ALUMINUM ALLOY MATERIAL HAVING IMPROVED CORROSION RESISTANCE FOR GAS TUBE IN EGR COOLER

Abstract

The present invention relates to an aluminum alloy material for a gas tube included in an exhaust gas recirculation (EGR) system. More specifically, the present invention relates to an aluminum alloy material for a gas tube, the an aluminum alloy material including: a core material; an outer material cladded onto a single surface or opposite surfaces of the core material; and an intermediate material cladded between the core material and the outer material to prevent magnesium from diffusing into the outer material from the core material, wherein the core material includes copper (Cu), silicon (Si), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), and aluminum (Al). According to the present invention, the aluminum alloy material for a gas tube in an EGR cooler is excellent in strength and corrosion resistance, thereby extending the life span of gas tube even under extreme conditions.

Claims

1. An aluminum alloy material for a gas tube in an EGR cooler, the aluminum alloy material comprising: a core material; an outer material cladded onto a single surface or opposite surfaces of the core material; and an intermediate material cladded between the core material and the outer material to prevent magnesium from diffusing into the outer material from the core material, wherein the core material includes copper (Cu), silicon (Si), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), and aluminum (Al).

2. The aluminum alloy material of claim 1, wherein the core material includes 0.4 wt. %-0.6 wt. % of copper (Cu), 0.6 wt. %-0.8 wt. % of silicon (Si), 0.4 wt. %-0.6 wt. % of iron (Fe), 0.3 wt. %-0.4 wt. % of magnesium (Mg), 0.4 wt. %-1.1 wt. % of manganese (Mn), 04 0.1 wt. %-0.2 wt. % of titanium (Ti), and a remainder of aluminum (Al).

3. The aluminum alloy material of claim 1, wherein the intermediate material is A3003 aluminum alloy or A0140 aluminum alloy.

4. The aluminum alloy material of claim 1, wherein the outer material is A4045 aluminum alloy.

5. The aluminum alloy material of claim 1, wherein the aluminum alloy material has a total thickness of 0.7 mm-2.0 mm, the outer material occupies 3%-8% of the total thickness of the aluminum alloy material, and the intermediate material occupies 3%-8% of the total thickness of the aluminum alloy material.

Description

DESCRIPTION OF DRAWINGS

[0020] FIG. 1 is a perspective view illustrating an EGR cooler according to the related art;

[0021] FIG. 2 is a cross-sectional perspective view illustrating the EGR cooler according to the related art;

[0022] FIG. 3 is a cross-sectional view illustrating a material for a gas tube in the EGR cooler according to the related art;

[0023] FIG. 4 is a cross-sectional view illustrating an aluminum alloy material for a gas tube in an EGR cooler according to a first embodiment of the present invention;

[0024] FIG. 5 is a cross-sectional view illustrating an aluminum alloy material for a gas tube in an EGR cooler according to a second embodiment of the present invention;

[0025] FIG. 6 is a photograph illustrating an apparatus for testing for corrosion resistance in Test Example 1 according to the present invention;

[0026] FIG. 7 is a graph illustrating a condensate circulation cycle obtained in Test Example 1 according to the present invention;

[0027] FIG. 8 shows photographs respectively illustrating a cross section of Comparative Example 1 before and after carrying out Test Example 1 according to the present invention; and

[0028] FIG. 9 shows photographs respectively illustrating a cross section of Example 1 before and after carrying out Test Example 1 according to the present invention.

MODE FOR INVENTION

[0029] Hereinbelow, a material for a gas tube in an EGR cooler according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0030] The present invention relates to an aluminum alloy material 100 for a gas tube equipped in an EGR cooler allowing heat-exchange between a high-temperature exhaust gas and a low-temperature coolant to cool the exhaust gas and transferring the exhaust gas to an exhaust gas recirculation (EGR) system.

[0031] As illustrated in FIG. 4, the aluminum alloy material according to the first embodiment of the present invention includes: a core material 110; outer materials 130 cladded onto opposite surfaces of the core material 110; and intermediate materials 120 each cladded between the core material 110 and the outer materials 130 to prevent magnesium from diffusing into the outer materials 130 from the core material 110. The core material 110 includes copper (Cu), silicon (Si), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), and aluminum (Al).

[0032] The core material 110 is to maintain main physical properties of a clad material and to impart high strength and high corrosion resistance, and includes copper (Cu), silicon (Si), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), and aluminum (Al). A composition ratio here is preferably 0.4 wt. %-0.6 wt. % of copper (Cu), 0.6 wt. %-0.8 wt. % of silicon (Si), 0.4 wt. %-0.6 wt. % of iron (Fe), 0.3 wt. %-0.4 wt. % of magnesium (Mg), 0.4 wt. %-1.1 wt. % of manganese (Mn), 0.1 wt. %-0.2 wt. % of titanium (Ti), and the remainder of aluminum (Al).

