JPS59206157A - Brazing method of aluminum alloy material - Google Patents

Abstract

PURPOSE:To perform satisfactory brazing without affecting adversely the fluidity and reactivity of a flux in the stage of joining by brazing Al alloy materials contg. Mg by thermally spraying a brazing filler metal on the surfaces to be joined then brazing the materials. CONSTITUTION:A brazing filler metal is thermally sprayed on the surfaces to be joined of Al alloy members contg. Mg in the case of brazing the members to be joined consisting of an Al alloy contg. Mg by using a reactive flux composed essentially of a fluoride compd. The above-described flux is interposed between the surfaces to be joined of said members and the members are heated to the temp. above the m.p. of the brazing filler metal and below the m.p. of the members and are brazed. The reactivity of the flux is thus stabilized and the members are surely joined with virtually no adverse influence on the fluidity thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for brazing aluminum alloy materials, and is capable of simply and effectively brazing aluminum alloy materials, at least one of which contains gin, using non-corrosive 7 lacs. It is intended to provide a method.

In recent years, aluminum and its alloy materials have been rapidly developed and popularized, and are widely used in heat exchangers for vehicle width and other applications such as evaporators, condensers, and radiators, and are known for their excellent light weight and transmission properties. Thermal properties are utilized.

By the way, in order to attach the tubes and fins that are the members of these heat exchangers, as well as the nirasol and reinforcing materials provided thereon, brazing is performed using a reactive flux that provides high bonding strength and is easy to work with. 9. This flux is applied to remove oxides on the surfaces to be joined and to improve the wettability of the brazing metal to the surfaces to be joined, and in particular, it improves the wettability of the brazing metal. This is an important characteristic in order to properly spread the brazing material on the surfaces to be joined and to obtain a joint with few defects and excellent durability using a small amount of brazing material. However, chloride-based fluxes have traditionally been used as fluxes with these characteristics, but since these chloride-based fluxes are highly corrosive to However, it is difficult to completely eliminate this in a device with a complicated structure such as the above-mentioned heat exchanger, and there is a high risk of corrosion due to residual slack and reaction residue. In addition, due to these circumstances, fluxes made of non-corrosive fluoride-based compounds have recently been developed in place of chloride-based fluxes. If it is, flux fluidity during brazing will be hindered.
Oxides are not removed sufficiently from the surfaces to be joined, and furthermore, the adhesion of the brazing filler metal to the surfaces to be joined is deteriorated, so there is a drawback that the joint strength of the joint cannot be reliably obtained.

The present invention was created after repeated studies in view of the above-mentioned circumstances. That is, the present inventors studied the reasons why the fluidity of the flux decreases when brazing parts to be joined of an alloy containing sulfur using the above-mentioned fluoride flux. This fluoride-based flux reacts with Gin in the parts to be joined, changing the composition ratio of the flux, and when heating during brazing, the flux exhibits its original fluidity and reactivity in the maximum heating temperature range. I learned that I would no longer be able to get it. That is, based on this knowledge, the present inventors thermally sprayed a brazing material on the surfaces to be joined when brazing At alloy materials containing Gin using the fluoride-based flux. Later, he discovered that good brazing could be achieved without impairing the fluidity and reactivity of the flux used for brazing, and completed the present invention.

In the present invention, in brazing parts to be joined, at least one of which is made of an At alloy containing Gin, using a reactive flux mainly composed of a fluoride compound,
After spraying a brazing filler metal onto the surface of the alloy member containing the target, the member to be joined (3) is attached with the 7 lux interposed between the corrugated surfaces of the member to be joined. The method is characterized in that the members are then heated to a temperature above the melting point of the brazing material and below the melting point of the members to be joined to perform brazing. That is, according to the present invention, the progress of the reaction between the homogeneous elements in the welded members and the flux is suppressed until the sprayed brazing filler metal melts, and the uniform elements in the welded members are reduced to "20 S "i. ”s
Since the formation of oxides such as 04 is inhibited, the reactivity of the flux is stabilized, and its fluidity is hardly hindered, allowing for reliable bonding.

To explain in more detail the method of the present invention as described above, the 7 lux consisting of fluoride compounds in the present invention includes, for example, KF.

