JPH0655349B2 - Vacuum brazing method for aluminum - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for brazing an aluminum product.

[Prior Art] There are aluminum heat exchangers such as radiators, condensers, and evaporators for automobile parts.
These parts are vacuum brazed using a vacuum brazing furnace, for example when attaching fins to fin tubes.

A conventional vacuum brazing furnace facility will be briefly described with reference to FIG. 3. Reference numeral 1 is a furnace body of a vacuum brazing furnace having an exhaust port 1a at the upper portion, and 2 is an inner wall of the furnace interior 3 and a furnace bottom portion. The heat shields 4 provided are heaters, and the portion surrounded by the heaters 4 is the processing space S ₁ . Further, 5 is a carrier frame on which the object to be treated W is set, and the carrier frame 5 is carried in and out of the furnace 3 by a carrier mechanism 6 provided on the ceiling of the furnace 3. Has become. A space above the processing space S ₁ in which the transport mechanism 6 is provided is a transport space S ₂ .

A method for brazing the object W to be processed using such a vacuum brazing furnace facility will be described. The object W to be processed is set on the carrier frame 5 installed in the furnace 3 and conveyed together with the carrier frame 5. The inside of the furnace 3 is charged by the mechanism 6, the inside of the furnace 3 is evacuated, and then the inside of the furnace 3 is heated to melt the brazing material coated on the fixed parts in advance to braze the parts together.

The brazing filler metal used contains magnesium, which has a higher affinity for oxygen than aluminum, in order to prevent the aluminum from forming an oxide coating by combining with oxygen during brazing and making brazing difficult. ing. For this reason, the oxide coating is destroyed by magnesium, and more oxygen is bonded to the magnesium side to prevent oxidation of the brazed portion.

In addition, when brazing particularly high quality brazing products, spare vacuum chambers are installed on the inlet side and outlet side of the furnace to make the entire equipment a three-chamber structure, Some are designed to be more sophisticated.

[Problems to be Solved by the Invention] By the way, when brazing is performed by the above method and a vacuum brazing furnace, the magnesium contained in the brazing material is combined with oxygen to scatter into magnesium oxide. Or, the magnesium that could not be bonded is scattered around. The scattered magnesium adheres to the heat shield plate 2 in the furnace 3, the transfer mechanism 6, or the inner wall of the furnace to cause contamination, and the adhered magnesium causes an obstacle to the movement of the transfer mechanism 6 and the movement of the furnace door. Go out.

Moreover, since the temperature of the transport space S ₂ is lower than that of the processing space S ₁ , magnesium tends to adhere to the transport space S ₂ . Since the attached magnesium is porous and has a large surface area, a large amount of water is likely to be adsorbed, which causes the performance of vacuum evacuation to deteriorate.

Therefore, must be frequently performed operation for removing magnesium adhered and work difficult to do narrow transport space S _2, also the heat shield plate 2, also several layers a plurality of plates with a space Since they were superposed, it was very time-consuming to remove the adhering substances that entered the gaps between the plates.

Further, in the space between the object to be processed W and the heat shield plate 2, there are magnesium molecules that have rebounded upon hitting the heat shield plate 2, but this space is large and some of them are exhausted, so magnesium The molecular density is not so high. That is, since the magnesium molecule density of the atmosphere of the brazing part is not so high, it was a disadvantage in promoting the antioxidant reaction of aluminum.

Further, in the three-chamber structure, good brazing quality can be obtained, but again there is a problem that the above-mentioned contamination of the inside of the furnace by magnesium cannot be avoided and the installation space of equipment is large. It was

[Means for Solving Problems] The present invention has been made in order to solve the above problems, and when brazing an object to be processed which is an aluminum product in a vacuum brazing furnace, each object to be processed is It is characterized in that an object is housed in a box body having a gap communicating with the inside and outside to be optically shielded, and in that state, the furnace is degassed or heated while the gas is discharged.

[Operation] According to the above aluminum vacuum brazing method, first,
When the inside of the box is evacuated, the gas inside the box flows out through the gap, and the inside of the box becomes a vacuum state together with the inside of the furnace. After that, when the temperature in the furnace is raised to about 400 ° C., the magnesium molecules in the brazing material scatter. In this case, magnesium molecules scatter in a vacuum state, so that the magnesium flow becomes a molecular flow. Therefore, unlike the case of viscous flow, almost no magnesium molecules leak to the outside from the optically shielded gap.

Therefore, the density of magnesium molecules in the box becomes high,
Antioxidation of the brazed part improves the reaction more than before. Also,
Since magnesium molecules do not leak to the outside of the box, contamination inside the furnace is reduced.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2 (a) (b).
This will be explained with reference to (C).

FIG. 1 shows the same vacuum brazing furnace equipment as that shown in FIG. 3, and the reference numeral 10 is a box suitable for carrying out the present method.

First, the box 10 will be described with reference to FIGS. 2 (A), 2 (B) and 2 (C).

This box body 10 is an upper lid 1 made of a thin plate such as stainless steel.
1 and a bottom plate 12.

The upper lid 11 is a rectangular parallelepiped box body that opens downward,
The size of the inside is set to be slightly larger than that of the object W having a substantially rectangular parallelepiped outer shape so that the object W can be stored as close as possible.

One of the bottom plates 12, on which the object W to be processed is placed, has its peripheral portion bent upward by a predetermined length to form a frame 12a as shown in FIGS. 2 (a) and (b). Has been done. The size of the inside surrounded by the frame 12a is set so that there is a slight gap 13 and the opening of the upper lid 11 is fitted.

