BRAZING FURNACE AND ALUMINUM MATERIAL BRAZING PROCESS

Abstract

A brazing furnace (1) used in brazing an article to be processed (100) composed of an aluminum material, comprising: a soldering chamber (2) equipped with a heating device (21) which heats the object (100) to be processed to a soldering temperature; an inert gas supply device (3) which supplies an inert gas into the soldering chamber (2); and a dehumidification device (4) arranged between the inert gas supply device (3) and the soldering chamber (2) and carrying out dehumidification of the inert gas, wherein the dehumidifying device (4) is designed to remove the moisture in the inert gas atmosphere during dehumidification such that the dew point of the inert gas is -80 °C or less.

Description

TECHNICAL FIELD

[0001] The present invention relates to a brazing furnace and an aluminum material brazing method for brazing an aluminum material. STATE OF THE ART

[0002] For example, aluminum products such as heat exchangers and machine parts are composed of a number of components made of aluminum material (including aluminum and aluminum alloys; the same shall apply hereinafter). The CAB (Controlled Atmosphere Brazing) process, in which brazing is performed by applying a fluoride-based flux to a workpiece and then heating the workpiece in an inert gas atmosphere, is commonly used as a brazing process for aluminum products.

[0003] However, in the CAB process, a flux and / or flux residue adheres to the surface of aluminum after the completion of brazing. The flux and / or flux residue may cause problems depending on the use of the aluminum products. For example, in an aluminum heat exchanger on which electronic components are mounted, there is a risk of problems occurring during its manufacture, such as deterioration of surface treatment ability due to flux residue. Furthermore, in a water-cooled heat exchanger, for example, there is a risk of problems occurring such as clogging of a refrigerant flow path due to flux or the like. In addition, to remove a flux and flux residue, it is necessary to perform pickling treatment; in recent years, the cost burden of this treatment has been considered a problem.

[0004] Accordingly, in order to reduce or avoid these problems associated with the use of a flux, the use of soldering methods with a reduced amount of flux applied to a joining part and so-called fluxless soldering methods in which soldering is carried out without applying a flux to the surface of a joining part in an inert gas atmosphere (e.g., JP H10 - 180 489 A) have been investigated. However, in these soldering methods, it is known from experience that the soldering performance tends to deteriorate when the humidity in the atmosphere is relatively high. Deterioration of the soldering performance also occurs when nitrogen gas with a high purity, which is obtained by evaporating liquid nitrogen, is supplied to the soldering furnace.Therefore, it was assumed that the deterioration of solderability was caused by an increase in moisture introduced into the furnace from outside, together with an increase in humidity in the atmosphere.

[0005] The moisture introduced into the furnace is of various types, such as outside air inevitably introduced when the object to be processed and the fixture, etc., are placed in the furnace for fixing, moisture absorbed in the object to be processed, or the like. To reduce the moisture introduced into the furnace from the outside in this way, a brazing method has been proposed (JP 2016 - 083 699 A) in which the object to be processed is preheated in a reduced-pressure atmosphere and brazed after the moisture evaporated from the object to be processed.

[0006] In addition, techniques have also been proposed which reduce the oxygen concentration in the brazing furnace by a method (JP 2007 - 319 924 A) in which at least a part of the inner wall of a brazing furnace is formed of a carbon-containing material and oxygen in the furnace is reacted with the carbon-containing material so that the oxygen is converted into carbon dioxide, by a method (JP 2014 - 217 844 A) in which an inert gas is supplied to an oxygen pump equipped with a solid electrolyte body having oxygen ion conductivity and a voltage is applied to this solid electrolyte, etc.

[0007] WO 01 / 88451 A1 discloses another soldering furnace. DE 10 2011 000 122 A1 discloses a device for welding copper. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] In practice, however, when soldering is performed with a reduced applied amount of a flux or without applying a flux, the solderability deteriorates in some cases even if the moisture introduced from the outside and / or the oxygen concentration in the soldering atmosphere is or are reduced by the techniques of Patent Documents 2 to 4.

[0009] The present invention has been made in view of this background, and it is an object of the present invention to provide a soldering furnace and a soldering method in which the solder joint quality can be easily stabilized in soldering with a reduced applied amount of a flux or in soldering without the use of a flux. MEANS TO SOLVE THE PROBLEMS

[0010] One aspect of the present invention is a brazing furnace according to claim 1.

[0011] Another aspect of the present invention is a method for brazing an aluminum material according to claim 9.

[0012] In conventional soldering, nitrogen gas generated by evaporating liquid nitrogen was used as the inert gas, as described above. Since such nitrogen gas already has sufficient purity, it has been recognized that the deterioration of solderability is primarily caused by oxygen and moisture entering from outside the furnace, such as the atmosphere entering from outside the furnace, moisture absorbed into the object being processed, or the like.

[0013] However, nitrogen gas produced by evaporating liquid nitrogen typically has a dew point of about -76°C and contains a small amount of moisture of about 1 ppm by volume. As a result of intensive investigation, the present inventors found that the deterioration of solderability is caused by adding the trace amount of moisture intrinsically contained in the nitrogen gas to the moisture introduced from outside the furnace.

[0014] The above-mentioned soldering furnace includes the dehumidification device that performs dehumidification of the inert gas supplied from the inert gas supply device and is configured so that the dehumidified inert gas can be supplied into the soldering chamber. Accordingly, the inert gas is not supplied directly from the inert gas supply device to the soldering chamber, but rather is supplied to the soldering chamber after dehumidification has been performed, so that it is possible to reduce the total amount of moisture introduced into the soldering chamber from the outside and the moisture intrinsically contained in the inert gas more than in the past. In this way, the deterioration of the solderability can be limited, and a satisfactory solder joint can be obtained when soldering with a reduced applied amount of flux or when soldering without the use of a flux.

