JPS63114948A - Manufacture of aluminum alloy clad material having sacrificial layer - Google Patents

Abstract

PURPOSE:To obtain the titled Al alloy clad material showing satisfactory pitting corrosion resistance in any environment by soaking and hot rolling an Al alloy ingot contg. prescribed components, superposing the resulting cladding material on an Al (alloy) core material and subjecting the materials to hot rolling, cold rolling, process annealing and cold rolling. CONSTITUTION:An Al alloy ingot contg., by weight, 0.1-2.0% Zn, 0.01-0.05% Ti, 0.0001-0.001% B and 0.02-1.5% in total of 0.01-1.0% each of Fe and Si is soaked at 500-635 deg.C especially for 2-8hr and hot rolled or further cold rolled. The resulting cladding material is superposed on at least one side of an Al (alloy) core material. The materials are heated, integrated by hot rolling, cold rolled at 80-98% draft, process-annealed at 250-450 deg.C and cold rolled again to obtain a desired Al alloy clad material having a sacrificial layer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an aluminum alloy composite material having a sacrificial layer, in which a material with improved pitting corrosion resistance is used for the sacrificial layer. I'll go.

[Conventional technology]

Conventionally, among the parts assembled by brazing various Al alloys, such as Al alloy heat exchangers, in parts that come into direct contact with cooling water and the atmosphere and require corrosion resistance, it is necessary to sacrificially lower the material surface to a base potential. By providing an anode layer, the corrosion life of the part is extended. This anode layer usually contains about 1% Zn! -Zn-based alloys are used, and the sacrificial effect of the anode layer is due to the corrosion potential difference between the anode layer and the core material, and therefore the absolute value of the 7-n content in the anode layer is the most important factor that influences the sacrificial effect. It has been. Therefore, in the manufacturing process of the composite material with the sacrificial anode layer, most attention was paid to the Zn content in the manufacturing process of the skin material that was to become the anode layer, and no particular attention was paid to the microscopic metal structure. . The manufacturing process for the rough anode layer is JI.
S7072 (S i 10F e0.7 wt%, Cu0
．． 1wt%, MnO, 1wt%, M2O, 1wt%, Z
An ingot of an alloy with a composition equivalent to nO, 8 to 1.3 wt%, balance Al) is soaked at 400 to 500°C, then hot rolled to form a plate, which is heated together with a core material and then hot rolled. The integrated laminated material was subjected to about 95% cold rolling, then subjected to intermediate annealing, and then finished to a predetermined thickness by cold rolling.

[Problem that the invention seeks to solve]

The sacrificial anode layer of the above-mentioned Al alloy gold plate corrodes preferentially than the core material in normal atmospheric conditions and water, so the component maintains its function over a long period of time without forming through-holes due to corrosion. be able to. However, especially when exposed to a corrosive environment containing a relatively large amount of chlorine ions, some of the laminates manufactured using conventional processes will experience pitting corrosion because the corrosion of the positive 4 layer concentrates on a part of the surface. The existence of something that gives rise to form has become a problem.

[Means for solving problems]

As a result of a detailed study of Al alloy composite materials that have suffered pitting corrosion, the present inventors have found that the following points are effective in preventing pitting corrosion.

(1) By adding a small amount of Li and B to the sacrificial anode layer, ie, the skin material, the metal structure such as crystal grain size is made homogeneous and uniform.

(2) Precipitates in the material are grown by increasing the soaking temperature of the skin material ingot to a high temperature.

(3) In the process of manufacturing laminated materials using the above-mentioned skin material, the grain size of the recrystallized grains is made uniform by a combination of the intermediate annealing temperature in the process before finishing the plate to the final thickness and the cold rolling rate in the process before that.
And the crystal orientation is random.

Based on the above knowledge and as a result of further studies, the present invention has developed a method for producing an Al alloy composite material that is unlikely to cause pitting corrosion in any environment and has a sacrificial anode layer that slows the progress of pitting corrosion. Zn0.1-2.0wt%
(hereinafter wt% is abbreviated as %), l'-i0.01 to 0.0
5%, BO,0001~0,01%, and further Fe
An Al alloy ingot containing a total of 0.02 to 1.5% of Si and Fe in the range of 0.0101 to 1.0%, Si0.
After soaking for more than an hour, hot rolling or hot rolling and cold rolling is performed to obtain a skin material, which is superimposed on at least one side of a core material made of Al or Al alloy, heated and then hot rolled. It is characterized in that it is integrated, then subjected to 80 to 98% cold rolling, then subjected to intermediate annealing at 250 to 450°C, and then cold rolled.

