JPH04160131A - Al-mg-si alloy plate excellent in strength and formability, and its manufacture - Google Patents

Abstract

PURPOSE:To improve strength and formability of Al-Mg-Si alloy by adding specified amts. of Cu and Cr, Zr, Mn into the alloy to limit Fe amt. and controlling the volume proportion of intermetallic compd. CONSTITUTION:An alloy ingot used consists of, by wt.%, 0.6-1.2 Mg, 0.4-1.0 Si, 0.5-1.0 Cu, and at least one transition element of 0.10-0.25 Cr, 0.05-0.15 Zr, and 0.10-0.20 Mn, with Fe limited to <=0.10, and the balance Al. This ingot is subjected to heat treatment for homogenization at 450-560 deg.C, hot-rolled at 250-550 deg.C, cold-rolled to obtain a rolled material and then treated to make a solid soln. at 500-550 deg.C. The structure of the alloy is controlled to include a transition element intermetallic compd. by 0.05-0.1%. This alloy plate shows superior formability to that of T4 material of 6061 alloy which is conventionally a typical Al-Mg-Si alloy. When this alloy is treated for aging to change into T6 material, it shows higher strength than 6061-T6 material by 25% of durability.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an aluminum alloy plate and a method for manufacturing the same.
More specifically, AQ-Mg has excellent strength and formability.
-Regarding an Si-based alloy plate and a method for manufacturing the same. (Conventional technology and problems to be solved) Traditionally, A.
The fl-Mg-Si alloy (6000 series aluminum alloy) plate material includes 6061 alloy (standard composition: Al-1,
0Mg-0,6Si-0,30Cu-0,20Cr)
is known (for example, "Aluminum Handbook J" published by the Light Metals Association), and its standard mechanical properties are
As shown in the table, as is clear from the table, 6061 alloy is T
4 heat treatment has a low yield strength of 150 MPa and a high elongation of 22%, making it suitable for finishing. Artificially aged after molding. If it is made of T6ml quality (standard aging time: 160°C x 18hr), the tensile strength will be 310MPa and the yield strength will be quite high, 275MPa. Because this alloy has good weldability, it is also used as a welding material, and is widely used in ships, vehicles, land structures, etc.

