KR20040097827A - Brazing agent containing a flux for brazint at a low temperture - Google Patents

Abstract

PURPOSE: A brazing agent containing a flux for low temperature brazing is provided to improve quality of a welding section and to simplify brazing work by properly controlling an amount of the flux. CONSTITUTION: A brazing agent includes Zn alloy powder consisting of 10 to 40 weight percent of Al or Al + Si and Zn. 10 to 40 weight percent of CeF is added to the Zn alloy powder. Mixed powder of the Zn alloy powder and flux powder is subject to mechanical processes, such as a powder forging process and an extruding process in such a manner that the mixed powder is formed in a three-dimensional shape. The granularity of the Zn alloy powder is less than 30mesh, and the granularity of the flux powder is less than the granularity of the Zn alloy powder.

Description

Brazing agent containing a flux for brazint at a low temperture}

The present invention relates to a brazing material used for joining metal members of the same or different types, and more particularly, to brazing by molding or pasting a mixed powder obtained by mixing a cesium fluoride flux with a metal powder made of zinc alloy. It relates to a low temperature bonding brazing material containing a flux to simplify the process and to enable low temperature brazing.

Brazing is a technique of joining metal parts of the same or different types by using a filler metal having a lower melting point than that of the base metal to be joined. It has been widely applied to pipe joints and the like.

The brazing joining process involves first applying a liquid flux to the joining part of the metal member, placing the brazing material and heating to remove the oxides formed on the surface of the metal member while melting the brazing material to melt. It is configured to solidify in the state filled in the gap of the site and to join between the metal members to be joined.

However, the conventional brazing method has a disadvantage in that the work process is complicated because the brazing material is melted by heating in a state where the brazing material is first placed on the object to be joined and then the flux is placed thereon. This is pointed out. In addition, there is also a problem that it is difficult to apply an appropriate amount of flux to a desired portion because the liquid flux applied in advance to the joint portion flows down from the surface of the metal member.

In order to solve the shortcomings of the conventional brazing method including the flux coating process, a flux-containing brazing material formed by mixing the brazing material and the flux into a predetermined shape is developed by the present applicant and registered in Patent No. 297609.

The patent evenly mixes chloride-based or fluoride-based flux powders with aluminum alloy powder, puts them in a molding container, and forges them to form a cylindrical billet, which is then preheated to a temperature of about 500 pipes or wire rods. Extruded in a predetermined form such as a brazing material and the flux is integrated to provide a brazing material molded.

When joining the metal member using the brazing material of the three-dimensional shape containing the flux of the patent, the brazing material produced in accordance with the shape of the joining portion of the metal member to be joined is placed on the joining portion, Since the bonding by melting is made, it can be seen that the disadvantages pointed out in the conventional flux coating method of brazing bonding are solved.

On the other hand, one of the factors that influence the economics of brazing joining is brazing temperature. When the brazing temperature is high, the cost for maintaining the high heating temperature is inevitably increased, and the metal member to be joined is exposed to high temperature. Brazing materials that can be melted at low temperatures are desired because of the deterioration of the characteristics of the internal tissues as they are exposed.

However, in the case of the flux-containing brazing material patent, both the aluminum alloy (melting point about 600 ° C.) and the flux (melting point about 550 ° C.) forming the brazing material exhibit a relatively high melting point. It is not economical in that heating temperature should be maintained above about 600 ℃.

Japanese Laid-Open Patent Publication No. 2001-138038 uses brazing materials made of Zn-Al alloys or Al-Si-Zn alloys and CsF-based fluxes to enable brazing bonding at temperatures of 500 ° C to 550 ° C, lower than conventional brazing temperatures. A brazing material is disclosed.

That is, in the Japanese patent, the brazing material is composed of Zn-Al or Zn-Al-Si alloy which is mainly composed of Zn (melting point: 419.6 ° C), which is one of low melting point metals, so that the melting point of the brazing material is 450 ° C to 550 ° C While showing a relatively low temperature while using a low CsF flux (specific example CsF-AlF ₃ ) with a melting point of 450 ° C to 550 ° C, brazing bonding at low temperature is possible.

By the way, although the Japanese patent has the advantage that brazing at low temperature is possible, the conventional brazing method of applying a liquid flux to the surface of the metal member to be joined and placing the brazing material thereon and heating it takes precedence. The problem presented in the flux coating method of the bar has remained as it is.

