. Since relatively thin plates with a thickness of 2.0 mm or less are generally arc welded, welding is generally difficult, so rolled plates with good weldability are required. This invention was made against the background of the above-mentioned circumstances, and has excellent molding processability, especially elongation and stretchability, no generation of reuders marks during molding, and high strength, especially after molding. An aluminum alloy that does not reduce its strength during the paint baking process, but rather increases its strength through the paint baking process after forming, making it possible to obtain molded products with high strength, and with improved corrosion resistance and weldability. The object of the present invention is to provide a rolled plate and a method for manufacturing the same. [Means for solving the problem] The first aspect of the present invention is that Si exceeds 1.2% and is 1.8% or less,
Mg over 0.6% and 1.1% or less, and Fe 0.05% to 0.5%
Furthermore, if necessary, Mn 0.6% or less,
Contains one or more of the three components consisting of Cr0.3% or less and Zr0.3% or less, with the remainder essentially consisting of unavoidable impurities and Al, and has good moldability and corrosion resistance. and Al-Si-Mg with excellent weldability.
It is an alloy rolled plate for system forming processing. The second aspect of the present invention is to cast a molten alloy having the above composition by semi-continuous casting or continuous casting, and roll the obtained ingot to produce a rolled plate at a temperature of 450°C to 590°C.
Al-Si-Mg aluminum alloy rolled sheet for forming process, which has excellent formability, corrosion resistance, and weldability, and is characterized by solution treatment in the temperature range of ℃ and quenching at a cooling rate of 5℃/sec or more. It is in the manufacturing method. The third aspect of the present invention is that after the above-mentioned solution treatment, the strain is straightened and 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. The material has excellent formability, corrosion resistance, and weldability, and is maintained at a temperature within the shaded area shown in Figure 2 for a period of time, and then cooled at a cooling rate within the shaded area shown in Figure 1. Al−Si−Mg
A method of manufacturing an aluminum alloy rolled plate for system forming processing. First, the reason for limiting the composition of the present invention will be explained. Si: Si is partially present in the Al alloy as metallic Si particles and improves formability, particularly elongation properties.
In addition, some other Si coexists with Mg to produce Mg ₂ Si, which contributes to improving strength through precipitation hardening. In particular, from the Mg ₂ Si stoichiometry that produces Mg ₂ Si
It is important for strength improvement to have a sufficient excess of Si and to generate metal Si particles. Although the mechanism is unknown, Si also improves the weldability of arc welding such as MIG and TIG. If the Si content is less than 1.2%, the effects of improving strength, formability, and weldability will be insufficient, and if the content exceeds 1.8%, it will be used as scrap when melting low Si-aluminum alloys. There are limitations to using this alloy. Mg: As already mentioned, Mg coexists with Si to generate Mg ₂ Si and impart strength. Mg 0.6%
If it is less than 1.1%, the strength is insufficient, while if it exceeds 1.1%, the elongation decreases, so the Mg content range is 0.6%.
~1.1%. Fe: Fe contributes to improving strength by making crystal grains finer, but if it is less than 0.05%, crystal grains become coarser,
On the other hand, if it exceeds 0.4%, formability will decrease, so Fe
The content was within the range of 0.05 to 0.5%. Mn, Cr, Zr: All of these elements refine the recrystallized grains, stabilize the structure, and
Improves formability. Mn less than 0.05%, Cr
If the Zr content is less than 0.05%, the above effects cannot be obtained sufficiently, so in order to actively utilize the effects of these elements, it is necessary to add 0.05% or more. On the other hand, if Mn exceeds 0.6%, formability decreases and Cr
If Zr exceeds 0.3% and Zr exceeds 0.3%, giant intermetallic compounds are formed and elongation decreases, so Mn was set at 0.6% or less, Cr at 0.05-0.3% or less, and Zr at 0.3% or less. These Mn, Cr, and Zr are effective elements for grain refinement, but the heating rate during solution treatment is 5℃/
sec or more, fine crystal grains can be formed without necessarily adding these elements. The remainder of each of the above components may be Al and inevitable impurities. Cu in impurities significantly deteriorates the corrosion resistance of the material and also impairs weldability.
Cu is limited to less than 0.1%. In addition, in ordinary aluminum alloys, Ti or Ti and B are added to refine the crystal grains of the ingot.
The rolled aluminum alloy plate of the present invention may also contain a trace amount of Ti or Ti and B as the remainder of Al, alloy components, and impurities. However, when adding Ti, the effect cannot be obtained if it is less than 0.01%, and 0.15
