Patent ID: 12202416

DESCRIPTION OF EMBODIMENTS

Hereinafter, a structure and operation of the present disclosure will be described in more detail with reference to embodiments of the present disclosure and comparative examples. However, the below description is merely some of the present disclosure, and the present disclosure is not necessarily limited to embodiments described herein.

Therefore, in order to develop the aluminum sheet suitable for the real aluminum, Al—Mn based alloys have been tried. However, elongation is only about 25% even in the case of such an alloy, so that there is a limitation that it is difficult to secure a thin thickness and formability for the real aluminum.

Moreover, even though the aluminum sheet with sufficient requirements for manufacturing the real aluminum is used, an aluminum coil is cut to prepare the aluminum sheet having a desired size and the aluminum sheet should be then transferred to a device for realizing a pattern and color in the manufacturing process. Thus, the yield is very low and high process ratio is inevitably required.

FIG.1is a flowchart of a method for manufacturing an aluminum alloy sheet of the present disclosure, the present disclosure is characterized by a method for manufacturing an aluminum alloy prepared to have a thin-thickness/formability/a strength suitable for manufacturing a real aluminum which will be descried with reference toFIGS.10to15.

As illustrated in the drawing, the method for manufacturing the aluminum alloy sheet includes a step S110of preparing aluminum alloy composition, a step S120of melting the aluminum alloy composition to manufacture cast alloy having a constant initial thickness, a step S130of rolling the cast alloy to make aluminum alloy sheet having a thickness less than the initial thickness, a step S140of heat-treating the aluminum alloy sheet, and a step S150of coiling the aluminum alloy sheet to make an aluminum coil.

The step S110of preparing the aluminum alloy composition is the step of preparing the aluminum alloy composition in which the content of the composition is optimized to improve a thin-thickness and formability, and it is preferable that this aluminum alloy composition contains silicon (Si) of 0.5 wt % or less, ferrum or iron (Fe) of 1.7 to 2.0 wt %, copper (Cu) of 0.5 wt % or less, manganese (Mn) of 2.0 to 6.0 wt %, and remainder of aluminum (Al) and inevitable impurities.

When the content of silicon (Si) of 0.5 wt % or less is added in the aluminum alloy composition, the strength can be improved and corrosion resistance can be increased in a weak acid atmosphere. In addition, intermetallic compound containing silicon (Si) is also effective for increasing hardness. However, when the content of silicon is added too much, there is a restriction on color implementation of an aluminum alloy sheet. In embodiment, the content of silicon (Si) in the aluminum alloy composition is 0.5 wt % or less.

In the aluminum alloy composition, iron (Fe) has a low equilibrium solidification limit with respect to aluminum and is effective for increasing the strength and surface hardness of the alloy, while suppressing a decrease in electric conductivity. Also, since an elastic modulus of an Al—Fe based alloy is increased by about 2.5% per 1 wt % of iron (Fe), iron is effective for improving the elongation of the aluminum alloy sheet. However, when iron is added too much, intermetallic compound may be formed, thereby lowering corrosion resistance in workability of the aluminum alloy. Therefore, it is preferable to add iron within the above-mentioned range.

In the aluminum alloy composition, it is preferable that copper (Cu) of 0.5 wt % or less is added for occurring solid solution hardening of the aluminum alloy and for easily managing the impurities.

In the aluminum alloy composition, manganese (Mn) is added for securing excellent corrosion resistance of the aluminum alloy sheet. If manganese of 2 wt % to 6 wt % is added, there is the effect that solid solution strengthening occurs or polygonal Al6Mn intermetallic compound is formed on a surface, surface hardness of the aluminum alloy sheet is thus enhanced by dispersion strengthening.

In the step S120of melting the aluminum alloy composition to make the cast alloy, in order to manufacture the aluminum alloy sheet, the aluminum alloy composition having the above-described content is melted at a predetermined temperature, the cast alloy is thus manufactured.

Then, the step S130of manufacturing the aluminum alloy sheet is the step of rolling the cast alloy to a predetermined thickness to produce the aluminum alloy sheet. Here, the cast alloy is rolled to a thickness of 0.4 to 0.8 mm to produce the aluminum alloy sheet. Of course, the thickness of the aluminum alloy sheet is not necessarily limited to the above thickness and may be rolled to have an appropriate thickness.

