KR100194139B1 - Aluminum alloy containing rare earth metal or mesh metal and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a high-strength, high-molding alloy and a method for manufacturing the same, which can be applied to transporting solvents and other Al structures including automobiles, the aluminum alloy of the present invention is 4.5-12.0% by weight of Mg, 0.001-0.5% by weight The rare earth metal or misch metal, and the remaining Al, characterized in that the manufacturing method of the aluminum alloy of the present invention is 4.5-12.0% by weight of Mg, 0.001-0.5% by weight of rare earth metal, and the remaining Al The ingot or slab obtained by dissolving and casting the molten metal of the Al alloy constituted is maintained at 400 ° C.-600 ° C. for 8 hours or more, and then quenched by quenching or more by air cooling or the like, followed by rolling.

Description

Aluminum alloy containing rare earth metal or mesh metal and manufacturing method thereof

The present invention relates to an aluminum alloy containing rare earth metal or Misch Metal, and a method of manufacturing the same, and more particularly, having high strength and high formability for application to a vehicle body and other aluminum structures including automobiles. A light weight Al-Mg alloy and a method of manufacturing the same.

Recently, many researches have been conducted on Al alloys for automobiles, which have infinite market potential, due to their development potential and cost reduction. This is not only the main purpose of reducing fuel consumption due to light weight, but also the increase in recovery rate according to the material characteristics and environmentally friendly benefits, the demand for the development of Al alloys as various structural materials for automobiles is further maximized.

However, it is impossible to replace Al alloy completely because of the relatively high production cost, relatively low strength and formability compared to steel. In particular, since there was considerable difficulty in development and difficulty in terms of formability rather than strength, no practical application has been made to date.

In addition, even in the case of the most representative Al-Mg alloy among automotive Al alloys developed so far, when the amount of Mg, which is a main additive element, is more than 7% by weight, there are serious problems in manufacturing such as casting, heat treatment, etc. In the case of producing an alloy of high concentration Mg Mg is more than 7% by weight caused by the well-known manufacturing method can not exhibit the material properties, when the addition of a special element could not take advantage of the excellent moldability of the Al alloy.

The present invention has been made in view of the above-mentioned problems of the conventional Al-based alloy, and provides an aluminum alloy containing a rare earth metal or a mismetal which can be applied to the vehicle body.

It is still another object of the present invention to provide a method for preparing an Al alloy containing rare earth metal or mismetal having high strength and high formability.

The present invention relates to an aluminum alloy composed of Mg4.5-16.0% by weight, rare earth metal 0,001-0.5% and a rare metal composed mainly of the rare earth metal, and the rest being composed of aluminum.

In the aluminum alloy of the present invention, 0.01 to 1.0% by weight, 0.01 to 0.3% by weight, 0.01 to 0.5% by weight, 0.01 to 0.5% by weight, 0.01 to 0.5% by weight of Ti, 0.01 to 1.0% by weight of Cu, and 0.01 to 1.0% of Zn, which constitute a rare earth metal. One type or two types or more may be added individually or in combination among the weight% and Be 0.001-0.5 weight%.

In addition, instead of the rare earth metal of the present invention, a misch metal composed of rare earth metal elements may be used.

The method for producing a high-strength high-forming aluminum alloy of the present invention is more than air cooling (cooling at room temperature) after homogenizing the ingot or slab obtained by melting and casting in a conventional manner at 400 ℃-600 ℃ for 8 hours or more. By performing a quenching (gold-cooling) treatment at a cooling rate, it is subjected to a hot rolling or cold rolling process, and directly processed (such as cutting) by ingot and slab directly to a predetermined thickness after the composite treatment It relates to a method of obtaining a predetermined thickness.

The present inventors added rare earth metals such as Sc, La, Ce, Y, Hf, Pd, and Nd to overcome the fatal phenomena such as extreme draw reduction and thermal embrittlement due to the high concentration of Mg when preparing Al-Mg alloy. It succeeded in obtaining the high moldability at the time of processing by correcting the moldability fall value to a suitable value. In addition, instead of the rare earth metal, it is also possible to add a Misch Metal composed of rare earth elements such as La, Ce, Nd, and Pr, which are relatively inexpensive.

FIG. 1 is a graph showing the change in mechanical properties of Al-Mg alloy containing high concentration of Mg (more than 7% by weight) when aged at 150 ° C.

2 is a graph showing the change of mechanical properties during aging treatment at 150 ° C. when La is added to an Al-Mg alloy containing a high concentration of Mg (7 wt% or more).

3 is a graph showing changes in mechanical properties during aging at 150 ° C. when Misch Metal is added to La in place of La.

