JP2001262265A - Hot rolling stock of high formability aluminum alloy sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot rolling stock suitable for obtaining an Al-Mg-Si alloy excellent in press formability (particularly, bulging formability). SOLUTION: In this hot rolling stock of an Al-Mg-Si aluminum alloy sheet, in the stage before cold rolling or before final solution treatment, the density of precipitated particles (e.g. Mg2Si as a precipitated compound of the main addition elements such as Mg and Si, Si simple substance, or the like) having the average particle size of >=0.5 μm is <=0.2 pieces/μm3. Moreover, the content of Mg in the aluminum alloy sheet is preferably controlled to 0.3 to 1.5%, and Si to 0.3 to 1.5%, and it is recommended that one or more kinds selected from the group consisting of Mn, Cr, Zr, V and Ti are contained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-rolled material (intermediate material) of a highly formable aluminum alloy sheet, and more particularly to J.
An Al-Mg-Si alloy plate belonging to IS 6000 series, which has excellent press formability, which is a material suitable for an engine hood, a trunk hood, and the like of an automobile requiring good stretch formability and bending workability. The present invention relates to a hot-rolled material of an Mg-Si alloy sheet.

[0002]

2. Description of the Related Art From the viewpoint of effective use of resources and economic efficiency,
There is a high demand for reducing the weight of vehicles for the purpose of improving fuel efficiency. For example, aluminum alloys are being applied to automobile outer panel materials and the like.

[0003] In an automotive panel material, an Al-Mg alloy (5000) was initially used as an Al alloy sheet instead of a cold-rolled steel sheet.
Alloys) have been mainly used, but there are problems such as the occurrence of stretcher strain marks at the time of press molding. Therefore, there is no problem of the stretcher strain marks, and the proof stress increases during the baking process. Al-M with excellent bake hardenability that can achieve strength
Attention has been paid to g-Si alloys (6000 alloys), for example, AA6009 and AA6010, and JP-A-5-2954.
Application of the Al alloy disclosed in Japanese Patent No. 75 is being studied.

[0004] However, these 6000 series alloys have the above-mentioned 5
It is necessary to improve the press formability since the press formability is inferior to that of the 000 series alloy.
Attempts have been made to add a third or fourth alloying element other than i, or to refine the crystal grain size or the crystals / precipitates together with the addition of the alloying element. However, the press-formability of the Al-Mg-Si-based aluminum alloy sheet obtained by these improved techniques is limited, and is not always sufficient for practical use.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is suitable for obtaining an Al-Mg-Si alloy excellent in press formability (especially stretch formability). The purpose is to provide a hot-rolled material.

[0006]

Means for Solving the Problems The present invention, which has solved the above-mentioned problems, relates to a hot-rolled material of an Al-Mg-Si-based aluminum alloy sheet, which is prepared before cold rolling or before final solution treatment. Precipitated particles having an average particle size of 0.5 μm or more (Mg, S
Mg ₂ Si and S, which are precipitation compounds of main additive elements such as i
The gist is that the density of i alone or the like is 0.2 / μm ³ or less.

[0007] In the above aluminum alloy plate, Mg
Is 0.3 to 1.5%, and the content of Si is 0.3 to 1.5%.
1.5%, preferably Mn, Cr,
It is recommended to contain at least one selected from the group consisting of Zr, V, and Ti, in which case the content of each element is Mn: 0.5% or less, Cr: 0.3% or less, respectively. Z
r: 0.2% or less, V: 0.2% or less, Ti: 0.15
% Is desirable. Further, it is desirable that Cu be contained in an amount of 1.0% or less, and Fe is desirably limited to 0.7% or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The hot-rolled material according to the present invention can be used for automobiles or the like by performing cold rolling and solution treatment in a conventional manner or by performing solution treatment without performing cold rolling. This is an intermediate plate material used as an aluminum alloy plate. Formability (extended formability, deep drawability, bendability) and BH (Bake
In order to obtain an aluminum alloy sheet with excellent hardening properties, it is desirable that the main additive elements are completely dissolved after the solution treatment. When precipitates having a particle size are present at a high density, it is difficult to completely form a solid solution within the range of a practical solution treatment. To completely solidify the precipitates, it is possible to raise the solution treatment temperature or perform the treatment for a long time, but in this case, the crystal grains become coarse, and conversely, forming The property is deteriorated. Therefore, in the Al-Mg-Si-based aluminum alloy sheet of the present invention, a hot-rolled material capable of sufficiently forming precipitates in a solid solution state under a solution treatment condition that does not cause coarsening of crystal grains. Before the cold rolling or before the final solution treatment, the density of the precipitated particles having an average particle size of 0.5 μm or more was 0.2 particles / μm.
^It adopts a method of controlling to ³ or less.

The hot-rolled material according to the present invention can be manufactured by performing the following casting, soaking, and hot rolling.

