JP2014237142A - Brazing furnace and brazing method of aluminum material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brazing furnace and a brazing method of aluminum material capable of brazing the aluminum material without using even flux and without requiring an expensive facility such as for vacuum brazing.SOLUTION: A brazing furnace of aluminum material is continuously arranged with a preheating chamber 11 for raising temperature to an aluminum material preheating temperature and having brazing material adhered to a joining part, a brazing chamber 12 for joining the mutual aluminum materials by raising temperature to the preheating temperature before raising temperature to the joining temperature to melt the brazing material and a cooling chamber 13 for cooling the aluminum material after the brazing, and is provided with argon supply means 15 for supplying argon for filling the brazing chamber with an argon atmosphere and nitrogen supply means 16 and 17 for supplying nitrogen for filling the preheating chamber and the cooling chamber with a nitrogen atmosphere, respectively.

Description

  The present invention relates to an aluminum material brazing furnace and a brazing method, and more particularly, to an aluminum material brazing furnace and a brazing method for joining aluminum materials using a brazing material.

Brazing of an aluminum material made of aluminum and an aluminum alloy uses an Al-Si alloy as a brazing material, and heats the brazing material by heating to a temperature higher than the melting temperature of the brazing material, usually about 600 ° C. Therefore, a method of joining aluminum materials is generally performed. In the brazing of an aluminum material, aluminum is very easily oxidized by the reaction of the following formula (1), and when an oxide film is formed, the brazing property is lowered.
2Al + 3 / 2O ₂ → Al ₂ O ₃ (1)
In fluxless brazing, the oxide film at the joint is divided from a dense film form into as fine particles as possible, and the wettability and flow of the molten brazing material (hereinafter sometimes referred to as molten brazing). It is necessary to improve the performance. In addition, it is effective to reduce the oxygen concentration in the furnace atmosphere in terms of improving brazing.

Even when Mg is added to a material such as a brazing material or a brazing target member to divide the oxide film, if the oxygen concentration in the atmosphere is high at the time of brazing, as shown in the following formula (2), Since the oxidation of Mg is promoted and a stable MgO oxide layer is formed thick on the surface, the brazing property is remarkably lowered. During brazing, the oxide film on the surface grows as the temperature is maintained for a long time, but the oxidation reaction proceeds rapidly at 550 ° C. or higher, and the oxidation reaction occurs even in the solid phase.
Mg + 1 / 2O ₂ → MgO (2)
On the other hand, in a state where the oxygen concentration is low, as shown in the following formula (3), the oxide film (Al ₂ O ₃ ) on the aluminum surface is reduced and decomposed by Mg in the material to change into granular MgAl ₂ O _4. Since it is dispersed as a fine oxide, good bonding is performed.
3Mg + 4Al ₂ O ₃ → 3MgAl ₂ O ₄ + 2Al (3)
Therefore, in order to obtain a good bonding state, it is desirable to control the oxygen concentration in the atmosphere as low as possible.

In order to lower the oxygen concentration in the atmosphere, generally the cheapest nitrogen gas is used, but in the melting brazing containing Mg, the oxide film on the surface is destroyed and is in an active state. As shown in the following formula (4), when the wax is melted, it reacts with nitrogen in the atmosphere, and a reaction layer mainly composed of metal nitride (MxNy) is formed on the surface of the molten wax, and the gap filling property is improved. The wax wettability is significantly reduced. However, this reaction is a reaction between the molten brazing (liquid phase) and the atmospheric gas (gas phase), and since the brazing material does not occur in a solid state, the oxygen concentration in the atmosphere in the brazing melting region in the furnace and It is important to reduce the nitrogen concentration.
M (Al, Mg, Si) + N ₂ → MxNy (4)
In the reactions of the above formulas (1) to (4), the reactions are likely to occur in the order of (2), (1), (3), and (4).

  For these reasons, the main brazing methods for aluminum materials are the vacuum brazing method in which the inside of the brazing furnace is evacuated and the nocolok method using non-corrosive flux in addition to the brazing material. Various proposals have been made for these methods (see, for example, Patent Documents 1 to 9).

