KR20210035138A - High corrosion-resistant heat exchanger tube and method for preparing the same - Google Patents

Abstract

The present invention relates to a high corrosion resistant heat exchanger pipe and a method for manufacturing the same. More specifically, the present invention indicates excellent corrosion resistance and strength and is a thin separation type pipe to effectively restrain degradation of elongation during manufacturing. Therefore, as a result, processing of the pipe such as expansion, contraction, and bending is easily performed, preferential corrosion of a processing unit can be restrained, and manufacturing costs can be reduced.

Description

High corrosion-resistant heat exchanger tube and method for preparing the same}

The present invention relates to a high corrosion resistance heat exchanger piping and a manufacturing method thereof. Specifically, it exhibits excellent corrosion resistance and strength, and by effectively suppressing the decrease in elongation during manufacture as a thin peelable pipe, as a result, it is easy to process the expansion of the pipe, shaft pipe, bending, etc., and preferential corrosion of the processed part can be suppressed. And, it relates to a heat exchanger piping and a manufacturing method thereof to reduce manufacturing cost.

The pipe for the heat exchanger is a component used in the heat exchanger of an automobile, and is made of aluminum alloy material in consideration of light weight, high strength, and heat conduction characteristics. The pipe for a heat exchanger made of such an aluminum alloy is mounted on a heat exchanger of a transport device including a vehicle to enable high-efficiency heat exchange, thereby reducing fuel efficiency of the transport device.

Depending on the application, pipes for heat exchangers include radiators, heater cores, oil coolers and condensors using R134a as refrigerants, evaporators, etc. of automobiles that use cooling water as refrigerant. Is used. Since such a heat exchanger tube is in direct contact with a refrigerant, an aluminum alloy having excellent corrosion resistance as well as strength and extrudability is required.

It is known that an aluminum alloy of 3000 series, such as Al3003, which has been used as a material for pipes for heat exchangers in the related art, exhibits excellent corrosion resistance. However, the 3000 series aluminum alloy is actually a heat exchanger pipe in a considerably deformed state compared to the initial state when it is manufactured as a pipe for a heat exchanger, and thus the minimum tensile strength required for the heat exchanger pipe may not be 90 MPa and the minimum yield strength 30 MPa may not be satisfied.

In particular, there is a problem that post-processing such as expansion, shaft pipe, bending, etc. is difficult due to excessive decrease in elongation during manufacture of a peelable pipe with a thin thickness, and the processing part is preferentially corroded during post-processing. In addition, when applied to the SWAAT test, one of the methods of evaluating the corrosion resistance of heat exchanger piping, the minimum corrosion resistance of 900 hours is not satisfied.

Meanwhile, Korean Patent Publication No. 10-2013-0109198, Japanese Patent Publication No. 11-21649, Japanese Patent Publication No. 2004-83954, and US Patent Publication No. 2011/0192583 A1 include heat exchangers with improved physical properties. Aluminum alloys for piping are disclosed.

In particular, Korean Patent Laid-Open No. 10-2013-0109198 discloses copper (Cu) 0.03 to 0.07 wt%, manganese (Mn) 0.3 to 0.55 wt%, iron (Fe) 0.05 to 0.15 wt%, and titanium (Ti) 0.08 to 0.12. An aluminum alloy containing aluminum and impurities in the remaining amount is disclosed, including 0.03 to 0.06% by weight of chromium (Cr), and 0.1% by weight or less of silicon (Si), and Japanese Patent Laid-Open No. 11-21649 Copper (Cu) 0.35 ~ 0.55% by weight, zinc (Zn) less than 0.03% by weight, titanium (Ti) 0.003 ~ 0.01% by weight, iron (Fe) 0.15 ~ 0.35% by weight, zirconium (Zr) 0.02 ~ 0.05% by weight, Silicon (Si) containing 0.15% by weight or less, iron (Fe) / silicon (Si) ≥ 2.5, the remaining amount is aluminum and impurities aluminum alloys are disclosed.