First, the casting process may be the same as a general manufacturing process applied to a JIS 6000-based aluminum alloy. For example, an ingot may be prepared by a method such as DC casting.

Next, in the homogenizing heat treatment before hot rolling, from the viewpoint of eliminating segregation generated at the time of casting and forming a solid solution state of main additive elements (Mg, Si, etc.) as much as possible, at a temperature of 500 ° C. or more. It is recommended to keep at temperature. It is also desirable that the starting temperature of the hot rolling after the homogenization treatment is 500 ° C. or higher.

[0012] In the hot rolling, 0.5 μm
It is necessary to control the starting temperature, the intermediate temperature, the rolling reduction, the inter-pass time, and the like during hot rolling so that the density of the precipitated particles having the above-mentioned particle diameters becomes 0.2 grains / μm ³ or less. Specifically, it is desirable that the starting temperature in the hot rolling be 500 ° C. or more and the reduction rate up to the intermediate temperature (450 ° C.) in the hot rolling be 70% or more. Thereafter, the temperature of the aluminum alloy material is cooled to 350 ° C. or less by water cooling or the like as quickly as possible, and hot finish rolling to a desired thickness may be performed.

Although the hot rolling process necessarily involves a temperature drop, the rolling reduction in the temperature range of 500 ° C. to 450 ° C. is made as large as possible, and the temperature drop is recovered as much as possible by processing heat. By performing hot rough rolling in a solid solution state of the main additive element as much as possible, and then rapidly cooling to 350 ° C. or less, fine and uniform precipitates can be formed. Thereby, in the hot finish rolling following the hot rough rolling, a hot-rolled material having fine crystals (that is, the density of precipitated particles having an average grain size of 0.5 μm or more is 0.2
Pieces / hot rolled material of not more than ³ μm ³ ).

The average particle size thus obtained is 0.5 μm
If the above hot-rolled material having the above-mentioned precipitated particle density of 0.2 particles / μm ³ or less is used, cold rolling and solution treatment in accordance with a conventional method or direct solution treatment is performed to form the material. An Al-Mg-Si-based aluminum alloy plate having excellent properties and BH properties can be obtained. In addition, it is desirable not to perform intermediate annealing, and it is recommended not to perform intermediate annealing even when cold rolling is repeatedly performed. When performing the solution treatment subsequent to the cold rolling, the work structure introduced by the cold rolling can be recovered and recrystallized,
In addition, the main additive element can be dissolved. Since the solid solution state after the solution treatment greatly affects the formability and BH property of the Al-Mg-Si based aluminum alloy sheet,
By realizing a solid solution state as complete as possible, the strength of the aluminum alloy sheet is increased, and furthermore, the formability and B
It is desirable to improve the H property. The presence of undissolved precipitates causes deterioration of bendability. As a guide of the solution state, although it depends on the composition of the Al—Mg—Si alloy, the conductivity is 45% IACS [International Announcement].
ealed Copper Standard].

In the solution treatment, S is a main additive element.
It is important that i and Mg are sufficiently dissolved,
When a method of holding the solution treatment at a high temperature for a long time is employed as a method for realizing the same, the growth and coarsening of the crystal grains occur due to the holding at a high temperature for a long time, thereby deteriorating the formability and the bendability. Therefore, hot rolling that satisfies the conditions according to the present invention in obtaining an aluminum alloy sheet that exhibits excellent formability even when subjected to a low-temperature and short-time solution treatment that is advantageous from the viewpoint of productivity and cost. It is important to adopt wood.

However, if the subsequent cooling step is performed at an insufficient cooling rate even though the precipitates can be sufficiently solution-solved, the precipitates are formed again during cooling, and the moldability, BH property,
It is desirable to adopt a cooling rate of 5 ° C./sec or more because the bending property is deteriorated.

Next, preferred numerical ranges of the Al-Mg-Si alloy according to the present invention will be described below.

Mg: 0.3-1.5% Si: 0.3-1.5% Mg is a solid solution strengthening element that also contributes to improvement in strength and ductility. Mg and Si are described in G. P. Mg called zone
2 An element that forms an aggregate (cluster) or an intermediate layer having a Si composition and contributes to increasing the strength by baking (baking coating). It is desirable that both Mg and Si be contained in 0.3% or more. More preferably, it is at least 4%. However, if the content is too large, the formability deteriorates. Therefore, it is desirable that both Mg and Si be 1.5% or less.
More preferably, it is 2% or less.

Mn: 0.5% or less Cr: 0.3% or less Zr: 0.2% or less V: 0.2% or less Ti: 0.15% or less Formed because it has the effect of refining crystal grains. Although it is effective in improving the properties, if it is added beyond the upper limit value, there is a problem that a coarse compound is formed, which serves as a starting point of destruction and suppresses recrystallization.