% or more, primary TiAl ₃ crystallizes and impairs formation properties, so Ti is preferably in the range of 0.01 to 0.15%. Also, when B is added together with Ti,
If it is less than 1 ppm, there is no effect, and if it exceeds 500 ppm, coarse particles of TiB ₂ will be mixed in, impairing the moldability, so B is preferably in the range of 1 to 500 ppm. Next, a method for manufacturing an aluminum alloy rolled plate of the present invention will be explained. In order to fully exhibit the characteristics of the above alloy composition of the present invention, an aluminum alloy rolled plate is solution-treated at 450°C to 590°C, and
It is necessary to cool at a cooling rate of ℃/sec or higher. Through this solution treatment, solid solution Mg and Si are obtained in the amount necessary to obtain predetermined strength and formability. If the temperature is less than 450°C, solution treatment will be insufficient and sufficient strength will not be obtained after cooling and after 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 such as intergranular corrosion will deteriorate. Therefore, 5℃/
A quenching speed of sec or higher is required. Furthermore, in order to further improve the characteristics of the above-mentioned alloy composition, it is desirable to use a manufacturing method according to the following methods and conditions. A molten metal having the above alloy composition is semi-continuously cast into an ingot having a rectangular cross section. The casting speed is
There is no particular requirement as long as a rectangular ingot can be cast, but usually
It is cast in the range of 25mm/min to 250mm/min.
This ingot was heated to 450-590℃ prior to hot rolling.
Heated for ~48 hours. In order to eliminate the non-uniformity of the ingot and improve the formability, if the heating temperature is less than 450℃ or the heating time is less than 1 hour, homogenization will be insufficient, so the heating temperature should be 590℃ or less. If the heating time exceeds 48 hours, local melting will occur, and if the heating time exceeds 48 hours, the economical efficiency will decrease and the homogenization effect will be saturated. Note that instead of a large semi-continuously cast ingot, a continuously cast plate obtained by continuously supplying molten metal between two rolls may be used. In this case, there is no particular restriction on the casting speed, and cold rolling is usually performed without hot rolling. ℃×1〜
It is even more effective if preheated for 48 hours. The aluminum alloy plate hot-rolled as described above is then cold-rolled to a thickness of 3.0 to 0.5 mm. If intermediate annealing is performed between cold rolling or between hot rolling and cold rolling, the recrystallization effect will further improve the properties of the aluminum alloy sheet, especially its strength and formability. There is. In other words, if coarse grains are generated during hot rolling, if the hot rolled sheet is cold rolled without intermediate annealing and subjected to solution treatment, these coarse grains will form a band extending in the rolling direction. A structure is formed, and during the molding process, undulations called ridging or flow lines occur, deteriorating the appearance of the molded product. Therefore,
Once recrystallization is caused by intermediate annealing, the influence of coarse grains produced during hot rolling can be eliminated. Here, if the intermediate annealing temperature is less than 280°C, recrystallization does not occur, and if the temperature exceeds 450°C, coarsening of crystal grains tends to occur. Further, intermediate annealing for which the holding time exceeds 48 hours is not economical. Considering the mass productivity, etc. of the above solution treatment,
Preferably, the coil is subjected to continuous solution hardening treatment. The holding time may be 0 (cooling at the same time as the predetermined temperature is reached), but is usually preferably 10 seconds or more. When continuously solution hardening the 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 higher is usually obtained, so crystal grains are refined and formability is improved. Solution treatment was originally intended to sufficiently dissolve alloying elements such as Mg and Si that contribute to strengthening into a solid solution. Therefore, in order to obtain the necessary strength, it is necessary to re-dissolve the alloying elements that contribute to strengthening in the amount necessary to obtain the strength. dissolve,
A so-called complete solution treatment is performed. However, especially when used for molding automobiles, depending on the part of the vehicle body, it may be necessary to emphasize moldability over strength. In this case, increase the Mg content and Si content,
