JPS6031592B2 - Flux-free brazing method for Al alloy members containing elements that easily vaporize during brazing as alloy components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an aluminum alloy containing elements that easily vaporize during brazing, such as Zn and Mg, as an alloy component, for the purpose of imparting an anticorrosion effect through sacrificial anode action and improving strength.
This relates to the fluxless brazing method of Alloybemura.

Recently, in the manufacture of automotive heat exchangers such as car cooler condensers and radiators, Zn and M are used to provide corrosion protection and improve strength through sacrificial anode action.
For assembling these AI alloy members into a heat exchanger, flux-free brazing is particularly recommended because of the various advantages brought about by not using flux. Vacuum brazing method and inert gas atmosphere brazing method are applied.

In these vacuum brazing methods and inert gas atmosphere brazing methods, the thickness of the oxide film of the member is kept thin during brazing, so the coefficient of thermal expansion between the oxide film and the base metal during brazing Destruction of the oxide film occurs due to the difference in temperature, and re-oxidation of the resulting metal substrate is prevented by a vacuum or inert gas atmosphere, allowing the solder to flow and complete brazing. If it is well controlled by the manufacturer, there is no need to carry out pre-cleaning treatment to remove the oxide film, and there is an advantage that it is only necessary to carry out pre-degreasing treatment to remove the oil that adheres during processing of the above-mentioned parts. . however,
In the above vacuum brazing method, the degree of vacuum is 10-4 to 1
Since it requires a high vacuum of 0-kiorr and high-temperature heating for a relatively long time, if the above-mentioned degreasing pretreatment or special refining pretreatment is performed as necessary, the above-mentioned parts will be free from oils, fats, moisture, etc. Even if there are residual impurities or moisture or other impurities attached during the standing period from the completion of pretreatment to the time of brazing, these impurities can be easily removed; It is impossible to avoid the evaporation of easily vaporized elements such as Zn and Mg, which are contained as components, and as a result, the corrosion resistance and strength of the parts after brazing deteriorate, as well as damage caused by the evaporated elements in the furnace. Contamination also occurred.

On the other hand, in the above-mentioned inert gas atmosphere brazing method, since the furnace atmosphere is composed of an inert gas at normal pressure or above normal pressure, it is possible to suppress the evaporation of Zn and Mg from the above-mentioned members. However, impurities that remain during pretreatment such as degreasing of the above-mentioned parts, or impurities that adhere to the parts during the period of storage before brazing, cannot be completely removed unless the furnace temperature reaches a considerably high temperature. Even if it can be removed from the component, it may still be mixed in the fresh inert gas atmosphere and adhere to the component again, causing coloring, and furthermore, it may require the use of a large amount of expensive inert gas. There was a problem. From the above-mentioned point of view, the present inventors have investigated the problem of impurities remaining during pretreatment such as degreasing of Kawa alloy members to be brazed (hereinafter referred to as brazing materials) and during the storage period before brazing. Fluxless brazing is performed with the aim of completely removing adhering impurities, as well as preventing the evaporation of Zn and Mg, which are included as alloying ingredients in order to provide anticorrosion effects and improve strength through sacrificial anode action, during brazing. As a result of research, {a'
Considering the vapor pressure of easily vaporized elements contained as alloy components in the above-mentioned parts to be brazed, for example, Zn
000 is about 10-4orr, 350q○ is about 10-2t
orr and has a vapor pressure of about 10-1ton at 400oo, the degree of vacuum in the heating atmosphere is 10-2 to 10
-3ton up to 3000C, same 10-1 to 10
0 ton, even if heated to 40,000 ton, the evaporation loss of Zn from the part to be brazed is extremely small, and the same is true for Mg. Therefore, in the process of heating the part to be brazed to the brazing temperature. If the initial stage is made into a reduced pressure atmosphere in relation to the heating temperature, Z contained as an alloying component in the member to be brazed can be reduced.
Impurities such as oil and moisture adhering to the brazing material can be completely removed with very little evaporation of n, Mg, etc.

'b} During the heating process up to the brazing temperature, as the temperature rises, inert gas is introduced into the brazing furnace one after another to bring the pressure inside the furnace to normal pressure or above normal pressure, which is the atmospheric pressure during brazing. If the temperature is gradually increased, complete flux-free brazing can be performed with extremely low evaporation of Zn, Mg, etc. contained as alloy components in the member to be brazed.

The findings shown in {a- and [b}] have been obtained above.