[0015] Furthermore, according to the above-mentioned brazing furnace, it is possible to mitigate the effects on the brazing performance due to the atmosphere outside the brazing furnace, the storage environment of the object to be processed, etc. Therefore, by using the brazing furnace, it is possible to reduce the amount of moisture introduced into the brazing furnace, thereby forming a satisfactory brazed joint, for example, even in areas or seasons with high temperatures and high humidity, or in cases where strict control of the storage environment of the material to be processed is difficult. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view showing a main part of a soldering furnace according to Working Example 1. Fig. 2 is a sectional view showing a main part of a brazing furnace according to Working Example 2, further including a preheating chamber. Fig.3 is a sectional view showing a main part of a brazing furnace according to Working Example 3, further including a cooling chamber. Fig. 4 is a perspective view of an outer fin test piece for evaluating solderability according to Experimental Example 1. Fig. 5 is a perspective view of a cup test specimen for evaluating solderability according to Experimental Example 2. Fig. 6 is a sectional view along the arrows VI - VI in the Fig. 5. MODE OR MODES FOR CARRYING OUT THE INVENTION

[0016] In the soldering furnace, as long as an inert gas can be supplied to the soldering chamber by means of a dehumidifying device, any type of device can be used as the inert gas supply device. For example, a device that supplies an inert gas formed by evaporating liquid nitrogen, or the like, a device that supplies an inert gas from a cylinder filled with the inert gas, or the like can be used as the inert gas supply device. Further, in the case where nitrogen is used as the inert gas, a device that separates nitrogen in the atmosphere using a cryogenic separation method and supplies the nitrogen gas generated in situ can be used as the inert gas supply device.

[0017] A non-oxidizing gas such as nitrogen gas, helium gas, argon gas, or the like can be used as the inert gas supplied by the inert gas supply device. In a mass production facility, high-purity nitrogen gas formed by the evaporation of liquid nitrogen is typically used due to cost and availability. Since such nitrogen gas has a sufficiently low dew point of approximately -76°C, the number of dehumidification instances can be reduced and the dehumidification device can be simplified.

[0018] The inert gas is supplied from the inert gas supply device to the dehumidification device. Dehumidification of the inert gas is then performed in the dehumidification device. The dehumidification device can be suitably selected for use from known dehumidification devices, taking into account the dew point of the inert gas and the dehumidification capacity of the device.For example, a device that removes moisture condensed by isothermally compressing the inert gas by a compressor, thereby increasing the relative humidity, a device that selectively removes moisture vapor by contacting the inert gas compressed by a compressor with a vapor-permeable membrane, a device in which moisture is absorbed into a moisture absorbent by contacting the inert gas with the moisture absorbent, or the like can be used as a dehumidifying device. These dehumidifying devices can be used individually or in combination.

[0019] The dehumidification device is preferably configured so that the dew point of the inert gas can be adjusted to -80°C or lower. By adjusting the dew point of the inert gas to such an extremely low temperature, the effect of moisture introduced from the outside can be reduced. Consequently, deterioration of the solderability can be more effectively limited during soldering with a reduced amount of flux applied or during soldering without the use of flux.

[0020] The dehumidifying device preferably comprises a moisture absorbent that absorbs moisture in the inert gas by bringing it into contact with the inert gas. This type of dehumidifying device has an extremely high dehumidifying capacity, so that the dew point of a high-purity inert gas, such as nitrogen gas formed by evaporating liquid nitrogen, can be further reduced. Therefore, by using a dehumidifying device equipped with a moisture absorbent, deterioration of solderability can be more effectively limited.

[0021] For example, an adsorption column loaded with a desiccant such as silica gel, a metal silicate, or a zeolite, a rotor holding such a desiccant, or the like can be used as the moisture absorption medium. In the former case, dehumidification can be performed by passing the inert gas through the adsorption column. In the latter case, dehumidification can be performed by bringing the inert gas into contact with the rotating rotor.

[0022] The dehumidification device may further comprise a plurality of gas flow paths connected in parallel, a moisture absorbent disposed in each gas flow path, and a flow path switching device that switches the supply and supply interruption of the inert gas to each gas flow path. The dehumidification performance of a moisture absorbent may deteriorate for various reasons, such as the moisture absorbent becoming nearly saturated with absorbed moisture. In such a case, a dehumidification device equipped with a flow path switching device can stop the supply of the inert gas to that moisture absorbent and continuously supply the inert gas to another moisture absorbent. In this way, replacement, etc., can be achieved.The moisture absorbent, whose dehumidification capacity has decreased, can be removed while continuing to dehumidify the inert gas. Consequently, the maintainability of the brazing furnace can be further improved.

[0023] Furthermore, the dehumidification device preferably further comprises a regeneration device that removes moisture absorbed in a moisture absorbent from the moisture absorbent. By removing the moisture from the moisture absorbent using the regeneration device, the dehumidification capacity of the moisture absorbent can be restored. The frequency of replacing the moisture absorbent can thereby be reduced, and consequently, the operating costs of the brazing furnace can be reduced.For example, a device that desorbs moisture in the moisture absorbent by degassing while heating the moisture absorbent, a device that desorbs moisture in the moisture absorbent by supplying dry gas to the moisture absorbent, a device that desorbs moisture in the moisture absorbent by simultaneously performing heating of the moisture absorbent and introducing dry gas, or the like may be used as the regeneration device.

[0024] The soldering furnace may be equipped with only a soldering chamber, or it may further comprise a chamber communicating with the soldering chamber. For example, the soldering furnace may further comprise a preheating chamber connected to the soldering chamber and equipped with a preheating device that heats the object to be processed to a temperature lower than the soldering temperature; a preheating pump that reduces the pressure inside the preheating chamber; and a repressurization gas supply device that supplies the inert gas to repressurize the interior of the preheating chamber after the pressure reduction.

[0025] In this case, in the state where the object to be processed has entered the preheating chamber, the soldering furnace can reduce the pressure inside and preheat the object to be processed. Furthermore, by preheating the object to be processed in a reduced-pressure atmosphere, evaporation of moisture adhering to the object to be processed and the device can be promoted. As a result, the amount of moisture introduced into the soldering chamber can be reduced more than in the case where preheating is not performed.

[0026] Furthermore, with respect to the soldering furnace, after preheating is performed, an inert gas can be supplied into the preheating chamber, and the preheating chamber can be repressurized. Consequently, exposure of the object to be processed and the device to the atmosphere after preheating can be avoided; as a result, re-adhesion of moisture thereto can be prevented. Furthermore, by repressurizing the preheating chamber using the inert gas, the atmosphere can be prevented from flowing into the soldering chamber when the object to be processed is moved from the preheating chamber to the soldering chamber.

[0027] As mentioned above, the brazing furnace further equipped with the preheating chamber can further reduce the amounts of oxygen and moisture introduced from outside the furnace. Therefore, by using the brazing furnace for brazing with a reduced amount of flux applied or for brazing without the use of flux, the effects on the brazing performance due to the storage environment and usage conditions of the object to be processed, the fixture, and the filler material, as well as fluctuations in the environment outside the furnace, and the like, can be reduced. As a result, the brazing furnace can easily stabilize the brazing joint quality and can limit the deterioration of the brazing performance, the occurrence of joint failure, and the like.

