JPS5992162A - Production of heat exchanger - Google Patents

Abstract

PURPOSE:To reduce stages and to eliminate the need for a waste water treatment by performing a pretreatment stage prior to welding of a heat exchanger made of Al or an Al alloy by a heating treatment without defatting and chemical cleaning. CONSTITUTION:A heat exchanger is produced by a stage for assembling the tubes and fins of the heat exchanger consisting of Al or an Al alloy clad with a brazing material on at least the tubes or fins, a pretreatment stage prior to brazing, a flux adhering stage and brazing stage. The pretreatment stage prior to the brazing is performed by heating the tubes and fins from 250 deg.C to the m.p. of the solder or below in an oxidative atmosphere and from 300 deg.C to the m.p. of the solder or below in a mixed atmosphere of one kind or >=2 kinds among the air, hydrogen, oxygen and inert gas or in vacuum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for manufacturing At and At alloy heat exchangers, and particularly to a pretreatment method optimal for brazing tubes and fins.

[Prior art]

The conventional wax treatment process for heat exchanger tubes and fins involves a degreasing process to remove oil stains during machining and a chemical cleaning process to remove the oxide film on the surface.Tubes that have undergone this process. The fins are well wetted with the flux bath solution, and the flux adheres evenly. However, these degreasers have the disadvantage of requiring a large amount of equipment to invest in chemical cleaning processes and treatment of waste liquids.

[Purpose of the invention]

The purpose of the present invention is to heat and remove oil and other dirt adhering to the surfaces of tubes and fins of At and AA alloy heat exchangers, and to uniformly apply a 7lux aqueous solution to the surfaces. The object of the present invention is to provide a method for processing a wax surface in order to obtain a fine-looking wax surface.

[Summary of the invention]

It is well known that pretreatment of the solder is important in order to obtain a healthy solder part. The purpose of pretreatment is to remove oil, other dirt, and oxide film. Conventionally, for this purpose, degreasing using trichlorethylene, acetone, etc., and chemical cleaning using KOH aqueous solution, Na01l aqueous solution, etc. have been carried out. Generally practiced At and At
Furnace brazing of the tubes and fins of an alloy heat exchanger involves a brazing treatment process in which the heat exchanger is immersed in an aqueous flux solution, and degreased and chemically cleaned to uniformly adhere the flux. As a result of various studies regarding this brazing treatment process, it was found that oil and other dirt are burned or evaporated by heating, so that the flux adheres uniformly.

The atmosphere at the time of heating is the most effective (250C heating shows its effect, and even in other atmospheres or vacuum)
It has been found that heating at 00 to 350C produces this effect, and that even if the oxide film is removed by chemical cleaning, a healthy wax part can be obtained.

The present invention is characterized in that at least one side is clad with a brazing material.
A process for assembling heat exchanger tubes and fins made of T or At alloy, a brazing process, a fujitsu attachment process, and a brazing process in which degreasing and chemical cleaning are not performed during the brazing process. In addition, the brazing process is carried out in an oxygen atmosphere from 250C to below the melting point of the wax in the atmosphere.

3 (1(l t,'
The present invention provides a method for manufacturing a heat exchanger made of Kl and At alloys, which is characterized by heating to a temperature below the melting point of Karawa.

[Embodiments of the invention]

The first embodiment of the present invention will be described below. 50m5X50Wn X as machined and heat treated in oxygen and air
Figure 1 shows the results of looking at the spread of the water quotient when a 1 tnm A4 plate was placed horizontally and water droplets were dropped one by one on it. Machine 〃11 Wet spread as it was, M
It can be seen that when the fi product is 1, the higher the heating temperature, the larger the wetted area and the better the wettability with water. The important point for this effect to appear is 250 tl' when heating in an oxygen atmosphere.

In the case of heating in the air, it was 350c. The water spread rate of the test piece that was degreased and chemically cleaned was 3.3, and the same wet spread rate was obtained at 300 C in an oxygen atmosphere and at 400 r in the air.

In addition, Kli'-A7B containing 2LIAtF as a complex compound
Figure 2 shows the results of a wax wetting and spreading test using a 0% aqueous solution of '3-Lrp yarn flux. The soldering material is made of material 4343 [α diameter 2-way soldering material is 13wn in diameter]
The material and shape of the plate were the same as those used in the study of water wettability.

The wetting and spreading rate of the wax was set to 1 for an area with a diameter of 13 mm.

When machined as is, the variation was large and the wetting spread rate was small. This is because the flux aqueous solution aggregated in one place and could not be applied uniformly. It can be seen that degreasing and chemical cleaning improve the wet spread rate and reduce the variation, indicating that they are effective. In the case of a test piece heat-treated in an oxygen atmosphere, the wetting and spreading rate improves up to 400C and becomes the same as that of a test piece that has been degreased and chemically cleaned. 500
In case of C, the variation is large and the wetting rate is also low.

The reason for this is that the oxidized film becomes thicker due to heating, and the oxide film cannot be completely removed by the flux, but it can be seen that brazing can be performed satisfactorily by the action of the flux alone without chemical cleaning. Furthermore, the heat exchanger tube (A7050+ and fins (placing sheet)
Assemble and heat in oxygen atmosphere [medium f400C, 10% after aging]
After being immersed in Frank's aqueous solution and dried, brazing was performed in a room water atmosphere furnace. As a result, fillets were formed on the tube and fin + U, and a healthy brazing section was obtained.

〔Effect of the invention〕

According to the present invention, since the brazing treatment process for heat exchangers made of A7 and At alloys is performed only by heat treatment without degreasing or chemical cleaning, there is an effect of shortening the process and reducing the failure of one-shot liquid processing.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the heating temperature before brazing and the wetting spread of water 9, and Fig. 2 is a diagram showing the relationship between the heating temperature before brazing and the wetting spread of the wax.

Claims (1)

[Claims] 1. Assembling tubes and fins of a heat exchanger made of At or A/=gold alloy with at least one side clad with a brazing material, a wax bending process, a flux adhesion process, a brazing process. A method for manufacturing a heat exchanger, characterized in that in the wax treatment step, heating is performed from 250C to below the melting point of the wax in an oxidizing atmosphere. 2. The method for manufacturing a heat exchanger according to claim 1, wherein degreasing and chemical cleaning are not performed in the wax treatment step. 3. In the wax wax treatment step, the wax is heated from 300 C to below the melting point of the wax in an atmosphere of air, nitrogen and an inert gas, or a mixed atmosphere of 2a1 or more, or in a vacuum. Method for manufacturing the heat exchanger described in Section 1.