In addition, Japanese Laid-Open Patent No. 2004-83954 discloses copper (Cu) 0.01 to 0.5% by weight, manganese (Mn) 0.1 to 0.5% by weight, zinc (Zn) 0.01 to 0.5% by weight, titanium (Ti) 0.05 to 0.3% by weight. , Chromium (Cr) 0.05 to 0.6% by weight, silicon (Si) 0.1 to 1.0% by weight, and the remaining amount is aluminum and an aluminum alloy which is an impurity, and U.S. Patent Publication No. 2011/0192583 A1 discloses copper ( Cu) 0.3 to 1.5% by weight, manganese (Mn) 0.3 to 2.0% by weight, titanium (Ti) 0.01 to 0.5% by weight, silicon (Si) 0.3 to 1.5% by weight, boron (B) 0.001 to 0.1% by weight, and , The remaining amount is aluminum and an aluminum alloy, which is an impurity, is disclosed.

However, the aluminum alloys contain only a very small amount of copper (Cu), manganese (Mn), and zinc (Zn) in order to improve the extrudability of the alloy, so that they are used as materials for heat exchanger piping. Elongation characteristics are excessively degraded when manufactured as a thin peelable pipe due to insufficient or insufficient effect of crystal grain refinement due to reduction and simple addition of titanium (Ti) and chromium (Cr) content, and as a result, expansion of pipes, shaft pipes, Processing such as bending is difficult, and there is a problem that preferential corrosion of the processing part occurs during processing.

Therefore, it exhibits excellent corrosion resistance and strength, and by effectively suppressing the decrease in elongation during manufacture as a thin peelable pipe, as a result, it is easy to process the expansion of the pipe, shaft pipe, bending, etc., and preferential corrosion of the processed part can be suppressed. In this situation, there is an urgent need for a heat exchanger pipe and a method for manufacturing the same to reduce manufacturing cost.

An object of the present invention is to provide a heat exchanger piping having sufficient corrosion resistance and strength and a method of manufacturing the same.

In addition, the present invention can effectively suppress the deterioration of the elongation characteristics when manufacturing a thin peelable pipe, so that it is easy to process the expansion of the pipe, shaft pipe, bending, etc., and a heat exchanger pipe that can suppress preferential corrosion of the processed part. It is an object of the present invention to provide a method for manufacturing the same.

Further, an object of the present invention is to provide a heat exchanger piping and a method for manufacturing the same, in which a separate crystal grain refinement process is unnecessary, so that a manufacturing process is simple and thus manufacturing cost is reduced.

In order to solve the above problems, the present invention,

Manganese (Mn) 0.6 to 1.2% by weight, iron (Fe) 0.1 to 0.3% by weight, copper (Cu) 0.1 to 0.5% by weight, zinc (Zn) 0.15 to 0.6% by weight, titanium (Ti) 0.05 to 0.3% by weight, Contains 0.15 to 0.3% by weight of silicon (Si) and 0.05 to 0.1% by weight of magnesium (Mg), and the remainder is made of aluminum and impurities, and is made of a highly corrosion-resistant aluminum alloy having a crystal grain size of 50 µm or less, and has a yield strength. A heat exchanger piping with 30 MPa or more, tensile strength 90 MPa or more, elongation of 35% or more, and corrosion resistance of 900 hours or more in the SWAAT test according to ASTM G85 is provided.

Here, it provides a heat exchanger piping, characterized in that the outer diameter is 5 to 8 mm, the thickness is 0.4 to 0.7 mm.

In addition, it provides a heat exchanger pipe, characterized in that the crystal grain diameter of the aluminum alloy is controlled to 70 ㎛ or less even when brazing heat treatment is performed.

And, it provides a heat exchanger piping, characterized in that the surface is treated with zinc spray (Thermal Arc Spray; TAS).

On the other hand, manganese (Mn) 0.6 to 1.2 wt%, iron (Fe) 0.1 to 0.3 wt%, copper (Cu) 0.1 to 0.5 wt%, zinc (Zn) 0.15 to 0.6 wt%, silicon (Si) 0.15 to 0.3 wt% %, and magnesium (Mg) containing 0.05 to 0.1% by weight, and the remaining amount of the aluminum alloy molten metal comprising aluminum and impurities, and titanium diboride (TiB ₂ ) added to the molten aluminum alloy to titanium (Ti ) Preparing an aluminum alloy molten metal further comprising 0.05 to 0.3% by weight, degassing the aluminum alloy molten metal within 10 minutes after adding _{titanium diboride (TiB 2) and filtering foreign substances, degassing and} Preparing a wire rod by continuous casting rolling with the aluminum alloy molten metal in which foreign substances are filtered, heat-treating the wire rod at a temperature range of 440 to 580°C for 12 to 24 hours and then air cooling, and It provides a method of manufacturing the heat exchanger pipe, characterized in that it comprises the step of conformally extruding the air-cooled wire rod after heat treatment.

