JPS6356024B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to integral brazing performed in a heating furnace.

The development of integral brazing methods has made it easier to manufacture aluminum structures, such as heat exchangers.
Conventionally, integral brazing was carried out in a salt bath, but due to problems such as processing of the flux used, fluxless brazing methods using vacuum furnaces and the like have recently come to be carried out. In this case, a vacuum heating furnace is generally used. However, in vacuum furnaces where there is no convection of heat from the atmosphere and most of the heating is done by thermal radiation, heating is extremely inefficient even if the heater has sufficient margin, and thermal energy is not used effectively. There are some serious drawbacks. Further, in complex structures where good heat convection is difficult to achieve even in an atmospheric furnace, the time required for brazing may be long and it may be difficult to achieve good brazing.

The object of the present invention is to provide an efficient fluxless integral brazing manufacturing method that improves the above-mentioned drawbacks, and it is also an object of the present invention to obtain a product free of brazing defects. In order to make radiant heat work efficiently on the object to be heated, it is effective to suppress the reflective ability of the surface.
It is also well known that there is a method for this purpose, such as making the surface black. However, difficult problems remain when applying this method to fluxless brazing of complex structures.

In other words, in the case of large heat exchangers made of aluminum, for example, it is not worth the trouble and expense to apply black paint to the surface, and after welding, the paint must be peeled off and the surface cleaned again before the next process. A process is added. Furthermore, according to the inventor's experimental research, when the object to be heated has a complex internal structure, improving the overall radiation activity on the surface can improve heating of the surface of the object, unlike when using the immersion method. It has been found that there are cases where it is difficult to perform good integral brazing because the heat is not transmitted to the inside and heating progresses locally.

The present invention was made based on the results of careful study of the state in which heating progresses when a structure with a complicated shape receives radiant heat. When heated in a vacuum furnace, heat hardly flows from direction A toward the center, but propagates from direction B toward the center according to the thermal conductivity of each structural material, and heat is generated. progresses.
Even if we were to suppress the reflective power of surface 1 of the tube plate and improve its radiation power, the outer surface of the plate would be rapidly heated, but that heat would hardly propagate into the inside of the structure. Therefore, the heating efficiency is not improved much, and there is a risk of failure in integral soldering due to local heating. Therefore, the method of the present invention improves the radiation efficiency of the outer end surface that receives the radiant heat of the structural members that are continuous toward the center, so that the entire structure is quickly heated by the cooperation of the heat conduction of the members. It is characterized by:

To explain more specifically, when manufacturing a heat exchanger core as shown in FIG. After being treated, it is charged into a heating furnace.
The simplest method for suppressing the reflectivity of the end face and improving the radiation is black or dark-colored painting. In this case, the paint must be heated to a wax addition temperature (approximately 600
℃), but it may also be a paint that carbonizes during soldering and turns the painted end surface black-gray, such as lacquer, paint, or oil-based ink for felt-tip pens. Furthermore, in addition to the above-mentioned coating, the reflective ability can be lowered and the amount of absorbed heat can be increased by roughening the end face by mechanical or chemical treatment. Further, it is of course possible to apply the above-mentioned coating on this rough surface to achieve a good effect.

This treatment of only the end face is inexpensive and easy to carry out, and it does not cause any problems in brazing or processing into products after brazing, so there is no need for any further treatment and the radiation efficiency is increased. Good integral brazing progresses quickly even in a vacuum furnace due to the cooperative heat conduction of the parts.

The implementation effects of this method are described below in comparison with the conventional method.

The core of the 125W x 250L x 100H aluminum laminated heat exchanger shown in Figure 1 was placed into a vacuum heating furnace with an internal volume of ^0.4m3 using the conventional method.
When heated to a furnace temperature of 600℃, it took about 30 minutes to complete the brazing.
It took 2.5 hours.

Paint black lacquer on the tube plate end face 2 of the core and the outer end face 3 of the side bar,
When the same temperature was heated to 600°C using the vacuum heating furnace, the time required for brazing was shortened to about 2 hours.
Moreover, good brazing was obtained.

When the end face 2 of the tube plate and the outer end face 3 of the side bar of a similar core were roughened by knurling and heated to the same temperature in the same vacuum heating furnace, the time required for waxing was approximately 2 hours, resulting in defect-free waxing. was carried out.

Under similar waxing heating conditions, when the end surface of the core was roughened and a coating was applied thereon, the time required for brazing was shortened to about 1.5 hours.

The method of the present invention is extremely effective not only for heat exchangers, but also for heating laminated materials or complex structures in a furnace. This improvement in efficiency complements convection heating, resulting in shorter heating times, savings in thermal energy, uniform heating, and other effects.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a structure for a laminated heat exchanger shown for explaining the implementation procedure of the method of the present invention. 1: tube plate surface, 2: tube plate end surface, 3: side bar outer end surface.

Claims (1)

[Scope of Claims] 1. Each plate-like member of a laminated structure is constructed by alternately laminating plate-like members and plate-like fins or other shaped structural members, and are joined together by brazing. A method for integrally brazing a structure, characterized in that the end face and the end face of the structural member facing the end face side are coated with black or dark color and heated in a furnace. 2. The end face of each plate-like member of a laminated structure constructed by alternately laminating plate-like members and plate-like fins or other shaped structural members and bonding them together with brazing, and the end face side thereof. A method for integrally brazing a structure, characterized in that the end face of the structural member facing the structural member is roughened and heated in a furnace.