JP2662034B2 - Low temperature vapor phase brazing of Al or Al alloy - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a low-temperature brazing method of Al or an Al alloy, for example, in the production of an automobile heat exchanger, the performance of the brazed member is evaluated. It is intended to improve the manufacturing cost and to reduce the manufacturing cost.

[Conventional technology]

Usually, the brazing of Al or Al alloy is
Alternatively, an Al alloy member is fixed via a brazing material having a lower melting point than these Al or Al alloy members to form an assembly, which is higher than the melting point of the brazing material and higher than the melting point of the Al or Al alloy member to be joined. This is done by heating to a lower temperature. And as a brazing material for low-temperature brazing,
Zn and Zn-Al alloys, Sn-Pb alloys, Sn-Cd alloys and the like are used. In addition, the heat exchanger made of Al does not use Sn-Pb-based alloys and Sn-Cd-based alloy brazing filler metals, which have poor corrosion resistance.

There are various conventional low-temperature brazing methods that use Zn and Zn-Al-based alloys as brazing materials.However, when brazing complicated shapes such as heat exchangers, brazing in a low-temperature furnace is required. A brazing method and a low-temperature reaction brazing method are used. In brazing in a low-temperature furnace, a member made of Al or an Al alloy is assembled, a Zn-based brazing material is placed at a joint, and a flux composed mainly of ZnCl ₂ is dissolved in an organic solvent such as alcohol and applied. And it heats above the melting temperature of a brazing material and brazes. For low-temperature reaction brazing, assemble a member made of Al or Al alloy, immerse it in a bath in which a flux mainly composed of ZnCl ₂ is dissolved in an organic solvent such as alcohol, and heat in a furnace to a temperature higher than the melting point of ZnCl ₂ and brazing. I do. In this case, Zn precipitated from the flux on the surface of the Al material becomes a brazing material.

[Problems to be solved by the invention]

The conventional low-temperature brazing method inevitably requires a coating process to adhere the flux to the surface of the assembly, and the applied flux often falls off the assembly during transport of the assembly to the next process. Therefore, the yield of the flux used effectively is low.

In addition, the concentration of the flux solvent to be applied is as high as 50 to 70%, and since an alcohol-based organic solvent is used for the solvent,
High flux cost. This flux is ZnCl
Since it is mainly composed of _two, it is corrosive, and it is necessary to sufficiently remove the flux after brazing.

In addition, the surface of the brazed heat exchanger
Although Zn is deposited, the surface is dirty and the commercial value is inferior due to the high concentration. When a corrosion test is further performed, the corrosion of the through-hole of the tube is prevented, but, for example, the joint between the fin and the tube is easily corroded, and the fin serving as a heat radiator is peeled off, thereby impairing the function as a heat exchanger.

As described above, the conventional low-temperature brazing method is inferior to other brazing methods using an Al-Si brazing material in terms of brazing cost and performance due to the application of the flux solution mainly composed of ZnCl _2. Therefore, it has not been widely used as a brazing method for heat exchangers.

[Means for solving the problem]

In view of this, as a result of various studies, the present invention has developed a vapor phase brazing method of Al or an Al alloy which does not require a step of directly applying a flux to an assembly to be joined and can be brazed at a low temperature. In a method of brazing Al or an Al alloy through a Zn-based brazing material, the method comprises brazing these members in a non-oxidizing atmosphere in which steam emitted from a melt of ZnCl ₂ is present. is there.

[Action]

By placing the assembly of the members to be joined in a non-oxidizing atmosphere in which steam from the melt of ZnCl ₂ exists, this steam adheres to the assembly in a trace amount and uniformly, and the Al on the surface is reduced. Since the oxide film is broken, the wetting of the wax is promoted, so that the wax flows uniformly and a uniform fillet is formed at the joint of the assembly.

Then, in order to generate this steam, ZnCl ₂ may be put in advance in a furnace where brazing is performed, and when the furnace is heated, the heat may be simultaneously evaporated and the steam may be evaporated outside the furnace. It is also possible to use a method in which nitrogen gas or the like is generated and supplied into the furnace as a carrier.