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However, in recent years, there has been a strong demand for higher speeds and higher performance in transportation equipment, and there has been a demand for the development of high-strength materials that can be made thinner. There has been a strong demand for the development of an AM-Mg-3i alloy with an improvement of more than %. The present invention was made in response to these demands, and is an A
The object of the present invention is to provide a Q-Mg-Si alloy plate and a method for manufacturing the same. (Means for Solving the Problems) In order to solve the above problems, the present inventors have devoted themselves to research and development on the following two points. (1) First, conventional Al-M represented by 6061 alloy
The strengthening mechanism of g-Si alloys is based on the following age hardening mechanism. S, S, (solid solution) → G, P, zone → β'-Mg2S
j (T4 state) (T6 state) Therefore, since there is a limit to simply increasing the amounts of Mg and Si (the total amount of Mg+Si is about 1% at most), it is necessary to provide another strengthening mechanism and perform composite strengthening. (2) Elongation, which is a guideline for formability, should be determined by keeping the strength as low as possible.
intermetallic compounds (dispersoids) formed in materials to refine the crystal grains of structural materials.
) to reduce as much as possible the stress concentration around these hard second phase particles during the molding process and to reduce work hardening during the molding process. It is known that stress concentration and work hardening can be reduced by controlling the amount of second phase particles. Therefore, we have conducted extensive research on metallurgical means and manufacturing conditions that can provide the above two effects to Al-Mg-Si alloys and produce Al-Mg-3i alloys with excellent strength and formability. As a result, the present invention has been achieved here. That is, in the present invention, Mg: 0.6 to 1.2%, Si:
0.4-1.0% and Cu: 0.5-1. Contains Q%, further Cr: 0.10~0.25%, Zr: 0.05~
0.15% and Mn: 0.10 to 0.20%, and contains at least one transition element of
．． Regulated to 10% or less, with the remainder essentially consisting of Al,
The volume fraction of the transition element-based intermetallic compound is 0.05 to 0.1
The gist of this invention is a 〇-Mg-Si based alloy plate which has excellent strength and formability and is characterized by a microstructure controlled to %. In addition, the manufacturing method includes homogenizing an aluminum base metal ingot having the above chemical components at 450 to 560°C, hot rolling at a temperature of 250 to 550°C, and rolling the ingot at 350 to 400°C as necessary. By performing intermediate annealing, cold rolling to obtain a rolled material, and solution treatment at a temperature of 500 to 550°C. The volume fraction of the transition element-based intermetallic compound is 0.05 to 0.1.
It is characterized by controlling the structure to %. The present invention will be explained in further detail below. (Function) First, the reason for limiting the chemical components of the metal alloy in the present invention will be explained. Mg: Mg strengthens itself through solid solution strengthening and aging precipitates β' −
Aging precipitate S' combined with Mg2Si and Cu (described later)
- Strength is imparted by precipitation hardening with CuMgAl 2. However, if it is less than 0.6%, sufficient strength cannot be obtained, and if it is added in excess of 1 or 2%, the equilibrium phase Mg2Si will be formed as a crystallized substance during casting, resulting in poor formability as seen in the decrease in elongation. decreases significantly. Therefore, Mg
The content is in the range of 0.6 to 1.2%. Si: Si mainly imparts strength through precipitation hardening of aging precipitates β'-Mg2Si. However, if it is less than 0.4%, sufficient strength cannot be obtained, and if it is added in excess of 1.0%, equilibrium phase Mg2Si will crystallize, greatly reducing elongation. Therefore, the Si content is in the range of 0.4 to 1.0%. Cu: Cu imparts strength through aging precipitates S'-CuMgAI22. In the present invention, Mg combines not only with Si but also with Cu, resulting in a composite precipitation hardening effect. However, if it is less than 0.5%, sufficient strength cannot be obtained;
Moreover, if it is added in an amount exceeding 1.0%, a room temperature aging phenomenon will appear after solution treatment. Also. During casting, Cu2FeAl7 crystallizes, resulting in elongation and greatly reduced formability. Therefore, the Cu content is 0.5~1゜0%
The range shall be . Cr, Zr, Mn: Transition elements of Cr, Zr, and Mn are mixed with Al and intermetallic compounds (dispersoids) Z r A (13, Cr2M gz A D 1s,
Generate MnAn. It is possible to provide a material with fine grains that provides the strength, corrosion resistance, and fatigue strength necessary for structural alloy materials. but,
Cr, Zr, and Mn are 0.10%, 0°05%, and 0.05%, respectively.
If it is less than 10%, the above effect cannot be obtained sufficiently, and if it is added in excess of 0.25% to 0.15% or 0.20%, coarse intermetallic compounds are formed, which greatly reduces elongation. Therefore, the Cr content is 0.1-0.25%, the Zr content is 0.05-0.15%, and the Mn content is 0.10-0.15%.
The range is 0.20%. However, it is sufficient to add at least one of each. Fe: Fe is originally contained in Al base metal as an impurity.
When the amount of Fe is more than 0.10%, Cu2FeA
l, crystallizes during casting and greatly reduces elongation. Therefore, the amount of impurity Fe is regulated to 0.10% or less. Next, the manufacturing conditions of the present invention will be explained. The ingot obtained by casting an aluminum alloy having the above chemical composition is used to homogenize the main elements that are heterogeneously distributed inside, and to form intermetallic compounds between transition elements and Al, that is, dispersoids. , ZrAl3,
Cr2Mg5A Q1. , the diameter of the intermetallic compound called M n A Q 6 is several 100 to 2000 people, and it is homogenized at 450 to 560 °C to control its volume fraction to 0.05 to 0.1%. Apply heat treatment. The above effects cannot be obtained outside this temperature range. Note that the homogenization heat treatment time can be determined as appropriate, for example, 4
At a low temperature of 50°C, 8 to 12 hours is required, and at a high temperature of 560°C, 4 to 8 hours is sufficient. The size of the intermetallic compound is smaller at lower temperatures and for a shorter period of time, and conversely becomes larger at higher temperatures and for a longer period of time, and the diffusion coefficient and crystal structure in the Al alloy differ depending on the transition element, so the respective sizes are generally ZrAl, <
The order is Cr2MgzAlzm<MnAl. After the homogenization heat treatment, hot rolling is performed at a temperature of 550 to 250°C to process the rough ingot structure into a wrought material structure. On this occasion,
The above-mentioned intermetallic compounds dispersoids prevent coarsening of crystal grains and provide an unrecrystallized grain structure or a fine recrystallized grain structure. Such an effect cannot be obtained outside the above temperature range. Next, cold rolling is performed to process the sheet into a desired thickness. At this time, if necessary, that is, if edge cracks etc. occur in the rolled material or if it is desired to control crystal grains, intermediate annealing is performed at a temperature of 350 to 400 ° C. before or during cold rolling to make the material soft. Cold rolling can be performed again. If the temperature of intermediate annealing is less than 350°C, sufficient softening cannot be obtained,
On the other hand, if the temperature exceeds 400°C, the material becomes hard due to solid solution of the main additive elements, so the above temperature is preferable. Finally, solution treatment is carried out at a temperature of 500 to 550 °C,
Make the main elements a solid solution. If the temperature is less than 500"C, the main additive elements Mg, Si, and Cu will not dissolve sufficiently in solid solution.
If the temperature exceeds .degree. C., there is a risk of eutectic melting (burning), so the temperature should be in the range of 500 to 550.degree. The solution treatment time is J
It is sufficient to follow the example of aluminum alloy for heat treatment prescribed by IS, etc. For example, for a plate with a thickness of about 1.
Up to n is fine. By this solution treatment, the dislocation density of the dislocations introduced by cold rolling is reduced, and this material becomes a relatively low-yield material during the next forming process, and is used for processing. Also, in this step, the intermetallic compound disperso
ids are unrecrystallized or retain a fine recrystallized grain structure,
It is possible to prevent roughness of the material during molding. After this, molding processing or heat treatment (tempering) according to the normal process
By applying this, a high-strength material can be obtained. For example, after being directly or subjected to a desired forming process such as bending or pressing, it is typically subjected to an aging treatment at 160° C. for about 18 hours, and then used for use. At this time, β'-Mg2Si and S'-CuMgAl, which are precipitation strengthening phases, are present in the material.
is generated, imparting high strength to the material. (Example) Next, an example of the present invention will be shown. 1. Strictly adhere to Nn 1 to &18 aluminum alloy ingots having the compositions shown in Table 2. Homogenization heat treatment at 480°C x 12 hours is carried out, followed by hot rolling at a temperature of 450 to 300°C.
Made of Reiho thick plate material. Furthermore, it was finished into a 1 mm plate material by cold rolling. Next, it was subjected to solution treatment at 530℃ x 30wins, cooled with water, and left at room temperature for about a week to become a T4 material.
A JISS No. test piece was prepared and its mechanical properties were determined. Furthermore, it was aged at 160° C. for 18 hours to obtain a T6 material, and its mechanical properties were determined in the same manner. In addition, the T4 material was observed using a transmission electron microscope at a portion having a sample thickness of about 2000 people, and the volume fraction of the intermetallic compound was determined. These results are also listed in Table 2. As is clear from Table 2, invention examples &1 to Nl115
The volume fraction of the intermetallic compound was controlled to 0.05 to 0.09, and the elongation of the T4 material was 24 to 26%, which showed high formability compared to the 22% elongation of the 6061 alloy. Furthermore, T6
After aging, the yield strength is 348 to 363 MPa, which is 25 to 30% of the 275 MPa yield strength of 6061 alloy.
It shows high strength that exceeds the above. On the other hand, in the comparative example, only Na 6, &8.11 kilO exceeds the 6061 alloy in elongation of T4 materials, and furthermore, the yield strength of these T6 materials is all 300 MPa or less, and high strength is not obtained. Using the aluminum alloy ingots &1 to &3 of Example 1,
A cold-rolled plate having a final thickness of 1 inch was prepared under the manufacturing conditions shown in Table 3, and then subjected to solution treatment, and the mechanical properties and volume fraction of intermetallic compounds were measured in the same manner as in Example 1. The results are also listed in Table 3. As is clear from Table 3, in the invention examples Nα1 to Nα6, the volume fraction of the intermetallic compound was controlled to 0.05 to 0.09%, the elongation of the T4 material was 23 to 26%, and the 6061 alloy It showed high formability compared to the elongation of 22%. Furthermore, T6
The material subjected to aging treatment has a yield strength of 350 to 360 MPa, showing high strength exceeding the yield strength of 6061, 275 MPa, by 27 to 30% or more. On the other hand, in the comparative example, the only T4 material with an elongation equivalent to that of the 6061 alloy is Nα9, and the yield strength of the T6 material is all 300 MPa or less, and high strength is not obtained.