KμF4, a mixture of Tora compounds containing NF3 as the main component
Plain or KAlF3, K3AIF, A/
F' refers to a mixture containing at least two or more of the following. Of course, the above-mentioned flux may contain other elements or compounds as impurities, or it may consist of the above-mentioned compounds to which elements or compounds other than those mentioned above have been added for the purpose of lowering the melting point (4) or for other purposes. The flux is included in the flux made of a fluoride compound in the present invention.

Such flux for brazing elbows contains a plurality of compounds in predetermined proportions so as to have good reactivity and fluidity at brazing temperatures.

When such a fluoride-based flux is used to braze alloy parts to be welded containing Gin, the reactivity and fluidity of the flux are reduced due to the components in the flux, such as the above-mentioned NF4. Compounds that easily react with Gin react with Gin in the alloy and change into KAIgF3, thereby changing the original composition ratio of the flux. When reacting with moisture, dense oxides such as A4Q% AIg and 4/2o4 are formed on the surface of the component. As mentioned above, it is considered to impair the sex. However, when using such a fluoride-based flux to braze and join parts containing At alloy to be welded, it is necessary to spray the brazing metal in the direction of the parts to be joined in advance and then perform the brazing process. In some cases, it is possible to prevent the flux from coming into contact with the bare metal of the surfaces to be joined until the sprayed brazing filler metal melts, so that the reaction between the flux and the metal in the raw metal of the parts to be joined can be minimized. Further, such a thermal sprayed brazing material suppresses oxidation of the rod in the direction to be joined, so it works well without impairing the fluidity and reactivity inherent to the flux, and preferred brazing can be easily achieved.

BA4343, BA as a brazing material to be thermally sprayed on the surface to be joined
Al-8t series such as 4045, Al − such as BA4145
, 'Et-Cu type, and *-St-X type brazing materials, and one of them is appropriately selected and used in consideration of the melting point of the parts to be joined, the usage condition of the brazed product, etc.

Furthermore, by thermally spraying such a brazing material onto the surfaces to be joined, a dense brazing layer can be formed, and this also prevents flux from penetrating into the surfaces to be joined.

When the thickness of this thermal sprayed brazing filler metal is around 50 μm or more, it is possible to suppress the reaction between the flux and the metal in the parts to be joined, and a good joint condition can be obtained. If the amount of brazing filler metal is insufficient, for example when fitting and joining pipes with a gap between the surfaces to be joined, the thickness of the thermally sprayed brazing filler metal may be increased or It is also possible to replenish the brazing material by separately disposing a brazing material near the surfaces to be joined.

Furthermore, if the thickness is thermally sprayed, the brazing filler metal may peel off and fall off, so it is preferable that the upper limit of thermal spraying be about 1000 μm. In the thermal spraying method, the brazing material is melted by a heating means such as a flame, and the material is covered by spraying a flame or a material such as gas.
It is preferable to thermally spray the brazing material by heating it to about 0° C., as this increases the adhesion of the brazing material and prevents troubles such as cracking and peeling of the brazing material (7). Note that this thermal spraying can be carried out by changing the direction of spraying as appropriate, so that it is possible to accurately treat many complex parts of the wax.

After applying flux to at least one of the homogeneous M alloy members to be welded together with the other member to be welded and having the brazing filler metal sprayed on the surfaces to be welded as described above,
After assembling or holding it in the desired shape, apply 7 lux. The flux can be applied by commonly used methods such as brush coating, spray coating, and dip coating.

The members to be joined that have been assembled through the above-mentioned steps are heated and brazed to a temperature above the melting point of the brazing material and below the melting point of the members, but the heating rate at this time,
The minimum heating temperature is determined by the composition of the flux and brazing material used, and the maximum heating temperature is determined by the composition of the members to be joined. That is, heat brazing is usually performed at a heating temperature of 10 to 40(8)°C above the melting point of the brazing material and 40 to 50°C below the melting point of the members to be joined. Further, the heating rate is determined by the shape and size of the assembled members to be joined. In the case of general electric furnace brazing, it is 10-b. However, such brazing method is called torch brazing,
Any conventionally known method such as high frequency brazing or furnace brazing can be used.