It is also possible to perform so-called incomplete solution treatment, in which Mg and Si are redissolved in the amount necessary for strengthening during solution treatment. Specifically, the time or temperature during solution treatment may be shortened or lowered. In particular, when a continuous solution hardening device is used, it is possible to shorten the holding time, thereby increasing the line speed during continuous solution treatment, resulting in economical advantages. When incomplete solution treatment is performed, if the state of existence of Mg and Si before solution treatment changes, the amounts of Mg and Si that are re-dissolved will vary accordingly, and the mechanical properties will change. Therefore, before solution treatment
The key point is to keep the existing states of Mg and Si constant. In order to control the presence of Mg and Si before solution treatment, it is necessary to strictly control the heating conditions and hot rolling conditions before hot rolling, but if intermediate annealing is included in the manufacturing process, , more preferred. When subjected to intermediate annealing at the temperature described above, the existing states of Mg and Si determined by the thermal history before intermediate annealing are stabilized and constant, and as a result, the regeneration of Mg and Si due to incomplete solution treatment is The amount of solid solution is stabilized, making it easier to stabilize mechanical performance. Note that after the solution treatment, the aluminum alloy rolled plate is strain-corrected. After that, surface cleaning, chemical conversion treatment,
Performs molding, welding, painting, baking hardening, etc. Rapid heating during solution treatment and rapid cooling during quenching cause rapid thermal expansion and contraction of the rolled plate, which deforms the rolled plate and causes strain. Therefore, in order to remove this distortion, distortion correction is performed after solution treatment and quenching. This distortion correction may be performed by leveling, tension leveling, skin pass, or stretching, and in any of these methods, distortion is removed by applying a slight cold work. The degree of processing in the strain straightening process varies depending on the degree of strain after solution treatment and quenching, but usually by including the strain straightening process, the yield strength can be reduced to 1.
Kg/ ^mm2 or more increases, and formability is determined by Erichsen value.
Decreased by 0.2mm or more. The rolled plate whose forming performance has been degraded due to the strain straightening process is then subjected to a final heat treatment in which the sheet is heated to a temperature in the range of 60 to 360°C and held or immediately cooled. This heat treatment is carried out in the shaded area of FIG.
The temperature is increased at a heating rate within the area surrounded by a straight line or curved line connecting the The temperature is maintained for a period of time within the range enclosed by the heating temperature, and the temperature is further cooled at a cooling rate within the shaded area in FIG. 1 corresponding to the heating holding temperature. Here, the temperatures and heating/cooling rates at each point A to E in FIG. 1 are as follows. A: 60℃, 4×10 ^-3 ℃/sec B: 140℃, 4×10 ^-3 ℃/sec C: 360℃, 3×10℃/sec D: 230℃, 4×10 ³ ℃/sec E : 60°C, 4×10 ³ °C/sec The temperature and time at each point a to d in FIG. 2 are as follows. a: 200℃, 0sec b: 360℃, 0sec c: 130℃, 10 ⁵ sec d: 60℃, 10 ⁵ sec In this way, the range of heating rate, holding time, and cooling time is determined for the final heat treatment after straightening the strain. Explain why. Since the Al-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 the strength after molding or the strength after T6 treatment may decrease due to over-aging. 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 AB in Figure 1, there is no problem with the material's performance, but if it is heated more slowly than this, it will take an extremely long time to raise the temperature, which will reduce productivity and reduce economic efficiency. It will no longer be. Therefore, the heating rate was set above the straight line AB. In the region below the curve BC in FIG. 1 where the heating rate is slow, age hardening occurs during heating and temperature rise, and although the strength increases, the formability decreases. So the curve BC
This is the upper area. 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 straight line DC
This is the lower area. The area above the straight line DE is a heating rate that substantially exceeds the heating rate due to oil bath injection,
Although heating rates higher than this are effective, they are not practical and meaningless, so the region below the straight line DE was chosen. On the left side of the straight line EA, that is, when the heating temperature is low (less than 60℃), the processing strain due to strain correction cannot be completely removed regardless of the heating rate, so the straight line EA
The left side region of was excluded. From the above, the range of heating rate varies depending on the heating holding temperature, but points A, B, C, D, and E in Figure 1
It is necessary to place it within the shaded area surrounded by . (Holding temperature/time) Regarding the straight line ab in Figure 2, the holding temperature
At 200 to 360°C, processing strain can be removed even if cooling is started immediately after reaching that temperature range, that is, even if the holding time is 0 seconds. Therefore, the holding temperature is 200
