JPH0570541B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention is characterized by the fact that the surface is covered with wax.
The present invention relates to a method of brazing an Al or Al alloy member, such as a brazing sheet or a member obtained by forming a brazing sheet, and an Al or Al alloy member. [Prior Art] In general, Al and Al alloys are light, have excellent thermal conductivity, and have a certain degree of corrosion resistance, so they have traditionally been used as materials for heat exchangers such as automobile radiators and air conditioners. These heat exchangers are widely used as, for example, Al-
The core material is Mn diameter alloy, and one side of this core material is Al-Si.
A fin material made of a brazing sheet made of a brazing sheet made of a brazing alloy and a pipe material of pure Al or Al-Mn alloy are combined, and this combination is brazed in a vacuum or in an inert gas without flux. It is manufactured by attaching or brazing with flux in a low pressure atmosphere. [Problems to be solved by the invention] In such brazing, in the case of the member to be brazed, that is, the above heat exchanger,
The fin material and tube material made of brazing sheets are heated to a brazing temperature of around 600℃ where the wax melts, but during this temperature rise, the brazing sheet wax penetrates into the core material, causing brazing. Not only does the high-temperature strength of the fin material made of sheets drop significantly, causing deformation such as so-called "sagging", but also the wax that has entered the core material no longer contributes to the bonding of the parts. In order to impart high strength to Al or Al alloy members whose surfaces are clad with solder, strong processing is required to improve brazing properties. For example, in order to give high strength to the fin material corrugated in the heat exchanger, a processing rate of 50, for example, is applied.
% or more, the problem becomes particularly noticeable. [Findings based on research] Therefore, the inventors of the present invention have conducted various studies to solve the above problems, and have found that (1) The penetration of solder into the core material is caused by the wax passing through the grain boundaries of the core material. (2) The flow of the core material crystal grains in the rolling direction during solder melting is determined by the plate thickness. When the crystal grains are significantly larger than the length in the direction, that is, when the shape of the crystal grains becomes elongated and fibrous, the depth of the wax penetrating into the core material becomes shallow, and therefore the wax penetration against the core material becomes shallow. (3) In general, when increasing the temperature of Al and ordinary Al alloy processed materials, recrystallization nuclei begin to form at temperatures above 250°C and are almost complete at 400°C. death,
Furthermore, when the temperature of the processed material exceeds 400°C, the growth of the recrystallized nuclei that have already been formed, that is, the coarsening of the crystal grains, progresses. Therefore, in general, if this heating rate is high, a large number of recrystallization nuclei are formed in the recrystallization nucleation temperature range of 250 to 400℃, and then
Grain growth occurs at temperatures exceeding 400℃, and as a result of the crystal grains growing around the many already formed crystal nuclei mutually constraining their growth, a nearly isotropic A structure is obtained as a result of aggregation of many fine crystal grains.On the other hand, if the heating rate is low, a small number of recrystallized nuclei are formed at 250 to 400℃, and then when the temperature of the workpiece exceeds 400℃, the temperature decreases. The growth of recrystallized nuclei, which extend in the rolling direction while absorbing surrounding processing energy as the steel rises, is not constrained by each other, resulting in the formation of crystal grains whose length in the rolling direction is significantly longer than that in the plate thickness direction. Therefore, when the temperature of the processed material is increased, the shape of the crystal grains formed by recrystallization is determined by the recrystallization temperature range, that is,
Processed material (core material) in the temperature range of 250-400℃
(4) The above-mentioned fibrous crystal grains are controlled by the temperature increase rate of 250 to 400℃, where recrystallization of the processed material occurs. is obtained when the temperature increase rate of the processed material is 10℃/min or less, but if this temperature increase rate exceeds 10℃/min, many crystal nuclei are formed and the shape of the crystal grains becomes isotropic. 20℃/min, which was conventionally applied when brazing Al or Al alloy parts.
We have found that at the above heating rate, almost completely isotropic fine crystal grains are formed. [Means for Solving the Problems] This invention was invented based on the above knowledge, and the Al or Al alloy member whose surface is clad with solder is bonded to the Al or Al alloy member at a brazing temperature. In the method of brazing these parts to each other by raising the temperature to The purpose is to provide a brazing method that does not cause
The method is characterized in that the temperature of the member is raised at a rate of 10°C/min or less in a temperature range of 250 to 400°C during the heating process during brazing. In this invention, the temperature range that defines the temperature increase rate during brazing is 250 to 400℃, and the temperature increase rate within that range is limited to 10℃/min or less, as is clear from the findings already mentioned. As in, Al or
The processed material made of Al alloy is heated to 250 to 400℃ during the heating process.
A recrystallization nucleus is formed between
If it is below, only a small number of grains will be formed, so during the subsequent crystal growth process in a temperature range exceeding 400℃, fibrous crystal grains are formed that are long in the rolling direction and short in the thickness direction, and have this shape. The formation of crystal grains depends exclusively on the heating rate of the workpiece in the above temperature range, and the elongated crystal grains extending in the rolling direction suppress the intrusion of solder into the workpiece. This method is based on solving the aforementioned problem, that is, the brazing failure caused by the deformation of the workpiece and the significant decrease in brazing properties that occur during brazing. [Examples and Effects Based on Examples] Next, the present invention will be explained using Examples while comparing with Comparative Examples. Zn: 1.51%, Mn:
