JPH0747802B2 - Method for manufacturing vacuum brazed structure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an aluminum alloy structure which causes less buckling deformation during vacuum brazing.

[Prior Art] Aluminum alloys are used for the structure of heat exchangers such as condensers, radiators, and evaporators for vehicles and various industries because of their good workability, excellent corrosion resistance, and light weight. ing. The methods of joining aluminum alloys are roughly classified into flux brazing and vacuum brazing not using flux. In flux brazing, the flux itself is expensive,
Vacuum brazing has been widely used in recent years because of problems in the cleaning process and wastewater treatment. Then, as the demand for large heat exchangers has increased, the vacuum heating furnace has also become larger.

However, when brazing is performed in a large vacuum heating furnace, buckling of the structure occurs due to erosion at the time of brazing, which has not occurred in conventional flux brazing or brazing in a small vacuum heating furnace.

There are several papers on erosion resistance, and the occurrence of erosion is remarkable when subgrains remain up to the wax melting start temperature, and conversely, when it is easy to recrystallize coarsely, erosion occurs. It is known that it is difficult to do (Suzuki et al .: Light Metals, vol.34, No.2 [1984] p708,
Toma et al .; Light Metals, vol.37, No.2 [1987] p119). Further, in a large-sized vacuum heating furnace, the rate of temperature rise during brazing is slow, so erosion is likely to occur.

[Problems to be Solved by the Invention] From the above, the present invention is intended to reduce buckling deformation during brazing.

Large-sized vacuum heating furnaces are brazing with a slow heating rate of 5 to 100 ° C / hr, but in the conventional case, brazing is performed with a heating rate faster than 100 ° C / hr. In the case of a larger heat exchanger, the load applied to the fin material is about 0.2 kgf / cm ² .

Therefore, in carrying out the present invention, the structure is 0.2 kgf / cm ²
By performing vacuum brazing while applying a load equivalent to, and examining the buckling resistance, it was possible to obtain a structure with a small amount of buckling deformation.

More specifically, the molded structure has strength,
Since corrosion resistance is required, the A3003 series alloy containing Mn is often used for this application. In the A3003-based alloy, A1-Mn-based compounds precipitate and dominate the recrystallization behavior. Vacuum brazing heats up to 550 ° C or higher at a relatively slow temperature rise of about 10 ° C / hr. At this time, if recrystallization does not occur sufficiently and subgrain structure remains, erosion due to wax corrosion causes erosion. It happens. When erosion occurs, the strength is remarkably reduced, and local deformation (buckling) occurs, which results in a poor shape of the structure after brazing, which is not preferable. In order to prevent erosion from occurring, it is sufficient that the material is sufficiently recrystallized before the brazing material melts (the temperature is reached) during heating of the vacuum brazing.

In the present invention, as a result of various examination of these conditions, Fe, Mn, S
It was found that buckling deformation during brazing can be reduced by controlling the amounts of i and Cu and the distribution size of precipitates.

[Means for Solving the Problems] In the present invention, Mn: 1.0 to 1.6% (wt%, the same applies hereinafter), Fe: 0.
An alloy ingot containing 8 or less, Si: 0.4% or less, Cu: 0.2% or less and the balance A1 and unavoidable impurities, and Fe / Si = 1 to 4 Mn / Si = 3 to 12 at 570 ° C. for 8 hours. Heat more than 450-550
Hot rolling at ℃, then with or without cold rolling, intermediate annealing at 300 ~ 450 ℃ for 0.5 hr or more, cold rolling at a plate thickness reduction rate of 30% or more, then 300 ~ 450 ℃ At 0.5h
The maximum length of the precipitated compound observed on the cut surface parallel to the rolled surface after annealing for r or more is 1 μm or less, and 5 × 10 ⁴
A method for producing a material for a vacuum brazing structure, which is characterized by forming a soft thin plate having a distribution of at least 5 pieces / mm ² and cold rolling at a plate thickness reduction rate of 5 to 30% Then, after bending, overhanging, pulling, and ironing deformation to form a predetermined fin shape so that the total working strain amount including the working strain amount by cold rolling becomes 10 to 35%, and after assembling it into the structure The method for producing a vacuum brazed structure is characterized in that the temperature is raised at a rate of 5 to 100 ° C./hr and brazing is performed in a vacuum.