[For production]

The reason why the composition of the sacrificial anode layer, ie, the skin material, is limited as described above in the product of the present invention is as follows.

The reason for limiting the Zn content to 0.1 to 2.0% is because the addition of Zn makes the potential of the material base and enhances the sacrificial anode effect of the skin material.If Zn is less than 0.1%, the above effect will be reduced. There are few
This is because if it exceeds 2.0%, the above effect will be saturated.

The addition of Ti acts as solidification nuclei during casting, making the ingot structure uniform and fine, and making the structure uniform after subsequent rolling and heat treatment to improve corrosion resistance.
The limit to ooi~0.05% is when l-i is 0.001
If it is less than %, the above effect will be small and the structure will become non-uniform, and this non-uniform structure will also have an adverse effect on the recrystallized structure after soaking the ingot, rough rolling and heat treatment, reducing the corrosion resistance of the material. Moreover, when the lower i exceeds 0.05%, the above effect is saturated, and the possibility that Ti is roughly aggregated to form a coarse intermetallic compound increases. Normal leather material has a thickness of 20 to 50 mm.
μm, and it is not preferable for coarse intermetallic compounds to exist therein. The purpose of adding B is to make the ingot structure uniform and fine by coexisting with Ti, and to make the metal structure after rough rolling homogeneous. ooooi~
The reason why it is limited to 0.01% is because if it is less than 0.0001%, the above effect will be small. This is necessary because if it exceeds oi%, TiB2 becomes coarse.

The purpose of adding S; and Fe is to improve the pitting corrosion resistance by precipitating them during soaking, hot rolling, or intermediate annealing of the ingot. That is, the size and orientation of recrystallized grains are determined by the step and size in which Si and Fe are precipitated during the alloy manufacturing process, and by controlling these, a material with excellent corrosion resistance can be obtained. Fe0601~1.0%, SiC
), the total content of Fe and Si is limited to 0.02 to 1.5% within the range of 0.01 to 1.0%, because if each of Fe and S) is less than 0.01%, their It becomes difficult to control recrystallized grains due to precipitates, and either Fe or Si exceeds 1.0%, or the total of both exceeds 1.0%.
If it exceeds 5%, the possibility of forming insoluble coarse intermetallic compounds increases, and these coarse intermetallic compounds do not contribute to the control of recrystallized grains, and also reduce pitting corrosion resistance.
I'm here to help.

Next, the manufacturing process of the material of the present invention will be explained.

During the soaking treatment of the Al alloy ingot, the segregated phase diffuses and disappears into the matrix, and at the same time, Fe and Sl, which are supersaturated in solid solution in the matrix during casting, precipitate. The size of the precipitated phase is determined by the temperature and time at this time. Therefore, the present inventor found that the size of the precipitated phase most effective for corrosion resistance is 0.1 to several μm. The reason why the soaking temperature was limited to 500-635°C is that at temperatures below 500°C, it is difficult for the precipitated phase to grow to a sufficient size, and when it exceeds 640°C, the risk of melting increases. It's for a reason. The reason why the soaking time is set to 1 hour or more is because precipitation does not occur sufficiently when heating for less than 1 hour. In addition, from the point of view of actual operation, the time is economical to be 2 to 8 hours, and the temperature is 580 to 620°.
C is preferable.

Next, the above-mentioned ingot is hot-rolled or hot-rolled and cold-rolled to make a skin material, and this is superimposed on one side of the core material, and if necessary, on the other side, low melting point A, l2-sr. The sheet materials are stacked together as a brazing material, heated, and then integrated by hot rolling to form a laminated material. This composite material is subjected to intermediate annealing at a temperature of 250 to 450°C, or cold rolled at a rolling rate of 80 to 98% without sieving, then intermediate annealed at a temperature of 250 to 450°C, and then cold rolled. The plate is finished to the specified thickness by inter-rolling.

In the present invention, the temperature, etc. of intermediate annealing during the production of the laminated material are specified as described above for the following reason.

First, the intermediate annealing is to recrystallize the side slopes due to the strain introduced into the material by rolling, and the annealing temperature is set at 250-4.
The reason why the temperature is limited to 50°C is because recrystallization does not occur sufficiently when the temperature is less than 250°C, and when it exceeds 450°C, there is an increased risk that the structure will become non-uniform. After integration by hot rolling, intermediate annealing can be performed if necessary before cold rolling, but the presence or absence of this annealing may slightly affect the pitting corrosion resistance of the final product depending on the interaction with the cold rolling rate. However, it is not a big difference in practice.

