JPH02115336A - Aluminum alloy sheet for brazing excellent in drooping resistance and sacrificial anode effect and its production - Google Patents

Abstract

PURPOSE:To improve the sacrificial anode property and drooping resistance of the title sheet by adding specific amounts of Si at the time of adding In and Zn improving a sacrificial anode effect to an Al-Nn alloy. CONSTITUTION:This Al alloy sheet has a composition consisting of, by weight, 0.8-1.3% Mn, 0.2-0.7% Si, 0.04-0.1% In and/or 0.1-2.0% Zn, and the balance Al. In order to manufacture the above sheet metal, an ingot of an Al alloy with the above composition is hot-rolled at about 350-450 deg.C, without being subjected to homogenizing treatment, and is then subjected to a single process annealing only between primary cold rolling and secondary cold rolling at about 350-420 deg.C and further to secondary cold rolling at 20-40% draft. At this time, Si is formed into fine Al-Mn-Si-type precipitates, by which thermal conductivity is improved and the recrystallized grains of the sheet metal at the time of brazing heating are coarsened. As a result, the sheet metal capable of increasing strength at high temp. and inhibiting the corrosion of brazing filler metal and, further, excellent also in drooping resistance can be obtained.

Description

[Detailed Description of the Invention] Industrial Application Field This invention is used as a fin material for aluminum heat exchangers such as automobile radiators, car cooler condensers, and evaporators, either alone or as a core material of plating sheets. The present invention relates to an aluminum alloy thin plate for brazing and a method for manufacturing the same, and more particularly to an aluminum alloy thin plate for brazing that has excellent sagging resistance during brazing heat and a sacrificial anode effect as a brazing agent, and a method for manufacturing the same.

BACKGROUND ART Conventionally, when a heat exchanger such as the one described above is manufactured by using a wax wire, an AΩ-Mn alloy thin plate is used as a fin material, or AΩ-5 is used as a core material on one or both sides of the thin plate.
A plating sheet clad with an i-based alloy brazing material is used, and the fin material and the tube material are joined by brazing.

By the way, with the demand for weight reduction and cost reduction of heat exchangers, it is required to make the thickness of the fin material as thin as possible. Deformation such as buckling is likely to occur at high temperatures during additional heating. Therefore, in order to reduce the thickness of the fin material, it is essential to improve the sagging resistance of the fin material without deteriorating its formability or the like.

On the other hand, in order to reduce the weight of heat exchangers, there is a demand for thinner not only fin materials but also tube materials. It is also required to have an anodic effect. Under these circumstances, there is an increasing demand for fin materials that are excellent in both droop resistance and sacrificial anode effect.

In order to improve the sagging resistance, it is necessary to increase the size of the recrystallized grains formed in the thin plate of fin material during brazing heating. The reason for this is to improve high temperature strength by increasing the recrystallized grain size. Furthermore, during heating, the molten filler metal enters and erodes the inside of the thin plate through the grain boundaries of the thin fin plate, so if the crystal grain size is small, the amount of erosion of the filler metal increases, resulting in poor sag resistance. This is because deterioration occurs, and conversely, if the recrystallized grain size is large, the amount of erosion of the brazing filler metal will be reduced. On the other hand, in order to improve the sacrificial anode effect, it is possible to add In, Zn, etc.

Problem to be solved by the invention However, AΩ-M, which has been conventionally used as a fin material,
N-alloy thin plates generally have poor sagging resistance, and
Addition of Zn had the disadvantage that the sagging resistance further deteriorated.

The present invention has been made in view of the above technical background, and aims to provide an aluminum alloy thin plate for brazing that is excellent in both droop resistance and sacrificial anode effect, and a method for manufacturing the same.

Means for Solving the Problems In order to achieve the above object, the inventor conducted repeated experiments and research, and found that although the addition of In5Zn can exhibit an excellent sacrificial anode effect, The present invention has been completed by discovering an alloy composition and manufacturing method that can increase the recrystallized grain size of a thin plate to increase high-temperature strength, suppress brazing filler metal corrosion, and provide excellent sagging resistance. It is.

That is, the aluminum alloy thin plate for brazing having excellent sagging resistance and sacrificial anode effect according to the present invention has Mn: 0.8.
~1.3wt%, Si: 0.2~0°7vt%, further In: 0.04~0°1wt%, Zn
: Contains 0.1 to 2.0 wt% of one or two types,
It is characterized in that the remainder consists of aluminum and unavoidable impurities. Further, the method for manufacturing an aluminum alloy thin plate for brazing having excellent sagging resistance and sacrificial anode effect according to the present invention includes Mn: 0.8 to 1. 3wt%, Si: 0.2~
Using an aluminum alloy containing 0.7vt% and the remainder consisting of aluminum and unavoidable impurities, the aluminum alloy ingot was heated at 350 to 450°C without homogenization treatment.
After hot rolling at a temperature of
The secondary cold rolling is carried out at a temperature of 20 to 40%.
It is characterized by being carried out in

First, the significance of adding each element in the thin plate and the reason for limitation will be explained.