[0028] The brazing furnace is preferably designed so that the pressure within the preheating chamber can be reduced to 100 Pa or less. By setting the pressure within the preheating chamber to 100 Pa or less, the removal of moisture and the like during preheating can be further promoted. As a result, the time required for preheating can be further shortened.

[0029] The preheating chamber is preferably configured so that the temperature of the object to be processed can be set to more than 200°C. In this case, the evaporation of moisture adhering to the object to be processed or the like can be promoted, and the amount of moisture introduced into the furnace can be further reduced. Furthermore, in cases where a cutting oil or the like adheres to the object to be processed and / or the device, the removal of these residues can also be promoted.

[0030] Furthermore, the soldering furnace may further comprise a cooling chamber connected to the soldering chamber and a cooling gas supply device that supplies an inert gas into the cooling chamber. By cooling the object to be processed in the inert gas atmosphere in the cooling chamber, unnecessary oxidation of the object to be processed can be limited. Moreover, in this case, since the cooling chamber is filled with an inert gas, it is possible to prevent the atmosphere from flowing into the soldering chamber from the cooling chamber.

[0031] According to the brazing furnace as mentioned above, the object to be processed composed of an aluminum material can be brazed in the following manner.

[0032] In particular, soldering can be carried out by: Dehumidification of an inert gas; By supplying the dehumidified inert gas, causing the environment of the object to be processed to be an inert gas atmosphere; and Heating the object to be processed to the soldering temperature in the inert gas atmosphere and soldering the object.

[0033] Brazing can be performed using a workpiece that has been pre-coated with a fluoride-based flux on a portion to be brazed, or it can be performed using a workpiece that has not been pre-coated with a fluoride-based flux on a portion to be brazed. In the former case, the applied amount of the fluoride-based flux can be limited to 2 g / m 2or less. According to the brazing method mentioned above, satisfactory brazing can be performed in either case of brazing with a reduced amount of flux applied or brazing without the use of flux. (Working example 1)

[0034] A working example of the brazing furnace will be explained with reference to the drawings. The brazing furnace 1 of the present example is designed for use in brazing a processing object 100 composed of an aluminum material. As shown in FIG. Fig.1, the soldering furnace 1 comprises a soldering chamber 2 equipped with heating devices 21 that heat the object 100 to be processed to a soldering temperature, an inert gas supply device 3 that supplies an inert gas into the soldering chamber 2, and a dehumidifying device 4 that is arranged between the inert gas supply device 3 and the soldering chamber 2 and dehumidifies the inert gas.

[0035] The soldering furnace 1 of the present example is configured so that the object to be processed 100 can be placed inside the furnace and removed from the furnace through an entrance / exit provided in the soldering chamber 2. The entrance / exit of the soldering chamber 2 is equipped with a front door 11 that can be opened and closed. The inert gas supply device 3 and the dehumidification device 4 are arranged outside the soldering furnace 1. The inert gas supply device 3 is connected to the dehumidification device 4 via a gas line 31, and the dehumidification device 4 is connected to the soldering chamber 2 via a gas line 41.

[0036] The soldering chamber 2 of the present example includes the heaters 21, a graphite muffle 22 disposed inside the heaters 21, and a belt-type endless drive conveyor 23 that conveys the workpiece 100. When the front door 11 is closed, the conveyor 23 is entirely housed inside the soldering chamber 2 and is separated from a conveyor (not shown) provided outside the soldering chamber 2. Consequently, moisture, oil, and the like adhering to the conveyor provided outside the soldering chamber 2 can be prevented from entering the furnace. The dimensions of the soaking area of the soldering chamber 2 are: a length of 300 mm, a width of 200 mm, and a height of 200 mm.

[0037] The inert gas supply device 3 of the present example is designed to generate nitrogen gas by evaporating liquid nitrogen. The dew point of the nitrogen gas generated by the inert gas supply device 3 is typically from -74°C to -78°C, and the oxygen concentration is typically from 0.1 ppm to 0.5 ppm. The nitrogen gas generated by the inert gas supply device 3 is supplied to the dehumidification device 4 through the gas line 31.

[0038] The dehumidification device 4 of the present example is connected to the gas line 31 and includes a flow path switching device 42, two gas flow paths 43 connected in parallel with the flow path switching device 42, moisture absorbers 44 disposed in each of the gas flow paths 43, and a regeneration device 45. The flow path switching device 42 can switch the supply and supply cutoff of the inert gas to each gas flow path. The moisture absorbers 44 contact the nitrogen gas and can absorb moisture in the nitrogen gas. The regeneration device 45 can remove the moisture absorbed in the moisture absorbers 44 from the moisture absorbers 44.

[0039] The flow path switching device 42 of the present example includes a branching section 421 for distributing nitrogen gas supplied from the inert gas supply device 3 to each gas flow path 43, and switching valves 422 provided between the branching section 421 and each moisture absorber 44. The switching valves 422 can switch the supply and supply cutoff of nitrogen gas to the moisture absorbers 44 by switching them open and closed, respectively. Furthermore, each switching valve 422 can adjust the flow rate of nitrogen gas into each moisture absorber 44 by adjusting its opening degree.

[0040] The two gas flow paths 43 are connected to each other in parallel by the branching section 421. Each gas flow path 43 has the moisture absorber 44 disposed therein. The moisture absorbers 44 of the present example are specific adsorption columns filled with a zeolite. The dew point of the nitrogen gas that has passed through the moisture absorbers 44 is -80°C or less.

[0041] The regeneration device 45 of the present example includes heaters 451 that heat each moisture absorbent 44 and a regeneration pump 452 that degasses the moisture absorbent 44. The regeneration pump 452 is connected to the gas flow paths 43 through three-way valves 453 provided at each inlet and outlet of each moisture absorbent 44. Furthermore, a shutoff valve 454 is provided between the regeneration pump 452 and the three-way valves 453 to shut off the regeneration pump 452 from the three-way valves 453. It should be noted that, although the heaters 451 have been used for heating the moisture absorbers 44 in the present example, the moisture absorbers 44 may be heated by other heating devices such as a microwave heating device or the like instead of the heater 451.

[0042] When regenerating a moisture absorbent 44, first, the switching valve 422 connected to this moisture absorbent 44 is closed, and a closed flow path is formed including the moisture absorbent 44, two of the three-way valves 453, and the regeneration pump 452. Then, the moisture absorbent 44 is degassed by the regeneration pump 452 while being heated by the heater 451. Moisture absorbed in the heated moisture absorbent 44 is desorbed therefrom. The moisture absorbent 44 is regenerated by removing this moisture using the regeneration pump 452, and the dehumidification capacity can be restored.