Figure 4 is a photograph of the casting structure observed with an optical microscope when La and Ce is added to the alloy.

5 is a graph showing a change in mechanical properties according to cooling conditions when La and Ce are added to the alloy.

FIG. 6 is a graph showing the results of high temperature tensile test when La and Misch Metal are added to the alloy.

Hereinafter, the components and the ratio of the high forming, high strength Al alloy according to the present invention will be described in detail.

Al-Mg alloy, which is the basic material of the present invention, is an alloy that obtains solid solution strengthening and processing strength according to the addition of Mg, and the amount of Mg is a major element for imparting strength of the present invention. In particular, in order to use as a plate for transport equipment, at least 4.5% Mg must be added to maintain the minimum strength. However, when Mg is added in an amount of about 7.0% by weight or more, serious cracking occurs during manufacturing and processing, which greatly affects the production of the product. In the present invention, by adding the rare earth element, it was designed to have excellent moldability even in a high concentration Mg alloy of 7.0% by weight or more, and succeeded in increasing the degree of weight reduction.

In addition, when 16% by weight or more of Mg is added, the strength increases but the workability deteriorates. In the present invention, the Mg content is in the range of 4.5-16.0% by weight.

Mn is an element necessary for inducing Mg and Si-based compounds to be uniformly finely precipitated, increasing strength upon heating after molding, and obtaining microcrystal grains. If the Mn content is 0.01% by weight or less, there is little effect. If the Mn content is 1.0% by weight or more, the Mn-based compound is made as much as possible to lower the elongation. Therefore, the composition range of Mn is 0.01-1.0 weight%.

Be is a microadditive element that improves castability in Al alloys. When Be is added in a small amount during casting, Be can not only prevent the oxidation of the molten metal but also obtain a correct viscosity, thereby obtaining a sound casting structure. In addition, Be-particles produced by the addition of Be has the effect of obtaining the fine grains in the subsequent heat treatment step. The composition range of Be is preferably 0.001-0.5% by weight.

Cu and Zn are the most representative age hardening induction additives in Al alloys, which can not only improve the strength by aging heat treatment but also improve the bendability, and in the case of Zn, luster bands Additional effects of suppression can also be obtained, but when added in an amount of 1.0 wt% or more, rapid ductility and moldability decreases, and a fatal disadvantage of increasing stress and corrosion resistance is also observed, and an amount of 0.01 wt% or less can be added. In that case, you can not expect the effect. Therefore, the composition of Cu and Zn is 0.01-1.0 weight%.

Ti and Zr are disperse phases formed by the addition of these elements, which can not only increase the strength but also increase the particle fineness, thereby obtaining additional strength. However, when the added amount of these elements exceeds 0.3% by weight, the formability is significantly reduced by the intermetallic compound particles produced by them. Therefore, the content of Ti and Zr components is 0.01-0.3 wt%.

Rare earth elements such as Sc, Y, hf, La, Ce, Pd, and Nd are the most characteristic addition elements in the present invention. When these are added to Al-Mg alloys, they can be expected to have an additional solid solution effect and high concentration of Mg. It can solve the segregation problem during casting, and it has the effect of preventing the deterioration of formability due to grain embrittlement, enabling high concentration of Mg addition, and increasing the thermal stability at high temperature to improve the high temperature melting power of the present invention. It is a characteristic element to increase, and in the case of Sc, it is possible to enhance the precipitation strengthening effect by precipitating Al₃Sc phase, as well as an element that enables superplasticity by predetermined heat treatment in Al-Mg alloy with high concentration of Mg. Therefore, the composition range of the rare earth element is 0.001-0.5% by weight.

In addition, in the case of the Misch Metal composed of these rare earth elements, the rare earth elements are complex, so that the characteristics of the rare earth elements can be improved in various ways, and the cost is relatively economical compared to the rare earth metals. This is a cheap and optimal additive. Therefore, the composition range of the mash metal composed of rare earth elements such as Ce, LA, Pd, and Nd is also 0.001-0.5% by weight.

The following describes in detail the manufacturing method of the present invention.

The ingot or slab obtained by melting and casting in a conventional manner is subjected to heat treatment at 400 ° C.-600 ° C. for about 8 hours or more, and then quenched by quenching it with air cooling, water cooling, or ice water without using a conventional furnace cooling. By increasing the heat treatment, not only the homogenizing treatment but also the complex heat treatment which simultaneously obtains the solution treatment effect. Such treatment not only has the effect of homogenization treatment to remove segregation of various elements appearing during casting, but also has an additional effect of suppressing precipitation of various precipitated phases which have an adverse effect on formability by quenching at high temperature. Because it can.

