KR20150071054A - Corrosion-resistant brazing material containing flux - Google Patents

Abstract

The present invention relates to a corrosion resistant brazing member, used for attaching the same or different kinds of metal materials at a low temperature. The brazing member is formed of a brazing alloy, comprising Si 4-15wt%, In 0.1-3.0wt%, and the rest AI; and fluoride flux corresponding to 10-40wt% of the weight of the brazing alloy. The formation is formed into a 3D shape through the mechanical treatment of extrusion molding and powder metal forging or formed into paste containing liquid binder. The brazing member improves corrosion resistance and welding temperature and flow by adding In instead of Zn, which causes corrosion resistance in the formation of the existing Al-Si-Zn brazing alloy. Thus, the member is able to be used in a variety of industrial fields including electric and electronic fields demanding strengthened welding quality against corrosion resistance.

Description

CORROSION-RESISTANT BRAZING MATERIAL CONTAINING FLUX < RTI ID = 0.0 >

The present invention relates to a brazing material used for bonding a homogeneous or heterogeneous metal material at a low temperature, and more particularly, to a brazing material used for bonding an aluminum-silicon-indium alloy and a fluoride-based flux containing aluminum as a main component .

Brazing is a technique for joining the same kind or different kinds of metal members to be bonded by using a filler metal having a melting point lower than that of the base metal to be joined. The brazing is a process for joining a noble metal such as gold or silver, To the heat exchanger pipe joint of the heat exchanger.

In the brazing process, first, a liquid flux is applied to a portion to be bonded of a metal material, then a brazing material is placed thereon and then heated to remove oxides formed on the surface of the metal material, while the brazing material is melted To be solidified in a state of being filled in the gap of the joining target portion so that the joining between the metal members is performed.

On the other hand, in the above-described conventional brazing method, since the flux is applied to the joining target portion and the brazing material is placed thereon, the brazing material is joined by melting through the heating, so that the work process is complicated, It is difficult to apply a proper amount of flux to a desired site by flowing down the flux of the metal from the surface of the metal member.

In the patent No. 297605 developed by this cause, the chloride-based powder or the fluoride-based powder is uniformly mixed into the aluminum alloy powder, the powder is cast into a molding container, powder is forged and formed into a billet, and then preheated at a temperature of about 500 ° C And the brazing material and the flux are integrated to provide a molded brazing material.

The above-mentioned patent disadvantages the conventional flux coating type brazing joint because the bonding is performed only by heating the brazing material formed in a three-dimensional shape by integrating the flux and the brazing material on the metal member to be bonded. .

On the other hand, although the above-mentioned patent has the above-mentioned advantages in terms of the work process, it is pointed out that the brazing temperature as the quality characteristic required in the brazing joint is about 600 ° C, which is not economical in terms of relatively high point.

Therefore, in order to improve the relatively high brazing temperature which is a disadvantage of the above-mentioned Japanese Patent No. 297605, the present invention uses a brazing alloy of Al + Zn or Al + Zn + Si alloy containing Zn having a low melting point, (CsF), which is known to be low, and developed a brazing material in which the flux and the brazing alloy were integrated. This was registered as a patent No. 509587.

The brazing material of the above patent has a brazing material temperature of about 500 ° C, which is lower than that of the prior art. As a result, the quality of the joint is improved and the economical efficiency is improved as compared with the past. As a result, Have been widely used.

In recent years, however, as the trend of the industry related to electrical and electronic parts has been strengthened in terms of quality characteristics and the corrosion resistance of the brazed joint is also strictly controlled as one of such enhanced quality characteristics, the brazing material of Patent No. 509587 There is a problem about corrosion resistance in Edo.

Since the joint portion of the brazing material using the brazing material described in the above-mentioned Japanese Patent No. 509587 has no problem at first but corrosion is known to occur over time, it is necessary to maintain the desired quality characteristic of the brazing material of the patent, The development of a new brazing material that solves the problem of the conventional brazing material has been demanded.

Therefore, the present invention solves the problem of corrosion resistance which is pointed out as a problem of the flux-integrated Al + Zn brazing material in which the conventional Al + Zn-based or Al + Si + Zn-based alloy and the cesium fluoride-based flux are integrally mixed Resistant brazing material having a high corrosion resistance and corrosion resistance.

Another object of the present invention is to allow Zn to be excluded from the brazing alloy based on the fact that the element causing corrosion of the joint in the conventional flux-containing brazing material is Zn, but even if Zn is excluded, Which is capable of brazing at a low bonding temperature without any separate flux coating process through a brazing alloy composition and a flux composition, and which is excellent in corrosion resistance of the bonded portion after bonding.

The above object of the present invention is achieved by a brazing alloy (Al-Si-In) made of aluminum (Al), silicon (Si) and indium (In) and a fluoride flux having a weight corresponding to 10 to 40% Is achieved by a corrosion resistant brazing material containing a flux that has been made.