In order to reduce the buckling deformation during brazing, it is necessary that the material is not easily deformed at high temperature and at the same time erosion is unlikely to occur. In the former case, Mn is used in the present invention.
By appropriately adding Cu and Cu, and by further setting the final refining to H1n, the stress applied during large-scale vacuum brazing (about 0.2 kgf
It is possible to obtain a high temperature strength that can withstand a pressure of 1 cm / cm ² .
Regarding the latter erosion-resistant point, it can be said that the internal structure of the material, which is determined by the distribution state of the precipitates together with the components, is the most influential factor. That is, in order to use a material that is unlikely to cause erosion during brazing, it is necessary to coarsely recrystallize easily during brazing. For that purpose, the maximum length before brazing is 1 μm from the relationship between the workability from annealing to brazing in the process of manufacturing the material and the temperature rising rate of 5 to 100 ° C / hr during brazing. The following fine precipitates are plate materials having a distribution density of 5 × 10 ⁴ pieces / mm ² or more, and the workability from annealing to brazing is 10 to 35
% Is required. If the precipitates are larger than 1 μm, they tend to act as nuclei for recrystallization at the time of brazing heating after fin processing, which makes crystal grains fine, which is not preferable. Moreover, the distribution density is 5 × 10 ⁴ in terms of area ratio.
When the number is less than the number of pieces / mm ^{2, the} amount of precipitation before heating for brazing is insufficient, precipitation tends to occur during heating for brazing, and the crystal grains become fine, which is not preferable.

Regarding the components, the amounts of Fe, Si, and Mn particularly affect the precipitation state. These elements combine with Al and form a stable phase α
Easily precipitated as a phase.

Fe / Si = 1 to 4 is suitable. If it is less than 1, the amount of solid solution Si increases, and the grain refinement due to the precipitation of Si during brazing is likely to occur. On the other hand, if it is larger than 4, coarse Al-Mn-Fe compounds larger than 1 μm are likely to be formed, and recrystallized grains are likely to be fine. Furthermore, it impedes the fine precipitation of Al-Mn-Si compounds.

On the other hand, Mn / Si = 3 to 12 is suitable. If it is less than 3, similarly, the amount of solid solution Si increases, which is not preferable, and if it is more than 12, the amount of solid solution Mn increases, and the crystal grains are likely to become fine due to precipitation of Al-Mn compound during brazing heating.

The absolute amounts of the components are Fe ≦ 0.8%, 1.0 ≦ Mn ≦ 1.6%, S
i ≦ 0.4% is appropriate. If both are added in excess of the maximum value, a coarse compound of 1 μm or more is likely to be formed, and the amount of solid solution is also increased, so that the crystal grains during brazing heating are likely to become fine as described above. If the Mn content is less than 1%, the high temperature strength will be poor. Although high temperature strength can be obtained by adding Mn, in order to obtain higher temperature strength, Cu
Is added. However, if added over 0.2%,
Since the corrosion resistance is poor, Cu ≦ 0.2% is preferable.

The production conditions for controlling the size and distribution of the fine compound are as follows. Ingot heating at 570 ℃ or higher 8
Perform for 3 hours or more at hr or more or 600 ℃ or more. This is 0.
This is because the distribution of a compound having a size of less than 1 μm is reduced and a part of the compound is grown to have a size of 0.1 μm or more and 1 μm or less. The temperature is high, and the longer the time, the better. However, from the economical point of view, it is practically within 20 hours.

Hot rolling and intermediate annealing are performed to adjust the thickness of the alloy sheet, but in order to promote precipitation of alloy components again in the subsequent heat treatment, cold working of 30% or more is added. It is convenient to be there. It is advisable to carry out hot rolling at 450 to 550 ° C. and heat treatment for intermediate annealing at 300 to 450 ° C. for 0.5 hr or more.

