KR102201131B1 - Heat treatment method of Al-Mg-Si alloy - Google Patents

Abstract

An embodiment of the present invention comprises the steps of determining the time and temperature conditions of natural aging of the Al-Mg-Si alloy; Preparing an Al-Mg-Si alloy by selecting an Mg/Si content ratio according to the determined natural aging time and temperature conditions; Determining time and temperature conditions for preliminary aging according to the determined time and temperature conditions for natural aging; Solutionizing the Al-Mg-Si alloy; Referencing the solutionized alloy; And Al-Mg suitable as an exterior plate for automobiles by providing a heat treatment method of an Al-Mg-Si alloy comprising the step of pre-aging the alloy according to the determined pre-aging time and temperature conditions. There is an effect that can provide a -Si alloy plate.

Description

Heat treatment method of Al-Mg-Si alloy}

The present invention relates to a heat treatment method of an Al-Mg-Si alloy, and more particularly, in consideration of the natural aging and bake hardening of the Al-Mg-Si alloy plate, the Mg/Si content ratio and pre-aging conditions for maintaining hardness It relates to a method of setting and heat treatment.

Aluminum alloy plate is a representative material that can replace the existing steel plate in order to improve fuel efficiency of automobiles and lighten the vehicle. Aluminum alloys are largely divided into non-heat-treated alloys and heat-treated alloys, and heat-treated alloys are further divided into 2XXX series of Al-Cu alloys, 6XXX series of Al-Mg-Si alloys, and 7XXX series of Al-Zn-Mg alloys. Among them, 6XXX series of Al-Mg-Si alloys are used as exterior plates for automobiles because they have excellent formability, corrosion resistance and specific strength, and can be age-hardened.

Due to the characteristics of automobile manufacturing, the Al-Mg-Si alloy sheet manufactured to manufacture an exterior sheet for automobiles takes a certain time from manufacturing the sheet to press forming and painting. It would be ideal if the alloy plate could be put into the automobile manufacturing process immediately after the rolling process of manufacturing the alloy plate, press-formed and painted.However, since automobile manufacturing requires a large number of materials and parts, all necessary materials are provided near the factory. It is a condition that cannot be put into production immediately. Therefore, it takes a certain amount of time required for transportation and storage until press forming and painting after the rolling process.

During the predetermined period of time, the Al-Mg-Si alloy plate is subjected to natural aging. It is known that the mechanical properties are partially changed by natural aging, and the hardness is partially increased by aging hardening, but the strength does not increase during the painting process after the natural aging. Due to this decrease in hardness, there is a disadvantage in that the mechanical properties of the alloy plate are not obtained to the maximum in the finished vehicle.

In the prior art, in order to solve this problem, the Al-Mg-Si alloy plate is subjected to stabilization heat treatment immediately after solution treatment to produce the plate, thereby suppressing the deterioration of physical properties due to natural aging during transport and storage, and curing properties during bake hardening after plate molding. It was intended to be greatly improved.

However, there is a problem that the stabilization heat treatment of the prior art does not lead to an improvement in hardness under all conditions. It was found that the heat treatment before natural aging was not effective depending on the natural aging period and the composition of the Al-Mg-Si alloy, and to solve this problem, the composition of the Al-Mg-Si alloy was selected in consideration of the natural aging time and bake hardening conditions. And it is necessary to set preliminary aging conditions.

Korean Patent Registration No. 0213678

The technical problem to be achieved by the present invention is to solve the above problems, in consideration of the natural aging and bake hardening of the Al-Mg-Si alloy plate, and heat treatment by selecting the composition of the Al-Mg-Si alloy having optimal physical properties. To provide a way.

Another technical problem to be achieved by the present invention is to provide a method of heat treatment by setting pre-aging conditions for maintaining hardness in consideration of the natural aging and bake hardening of the Al-Mg-Si alloy plate.

The technical problem to be achieved by the present invention is not limited to the technical problems mentioned above, and other technical problems that are not mentioned can be clearly understood by those of ordinary skill in the technical field to which the present invention belongs from the following description. There will be.

In order to achieve the above technical problem, an embodiment of the present invention includes determining the time and temperature conditions of natural aging of the Al-Mg-Si alloy; Preparing an Al-Mg-Si alloy by selecting an Mg/Si content ratio according to the determined natural aging time and temperature conditions; Solutionizing the Al-Mg-Si alloy; Referencing the solutionized alloy; And it provides a heat treatment method of the Al-Mg-Si alloy, characterized in that it comprises the step of pre-aging the quenched alloy.