In the corrosion-resistant brazing material of the present invention, the composition of the brazing alloy is 4 to 15 wt% of Si, 0.1 to 3.0 wt% of In and the balance Al, and a preferable example of the fluoride-based flux is KAlF ₄ .

The brazing material of the present invention can be formed into a three-dimensional shape by mixing powder of a fluoride-based flux (KAlF ₄ ) with an alloy powder made of Al-Si-In and mechanically processing it by powder forging and extrusion molding.

In this case, the particle size of the alloy powder is preferably in the range of 30 to 100 mesh, and the particle size of the flux is in the range of 100 to 200 mesh, which is relatively small as compared with the particle size of the alloy powder.

The brazing composition of the present invention may be in the form of a paste by adding a liquid organic binder.

In the brazing material of the present invention, the role of each element in the brazing alloy Al-Si-In and the reason for limiting the component are as follows.

First, Si plays a role of improving the strength of the alloy by forming a solid solution in the matrix after brazing, and also acting as a noble metal for improving the flowability of the weld metal. When the content is less than 4 wt% If the content exceeds 15 wt%, the strength becomes too high and the impact toughness is lowered. Therefore, the content is preferably 4 to 15 wt%.

Next, In has an advantage that it plays a decisive role in lowering the bonding temperature in the brazing material of the above-mentioned Japanese Patent No. 509587, but it is an element added as a substitute for Zn, which is said to be a cause of corrosion, It has a much better effect in reducing potential. The content is preferably in the range of 0.1 to 3.0 wt%, and if it is less than 0.1 wt%, the weldability is hardly affected. If the content is more than 3.0 wt%, the indium oxide film is formed and the flowability in welding is lowered.

On the other hand, the content of the fluoride-based flux (KAlF ₄ ) is preferably 10 to 40% of the weight of the brazing alloy. If the content is less than 10%, the fluidity is lowered, , The flowability is too high and flows out of the brazing joints to deteriorate the weldability.

The process of forming a three-dimensional shape using the mixed composition of the alloy powder and the flux powder, including the paste-type composition based on the brazing material of the present invention, the method of mixing the alloy powder and the flux, and the like disclosed in the aforementioned Japanese Patent No. 509587 So that further explanation is omitted here. In this case, the three-dimensional shape may be any of a rod shape, a plate shape, a pipe shape, a wire shape, and a ring shape.

In the brazing material of the present invention, addition of In instead of Zn causing corrosion resistance in the Al-Si-Zn type brazing alloy composition of the conventional patent No. 509587 improves the welding temperature and flowability and improves the corrosion resistance, It is expected to be usefully used in various industrial fields including electric and electronic fields requiring enhanced welding quality characteristics against corrosion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a joining process of a tubular body using a ring-shaped brazing material. FIG.
Figures 2 (a) and 2 (b) are cross-sectional photographs of the brazed joints before and after the salt spray test.
3 is a cross-sectional photograph of a brazed joint of an aluminum-aluminum tube.
Fig. 4 is a cross-sectional photograph and an enlarged view of a brazed joint of an aluminum-copper tube;
FIG. 5 is a photograph showing the flowability of a joint portion using a ring-shaped brazing material. FIG.

The objects, technical constructions and operation effects of the present invention will be more clearly understood from the following examples, but the present invention is not limited to these examples.

A brazing alloy having the composition shown in Table 1 below was prepared and mixed with the flux.

                Metal (wt%) Metal (wt%) + flux (wt%)     Al Si In Zn metal KAlF ₄ CsAlF ₄ Example 1 89 10 One 80 20 Example 2 89.5 10 0.5 80 20 Example 3 87 12 One 80 20 Example 4 87.5 12 0.5 80 20 Example 5 91.5 7 1.5 80 20 Example 6 93 5 2 80 20 Comparative Example 1 90 10 80 20 Comparative Example 2 22 78 85 15

In Table 1, Comparative Example 1 is a re-composition of the SKA-TB 200 brazing product by the present applicant company (Sunkwang Empa Co., Ltd.), and Comparative Example 2 is also the same as that of Patent No. 509587 of SU- Brazing resurfacing.

The results of melting point measurement for the brazing materials of the above-mentioned Examples and Comparative Examples are shown in Table 2 below.

Solid carrier (℃) Liquid line (℃) Example 1 569 581 Example 2 573 585 Example 3 566 572 Example 4 571 578 Example 5 578 598 Example 6 578 596 Comparative Example 1 577 590 Comparative Example 2 465 486

The results of Table 2 show that the brazing composition according to the present invention has a higher melting temperature than that of Comparative Example 2, but is lower than Comparative Example 1.

The alloy metal of the composition of Example 1 of the above Table 1 was made into powders of 30 mesh or less (550 mu m) using an atomizer facility. Next, KAlF ₄ , which is a fluoride-based flux, was added to the alloy powder at a weight ratio (80:20) of Example 1 to prepare a brazing material (powder state) in which alloy powder and flux powder were mixed. At this time, the melting point of the alloy powder was 575 ° C and the melting point of the flux was 560 ° C.