The step S140of heat-treating the aluminum alloy sheet is the step of heat-treating the aluminum alloy sheet to a predetermined temperature in order to improve elongation of the aluminum alloy sheet. The produced aluminum alloy sheet may be heat-treated at a temperature of 300 to 350° C. for 20 to 30 minutes, and more preferably, may be heat-treated at a temperature of 330° C. for 20 minutes.

The below Table 1 represents compositional contents of examples of aluminum alloys and compositional content of the aluminum alloy of the present disclosure. Comparative Examples in Table 1 show the aluminum alloys of A8014 (Comparative Example 1) and A8150 (Comparative Example 2) as the 8000-based aluminum alloy.

TABLE 1Classi-ficationSiFeCuMnMgZnTiAlComparative0.31.2~0.20.2~0.100.100.10Re-Example 11.60.6mainder(A8014)Comparative0.201.2~0.05————Re-Example 21.7mainder(A8150)Example~5.01.7~~5.02.0~———Re-2.05.0mainder

Mechanical properties, such as yield strength, ultimate tensile strength, elongation and ultimate elongation (F-max), of the aluminum alloy sheet before heat treatment, which had the composition of the content of manganese (Mn) in the aluminum alloy composition according to the present disclosure, were measured at a speed of 50 mm/min. according to criteria of ASTM D638, which is the standard measuring method. In order to verify the reproducibility of the data, the results derived from five tests were reviewed, and the results are shown in Tables 2 and Table 3 below.

TABLE 2YieldUltimateClassifi-strengthtensileElongationF-maxn-MaterialcationOrientation(MPa)strength(MPa)(%)El. (%)valueMn10°56.81102.2222.2143.120.1862.0 wt %20°57.00102.5121.3440.080.19130°57.19102.2722.4043.020.19140°56.81102.172.6839.440.19050°—————Average56.95102.2922.1641.420.190190°49.1893.1125.4035.880.197290°48.5193.3324.2829.480.194390°47.4493.2824.9331.280.197490°47.3793.2625.2037.300.195590°48.4293.1824.8629.700.196Average48.1893.2324.9332.730.196

TABLE 3YieldUltimateClassifi-strengthtensileElongationF-maxn-MaterialcationOrientation(MPa)strength(MPa)(%)El. (%)valueMn10°42.6184.5726.1147.890.2126.0 wt %20°42.9586.2528.7647.700.22030°42.7986.2128.9749.480.21440°42.786.1626.1647.540.21150°42.6686.1827.8146.610.212Average42.7485.8727.5647.840.214190°42.6784.0627.6746.240.211290°42.4084.0026.0047.450.207390°42.6482.5928.7048.260.202490°42.6682.5329.6748.240.205590°42.4783.9526.5945.920.211Average42.5783.4327.7347.220.207

After heat-treating the aluminum alloy sheet in which the content of manganese (Mn) was adjusted to 6 wt %, ultimate tensile strength and elongation as the mechanical properties were measured. The results of measurement are shown in Table 4 below. Here, “n-value” shown in Table is a measurement value of a response of metal to cold working, and is usually referred to as the strain hardening exponent.

TABLE 4ClassificationUltimate tensile strength (MPa)Elongation (%)193.2240.896293.8249.49395.1546.433479.9345.22959347.274Average9145.9

As shown in Table 4, it could be confirmed that ultimate tensile strength and elongation of the aluminum alloy sheet after heat treatment were improved compared with those before heat treatment.

In addition, as a result of confirming formability of the aluminum alloy sheet, in which the content of manganese (Mn) was adjusted to 6 wt %, after and before heat treatment with the forming limit diagram (FLD) test as shown inFIG.2, it was confirmed that formability of the aluminum alloy sheet before the heat treatment was similar to that of the aluminum alloy sheet after the heat treatment. Accordingly, from these results, it could be seen that, through heat treatment, the mechanical properties such as yield strength and elongation of the aluminum were improved, whereas formability was maintained.

In addition,FIGS.3A,3B,3C, and3Dis photographs showing formability of the aluminum alloy sheet according to the content of manganese (Mn).

FIG.3Ashows the result of press-forming the aluminum alloy sheet in which the content of manganese (Mn) is 0.5 wt %, into a certain shape,FIG.3Bshows the result of press-forming the aluminum alloy sheet in which the content of manganese (Mn) is 1.5 wt %, into a certain shape,FIG.3Cshows the result of press-forming the aluminum alloy sheet in which the content of manganese (Mn) is 2.5 wt %, into a certain shape, andFIG.3Dshows the result of press-forming the aluminum alloy sheet in which the content of manganese (Mn) is 6.5 wt %, into a certain shape.

