JPH06272001A - Production of al-mg-si series alloy metal plate excellent in heating hardenability - Google Patents

Abstract

PURPOSE:To produce an Al-Mg-Si series alloy metal plate excellent in heating hardenability by subjecting an Al allay contg. specified amounts of Mg, Si, Fe, Cu, Zn, Mn, Cr, Zr, Ti, B and Be to a specified homogenizing treatment, hot rolling, cold rolling and solution treatment. CONSTITUTION:The ingot of an Al alloy contg., by weight, 0.2 to 2% Mg and 0.2 to 2% Si and furthermore contg. one or more kinds among <=2% Fe, <=2% Cu, <=3% Zn, <=2% Mn, <=0.5% Cr, <=0.3% Zr, <=0.2% Ti, <=0.1% B and <=0.05% Be, and the balance substantial Al is heated to >=480 deg.C and is subjected to homogenizing treatment. After that, this ingot is heated to >=480 deg.C, is thereafter subjected to hot rolling and is passed through the temp. range of 360 to 450 deg.C for <15min, and it is completed at <=360 deg.C. Subsequently, this hot rolled plate is subjected to cold rolling including intermediate rolling according to necessary to regulate its plate thickness into a prescribed one. Next, this cold rolled plate is subjected to solution treatment of heating to >=500 deg.C for >=10sec.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an Al-Mg-Si alloy sheet for a member which is heated by baking after forming, and more specifically, the strength is increased by heating after forming. It is possible to obtain an aluminum alloy plate material for a structural part in which

[0002]

2. Description of the Related Art At present, a plate material is molded and used as a member such as a vehicle outer plate or a wheel plate member. The characteristics required for aluminum plate materials used for such members are high moldability so that they can be formed into a predetermined shape at the time of molding and high reliability and high corrosion resistance when used as members at the same time. It is to let.

As a material having such characteristics, A
Plate materials of 1-Mg-based alloy and Al-Mg-Si-based alloy are generally used. This Al-Mg-based alloy is characterized by having medium strength and particularly excellent formability, while the Al-Mg-Si-based alloy has a formability of Al-
Although somewhat inferior to Mg-based alloys, it is characterized in that the strength increases as the coating is heated. Therefore, there is a tendency that an Al-Mg-based alloy is used for parts having complicated shapes and an Al-Mg-Si-based alloy is used for parts requiring high strength.

[0004]

In recent years, there has been a strong demand for improvement of fuel efficiency of automobiles, improvement of operability of electric products and mechanical products, and improvement of efficiency. Therefore, there is a further demand for weight reduction of parts of those products. It is showing strength. In response to such demands, the thickness of members has been reduced, and even higher strength is required for aluminum materials as raw materials.

Therefore, vigorous studies have been made to improve the heat-hardening property of Al-Mg-Si alloys. However, on the other hand, from the viewpoint of improving the efficiency of the painting process,
There is a tendency to shorten the time, and there is a tendency to adopt conditions under which the Al-Mg-Si alloy is hard to harden. Against this background, development of a plate material having higher heat-curing property is strongly desired.

[0006]

Means for Solving the Problems In order to solve these problems, the present inventors have made a detailed study by paying attention to the structure in an Al—Mg—Si alloy plate material, and as a result, have arrived at the present invention. More specifically, the present invention succeeds in obtaining a structure for imparting a high heat-hardening property to an Al-Mg-Si alloy sheet material by controlling the hot rolling process.

That is, the manufacturing method of the Al-Mg-Si alloy sheet according to the present invention is as follows: Mg: 0.2-2 wt%, Si: 0.2-2 wt%
%, And Fe: 2 wt% or less, Cu: 2 wt% or less,
Zn: 3 wt% or less, Mn: 2 wt% or less, Cr: 0.5 wt%
Below, Zr: 0.3 wt% or less, Ti: 0.2 wt% or less, B:
An Al alloy ingot containing 0.1 wt% or less and Be: 0.05 wt% of 1 type or 2 types or more, and the balance substantially consisting of Al.
After heating to 480 ° C or higher for homogenization, or after heating to 480 ° C or higher during hot rolling after homogenization, pass the temperature range of 360 to 450 ° C in less than 15 minutes in hot rolling. The hot rolling finish temperature is set to 360 ° C or less, then cold rolling is performed, and if necessary, intermediate annealing is performed in the middle of cold rolling to obtain a predetermined plate thickness, and then heating to a temperature of 500 ° C or more for 10 seconds or more. It is characterized in that it is subjected to solution treatment.