Here, after the confirmation extrusion step, it provides a method of manufacturing a heat exchanger pipe, further comprising a step of treating a surface of the heat exchanger pipe with a thermal arc spray (TAS).

In addition, it provides a method of manufacturing a heat exchanger pipe, characterized in that the temperature of the aluminum alloy molten metal applied to the continuous casting rolling is 750 to 900 ℃.

Heat exchanger piping according to the present invention exhibits an excellent effect of simultaneously exhibiting excellent corrosion resistance and strength with specific alloying elements and their mixing ratio.

In addition, the heat exchanger piping according to the present invention achieves efficient grain refinement by controlling the content of specific alloying elements and the timing of addition, thereby effectively suppressing the decrease in elongation during manufacture as a thin peelable piping, resulting in the expansion of the piping. , Shaft pipe, bending, etc., are easy to process, and it shows an excellent effect that can suppress preferential corrosion of the processed part.

Further, since the heat exchanger pipe according to the present invention does not require a separate grain refinement process, the manufacturing process is simple, and thus manufacturing cost is reduced.

1 is a flow chart of a manufacturing process of an aluminum alloy forming a heat exchanger pipe according to the present invention.
2 is a flowchart of a manufacturing process of a heat exchanger pipe according to the present invention.

The present invention relates to high corrosion resistance heat exchanger piping, and the aluminum alloy forming it is manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), titanium (Ti), other impurities and aluminum (Al) Includes.

Manganese (Mn) is an alloying element that contributes to the corrosion resistance of aluminum alloys, and it is finely distributed in the aluminum base and has a function to increase the potential of aluminum, so that the contribution of corrosion resistance increases depending on the content and has a positive influence on strength improvement. .

The content of manganese (Mn) may be 0.6 to 1.2% by weight based on the total weight of the aluminum alloy. Here, when the content of manganese (Mn) is less than 0.6% by weight, the effect of improving the corrosion resistance and strength of the aluminum alloy by the addition of manganese (Mn) is difficult to exert, whereas when the content of manganese (Mn) is more than 1.2% by weight, the extrudability of the aluminum alloy is lowered. Can be.

Iron (Fe) exists as an Al-Fe intermetallic compound in the matrix. In addition, when manganese (Mn) or manganese (Mn) and silicon (Si) coexist, the strength after brazing is crystallized or precipitated as an Al-Mn-Fe intermetallic compound or Al-Mn-Fe-Si intermetallic compound. And, the intermetallic compound acts to suppress grain coarsening.

The content of iron (Fe) may be 0.1 to 0.3% by weight based on the total weight of the aluminum alloy. Here, when the content of iron (Fe) is less than 0.1% by weight, it is difficult to exert the effect of improving the strength of the aluminum alloy by the addition of iron (Fe), whereas when the content of iron (Fe) is more than 0.3% by weight, the intermetallic compound becomes coarse and the aluminum alloy is extruded. The property may be lowered and corrosion resistance may be significantly lowered.

Copper (Cu), like manganese (Mn), is an alloying element that is dissolved in aluminum (Al) to increase the potential of the aluminum alloy, and serves to improve the corrosion resistance and strength of the aluminum alloy.

The content of copper (Cu) may be 0.1 to 0.5% by weight based on the total weight of the aluminum alloy. Here, when the content of copper (Cu) is less than 0.1% by weight, the effect of improving the corrosion resistance and strength of the aluminum alloy by the addition of copper (Cu) is difficult to exert, whereas when the content of copper (Cu) is more than 0.5% by weight, the extrudability and corrosion resistance of the aluminum alloy This can be degraded at the same time.