[0043] The nitrogen gas, which has passed through a moisture absorbent 44 and has a dew point of -80°C or less, is supplied to the soldering chamber 2 via the gas line 41. The dew point of the nitrogen gas is typically from -80°C to -84°C, and the oxygen concentration is typically from 0.1 ppm to 0.5 ppm.

[0044] The soldering furnace 1 of the present example is designed so that the dehumidified nitrogen gas of the soldering chamber 2 is continuously supplied with 5 m 3 / hour to replace the interior of the soldering chamber 2 with the nitrogen gas. After the soldering chamber 2 is filled with the nitrogen gas, excess nitrogen gas is discharged from a gas escape port (not shown) provided near the front door 11.

[0045] Next, the operation and effects of the soldering furnace 1 of the present example will be described. The soldering furnace 1 includes the dehumidification device 4, which dehumidifies the nitrogen gas supplied from the inert gas supply device 3, and is configured to supply the dehumidified nitrogen gas into the soldering chamber 2. In this way, the nitrogen gas generated by the inert gas supply device 3 is not directly supplied into the soldering chamber 2, but rather is supplied into the soldering chamber 2 after dehumidification, so that the total amount of moisture introduced into the soldering chamber 2 from the outside and the moisture originally contained in the nitrogen gas can be reduced more than in the past.Consequently, deterioration of solderability when soldering with a reduced amount of flux applied or when soldering without the use of flux can be limited and satisfactory solder joints can be formed.

[0046] Furthermore, according to the soldering furnace 1, the effects on the solderability due to the atmosphere outside the soldering furnace 1, the storage environment of the object 100 to be processed, and the like can be mitigated. Therefore, by using the soldering furnace 1, the amount of moisture introduced into the soldering chamber 2 can be reduced, thereby forming a satisfactory solder joint, for example, even in areas or seasons with high temperatures and high humidity, or even in cases where strict control of the storage environment of the object 100 to be processed is difficult.

[0047] Furthermore, the inert gas supply device 3 is configured to generate high-purity nitrogen gas by evaporating liquid nitrogen. Accordingly, the number of dehumidification instances can be reduced and the dehumidification device 4 can be simplified.

[0048] The dehumidification device 4 includes the moisture absorbers 44, which contact the nitrogen gas and absorb moisture in the nitrogen gas. Accordingly, the dew point of the high-purity nitrogen gas generated by the inert gas supply device 3 can be further reduced, easily achieving an extremely low dew point of -80°C or less. Consequently, the deterioration of solderability can be more effectively limited with a reduced amount of flux applied or during soldering without applying flux.

[0049] The dehumidification device 4 further includes the two gas flow paths 43 connected in parallel, the moisture absorbers 44 respectively arranged in the gas flow paths 43, and the flow path switching device 42 that switches the supply and supply interruption of nitrogen gas to each gas flow path 43. Consequently, when the dehumidification capacity of one of the moisture absorbers 44 decreases, the supply of nitrogen gas to that moisture absorber 44 can be stopped, and the nitrogen gas can be continuously supplied to the other moisture absorber 44. This allows the moisture absorber 44 whose dehumidification capacity has decreased to be replaced or regenerated while continuing to dehumidify the nitrogen gas. As a result, the maintainability of the brazing furnace 1 can be further improved.

[0050] The dehumidification device 4 further includes the regeneration device 45, which removes moisture absorbed in the moisture absorbers 44 from the moisture absorbers 44. This can reduce the frequency of replacing the moisture absorbers 44 and lower the operating costs of the soldering furnace 1. (Working example 2)

[0051] The present example is an example of a two-chamber soldering furnace 102 equipped with the soldering chamber 2 and a preheating chamber 5 connected to the soldering chamber 2. It should be noted that, of the symbols used in the present example and thereafter, symbols identical to symbols used in the preceding examples indicate structural elements and the like identical to those in the preceding example, unless otherwise explained.

[0052] In the Fig. 2, the soldering furnace 102 of the present example includes the soldering chamber 2, the preheating chamber 5 connected to the soldering chamber 2 and equipped with the preheating devices 51 that preheat the object 100 to be processed to a temperature lower than the soldering temperature, a preheating pump 52 that reduces the pressure inside the preheating chamber 5, and a repressurizing gas supply device 53 that supplies an inert gas for repressurizing the interior of the preheating chamber 5 after the pressure reduction.

[0053] The soldering furnace 102 is configured so that the workpiece 100 to be processed can be placed inside and removed from the furnace through the entrance / exit provided in the preheating chamber 5. The front door 11, which can be opened and closed, is located at the entrance / exit of the preheating chamber 5. Furthermore, the preheating chamber 5 is connected to the soldering chamber 2, and an intermediate door 12, which can be opened and closed, is provided between the preheating chamber 5 and the soldering chamber 2.

[0054] The preheating pump 52 is located outside the brazing furnace 102 and is connected to the preheating chamber 5 via a drain line 521. A drain valve 522, which acts as a barrier between the preheating pump 52 and the preheating chamber 5, is provided in the drain line 521. It should be noted that the preheating pump 52 is an oil-sealed rotary pump with a mechanical booster pump.

[0055] In the present example, the inert gas supply device 3 is also used as a repressurization gas supply device 53. Specifically, the inert gas supply device 3 is also connected to the preheating chamber 5 via a pressure recovery gas line 531. Thus, nitrogen gas formed by evaporating liquid nitrogen is supplied to the preheating chamber 5. Furthermore, a pressure recovery valve 532, which acts as a barrier between the inert gas supply device 3 and the preheating chamber 5, is provided in the pressure recovery gas line 531.

[0056] The inert gas supply device 3 is designed so that the nitrogen gas of the preheating chamber 5 with 5 m 3 / hour can be continuously supplied. It should be noted that excess nitrogen gas supplied into the preheating chamber 5 is discharged from a gas exhaust port (not shown) provided near the front door 11.

[0057] The preheating chamber 5 includes the preheating devices 51, stainless steel muffles 54 arranged within the preheating devices 51, and a belt-type endless drive conveyor 55 that transports the object 100 to be processed. The dimensions of the soaking area of the preheating chamber 5 are: a length of 300 mm, a width of 200 mm, and a height of 200 mm.