Particularly, when Mg is added in an amount of more than 7% by weight, the segregation of Mg becomes severe, and accordingly, the above-described heat treatment should be sufficiently performed for at least 8 hours to obtain a homogenizing effect. In particular, such a composite heat treatment is a characteristic manufacturing process of the present invention to increase the possibility of continuous production of Al alloy sheet material. Then, in order to fabricate the treated ingot or slab into a plate of appropriate size, first, hot rolling is performed between 250 and 450 ° C., in which case it is relatively hot rolled in case of 250 ° C. as compared with the conventional case. In the case of low temperature, but in the present invention, since the thermal stability is shown to be relatively close to 250 ° C., the minimum temperature range of hot rolling is lowered by 250 ° C. in consideration of economical efficiency. The plate rolled to an appropriate size is subjected to cold rolling again to obtain a high strength, high forming Al plate having a predetermined thickness. After the solution treatment in the temperature range of 350 ℃ to 550 ℃ to obtain the proper properties and quenched and then aged in the range of -30 ℃ to 300 ℃ to prepare a high-strength, high-forming Al alloy for the vehicle body. This process is adjusted to take each stage as continuously as possible considering economics.

In the second method, if the size of the ingot or slab is relatively small, after performing the combined heat treatment combining the homogenization treatment and the solution treatment, the hot rolling process is omitted, and if the size is large, the hot process is performed. It is processed by cutting, etc., and then processed into a shape having a predetermined size or width: thickness ratio, and then cold-rolled to save energy during the hot rolling process and at the same time to continuously cast non-heat treated Al alloy sheet. By maximizing economic benefits. This is because the present invention exhibits the maximum ductility and formability when there is almost no precipitated phase, and in the case of ingots or slabs having a small size, the present invention exhibits optimal strength and formability by performing cold rolling immediately after the composite heat treatment. After quenching and quenching at a temperature range of 350 ℃ to 550 ℃ in order to obtain the properties of a special purpose it is characterized in that it is aged at -30 ℃-300 ℃. In addition, like the first method, each process proceeds continuously to maximize economic benefits.

The present invention will be described in more detail with reference to the following Examples.

Example 1

Ingots or slabs obtained by dissolving and casting aluminum added with 7% by weight of Mg and 0.1% by weight of La were subjected to heat treatment at 480 ° C for 24 hours, and then quenched with ice water. After cold rolling again to obtain a predetermined thickness, the solution was quenched at 450 ° C., quenched, and aged at 150 ° C. to prepare an Al alloy. Maximum tensile strength, yield strength and elongation were measured and shown in FIG. 2. In addition, a tensile test was performed during the aging treatment at a high temperature of 200 ° C. or higher, and the results are shown in FIG. 6.

Example 2

An ingot or slab obtained by dissolving and casting 8% by weight of Mg and 0.3% by weight of La-added aluminum in a conventional manner was treated in the same manner as in Example 1 to prepare an Al alloy. Maximum tensile strength, yield strength and elongation were measured and shown in FIG. In addition, a tensile test was performed during the aging treatment at a high temperature of 200 ° C. or higher, and the results are shown in FIG. 6.

Example 3

An ingot or slab obtained by dissolving and casting aluminum added with 10% by weight of Mg and 0.3% by weight of La in a conventional manner was treated in the same manner as in Example 1 to prepare an Al alloy. The cast structure was observed with an optical microscope, and the photograph is shown in FIG.

Comparative Example 1-3

Ingot obtained by dissolving and casting aluminum in which 7% by weight of Mg (Comparative Example 1), 8% by weight of Mg (Comparative Example 2), and 10% by weight of Mg (Comparative Example 3) were respectively Alternatively, the slabs were heat treated at 480 ° C. for 24 hours. After performing a conventional furnace cooling and hot rolling at 350 ° C., it was cold rolled again, solution treated at 450 ° C., quenched, and aged at 150 ° C. to prepare Al alloy. The microstructure of the cast structure was observed in FIG. 4, and the maximum tensile strength, yield strength and elongation were measured and shown in FIG.

In addition, a tensile test was performed during the aging treatment at a high temperature of 200 ° C. or higher, and the results are shown in FIG. 6.

As can be seen from the results of FIGS. 1 and 2, when Mg is added at a high concentration to increase the amount of Mg to increase the strength, that is, when Mg of 7% by weight or more is added as in Comparative Examples 1-3. In the heat exposure (aging treatment) of about 150 ° C., a sudden drop in stretching is also observed. However, in the case of aging treatment when 0.1-0.3% by weight of La was added to Al-Mg alloy as in the embodiment of the present invention, the strength increased with a slight increase, especially in the elongation (at least 8 compared to the case of no additive alloy). It shows excellent thermal stability.