The present invention has been made in view of the above-mentioned disadvantages of the conventional brazing material, by mixing the brazing metal powder and the flux powder and processing it into a predetermined three-dimensional shape through a mechanical molding process, thereby eliminating the flux coating process during brazing bonding. The primary object of the present invention is to provide a brazing material containing flux, which aims to improve the joining quality by simplifying the work and controlling the flux appropriately.

In addition, another object of the present invention is to use a brazing alloy of a Zn-based alloy having a low melting point, and the flux mixed therewith is also obtained by using the brazing material itself in which the flux is contained by using a cesium fluoride-based (CsF) flux known to have a low melting point. It is to provide a brazing material for low temperature bonding to keep the melting point lower than the conventional brazing material to reduce the heat source cost and the bonding time consumed during brazing bonding.

Still another object of the present invention is to join by simply brazing by using a brazing material molded to match the shape of the joining portion of the metal member to be joined without a separate flux coating process at a relatively low temperature compared to the conventional brazing temperature. Low-temperature bonding with flux that allows the material of the target metal member to be easily brazed between dissimilar metals such as copper to aluminum, copper to stainless, aluminum to stainless, as well as homogeneous metals such as copper to copper and aluminum to aluminum It is to provide a brazing material for.

Figure 1 (a) to (d) is an embodiment of the process of manufacturing a ring-shaped brazing material of the present invention.

Figure 2 is a cross-sectional view showing the bonding process of the tube using the ring-shaped brazing material of Figure 1;

Figure 3 is a cross-sectional view showing the bonding process of the tube using a brazing material in the form of an embodiment of the present invention.

Figure 4 is a perspective view showing the bonding process of the plate using the brazing material in the form of one embodiment of the present invention.

((Description of the code for the main part of the drawing))

B, B ', B ". Brazing Material 1. Copper Pipe

1a. Socket for connection 2. Aluminum tube

3. Copper plate 4. Aluminum plate

The above object of the present invention is an alloy powder comprising 10-40% by weight of Al or Al + Si and Zn alloy powder having a balance of Zn, and containing 10-40% of the weight of the alloy powder. The mixed powder of the flux powder is achieved by the low temperature bonding brazing material containing the flux formed into a three-dimensional shape through mechanical processing.

At this time, the alloy powder is a binary alloy of Zn + Al or a ternary alloy of Zn + Al + Si, it is possible to lower the final brazing temperature of the brazing material by adopting Zn, a low melting point metal as a main component. In addition, Al or Al + Si added to Zn serves to reinforce strength and elongation as quality characteristics of the brazing material which Zn does not have.

At this time, the amount of Al or Al alloy added to Zn is appropriately 10 to 40% by weight. If only 10% is used, the strength and elongation of the brazing material is lowered, and if the content exceeds 40%, the brazing joint temperature is increased. There is this.

The alloy powder according to the present invention exhibits a melting point of about 450 ° C to 500 ° C.

In addition, the particle size of the alloy powder is preferably such that the size of less than 30 mesh (550㎛). When the particle size of the alloy powder is larger than the flux powder, coarse particles are preferably used because the fracture does not occur during secondary processing such as bending, punching or bending after extrusion, and plastic processing is easy. The powder should be kept in a range that does not prevent the powder from being uniformly dispersed. The particle size of the appropriate alloy powder selected in consideration of this point is 30 mesh or less.

In this case, the particle size distribution of the alloy powder preferably has a wide particle size distribution so as to improve the filling properties during billet manufacture and increase the extrusion density.

On the other hand, the flux constituting the brazing material of the present invention is a cesium fluoride-based (CsF), its melting point is 440 ℃ - to represent a range 500 ℃, its specific example may be mentioned CsAlF _4, in that in addition to CsAlF ₄ Flux of a composition in which a small amount of LiF or KAlF ₄ is mixed may be used.

The CsAlF ₄ has a melting point of 330 ° C. to 490 ° C. according to the content ratio between CsF and AlF, and the particle size of the flux powder is preferably in the range of 100 to 200 mesh. That is, the particle size of the flux powder is required to be relatively small compared to the particle size of the braze metal powder. The reason is that the compacted metal obtained by mixing the alloy powder and the flux powder into a predetermined shape is extruded into a predetermined shape. This is because the particles must be stretched and interconnected to maintain sufficient forming strength.

If the size of the alloy particles is similar to that of the flux particles and the size difference between the powder particles is not large, an increase in the oxide due to the increase in the surface area of the alloy particles cannot be avoided. This increase in oxide may interfere with the extrusion, making the extrusion itself difficult, and also may cause the fractured oxides to be present in the extrusion material and act as a break point of the extrusion wire that is extruded.