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(Effects of the Invention) As detailed above, according to the present invention, the conventional representative A
It has formability that is equal to or better than the formability of T4 material of 6061 alloy, which is an l-Mg-Si alloy, and when made into T6 material by aging treatment, it has high strength that exceeds the yield strength by more than 25% of 6061-T6 material. An aluminum alloy plate material having the following properties is obtained. Therefore, the effect of contributing to higher strength and thinner walls is significant. Patent applicant Hisashi Nakamura, patent attorney representing Kobe Steel, Ltd.

Claims (3)

[Claims] (1) In weight% (the same applies hereinafter), Mg: 0.6 to 1.2
%, Si: 0.4-1.0% and Cu: 0.5-1.0
%, further Cr: 0.10 to 0.25%, Zr:
0.05-0.15% and Mn: 0.10-0.20%
The impurity Fe is controlled to 0.10% or less, and the remainder is substantially Al.
The volume fraction of the transition element-based intermetallic compound is 0.0.
An Al-Mg-Si alloy sheet with excellent strength and formability, characterized by a controlled structure of 5 to 0.1%. (2) 4 aluminum alloy ingots having the above chemical components
Homogenization heat treatment at 50-560℃, 250-550℃
Hot rolled at a temperature of ℃, cold rolled to form a rolled material, 5
By performing solution treatment at a temperature of 00 to 550°C,
The volume fraction of the transition element-based intermetallic compound is 0.05 to 0.1.
A method for manufacturing an Al-Mg-Si alloy sheet having excellent strength and formability, characterized by controlling the structure to %. (3) The method according to claim 2, wherein intermediate annealing at 350 to 400°C is performed during cold rolling.