The present invention has been made based on the above findings, and is a method for brazing parts to be brazed containing easily vaporized elements such as Zn and Mg as alloy components by a fluxless brazing method. In the heating process, impurities adhering to the member are first removed by setting the initial heating stage to a reduced pressure atmosphere (a reduced pressure atmosphere with a vacuum degree of 10 - 2 to 10 orr without the need for a diffusion pump is sufficient). , upon subsequent heating to brazing temperature,
Inert gas is successively introduced as the furnace temperature rises so that the furnace pressure reaches the brazing atmosphere pressure, which is normal pressure or above normal pressure, when the furnace temperature reaches the brazing temperature. By gradually increasing the temperature, the evaporation of Zn and Mg from the member during the subsequent heating process to the brazing temperature is suppressed, and the temperature inside the furnace is made uniform. Next, the flux-less brazing method of the present invention will be explained using examples.

Example 1 In this example, AA3105 material (
AI-1 on both sides of AI-0.5%Mn-0.5%Mg)
A plating sheet made of brazing filler metal with a composition of 0%Sj-2%Zn-0.5%Mg is used, and this fin member is made of AAI070 material (99.7%A
The case of manufacturing a capacitor by brazing the tube part I) will be explained.

Note that, prior to brazing, the above-mentioned members to be brazed were subjected to a pre-degreasing treatment using vapor of a chlorinated hydrocarbon solvent such as perchloroethylene. First, as shown in Fig. 1, A
The above-mentioned parts to be brazed were placed in a bag in Chamber B of a brazing furnace, which consists of a chamber and an adjacent chamber B equipped with a heating device and lined with a heat insulating material, and chamber A was heated for about 10 minutes. It was evacuated to a vacuum degree of 3 rr.

Next, in the process of heating the inside of Furnace A to 300°C, argon gas with a fog point of -60 oo or less and an oxygen concentration of 2 skins or less was successively introduced, and when the temperature inside the furnace reached 300 oo, a vacuum of 10-ltorr was applied. The amount of argon gas introduced was controlled so that the In this case, the atmosphere in the brazing furnace preferably satisfies the conditions of a dew point of -5000 or less and an oxygen concentration of 5 or less.In addition to argon gas, the inert gas introduced into the furnace is nitrogen gas or nitrogen gas. A mixture of 1 to 6% by volume of hydrogen can be used. On the other hand, chamber B was also evacuated in advance, and heated while introducing inert gas in the same way as chamber A.
o, adjust the furnace pressure to 10-1 rr.

In this way, when the pressure in chamber A reaches 101 rr, which is the same as the pressure in chamber B, the doors of both chambers are raised, the material to be brazed is transferred from chamber A to chamber B, and then both lids are removed. Close the door and gradually increase the temperature inside the furnace while gradually introducing the inert gas into chamber B, so that the pressure inside the furnace reaches 800 tons when the temperature inside the furnace rises to 620 oo, which is the brazing temperature. did. In this way, the temperature of the brazing furnace is 6
When the temperature reached 2000, the heating was stopped and the pressure reduction of the atmosphere in the furnace was started, so that the atmosphere in the furnace was set at rr of 10-1 when solidification of the brazing material was completed. Next, the doors of both chambers were raised, the brazed condenser was transferred from chamber B to chamber A, the doors of both chambers were closed, and the condenser was taken out from chamber A. In the resulting capacitor,
The brazing was completed completely, showing an excellent brazing condition, and the Zn content of the fin member was 1.6%.
Even though the Zn content before brazing is 2.0%, the Zn residual rate is extremely high (80%).
It was something.

On the other hand, for the purpose of comparison, when capacitors were manufactured by conventional vacuum brazing and conventional inert gas atmosphere brazing of the above-mentioned members, the vacuum brazing showed an excellent brazing state, but The Zn content of the fin member is 0, and in the inert gas atmosphere brazing,
Shows excellent brazing condition and Zn content is 1.7
%, indicating a high residual rate, but the surface of the capacitor was slightly colored.

Example 2 In this example, AA3003 material (Yamaichi 1.2% Mn) was coated with AA4104 material (AI-9.5% Mn) as a pipe member.
A plasing pipe made of a brazing material (Si-1.9Mg-0.1%Bi) is used, and this pipe member has a composition of 1.0%Mn-1.5%Zn. A case will be described in which a capacitor is manufactured by brazing fin members.

No, each member was subjected to degreasing pretreatment in the same manner as in Example 1. First, as shown in Figure 2, there is a room A equipped with a heating device and a heat reflector, a room B adjacent to this equipped with a heating device and lined with a heat insulating material, and a room B. In a brazing furnace consisting of a heating device and a chamber C equipped with a heat reflecting plate, the parts to be brazed are placed in a bag in chamber A, the pressure inside the furnace is reduced to 10-3 tons, and the inside of the furnace is The temperature was heated to 260:00.