JP-A-9-85433 JP 2006-175500 A JP-A-9-206980 JP 2002-18570 A Japanese Patent Laid-Open No. 10-180489 International Publication No. 2012/057197 Pamphlet JP 2004-358519 A Japanese Patent Laid-Open No. 2003-3211 JP 2004-183026 A

  However, in the vacuum brazing method, since the degree of vacuum in the furnace greatly affects the brazeability, it is necessary to strictly control the degree of vacuum in the furnace, which not only requires an expensive vacuum furnace, Since the brazing operation is a batch type, mass productivity is low, and there is a limit in reducing brazing cost. Furthermore, when brazing of an aluminum alloy to which Zn is added in order to improve the corrosion resistance of the aluminum product by vacuum brazing, Zn in the aluminum alloy evaporates under vacuum heating, and the aluminum product after brazing There was also a risk that the corrosion resistance of the steel would decrease.

  On the other hand, the Nocolok method is easier to manage the furnace atmosphere than the vacuum brazing method, but it is necessary to apply a flux to the member to be brazed in advance. For this reason, with a member having a complicated structure, it is difficult to sufficiently apply the flux to all the joints, and there is a possibility that poor brazing may occur. Furthermore, since flux residue always exists on the surface after brazing, there is a problem that it is difficult to obtain a stable surface treatment property for parts that require surface treatment after brazing, such as an evaporator, Recently, in inverter coolers and the like used for hybrid vehicles and electric vehicles, there is a problem that flux residue hinders solderability of semiconductor components.

  Accordingly, an object of the present invention is to provide an aluminum brazing furnace and a brazing method capable of brazing an aluminum material without using expensive equipment such as vacuum brazing and without using a flux. It is said.

  In order to achieve the above object, a brazing furnace for an aluminum material according to the present invention is the brazing furnace for an aluminum material in which the brazing material is used to join the aluminum material. A preheating chamber that raises the aluminum material to a preset preheating temperature, and after raising the temperature to the preheating temperature, the aluminum material is joined by melting the brazing material by raising the temperature to a preset joining temperature. An argon supply means for continuously supplying a brazing chamber and a cooling chamber for cooling the brazed aluminum material, and supplying argon for making the brazing chamber into a preset argon atmosphere, and the preheating And a nitrogen supply means for supplying nitrogen for making each of the chamber and the cooling chamber into a preset nitrogen atmosphere. It is characterized by a door.

  Furthermore, in the brazing furnace for an aluminum material of the present invention, the oxygen concentration in the argon atmosphere in the brazing chamber is 50 ppm or less, and the nitrogen concentration in the argon atmosphere in the brazing chamber is 10% by volume or less. The oxygen concentration in the nitrogen atmosphere in the preheating chamber and the oxygen concentration in the nitrogen atmosphere in the cooling chamber are each 100 ppm or less, and the magnesium content of the brazing material is 0.05 to 5.0% by weight. It is characterized by that.

  Further, the brazing method for an aluminum material according to the present invention is an aluminum material brazing method for joining an aluminum material using a brazing material. A preheating step of raising the temperature to a preset preheating temperature in a preset nitrogen atmosphere, and after raising the temperature to the preheating temperature, raising the temperature to a preset joining temperature in a preset argon atmosphere It is characterized by continuously performing a brazing step of joining aluminum materials by melting the material and a cooling step of cooling the brazed aluminum material in a preset nitrogen atmosphere.

  Furthermore, in the brazing method for an aluminum material of the present invention, the oxygen concentration in the argon atmosphere in the brazing step is 50 ppm or less, and the nitrogen concentration in the argon atmosphere in the brazing step is 10% by volume or less. The oxygen concentration in the nitrogen atmosphere in the preheating step and the oxygen concentration in the nitrogen atmosphere in the cooling step are each 100 ppm or less, and the magnesium content of the brazing material is 0.05 to 5.0% by weight. It is characterized by that.