Mn improves the room temperature strength, and also acts with AΩ and Si, which will be described later, to form fine precipitates of the Afl-Mn-Si system, and these precipitates retard recrystallization. As a result, the recrystallized grains become coarser and the sagging resistance is improved. However, if it is less than 0.8vt%, the effect is small, and conversely, 1.
If it exceeds 3 wt%, coarse precipitates are likely to be formed. These coarse precipitates not only deteriorate formability, but also serve as nuclei for recrystallized grains, making the recrystallized grains finer, leading to a decrease in high-temperature strength and erosion of the brazing filler metal, leading to deterioration in sagging resistance.

St becomes Aρ-Mn-St-based fine precipitates, which has the effect of improving thermal conductivity and coarsening recrystallized grains. But 0. If it is less than 2 wt%, the effect will be small, and if it exceeds 0.7% wt%, the precipitates will become coarse and coarsening of the recrystallized grains cannot be expected.

In5Zn makes the electric potential of the thin plate less base than the other material to be brazed, for example, when the thin plate is used as the inner material of a heat exchanger, the tube of the heat exchanger, and gives the fin material a sacrificial anode effect to protect the tube from corrosion. It brings about the effect of In terms of such effects.

Both Zn are equivalent, and it is sufficient to contain either one of them. However, I n : less than 0.04vt%, Z
If n: less than 0.1 wt%, the above effect is poor, and on the contrary, In
to, 1 wt%, and Zn: exceeding 2.0 wt%, the sagging resistance deteriorates.

In addition to the above-mentioned essential additive elements, Zr and Cr may be included as optional additive elements if necessary.

Zr and Cr have the effect of improving fin formability and droop resistance. In terms of such effects, both elements are equivalent, and it is sufficient to contain 18 of them. However, if the total content is less than 0.04vt%, the above effects will be poor,
On the other hand, if it exceeds 0.12 vt%, coarse precipitates will be produced and recrystallized grains will become fine.

In addition to the above elements, F e s CU sM as an impurity
The inclusion of elements such as g, Cr5Zn, and Ti is allowed. Among these, Fe forms coarse precipitates of the Aρ-Fe system and the A[-Mn-Fe system, which serve as nuclei for recrystallization. This not only makes the recrystallized grains finer and lowers the high-temperature strength, but also causes erosion of the thin plate of the filler metal during brazing heating, so it is best to reduce its content as much as possible, preferably 0.3
It is best to limit the content to wt% or less.

In addition, since Cu has the effect of increasing the potential of the thin plate and reducing the effect of adding In and Zn, it is also best to reduce its content as much as possible, preferably regulating the content to 0.05vt% or less. It's good.

Next, a manufacturing method according to the present invention will be explained as the most preferred method for manufacturing an aluminum alloy thin plate having the above composition. The basic idea of this manufacturing method is to suppress the formation of coarse Mn precipitates that become recrystallization nuclei by applying as little heat as possible to the thin plate until brazing, and to control the final rolling reduction within an appropriate range. The goal is to control the driving force for recrystallization.

Furthermore, minimizing the application of heat to the thin plate until it is brazed will also prevent In, Zn from diffusing into the brazing material layer when used as the core material of a plating sheet.

Specifically, the details are as follows.

That is, the production method according to the conventional method involves melting and casting an aluminum alloy having the above composition, then subjecting the obtained ingot to homogenization treatment, and then performing the steps of hot rolling, intermediate annealing, and cold rolling. However, in the present invention, hot rolling is performed without performing homogenization treatment after melting and casting. The reason why the homogenization process is omitted in this way is that when the homogenization process is performed, Mn becomes Afl-M.
This is because they are formed as coarse precipitates of n-type and AΩ-M n -Fe-type, and serve as nuclei for recrystallization to refine the recrystallized grains, so this is avoided. In addition, in order to avoid the formation of coarse precipitates as much as possible during hot rolling,
It must be carried out at a temperature range of 350 to 450°C to prevent diffusion of n.

Next, cold rolling is performed by omitting intermediate annealing after hot rolling and before cold rolling. In addition, only intermediate annealing is performed at a temperature of 350 to 420° C. only during this cold rolling, that is, between the first cold rolling and the second cold rolling. The reason for omitting the intermediate annealing after hot rolling and before cold rolling is to suppress the formation of coarse precipitates as mentioned above. Furthermore, the intermediate annealing performed between the first cold rolling and the second cold rolling is performed for the purpose of releasing strain and making rolling easier, and for the purpose of controlling the rolling reduction rate of the second rolling. The temperature of this intermediate annealing is 35
The reason why it is specified as 0 to 420°C is that below 350°C, the above effect is poor, and on the other hand, when it exceeds 420°C, coarse precipitates are formed, recrystallized grains become finer, and the sagging resistance deteriorates. It is. Moreover, the above-mentioned secondary cold rolling has a rolling reduction ratio of 2
It shall be carried out at 0 to 40%. The reason why the rolling reduction rate is specified above is that if it is less than 20%, recrystallization will not occur and the crystal grains will remain unstable and the brazing metal will erode into the thin plate along the sub-grain boundaries. . On the other hand, if the rolling reduction exceeds 40%, the driving force for recrystallization is too large and the crystal grains become finer.
This is because the amount of erosion of the brazing filler metal increases. The final wall thickness is obtained by this secondary cold rolling. Note that the conditions for the primary cold rolling are not particularly limited, and the conditions for normal cold rolling may be adopted. Further, when a thin plate is used as the core material of an aluminum plating sheet, one or both sides of the thin plate may be clad with a brazing metal layer in a hot rolling process.

