JPS63132767A - Brazing method - Google Patents

Abstract

PURPOSE:To abbreviate the drying stage after coating a flux by coating a fluoride flux with an electrostatic powder body coating under nonaqueous atm. in case of brazing the body to be brazed by heating it by joining each other. CONSTITUTION:A coating booth 3 is provided at an optimum position on the conductive net conveyor 2 transferring the body 1 to be brazed and the electrostatic spraying gun 5 of an electrostatic powder spraying coating machine 4 is set to the ceiling thereof. The fluoride flux 6 to which an electric charge is given at the specified place is coated with its spraying by this static spraying gun 5 on the body 1 to be brazed being transferred with the net conveyor 2. The pure Al alloy of 1050, etc., Al-Mn alloy of 300, etc., are used for the body 1 to be brazed and for the fluoride flux 6 those which contain KAlF4, etc., are used. The fluoride flux only can thus be uniformly coated on the surface of the body 1 to be brazed with its dry state under nonaqueous atm. and the dew point of the brazing conditions of the case of brazing by heating in a heating furnace is maintained at about -40 deg.C.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a brazing method, and more particularly to a brazing method in which a fluoride-based flux is applied to an object to be brazed in a non-aqueous atmosphere. .

Conventional Techniques The method for brazing objects to be brazed, such as aluminum-based materials, is usually to degrease and clean the aluminum-based materials to be brazed together in a degreasing/cleaning process, and then to remove these aluminum-based materials. are temporarily assembled so that they are joined at the joints, and a predetermined fluoride-based flux, such as a slurry (water suspension) of potassium aluminum fluoride salt, is applied to the temporarily assembled aluminum materials by spraying or dipping. After sufficiently drying at 100 to 150°C, it is introduced into a heating furnace, and heated under an atmosphere of inert gas such as nitrogen gas with an oxygen partial pressure of less than 1.0009 pm, a heating temperature of 600 ± 5°C, and a dew point of -40°C. When is heating and brazing performed under brazing conditions?

In such a brazing method, the brazing performance on a given day is determined by the brazing atmosphere and the amount of flux, and in particular, the dew point in the brazing atmosphere has a very large effect, and the higher the dew point, the more likely brazing defects will occur. Become,
In order to ensure good brazing properties, it is necessary to maintain an appropriate dew point of -40°C.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional method, a slurry of the fluoride flux is prepared in the process of applying the fluoride flux to the object to be brazed, and this slurry is applied using a spray method or Since the slurry is applied to the object to be brazed using a dipping method, it is necessary to dry it to remove moisture after applying the slurry.
This drying step had a problem in that strict and high-level drying was required in order to maintain the dew point of -40° C. under the brazing conditions in the subsequent heating step.

Moreover, in this conventional method, the fluoride flux not only has extremely low solubility in water but also has a high specific gravity. It tends to settle, and in order to maintain the slurry in a uniform state during this flux application process, it must be constantly stirred or otherwise maintained in a suspended state. Also, since it is applied to the object to be brazed in the form of a slurry, The slurry of fluoride flux attached to the object to be brazed tends to flow together with water, which tends to cause unevenness in the amount of fluoride flux attached to the surface of the object after the drying process. As a result, there was a problem in that it was difficult to uniformly apply the fluoride flux to the surface of the object to be brazed.

By the way, Japanese Patent Publication No. 58-27.037 states that as a method for applying flux, ``Both a flux and a resin can be applied in a dry state by an electrostatic method, and then this can be baked.'' Although there is a description, the purpose of this is to bake and fix flux to a flat object to be brazed with resin, and the amount of flux used is 175 to 350 g/TIt, which is not practical. It's not a thing.

Therefore, an object of the present invention is to apply only fluoride flux to the surface of the object to be brazed in a dry state in a non-aqueous atmosphere, thereby improving the brazing conditions when heating and brazing in a heating furnace. To provide a new brazing method which makes it easy to maintain the dew point at -40° C., can omit a drying step, and can almost uniformly apply a fluoride flux to the surface of an object to be brazed. It is in.

[Means for Solving the Problems] That is, the present invention applies a fluoride flux to the objects to be brazed to each other, and when the objects to be brazed are bonded to each other and brazed by heating. , is a brazing method in which a fluoride flux is applied to the object to be brazed by electrostatic powder coating in a non-aqueous atmosphere.

The object to be brazed to which the brazing method of the present invention is applied may be anything that can be brazed using a fluoride flux and can be subjected to electrostatic powder coating. Typical materials include pure i-based alloys such as 1050, Al1-Mn alloys such as 3003, and 6061.
AJl-Mg-3i alloy such as 6063, 7003.
Examples include aluminum materials such as AA-7n-Mg alloys such as 7NO1, and specific products include condensers, evaporators, oil coolers, heater cores, radiators, and intercoolers.