Zinc (Zn) has the effect of improving the mechanical performance of the aluminum alloy. The content of zinc (Zn) may be 0.15 to 0.6% by weight based on the total weight of the aluminum alloy. Here, when the content of zinc (Zn) is less than 0.15% by weight, the effect of improving the mechanical performance of the aluminum alloy by the addition of zinc (Zn) is difficult to exert, whereas when the content of zinc (Zn) is more than 0.6% by weight, the extrudability of the aluminum alloy will be reduced. I can.

Titanium (Ti) slightly improves the elongation of the aluminum alloy and, in particular, effectively suppresses the decrease in the elongation when the aluminum alloy is manufactured as a thin peelable pipe by grain refinement. As a result, expansion of the pipe, shaft pipe, bending, etc. Processing is easy and preferential corrosion of the processing part can be suppressed.

The content of titanium (Ti) may be 0.05 to 0.3% by weight based on the total weight of the aluminum alloy. Here, when the content of titanium (Ti) is less than 0.05% by weight, it is difficult to improve the elongation and refine grains of the aluminum alloy by the addition of titanium (Ti), whereas titanium (Ti) has a high melting point when manufacturing aluminum molten metal. Since it is added as titanium diboride (TiB ₂ ), if the content of titanium (Ti) exceeds 0.3% by weight, a large amount of impurities are added to the aluminum alloy to form a coarse intermetallic compound, which will reduce the extrudability and corrosion resistance of the aluminum alloy. I can.

In the present invention, the aluminum alloy may further include chromium (Cr) in addition to the alloying element.

Since chromium (Cr) has an effect of further improving the grain refining effect and strength of the aluminum alloy, it may play a role of assisting the function of titanium (Ti). The content of chromium (Cr) may be 0.05 to 0.3% by weight based on the total weight of the aluminum alloy. Here, when the content of chromium (Cr) is less than 0.05% by weight, it is difficult to exert the effect of further improving the grain refinement effect and strength of the aluminum alloy by the addition of chromium (Cr), whereas when it exceeds 0.3% by weight, it is rather corrosion resistance. Can significantly worsen.

Therefore, when titanium (Ti) and chromium (Cr) are added together, the total content of these alloying elements is limited to 0.5% by weight or less, thereby maximizing the improvement of the corrosion resistance of the aluminum alloy and reducing the content of impurities so that the properties of the aluminum alloy are not reduced. Can be controlled.

In the present invention, the other impurities may include silicon (Si) and magnesium (Mg).

Silicon (Si) has the effect of miniaturizing various recrystallized structures formed in the extrusion process by forming intermetallic compounds such as Al, Mn, and Mg. The content of silicon (Si) may be 0.3% by weight or less based on the total weight of the aluminum alloy. Here, when the content of silicon (Si) is more than 0.3% by weight, the high capacity of manganese (Mn) may be reduced, and the economy of the aluminum ingot manufactured from the aluminum alloy may be reduced.

Magnesium (Mg) is an alloying element that contributes to the improvement of the strength of the aluminum alloy, but as the content increases, the extrudability and elongation of the aluminum alloy may significantly decrease. Therefore, the content of magnesium (Mg) is preferably 0.1% by weight or less based on the total weight of the aluminum alloy.

1 is a flow chart of a manufacturing process of an aluminum alloy forming a heat exchanger pipe according to the present invention.

1, the manufacturing process of the aluminum alloy may include steps a) to d) below.

a) 0.6 to 1.2% by weight of manganese (Mn), 0.1 to 0.3% by weight of iron (Fe), 0.1 to 0.5% by weight of copper (Cu), and 0.15 to 0.6% by weight of zinc (Zn), and the remaining amount is aluminum and Preparing a molten aluminum alloy made of impurities;

b) preparing a molten aluminum alloy further comprising 0.05 to 0.3% by weight of titanium (Ti) by adding titanium diboride (TiB _{2) to the molten aluminum alloy;}

c) degassing the aluminum alloy molten metal within 10 minutes after adding titanium diboride (TiB _{2) and filtering foreign substances;} And

d) manufacturing a wire rod of an aluminum alloy by continuous casting rolling with the aluminum alloy molten metal in which degassing and foreign substances are filtered.