1.01%, Zr: 0.11%, and Al + inevitable impurities:
The remainder is an Al alloy for core material having a component composition (the above weight %, the same below), Si: 9.55%,
A brazing filler metal with a component composition consisting of Mg: 1.53%, Bi: 0.05%, and Al + unavoidable impurities: the remainder.
After melting and casting an Al alloy into an ingot, it was homogenized under normal conditions. Furthermore, these
All Al alloys contain Fe as an unavoidable impurity.
0.4% or less, Si: 0.2% or less, Cu: 0.05% or less,
Mg: 0.01% or less, Cr: 0.01% or less, Mn: 0.01%
Below, Zn: 0.02% or less, Zr: 0.01% or less, Ti:
It contained 0.05% or less. Next, regarding the Al alloy ingot produced as described above, the Al alloy for the core material was hot-rolled to form a hot-rolled plate with a thickness of 8 mm, while the Al alloy for the core material was hot-rolled to a thickness of 8 mm.
For Al alloys, the same result is obtained by hot rolling:
After making a 5mm hot rolled sheet, cold rolling was performed to obtain the same:1
It was made into a cold-rolled sheet of mm. Next, the cold-rolled plates of the Al alloy for the brazing filler metal are laminated on both sides of the hot-rolled plate of the Al alloy for the core material, and the plate is made into a plate with a thickness of 3 mm by hot rolling, and then a... Heating rate:
Intermediate annealing under the conditions of 0.5℃/min, heating temperature: 380℃, holding time: 2 hours, or b...Temperature increase rate:
While performing intermediate annealing under the conditions of 50°C/sec, heating temperature: 400°C, and holding time: 5 minutes, cold rolling is performed with a final cold rolling reduction of 55% or 70%. : Many 0.16mm brazing sheets were manufactured. Next, in order to evaluate the high temperature sag resistance of each brazing sheet obtained as a result, a sagging resistance test was conducted in a vacuum. In the drooping resistance test, a specimen with dimensions of width: 30 mm x length: 130 mm was cut from the above brazing sheet, and a specimen was cut out from the brazing sheet by 100 mm from one longitudinal end of the specimen.
The remaining 30mm portion is held horizontally, and the remaining ^30mm portion is left exposed. Each specimen was heated from room temperature to 620℃ at a heating rate of ℃/min, 8℃/min, 15℃/sec, and 30℃/min, and at a heating rate of 30℃/min for all other temperature ranges. After increasing the temperature to The height was measured and the results are shown in Table 1. In addition, in order to investigate the extent to which solder contributes to the joining of brazing sheets during brazing, we corrugated the various brazing sheets mentioned above to make fin materials, and used these as fin materials on two sheets of pure aluminum (JIS 1050) with a thickness of 1 mm. ) The fin material and the Al plate are brazed by exposing them to the heat treatment in which the temperature is raised at the four temperature increase rates while being sandwiched between the plates, and maintaining the temperature at 620°C for 10 minutes during the heat treatment. death,
The state of the fillet formed by this solder between the two members was observed. In this case, the fillet formed between the fin material and the Al plate across the twill line of the fin material in contact with the Al plate has a width of 1 mm or more due to the sufficient supply of solder to the fillet portion. ○ indicates that the fillet is in good condition, and △ indicates that the width is more than 0.3 mm but less than 1 mm and the fillet is formed but is not in good condition due to insufficient solder supply. The case where the fillet was hardly formed due to the extremely small supply of fillet with a width of 0.3 mm or less was marked as x, and the results are shown in Table 1. Furthermore, the fin material after brazing in this way was cut so that the surfaces along the rolling direction and plate thickness direction were exposed, and after polishing the cut surfaces, microstructure photographs of each of these cross sections were taken. By taking photographs and counting the average number of crystal grains that intersect with a straight line of a certain length drawn along the rolling direction and the plate thickness direction on the microstructure photograph, respectively,
Regarding the recrystallized grains formed in the core material of this fin material, the average length in the rolling direction and the plate thickness direction was measured, and the state of penetration of solder into these core materials was examined to confirm that there was no penetration of wax at all. The results are shown in Table 1. The results are shown in Table 1. The results are shown in Table 1. From the results shown in Table 1, the intermediate annealing conditions during processing of the brazing sheet and the final cold rolling

[Overall effect of the invention]

As is clear from the above explanation, according to the present invention, the wax is clad with Al or
When brazing Al alloy parts, the Al or
The above-mentioned solder is suppressed from penetrating into the Al alloy member, thereby preventing deformation such as “settling” during brazing of the member, and
Since the solder remains on the surface of Al or Al alloy parts and can fully fulfill its original role of contributing to the joining between parts, it suppresses the occurrence of brazing defects in fields where such parts are brazed. death,
The industrially useful effect of improving productivity and yield can also be obtained.

Claims (1)

[Claims] 1 Al with wax cladding on the surface or
In a method of brazing an Al alloy member and an Al or Al alloy member to each other by raising the temperature to the brazing temperature, the heating temperature is 250 to 400°C during the temperature raising process during brazing. 10℃/at a temperature range of
The brazing method is characterized in that the temperature of the member is increased at a temperature increase rate of min or less.