In an embodiment of the present invention, the pre-aged alloy may further include a step of natural aging according to the determined natural aging time and temperature conditions.

In one embodiment of the present invention, the Mg/Si content ratio may be 0.3 to 2.5.

In one embodiment of the present invention, the Al-Mg-Si alloy may contain 0.3 to 1.0 wt% Mg and 0.3 to 1.0 wt% Si.

In one embodiment of the present invention, the natural aging time condition may be 7 days to 2 months.

In one embodiment of the present invention, the temperature condition of the natural aging may be 20 to 30 ℃.

In an embodiment of the present invention, the step of preparing the Al-Mg-Si alloy by selecting the Mg/Si content ratio according to the determined natural aging time and temperature conditions may be determined by a preset database.

In an embodiment of the present invention, it may further include determining the time and temperature conditions of the preliminary aging according to the determined time and temperature conditions of the natural aging.

In one embodiment of the present invention, the time condition of the preliminary aging may be 10 seconds to 3 days.

In one embodiment of the present invention, the temperature condition of the pre-aging may be 40 to 120 ℃.

In one embodiment of the present invention, the step of determining the time and temperature conditions of the preliminary aging according to the determined time and temperature conditions of the natural aging may be determined by a preset database.

In one embodiment of the present invention, the step of solutionizing the Al-Mg-Si alloy may be performed for 20 to 40 minutes at a temperature range of 550 to 570°C.

In one embodiment of the present invention, the step of referencing the solutionized alloy may be performed at -10 to 10°C for 30 to 90 seconds.

In order to achieve the above technical problem, another embodiment of the present invention provides an Al-Mg-Si alloy heat-treated by the above method.

In order to achieve the above technical problem, another embodiment of the present invention provides an exterior plate for a vehicle comprising the alloy.

According to an embodiment of the present invention, in consideration of the natural aging and bake hardening of the Al-Mg-Si alloy plate, an Al-Mg-Si alloy composition capable of maximizing the physical properties of the alloy plate is selected, and the preparation of the alloy plate By setting aging conditions and performing heat treatment, an Al-Mg-Si alloy plate suitable as an exterior plate for automobiles can be provided.

The effects of the present invention are not limited to the above effects, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a view showing the composition ratio of 9M4S, 6M6S and 3M10S in an embodiment of the present invention.
2 is a single aging (ST-AA) (a), two-stage aging (ST-NA-AA) (b) and multi-stage aging (ST-PA-NA-AA) (c) in one embodiment of the present invention. A diagram showing the experimental conditions according to.
3 is a graph of comparison of micro Vickers hardness of 9M4S, 6M6S and 3M10S according to two-stage aging (ST (560° C., 30 min)-NA (2 months)-AA (170° C., 20 min)) in an embodiment of the present invention .
Figure 4 is a comparison of the micro-Vickers hardness difference of 9M4S, 6M6S and 3M10S according to two-stage aging (ST (560 ℃, 30min)-NA (2 months)-AA (170 ℃, 20 minutes)) in one embodiment of the present invention graph.
Figure 5 is a comparison table of micro Vickers hardness of 9M4S, 6M6S and 3M10S by multi-stage aging (ST (560 °C, 30 min) -PA (100 °C, 1 h) -NA (2 months) -AA (170 °C, 20 min)) (a) and comparative graph (b).
6 is a multi-stage aging according to the experimental conditions of FIGS. 1 and 2 (ST(560° C., 30 min)-PA(100° C., 1 h)-NA(2 months)-AA(170° C., 20 min)) 9M4S( a), 6M6S (b) and 3M10S (c) micro Vickers hardness comparison graph.
7 is a TEM photograph of 9M4S, 6M6S and 3M10S after aging.

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be implemented in a number of different forms, and therefore is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and similar reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part is said to be "connected (connected, contacted, bonded)" with another part, it is not only "directly connected", but also "indirectly connected" with another member in the middle. "Including the case. In addition, when a part "includes" a certain component, it means that other components may be further provided, rather than excluding other components unless specifically stated to the contrary.

The terms used in the present specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or a combination thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

It is known that the decrease in hardness of Al-Mg-Si alloy during artificial aging after natural aging is caused by clusters. During natural aging, Mg and Si elements form clusters, and due to the clusters, the driving force for formation of β" precipitates decreases during bake hardening corresponding to artificial aging, resulting in lower hardness.

