JPS63166951A - Al-alloy fin material for heat exchanger excellent in brazing characteristic - Google Patents

Abstract

PURPOSE:To improve fin-material assembly yield and also to prolong the durability of a heat exchanger, by regulating the full annealing temp. at the temp.-rise rate at the time of brazing a sheet metal of Al alloy for fin material to a specific temp. range in manufacturing heat exchangers. CONSTITUTION:At the time of manufacturing heat exchangers made of Al alloy, fins are manufactured by the use of a sheet metal of Al alloy in which full annealing temp. at the temp.-rise rate at the time of brazing by means of a brazing filler metal of Al-Si alloy for constituting a joined part where fin materials made of Al alloy are joined is regulated to 450-570 deg.C. If the Al-alloy material of this kind is used, crystalline neuclei grow in a rolling direction while absorbing the energy of working texture when the heating temp. at the time of brazing as fin material is raised, so that the crystalline grains of a thin Al-alloy film for fin material become flat and coarse anisotropic crystals, the infiltration of the brazing filler metal into a core material in a brazing sheet is made inactive, and deterioration in high-temp. strength is removed. In this way, superior heat exchangers can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention is applicable to, for example, when manufacturing a heat exchanger by brazing a fin material and a tube material, 1. The present invention relates to an A1 alloy fin material for heat exchangers that exhibits excellent sagging resistance and maintains excellent corrosion resistance even when used as a heat exchanger, and has excellent brazing properties.

[Prior art and its problems 1 Conventionally, in general, it depends on brazability! ! The remaining A1 alloy heat exchangers often had problems with brazing beans. The most common cause is deformation of the fin material during brazing. Brazing is usually 600
It is carried out at temperatures around ℃, but at such high temperatures,
If the molten Al-8i brazing filler metal that forms the joint enters through the grain boundaries of the fin material AI Imakane veneer or the crystal grain boundaries of the Pre-Song sheet core material and the fin becomes thin, the high-temperature strength of the fin will decrease. This results in a severe decrease in brazability, easily causing plastic deformation, and deteriorating brazing properties. In order to solve these difficulties, various attempts have been made regarding the chemical composition of A1 alloy plates and each step of the manufacturing method of those A1 alloy plates.

However, in these attempts, the manufacturing conditions for A1 alloy plates must be determined for individual materials with various component compositions, and it is said that it cannot be a unified condition that can solve the problem. That was the reality.

While conducting research to solve the above-mentioned problems, the present invention developed A1 for various fin materials with various processing histories.
As a result of examining the structure changes, strength changes, etc. of alloy veneers or their plating sheet core materials (hereinafter referred to as A1 alloy thin sheets for fin materials) due to heating during brazing, it was found that these materials Not only composition but also A1 for fin material
It was determined that the complete annealing temperature at the temperature increase rate during brazing of thin alloy sheets is an important factor that influences the degree of penetration of solder into the fin material.The main points of this research are as follows:
An A1 alloy thin plate for a heat exchanger, characterized in that the A1 alloy thin plate for fin material is composed of an A1 alloy thin plate whose complete annealing temperature at a heating rate during brazing is more than 450°C and less than 570°C. Exists in alloy fin material.

Next, the reasons for limiting the present invention as described above will be explained: a) A case where the complete annealing temperature at the temperature increase rate during brazing of the A1 alloy thin plate for fin material is 450°C or less.

In such cases, many recrystallized nuclei are formed in the material, and the processing energy is completely consumed during this crystal growth process, and the alloy components are dispersed as precipitates.
Even if the heating temperature increases further, it does not lead to coarsening of crystal grains. When the crystal grains are refined in this way, it becomes easy for wax to enter through the grain boundaries in the plating sheet, and on the other hand, in the case of the plating sheet, it becomes easy for wax to enter through the grain boundaries.
In a single alloy plate of No. 1, deformation easily occurs at grain boundaries, and as a result, high temperature strength does not increase.

b) When the complete annealing temperature at the temperature increase rate during brazing of the A1 alloy thin plate for fin material exceeds 570°C.

In such a case, the processed structure will remain in the fin material, and during brazing, the brazing material will move into the A1 alloy thin plate for the fin material through the processed structure. As a result, this causes severe corrosion of the heat exchanger and also causes a decrease in high temperature strength.

c) When the complete annealing temperature of the fin material Yoni 1 alloy thin plate at the temperature increase rate during brazing exceeds 450°C and becomes 570°C or less.

In this case, the crystal nuclei generated at a temperature sufficiently lower than 450°C and the processed structure can coexist until the temperature reaches a sufficiently high temperature, so that when the heating temperature rises, the crystal nuclei absorb the processing energy of the processed structure. As a result, the crystal grains in the Fin Material User 1 alloy thin plate become flat, coarse, and anisotropic crystals.

As a result, the penetration of the filler metal into the core material in the plating sheet becomes inactive, while in the case of the AI alloy veneer for the fin material, deformation at the grain boundaries is restricted. Decrease in high temperature strength is also suppressed. The present invention will be described below based on examples.