In particular, among the alloying elements constituting the aluminum alloy, titanium (Ti) is _{added as titanium diboride (TiB 2} ) in step b), which has a melting point of 1,800°C and manganese (Mn), which is another alloying element. ) Is higher than the melting point of 1244°C, iron (Fe) of 1540°C, copper (Cu) of 1084.5°C, and zinc (Zn) of 420°C.

In addition, the titanium diboride (TiB ₂ ), unlike other alloying elements, is added within about 10 minutes before the start of the degassing process of the molten aluminum, thereby maximizing the effect of minimizing the grains of titanium (Ti) to reduce the grain size of the aluminum alloy to 50 μm. It can be controlled as follows.

This facilitates post-processing of the heat exchanger pipe made of the aluminum alloy, such as expansion, shaft pipe, bending, etc., it is possible to effectively suppress preferential corrosion of the processed part, and since a separate grain refinement process is not required, the manufacturing process is simple and thus manufacturing Cost can be reduced.

On the other hand, when titanium diboride (TiB ₂ ) is added about 10 minutes before the start of the degassing process of the aluminum alloy, the effect of minimizing the grains of titanium (Ti) may hardly be exhibited depending on the manufacturing conditions of the aluminum alloy.

Further, it is preferable that the temperature of the molten aluminum alloy applied to the continuous casting rolling in step d) is 750 to 900°C. The reason for limiting the injection temperature of the molten metal applied to the continuous casting rolling as described above is to obtain a solid solution as an intermetallic compound, that is, a casting having a dense microstructure, and when the injection temperature of the molten metal exceeds 900°C, casting While there is a problem that the microstructure of is coarse, when the temperature is less than 750°C, a miss run phenomenon may occur in which the mold space cannot be densely filled due to insufficient fluidity of the molten metal.

2 is a flowchart of a manufacturing process of a heat exchanger pipe according to the present invention.

As shown in FIG. 2, the manufacturing process of the heat exchanger pipe according to the present invention may include steps a) to c) below.

a) air-cooling the wire rod of the aluminum alloy manufactured by the process shown in FIG. 1 after heat treatment at a temperature range of 440 to 580°C for 12 to 24 hours, and

b) manufacturing a heat exchanger pipe by conformally extruding the air-cooled wire rod after heat treatment.

In step a), the heat treatment of the aluminum alloy wire rod achieves uniformity of alloy elements forming the aluminum alloy or removal of non-uniform structures such as segregation, and as a result, uniformity of properties of the aluminum alloy and partial corrosion and intergranular corrosion are prevented. Can be suppressed.

In addition, the extrusion speed during the confirm extrusion in step b) may be preferably about 100 mpm. The conformal extrusion method is an extrusion method using shear stress, and requires an extrusion speed of a certain level or higher, and when the extrusion speed is low, surface defects or physical properties of the pipe to be manufactured may be deteriorated.

The manufacturing process of the heat exchanger pipe according to the present invention may further include performing step b) and then c) performing a thermal arc spray (TAS) treatment on the surface of the heat exchanger pipe. The zinc spraying (TAS) treatment may provide a sacrificial anode effect to further improve the corrosion resistance of the heat exchanger pipe.

In the conventional direct extrusion method for manufacturing a heat exchanger pipe, aluminum billets made from an aluminum alloy are discontinuously introduced into an extruder to manufacture a heat exchanger pipe. The heat energy applied to the aluminum billet during such direct extrusion and the shear energy caused by the extrusion diffuses a certain amount of alloying elements such as manganese (Mn) and copper (Cu) and intermetallic compounds that exist in a solid solution state on the aluminum base to the intergranular surface. To precipitate.

Since the degree of precipitation varies depending on the extrusion speed and shear energy, in the case of producing a heat exchanger pipe using direct extrusion that discontinuously introduces aluminum billets, the end region of the input billet and the next billet input. The structure of the alloy is changed due to the difference in the degree to which the precipitation phenomenon occurs at the interlocking region of the start-end region, and as a result, potential difference corrosion may occur at the interlocking region.