The mixed brazing material was placed in a cylindrical mold and forged to form a round bar-shaped billet. The size of the billet was 85 mm in diameter and 300 mm in length.

Subsequently, the billet was extrusion-molded into a pipe having an inner diameter of 8.2 mm and an outer diameter of 11.3 mm using an extrusion facility. The brazing material extruded in the form of a pipe was cut to a width of 1.5 mm to prepare a ring-shaped brazing material.

On the other hand, an aluminum (Al) tube 2 was inserted into a portion where an end portion of a copper (Cu) tube 1 having an outer shape of 8 mm and a thickness of 0.8 mm was expanded (9 mm in depth) 3) was placed in the space between the bulb portion of the copper tube (1) and the aluminum tube (2), and the tube was heated in an electric furnace for 5 minutes and then cooled at room temperature.

Then, the ring-shaped brazing material was placed on the joints of aluminum and aluminum pipes having the same dimensions as those of the above-mentioned tubular body to be joined but different in material of the tubular body, and brazing was performed under the same heating conditions.

At this time, the temperature of the electric furnace was set at 600 ° C, and nitrogen gas was supplied at a rate of 2 m 3 / min with the atmospheric gas.

On the other hand, the brazing material of Comparative Example 1 and Comparative Example 2 was provided with a brazing material in the form of a three-dimensional ring in the same process as the brazing material forming process of Example 1, And then heated under the same heating conditions to allow the brazing operation.

In order to examine the corrosion resistance between the embodiment of the present invention and the comparative example, a salt spray test was carried out on the tube connection portion obtained through the above process.

The test was carried out with the request of "Citi Scoria (Korea) Co., Ltd." in Korea. The condition was confirmed by enlarging the cross section of the specimens after salt spraying with NaCl 5% aqueous solution for 300 hours Respectively.

2 (a) and 2 (b) are photographs of cross sections of the tube joints before and after the salt spray test, wherein A-1 and A-2 are respectively an aluminum-aluminum tube joint using the ring- B-1 and B-2 are respectively an aluminum-aluminum pipe joint and an aluminum-copper pipe joint using the ring-type brazing material of Comparative Example 1, and C-1 and C-2 are respectively ring type brazing material of Comparative Example 2 Aluminum-aluminum joints and aluminum-copper joints.

FIG. 3 is a cross-sectional photograph taken after polishing the surface of the aluminum-aluminum tube brazing joints A-1, B-1 and C-1 of FIG. 2, .

As shown in the photograph, no corrosion was observed in all three specimens. In the aluminum-aluminum tube brazing joint, both the specimens of the embodiment and the comparative specimen showed good results in terms of corrosion resistance.

Next, FIG. 4 is a cross-sectional photograph taken after polishing the surfaces of the joints in order to examine the degree of corrosion of the brazing joints of A-2, B-2 and C-2 brazing joints of FIG. 2, It is an enlarged photograph.

In each example of the photographs, a part of the interior of the blue color is a joint part, and an enlarged micrograph of the copper part is shown at the lower part thereof. In the case of example 1 of the A-2 specimen, And the C-2 micrographs of B-2 and C-2, respectively. Thus, it can be confirmed that the case where In contains Al (Example 1) is more advantageous from the viewpoint of corrosion resistance than the case where Al contains Zn in the composition of the brazing alloy (Comparative Example 2).

Next, in order to determine the flowability at the time of welding, the brazing test specimen having an outer diameter of 2 mm and a length of 1 cm according to Example 1 and a brazing specimen having the same shape and dimensions according to Comparative Example 1 were placed on an aluminum 1050 plate, Lt; 0 > C for 2 minutes.

FIG. 4 is a photograph of the brazing material according to Example 1 and Comparative Example 1 taken out from the electric furnace after the above-mentioned heating, and it is confirmed that the flowability of Example 1 is much better than that of Comparative Example 1. That is, it can be seen that the flowability is improved by the inclusion of indium in the case of Example 1.

Claims (5)

  A brazing alloy comprising 4 to 15 wt% of Si, 0.1 to 3.0 wt% of In, and the balance Al, and a fluoride-based flux having a weight corresponding to 10 to 40% of the weight of the brazing alloy. ashes. The corrosion resistant brazing material as claimed in claim 1, wherein the fluoride-based flux is KAlF ₄ . A brazing alloy consisting of 4 to 15 wt% of Si, 0.1 to 3.0 wt% of In and the balance Al and a fluoride-based flux having a weight corresponding to 10 to 40% of the weight of the brazing alloy, Wherein the flux-containing corrosion resistant brazing material is formed into a three-dimensional shape. 4. The method of claim 3 wherein the fluoride-based flux brazing corrosion resistant material containing a flux, characterized in that KAlF _4. 4. The corrosion resistant brazing material as claimed in claim 3, wherein the three-dimensional shape is any one of a rod shape, a plate shape, a pipe shape, a wire shape, and a ring shape.

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