Further, the box body 10 includes a bottom plate 12 on which the workpiece W is placed.
When the upper lid 11 is covered with a space between the workpiece W and the object W to be processed, the opening of the upper lid 11 is left in the frame 12a of the bottom plate 12 with a gap 1
It is configured to overlap with each other with a gap 3 and to be held in a state in which a gap 14 is provided between the lower edge of the upper lid 11 and the bottom portion of the bottom plate 12.

At this time, the inside of the box body 10 is in a state in which it cannot be seen from any angle through the gap 13 from the outside, that is, a state in which it is optically shielded.

The plate material forming the box body 10 is preferably covered with a black oxide film on both the surface and the inner surface so that the emissivity is stable at a large value. That is, in order to heat the object W to be processed, the box body 10 is first heated by the radiant heat of the heater 4, and the object W to be processed is heated by the heated box body 10. Therefore, it is preferable that the box 10 has a large emissivity so that there is no difference between the temperature rising pattern of the furnace and the temperature of the object W to be processed. Therefore, the box 10 is preferably covered with the black oxide film as described above. .

Next, the operation procedure of the brazing method of the present invention using the box 10 and the vacuum brazing furnace facility described above, and the effect of the box 10 accompanying this will be described.

First, when the object W to be processed is put into the furnace, (1) the object W to be processed is placed on the bottom plate 12 of the box body 10, and the upper lid 11
Cover. At this time, the lower edge of the upper lid 11 is the frame 1 of the bottom plate 12.
2a and a small gap 13 are overlapped with each other, and there is a gap 14 between the lower edge of the upper lid 11 and the bottom portion of the bottom plate 12. As a result, the inside of the box body 10 cannot be seen from any of the gaps 13 and 14 from any angle, that is, the inside of the box body 10 is optically shielded, and the inside of the box body 10 is communicated with the outside by the gaps 13 and 14. It becomes a state.

(2) After placing the box body 10 in which the workpiece W is stored on the carrier frame 5 as described above,
The box body 10 together with the carrier frame 5 is loaded into the furnace 3 by the transfer mechanism 6.

Next, in order to braze the workpiece W, (3) the furnace interior 3 is sealed and the furnace interior 3 is evacuated. At this time, the gas in the box body 10 flows out of the box body 10 through the gaps 13 and 14, and the inside of the box body 10 becomes a vacuum state together with the furnace 3.

(4) Next, the heater 4 is turned on to heat the furnace 3 to a predetermined brazing temperature.

(5) The radiant heat from the heater 4 is transmitted to the box body 10, and the heat of the box body 10 is radiated to the object W to be treated inside the box body 10 to heat the object W to be brazed.

(5) The brazing filler metal coated on the brazing part of the workpiece W is melted, and at this time, magnesium contained in the brazing filler metal is combined with oxygen to prevent oxidation and is scattered as magnesium oxide. Single magnesium that could not be bonded scatters. These are blocked by the box body 10 and do not scatter toward the furnace wall. Therefore, unlike the conventional case, magnesium does not adhere to the heat shield plate 2, the transport space S _{2, and the} like.

Further, most of the magnesium scatters in the narrow space between the box 10 and the object W to be processed, so that the magnesium molecule density in this space becomes high. This magnesium molecule flows out of the box body 10 as a viscous flow from the gaps 13 and 14 when the furnace 3 is not in a vacuum, but since it is a vacuum, this viscous flow does not occur and the magnesium molecule becomes a molecular flow. Existing inside the box 10. Since this molecular flow is a linear motion, it hardly exits outside through the gaps 13 and 14, and therefore the magnesium molecule density around the object W to be processed becomes high. Therefore, at the time of brazing, the ability to absorb oxygen existing around the object to be processed W is increased, so that the object to be processed W
The brazed part of B is brazed well without being oxidized.

[Effects of the Invention] As described above, the aluminum vacuum brazing method of the present invention has the following effects.

(1) By storing the object to be processed in a box that optically shields, the density of magnesium molecules around the object to be processed becomes higher, so that the antioxidation reaction of the brazing part is improved and the brazing quality is improved. Good product is obtained.

(2) The operating cost can be reduced because it is not necessary to have a high degree of vacuum in the entire furnace.

(3) Since the inside of the furnace is hardly contaminated by the magnesium scattered during the brazing, the maintenance work of the furnace becomes easy and the intervals can be set longer.

(4) The amount of magnesium contained in the brazing material can be reduced to the necessary minimum.

(5) It is not necessary to use a three-chamber structure as in the conventional case, even when the product has a particularly high brazing quality.

[Brief description of drawings]

1 and 2 are diagrams showing an embodiment of the present invention, in which FIG. 1 is a vertical sectional view of a vacuum furnace facility equipped with a vacuum brazing furnace, and FIG. 2 (a) (b) ( (C) is a front view, a side view, and a plan view, respectively, of a state in which an object to be processed is stored in a box, and FIG. 3 is a vertical sectional view of a conventional vacuum furnace facility. 10 ... Box, 13, 14 ... Gap, W ... Object to be processed.

Claims (1)

[Claims] 1. A box having a gap for communicating the inside and outside of an aluminum object to be processed when the object to be processed is brazed in a vacuum brazing furnace with a brazing material containing magnesium as a reducing agent. A vacuum brazing method for aluminum, which is characterized in that it is housed in the body, optically shielded, and then heated in the state after degassing the furnace or while performing degassing.