In the temperature range of ~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.
Moldability deteriorates. In addition, especially in high temperature ranges, overaging occurs, which reduces formability and makes it impossible to obtain the desired strength by baking or T6 treatment after forming. Therefore, it needs to be the lower left area of curve bc. Above the straight line CD, processing distortion can be removed and formability can be restored, but the holding time exceeds 24 hours, making it economically meaningless.
It was placed below the CD. In the area below and to the left of the curve da, the heat necessary to remove processing strain is not applied, and recovery of formability is not observed. Therefore, it needs to be the upper right area of the curve da. From the above, the heating holding time differs depending on the heating holding temperature, but ultimately it needs to be within the shaded area surrounded by points ABCD in FIG. 2. (Cooling rate) The cooling rate is the same as the heating rate in Figure 1.
Must be within the shaded area surrounded by ABCDE. In the region below straight line AB, there is no problem with the performance of the material, but slow cooling beyond this range is not economical because cooling takes a significantly long time. Therefore, it was set as the area above straight line AB. In the region below curve BC where the cooling rate is slow,
Aging precipitation occurs during cooling, reducing formability, and over-aging may cause baked-on coating or damage after forming.
It becomes impossible to obtain the specified strength with T6 treatment.
Therefore, it was set as the area above curve BC. If the cooling rate is above the straight line DC, the cooling rate will be too high, causing strain deformation in the material, and the effect of strain correction before the final heat treatment will be lost. Therefore, it was set as the area below the straight line DC. In the region above the straight line DE, the cooling rate substantially exceeds water cooling, which is practically meaningless, so the cooling rate was set below the straight line DE. To the left of straight line EA, machining strain cannot be removed regardless of the cooling rate. therefore straight line
This is the area to the right of the EA. Therefore, like the heating rate, the cooling rate also varies depending on the heating holding temperature, but the
The shaded area is surrounded by ABCDE. If the final heat treatment under the above conditions is performed after the strain straightening process, the processing strain introduced in the strain straightening process will be removed, and the formability, especially the stretchability, which has decreased due to the strain correction will be restored, and the solution treatment Good formability in T4 temper state obtained by quenching,
In particular, it can be returned to a state where it has overhanging properties. In addition, in this final heat treatment, appropriate conditions are set so that age hardening and overaging do not occur, so there is no deterioration in formability due to these, and there is no problem with post-forming baking painting or T6 treatment. The required strength can be obtained. Furthermore, since the conditions for the final heat treatment are determined 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. [Function] Typical properties of the aluminum alloy rolled sheet of the present invention in the artificially aged (T4) state after solution treatment are as follows. Mechanical properties: proof stress (σ _0.2 ) - 15Kg/mm ² or more, tensile strength - (σ _B ) about 30Kg/mm ² or more, and elongation about 29% or more. Formability: Erichsen value - equivalent or higher than 6010 alloy, minimum bending (180°) - equivalent or higher than 6010 alloy, limiting drawing ratio (LDR) - equivalent to conventional aluminum alloy plate for forming processing, Lyuders mark - none. Bake hardenability: After adding 10% or less cold working assuming molding, 175℃ assuming paint baking.
When heat treated for 1 hour, the yield strength increases by more than 1Kg/mm ² , up to about 2Kg/mm ² . Equivalent to or better than 6010 alloy. Corrosion resistance: The corrosion resistance of the painted plate after the usual 3-coat coating for automobile bodies consisting of electrodeposited undercoat, intermediate coat, and topcoat is superior to 6010 alloy and equivalent to 5182 alloy. Weldability: Weldability is improved compared to conventional TIG or MIG welding, such as 6009 alloy thin plates. The rolled aluminum alloy sheet for forming according to the present invention having the above characteristics has a better balance of properties and is significantly more suitable as a body sheet material for automobile bodies than conventional rolled sheets. Hereinafter, the present invention will be explained in more detail with reference to Examples. [Example] Example 1 Molten aluminum alloy having the composition shown in Table 1 was
Casting speed 60mm/ for a slab with a cross section of 500×1000mm
Semi-continuous casting was performed at min.