The content of the flux powder constituting the brazing material of the present invention is appropriately in the range of 10-40% of the weight of the alloy powder. If the content of the flux powder is less than 10%, the brazing material may not flow into the joint gap due to poor fluidity during brazing bonding. If it exceeds 40%, the fluidity is so good that there is a high possibility that the brazing material will flow out of the joint, resulting in poor bonding.

On the other hand, the present invention can be manufactured in the form of a paste by adding a liquid binder to the alloy powder and the flux powder in addition to the shape of the alloy powder and the flux powder is molded and extruded in a predetermined form.

As such, the brazing material composition in the form of paste according to the present invention includes 10-40% by weight of Al or Al + Si and the balance of Zn alloy powder of cesium fluoride-based flux powder is 10-40 of the weight of the alloy powder. %, The liquid organic binder is composed of 10 to 30% of the weight of the alloy powder, wherein the organic binder is characterized in that the weight ratio of the thermoplastic resin and the solvent for dissolving it is 1/1-1/100. .

Characteristics of the composition and particle size of the alloy powder and the flux powder in the brazing material of the paste form are the same as the brazing material that is extruded into a specific shape as described above.

However, in the case of the brazing material manufactured in the paste state, it is preferable that the particle size of the alloy powder has a smaller particle size than the brazing material of the three-dimensional shape, and the preferable average particle size is in the range of 100-200 mesh. If the particle size of the alloy powder is larger than 100 mesh, the paste itself is rough, which makes it difficult to apply on the joint surface of the base material to be bonded. On the contrary, when the particle size is smaller than 200 mesh, the surface area of the powder is widened, causing oxidation of the brazing material during brazing. There is this.

On the other hand, specific examples of the binder component in the liquid organic binder added in the brazing material of the paste form according to the present invention include a thermoplastic resin such as butyl polyacrylate. When butyl polyacrylate is used as a binder, it is preferable to use lower aliphatic alcohols such as methyl alcohol, ethyl alcohol, propanol, butanol, isobutyl alcohol, and isopropyl alcohol.

Mixing of the alloy powder and the flux powder according to the present invention may be performed by selecting any one of the following methods.

1. Method of drying by adding alloy powder for brazing during the reaction of producing liquid flux in solid phase.

2. When brazing alloy powder is manufactured by using atomizer device, flux is mixed in the cooling fluid used for quench solidification to impinge on the molten metal so that the flux is applied to the surface of the brazing alloy powder at the same time. How to.

3. Simple mixing of solid-state flux powder of several hundred microns and brazing alloy powder.

4. A method of preforming a braze alloy powder into a porous body and then immersing it in a liquid flux to inject flux into an internal cavity by using a capillary phenomenon or to apply flux to a surface, followed by drying and grinding.

The mixing of the alloy powder for brazing and the flux powder according to the present invention may be achieved through other methods known in the art in addition to the above method.

The mixing powder of the brazing alloy powder and the flux powder mixed through the mixing method as described above is primarily made of powder forging in a molding container, thereby forming a billet of a cylindrical shape or the like.

Subsequently, the billet formed of the mixed powder as described above is extruded into a three-dimensional shape in accordance with the quality characteristics of the wire rod, pipe, rod, plate, etc. by the extruder in the pre-heated state to about 500 ℃.

On the other hand, in the case of the paste-type brazing material according to the present invention, the alloy powder for brazing, the flux powder and the organic binder are mixed without undergoing the process of powder forging and extrusion molding as described above, which does not have a specific three-dimensional shape. It is present as a paste in the state.

Matters related to the purpose and technical configuration of the present invention and the resulting effects thereof will be more clearly understood by the following examples, and the present invention is not limited by the embodiments.

Example 1

A Zn-Al alloy consisting of Zn78% and Al22% by weight was prepared using an atomizer device with an alloy powder of 30 mesh or less. CsAlF ₄ , a cesium fluoride flux, was added to the alloy powder by 13% of the weight of the alloy powder to obtain a mixed powder (FIG. 1A) in which the alloy powder and the flux powder were uniformly mixed.

At this time, the melting point of the alloy powder was 480 ℃, the melting point of the flux was 450 ℃.

Subsequently, the mixed powder of the alloy powder and the flux powder was placed in a cylindrical molding container and powder forged to form a billet having a diameter of 85 mm and a length of 300 mm as shown in FIG.