  According to the present invention, it is possible to braze an aluminum material without making the atmosphere in a vacuum state and without using a flux. In addition, by making only the atmosphere during brazing where the brazing material melts into an argon atmosphere, the fluidity and wettability of the molten brazing can be improved, and brazing can be performed reliably and with reliability. Can be improved. Further, by performing preheating and cooling in a nitrogen atmosphere without using an argon atmosphere as a whole, the amount of argon used can be reduced and the operating cost can be reduced. In addition, by suppressing the oxygen concentration in each atmosphere below a preset concentration, oxidation of the brazing material and aluminum material can be prevented, and the nitrogen concentration in the atmosphere during brazing is set to a predetermined concentration. By suppressing to the following, it is possible to prevent the molten wax from nitriding.

It is explanatory drawing which shows one example of the brazing furnace of the aluminum material of this invention. It is a perspective view which shows the test material produced in the Example. It is a figure which shows the temperature change in an Example.

  FIG. 1 shows an embodiment of a brazing furnace for carrying out the method of brazing an aluminum material of the present invention. This aluminum brazing furnace has a preheating chamber 11 for performing a preheating process, a brazing chamber 12 for performing a brazing process, and a cooling chamber 13 for performing a cooling process, which are continuously provided. 11. Inside the brazing chamber 12 and the cooling chamber 13, a conveying means for conveying the aluminum material to be brazed, for example, a mesh belt type conveyor 14, is provided. Between the chambers 11, 12, and 13, in order to suppress the intrusion of the atmosphere as much as possible, the aluminum material to be brazed is formed in a connected state through an opening or tunnel through which gas can flow. Shutters, curtains, and gas curtains can also be provided to prevent air from entering.

  The brazing chamber 12 is provided with an argon supply means 15 for supplying argon into the brazing chamber 12, and the preheating chamber 11 and the cooling chamber 13 are supplied with nitrogen for supplying nitrogen into each chamber. Supply means 16 and 17 are provided, respectively. Supply sections for supplying each gas from the argon supply means 15 and the nitrogen supply means 16 and 17 into each chamber can be provided at a plurality of locations according to the size and shape of each chamber.

  The preheating chamber 11 performs a preheating process in which the aluminum material to which the brazing material is adhered is preheated to a preset preheating temperature close to the temperature at which the brazing material melts, and the preheating chamber 11 is supplied with nitrogen. The nitrogen atmosphere supplied from the means 16 is controlled so as to obtain a preset nitrogen atmosphere. The nitrogen supply means 16 includes a flow rate adjusting means capable of adjusting the supply amount of nitrogen as required. The amount of nitrogen supplied from the nitrogen supply means 16 into the preheating chamber 11 varies depending on conditions such as the shape of the preheating chamber 11 and the shape of the joint, but normally, the amount of supply per minute is set in the preheating chamber 11. Nitrogen is supplied into the preheating chamber 11 so that the volume is set to 1.0 times or more, preferably 1.3 times or more of the volume, and the atmospheric gas in the preheating chamber 11 is discharged from the inlet of the preheating chamber 11. By appropriately setting the position, the number of installed supply units, the supply amount, and the like, it is possible to suppress the intrusion of the atmosphere from the entrance of the preheating chamber 11 into the preheating chamber 11 as much as possible.

  By forming the preheating chamber 11 in this way, it is possible to suppress the intrusion of air from the inlet portion into the preheating chamber 11, so that the oxygen concentration in the atmosphere of the preheating chamber 11 can be lowered, and the atmosphere It is possible to suppress the growth and thickness of the oxide film of the aluminum material or the brazing material by setting the oxygen concentration of the steel to 100 ppm or less. Furthermore, by controlling the oxygen concentration in the atmosphere to 50 ppm or less, the growth of the oxide film can be suppressed more reliably. This makes it possible to suppress the deterioration of the wettability and fluidity of the brazing material when the brazing material is melted in the next brazing process due to the thickened oxide film, and ensures brazing in the brazing process. Can be done. In the range where the temperature of the aluminum material or the like is low on the inlet side of the preheating chamber 11 and there is almost no growth of the oxide film, there is no problem even if the oxygen concentration exceeds 100 ppm.

  That is, in the brazing of an aluminum material, since the oxidation of the aluminum material proceeds as the temperature rises, it is essential to reduce the oxygen concentration in the high temperature atmosphere. Therefore, it is advantageous in terms of cost to suppress oxidation using the least expensive nitrogen gas.