Therefore, the manufacturing process of the heat exchanger piping according to the present invention is the direct extrusion by adopting the conformal extrusion method of manufacturing the heat exchanger piping while continuously inserting an aluminum alloy wire rod into the extruder and maintaining the same extrusion line speed of about 100 mpm. A problem with the method, that is, potential difference corrosion due to localized structural deformation of the aluminum alloy forming the heat exchanger piping can be avoided.

The heat exchanger piping manufactured by the manufacturing process according to the present invention has a yield strength of 30 MPa or more and a tensile strength of 90 MPa or more, which is excellent in mechanical strength. In addition, the heat exchanger pipe has an elongation of 35% or more, an outer diameter of 5 to 8 mm, and a thickness of 0.4 to 0.7 mm, even when manufactured as a peelable pipe having an elongation of 35% or more due to grain refinement of the aluminum alloy forming it, the elongation decreases. As is avoided or minimized, post-processing such as expansion, shaft pipe, bending, etc. is easy, and preferential corrosion of processing parts after post-processing can be suppressed.

In addition, the heat exchanger pipe may have a crystal grain size of 50 µm or less of an aluminum alloy constituting it, and a grain size of 70 µm or less even when brazing heat treatment is performed to manufacture a heat exchanger. Further, the heat exchanger pipe has a corrosion resistance of 900 hours or more in the SWAAT test according to ASTM G85, and is extremely superior to the heat exchanger pipe manufactured by conventional aluminum alloy, and a separate grain refinement process of the aluminum alloy is not required. Therefore, the manufacturing process is simple, and thus the manufacturing cost is reduced.

<Example>

1. Manufacturing example

After preparing the remaining amount of alloying elements as shown in Table 1 below, and preparing the remaining amount, wire rods having an outer diameter of 10 mm were each manufactured using the Properch method, and wound around a bobbin in the form of a coil. For the homogenization treatment, heat treatment was performed in the order of air cooling after maintaining for 18 hours in a temperature range of 520°C. Thereafter, pipes having an outer diameter of 8 mm and a thickness of 0.7 mm were manufactured using a heat-treated wire rod at an extrusion speed of 100 mpm using a conformal extrusion method. In Table 1 below, the unit for the content of the alloying element is% by weight.

Si Mg Cr Mn Ti Fe Cu Zn Example 1 0.15 0.05 0.2 0.6 0.15 0.2 0.4 0.3 Example 2 0.15 0.05 0.2 1.2 0.15 0.2 0.2 0.3 Example 3 0.15 0.05 0.2 0.9 0.15 0.2 0.1 0.3 Example 4 0.15 0.05 0.2 0.9 0.15 0.2 0.5 0.3 Example 5 0.15 0.05 0.15 0.9 0.15 0.3 0.3 0.15 Example 6 0.15 0.05 0.2 0.9 0.15 0.2 0.3 0.6 Example 7 0.15 0.05 0.2 0.9 0.15 0.2 0.3 0.3 Example 8 0.3 0.05 0.2 0.9 0.15 0.2 0.3 0.3 Example 9 0.15 0.05 0.3 0.9 0.05 0.2 0.3 0.3 Example 10 0.15 0.05 0.05 0.9 0.3 0.2 0.3 0.3 Example 11 0.15 0.05 0.2 0.9 0.15 0.1 0.4 0.3 Example 12 0.15 0.05 0.2 0.9 0.15 0.3 0.3 0.2 Example 13 0.15 0.1 0.2 0.9 0.15 0.2 0.3 0.3 Example 14 0.15 0.15 0 0.9 0.3 0.2 0.3 0.3 Comparative Example 1 0.15 0.05 0.2 0.5 0.15 0.2 0.3 0.3 Comparative Example 2 0.15 0.05 0.2 1.3 0.15 0.2 0.3 0.3 Comparative Example 3 0.15 0.05 0.2 0.9 0.15 0.2 0 0.3 Comparative Example 4 0.15 0.05 0.2 0.9 0.15 0.2 0.6 0.3 Comparative Example 5 0.15 0.05 0.2 0.9 0.15 0.2 0.3 0 Comparative Example 6 0.15 0.05 0.2 0.9 0.15 0.2 0.3 0.7 Comparative Example 7 0.4 0.05 0.2 0.9 0.15 0.2 0.3 0.3 Comparative Example 8 0.15 0.05 0.4 0.9 0.15 0.2 0.3 0.3 Comparative Example 9 0.15 0.05 0.2 0.9 0.4 0.2 0.3 0.3 Comparative Example 10 0.15 0.05 0.3 0.9 0.3 0.2 0.3 0.3 Comparative Example 11 0.15 0.05 0.2 0.9 0.15 0 0.3 0.3 Comparative Example 12 0.15 0.05 0.2 0.9 0.15 0.4 0.3 0.3 Comparative Example 13 0.15 0.2 0.2 0.9 0.15 0.2 0.3 0.3 Comparative Example 14 0.15 0.05 0.2 0.9 0 0.2 0.3 0.3