As described in detail of the invention, the aluminum alloy thin plate according to claim 1 has excellent sagging resistance during brazing heat, and therefore the thin plate can be made thinner and can be used alone as a fin material of a heat exchanger. It is also suitable for use as a core material for plating sheets. Moreover, since it has an excellent sacrificial anode effect, it can compensate for the deterioration in corrosion resistance that occurs when the tube material of a heat exchanger is made thinner, and can greatly contribute to reducing the weight and cost of products.

Further, by using the manufacturing method of claim 2, it is possible to provide an aluminum alloy thin plate having even better sagging resistance and sacrificial anode effect.

Examples (Example 1) Placing sheets having core materials made of various aluminum alloy thin plates having compositions shown in Table 1 below were manufactured. The production followed the following steps. That is, each aluminum alloy ingot is face-sided without being homogenized after melting and casting, then both sides are clad with a brazing filler metal made of AΩSt alloy at a ratio of 15%, and then hot-rolled to a wall thickness of 3.5%. It was rolled to 2rrrm.

Next, after first cold rolling to a wall thickness of 0.2# without performing intermediate annealing between hot rolling and cold rolling, 370X
Intermediate annealing was performed for 1 hour, and secondary cold rolling was performed to a thickness of 0.13 #, which was used as the final thickness. Here, the rolling reduction ratio of the core material in the secondary cold rolling was 35%.

[Margin below] Each aluminum plating sheet obtained above was subjected to a sagging resistance test and a corrosion resistance test, and fin height 20m x width 100++m x pitch 20IllII+
The formability of this material was investigated when it was processed into corrugated louver fins. Dragging resistance test is width 20 x length 80/III
Of the test piece cut to size II, a portion up to 35 m from one end in the length direction was held horizontally, and the remaining 45 mIn portion was left unsupported, and in this state, it was placed in a vacuum for 6 minutes.
The corrosion resistance test was carried out by measuring the amount of droop of the free end of the protruding part of the test piece when it was held for 5 minutes at 05"CX. In addition, the corrosion resistance test was performed by brazing a tube made of A1100 alloy and soaking it in salt water based on JIS 22371. A spray test (SST) was conducted to determine the time n1 until the tube leaked.

In addition, those with good moldability and those with poor Q1 were expressed as x.

The results are shown in Table 2 below.

[See Table 2 below (Example 2) Aluminum alloys having the compositions indicated by alloy symbols A to G in Table 1 of Example 1 were used as materials and were melted and cast to produce aluminum alloy ingots. These ingots were then face-sided with or without homogenization treatment. Next, both sides were clad with a brazing filler metal made of An-5t alloy at a ratio of 15%, and hot rolling was performed to a thickness of 3.2. Next, after performing primary cold rolling to a thickness of 0.2 mm with or without intermediate annealing, various aluminum plating sheets are produced by sequentially performing intermediate annealing and secondary cold rolling. did. Table 3 summarizes the presence or absence of each step and the processing conditions.

The aluminum plating sheet obtained above was subjected to a sagging resistance test and a corrosion resistance test, and its formability was also investigated. The sagging resistance test, corrosion resistance test, and moldability investigation were all conducted under the same conditions as in Example 1. The results are also shown in Table 3.

[Margins below] From the results of Examples 1 and 2 above, it can be seen that the aluminum alloy thin plate for brazing according to the present invention and the aluminum alloy thin plate for brazing manufactured by the present invention have good droop resistance,
It was confirmed that the sacrificial anode effect was excellent and the moldability was also excellent.

Claims (2)

[Claims] (1) Mn: 0.8-1.3wt%, Si: 0.2-0
．． Contains 7 wt%, and further In: 0.04 to 0.1 w
t%, Zn: 0.1 to 2.0 wt% or two, and the balance consists of aluminum and unavoidable impurities, and has excellent sagging resistance and sacrificial anode effect. . (2) Mn: 0.8-1.3wt%, Si: 0.2-0
．． Contains 7 wt%, and further In: 0.04 to 0.1 w
t%, Zn: 0.1 to 2.0 wt%, and the balance is aluminum and unavoidable impurities. After hot rolling at a temperature of 450°C, intermediate annealing is performed once only between the first cold rolling and the second cold rolling at a temperature of 350 to 420°C,
A method for producing an aluminum alloy thin plate for brazing having excellent sagging resistance and sacrificial anode effect, characterized in that the secondary cold rolling is performed at a rolling reduction ratio of 20 to 40%.