Furthermore, the presence of this vapor in a non-oxidizing atmosphere allows the assembly to be completely covered with vapor,
The steam density is low and the flux consumption can be reduced. As the non-oxidizing atmosphere, for example, nitrogen, argon, carbon monoxide or any other atmosphere can be used.

In order to carry out the present invention, it is preferable to use a furnace with a high degree of sealing. Even in a furnace with a low degree of sealing, the assembly to be joined is put together with ZnCl _{2 in a} container made of stainless steel or the like and brazed. It can be easily brazed by heating. In this case, since the vapor emanating from the ZnCl ₂ melt is confined in the container, the consumption thereof is extremely small, so that it is possible to perform brazing any number of times using the container used for brazing once.

As the Zn-based brazing material, pure Zn, Zn-Al-based, Zn-Al-Si
A brazing material obtained by adding Bi, Sn, Cd, Pb, Be, Mg, or the like to a Zn-based brazing material, or any other Zn-based brazing material can be used. These brazing materials can be used in the form of plate, rod, powder, or Al or Al alloy coated with these brazing materials. As the coating method, any method such as a hot pressing method, a thermal spraying method, and a hot-dip plating method may be used.

The brazing temperature is required to be heated to at least 590 ° C. or more when using an Al—Si brazing material. In the present invention, for example, a melting point of 381 ° C. is used for a Zn-5% Al brazing material. 400 ° C is sufficient as the brazing temperature.

Also, Al or Al alloy that can be used in the method of the present invention means any alloy having a melting point higher than the melting temperature of the brazing filler metal.

By using the vapor of ZnCl ₂ in this way, brazing is possible without directly applying flux to the assembly,
Due to the structure of the assembly, it is generally difficult to braze the inside of a heat exchanger having a joint inside the assembly by steam. Therefore, in such a case, a conventional chloride-based flux or a fluoride-based flux such as potassium fluoroaluminate complex is applied to the joint inside the assembly in advance and dried, and these fluxes are applied to the joint outside the assembly. It is effective to braze in a non-oxidizing atmosphere in which ZnCl ₂ vapor is present without coating. Further, as described above, the application of a part of the chloride-based flux or the fluoride-based flux is not limited to the inside of the assembly, but may be performed on the outside, for example, when the brazing is difficult due to the complicated shape of the joint and only steam. These conventional fluxes may be applied directly.

〔Example〕

 Next, examples of the present invention will be described.

Example 1 An inverted T joint test piece shown in FIG. 1 was assembled and brazed by the method of the present invention. That is, JISA3003 (Al-Cu0.05 ~ 0.20% ~
Mn 1.0-1.5% alloy) with Zn-5% Al on both sides
1mm thick rolled plate consisting of brazing sheet (1) clad with 10% alloy brazing material, JIS A1050, JIS
Thickness 1 made of A3003, JIS A6951 and Al-0.5% Cu alloy
The rolled plate (2) of mm was assembled and degreased with an organic solvent.

Then, the assembly was placed on a stainless steel tray on which 500 g of ZnCl ₂ was placed per 1 m ³ of the brazing furnace, and the dew point was -40.
400 ° C with a nitrogen gas atmosphere with an oxygen concentration of 100 ppm
Insert this assembly into an electric furnace held at
Brazing was performed by heating at 400 ° C. for 5 minutes.

The joined material after the above brazing was taken out of the furnace and the brazing condition was examined. Good results were shown in Table 1 with good brazing conditions and poor results with x. Table 1 also shows the case where the surface state could not be completely observed, and x the case where the surface was uneven and dark and dirty.

For comparison, the assembly after degreasing was joined by a brazing method in a low-temperature furnace as a conventional method. That is, the assembly is ZnCl
The assembly was immersed in a 66% propyl alcohol solution of a _two-part flux, and the assembly was inserted into an electric furnace maintained at 400 ° C., and the assembly was heated at 400 ° C. for 5 minutes to perform brazing. The results are summarized in Table 1.