In this way, the temperature inside the furnace in chamber A is 260℃, and the pressure inside the furnace is 1
When the rr of 0-3 was reached, the brazed portion was transferred from room A to room B, which had been adjusted to the same temperature and pressure in advance, and the same temperature and pressure as used in Example 1 was placed in room B. While gradually introducing inert gas, the temperature inside the furnace is gradually increased.
When the temperature in the furnace rose to 620 pm, which is the brazing temperature, the atmospheric pressure in the furnace was set to 80 mbn. Next, the heating in chamber B is stopped, and when the solidification of the brazing material is completed, the condenser after being brazed is transferred to chamber C, where the pressure inside the furnace has been adjusted to 80 mm. The condenser was taken out from chamber C when the atmospheric pressure was brought to atmospheric pressure. In the capacitor obtained as a result, the brazing was completed completely and exhibited an excellent brazing condition, and the fin member contained 1.3% Zn.
The content is shown.

Considering that the Zn content of the fin member before brazing is 1.5%, the Zn residual rate is extremely high (
approximately 87%). On the other hand, for the purpose of comparison, when the capacitor was roughly assembled by the conventional vacuum brazing method as in Example 1, an excellent brazed state was obtained, but the Zn content in the fin member was 0. The Zn residual rate decreased sharply to .5%, indicating an extremely low Zn residual rate.

Similarly, in the case of the conventional inert gas atmosphere brazing method, the surface of the capacitor was considerably colored as in Example 1. However, the Zn content after brazing in the fin member was 1.4%, indicating a high Z-cape residual rate. Example 3 In this example, a plating sheet made of AA3003 material with brazing filler metal of 4104 material clad on the outer surface of AA3003 material is used as the cup member. )
A case will be explained in which a draw cup oil cooler is manufactured by brazing fin materials.

In addition, in this embodiment, as shown in FIG. 3, between the A room and the C room, each equipped with a heating device and a heat reflection plate, the B room and the B room each have a heating device and are lined with a heat insulating material. A brazing furnace consisting of a 'chamber' and a 'B'' chamber arranged in series was used.

First, put the soldered brazing material into room A and the vacuum level is 10-
After reducing the pressure inside the furnace to 30 rr, the same inert gas used in Example 1 was introduced and the pressure was increased to 10-ltom.

In this way, when the furnace atmospheric pressure in chamber A reaches 10-1 rr, the furnace atmosphere pressure is adjusted to 10-1 rr in advance and the furnace atmosphere is transferred to chamber B, which is heated to an internal furnace temperature of 30,000 rr. The parts to be brazed were transferred, and the inert gas was introduced into chamber B to increase the atmospheric pressure in the furnace to 1000 rr. Next, when the furnace atmosphere in chamber B reaches 1 plate orr, the brazing material is transferred to chamber B', where the furnace atmosphere pressure is adjusted to 100 rr and the furnace temperature is heated to 45,000 rr. Then, inert gas was introduced into the B' chamber of the same machine to increase the pressure of the furnace atmosphere to 80 mm, and then the furnace atmosphere pressure was increased to 80 mm. The parts to be brazed are transferred to chamber B'' where the temperature inside the furnace is heated to 62 mm, which is the brazing temperature, and the atmospheric pressure inside the furnace is finally raised to 80 mm.
The mixture was transferred to chamber C, which had been adjusted to a temperature of 0.5 mm, and the brazed draw cup oil cooler was taken out when the atmospheric pressure inside the furnace in chamber C was reduced to atmospheric pressure. The resulting cooler exhibited excellent brazing conditions similar to those in Examples 1 and 2.

As described above, according to the present invention, when performing fluxless brazing of N alloy members containing easily vaporized elements such as Zn and Mg as alloy components, complete brazing can be achieved with the evaporation of Zn and Mg being prevented as much as possible. Since the brazed product can be brazed, it is possible to ensure the anti-corrosion effect and strength due to the sacrificial anode action, which is the purpose of the inclusion of the above-mentioned elements, and to completely prevent impurities such as oil and moisture from adhering to the above-mentioned components. Since it can be removed, the surface quality of the product after brazing is very good, and there is no coloring phenomenon, which is an extremely effective industrial effect.

[Brief explanation of drawings]

FIG. 1, FIG. 2, and FIG. 3 are schematic illustrations of a brazing furnace used in an embodiment of the present invention. In the drawings, A, C...chambers equipped with a heating device and a heat reflector, B, B', B''...chambers equipped with a heating device and lined with a heat insulating material. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. In a flux-free brazing method for Al alloy members containing elements that are easily vaporized during brazing as alloy components, first, the initial heating stage in the heating process for brazing is performed in a reduced pressure atmosphere, so that the member is heated in a reduced pressure atmosphere. Adhering impurities are removed by electrification, and during subsequent heating to the brazing temperature, inert gas is introduced successively to gradually increase the pressure in the furnace, thereby preventing the evaporation of easily vaporized elements from the member. A flux-free brazing method for Al alloy members containing elements that are easily vaporized during brazing as alloy components, characterized in that the brazing is finally performed at normal pressure or an atmospheric pressure in the furnace above normal pressure. .