[0058] The preheating chamber 5 is configured such that by operating the preheating vacuum pump 52 with the front door 11 and the intermediate door 12 closed, the pressure in the chamber can be adjusted to 0.4 Pa or less. It should be noted that the pressure inside the chamber can be measured by a Pirani gauge (not shown). Other aspects are the same as in Working Example 1. It should be noted that the dehumidifying device 4 of the present example includes the regeneration pump 452, the three-way valves 453, and the shut-off valve 454, but for the sake of simplicity, these are omitted in the Fig. 2 are not described.

[0059] The brazing furnace 102 of the present example can be used, for example, as described below. First, the front door 11 is opened, and the workpiece 100 made of an aluminum material is placed in the preheating chamber 5. Then, the front door 11 and the intermediate door 12 are closed. In this state, the preheating pump 52 is operated to discharge the interior of the preheating chamber 5, and the preheaters 51 are simultaneously operated to preheat the workpiece 100 (100a) to be processed. The timing at which discharge begins and the timing at which preheating of the workpiece 100 to be processed may be simultaneous, or one may start earlier than the other.In order to avoid unnecessary oxidation of the article 100 to be processed, it is preferable to start discharging before starting preheating.

[0060] The temperature reached during preheating can be set, for example, to 200°C or higher. Preheating is completed when the pressure inside the preheating chamber 5 reaches 100 Pa or less and the temperature of the object 100 to be processed reaches the target temperature. After preheating is completed, the relief valve 522 is closed; then, the preheating pump 52 and the preheaters 51 are stopped. After that, the pressure recovery valve 532 is opened, and the pressure inside the preheating chamber 5 is restored using nitrogen gas until it reaches atmospheric pressure. This makes the environment of the object 100a to be processed an inert gas atmosphere.

[0061] After the pressure recovery is completed, the pressure recovery valve 532 is closed, and then the intermediate door 12 is opened. Thereafter, the object 100 to be processed is transported into the soldering chamber 2, and the intermediate door 12 is closed. Since dehumidified nitrogen gas is continuously supplied into the interior of the soldering chamber 2, an inert gas atmosphere surrounding the object 100 to be processed is maintained during the transportation of the object 100 to be processed.

[0062] Next, the workpiece 100 (100b) to be processed, which is arranged inside the brazing chamber 2, is heated by the heaters 21, and then brazing is performed. After brazing is completed, the intermediate door 12 is opened, and the workpiece 100 is transferred to the preheating chamber 5. Since a nitrogen gas atmosphere is maintained inside the preheating chamber 5, the workpiece 100 for which brazing is completed can be cooled in the nitrogen gas atmosphere. After cooling, the front door 11 is opened, and the workpiece 100 is removed from the furnace. Brazing of the workpiece 100 can be performed by the above.

[0063] The brazing furnace 102 of the present example is configured so that preheating can be performed in a reduced-pressure atmosphere, pressure recovery can be performed by supplying nitrogen gas, and brazing can be performed in a dehumidified nitrogen gas atmosphere. Therefore, when brazing is performed with a reduced applied amount of flux or when brazing is performed without the use of flux, the effects on the brazing performance due to the storage environment and usage conditions of the object 100 to be processed, the jig and filler material, fluctuations in the environment outside the furnace, and the like can be reduced. As a result, the deterioration of the brazing performance can be more effectively restrained, thereby stably forming satisfactory brazed joints.

[0064] Furthermore, regarding the soldering furnace 102, since the effects on the solderability due to the storage environment of the object 100 to be processed or the like can be reduced, the soldering furnace 1 can be used appropriately even in areas, seasons with high temperatures and high humidity, and the like. Furthermore, the soldering furnace 102 can provide satisfactory solder joints even in working environments where strict control of the storage environment or the like of the object 100 to be processed and the device is difficult. Regarding the rest, the soldering furnace 102 of the present example can provide the same operations and effects as in Working Example 1. (Working example 3)

[0065] The present example is an example of a three-chamber type 103 soldering furnace, which is equipped with the preheating chamber 5, the soldering chamber 2 and a cooling chamber 6. As shown in the Fig.As shown in Fig. 3, with respect to the soldering furnace 103 of the present example, the preheating chamber 5, the soldering chamber 2, and the cooling chamber 6 are arranged in this order. In the preheating chamber 5, an entrance is provided for placing the object 100 to be processed inside the furnace. The front door 11, which can be opened and closed, is provided at the entrance. The intermediate door 12, which can be opened and closed, is provided between the preheating chamber 5 and the soldering chamber 2, and a rear door 13, which can be opened and closed, is provided between the soldering chamber 2 and the cooling chamber 6.

[0066] The cooling chamber 6 includes a belt-type endless drive conveyor 23 that transports the object 100 to be processed. An exit for removing the object 100 to the outside of the furnace is provided in the cooling chamber 6. An openable and closeable exit door 14 is provided at the exit to prevent the outside atmosphere from flowing into the brazing furnace 103. Note that a metal curtain or the like may be installed instead of the exit door 14.

[0067] Furthermore, a cooling gas supply device 62, located outside the furnace, is connected to the cooling chamber 6 via a cooling gas line 63. In the present example, the inert gas supply device 3 is also used as the cooling gas supply device 62. Specifically, the inert gas supply device 3 is also connected to the cooling chamber 6 via the cooling gas line 63. A cooling gas valve 64, which acts as a barrier between the inert gas supply device 3 and the cooling chamber 6, is provided in the cooling gas line 63.

[0068] The inert gas supply device 3 is designed so that nitrogen gas with 5 m 3 / hour can be continuously supplied into the cooling chamber 6. It should be noted that excess nitrogen gas is provided by means of a gas escape port (not shown) near the exit door 14.

[0069] The brazing furnace 103 of the present example is configured so that the object 100 to be processed can be placed in the furnace through an entrance provided in the preheating chamber 5. The object 100 to be processed (100a), located within the preheating chamber 5, is preheated and then transported into the brazing chamber 2. The object 100 to be processed (100b), for which brazing is completed in the brazing chamber 2, is transported to the cooling chamber 6. The object 100 to be processed (100c), which has been cooled in the nitrogen gas atmosphere in the cooling chamber 6, is taken out of the furnace from the exit of the cooling chamber 6. Other aspects are the same as in Working Example 2. It should be noted that the dehumidifying device 4 of the present example includes the regeneration pump 452, the three-way valves 453 and the shut-off valve 454 in the same manner as in Working Example 1, but these are in the Fig. 3 not described for reasons of simplicity.