  The brazing chamber 12 performs a brazing process in which the aluminum material and the brazing material are heated to a predetermined brazing temperature, the brazing material is melted, and the aluminum materials are joined to each other by the molten brazing. The inside 12 is controlled so as to have a preset argon atmosphere by argon supplied from the argon supply means 15. The argon supply means 15 includes a flow rate adjusting means capable of adjusting the supply amount of argon as required. The amount of argon supplied from the argon supply means 15 into the brazing chamber 12 is the shape of the brazing chamber 12 or the like. Usually, it is preferable to set the supply amount per minute to 0.8 times or more, preferably 0.9 times or more the volume of the brazing chamber 12. The atmospheric gas in the brazing chamber 12 flows into the adjacent preheating chamber 11 and cooling chamber 13, but does not adversely affect the processes in the preheating chamber 11 and cooling chamber 13.

  Also in this brazing chamber 12, the oxygen concentration in the argon atmosphere can be controlled to 50 ppm or less and the nitrogen concentration to 10 volume% or less by appropriately setting the supply amount of argon, the position of the supply unit, and the number of installations. It is possible to prevent the flowability and wettability of the wax from being reduced due to oxidation or nitridation of aluminum or magnesium contained in the aluminum material or the molten wax. Furthermore, by controlling the oxygen concentration to 25 ppm or less and the nitrogen concentration to 1% volume or less, oxidation and nitridation of aluminum and magnesium can be suppressed more reliably.

  Further, in the brazing chamber 12, the allowable value of the nitrogen concentration can be set higher than the oxygen concentration in the atmosphere, so that nitrogen enters the brazing chamber 12 from the adjacent preheating chamber 11 and cooling chamber 13. Therefore, it is possible to reduce the amount of argon supplied from the argon supply means 15 into the brazing chamber 12 as compared with the case where nitrogen intrusion is completely prevented. As a result, it is possible to reduce the gas cost by reducing the amount of argon that is more expensive than nitrogen.

  That is, the brazing process in the brazing chamber 12 is a process in which the brazing material is melted and the aluminum materials are joined together by the molten brazing. In this step, if the nitrogen concentration in the atmosphere after the brazing material is melted is high, a nitride layer is formed on the surface of the molten brazing, so that the wettability of the brazing is remarkably lowered and sufficient bonding cannot be obtained. In particular, in the case of a brazing material containing magnesium, since the brazing material surface is activated, a nitride layer is easily formed. Since this nitride layer is formed by the reaction between the liquid phase melting wax and the gas phase nitrogen, the atmosphere above the temperature range where the wax starts to melt is changed to an argon atmosphere in which the oxygen concentration and nitrogen concentration are controlled. In addition, it is possible to suppress the oxidation or nitridation of aluminum or magnesium and to improve the stability of bonding.

  The cooling chamber 13 performs a cooling process for cooling the aluminum material that has been brazed in the brazing process of the brazing chamber 12 to a temperature that can be taken out of the furnace. The inside of the cooling chamber 13 is controlled by the nitrogen supplied from the supply means 17 so as to have a preset nitrogen atmosphere. Similarly to the other supply means, the nitrogen supply means 17 in the cooling chamber 13 also includes a flow rate adjusting means that can adjust the supply amount of nitrogen as required. The amount of nitrogen supplied from the nitrogen supply means 17 into the cooling chamber 13 varies depending on conditions such as the shape of the cooling chamber 13, but normally the supply amount per minute is 1 with respect to the volume in the cooling chamber 13. It is preferable to set it to be twice or more and to discharge the atmospheric gas from the outlet of the cooling chamber 13. As a result, the aluminum material after brazing can be effectively cooled in a short time with an appropriate amount of nitrogen, the handleability of the aluminum material after brazing can be improved, and oxidation of the aluminum material after removal can be prevented. Intrusion of air into the cooling chamber 13 from the outlet can also be suppressed. Further, by supplying 1.3 times or more of nitrogen with respect to the volume in the cooling chamber 13, the cooling effect of the aluminum material and the air inflow suppressing effect can be further enhanced.