As is evident from Table 1, all of the methods Nos. 1 to 4 of the present invention exhibited good brazing properties and a good surface condition. On the other hand, in the conventional methods No. 5 to No. 8, Zn diffused in a large amount to the surface of the joint, so that the surface state was dirty.

Example 2 As shown in FIG. 2, a tube material (3) made of JIS A1050 (Al 99.5% or more), which was hot-extruded into a tube by a conventional method, was bent in a meandering shape, and the meandering tube material (3) was bent. A corrugated fin (4) consisting of a brazing sheet with a thickness of 0.16 mm clad in a 10% ratio of Zn-5% Al alloy brazing material on both sides with a JISA3003 alloy as the core material, and further with an Al-4.3% Z
A connector (5) made of an n-1.3% Mg alloy was TIG-welded using an A1070 welding rod to assemble a serpentine-type capacitor, degreased with an organic solvent, and brazed by the method of the present invention. That is of brazing furnace inner volume of 1m ³ per 500g
The assembly was placed on a stainless steel tray on which ZnCl ₂ was placed, and the atmosphere was replaced with a nitrogen gas atmosphere with a dew point of −40 ° C. and an oxygen concentration of 100 ppm, and the assembly was inserted into an electric furnace maintained at 400 ° C. To heat the assembly at 400 ° C for 5 minutes to perform brazing, take it out of the furnace and cool it to remove traces of Cl
It was washed with water at 80 ° C. for 1 minute and dried.

The appearance of the surface and the state of brazing of the capacitor were examined and evaluated in the same manner as in Example 1. These results are
It is shown in the table. Thereafter, in order to evaluate the corrosion resistance of the condenser, a CASS test based on JISH8681 was carried out for 500 hours.

For comparison, the characteristics of the capacitor assembly shown in FIG. 2 which was brazed by a conventional method were investigated.

That is, the condenser shown in FIG. 2 was degreased with an organic solvent, immersed in a 66% propyl alcohol solution of a flux mainly composed of ZnCl ₂ , and inserted into an electric furnace maintained at 400 ° C. to assemble. The material was heated at 400 ° C. for 5 minutes to perform brazing, taken out of the furnace, cooled, washed with hot water at 80 ° C. for 10 minutes and dried to remove a large amount of Cl adhering. This capacitor was subjected to the same evaluation tests as described above, and the results are shown in Table 2.

As is clear from Table 2, the surface of the capacitor after brazing according to the method of the present invention was clean and the brazing condition was good. Furthermore, the joint between the tube and the fin did not peel off, and the corrosion resistance was good.

On the other hand, the capacitor according to the conventional method had good brazing properties, but had irregularities on the surface and was dark and dirty. Further, the joint between the tube and the fin was completely peeled off by corrosion, and the corrosion resistance was poor.

〔The invention's effect〕

Thus, according to the present invention, for example, compared to the conventional low-temperature brazing method, it is possible to shorten the manufacturing process of a heat exchanger such as an automobile,
Since the consumption of the flux is reduced, the production cost is reduced. In addition, since the surface after brazing is clean, the commercial value is high, and since the corrosion resistance is excellent, the life of the heat exchange performance is long, and the quality is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an inverted T joint test piece, and FIG. 2 is a side view showing an example of a serpentine type capacitor. DESCRIPTION OF SYMBOLS 1 ... Preserving sheet 2 ... Rolled plate 3 ... Tube material 4 ... Fin 5 ... Connector

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-35874 (JP, A) JP-A-3-90273 (JP, A) JP-A-3-90274 (JP, A) JP-A-3-90274 146261 (JP, A) JP-A-3-146262 (JP, A) JP-A-3-146263 (JP, A) JP-A-2-284767 (JP, A) JP-A-60-238081 (JP, A) JP-B 63-42547 (JP, B2)

Claims (1)

(57) [Claims] 1. A method of brazing Al or an Al alloy through a Zn-based brazing material, characterized in that these members are brazed in a non-oxidizing atmosphere in which steam from a ZnCl ₂ melt exists. -Temperature vapor-phase brazing method for Al or Al alloy.