[0070] Thus, the soldering furnace 103 further includes the cooling chamber 6 connected to the soldering furnace 103 and the cooling gas supply device 62 that supplies nitrogen gas into the cooling chamber 6. Regarding the soldering furnace 103, as mentioned above, unnecessary oxidation of the object 100 to be processed can be restricted by cooling the object 100 to be processed in a nitrogen gas atmosphere within the cooling chamber 6. Moreover, since the cooling chamber 6 is filled with nitrogen gas, the atmosphere can be prevented from flowing from the cooling chamber 6 into the soldering chamber 2. Regarding the rest, the soldering furnace 103 of the present example can provide the same operations and effects as in Working Example 2.

[0071] In the case where the brazing furnace 103 includes the cooling chamber 6 as in the present example, the cooling chamber 6 may further be configured so that the chamber interior can be discharged and the pressure within the chamber can be restored. In this case, by discharging the chamber interior of the cooling chamber 6 and then restoring the pressure using nitrogen gas, the atmosphere can be reliably prevented from flowing into the interior of the cooling chamber 6. As a configuration that can achieve such functions, a configuration in which, for example, the discharge line of the preheating pump is connected to the cooling chamber 6 in the same manner as that of the preheating chamber 5 is conceivable.

[0072] Further, in the present example, although the inert gas supply device 3 is also used as the pressure-restoring gas supply device 53 and the cooling gas supply device 62, gas supply devices may be provided separately as the pressure-restoring gas supply device 53 and the cooling gas supply device 62, respectively. (Experimental Example 1)

[0073] The present example is an example in which brazing is performed by variously changing the dew point of the inert gas to be supplied into the brazing chamber 2. In the present example, two types of aluminum materials (test materials A1 and A2) with the chemical components and layer structures shown in Table 1 were prepared. These test materials are single-sided brazing sheets with a thickness of 0.6 mm in which a filler material was bonded to a core surface by lamination.

[0074] In the present example, an outer fin test specimen 7 simulating a connection between outer fins and a refrigerant flow path was manufactured and brazed. The test specimen 7 of the present example, as shown in the Fig.4, comprises a corrugated rib 71 and two flat sheets 72 surrounding the corrugated rib 71. The corrugated rib 71 is made of a JIS A3003 alloy. The flat sheets 72 are made of the test materials, and the filler materials 721 of the flat sheets 72 are in contact with crest portions 711 of the corrugated rib 71. The length of the corrugated rib 71 is 50 mm. The length of each of the flat sheets 72 is 60 mm, the width is 25 mm, and the distance between the flat sheets is 10 mm.

[0075] The test pieces 7 were specifically assembled in the following manner. First, after cutting a sheet material made of an A3003 alloy to specified dimensions, it was corrugated to form the corrugated fin 71. Further, the test material was cut to the aforementioned dimensions separately from the production of the corrugated fin 71, thus producing the flat sheets 72. These components were then degreased with acetone.

[0076] Here, with respect to the flat sheets 72 using test material A1 (Table 2, Experiment No. 3), a fluoride-based flux was applied to the filler material 721 in the applied amount shown in Table 2. The applied amount of flux was calculated as follows. After measuring the mass (g) of the flat sheets 72 before applying the flux, the flux was applied to the flat sheets and then dried. The total amount of applied flux was calculated by subtracting the mass (g) of the flat sheets 72 measured before applying the flux from the mass (g) of the flat sheets 72 after drying the flux. The applied amount of flux (g / cm 2 ) was calculated by dividing the total amount (g) by the flux application area (cm 2 ), ie, the area of the filling material 721, is calculated.

[0077] Thereafter, the corrugated rib 71 and the flat sheet 72 were mounted in this order on the flat sheet 72, so that the test specimen 7 as shown in the Fig. 4. This test specimen 7 was held in the layer direction by a device not shown and thus fixed.

[0078] After fixing the test piece 7 to the fixture, preheating and soldering heating were carried out successively by means of the soldering furnace 102 used in Working Example 2 (see the Fig.2) was performed so that the test piece 7 was brazed. As shown in Table 2, in Experiment Nos. 1, 3, and 4, the test piece 7 was placed inside the preheating chamber 5, and preheating was performed in a nitrogen gas atmosphere at normal pressure under the condition of heating the test piece to 200°C. In Experiment No. 2, the test piece 7 was placed inside the preheating chamber 5, and preheating was performed in an atmosphere with a reduced pressure of 10 Pa under the condition of heating the test piece to 300°C.

[0079] After preheating under the above-mentioned conditions, the test piece 7 was transported into the soldering chamber 2, and soldering heating was performed by heating to 600°C at a temperature rise rate of about 13°C / min. Meanwhile, as shown in Table 2, in Experiment Nos. 1 and 2, dehumidified nitrogen gas, which had been dehumidified using the dehumidifying device 4 so that the dew point was -80°C or less, was supplied to the inside of the soldering furnace 1. In Experiment No. 3, after the dew point of the nitrogen gas generated by the inert gas supply device 3 was adjusted to -55°C, the nitrogen gas was supplied to the soldering chamber 2 without performing dehumidification. In Experiment No. 4, nitrogen gas generated by the inert gas supply device 3 was supplied to the soldering chamber 2 without performing dehumidification.The dew points of nitrogen gas before and after dehumidification and the dew point in the soldering chamber 2 at the time of soldering heating in each experiment were as shown in Table 2.

[0080] After the brazing was completed, the test specimen 7 was transported to the preheating chamber 5 and cooled to 450 °C in the preheating chamber 5. The test specimen 7 was then removed from the furnace.

[0081] After brazing, the corrugated rib 71 was removed from the test piece 7, and the joining percentage was calculated based on the traces of the ridges present on the flat sheets 72 in the following manner. First, for the trace of each ridge, the length in the width direction of the flat sheet 72 was measured, and the sum of the lengths was calculated. Separately from this calculation, on the assumption that the flat sheet 72 and the corrugated rib 71 were completely joined, the sum of the lengths of the ridges in the sheet width direction was calculated. Then, the ratio of the former value to the latter value was set as the joining percentage (%). It should be noted that the latter value can be obtained, for example, by multiplying the width of the corrugated rib 71 by the number of peaks 711 (cf. the Fig. 4), ie, the number of sections to be connected to the flat sheets 72 can be calculated.