However, the inventors of the present invention found that the hardness decreases due to cluster formation under all conditions, and in order to prevent the hardness decrease, it is not possible to increase the hardness by preventing cluster formation by heat treatment before natural aging. In addition, it was found that in order to maintain or improve the hardness, the composition of the Al-Mg-Si alloy and the pre-aging conditions must be selected in a certain range according to the natural aging period and temperature conditions.

In the present invention, natural aging (NA) means that the Al-Mg-Si alloy is subjected to solution treatment followed by aging at room temperature. The natural aging includes those occurring during transportation to an automobile manufacturing plant or storage in a warehouse. It may also have a preliminary aging step of heat treatment before natural aging after the quenching. In other words, it is considered as natural aging if it is referred to after solution treatment and then aging at room temperature regardless of the presence or location of other treatments.

In the present invention, artificial aging (AA) mainly refers to a bake hardening treatment after painting in an automobile manufacturing process. In the automobile manufacturing process, the bake hardening treatment is usually performed at a temperature of 170 to 180° C. for 20 to 30 minutes. Detailed temperature and bake hardening time may vary depending on the color to be painted. In Examples and Experimental Examples of the present invention, aging was performed according to the above temperature range.

Pre-aging (PA) of the present invention refers to aging performed before natural aging. It is a concept corresponding to the stabilization heat treatment of the prior art, and in the present invention, it is characterized in that the aging time is much longer, up to 3 days.

An embodiment of the present invention comprises the steps of determining the time and temperature conditions of natural aging of the Al-Mg-Si alloy; Preparing an Al-Mg-Si alloy by selecting an Mg/Si content ratio according to the determined natural aging time and temperature conditions; Solutionizing the Al-Mg-Si alloy; Referencing the solutionized alloy; And it provides a heat treatment method of the Al-Mg-Si alloy, characterized in that it comprises the step of pre-aging the quenched alloy.

The method may further include natural aging the preaged alloy according to the determined natural aging time and temperature conditions.

The Mg/Si content ratio may be 0.3 to 2.5. Depending on the Mg/Si content ratio, there may be a difference in hardness when artificial aging after natural aging, and considering this, the Al-Mg-Si alloy is selected. For example, in the case of a natural aging period of less than 1 day, the Mg/Si content ratio is preferably close to 1, and when the natural aging period exceeds 1 day, the Mg/Si content ratio is preferably 1 or more. If the Mg/Si content ratio is less than 0.3 or more than 2.5, it is not preferable to ensure sufficient hardness.

The Al-Mg-Si alloy may contain 0.3 to 1.0 wt% Mg and 0.3 to 1.0 wt% Si. Mg and Si combine with Si in the aluminum alloy to form Mg ₂ Si to increase the hardness. However, when the amount exceeds 1.0 wt%, there is a problem that the workability is deteriorated due to insufficient tensile strength of the aluminum alloy, and when the amount is included in each of less than 0.3 wt%, sufficient hardness cannot be secured, which is not preferable.

The time and temperature conditions of the natural aging may include the time and temperature at which the pre-aged Al-Mg-Si alloy is transported and stored, as described above. Natural aging may mainly occur at room temperature, but may have a temperature range of 20 to 30°C depending on the transport or storage location. The temperature range is highly influenced by the season, and in order to reduce the influence of the season, a means of cooling or heating is required in a transportation means or a storage place.

The time conditions for the natural aging may range from 7 days to 2 months. The above conditions take into account the conditions of conventional automobile manufacturing, and the natural aging period may be prolonged due to a strike by automobile manufacturers. However, if the natural aging period exceeds 2 months, there is a problem that the effect of the preliminary aging fades as described later.

The method may further include determining the time and temperature conditions of the preliminary aging according to the determined time and temperature conditions of the natural aging.

The time and temperature conditions of the pre-aging may be from 10 seconds to 3 days and from 40 to 120°C, respectively. In the case of less than 10 seconds or less than 40℃, the pre-aging does not sufficiently affect the clusters of the Al-Mg-Si alloy, which is not preferable. In the case of more than 3 days or more than 120℃, the workability of the Al-Mg-Si alloy decreases and economical efficiency This off is not desirable.

The step of preparing the Al-Mg-Si alloy by selecting the Mg/Si content ratio according to the determined natural aging time and temperature conditions may be determined by a preset database. In addition, the step of determining the time and temperature conditions of the preliminary aging according to the determined time and temperature conditions of the natural aging may be determined by a preset database. The time and temperature conditions of natural aging can be adjusted in advance according to the conditions of the automobile manufacturer, and accordingly, the Mg/Si content ratio and the process conditions of the pre-aging step can be arbitrarily selected.