Example 4

Ingots or slabs obtained by dissolving and casting aluminum added with 10% by weight of Mg and 0.1% by weight of misch metal in a conventional manner were treated in the same manner as in Example 1 to prepare an Al alloy. The maximum tensile strength, yield strength and elongation were measured and shown in FIG. 3 in comparison with Comparative Example 3, which is not added, and Example 3, in which 0.3 wt% of La was added. In addition, a tensile test was performed during the aging treatment at a high temperature of 200 ° C., and the results are shown in FIG. 6.

As can be seen from the results of FIG. 3, in the case of an alloy manufactured by the conventional method and composition, the thermal exposure (aging treatment) for about 10 hours at 150 ° C. showed not only a rapid decrease in elongation but also a decrease in strength. Likewise, when Misch Meatal composed of rare earth metals is added, the elongation is maintained at the time of thermal exposure (aging treatment), and the elongation (at least 30% elongation at 150 x 100 hours) is maintained.

As a result of the high temperature tensile test of FIG. 6, when Mg and La were added to Al-Mg alloys containing high concentrations of Mg (Mg 7% by weight or more) of Examples 1, 2, and 4, Although more was added, the strength and elongation at each temperature (200 ° C, 250 ° C, 350 ° C) increased compared to the alloys without them, in particular the elongation was at least 20% to 50% higher than that of non-added alloys. An increase rate of more than% indicates that the present invention is an excellent material that overcomes the thermal withdrawal property, which is a fatal disadvantage in the high concentration of Mg.

Example 5

An Al alloy was prepared in the same manner as in Example 3 by adding 0.3 wt% Ce instead of 0.3 wt% La. The cast structure was observed with an optical microscope, and the photograph is shown in FIG. 4, and the maximum tensile strength, yield strength, and elongation were measured and shown in FIG. 5 in comparison with Example 3. FIG.

From the structure photograph of FIG. 2, it can be seen that the addition of rare earth elements such as La and Ce shows the effect of miniaturization of the cast structure. This resulted in a considerably superior effect on strength and ductility by obtaining a metal structure having finer crystals in subsequent heat treatment.

[Comparative Example 4]

Ingots or slabs obtained by dissolving and casting aluminum added with 10% by weight of Mg and 0.3% by weight of La in a conventional manner are heat-treated at 480 ° C for 24 hours, except that they are furnace-cooled in a furnace instead of quenching with ice water. And the same process as in Example 3 to prepare an Al alloy. Maximum tensile strength, yield strength and elongation were measured and shown in FIG. 5 in comparison with Example 3.

[Comparative Example 5]

Ingots or slabs obtained by dissolving and casting aluminum added with 10% by weight of Mg and 0.3% by weight of Ce are subjected to heat treatment at 480 ° C for 24 hours, except that they are quenched in a furnace instead of quenching with ice water. And Al alloy was prepared in the same manner as in Example 5. Maximum tensile strength, yield strength and elongation were measured and shown in FIG. 5 in comparison with Example 5. FIG.

In the graph of FIG. 5, the effects on mechanical properties such as strength and elongation are better when La is added than when Ce is added, and when quenched with ice water is much better than when it is cold, the effect of the composite heat treatment Was found to be large.

As described above, it can be seen that the alloy sheet of the present invention is a high-strength, high-forming Al alloy having excellent thermal stability that overcomes the thermal withdrawal characteristic, which is a fatal disadvantage of the existing Al-Mg alloy, and the manufacturing method of the present invention provides the characteristics of the present invention. It can be seen that it can be maximized.

Claims (2)

6-16.0 wt% Mg, Mn 0.01-1.0 wt%, Cr 0.01-0.3 wt%, Zr 0.01-0.5%, Ti 0.01-0.5 wt%, Cu 0.01-1.0 wt%, Zn 0.01-1.0 wt% and Be 0.001-0.1% by weight and one or two or more selected from the rare earth metal group are contained alone or in combination with 0.001 to 0.1% by weight, and the rest contains rare earth metals or misch metals, which are composed of Al. Aluminum alloy. In manufacturing an alloy sheet having high molding and high strength and light weight, obtained by dissolving and casting a molten Al alloy composed of 6-16.0 wt% Mg, 0.001-0.1 wt% rare earth metal and the remaining Al. After maintaining the ingot or slab at 40 ° C.-600 ° C. for at least 8 hours, quenching and quenching by quenching at least with air cooling, and further heat-treating and quenching at 350-550 ° C. after the rolling process, and then -30-300 ° C. Method for producing an aluminum alloy containing rare earth metal or mismetal, characterized in that the aging treatment in.