[0033] That is, the core material 110 according to the present invention is obtained by improving a composition of the conventional A3003 aluminum alloy. As shown in Table 1 below, the core material 110 is increased in the copper content compared with the basic composition of A3003 aluminum alloy to reinforce the strength and corrosion resistance. In addition, magnesium is added to increase the strength, and titanium is added to induce uniform corrosion.

TABLE-US-00001 TABLE 1 Composition of the core material Composition (wt. %) Category Cu Si Fe Zn Mg Mn Ti Al A3003 0.05- 0.6 0.7 0.1 0.1- Rem. 0.2 1.5 Core material 0.4- 0.6- 0.4- 0.3- 0.4- 0.1- Rem. of the present 0.6 0.8 0.6 0.4 1.1 0.2 invention

[0034] In more detail, as can be seen in Table 1, the copper content is increased from 0.05 wt. %-0.2 wt. % to 0.4 wt. %-0.6 wt. % such that Al.sub.2Cu is precipitated, leading to improving of the strength, and corrosion potential is increased, leading to improving of the corrosion resistance. In addition, 0.3 wt. %-0.4 wt. % of magnesium is added such that Mg.sub.2Si is precipitated, thereby improving the strength due to age hardening. In addition, 0.1 wt. %-0.2 wt. % of titanium is added such that the behavior of corrosion is changed, which means that uniform corrosion is induced rather than local corrosion. Furthermore, the iron content is lowered to 0.4 wt. %-0.6 wt. % according to the present invention because the higher the iron content, the lower the corrosion resistance, and zinc is not contained.

[0035] That is, compared with the conventional A3003 aluminum alloy, the core material 110 according to the present invention contains magnesium and titanium, the higher copper content, the lower iron content, and no zinc, thereby remarkably improving the strength and corrosion resistance.

[0036] The outer materials 130 cladded on the opposite surfaces of the core material 110 are brazing filler materials provided for brazing. The outer materials 130 may be A4045 aluminum alloy which is the same as the conventional gas tube material, and may be various aluminum alloys disclosed in the related art.

[0037] Table 2 below shows a composition of A4045 aluminum alloy.

TABLE-US-00002 TABLE 2 Composition of A4045 aluminum alloy Composition (wt. %) Category Si Fe Cu Mn Mg Zn Ti Al A4045 9.0-11.0 0.8 0.30 0.05 0.05 0.10 0.20 Rem.

[0038] According to the present invention, the intermediate materials 120 are provided between the core material 110 and the outer materials 130. The intermediate materials 120 are to prevent magnesium from diffusing from the core material 110. Magnesium contained to improve the strength of the core material 110 may diffuse into the outer materials 130 so that some portions may be unbonded in the brazing process, thereby degrading bonding of the material 100. Therefore, when the intermediate materials 120 preventing diffusion of magnesium are cladded between the core material 110 and the outer materials 130, magnesium is prevented from diffusing into the outer materials 130 from the core material 110 and thus unbonding is prevented.

[0039] Here, aluminum alloy containing no magnesium, most preferably, A3003 aluminum alloy, may be used as the intermediate materials 120. Since A3003 aluminum alloy has been described in Table 1 above, the description thereof will be omitted here. Alternatively, A0140 aluminum alloy, which contains a small amount of magnesium but prevents magnesium from diffusing from the core material 110, may be used as the intermediate materials 120. A composition of A0140 aluminum alloy is shown in Table 3 below. However, A3003 aluminum alloy is preferably to be used to effectively prevent diffusion of magnesium.

TABLE-US-00003 TABLE 3 Composition of A0140 aluminum alloy Composition (wt. %) Category Si Fe Cu Mn Mg Zn Ti Al A0140 0.34-0.5 0.30 0.05 0.10 0.05 0.10 0.05 Rem.

[0040] As described above, since the aluminum alloy material 100 for a gas tube is composed of the core material 110 having improved corrosion resistance and strength, the intermediate materials 120 preventing magnesium from diffusing from the core material 110, and the outer materials 130 provided for brazing, the aluminum alloy material 100 has excellent strength and corrosion resistance but also has excellent bonding so that the aluminum alloy material 100 is suitable for a gas tube in an EGR cooler.

[0041] In the present invention, a process of manufacturing a gas tube using the material 100 is performed by well-known methods in the art such as cladding, roll forming, bonding, and the like, and thus the detailed description thereof will be omitted.

[0042] The aluminum alloy material 100 is preferably 0.7 mm-2.0 mm thick. This is because when the aluminum alloy material 100 is too thin, the heat exchange efficiency is increased but the replacement cycle of a gas tube is shortened which is not good in terms of a cost aspect, and when the thickness is too thick, the heat exchange efficiency is reduced. The thickness of the outer materials 130 is preferably 3%-8% of the total thickness of the material, and the same applies to the intermediate materials 120. This is because when the thickness of the outer materials 130 or the intermediate materials 120 occupies less than 3% of the total thickness, the materials cannot function properly, and when the thickness of the outer materials 130 or the intermediate materials 120 occupies over 8% of the total thickness, it is not good in terms of cost due to the thickness being more than necessary, and the corrosion resistance and strength are adversely affected. Here, the thickness of the outer materials 130 is sum of the thickness of each of the outer materials 130 provided on the opposite sides, and the thickness of the intermediate materials 120 is sum of the thickness of each of the intermediate materials 120 provided on the opposite sides. It is preferable to clad the outer materials 130 to the same thickness on each side, and the same applies to the intermediate materials 120 in order to improve the corrosion resistance.