[0008]

The reason for limiting the Al alloy composition targeted in the present invention as described above is as follows. That is, Mg,
If any of Si is less than 0.2 wt%, sufficient heat-curability cannot be obtained, and if more than 2 wt% is contained, the formability is deteriorated.

Fe, Cu, Zn, Mn, Cr, Z
Each element of r, Ti, B, and Be forms a solid solution or a fine compound in the material, and contributes to homogenization of the material structure and improvement of strength. More than one seed is added. However, if added in excess of the respective upper limits, a coarse compound is produced and moldability and strength are both reduced.

Next, the hot rolling condition, which is the most characteristic feature of the present invention, will be described. A targeted by the production method of the present invention
In order to improve the heat-hardening property in the 1-Mg-Si based alloy, it is necessary to make Mg and Si elements in a solid solution as much as possible during the solution treatment. Regarding the means therefor, the inventors have made detailed studies on the structural behavior of the Al—Mg—Si alloy.

The manufacturing method of the present invention has been made as a result. That is, in order to maximize the amount of solid solution of Mg and Si during solution treatment, M before solution treatment
It is necessary to increase the solid solubility of g and Si as much as possible and finely disperse the size of the compound containing these elements.
The solid solution reaction of these compounds proceeds by heating the material at a high temperature, the volume ratio of the compound in the material decreases, and the solid solubility increases. Therefore, by heating the material to a temperature as high as possible, the volume ratio of the compound containing Mg and Si is decreased and the solid solution amount is increased, which is effective in improving the heat-curability.

However, not only these compounds are not completely eliminated by heating at a high temperature, but the volume ratio of the entire compound is reduced, but the size of each individual compound remaining after heating at a high temperature becomes larger than the size of the compound before heating. Things have been found. Further, it has been clarified that the temperature of the material heated during the hot rolling lowers during the rolling and that the above-mentioned Mg and Si compounds reprecipitate during the rolling and at the end of the rolling. This reprecipitation is characterized by coarsening of the above-mentioned residual compound and preferential precipitation / growth at the recrystallized grain boundary that occurs during hot rolling or immediately after the end of rolling. Moreover, since this precipitation reaction is a reaction at a relatively high temperature, the precipitation rate is high, and strain during hot rolling also promotes this precipitation, so that a coarse precipitation phase grows in a short time. It was confirmed that such a coarse precipitation phase is unlikely to form a solid solution during solution treatment.

Therefore, in order to suppress such reprecipitation during hot rolling, the material heated to a high temperature in a homogenizing treatment or the like is rapidly cooled and rolled at a low temperature to reduce the precipitation rate. It was found that it is effective to refine the recrystallized grains to disperse preferential precipitation / growth at grain boundaries.

The present invention has been made based on such a technical idea, and the reason why the manufacturing conditions are defined in the present invention will be described below.

The heating temperature in the homogenization treatment before hot rolling is
Alternatively, the heating temperature for heating in the course of hot rolling needs to be as high as possible to increase the solid solubility of Mg and Si as much as possible. However, heating below 480 ° C does not provide sufficient solid solution, and 500 ° C or higher is a desirable heating temperature. The upper limit of the heating temperature is not particularly limited, and it is preferable that the heating temperature is high, and the heating temperature may be lower than the solidus temperature of the material.

When hot rolling is carried out in the temperature range of 360 to 450 ° C., precipitation is most likely to proceed and recrystallized grains are likely to become coarse. Therefore, it is necessary to cool this temperature range in a short time. However, if exposed to this temperature range for 15 minutes or more, the above-mentioned coarse precipitates are generated and the heat-curability is reduced, and it is preferably within 10 minutes.