From the above results, it could be confirmed that, except only the case in which the content of manganese (Mn) was 2.5 wt % as shown inFIG.3C, a damaged portion or wrinkling may be occurred in the remaining cases ofFIGS.3A,3B, and3D.

FIGS.4A,4B,5A, and5Bare comparative diagrams and photographs showings surfaces of A8150 aluminum alloy sheet and the aluminum alloy according to one embodiment of the present disclosure, respectively, after performing the rolling and hard-facing treatment. In this case,FIGS.4A and5Ashow A8150 aluminum alloy sheet, andFIGS.4B and5Bshow the aluminum alloy sheet according to the present disclosure.

As shown inFIG.4AandFIG.5A, average surface roughness (Ra) of the A8150 aluminum alloy sheet was 0.07 μm, and it could be confirmed that, as the surface hardness was lowered, marks of a rolling roll were generated after performing the rolling and hard-facing treatment. On the other hand, as shown inFIG.4BandFIG.5B, as a result, unlike the A8150 aluminum alloy sheet, the aluminum alloy sheet of the present disclosure had average surface roughness Ra of 0.02 μm and the surface hardness was improved by addition of iron (Fe), so that it was confirmed that surface quality was good even after performing the same rolling and hard-facing treatment.

FIGS.6A,6B,6C,7A, and7Bare comparative diagrams and photographs showings microstructures of surfaces of the aluminum alloy sheets of A8014 (FIG.6A), A3055 (FIG.6B) and A8150 (FIG.6C) and of a surface of the aluminum alloy sheet (FIGS.7A and7B) according to one embodiment of the present disclosure.

It was confirmed that, as compared with the aluminum alloy sheets of A8014, A3055 and A8150 as shown inFIGS.6A,6B, and6C, a size of crystal grain of the aluminum alloy sheet of the present disclosure shown inFIGS.7A and7Bwas very small and smaller than that of the aluminum alloy sheets of A8014, A3055 and A8150. In this case,FIGS.7A and7Brepresent a plane surface and a side face of the aluminum alloy sheet, respectively.

FIGS.8and9are photographs showing the results of detection of energy dispersion for the aluminum alloy sheet according to one embodiment of the present disclosure.

As shown in the drawings, it can be confirmed that polygonal Al—Fe—Mn intermetallic compounds with a micro size of several μm are uniformly distributed in the aluminum alloy sheet of the present disclosure.

Here, the results of detection of energy dispersion are obtained by the energy dispersive spectroscopy (EDS). In the energy dispersive spectroscopy, an electron beam generated from an electron gun of an electron microscope are scanned on a surface of specimen, and various signals are generated by interaction between an electron and an atom of the specimen, and at this time, an x-ray signal, that analyzes chemical components, of various signals generated as above is detected by an energy or wavelength detector to analyze the chemical components contained in the specimen.

As shown in Table 5, the aluminum alloy sheet of the present disclosure proves an example in which the surface quality is improved when the rolling and hard-facing treatment is performed, due to the effect of uniformly distributed fine crystal grains which cause the improved surface hardness.

TABLE 5ClassificationWeight %Atomic %Al50.9267.07Si0.460.58Mn2.441.58Fe45.3228.84O0.871.93Total100.00100.00

In particular, Table 5 specifically shows component of Al—Fe—Mn intermetallic compound of the present disclosure to which iron is added, in which a roll mark occurring phenomenon on a material of 8000 series after performing the rolling and hard-facing treatment can be minimized or avoided. The surface hardness of the material of 8000 series is lowered, through the polygonal crystal grains which have a size of several μm and are uniformly distributed as shown inFIG.8to cause an enhancement of the surface hardness.

On the other hand,FIGS.10to16illustrate a series of continuous processes in which the aluminum coil is made from the aluminum alloy sheet, as previously described, of the present disclosure in the step150inFIG.1, the real aluminum sheet having excellent internal structure is manufactured by directly using the aluminum coil in a coil-to-uncoil process, and a real aluminum sheet is then made and formed into a vehicle interior part such as a door trim garnish.

Referring toFIG.10, a method for manufacturing the aluminum alloy sheet product using the aluminum alloy sheet which can be applied to the coil-to-uncoil process includes a preparing process of S210, a patterning process of S220, a color-coating process of S230, a surface coating process S240, a cutting process of S250and a product-making process of S2620.