[Table] Subsequently, after performing the homogenization treatment shown in Table 2, hot rolling was performed to a plate thickness of 4 mm, cold rolling to a plate thickness of 1 mm, and finally the final heat treatment shown in Table 2 was performed.

[Table] It was.
Table 3 shows the mechanical properties and moldability after the final heat treatment shown in Table 2 and after further standing at room temperature for 7 days. Note that proof stress and tensile strength are expressed in Kg/mm ² , elongation is expressed in %, and Erichsen value and minimum bending are expressed in mm. In addition, in order to examine the change in strength due to the paint baking process after forming, the plate after room temperature aging was subjected to 5% cold working or 10% cold working, which corresponds to forming process, and then to the plate, which corresponds to the paint baking process. 175℃×
One hour of heat treatment without cold working (0% cold worked material), and 5% cold worked material,
This was carried out on 10% cold-worked materials, and the strength at each stage was investigated. The results are shown in Table 4.

【table】

[Table] As is clear from Table 3, all of the alloys 1 to 3 of the present invention have excellent stretchability and bendability, and there is no occurrence of Lyuders' marks, indicating that they have excellent moldability. Furthermore, from Table 4, it is clear that the strength of the alloy of the present invention is improved in the paint baking process after forming, and a baked painted molded product having a high tensile strength of 33 Kg/mm ² or more is finally obtained. In addition, a fishbone crack test piece was TIG welded and the cracking rate was investigated. The TIG welding conditions were: TIG automatic welding (no overlay); current 60A; feed rate 25cm/min; tungsten electrode 2.4mmφ; Ar airflow; arc length 3mm. The dimensions of the fishbone test piece are shown in Figure 3.

【table】

[Table] Here, the cracking rate is expressed by the following formula. Cracking rate = bead length with cracks/total weld bead length x
100 It can be seen that the invention alloy has excellent weldability. Summarizing the above results, we find the following. Comparative Example 5, which has a composition of low Si and high Mg, has strength, but has poor formability and poor weldability. high
Comparative Cu alloys 4 and 5 have poor weldability. Conventional examples 7 to 10 are representative materials for molding. The materials of the invention are superior to these in terms of overall properties. That is, the material of the present invention is 2036 (No.
8) in terms of workability, elongation, bake hardenability, and weldability, and Al-Mg-Zn-Cu (No. 10) in terms of bake hardenability and weldability. (No. 9), it is superior in terms of elongation and weldability. Example 2 In alloys 1, 2, and 3 in Table 1, Example 1
A hot rolled plate with a thickness of 4 mm was obtained in the same manner as (however, the solution treatment will be described later). It was further cold rolled to a thickness of 3 mm, intermediate annealed at 350°C for 2 hours at this thickness, cooled at an average rate of 30°C/Hr, and then cold rolled to a thickness of 1 mm and wound into a coil. For Alloy 3, a cold rolled coil was manufactured by the same method except that intermediate annealing was omitted for comparison. These coils were heated using a continuous solution quenching furnace, held at a temperature increase rate of 30°C/sec, 560°C for the time shown in Table 5, and quenched at a quenching rate of 30°C/sec. Aging was performed for two weeks at room temperature (T4 state), and then the same test as in Example 1 was performed. A 100φ ball head extension test was conducted, the appearance was observed, and the moldability was judged based on the following criteria.
The results are shown in Table 6. ○: No flow lines at all △: Flow lines observed (cannot be used for applications with severe appearance) ×: Strong flow lines The results are shown in Table 6.

[Table] 175, which corresponds to paint baking, on an alloy plate in T4 condition
Aging treatment (no stretching) was performed at ℃×1 hour.

[Table] From the above results (Table 6) for Alloy 3 of this example, even in manufacturing using a continuous annealing furnace with high productivity,
It has been found to have excellent performance and, by incorporating an intermediate annealing into the manufacturing process, improves the flow line and is more suitable for applications with demanding appearance requirements such as automobiles. The process applied to Alloys 1 and 2 uses a relatively short solution treatment to increase the amount of Mg required for strengthening.
This is an example in which Mg and Si are redissolved in solid solution, but the remaining Mg and Si remain as precipitates, and this is a process with extremely high productivity. In this alloy, Example 1
Although the strength is slightly inferior to that of the complete solution annealing treatment shown in Fig. 1, it is possible to obtain a yield strength that sufficiently exceeds the strength required to replace automotive steel sheets, especially the yield strength level of 12 kg/mm ² or more. There is. Moreover, it has excellent moldability (flow line). Moreover, since the material of the present invention has bake hardenability,
Further reinforcement is possible. In this way, by effectively utilizing incomplete solution treatment, we can improve strength, formability, and weldability.
It becomes possible to obtain materials with excellent corrosion resistance. Example 3 Present invention alloys 1, 2, and 3, comparative example alloys 4, 5, and 6, and conventional example alloys 7, 8, and
A rolled plate (thickness 1mm) corresponding to 9 and 10 is 70mm×
Cut to 150mm. Experiment 1: Corrosion resistance test of unpainted plate The surface of the rolled plate was coated with a 10% NaOH aqueous solution (50℃)
After degreasing for 1 minute with
The smuts were removed and washed using aqueous HNO ₃ solution. About the rolled plate treated in this way
A salt spray test was conducted according to JISZ2371. Spraying time is 1000 hours. Evaluation of corrosion resistance was based on visual observation based on the following criteria. ◎: No pits at all ○: Several pits △: Considerable pits ×: Pitts all over