In addition, the fluoride flux used in the method of the present invention includes one containing KiF, and 3AJ2F6 in KiF4 and 3AJ2F6.
Those containing K2/lF5 ・1120,
Others are obtained from aluminum chloride or potassium fluoride, or by adding small amounts of additives such as zinc fluoride, lithium fluoride, calcium fluoride, sodium fluoride, etc. to these 7 lacs. A fluoride having a composition preferably consisting of 40 to 50% by weight of potassium fluoride (KF) and 50 to 60% by weight of aluminum trifluoride (ApF3) and a small amount of unavoidable impurities in terms of single compounds. It is an aluminum potassium salt.

Electrostatic powder coating for applying fluoride flux to the surface of the object to be brazed by the method of the present invention is performed using an electrostatic powder coating system equipped with an electrostatic spray gun, a powder supply device, a high voltage generator, a control device, etc. Using an electric spray coating machine, a positive or negative charge is applied to the fluoride flux by corona discharge, and if necessary, a voltage with the opposite polarity to the charge of the fluoride flux is applied to the object to be brazed. , an electrostatic method in which a positively or negatively charged fluoride flux is sprayed onto the object to be brazed using the electrostatic spray gun, and the fluoride flux is attached to the surface of the object by electrical adsorption. Spraying method,
An electric charge is applied to the fluoride flux in a fluidized state in a fluidized tank, and the object to be brazed is grounded so as to be the opposite pole of the fluoride flux, and the charged fluoride is passed through the fluidized tank in this state. There is an electrostatic dynamic immersion method in which the flux is electrically attached to the surface of the object to be brazed, but the former electrostatic spraying method is preferable in order to automate the brazing line. These electrostatic powder coatings use electrical adsorption to deposit fluoride flux on the surface of the object to be brazed, so there is no need to use water, and there is no need to use water. must be carried out in a non-aqueous atmosphere without moisture.

In addition, if fluoride flux is applied to the surface of the object to be brazed using electrostatic powder coating, the fluoride flux will be uniformly distributed over the object to be brazed, and the object to be brazed will be able to assemble the tube and fin. Fluoride-based flux can be reliably applied to the joints of heat exchangers such as condensers and evaporators, so it is necessary to apply these in advance to the objects to be brazed to each other. It is best to apply fluoride flux after temporary assembly.

For the heating process of joining the objects to be brazed together and heating and brazing after applying the fluoride flux, a conventionally known method can be adopted as is.
Moreover, as for the brazing conditions at that time, the brazing conditions for a conventionally known heating process can be applied as they are.

Next, an application example of applying a fluoride flux to an object to be brazed by the method of the present invention will be explained based on the accompanying drawings.

In FIG. 1, a coating booth 3 is provided at an appropriate position on a conductive net conveyor 2 that conveys an object 1 to be brazed, and the ceiling of this coating booth 3 is coated with electrostatic powder spraying f.
! A4 electrostatic spray gun 5 is set, and when the object 1 to be brazed conveyed by the net conveyor 2 comes to a predetermined position in the coating booth 3, the electrostatic spray gun 5 applies an electric charge to the film. A chemical flux 6 is sprayed onto the object 1 to be brazed.

The electrostatic powder spray coating equipment I4 is equipped with an electrostatic spray gun 5, a powder supply device 7, a high voltage generator 8, and a control m+ device 9. The fluoride flux 6 is supplied in fixed quantities into the electrostatic spray gun 5, and the high voltage generated by the high voltage generator 8 is supplied to the electrostatic spray gun 5 to cause corona discharge. A positive or negative charge is given to the flux 6, and the positively or negatively charged fluoride flux 6 is electrostatically sprayed by compressed air supplied via the compressor 10, air dryer 11, mist separator 12, and control device 9. Spray from gun 5.

In addition, the net conveyor 2 is equipped with a fluoride flux 6.
A voltage is applied so that the polarity is opposite to the polarity of the charge given by the corona discharge, and the object 1 placed on the net conveyor 2 also has the polarity of the charge of the fluoride flux 6. are of opposite polarity, so that the fluoride flux 6 ejected from the electrostatic spray gun 5 reliably adheres to and coats the surface of the object 1 to be brazed.

Further, the coating booth 3 is provided with a duct 14 extending from the lower end thereof to a recovery device 13 for the fluoride flux 6, so that the fluoride flux that did not adhere to the surface of the object 1 to be brazed in the coating booth is removed. 6 is sucked by the fan 15 provided in the collection device 13, enters the collection device 13 through the duct 14, is collected from the collection port 16 provided at the lower end of this collection device 13, and is used as an electrostatic powder blower if necessary. The powder is circulated to the powder supply device 7 of the coating machine 4.