Specifically, the preparing process S210, the patterning process S220, the color-coating process S230, the surface coating process S240, the cutting process S250and the product-making process S260are described with reference toFIG.11as below.

As one example, the preparing step S210is performed by setting the aluminum coil as in S211, setting a rolling mill as in S212, setting a vacuum coater as in S213, setting a spray coater as in S214, and setting a press as in S15. Therefore, the preparing process S210means that the aluminum coil1as raw material used for manufacturing the real aluminum is prepared, and a rolling mill3performing the coil-to-uncoil process, a vacuum coater5, a spray coater7and a press9are ready for driving. Particularly, devices for blanking/piercing/injection to be used in the product-making process S260may also be set in the preparing process S210.

In this case, the aluminum coil1is the aluminum alloy sheet which is manufactured by the method for manufacturing the aluminum alloy sheet shown inFIG.1, contains silicon (Si) of 0.5 wt % or less, iron (Fe) of 1.7 to 2.0 wt %, copper (Cu) of 0.5 wt % or less, manganese (Mn) of 2.0 to 5.0 wt % and remainder of aluminum (Al) and inevitable impurities, is heat-treated and has a coil shape to be capable of continuously supplied.

As one example, in the patterning step S220, the rolling mill3to which the aluminum coil1is connected is operated as in S221and as in S222, a three-dimensional pattern roller3-1is operated to allow a three-dimensional design (or shape) of the roller is formed on the aluminum coil1while the aluminum coil passes though the rolling mill3. Particularly, the three-dimensional pattern roller3-1rolls the aluminum coil with a pressure of 2500 to 4000 kg/cm2at a speed of 5 to 10 Hz to form a three-dimensional pattern.

Further, various kinds of three-dimensional pattern designs (or shapes) may be applied by changing the kind of three-dimensional pattern roller3-1, if necessary.

As a result, in the patterning step S220, the aluminum coil1passing through the rolling mill3is transformed into a patterned coil1-1having a three-dimensional pattern is made from as in S223.

FIGS.12A and12Billustrates the patterned coil1-1having a three-dimensional pattern formed by rolling the aluminum coil1having a thickness of 0.6 mm at a rolling speed of 8 Hz and a pressure of 3,500 kg/cm2.

As one example, in the color-coating process S230, the vacuum coater5to which the patterned coil1-1exiting the rolling mill3is connected is operated as in S231, and a vacuum chamber5-1is operated to form a PVD coating layer and impart the color on a surface of the patterned coil1-1during coiling/uncoiling process in which the patterned coil1-1is coiled and uncoiled by a pair of roller in the vacuum chamber5-1as in S232.

In this case, the vacuum chamber5-1is a PVD chamber for forming the PVD (physical vapor deposition) coating layer on the surface of the patterned coil1-1to impart the color, and in the PVD chamber under an inert gas atmosphere, the PVD coating layer containing Ti and TiC is formed on the surface of the patterned coil1-1under the conditions of a temperature of 70 to 120° C. and a pressure of 3.0×10−3to 1.2×10−2Torr, so that the color is realized on a surface of the patterned coil.

As a result, in the color-coating process S230, the patterned coil1-1is transformed into a colored coil1-2, as in S233, through a first coating process. In this case, a process in which the aluminum coil1passes through the three-dimensional pattern roller3-1of the rolling mill3and is transformed into the patterned coil1-1is continued.

FIG.13shows an example in which an electrochemical film forming method called the anodizing which realizes the color for improving a texture of metal, and shows that when the aluminum alloy sheet to which this anodizing method is applied is formed to have a desired shape in a subsequent process, a crack of an anodizing layer is generated in an edge portion of the pattern.

On the other hand,FIG.14shows the PVD coating layer on which the colored is imparted by the PVD method as in the present disclosure, and shows that no crack is generated in the PVD coating layer even after forming the flexible metal coating layer with the press.

As one example, in the surface coating process S240, the spray coater7to which the colored coil1-2exiting the vacuum coater5is connected is operated as in S241, and a wet spray injector7-1is operated as in S242to form a nano ceramic coating (NCC) layer on a surface of the colored coil1-2during an uncoiling process in which the colored coil is uncoiled by the roller.