The final heat treatment of the alloy plate at 300 to 450 ° C. for 0.5 hr or more is suitable, and the alloy components are precipitated and the size thereof is increased. If the temperature is less than 300 ° C., the effect is small, and coarse recrystallized grains higher than 450 ° C. are likely to occur, which is not preferable because the strength and workability of the thin plate are impaired.

When processing the structure of thin material made in this way,
The total amount of processing strain including the amount of processing strain due to cold rolling is
Bending, overhanging, pulling, and ironing deformation to form a predetermined fin shape so as to be 10 to 35%. If the workability is higher than this, coarse recrystallized grains are generated, which is not preferable.

The rate of temperature rise during brazing is set to 5 to 100 ° C./hr because good results can be expected even if the temperature rises faster than this even without depending on the conditions of the present invention. It was limited because it is almost impossible in terms of economic capacity and equipment capacity in industrial production.

[Example] Example 1 An aluminum alloy ingot having the components shown in Table 1 was cast. The ingot was heated at 580 ° C. for 10 hours, hot-rolled by an ordinary method, then cold-rolled to various plate thicknesses shown in Table 1, and annealed at 400 ° C. for 1 hour.

The distribution of precipitates of 1 μm or less on this plate material was measured by using an image analyzer (Luzex500, manufactured by Nireco Co., Ltd.), and the results are shown in Table 1.

The plate thus produced was cold-rolled to 0.20 mmt and then formed into fins having a fin pitch of 2.7 mm and a fin height of 9 mm. The workability at the time of fin forming was determined from the change in hardness of the cross section, and was found to be 5 to 25% in terms of the sheet thickness reduction rate by rolling.

Then, as shown in FIG.
It was sandwiched between A 3003 and JIS A 4004 clad plates 2 and 3 to make a fin core for experiments. Place a weight equivalent to a stress of 0.2 kgf / cm ² on this core and use a vacuum heating furnace with a vacuum degree of about 5 × 10 ^-6 Torr.
It was heated to 600 ° C and brazed.

The heating rate was 5 to 100 ° C./hr. Then, the buckling amount α after brazing was measured as shown in FIG. 2 and shown in Table 1.

In order to confirm the corrosion resistance of the final plate, 5% saline (35 ° C) was sprayed for 100 hours and a corrosion resistance test was conducted according to JIS Z 2371, and the results were compared with JIS A 1050. And evaluated and shown in Table 1. The components of JIS A 1050 are
Fe: 0.26%, Si: 0.08%, and other 0.01% or less unavoidable impurities. The manufacturing method was almost the same as that of the fin of the example, and the plate thickness during annealing was 0.23 mm.

Each material in Table 1 will be described.

The plate materials according to the present invention are Nos. 1 to 7. No. 1 is a material in which the upper limit of Fe / Si is 4.0 and the Mn content is 1.58% near the upper limit. N
o.2 is a material in which Fe / Si is 1.1 near the lower limit and Mn content is 1.60% at the upper limit. No. 3 is a material in which Mn / Si is 3.2 near the lower limit and Si content is 0.38% near the upper limit. No. 4 is a material whose Mn / Si is 11.1 near the upper limit. No. 5 has Fe content near the upper limit
It is a material with 0.77% and a Cu content of 0.18% near the upper limit. N
o.6 is a material whose Mn content is 1.08% near the lower limit. No.7
Is a material having Fe / Si and Mn / Si near the lower limit and a distribution density of precipitates of 1 μm or more near the lower limit.