[Example 1 A1 alloy No. 1 to 4 for fin material of the present invention whose composition is shown in Table 1 by a normal melting process, Comparative Example A1
Alloy Nos. 7 to 8 and A1 alloys A and B for brazing filler metal were melted and rolled into II lumps, and then homogenized under normal conditions.

Next, regarding the A1 alloy ingot produced as described above, for the A1 alloy ingot for the plain long sheet core material,
Hot rolling was performed to obtain a hot rolled plate with a thickness of 81 mm, while A1 alloy for veneer *i and A1 alloy mass for brazing metal were similarly hot rolled to obtain a 5 mm hot rolled plate. Thereafter, cold rolling was performed to obtain a cold rolled sheet II.

Next, the A1 alloy cold-rolled plates for the top brazing filler metal are superimposed on both sides of the A1 alloy hot-rolled plate for the core material, and a plate material with a thickness of 1.3 mm is made by hot rolling and cold rolling. After that, the final cold opening pressure is increased while appropriately performing intermediate annealing under the following conditions: temperature increase rate: 0.5°C/min, heating temperature: 380°C, holding temperature: 2 hours. Cold rolling was carried out at a rolling rate of 10 to 50% to produce plating sheets each having a thickness of 0.13 mm.

Table 1 In addition, the cold-rolled sheets for veneers were also subjected to intermediate annealing under the same conditions as appropriate, and cold-rolled to a final cold rolling reduction of 10 to 50%. A .13w+a A1 alloy veneer was manufactured.

Next, in order to evaluate the quality of these A1 alloy thin plates for fin materials, tests were conducted under the following conditions regarding sagging resistance test, brazing test, complete annealing temperature during brazing, etc., and the results are shown in Table 2. Indicated.

m1~ As is clear from the second table, the complete annealing temperature at the temperature increase rate during brazing of the A1 alloy thin plate for fin material is 4.
It is clear that when the temperature exceeds 50°C and falls below 570°C, the A1 alloy fin material for a heat exchanger has excellent droop resistance and good brazing properties.

[Test Method 1 ■ Drooping Resistance Test Test pieces having dimensions of 30 mm width x 130 mm length were cut out from each of the above A1 alloy thin plates for fin materials, and the longitudinal sides of these test pieces were cut out as shown in Figure 1. 10 from one end of the direction
Hold the part up to 0+ua horizontally, and the rest r) 301Il
With the part b protruding, and with the protruding part free, the temperature was raised from room temperature to 620°C in a vacuum of 10"'torr or in a nitrogen gas atmosphere of 1 atm, and at 620°C for 10 minutes. After the holding heat treatment, the hanging height of the protrusion at the free end of each specimen was measured, and the results are shown in Table @2.

■ Brazeability test After applying full date processing to each of the above-mentioned fin material A1 alloy thin plates, (1) For the fin material A1 alloy veneer, separately prepared JI
Assemble S3003 cladding brazing sheet with a thickness of 0.5, as shown in Figure 2. (2) For the A1 alloy plating sheet for fin material, use a separately prepared JIS1050A+ plate with a thickness of 1 ring. were assembled as shown in FIG.

Then, heat treatment was performed by increasing the temperature from room temperature to 620'C in a vacuum of 10'' torr or in a nitrogen gas atmosphere of 1 atm, and maintaining the temperature at 620°C for 10 minutes.

- The state of deformation of the fin material after brazing or the state of the fillet formed between the fin plates was observed, and the results are shown in Table 2 as brazeability.

■Measurement of complete annealing temperature at heating rate during brazing of A1 alloy thin plate for fin material.

Each of the A1 alloy thin sheets described above was charged into an inert gas atmosphere brazing furnace and heated to a temperature of 240 to 620°C at the same temperature increase rate as for normal brazing. After that, it was cooled to room temperature and tensile strength was applied. A test was conducted to examine changes in strength (softening characteristics), and the temperature at which complete annealing was determined is shown in Table #12.

[Effect of the invention 1 As described above, the A1 alloy fin material for heat exchangers of the present invention has the following effects:
In manufacturing these products, without relying on conventional multidimensional quality control standards, A
By concentrating on extremely simple control items such as the complete annealing temperature of the A1 alloy thin plate, manufacturing of A1 alloy fin material for heat exchangers is extremely easy, the yield when assembling it as a heat exchanger is improved, and the Since these materials exhibit excellent sagging resistance, they do not cause any sagging or deformation (and fillet formation is sufficient, so
It also has sufficient durability as a heat exchanger.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the drooping resistance test, and in the figure, 1......test piece 2......
...Test piece holding part 2a, 2b......Test piece support part d...Curving/Drooping Figure 2 is an explanatory diagram of the brazing test. , 1... Cordate fin 2...
・・・Adjustment board

Claims (1)

[Claims] Excellent brazing properties, characterized in that the Al alloy plate serving as the fin material is composed of an Al alloy thin plate whose temperature exceeds 450°C and is below 570°C at the complete annealing temperature at the temperature increase rate during brazing. A1 alloy fin material for heat exchangers.