[0082] In the "Evaluation Results" columns, symbol "A" is indicated when the joining percentage was 95% or more, symbol "B" is indicated when the joining percentage was 85% or more and less than 95%, symbol "C" is indicated when the joining percentage was 60% or more and less than 85%, and symbol "D" is indicated when the joining percentage was less than 60%. When evaluating the solderability using the outer rib test piece 7, in the case of symbols A and B where the joining percentage is 85% or more, the solderability was judged to be acceptable due to satisfactory solderability. In the case of symbols C and D where the joining percentage is less than 85%, the solderability was judged to be unacceptable due to the risk of solder failure. Table 1 Table 1 Test material symbol Layer structure Chemical composition (mass%) Lamination percentage (%) Total sheet thickness (mm) Notes Si Fe Cu Mn Mg Bi A1 Filling material 10 - - - - - 10 0,6 Flux soldering Nuclear material 0,27 0,6 0,15 1,2 - - - A2 Filling material 10 - - - - 0,02 10 0,6 Soldering without flux Nuclear material 0,35 - 0,27 - 0,6 - - Table 2 Table 2 Test No. Test material symbol Amount of flux applied (g / m 2 ) Preheating conditions Dehumidification Dew point of the inert gas (°C) Soldering heating conditions Evaluation results Pressure Highest temperature (°C) Before dehumidification After dehumidification Dew point during heating (°C) Highest temperature (°C) 1 A2 None Normal pressure 200 Carried out -76 -82 -68 600 B 2 A2 None 10 Pa 300 Carried out -74 -80 -80 600 A 3 A1 1 Normal pressure 200 Not carried out -55 -55 -45 600 D 4 A2 None Normal pressure 200 Not carried out -76 -76 -63 600 C

[0083] As shown in Table 2, in Experiments 1 and 2, since the nitrogen gas generated by the inert gas supply device 3 was dehumidified, the dew point of the nitrogen gas supplied to the soldering chamber 2 could be adjusted to -80 °C or less. As a result, a joining efficiency of 85% or more could be achieved.

[0084] On the other hand, in Experiment Nos. 3 and 4, since the dehumidification of the nitrogen gas generated by the inert gas supply device 3 was not performed, it was not possible to adjust the dew point of the nitrogen gas to be supplied into the soldering chamber 2 to -80 °C or less. As a result, the soldering performance was deteriorated, as shown in Table 2. In particular, as shown in Experiment No. 4, even when nitrogen gas formed by evaporating liquid nitrogen was supplied as such, it was not possible to form satisfactory solder joints. (Experimental Example 2)

[0085] In the present example, a cup test specimen 8, which was placed in the Fig. 5 and Fig.6 was used to evaluate the brazing performance in the case where the dew point of the nitrogen gas to be supplied to the brazing chamber 2 was variously changed. In the present example, two types of aluminum materials (test materials B1 and B2) having the chemical components and layer structures shown in Table 3 were prepared. These test materials are single-sided brazing sheets with a thickness of 0.4 mm in which a filler material was bonded to one surface of a core by lamination.

[0086] The cup test specimen 8 (see the Fig. 5 and Fig. 6), which was used to evaluate the solderability in the present example, was manufactured in the following manner. First, press processing was carried out on a sheet material sampled from the test material to produce the circular cups 81 used in the Fig.5 and Fig. 6. The diameter of the cups 81 was 30 mm, and a vent hole 812 with a diameter of 5 mm was formed in the center of the bottom 811 of each cup 81. A flange 813 was formed on the outer peripheral edge portion of each cup 81. Further, as shown in the Fig. As shown in Figure 6, the cups 81 were formed so that the filling material 814 was present on their inside. Subsequently, the cup 81 and a corrugated rib 82 were degreased.

[0087] Here, upper sheets using test material B1 (Table 4, Experiment Nos. 11, 14 and 15) had a fluoride-based flux applied to the filler material 814 in the applied amounts shown in Table 4 in the same manner as in Experimental Example 1.

[0088] The two cups 81 and the corrugated rib 82, which were manufactured in the above-mentioned manner, were used to assemble the test specimen 8, which was used in the Fig. 5 and Fig. 6. The test specimen 8 comprises a hollow member 80 composed of the two cups 81 and the corrugated rib 82 disposed within the hollow member 80. The hollow member 80 includes abutting portions 800 where the flanges 813 of the cup 81 abut each other. The corrugated rib 82 is in contact with the brazing material 814 on the bottom 811 of each cup 81.

[0089] After holding and fixing the test piece 8 in the stacking direction using the jig not shown, the test piece 8 was brazed in the same manner as in Experimental Example 1. In the present example, dehumidification of the nitrogen gas generated by the inert gas supply device 3 was performed in Experiment Nos. 11 to 13. Moreover, dehumidification of the nitrogen gas generated by the inert gas supply device 3 was not performed, and it was supplied as such into the brazing furnace 102 in Experiment Nos. 14 to 17. The conditions for preheating, the dew points of the nitrogen gas before and after dehumidification, and the dew points inside the brazing chamber 2 during brazing heating were as shown in Table 4.

[0090] Test specimen 8 was visually inspected after soldering to determine the appearance of a web F (see the Fig.6) formed outside the adjacent section 800. In the "Evaluation Results" columns, the symbol "A" was indicated in cases where the web had a uniform shape. In cases where a continuous web was formed, although partially non-uniform, the symbol "B" was indicated.

[0091] In cases where the web is uneven throughout, or stitching occurs in part of the web, the symbol "C" is indicated. In cases where stitching is present throughout the web, or where no web is formed, the symbol "D" is indicated. Here, the above-mentioned "stitching" refers to a state where the web is discontinuous; in other words, the web is discontinuous due to defects such as pinholes or the like, and looks like a stitch. Stitching does not always cause leakage of the contents in the hollow member 80; however, in many cases, it is considered a defect because it affects the joining quality of the products, as in the case where no web is formed.