2. Property evaluation

1) Evaluation of extrudability, yield strength, tensile strength and elongation

Extrusion was evaluated as good when the extrusion process was possible with an extrusion line speed of 100 mpm, and was evaluated as poor when the extrusion process was impossible. In addition, yield strength, tensile strength and elongation were evaluated according to ASTM E8.

2) Corrosion resistance evaluation

The evaluation of corrosion resistance was evaluated by the SWAAT test according to ASTM G85. Specifically, by adding glacial acetic acid to 4.2% by weight of NaCl solution, the pH is maintained at 2.8 to 3.0, and the maximum withstands corrosion while spraying the pipe specimen at a pressure of 0.07 MPa and a spray amount of 1 to 2 ml/hr under a temperature of 49℃ Time was measured.

The results of the physical property evaluation are as shown in Table 2 below.

Extrudability Yield strength (MPa) Tensile strength (MPa) Elongation(%) SWAAT (hours) Example 1 Good 32 94 36 920 Example 2 Good 33 96 35 980 Example 3 Good 31 92 36 930 Example 4 Good 34 99 36 950 Example 5 Good 31 92 35 960 Example 6 Good 33 95 39 900 Example 7 Good 32 93 37 950 Example 8 Good 33 95 36 920 Example 9 Good 32 93 36 920 Example 10 Good 33 93 36 930 Example 11 Good 31 92 36 930 Example 12 Good 34 98 35 920 Example 13 Good 32 94 35 930 Example 14 Good 30 90 35 900 Comparative Example 1 Good 31 92 33 890 Comparative Example 2 Bad 33 95 35 980 Comparative Example 3 Good 30 90 35 890 Comparative Example 4 Bad 34 100 35 920 Comparative Example 5 Good 29 89 32 960 Comparative Example 6 Good 33 93 36 880 Comparative Example 7 Bad 34 97 35 890 Comparative Example 8 Good 32 94 34 880 Comparative Example 9 Good 33 94 35 890 Comparative Example 10 Good 32 94 34 870 Comparative Example 11 Good 29 89 36 930 Comparative Example 12 Good 34 100 32 880 Comparative Example 13 Good 32 94 33 890 Comparative Example 14 Good 27 83 36 820

As shown in Table 2, the heat exchanger pipes of Examples 1 to 14 according to the present invention have good extrudability, excellent mechanical strength such as yield strength and tensile strength, and a peelable type having an outer diameter of 8 mm and a thickness of 0.7 mm. Even though it is a pipe, its elongation is over 35%, so it is easy to post-processing such as expansion pipe, shaft pipe, bending, etc. to manufacture the final finished heat exchanger, and it is possible to suppress preferential corrosion of the processing part during post-processing. Compared to the SWAAT test, it has achieved 900 hours or more during the SWAAT test. On the other hand, the pipe specimen of Comparative Example 1 had insufficient elongation and corrosion resistance because the content of manganese (Mn) was below the standard, whereas the pipe specimen of Comparative Example 2 was It was confirmed that the extrudability was poor due to the excessive content of (Mn).

In addition, it was confirmed that the pipe specimen of Comparative Example 3 had insufficient corrosion resistance because copper (Cu) was not added, whereas the pipe specimen of Comparative Example 4 had an excessive content of copper (Cu), and thus it was confirmed that the extrudability was poor.