The step of solutionizing the Al-Mg-Si alloy may be performed for 20 to 40 minutes at a temperature range of 550 to 570°C, and the step of referencing the solutionized alloy is 30 to 90 at -10 to 10°C. It can be done in seconds.

In the description of the drawings of the present invention, ST (solution treatment) means solution treatment, PA (pre aging) means preliminary aging, NA (Natural aging) means natural aging, and AA (Artificial aging) means artificial aging.

1 is a diagram showing the composition ratio of 9M4S, 6M6S and 3M10S in one embodiment of the present invention, and FIG. 2 is a single aging (ST-AA) (a), two-stage aging (ST-NA) in an embodiment of the present invention. It is a diagram showing the experimental conditions according to -AA) (b) and multi-step aging (ST-PA-NA-AA) (c).

9M4S (Mg 0.9 wt%, Si 0.4 wt%, Mg/Si 2.5 composition aluminum alloy), 6M6S (Mg 0.6 wt%, Si 0.6 wt%, Mg/Si 1 composition aluminum alloy) according to FIG. ), 3M10S (Mg 0.3 wt%, Si 1.0 wt%, Mg/Si 0.3 composition aluminum alloy) was prepared, and then single aging (ST (560° C., 30 min)-AA (170° C., 20)) according to the conditions of FIG. Min)), two-stage aging (ST(560 ℃, 30min)-NA (2 months) -AA (170 ℃, 20 minutes)) and multi-stage aging (ST (560 ℃, 30min) -PA (100 ℃, 1 h) )-NA (2 months)-AA (170° C., 20 minutes)) to prepare a sample. At this time, the single aging, the two-stage aging and the multi-stage aging all include the step of terming at -10 to 10°C for 30 to 90 seconds after solution treatment (ST), and in the embodiment of the present invention, at 0°C for 1 minute The same was performed.

The hardness was measured for the prepared sample, and TEM photographing was performed. At this time, the microVickers hardness was measured 7 times under each condition to calculate the average of the 5 measured values excluding the maximum and minimum values, and DSC was measured at a heating rate of 10°C/min at -50 to 500°C. In addition, the microstructure was analyzed by observing from the (001) plane using a transmission electron microscope.

3 is a graph of comparison of micro Vickers hardness of 9M4S, 6M6S and 3M10S according to two-stage aging (ST (560° C., 30 min)-NA (2 months)-AA (170° C., 20 min)) in an embodiment of the present invention 4 is a micro Vickers hardness of 9M4S, 6M6S and 3M10S according to two-stage aging (ST (560° C., 30 min)-NA (2 months)-AA (170° C., 20 min)) in an embodiment of the present invention. It is a difference graph.

When performing the two-step aging, as shown in FIGS. 3 and 4, the 6M6S micro-Vickers hardness of which the Mg/Si ratio is 1 was the highest, and the hardness increase after artificial aging was also the largest. In addition, even during the natural aging process for 2 months at room temperature, the decrease in hardness of 6M6S with a ratio of Mg/Si of 1 was the lowest compared to 9M4S and 3M10S. However, when a long time after artificial aging has elapsed, the decrease in hardness of 6M6S occurred most significantly compared to 9M4S and 3M10S, but the overall hardness is the same, so it is judged not to be a problem.

Figure 5 is a comparison table of micro Vickers hardness of 9M4S, 6M6S and 3M10S by multi-stage aging (ST (560 °C, 30 min) -PA (100 °C, 1 h) -NA (2 months) -AA (170 °C, 20 min)) (a) is a comparative graph (b), and Figure 6 is a multi-stage aging (ST (560 ℃, 30min) -PA (100 ℃, 1 h) -NA (2 months) -AA (170 ℃, 20 minutes)) 9M4S (a), 6M6S (b) and 3M10S (c) is a comparison graph of the micro Vickers hardness.

In the case of performing multi-stage aging (ST (560 °C, 30 min) -PA (100 °C, 1 h) -NA (2 months) -AA (170 °C, 20 min)) for 9M4S, 6M6S and 3M10S, FIG. 5 And, as shown in Figure 6, 9M4S, 6M6S, and M10S all the hardness gradually increased with the passage of time during natural aging, it can be seen that all significantly increased after artificial aging. Even in this case, it can be seen that the micro Vickers hardness of 6M6S maintains the largest value for the entire aging period and for a long time after aging.