These elements have the effect of refining the crystal grains. If at least one of these elements is added, grain boundary destruction can be suppressed, and the formability can be further improved. it can. However, when each element is contained beyond the upper limit, a coarse compound is formed between Al and these elements, which becomes a starting point of destruction and rather deteriorates moldability. Is desirable.

Cu: 1.0% or less Cu has the effect of improving the age hardening rate during baking, and when added, the strength and moldability are improved. However, if too much, the corrosion resistance is deteriorated. And more preferably 0.6% or less.

Fe: 0.7% or less Fe is contained as an unavoidable impurity.
Since e forms a compound with Si, the effect of the added Si becomes weak and the strength is deteriorated, and the formability is deteriorated due to the increase and coarsening of the amount of the compound.

It is to be noted that unavoidable impurities other than those described above may be present.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are not intended to limit the present invention, and any design change based on the above and subsequent gist is not limited to the present invention. Are included within the technical scope of

[0025]

EXAMPLE Hot-rolling and cold-rolling were performed using Al-Mg-Si alloys having the respective compositions shown in Table 1 under the conditions shown in Table 2 to obtain a sheet having a thickness of 1 mm. Solution treatment under the conditions and quenching to obtain a 1 mm thick test material (T4
Material). The particle density of 0.5 μm or more and the electrical conductivity were measured by the following methods, and the following bulging test and hydraulic bulge test were performed for the purpose of evaluating press formability. The results are shown in Table 3.

[Method for Measuring Particle Density of 0.5 μm or More]
For the measurement of particle density, a sample for observation with a transmission electron microscope was prepared from each test material at a stage before hot rolling and before cold rolling, and observed at a magnification of 10,000 or more and at a visual field of 5 or more places for each sample. After that, the particle size distribution of the precipitated particles was determined by image processing. As for the density, the volume was calculated from the transmission thickness of the transmission electron beam and the viewing area, and the density for each particle distribution was obtained.

[Measurement of Conductivity] The conductivity was measured by measuring each test material having a thickness of 1 mm with a conductivity measuring instrument adjusted in advance by measuring pure copper and pure silver, and corrected according to temperature to obtain “% IACS”. "As a unit.

[Extension molding test] Each test material was tested for a length of 180
mm, width 110 mm, and after applying lubricating oil, 10
Using a 1.6 mmφ ball head overhang jig, the overhang speed 4
A stretch forming test was performed at a wrinkle pressure of 200 kN / mm / s, and the forming limit cracking height (LDH) was measured.

[Hydraulic bulge test] A 100 mm square test piece was sampled from each test material having a thickness of 1 mm produced by the above method, and a hydraulic bulge test was performed using a 52.8 mmφ die, and a test was carried out. The blister height was measured.

[0030]

[Table 1]

[0031]

[Table 2]

In Table 1 above, No. Nos. 1 to 11 are Al alloys satisfying the component composition according to the present invention. 1
2 to 14 are Al alloys that do not satisfy the component composition according to the present invention. In Table 2, circled letters 1 to 7 are hot-rolled materials according to the present invention, and circled letters 8 to 10 are comparative examples.

[0033]

[Table 3]

No. 3 in Table 3 1 to 17 are Al alloy sheets using the hot-rolled material according to the present invention (the alloy compositions are Nos. 1 to 11 in Table 1;
7), the LDH in the overhang test and the swelling height in the hydraulic bulge test are high, and the press formability is excellent. On the other hand, No. Nos. 18 to 25 are comparative examples in which the density of precipitated particles having an average particle size of 0.5 μm or more exceeds 0.2 particles / μm ^3, which indicates that press formability is poor.

[0035]

As described above, according to the present invention, a hot-rolled material of an aluminum alloy sheet having excellent press formability can be provided.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C22F 1/00 630 C22F 1/00 630K 683 683 684 684C 685 685Z 690 690

Claims (5)

[Claims] 1. A hot-rolled material of an Al—Mg—Si-based aluminum alloy sheet, which is a stage after hot rolling and before cold rolling and solution treatment or a stage after hot rolling and before solution treatment. Average particle size of 0.5μ
A hot-rolled material of a highly formable aluminum alloy sheet, wherein the density of precipitated particles of m or more is 0.2 / μm ³ or less. 2. The content of Mg is 0.3 to 1.5% (mean% by mass, the same applies hereinafter), and the content of Si is 0.3 to 1.5%.
The hot-rolled material according to claim 1, which is 1.5%. 3. It contains at least one selected from the group consisting of Mn, Cr, Zr, V and Ti, and the content of each element is Mn: 0.5% or less, Cr: 0.3%. The hot-rolled material according to claim 1 or 2, wherein Zr: 0.2% or less, V: 0.2% or less, and Ti: 0.15% or less. 4. The hot-rolled material according to claim 1, further comprising 1.0% or less of Cu. 5. The hot-rolled material according to claim 1, further comprising 0.7% or less of Fe.