When brazing in a furnace, the flux reacts with oxygen and moisture in the atmosphere in the furnace, reducing the reactivity and fluidity of the flux. % or less, preferably with nitrogen gas, hydrogen gas, ammonia gas, etc. with a water content of 0.008% or less. Specific examples of the method of the present invention will be described below.

As shown in FIG. 1, a corrugated fin 2 is made up of a meandering flat tube 1 through which a heat exchange fluid flows, and a thin plate for promoting heat exchange with the fluid between the parallel parts of the flat tube 1. A condenser for automobile air conditioning is made up of a flat tube 1 and a Nirasol 3 connected to other piping on the other side, and a reinforcing member 5 having a U-shaped cross section as shown in FIG. 3 formed to cover the bent portion 1a of the flat tube 1. Fluoride flux T
It was manufactured by brazing using.

The composition of each member and the ratio of flux expressed as a single compound are shown in Table 1.

(11) (12) Each of the above-mentioned members was degreased by immersion in trichlene and steam cleaning. Thereafter, the material was heated to about 200 DEG C. using Nirasol 3 and a 5-piece U-shaped reinforcing burner, and a brazing filler metal 4 was sprayed onto each joint surface using an oxygen-acetylene flame spraying device. Note that parts other than the joint surfaces were masked to prevent them from being coated.

The composition, coating thickness, and thermal spraying conditions of the brazing filler metal 4 are as shown in Table 2 below.

Table 2 Next, spray the Clax-F slurry on the brazing metal sprayed surface of the U-shaped reinforcing material 5 (coating amount: 10,
! i'r/m') I did. After that, each member is assembled as shown in FIGS. 1 and 2, and a brazing filler metal 6 having the same composition as the sprayed brazing filler metal 4 is placed between the Niraglu 3 and the flat tube 1 as shown in FIG. Further, the above-mentioned flux T was applied to this part using lpr.

The above-mentioned 7
After spraying Lux 7 (coating amount: 79 r/m), drying at 150°C for 10 minutes, then 580-625°C.
The brazing process was performed using a continuous brazing furnace set at . The brazing conditions are shown in Table 3 below.

In this way, 100 capacitors were brazed and manufactured. According to the leakage test results of these 100 units, no leakage was found in any of the 100 units, and all of them passed the test.

In addition, vibration inspection (44G-8hr vibration),
and repeated pressure test (0 9G-30#/ff1G
, 10,000 times), but all the tests passed without any damage to the nipple or the welded portion of the reinforcing member.

Furthermore, we conducted a bursting pressure test in which we pressurized the inside of the flat tube and nipple to see which part would break, but in this burst pressure test, although the flat tube was broken, the joint between the flat tube and the nipple was not detected. It did not say that it would be destroyed.

By the way, about 70% of the same capacitors that were brazed and bonded without being coated with a brazing material under the above conditions failed the helium leak test, and about 2 capacitors failed the vibration test. -3C = Break 4 - EIA Kenshu Shukuyoban By using the non-corrosive fluoride compound flux according to the present invention as explained above, homogeneous alloy members can be effectively and appropriately brazed, As a result, sufficient durability can be ensured for this type of heat exchange equipment, etc., and the intended purpose of soldering can be achieved in a rational manner, so this invention is industrially very effective.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, and FIG. 1 is a plan view partially showing the structural relationship of the main parts of a condenser for automobile air conditioning as an embodiment of the method of the present invention, and FIG. 2 shows the nipple thereof. FIG. 3 is a partial perspective view of the reinforcing material mounting portion, and FIG. 4 is a sectional side view thereof. However, in these drawings, 1 is a flat tube, 2 is a col y
3 is a nipple, 4 is a thermal sprayed brazing material, 5 is a reinforcing material, 6 is a brazing material, and 7 is a flux. (15) 1st / circle / 2nd circle 〆 ′ 47 °7,〈 da °−7? J Engai 4 mouths

Claims (1)

[Claims] When brazing aluminum alloy materials, at least one of which contains gin, using a reactive flux mainly composed of fluoride compounds, a brazing filler metal is thermally sprayed on the surfaces of the aforementioned sai-containing aluminum alloy materials to be joined. After that, each member is assembled with the flux interposed therebetween, and then brazing is performed by heating to a temperature above the melting point of the brazing material and below the melting point of the aluminum alloy material. is the method.