The piping specimen of Comparative Example 5 was insufficient in mechanical strength and elongation such as yield strength and tensile strength because zinc (Zn) was not added, whereas the piping specimen of Comparative Example 6 had an excessive zinc (Zn) content and thus extrudability. It was found to be poor, and rather, the corrosion resistance was lowered, and the piping specimen of Comparative Example 7 had an excessive content of silicon (Si), and thus it was confirmed that extrudability and corrosion resistance were poor.

The piping specimens of Comparative Examples 8 to 10 have an excessive content of chromium (Cr) or titanium (Ti), or the content of chromium (Cr) and titanium (Ti) exceeding 0.5% by weight, thereby reducing elongation and corrosion resistance. Was confirmed.

The piping specimen of Comparative Example 11 was insufficient in mechanical strength such as yield strength and tensile strength because iron (Fe) was not added, whereas the piping specimen of Comparative Example 12 had an excessive iron (Fe) content, resulting in lower elongation and corrosion resistance. It was confirmed to be.

The piping specimen of Comparative Example 13 has an excessive content of magnesium (Mg) and thus the elongation and corrosion resistance are lowered, and the piping specimen of Comparative Example 14 does not contain titanium (Ti), so mechanical strength and corrosion resistance such as yield strength and tensile strength are It was confirmed to be degraded.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art may variously modify and change the present invention within the scope not departing from the spirit and scope of the present invention described in the following claims. I will be able to do it. Therefore, if the modified implementation basically includes the elements of the claims of the present invention, it should be seen that all are included in the technical scope of the present invention.

Claims (7)

Manganese (Mn) 0.6 to 1.2% by weight, iron (Fe) 0.1 to 0.3% by weight, copper (Cu) 0.1 to 0.5% by weight, zinc (Zn) 0.15 to 0.6% by weight, titanium (Ti) 0.05 to 0.3% by weight, It contains silicon (Si) 0.15 to 0.3% by weight, and magnesium (Mg) 0.05 to 0.1% by weight, and the remainder is made of aluminum and impurities, and is made of a highly corrosion-resistant aluminum alloy having a crystal grain size of 50 μm or less,
Yield strength is more than 30 MPa, tensile strength is more than 90 MPa, elongation is more than 35%,
Heat exchanger piping with corrosion resistance of 900 hours or more in SWAAT test according to ASTM G85. The method of claim 1,
Heat exchanger piping, characterized in that the outer diameter is 5 to 8 mm, the thickness is 0.4 to 0.7 mm. The method according to claim 1 or 2,
Heat exchanger piping, characterized in that the crystal grain diameter of the aluminum alloy is controlled to 70 µm or less even when brazing heat treatment is performed. The method according to claim 1 or 2,
Heat exchanger piping, characterized in that the surface is treated with zinc spray (Thermal Arc Spray; TAS). Manganese (Mn) 0.6 to 1.2% by weight, iron (Fe) 0.1 to 0.3% by weight, copper (Cu) 0.1 to 0.5% by weight, zinc (Zn) 0.15 to 0.6% by weight, silicon (Si) 0.15 to 0.3% by weight, And magnesium (Mg) comprising 0.05 to 0.1% by weight, the remaining amount of preparing a molten aluminum alloy consisting of aluminum and impurities,
A step of preparing a molten aluminum alloy further comprising 0.05 to 0.3% by weight of titanium (Ti) by adding titanium diboride (TiB _{2) to the molten aluminum alloy,}
Degassing the aluminum alloy molten metal within 10 minutes after adding titanium diboride (TiB _{2) and filtering foreign substances,}
Producing a wire rod by continuous casting rolling with the aluminum alloy molten metal in which degasification and foreign matters are filtered,
Air-cooling the wire rod after heat treatment at a temperature range of 440 to 580°C for 12 to 24 hours, and
A method of manufacturing a heat exchanger pipe according to claim 1 or 2, comprising the step of conformally extruding the air-cooled wire rod after heat treatment. The method of claim 5,
After the conforming extrusion step, the method of manufacturing a heat exchanger pipe further comprising the step of treating a surface of the heat exchanger pipe with a thermal arc spray (TAS). The method of claim 5,
The method of manufacturing a heat exchanger pipe, characterized in that the temperature of the molten aluminum alloy applied to the continuous casting rolling is 750 to 900 ℃.

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