Next, a pipe-shaped wire rod having an inner diameter of 8.2 mm and an outer diameter of 11.2 mm was extruded using a pipe molding extruder in a state in which the billet was preheated to about 500 ° C. At the time of hot extrusion as described above, the billet temperature of the extruded state becomes higher than the recrystallization temperature of the alloy powder, the alloy powder and the flux become semi-melted state, and the alloy powder is deformed, resulting in the bonding between the alloy powders, resulting in the brazing that is extruded. The ash will maintain a certain strength.

Finally, as shown in (d) of FIG. 1, the pipe-shaped wire rod was cut to a width of 1.5 mm to produce a plurality of ring-shaped brazing members having the same shape and size.

Example 2

This embodiment relates to an example in which an aluminum tube and a copper tube which are dissimilar metals are joined using the brazing material obtained in Example 1 above.

The copper object 1 and the aluminum tube 2 to be joined are shown in FIG. 2, which have the same outer diameter and thickness, the inner diameter of which is 8 mm and the thickness of 0.8 mm. The copper pipe (1) is provided with a connecting socket (1a) consisting of a 9 mm deep expansion pipe at one end for connecting the aluminum pipe (2).

The ring-shaped brazing material B obtained in Example 1 was inserted into the outer circumferential surface of one end of the aluminum tube, and the same portion was inserted into the connection socket 1a of the copper tube 1 to make the primary coupling between the two bodies. To lose. Subsequently, the two bonded bodies were placed inside an electric furnace and heated at 520 ° C. for 5 minutes. At this time, nitrogen gas was supplied into the furnace at an injection rate of 2 m 3 / min.

After the heating was completed, the bonding target material was taken out of the furnace to allow cooling at room temperature. As a result of observing the junction of the cooled object to be joined with the conduit, the brazing material was completely melted by the gap between the junction of the copper tube and the aluminum tube, specifically, the inner peripheral surface of the copper tube and the aluminum and outer peripheral surface of the part inserted into the socket. It was confirmed that coagulation occurred in the soaked state.

When the pressure resistance test was conducted on the pipe body in which the joint was completed, the joint was satisfactory under an internal pressure of 140 Kgf / cm 2, but a rupture occurred on the aluminum tube at a point far from the joint. And, as a result of the tensile test, the joint was good, while fracture occurred on the aluminum tube at the part away from the joint. Accordingly, it was found that the bonded portion joined using the brazing material according to the present invention had a higher strength than the base metal and maintained a very good bonded state.

Example 3

A brazing material was manufactured by the same composition and manufacturing process as in Example 1 except that the flux was replaced with a flux in which a small amount of LiF was mixed with CsAlF ₄ in order to enhance the effect of the flux. The mixing ratio of CsAlF ₄ and LiF was 10: 1 (weight ratio). Among the flux components, Li exhibits properties of enhancing spreadability during brazing bonding, preventing oxidation of the bonding portion, removing oxygen and sulfur groups in the metal, and improving thermal conductivity. After the brazing joint of the tube was made through the same joining process as in Example 2, the internal pressure test and the tensile test of the joint of the tube were carried out by the same test method as in Example 2, and the results were equal to those of Example 2. Bonding results were obtained.

Example 4

A brazing material was manufactured by the same composition and manufacturing process as in Example 1 except that the flux was replaced with a flux in which a small amount of KAlF ₄ was mixed with CsAlF ₄ in order to enhance the effect of the flux. The mixing ratio of CsAlF ₄ and KAlF ₄ was 10: 1 (weight ratio). The same joining process as in Example 2 was taken to allow the conduit to be joined, but the temperature of the electric furnace was set to 550 ° C. and heated for 8 minutes. By the same test method as in Example 2, the pressure resistance test and the tensile test of the joints of the tubular body were carried out.

Example 5

3 to prepare a brazing material having the same composition as in Example 1, but in a mechanical molding process using a mixed powder, instead of a ring shape as in Example 1, forming a brazing material (B ') having a diameter of 3mm and a wire shape (B') as shown in FIG. As described above, the end portion of the brazing material B 'is brought into contact with the junction between the copper tube 1 and the aluminum tube 2 to be heated, but the brazing is performed by heating with a gas torch in the air without using an electric furnace. By the same test method as in Example 2, the pressure resistance test and the tensile test on the joints of the tubular body were carried out, and as a result, good joint results at the same level as in Example 2 were obtained.

Example 6.

The brazing was performed in the same composition as in Example 1 and in the same manufacturing process as in Example 2, except that the composition of the alloy powder was Zn: Al: Si in a weight ratio of 75: 18: 7. At this time, the melting point of the alloy powder was 492 ℃, and the joint test on the pipe joint by the same test method as in Example 2 to obtain a good joint result of the same level as in Example 2.