  By forming the cooling chamber 13 in this way, air can be prevented from entering the cooling chamber 13 from the outlet, so that the oxygen concentration in the atmosphere of the cooling chamber 13 can be reduced as much as possible. It is possible to suppress the growth of the oxide film of the aluminum material or the brazing material by setting the oxygen concentration therein to 100 ppm or less, and the wettability of the brazing is not hindered. Furthermore, by controlling the oxygen concentration in the atmosphere to 50 ppm or less, the growth of the oxide film can be suppressed more reliably. Note that there is no problem even if the oxygen concentration exceeds 100 ppm in the range where the cooling of the aluminum material or the like has progressed on the exit side of the cooling chamber 13.

  That is, in the cooling process in the cooling chamber 13, it is necessary to regulate the oxygen concentration in the atmosphere in order to suppress the growth of the oxide film on the material surface. In addition, since aluminum does not have reactivity with nitrogen, as in the preheating chamber 11, it is advantageous in terms of cost to reduce the oxygen concentration by using an inexpensive nitrogen atmosphere without using argon.

  The brazing material to be used may be an appropriate brazing material selected according to the type of aluminum material, and the magnesium content in the brazing material is preferably in the range of 0.05 to 5.0% by weight. If the content is less than 0.05%, the redox effect of magnesium cannot be sufficiently obtained. If the content exceeds 5.0% by weight, the magnesium remains in the brazing material during the brazing and melts. A flow may worsen, wettability may fall, and a clearance gap may generate | occur | produce in a brazing part. Therefore, brazing of an aluminum material can be more reliably performed by making magnesium content in a brazing material into the range of 1.0 to 2.0 weight%.

  As described above, in the continuous brazing furnace in which the preheating chamber 11, the brazing chamber 12, and the cooling chamber 13 are continuously provided, the brazing chamber 12 in which the brazing material may be melted and nitrided may be in an argon atmosphere. And reducing the cost of the gas to be used while brazing the aluminum material reliably by making the preheating chamber 11 and the cooling chamber 13 in which the brazing material is not melted and nitriding into a nitrogen atmosphere. Can do. Further, by appropriately setting the supply amount and supply position of nitrogen supplied to the preheating chamber 11 and the cooling chamber 13, the atmosphere enters the furnace from the inlet portion of the preheating chamber 11 and the outlet portion of the cooling chamber 13 that are in contact with the atmosphere. This can be suppressed.

  Thereby, the oxygen concentration in the nitrogen atmosphere of the preheating chamber 11 and the cooling chamber 13 can be controlled to 100 ppm or less, preferably 50 ppm or less, and the growth of an oxide film of an aluminum material or a brazing material can be prevented. In addition, this makes it possible to suppress an increase in the oxygen concentration in the argon atmosphere of the brazing chamber 12 sandwiched between the preheating chamber 11 and the cooling chamber 13. Further, the supply amount of argon supplied to the brazing chamber 12 In addition, by appropriately setting the supply position, the amount of nitrogen flowing from the preheating chamber 11 or the cooling chamber 13 into the brazing chamber 12 can be reduced, and the aluminum material heated to a high temperature or the wax melted at a high temperature is oxidized. Or being nitrided can be prevented. Therefore, it is possible to reliably braze the aluminum material at a low cost.

  As shown in FIG. 2, the core alloy is equivalent to A3003, the brazing alloy is equivalent to A4004, the brazing aluminum clad rate is 10%, and the corrugated fin 22 corresponding to A3003 is combined with a corrugated fin 22 in width (W) 50 mm. Then, a brazing experiment was performed on the specimen 23 having a shape with a depth (D) of 25 mm.

The brazing furnace has a preheating chamber with a height of 95 mm, a width of 200 mm and a length of 1380 mm, a brazing chamber with a height of 95 mm, a width of 200 mm and a length of 3030 mm, and a cooling chamber with a height of 95 mm, a width of 200 mm and a length of 4000 mm. A mesh belt having a belt width of 200 mm and a total length of 12 m is installed over the preheating chamber, the brazing chamber and the cooling chamber. The total volume of the brazing furnace is about 0.16 m ³ .