The purpose of rough cold rolling is to ensure that the recrystallization during intermediate annealing of the bond has a uniform grain size and random crystal orientation, and the reason why the rolling rate was limited to 80 to 98% was to Outside this range, the recrystallization orientation tends to be aligned, and in particular, multiple crystal grains with the Miller index (100) plane oriented parallel to the plate surface are generated, which tends to cause cubic pitting corrosion in the final product, resulting in poor corrosion resistance. is.

In addition, the laminated material finished to a predetermined thickness is processed into a tube by forming or electric resistance stitching depending on the part to be used, and then processed into the final product shape (part shape of a heat exchanger, etc.) by forming, etc. , and then subjected to brazing heat (approximately 800'C) to form the final product. Here, it is confirmed L2 that the non-uniformity of crystal orientation, etc. that exists in the structure before the brazing heat is promoted by the brazing heat.

〔Example〕

Next, the present invention will be explained in detail based on the first example.

Alloys having eight different compositions shown in Table 1 were produced by a semi-continuous casting method, and five core materials and one each of the other materials were used as ingots measuring 70 x 200 x 400 mm. These were first soaked on both sides with a distance of 5 m on each side, and alloys a to f were soaked under the conditions shown in Table 2. The core material was soaked at 580°C for 4 hours, and the brazing material was soaked at 500°C for 2 hours. was applied.

Thereafter, a to f and the brazing metal were hot rolled at 500°C to form a plate with a thickness of 7.5 mm, and these were made into a 60x200
A core material ingot of x200 rrm is overlaid with skin material on one side and brazing material on the other side with a crud ratio of 10%, and this is
'C was heated and then hot-rolled to form a laminate with a plate thickness of 6#.

These laminated materials were made into plates of 21 m and 0.42 m in the process shown in Table 2, and used as test materials. This test side was brazed at 600°C in a N2 atmosphere for 10
After heating for a few minutes and cooling to the lowest temperature, a corrosion test was conducted.

Corrosion test conditions were 10 ppm of copper ions added to flowing water7]0
Each test material was tested for 2,000 cycles, with one cycle consisting of holding the solution at 80°C, immersing the above test material for 8 hours, and then leaving it in the air at the lowest temperature for 16 hours. Ta.

Upon completion of the test, each sample material was ranked into the following three levels and evaluated based on the depth of the pits formed on the surface of the sample material.

Rank A: Very shallow pits occur only in the skin material.

Rank B: Many shallow pits occur in the skin material, but there is no pitting corrosion in the core material.

Rank C: There are deep pits that reach inside the core material, and the consumption of the skin material is large due to corrosion.

The evaluation results of the corrosion test are also listed in Table 2.

As is clear from Tables 1 and 2, it can be seen that the laminated materials (N0.1 to No.5) produced by the method of the present invention have excellent corrosion resistance. On the other hand, the corrosion resistance of composite materials (N0.6 to N0.8) using comparative skin materials whose alloy compositions deviate from the specifications of the present invention is inferior to that of composite V materials made by the method of the present invention, and is generally not as good as that of the composite skin materials of the present invention. (N0.9 to N(110)
It can be seen that the corrosion resistance is significantly inferior.

In this example, the brazing heat was carried out in an N2 atmosphere, but the brazing conditions of this composite material are not particularly restricted, and the specified performance can be achieved even under any brazing conditions, such as in a vacuum or with or without flux. I'll take what I can get. Further, as for the core material, any alloy can be selected depending on the final purpose as long as it has a higher potential than the skin material. The brazing filler metal on the opposite side of the sacrificial anode layer skin material can also be used with or without cladding, if necessary.

〔Effect of the invention〕

The aluminum alloy composite material having a sacrificial anode layer according to the present invention has good pitting corrosion resistance under any environment, and therefore products using this composite material have a long corrosion life. It is necessary.

Claims (2)

[Claims] (1) Zn0.1~2.0wt%, Ti0.001~
0.05wt%, B0.0001~0.01wt%, further Fe0.01~1.0wt%, Si0.01~
A total of 0.0 of Si and Fe within the range of 1.0 wt%
After subjecting an Al alloy ingot containing 2 to 1.5 wt% and the remainder Al to soaking treatment at 500 to 635°C for 1 hour or more, hot rolling or hot rolling and cold rolling is performed to form a skin material. ,
This was superimposed on at least one side of a core material made of Al or Al alloy, heated and then integrated by hot rolling, and then 8
0~98% cold rolling, then 250~450%
A method for producing an aluminum alloy composite material having a sacrificial layer, the method comprising performing intermediate annealing at °C and then cold rolling. (2) After being integrated by hot rolling, 250 to 450
A method for producing an aluminum alloy composite material having a sacrificial layer according to claim 1, which comprises performing intermediate annealing at .degree. C. and then cold rolling by 80 to 98%.