[Table] Experiment 2: Corrosion of blisters and thread rust after painting The above-mentioned cut and rolled plate was degreased with alkali, washed with water, and then treated with zinc phosphate. After washing with water and drying, cationic electrodeposition of epoxy paint was applied to a thickness of 20μm, and then 160μm thick.
Baking was carried out at ℃ for 30 minutes. This electrodeposition coating was coated with melamine alkyd paint to a thickness of 30 μm as an intermediate coat and baked at 140°C for 25 minutes.Next, a melamine alkyd paint was coated to a thickness of 35 μm as a top coat and baked at 145°C for 25 minutes. . Next, a cross cut was made on the surface of each test piece, and a salt spray test was conducted in accordance with JIS2371.
It lasted 48 hours. Next, a humidity test was conducted at a temperature of 45°C and a humidity of 95% for 30 days, and the results of evaluating surface blisters and filamentous corrosion (or thread rust) using the following criteria are shown (Table 10).

【table】

【table】

[Table] Example 4 Inventive alloy 1 was treated in the same manner as in Example 2, including intermediate annealing and continuous solution quenching. The intermediate annealing conditions were a temperature increase rate of 30°C/sec, a quenching rate of 30°C/sec, an annealing temperature of 560°C, and no holding time. Also, aging at room temperature for 2 weeks after quenching (T4)
I did this. The strain on the solution-treated coil was corrected by tension leveling, and the flatness of the plate was corrected. Thereafter, final annealing was performed under the conditions shown in Table 11.

[Table] Table 12 shows the mechanical properties, Erichsen values, and deformation of the plate before and after leveling and after final annealing.

【table】

〔Effect of the invention〕

As is clear from the above examples, the aluminum alloy rolled sheet for forming of the present invention has excellent formability, such as excellent stretchability and bendability, and no generation of reuders marks, and also has high strength. In particular, when baking paint is applied after forming, the strength increases during the baking process and a baking-painted molded product with extremely high strength can be obtained. As such, it is ideal for use in high-strength molded products that are welded and baked. Furthermore, it has excellent corrosion resistance after painting and TIG/MIG weldability. The aluminum alloy rolled sheet of this invention only contains Si and Mg, which are most widely used in ordinary rolled sheets, extruded materials, castings, etc., as main elements, so it is not possible to use scraps of other alloys. It is easy to use, and conversely, it is also easy to use the scrap of the rolled plate of the present invention for other alloys and other uses, and it has good scrap processing properties and is economically advantageous. The aluminum alloy rolled sheet of the present invention is ideal for body sheets of automobile bodies as mentioned above, but it can also be used for other applications where strength is required, such as wheels, oil tanks, air cleaners, etc. Of course, it can also exhibit excellent performance when used in automobile parts, various caps and blinds, aluminum cans, household appliances, instrument covers, chassis for electrical equipment, etc.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the range of heating temperature/rate and cooling temperature/rate in the final heat treatment after straightening distortion.
The figure shows the range of holding temperature and time, and Figure 3 is a diagram of the body bone test piece (numbers are in mm).