However, it is difficult to rapidly cool a thick ingot such as an ingot, and a preferable method is to use an ingot or a rolled plate having a small wall thickness so that the cooling during the rolling progresses quickly. The plate thickness is rapidly reduced by increasing the rolling amount during rolling, and rolling is performed to a wall thickness that facilitates cooling in a short period of time. It is conceivable to use a method such as rapid cooling by applying. The present invention does not specify the details of these conditions, and it is sufficient that the temperature / time conditions are satisfied.

Next, the hot rolling finish temperature is set to 360 ° C. or lower. This is because if the temperature after hot rolling exceeds 360 ° C, the recrystallized grains become coarse and the heat-hardening property decreases.

Further, the plate which has been hot rolled is subjected to cold rolling, and if necessary, subjected to intermediate annealing during the cold rolling, or to a predetermined plate thickness without being subjected to it, and then to a temperature of 500 ° C. or higher.
Heat for 10 seconds or more to perform solution treatment. However, if the temperature is less than 500 ° C or heating for less than 10 seconds, solution treatment is not sufficiently performed. The upper limit of the heating temperature is not particularly limited, but it is usually performed at a temperature below the solidus temperature. Further, it is preferable that the heating time is long so that the solution formation proceeds easily. However, since heating for a too long time is economically disadvantageous, the heating time may be set for convenience of operation.

[0020]

Example An alloy having the composition shown in Table 1 was formed into a ingot having a thickness of 400 mm and a width of 1200 mm by ordinary DC casting. This alloy on one side 5
After chamfering by mm, these alloys were subjected to either heat treatment or hot rolling shown in Table 2 as shown in Table 3. The plate thickness after hot rolling was set to 5 mm and then cold rolled to a plate material of 1 mm.

Step A, which is the process of the present invention shown in Table 2, is that the plate thickness during hot rolling is about 150 mm and the material temperature is about 490 ° C.
Perform forced cooling with a refrigerant containing water-soluble oil, and in about 6 minutes
After cooling to 350 ° C, rolling was restarted. In the comparative steps B to D, the hot rolling conditions shown in Table 2 were achieved by adjusting the reduction amount and rolling time of hot rolling.

The strength and elongation of the plate material thus obtained were measured by a tensile test, and the tensile test piece was subjected to 2% tensile deformation to simulate coating heating after molding.
Heating was conducted at 20 ° C. for 20 minutes, and then a tensile test was performed to measure the strength. The results are also shown in Table 3.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

As is clear from Table 3, it can be seen that the manufacturing method of the present invention has excellent mechanical properties after heating and also has a large increase in yield strength due to heating. On the other hand, it can be seen that the comparative manufacturing method which is out of the scope of the present invention has low strength after coating heating and low curability by heating.

[0027]

According to the present invention, it is possible to remarkably enhance the heat-hardening property of an Al-Mg-Si type alloy used for automobiles, electric parts, etc., and it is possible to remarkably reduce the thickness and weight of members. Is played. Therefore, the plate material according to the present invention is suitable for automobile parts such as wheels and outer plates of two-wheeled vehicles, passenger cars, etc., parts for electric appliances or baking parts for which baking is applied after forming.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsutoshi Sasaki 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Aluminum Co., Ltd. (72) Inventor Gen 2 Watanabe 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Aluminum Co., Ltd.

Claims (1)

[Claims] 1. Mg: 0.2-2 wt%, Si: 0.2-2 wt%
%, And Fe: 2 wt% or less, Cu: 2 wt% or less,
Zn: 3 wt% or less, Mn: 2 wt% or less, Cr: 0.5 wt%
Below, Zr: 0.3 wt% or less, Ti: 0.2 wt% or less, B:
An Al alloy ingot containing 0.1 wt% or less and Be: 0.05 wt% of 1 type or 2 types or more, and the balance substantially consisting of Al.
After heating to 480 ° C or higher for homogenization, or after heating to 480 ° C or higher during hot rolling after homogenization, pass the temperature range of 360 to 450 ° C in less than 15 minutes in hot rolling. The hot rolling finish temperature is set to 360 ° C or less, then cold rolling is performed, and if necessary, intermediate annealing is performed in the middle of cold rolling to obtain a predetermined plate thickness, and then heating to a temperature of 500 ° C or more for 10 seconds or more. A method of manufacturing an Al-Mg-Si alloy sheet having excellent heat-hardening properties, which is characterized by performing a solution treatment.