[0043] As illustrated in FIG. 5, an aluminum alloy material according to a second embodiment of the present invention includes: a core material 110; an outer material 130 cladded onto a single surface of the core material 110; and an intermediate material 120 cladded between the core material 110 and the outer material 130 to prevent magnesium from diffusing into the outer material 130 from the core material 110. The core material 110 includes copper (Cu), silicon (Si), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), and aluminum (Al). That is, the intermediate material 120 and the outer material 130 are cladded only onto a single surface of the core material 110. The aluminum alloy material 100 having the structure also has remarkably improved corrosion resistance due to a composition of the core material 110.

[0044] The material 100 here is roll-formed to construct a tube such that the core material 110 is positioned at the inner side of a gas tube, and the outer material 130 is positioned at the outer side of the gas tube.

[0045] Here, the core material 110, the intermediate material 120, and the outer material 130 have been described above, the description thereof will be omitted.

[0046] Hereinbelow, the present invention will be described more specifically with reference to Example.

EXAMPLE 1

[0047] Aluminum alloy was prepared in the composition shown in Table 4 below.

[0048] A core material composed of the aluminum alloy was prepared, and intermediate materials of A3003 aluminum alloy and outer materials of A4045 aluminum alloy were clad onto opposite sides of the core material. Here, the core material was 1.5 mm thick, and the intermediate materials and the outer materials were each 0.075 mm thick . Specifically, the intermediate material on one side was 0.0375 mm thick, the intermediate material on the opposite side was 0.0375 mm thick, the outer material on the one side was 0.0375 mm thick, and the outer material on the opposite side was 0.0375 mm thick. The materials were roll-formed to prepare a gas tube.

TABLE-US-00004 TABLE 4 Composition of aluminum alloy according to Example 1 Composition (wt. %) Cu Si Fe Mg Mn Ti Al 0.5 0.7 0.5 0.3 0.7 0.15 Rem.

COMPARATIVE EXAMPLE 1

[0049] Outer materials of A4045 aluminum alloy were cladded onto opposite surfaces of a core material of A3003 aluminum alloy. Here, the core material was 1.5 mm thick, and each of the outer materials was 0.0375 mm thick. The materials were roll-formed to prepare a gas tube.

TEST EXAMPLE 1

[0050] A corrosion resistance test for Example 1 and Comparative Example 1 was carried out.

[0051] In the corrosion resistance test, condensate having a composition as shown in Table 5 was prepared, and the condensate was circulated through specimens of Example 1 and Comparative Example 1 using an apparatus illustrated in FIG. 6. Here, a circulation cycle of the condensate is illustrated in FIG. 7, wherein one cycle includes that the condensate of 80 C. was circulated in the specimens of Example and Comparative Example 1 for 2 hours and the specimens were left for 22 hours at room temperature. The test was carried out for one week, wherein the cycle was repeated for five days, and the specimens were left for 48 hours at room temperature.

TABLE-US-00005 TABLE 5 Composition of condensate Composition (ppm) Temperature pH Cl NO.sub.3.sup. SO.sub.4.sup.2 F.sup. CH3COO.sup. HCOO.sup. 80 C. 1.85 300 2,000 400 200 20,000 20,000

[0052] Cross sections of the specimens were observed to confirm corrosion resistance. FIG. 8(a) is a photograph illustrating the cross section of Comparative Example 1 before carrying out the test; FIG. 8(b) is a photograph illustrating the cross section of Comparative Example 1 after carrying out the test; FIG. 9(a) is a photograph illustrating the cross section of Example 1 before carrying out the test; and FIG. 9(b) is a photograph illustrating the cross section of Example 1 after carrying out the test. After the test, corrosion progressed in Comparative Example 1 with a narrow and deep shape, and intergranular corrosion also occurred so that it was confirmed that Comparative Example 1 was vulnerable in the condensate present environment. On the contrary, in Example 1 according to the present invention, the progress of corrosion was remarkably less compared with Comparative Example 1. In addition, the corrosion did not progress with a narrow and deep shape so that it was confirmed that risk of penetration of the materials was remarkably smaller compared with Comparative Example 1.

[0053] Therefore, it was confirmed that the aluminum alloy material 100 according to the present invention is suitable for a gas tube in an EGR cooler in terms of corrosion resistance.

[0054] Although the present invention has been described with reference to the embodiments, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. It is thus well known to those skilled in that art that the present invention is not limited to the embodiments disclosed in the detailed description, and the patent right of the present invention should be defined by the scope and spirit of the invention as disclosed in the accompanying claims. Accordingly, it should be understood that the present invention includes various modifications, additions, and substitutions without departing from the scope and spirit of the invention as disclosed in the accompanying claims.