Comparative materials are Nos. 8-18. No. 8 is a material that exceeds the upper limit of Fe / Si. No. 9 is a material that exceeds the lower limit of Fe / Si. No. 10 is a material that exceeds the upper limit of Mn / Si. No. 11 is M
It is a material below the lower limit of n / Si. No. 12 is a material that exceeds the upper limit of Fe content. No. 13 is a material that exceeds the upper limit of the amount of Mn. No. 14 is a material that exceeds the upper limit of Si content. No.15
Is a material that exceeds the upper limit of the Cu content. No. 16 is a material in which the distribution density of precipitates is below the lower limit by making the amount of Mn extremely small and making Fe / Si and Mn / Si near the lower limit. No. 17 has a plate thickness of 0.28 mm during intermediate annealing, and the workability from intermediate annealing to fin processing exceeds the upper limit.
32 to 50%. No. 18 has a temperature rising rate during brazing heating of 120 to 500 ° C / hr, which exceeds 100 ° C / hr.

It can be seen from the buckling test results that the brazing structures for plate materials according to the present invention of Nos. 1 to 7 in Table 1 exhibit a buckling amount of 100 μm or less and are excellent in buckling resistance. Also, the corrosion resistance is JIS
Although it is slightly inferior to A 1050, it can be said to be good.

It can be seen that the brazed structures according to the comparative examples No. 8 to 14 and No. 16 to 18 in Table 1 exhibit a buckling amount of 100 μm or more, and are inferior in buckling resistance. In addition, No. 15 in which the Cu content exceeds 0.2% is inferior in corrosion resistance.

Example 2 The alloy shown in Table 2 was agglomerated to 0.26 mm under the conditions shown in Table 3.
Soft plates with t, 0.23 mmt and 0.21 mmt were manufactured. The distribution of precipitates on the annealed plate was 2-3 × 10 ⁵ pieces / mm ² . As shown in Table 4, cold rolling of these plates was 0%, 8.7%, 19.2%.
% To 0.21 mmt, and as a fin-formed product, repeated bending work was added by 15% and 20% (estimated from the amount of increase in hardness).

Subsequently, Table 4 shows the amount of buckling and the recrystallized grain size of the fin material when a test fin core was brazed in the same manner as in Example 1. When the total processing strain is 15 to 31%, the recrystallized grains become large, erosion is suppressed, and the amount of buckling of the fin core becomes small.

[Advantages of the Invention] According to the present invention, it is possible to obtain a brazing structure with less buckling in large-sized vacuum brazing with a slow temperature rising rate.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a test piece of an example of the present invention, and FIG. 2 is an explanatory diagram of test results. 1 ... Fins, 2, 3 ... Plates

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teruo Kurachi 2-6 Nishinagasumotodori, Amagasaki, Hyogo Prefecture Sumitomo Precision Industries, Ltd. (72) Inventor Tetsuo Abiko 2-6 Nishinazumotodori, Amagasaki, Hyogo Sumitomo Precision Industry Co., Ltd.

Claims (2)

[Claims] 1. Mn: 1.0 to 1.6% (% by weight, the same applies hereinafter), Fe:
Remainder A1 containing 0.8% or less, Si: 0.4% or less, Cu: 0.2% or less
And inevitable impurities, and Fe / Si = 1 to 4 Mn / Si = 3 to 12 alloy ingots heated at 570 ° C or higher for 8 hours or longer, and 450 to 550
Hot rolling at ℃, then with or without cold rolling, intermediate annealing at 300 ~ 450 ℃ for 0.5 hr or more, cold rolling at a plate thickness reduction rate of 30% or more, then 300 ~ 450 ℃ At 0.5h
The maximum length of the precipitated compound observed on the cut surface parallel to the rolled surface after annealing for r or more is 1 μm or less, and 5 × 10 ⁴
A method for producing a material for a vacuum brazing structure, which comprises forming a soft thin plate having a distribution of at least 1 piece / mm ² . 2. The material according to claim 1, wherein the reduction rate of plate thickness is 5
After cold-rolling up to 30% to a specified thickness, bend, bulge, pull, and iron to the specified amount so that the total working strain including the working strain due to cold rolling is 10-35%. After forming into a fin shape and assembling into a structure, 5-100 ° C /
A method for manufacturing a vacuum brazed structure, which comprises heating at a rate of hr and brazing in a vacuum.