  As shown in Table 1, Experimental Examples 1 and 2 in which argon was supplied to all the chambers, Experimental Examples 3 to 6 in which nitrogen was supplied to all the chambers, nitrogen was supplied to the preheating chamber and the cooling chamber, and the brazing chamber was supplied. Experiments 7 to 20 in which argon was supplied were performed by changing the oxygen concentration and the nitrogen concentration. The temperature conditions were the same as shown in FIG. 3 in all experiments. During the experiment, the oxygen concentration in each atmosphere in the preheating chamber, the brazing chamber, and the cooling chamber was measured with a zirconia oxygen analyzer, and the nitrogen concentration in the brazing chamber was measured by gas chromatography.

  The amount of argon reduction in Table 1 is calculated by the following equation (5), and the brazing property is obtained by calculating the bonding rate of fins by the following equation (6). Less than 90% was marked as cross.

Argon reduction amount = (1− (argon flow rate / atmospheric gas total flow rate)) × 100 (5)
Fin joint rate = (total brazed joint length of fin and tube / total contact length of fin and tube) × 100 (6)
The experimental conditions and results are summarized in Table 1.

  DESCRIPTION OF SYMBOLS 11 ... Preheating chamber, 12 ... Brazing chamber, 13 ... Cooling chamber, 14 ... Conveyor, 15 ... Argon supply means, 16 ... Nitrogen supply means, 17 ... Nitrogen supply means, 21 ... Aluminum brazing sheet, 22 ... Corrugated fin, 23 ... Sample material

Claims (10)

  In a brazing furnace for an aluminum material in which an aluminum material is joined using a brazing material, a preheating chamber for raising the temperature of the aluminum material with the brazing material adhered to the joining portion of the aluminum material to a preset preheating temperature, and preheating After raising the temperature, the brazing chamber for joining the aluminum materials by melting the brazing material by raising the temperature to a preset joining temperature and the cooling chamber for cooling the aluminum material after brazing are continuously provided. And an argon supply means for supplying argon for setting the brazing chamber to a preset argon atmosphere, and nitrogen for setting the preheating chamber and the cooling chamber to a preset nitrogen atmosphere, respectively. A brazing furnace of aluminum material provided with nitrogen supply means for supplying   The brazing furnace for an aluminum material according to claim 1, wherein the oxygen concentration in the argon atmosphere in the brazing chamber is 50 ppm or less.   The brazing furnace for an aluminum material according to claim 1 or 2, wherein a nitrogen concentration in an argon atmosphere in the brazing chamber is 10% by volume or less.   The brazing furnace for an aluminum material according to any one of claims 1 to 3, wherein an oxygen concentration in a nitrogen atmosphere in the preheating chamber and an oxygen concentration in the nitrogen atmosphere in the cooling chamber are each 100 ppm or less.   The brazing furnace for an aluminum material according to any one of claims 1 to 4, wherein the brazing material has a magnesium content of 0.05 to 5.0% by weight.   In a brazing method for an aluminum material in which an aluminum material is joined using a brazing material, an aluminum material in which the brazing material is adhered to the joining portion of the aluminum material is preliminarily set in a preset nitrogen atmosphere. A preheating step of raising the temperature to a preheating temperature, and after raising the temperature to the preheating temperature, brazing the aluminum materials by raising the temperature to a preset joining temperature in a preset argon atmosphere and melting the brazing material A brazing method for an aluminum material, wherein the step and a cooling step of cooling the brazed aluminum material in a preset nitrogen atmosphere are continuously performed.   The method for brazing an aluminum material according to claim 6, wherein the oxygen concentration in the argon atmosphere in the brazing step is 50 ppm or less.   The method for brazing an aluminum material according to claim 6 or 7, wherein a nitrogen concentration in the argon atmosphere in the brazing step is 10% by volume or less.   The method for brazing an aluminum material according to any one of claims 6 to 8, wherein an oxygen concentration in the nitrogen atmosphere in the preheating step and an oxygen concentration in the nitrogen atmosphere in the cooling step are each 100 ppm or less.   The method for brazing an aluminum material according to any one of claims 6 to 9, wherein a magnesium content of the brazing material is 0.05 to 5.0% by weight.

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