7 is a TEM photograph of 9M4S, 6M6S and 3M10S after aging according to the experimental conditions of FIG. 1. In the case of aluminum alloy, the strength/hardness is improved due to the formation of precipitates. TEM was used to observe the nano-sized precipitates, and as shown in the upper right of each picture, all were observed in (001) of the base aluminum. During natural aging, it can be seen that the number density of precipitates is significantly lower than that of materials that have not undergone natural aging, and it can be seen that the number density of precipitates is high in the case of preliminary aging materials.

Single aging for 9M4S, 6M6S and 3M10S described above (ST(560°C, 30min)-AA(170°C, 20min)), two-step aging (ST(560°C, 30min)- NA(2 months)-AA( 170 ℃, 20 minutes)) and multi-step aging (ST (560 ℃, 30min) -PA (100 ℃, 1 h) -NA (2 months) -AA (170 ℃, 20 minutes)) As can be seen, in the case of the Al-Mg-Si aluminum alloy, the ratio of Mg and Si is close to 1, and it can be seen that even when pre-aging is performed, the hardness is greatly improved.

That is, it was confirmed as a result of the experiment that the generation of the second cluster that improves the hardness during the artificial aging process of the Al-Mg-Si aluminum alloy is greatly affected by the Mg, Si content and aging conditions. At this time, the second cluster effective for coating reactivity that improves the hardness after artificial aging of the Al-Mg-Si aluminum alloy is largely generated when pre-aging is performed with a ratio close to 1:1 with a large Mg and Si content. , It was confirmed that the harmful first cluster is mainly generated during natural aging.

Therefore, as can be seen from the experiment of one embodiment of the present invention, in the case of manufacturing a 6xxx-based commercial aluminum alloy, it is preferable to synthesize the alloy with Mg/Si close to 1, and to perform heat treatment including pre-aging. Do.

Another embodiment of the present invention provides an Al-Mg-Si alloy heat-treated by the above method and an exterior plate for automobiles comprising the alloy.

The above description of the present invention is for illustrative purposes only, and those of ordinary skill in the art to which the present invention pertains will be able to understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative and non-limiting in all respects. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as being distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the claims to be described later, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims (15)

Determining time and temperature conditions for natural aging of the Al-Mg-Si alloy;
Preparing an Al-Mg-Si alloy by selecting an Mg/Si content ratio according to the determined natural aging time and temperature conditions;
Solutionizing the Al-Mg-Si alloy;
Referencing the solutionized alloy; And
It characterized in that it comprises the step of pre-aging the quenched alloy,
The step of preparing the Al-Mg-Si alloy by selecting the Mg/Si content ratio according to the determined natural aging time and temperature conditions is characterized in that it is determined by a preset database,
In the pre-aging step, the heat treatment method of an Al-Mg-Si alloy, characterized in that performing by determining the time and temperature conditions of the pre-aging according to the determined time and temperature conditions of the natural aging. The method of claim 1,
A heat treatment method of an Al-Mg-Si alloy, further comprising the step of naturally aging the pre-aged alloy according to the determined natural aging time and temperature conditions. The method of claim 1,
The Mg/Si content ratio is a heat treatment method of an Al-Mg-Si alloy, characterized in that 0.3 to 2.5. The method of claim 1,
The Al-Mg-Si alloy heat treatment method of an Al-Mg-Si alloy, characterized in that it contains 0.3 to 1.0wt% Mg and 0.3 to 1.0wt% Si. The method of claim 1,
The time condition for the natural aging is a heat treatment method of an Al-Mg-Si alloy, characterized in that 7 days to 2 months. The method of claim 1,
The temperature condition of the natural aging is a heat treatment method of the Al-Mg-Si alloy, characterized in that 20 to 30 ℃. delete delete The method of claim 1,
The time condition of the pre-aging is a heat treatment method of an Al-Mg-Si alloy, characterized in that 1 minute to 3 days. The method of claim 1,
The heat treatment method of the Al-Mg-Si alloy, characterized in that the temperature condition of the pre-aging is 100 to 110 ℃. The method of claim 1,
Determining the time and temperature conditions of the pre-aging according to the determined time and temperature conditions of the natural aging is determined by a preset database, characterized in that the heat treatment method of the Al-Mg-Si alloy. The method of claim 1,
The step of solutionizing the Al-Mg-Si alloy is a heat treatment method of an Al-Mg-Si alloy, characterized in that the step of 20 to 40 minutes at a temperature range of 550 to 570 ℃. The method of claim 1,
The step of referencing the solution-treated alloy is a heat treatment method of an Al-Mg-Si alloy, characterized in that made at -10 to 0 °C for 30 to 90 seconds. delete delete

Images