Example 7.

All the same as in Example 6, but the stainless steel pipe instead of the copper pipe to be joined, the properties of the junction showed the same level as in Example 6.

Example 8

First, an alloy powder having an average particle size of 150 mesh was obtained using an Zn-Al (78:22, weight ratio) alloy using an atomizer device. The melting point of the alloy powder is 480 ° C. A paste-type brazing material was prepared by mixing CsAlF ₄ , a cesium fluoride-based flux, and butyl polyacrylate (a mixed weight ratio of butyl polyacrylate: methanol: 1:10) as a binder in a weight ratio of 70:18:12. It was.

On the copper plate 3 of 10 mm (width) x 50 mm (length) x 3 mm (thickness) as shown in Fig. 4, 2 g of the brazing material B " The plate 4 (8 mm (bottom) x 10 mm (height) x 0.8 mm (thickness) x 40 mm (length)) was stacked and heated in a furnace at a temperature of 550 ° C. for 10 minutes and then cooled at room temperature. The nitrogen gas injection rate into the inside was 2 m <3> / min.

As a result of the brazing operation as described above, the brazing material was completely melted and solidified between the copper plate 3 and the aluminum plate 4. A break occurred in the plate). This shows that the strength of the joint is higher than that of the base material and maintains a very good bonding state.

Example 9

In order to enhance the flux effect in Example 8, a flux having a small amount of LiF added to CsAlF ₄ was used, wherein the mixing ratio of CsAlF ₄ to LiF was 10: 1 by weight. All other composition ratios, manufacturing steps, and bonding steps were the same as in Example 8. The fracture test results for the joints showed the same results as in Example 8.

The brazing material containing the flux of the present invention, by mixing the brazing metal powder and the flux powder into a predetermined three-dimensional shape through a mechanical molding process to simplify the brazing operation by eliminating the flux application process during brazing bonding and flux of There is an advantage that can improve the joining quality through proper control.

In addition, the present invention uses a Zn-based alloy having a low melting point as a brazing alloy, and the melting point of the brazing material itself integrated with the flux is contained by using a flux of cesium fluoride (CsF) based flux known to have a low melting point. It is possible to reduce the heat source cost and the bonding time consumed when brazing by maintaining the low compared to the conventional brazing material.

In addition, the present invention is a metal to be joined by simply brazing by using a brazing material molded in accordance with the shape of the joint portion of the metal member to be joined without a separate flux coating process at a relatively low temperature compared to the conventional brazing temperature The material of the member enables easy brazing bonding between dissimilar metals such as copper to aluminum, copper to stainless, aluminum to stainless, as well as homogeneous metals such as copper to copper and aluminum to aluminum.

Claims (9)

In the brazing material for joining homogeneous or dissimilar metal members, a Zn alloy powder containing 10 to 40% by weight of Al or Al + Si and a balance of Zn contains 10 to 40% of the weight of the alloy powder. A brazing material for low temperature bonding containing flux, wherein the mixed powder of the alloy powder and the flux powder is formed into a three-dimensional shape through mechanical processing of powder forging and extrusion molding. The brazing material of claim 1, wherein the alloy powder has a particle size of 30 mesh (550 μm) or less, and the particle size of the flux powder is smaller than that of the alloy powder. The brazing material of claim 1, wherein the flux powder is CsAlF ₄ . The brazing material of claim 1, wherein the flux is a composition in which LiF or KAlF ₄ is mixed with CsAlF ₄ in a weight ratio of less than 10%. The brazing material for flux bonding according to claim 1, wherein the three-dimensional shape is any one of a rod, plate, pipe, wire or ring. In the brazing material for joining homogeneous or dissimilar metal members, Zn alloy powder containing 10 to 40% by weight of Al or Al + Si and remaining Zn contains cesium fluoride flux powder containing 10 to 40% of the weight of the alloy powder. In the paste state, the liquid binder contains 10-30% of the weight of the alloy powder, wherein the liquid binder has a weight ratio of the organic binder component and the solvent dissolving it in the range of 1/1-1/100. Brazing material for low temperature bonding containing flux. The brazing material for flux bonding according to claim 6, wherein the alloy powder has a particle size of 30 mesh or less and a flux powder has a particle size of 100-200 mesh. 7. The brazing material for flux bonding according to claim 6, wherein the flux powder is CsAlF ₄ . 7. The brazing material of claim 6, wherein the flux is a composition in which CsAlF ₄ is mixed with LiF or KAlF ₄ in a weight ratio of less than 10%.