In this case, the spray coater7employs an NCC method and coats a nano ceramic paint, including an inorganic binder and ceramic powders, on the surface of the colored coil1-2, which is colored with the PVD coating layer, by a wet coating method to form a protective coating layer. Any one selected from a gravure coating, a microgravure coating, a capillary coating and a bar coating may be used as the above wet coating method, and the present disclosure is not necessarily limited thereto.

As a result, in the surface coating step S240, the colored coil1-2is transformed into a surfacing coil1-3by a second coating process as in S243. In this case, the process in which the aluminum coil1is transformed into the patterned coil1-1while passing through the three-dimensional pattern roller3-1of the rolling mill3, and the patterned coil is transformed into the colored coil1-2while passing through the vacuum chamber5-1of the vacuum coater5is continued.

As one example, in the cutting process S250, the press9through which the surface coil1-3exiting the spray coater7passes is operated as in S251, and a punch9-1is operated as in S252to cut the surfacing coil1-3to have a predetermined sheet size.

As a result, in the cutting step S250, a real aluminum sheet10is made from the surfacing coil1-3as in253. In this case, the process in which the aluminum coil1is transformed into the patterned coil1-1while passing through the three-dimensional pattern roller3-1of the rolling mill3, the patterned coil is transformed into the colored coil1-2while passing through the vacuum chamber5-1of the vacuum coater5, and the colored coil is transformed into the surfacing coil1-3while passing through the wet spray injector7-1of the spray coater7is continued.

FIGS.15A and15Bshows the results of scratch-resistance test for the real aluminum sheet10.

FIG.15Ashows that a noticeable scratch mark is formed on the anodizing layer of the aluminum sheet, whereasFIG.15Bshows that a light mark that is formed on the PVD coating layer and the protective coating layer of the real aluminum sheet10.

In this case, the scratch resistance test may be performed by scraping the surface of the sheet with a scratch-resistant scratcher having a pointed tip.

As one example, in the product-making process S260, a blanking of S261, a piercing of S262, and an injection of S263are applied to the real aluminum sheet10, so that a vehicle internal part is made from the real aluminum sheet10as in S264.

FIG.16shows an example in which a door trim garnish100applied to a door trim100-1constituting a door is made from the real aluminum sheet10.

As described above, the aluminum coil1of the aluminum alloy sheet according to the present disclosure can improve the surface hardness of the sheet even after rolling to manufacture the real aluminum sheet having high quality and high formability. In addition, the method of manufacturing the real aluminum sheet disclosed in the present disclosure has the effect that Since a pattern production, color implementation and a surface process are performed in a continuous process by the coil-to-uncoil method using the shape of the aluminum coil1, it is possible to form the real aluminum sheet10more easily and quickly than other surface treatment methods such as a screen printing or an anodizing, and physical properties such as the gloss degree, scratch resistance, and the like are excellent.

The real aluminum sheet10provided in the present disclosure and having the above characteristics can be widely applied to various fields such as the sheet for vehicle interior part, the exterior sheet, the packaging material, and the like.

In the real aluminum manufacturing method of the present disclosure, since the real aluminum is manufactured by using the aluminum coil of the aluminum alloy sheet having a thin-thickness, formability and a strength and is then cut to have a sheet size, It is possible to batch the coil-to-uncoil process which can achieve high yield and cost reduction. Especially, physical properties of the aluminum alloy sheet suitable for the real aluminum are realized by optimization of the contents of silicon (Si), iron (Fe), copper (Cu) and manganese (Mn) and heat treatment, so that it is possible to overcome limitation of technical difficulties.

In addition, the aluminum alloy sheet manufactured according to the method for manufacturing the aluminum alloy sheet, which has improved formability, for a vehicle interior part according to the present disclosure has an effect that deepness and surface roughness are enhanced by 30 times or more due to a step difference in pattern as compared with the A8150 aluminum material.

In addition, the method of forming the aluminum alloy sheet of the present disclosure is suitable for realizing a metal texture in terms of light resistance and scratch resistance as compared with the anodizing method, and since a crack does not occur in the edge portion during press forming, there is an improved effect as compared with the existing forming process.

Although the present disclosure has been described with a focus on novel features of the present disclosure applied to various embodiments, it will be apparent to those skilled in the art that various deletions, substitutions, and changes in the form and details of the apparatus and method described above may be made without departing from the scope of the present disclosure. Accordingly, the scope of the present disclosure is defined by the appended claims rather than by the foregoing description. All modifications within the equivalent scope of the appended claims are embraced within the scope of the present disclosure.