Claims (1)

[Claims] 1. Si over 1.2% and 1.8% or less, Mg over 0.6% and 1.1
% or less, and 0.05% to 0.5% Fe, with the remainder being essentially unavoidable impurities (however, Cu is less than 0.1%)
An Al-Si-Mg aluminum alloy rolled sheet for forming process, which has a composition consisting of and Al, and has excellent formability, corrosion resistance, and weldability. 2 Si over 1.2% and 1.8% or less, Mg over 0.6% and 1.1
% or less, Fe0.05% to 0.5%, and Mn0.6% or less,
A composition containing one or more of the three components consisting of Cr 0.3% or less and Zr 0.3% or less, with the remainder essentially consisting of unavoidable impurities (however, Cu is less than 0.1%) and Al. An Al-Si-Mg aluminum alloy rolled sheet for forming process, which has excellent formability, corrosion resistance, and weldability. 3 Si over 1.2% and 1.8% or less, Mg over 0.6% and 1.1
% or less, and Fe0.05% to 0.5%, and if necessary, one or more of the three components of Mn0.6% or less, Cr0.3% or less, and Zr0.3% or less. A molten alloy having a composition in which the remainder substantially consists of unavoidable impurities (however, Cu is less than 0.1%) and Al is cast by semi-continuous casting or continuous casting, and the obtained ingot is rolled. The obtained rolled plate is 450
Solution treatment in the temperature range from ℃ to 590℃, 5℃/sec
Al-Si with excellent formability, corrosion resistance and weldability, characterized by being quenched at a cooling rate of
- A method for manufacturing an aluminum alloy rolled plate for Mg-based forming processing. 4. A semi-continuously cast ingot is heated within a temperature range of 450°C to 590°C for 1 to 48 hours to perform homogenization treatment that also serves as rolling heating, and then hot rolling is performed. The method described in Scope No. 3. 5 Obtain a coiled ingot of the above alloy by continuous casting, and heat it at a temperature of 1 to 48°C within a temperature range of 300°C to 590°C.
4. A method according to claim 3, characterized in that homogenization is carried out by heating for a period of time, and then cold rolling is carried out. 6 A patent characterized in that intermediate annealing is performed at a holding temperature range of 260°C to 450°C for a holding time of 48 hours or less immediately after hot rolling or in the middle of cold rolling, and the solution treatment is performed after the subsequent cold rolling. The method according to any one of claims 3 to 5. 7. The solution treatment is carried out in a continuous solution heat treatment device using a coil, and the coil is cooled as soon as the temperature of the coil reaches the solution treatment temperature range, or the coil is heated within the solution treatment temperature range for 5 minutes or less. The method according to any one of claims 3 to 6, characterized in that the method is carried out by holding. 8 Si over 1.2% and 1.8% or less, Mg over 0.6% and 1.1
% or less, and Fe0.05% to 0.5%, and if necessary, one or more of the three components of Mn0.6% or less, Cr0.3% or less, and Zr0.3% or less. A molten alloy having a composition in which the remainder substantially consists of unavoidable impurities (however, Cu is less than 0.1%) and Al is cast by semi-continuous casting or continuous casting, and the obtained ingot is rolled. The obtained rolled plate is 450
Solution treatment in the temperature range from ℃ to 590℃, 5℃/sec
After quenching at the above cooling rate, and then performing strain correction, heating to a temperature in the range of 60°C to 360°C at a heating rate within the shaded area shown in Figure 1,
After that, the temperature is maintained within the shaded area shown in FIG. 2, and then cooled at the cooling rate within the shaded area shown in FIG. A method for producing a Si-Mg-based aluminum alloy rolled plate for forming processing. 9 A patent claim characterized in that a semi-continuously cast ingot is heated within a temperature range of 450°C to 590°C for 1 to 48 hours to perform homogenization treatment that also serves as rolling heating, and then hot rolling is performed. The method described in Scope Item 8. 10 Obtain a coiled ingot of the above alloy by continuous casting, and heat it at a temperature of 1 to 48°C within a temperature range of 300°C to 590°C.
9. The method according to claim 8, characterized in that homogenization is performed by heating for a period of time, and then hot rolling is performed. 11 Immediately after hot rolling or in the middle of cold rolling, intermediate annealing is performed at a holding temperature range of 260°C to 450°C for a holding time of 48 hours or less, and the solution treatment is performed after the subsequent cold rolling. The method according to any one of claims 8 to 10. 12 The solution treatment is carried out in a continuous solution treatment hardening device using a coil, and the coil is cooled as soon as the temperature of the coil reaches the solution treatment temperature range, or the coil is heated within the solution treatment temperature range for 5 minutes or less. 12. The method according to any one of claims 8 to 11, characterized in that the method is carried out by holding.