[0092] When evaluating the web shape, the cases of symbols A and B, where continuous webs were formed, were judged acceptable due to satisfactory solderability. On the other hand, the cases of symbols C and D, where tack occurred or where no web was formed, were judged unacceptable due to a risk of soldering failure. Table 3 Table 3 Test material symbol Layer structure Chemical composition (mass%) Lamination percentage (%) Total sheet thickness (mm) Notes Si Fe Cu Mn Mg Bi B1 Filling material 10 - - - - - 10 0,4 Flux soldering Nuclear material 0,27 0,6 0,15 1,2 - - - B2 Filling material 10 - - - - 0,02 10 0,4 Soldering without flux Nuclear material 0,35 - 0,27 - 0,6 - - Table 4 Table 4 Test No. Test material symbol Amount of flux applied (g / m 2 ) Preheating conditions Dehumidification Dew point of the inert gas (°C) Soldering heating conditions Evaluation results Pressure Highest temperature (°C) Before dehumidification After dehumidification Dew point during heating (°C) Highest temperature (°C) 11 B1 1 10 Pa 300 Carried out -74 -80 -80 600 B 12 B2 None 100 Pa 200 Carried out -76 -82 -81 600 B 13 B2 None 10 Pa 300 Carried out -76 -82 -82 600 A 14 B1 1 Normal pressure 200 Not carried out -76 -76 -62 600 C 15 B1 1 10 Pa 300 Not carried out -74 -74 -74 600 C 16 B2 None Normal pressure 200 Not carried out -76 -76 -62 600 D 17 B2 None 100 Pa 200 Not carried out -76 -76 -75 600 C

[0093] As shown in Table 4, in Experiment Nos. 11 to 13, dehumidification of the nitrogen gas generated by the inert gas supply device 3 was performed, and consequently, the dew point of the nitrogen gas to be supplied into the soldering chamber 2 could be adjusted to -80 °C or less. Thus, a continuous ridge could be formed.

[0094] On the other hand, in Experiment Nos. 14 to 17, dehumidification of the nitrogen gas generated by the inert gas supply device 3 was not performed, and consequently, the dew point of the nitrogen gas to be supplied into the soldering chamber 2 could not be adjusted to -80 °C or less. As a result, deterioration of the solderability was caused, as shown in Table 4.

[0095] As shown in Tables 2 and 4, by supplying the dehumidified inert gas into the brazing chamber 2, satisfactory solder joints could be formed when brazing with a reduced amount of flux or when brazing without using a flux. Furthermore, satisfactory solder joints could be formed in both the outer rib test piece 7 and the cup test piece 8 by each brazing.

[0096] As a result, it can be seen that deterioration of the solderability can be effectively limited by performing dehumidification of the inert gas generated by the inert gas supply device 3. Furthermore, it can be seen that since the effects on the solderability due to the atmosphere outside the soldering furnaces 1, 102, and 103 and the storage environment of the object to be processed 100 or the like can be reduced, the amount of moisture introduced into the soldering chamber 2 can be reduced, thereby achieving a satisfactory solder joint, for example, even in areas and seasons with high temperatures and high humidity, or even in cases where strict control of the storage environment of the object to be processed 100 is difficult.

[0097] It should be noted that aspects of the brazing furnace and the brazing method according to the present invention are not limited to the aspects of the above-mentioned embodiments and experimental examples, and their configurations can be modified within a range that does not deviate from the gist of the present invention.

Claims

[1] A brazing furnace (1) used in brazing an article to be processed (100) composed of an aluminum material, comprising: a soldering chamber (2) equipped with a heating device (21) which heats the object (100) to be processed to a soldering temperature; an inert gas supply device (3) which supplies an inert gas into the soldering chamber (2); and a dehumidification device (4) arranged between the inert gas supply device (3) and the soldering chamber (2) and carrying out dehumidification of the inert gas, wherein the dehumidifying device (4) is designed to remove the moisture in the inert gas atmosphere during dehumidification such that the dew point of the inert gas is -80 °C or less. [2] A soldering furnace (1) according to claim 1, wherein the dehumidifying device (4) comprises a moisture absorbing agent (44) that absorbs moisture in the inert gas by bringing it into contact with the inert gas. [3] The brazing furnace (1) according to claim 2, wherein the dehumidifying device (4) further comprises a plurality of gas flow paths (43) connected in parallel with each other, a moisture absorbing means (44) arranged in each gas flow path (43), and a flow path switching device (42) which switches the supply and supply cut-off of the inert gas to each gas flow path (43). [4] A soldering furnace (1) according to claim 2 or 3, wherein the dehumidifying device (4) further comprises a regenerating device (45) that removes moisture absorbed in the moisture absorbing means (44) from the moisture absorbing means (44). [5] Soldering furnace (1) according to one of claims 1 to 4, further comprising: a preheating chamber (5) connected to the soldering chamber (2) and equipped with a preheating device (51) which preheats the object (100) to be processed to a temperature lower than the soldering temperature, a preheating pump (52) which reduces the pressure inside the preheating chamber (5), and a pressure-restoring gas supply device (53) which supplies an inert gas so that the interior of the preheating chamber (5) is repressurized after the pressure reduction. [6] Soldering furnace (1) according to claim 5, wherein the soldering furnace (1) is designed so that the pressure of the interior of the preheating chamber (5) can be reduced to 100 Pa or less. [7] Soldering furnace (1) according to claim 5 or 6, wherein the preheating chamber (5) is designed so that the temperature of the object (100) to be processed can be set to more than 200 °C. [8] A soldering furnace (1) according to any one of claims 1 to 7, further comprising a cooling chamber (6) connected to the soldering chamber (2) and a cooling gas supply device (62) supplying an inert gas into the cooling chamber (6). [9] A method for brazing an aluminum material, in which an article to be processed (100) composed of an aluminum material is brazed in an inert gas atmosphere, the method comprising: Dehumidification of an inert gas; Causing the environment of the object (100) to be processed to be an inert gas atmosphere by supplying the dehumidified inert gas; and Heating the object to be processed (100) to a soldering temperature in the inert gas atmosphere and soldering the object (100) in which dehumidification involves removing moisture in the inert gas atmosphere so that the dew point of the inert gas is -80 °C or less. [10] A method for brazing an aluminum material according to claim 9, wherein, in the dehumidification step, the moisture in the inert gas atmosphere is removed by bringing the inert gas into contact with a moisture absorbing agent (44) which absorbs moisture. [11] A method for brazing an aluminum material according to claim 9 or 10, wherein the article to be processed (100) is preheated to a temperature lower than the brazing temperature in a reduced pressure atmosphere of 100 Pa or less before brazing, whereupon brazing is carried out. [12] A method for brazing an aluminum material according to any one of claims 9 to 11, wherein a fluoride-based flux is applied to a portion to be brazed of the article to be processed (100) before brazing. [13] A method for brazing an aluminum material according to claim 12, wherein the applied amount of the fluoride-based flux is 2 g / m 2or less. [14] A method for brazing an aluminum material according to any one of claims 9 to 11, wherein no flux is applied to a portion to be brazed of the article to be processed (100). [15] A method of brazing an aluminum material according to any one of claims 9 to 14, which is carried out using a brazing furnace (1) according to any one of claims 1 to 8.

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