JPH03211260A - Manufacture of aluminum thin sheet for soldering excellent in drooping resistance - Google Patents

Abstract

PURPOSE:To obtain an aluminum thin sheet for soldering excellent in drooping resistance, at the time of successively executing hot and cold rolling to the ingot of Al having specified value or above of purity, by executing process annealing at a specified temp. in the process of the cold rolling and specifying the draft in final cold rolling. CONSTITUTION:The ingot of Al having >=90% purity is hot-rolled into a sheet having a prescribed thickness, is thereafter cold rolled into a thin sheet, is thereafter subjected to process annealing at 250 to 450 deg.C and is successively subjected to final cold rolling at 20 to 70% draft. By this method, the size of the recrystallized grains formed in the stage of heating for soldering increases and not only high temp. strength but also drooping resistance can be improved. As for the process annealing temp., in the case of less than the lower limit, recrystallization does not occur as well as its high temp. strength is made weak, and in the case of more than the upper limit, precipitates are coarsened and are formed into the nucleus of the recrystallized ones to refine the recrystallized grains. As for the draft of the final cold rolling, in the case of less than the lower limit, recrystallization does not occur in the stage of heating for soldering, and in the case of more than the upper limit, the driving force for recrystallization is made excessive to refine the recrystallized grains.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a solder thin plate that is soldered to a tube or the like as a fin material for an aluminum heat exchanger such as an automobile radiator, a car cooler condenser, or an evaporator. In particular, the present invention relates to a method of manufacturing an aluminum thin plate that has excellent sagging resistance during soldering heat application.

BACKGROUND OF THE INVENTION For example, an aluminum heat exchanger as described above is constructed by joining a tube for refrigerant flow and thin plate-like fins for improving heat transfer efficiency. Brazing is a method of joining such tubes and fins.
is often used, but in cases where workability is required, soldering may be used.

Problems to be Solved by the Invention By the way, the current wall thickness of the above-mentioned fin material is 0.13 to 0.13.
Although those with a thickness of about 16 am are often used, there is a trend toward thinner walls due to recent demands for light weight and low cost. However, when the fin material is made thinner, the sag resistance deteriorates, and deformation such as buckling is likely to occur during heating during brazing or soldering. Therefore, in order to further reduce the thickness of the fin material, etc., it is essential to improve the sagging resistance.

In response to these demands, various attempts have been made to improve the sagging resistance of fin materials for brazing by improving the composition and manufacturing process. The reality is that very little has been done.

This invention was made in view of such circumstances, and
The purpose is to improve the droop resistance of thin plates such as fin materials used for soldering.

Means for Solving the Problems To achieve the above object, the present invention uses pure aluminum with an AQ purity of 90% or more, and when hot rolling and cold rolling are sequentially performed on an ingot of the aluminum, cold rolling is performed. The summary is a method for producing a solder-used aluminum thin plate with excellent droop resistance, which is characterized by performing intermediate annealing at a temperature of 250 to 450 ° C. and final cold rolling at a reduction rate of 20 to 70%. It is something to do.

Regarding the composition of the thin plate, pure aluminum with an AΩ purity of 90% or more is used because pure aluminum has excellent thermal conductivity, good formability, and is inexpensive. Such pure aluminum is defined as 1000 series, and specifically, for example, A1100, A1050, etc. can be used.

Next, to explain the manufacturing method, the basic idea of this invention is to increase the recrystallized grain size formed during soldering heat to improve high-temperature strength and, by extension, sag resistance. It is. Specifically, it is as follows. In other words, the conventional manufacturing method for thin plates involves melting and casting aluminum, subjecting the resulting ingot to homogenization treatment as necessary, and then hot rolling, cold rolling, intermediate annealing, and final cooling. Inter-rolling is performed sequentially. Therefore, in this invention, intermediate annealing during cold rolling is performed at 250 to 450°C.
The test shall be carried out at a temperature of This intermediate annealing is performed for the purpose of releasing strain and making rolling easier.
At temperatures below 0° C., recrystallization does not occur, so not only the above object cannot be achieved, but also the high temperature strength becomes weak, and furthermore, the sagging resistance cannot be improved.

On the other hand, at temperatures above 450° C., the precipitates become coarse and serve as nuclei for recrystallization, resulting in finer recrystallized grains, resulting in a decrease in high-temperature strength and, ultimately, in sagging resistance. Particularly preferable intermediate annealing is about 300 to 400°C. The number of times of this intermediate annealing is not particularly limited,
It may be performed once or twice or more. Further, in this invention, the final cold rolling is performed at a rolling reduction ratio of 20 to 70%. The reason why the rolling reduction ratio is specified above is because if it is less than 20%, recrystallization does not occur during soldering heat and the crystal grains remain unstable, and the effect of improving high temperature strength and sagging resistance cannot be obtained. It is. On the other hand, since the soldering temperature is lower than the brazing temperature, a reduction rate of up to 70% is allowed, but if it exceeds 70%, the driving force for recrystallization becomes too large and the recrystallized grains become fine at the soldering temperature. , which impairs high-temperature strength and sagging resistance. Particularly preferable rolling reduction ratio is 25 to 50%.
That's about it. This final cold rolling obtains the final wall thickness.

Note that conditions for cold rolling other than hot rolling and final cold rolling are not particularly limited, and conditions for normal hot rolling and cold rolling may be adopted.

Example Pure aluminum having the composition shown in Table 1 below was melted and cast to produce an ingot. Next, this ingot was hot rolled at 480° C. on the back side to produce a plurality of plates with a wall thickness of 35 mm. next,
After cold rolling each plate to the thickness shown in Table 2, intermediate annealing was performed at the temperature also shown in Table 2, followed by final cold rolling to form aluminum thin sheets with a final thickness of 0.15as+. Obtained.

Each of the aluminum thin plates produced as described above was subjected to a drooping resistance test, and
The moldability when processed into corrugated louver fins with a pitch of 10 am was investigated. The sagging resistance test was performed using width 2011
A test piece cut into a size II x 100 length is held horizontally from one end to 30 mm, and the remaining 7 mm is held horizontally.
The test was carried out by measuring the amount of droop of the free end of the protruding portion of the test piece when the test piece was protruded in an unsupported state and heated at 500° C. for 5 minutes.

In addition, good moldability was represented by ◯, and poor moldability was represented by ×.

The results are also shown in Table 2.

[Margin below] As can be seen from the results in Table 2, it was confirmed that the thin aluminum plate for soldering produced according to the present invention had a small amount of sagging, and was therefore excellent in sagging resistance. Furthermore, there were no problems with moldability.

As described in detail, according to the present invention, it is possible to provide a thin aluminum plate for soldering that has excellent droop resistance. Therefore,
This makes it possible for solders to reduce the thickness of the fin materials of aluminum heat exchangers, meeting the demands for lighter weight and lower cost.

that's all

Claims (1)

[Claims] Using pure aluminum with an Al purity of 90% or more, when hot rolling and cold rolling are sequentially performed on the aluminum ingot, intermediate annealing is performed at a temperature of 250 to 450 ° C. during the cold rolling, And the final cold rolling is done at a reduction rate of 20 to 70.
%.A method for manufacturing aluminum thin plates for soldering with excellent droop resistance.