Regarding the electrostatic spray gun 5 that sprays the fluoride flux 6, it is not only necessary to install only one gun on the ceiling of the painting booth 3, but also to install it depending on the shape, size, or thickness of the object 1 to be brazed. Of course, an appropriate number may be used, such as attaching them to the left and right side walls of the painting booth 3, or attaching a total of three to the ceiling and each side wall.

[Function] In the method of the present invention, the fluoride flux is applied to the object to be brazed by electrostatic powder coating in a non-aqueous atmosphere, so there is no need for drying after the fluoride flux application step. In addition, it is possible to easily maintain the dew point of -40°C required in the heating process for the next brazing process, and the fluoride flux is attached to the surface of the object to be brazed by electrical adsorption. The fluoride flux can be applied uniformly, and even if the object to be brazed has a complicated shape, the fluoride flux can be reliably applied to every corner of the object, thereby significantly improving the brazing properties of the product.

[Example 1] Hereinafter, an example performed based on the application example shown in FIG. 1 will be described.

The object to be brazed 1 has a width of 26sX as shown in Fig. 2.
A flat tube 1a (AA1050 aluminum extruded tube) with a thickness of 5m++ and a corrugated fin 1b (core material:
As shown in Fig. 3, the size 3007111+1X 40 is obtained by temporarily assembling AA3003 and a skin material (aluminum plating sheet clad with AA4045) as shown in Fig. 3.
A heat exchanger of 0 mm x 26 m was used, and potassium tetrafluoroaluminate (
A mixture of KAflF4) and hekylyfluoroalumine (apparent specific gravity: 0.8'J/r:m3,
Particle size: 40 μm or less) using an electrostatic powder spray coating machine (manufactured by Nippon Paru Ising: S ＾ JET JRN
403) at a powder flow rate of 50 to 100 g/m
in. Electrostatic powder spray coating was performed under the conditions of 40 KV and 40 KV of voltage.

At this time, the amount of 7 lux deposited was approximately 109/unit (2 to 3 g/yt in terms of surface area), and it was almost uniformly deposited on the joints between the heat exchanger fins and flat tubes. .

The heat exchanger to which the flux has been attached in this way is then immediately introduced into a brazing furnace without going through a drying process, under normal brazing conditions, that is, under a nitrogen gas atmosphere with an oxygen partial pressure of 1, OOOppIII. Below and dew point -40℃
Brazing was performed by heating to 600° C. while maintaining the temperature at 600°C.

Generally, the required bonding ratio between fins and flat tubes is 95
% or more, but the heat exchanger of the product obtained in this example has a temperature of 99% or more between the fins and the flat duplex.
% or more was obtained, a fillet shape equivalent to that of the conventional product was obtained, and brazing with sufficient strength was performed. Further, during this heating step, the dew point was measured using a dew point meter, and it was easy to maintain the dew point at -40°C or lower.

[Effects of the Invention] According to the method of the present invention, the drying step after flux application, which was conventionally required in the brazing process, can be omitted, and the dew point condition of -40°C required in the heating process for the next brazing can be omitted. can be easily maintained, and the fluoride flux can be uniformly adhered to the surface of the object to be brazed by electrical adsorption, so the brazing properties of the product are significantly improved. In general, the fluoride flux is attached to the surface of the object to be brazed by electrical adsorption, so even if the object to be brazed has a complex shape, the fluoride flux can be applied to every corner of the object without fail. This also improves the brazing properties of the product.

In addition, since water is not used in the flux application process, it is easier to manage the flux after it has been applied, and there is no need for a drying process, resulting in energy savings.Moreover, the current automated line can be used as is, which is an advantage.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of the flux coating process in the method of the present invention, Fig. 2 is a partial perspective view of a flat tube constituting a heat exchanger for the object to be brazed used in the example, and Fig. 3 is a FIG. 3 is a front view showing a heat exchanger to be brazed, which is formed of the flat tube and corrugated fins of FIG. 2;

Claims (4)

[Claims] (1) Fluoride-based flux is applied to the objects to be brazed to each other, and when these objects are joined together and heated and brazed, the fluoride-based flux is applied with electrostatic charge in a non-aqueous atmosphere. A brazing method characterized by applying powder coating to the object to be brazed. (2) The brazing method according to claim 1, wherein the electrostatic powder coating is an electrostatic spraying method in which a charged fluoride flux is sprayed onto the object to be brazed. (3) The brazing method according to claim 1 or 2, wherein the fluoride flux is potassium aluminum fluoride salt. (4) The brazing method according to any one of claims 1 to 3, wherein the objects to be brazed are temporarily assembled to each other before the fluoride flux is applied.