JPS6237757B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an Al alloy heat exchanger manufactured by vacuum brazing a fin material to a tube body. Conventionally, heat exchangers such as radiators for motorcycles and automobiles, condensers for coolers, and even evaporators have been constructed using a single-layer pipe body made of an Al-Mn alloy and a single-layer fin material body made of an Al-Zn alloy. It is manufactured by brazing fin materials in a vacuum, which are made up of brazing sheets with Al--Si alloy brazing filler metal clad on both sides. In the tube body of such a conventional Al alloy heat exchanger,
For example, when tap water or especially a fluid containing heavy metal ions such as Cu is distributed, pitting corrosion is likely to occur, and as this pitting corrosion progresses, the fluid inside the pipe may seep out, or the external liquid or In recent years, the outer layer of the Al-Mn alloy and the more electrochemically base Al-Zn alloy have been developed for the tube body. Two-layer cladding materials consisting of an inner layer have come to be used, and attempts have also been made to corrode the inner layer preferentially to better protect the outer layer from corrosion, thereby imparting excellent pitting corrosion resistance to the pipe body. However, even if a two-layer clad material is used as the tube body, when manufacturing an Al alloy heat exchanger by vacuum brazing the fin material to the tube body, the tube body may be damaged during vacuum brazing. When exposed to high temperatures, the Zn in the inner layer of the tube evaporates preferentially into the atmosphere, and since this evaporation of Zn occurs on the surface of the inner layer of the tube, the Zn in the inner layer of the tube after brazing is
Not only does the Zn content decrease, but especially the Zn content at the inner surface of the tube decreases to almost zero, and as it goes deeper than the surface,
Undesirable Zn for corrosion protection, such as high Zn concentration
In such cases, significant local corrosion often occurs, often resulting in the formation of through holes. From the above-mentioned viewpoint, this invention is particularly applicable to Al
-The tube is made of a two-layer clad material consisting of an outer layer of Mn alloy and an inner layer of Al-Mn-Zn alloy.
Manufactured by vacuum brazing a fin material consisting of a brazing sheet made of a fin material body made of a single layer or multiple layers of Al and Al alloy and cladding with Al-Si alloy brazing filler metal on both sides. This product provides an Al alloy heat exchanger that solves the problems of conventional Al alloy heat exchangers.
It is composed of a three-layer clad material consisting of an outer layer of an Al-Mn-Zn alloy, an inner layer of pure Al or Al-Mg alloy, and the outer layer, middle layer, and inner layer are electrochemically bonded in that order. By making it base, even when exposed to high temperatures during vacuum brazing, the intermediate layer
The evaporation of Zn is suppressed by the inner layer, and the preferential elution from the inner layer, which is electrochemically more base, imparts excellent pitting corrosion resistance to the tube, thereby significantly extending its service life. This is a unique heat exchanger made of aluminum alloy. In addition, the Al--Mn alloy constituting the outer layer of the tube of the heat exchanger of the present invention includes Mn: 0.4 to 1.5% by weight.
It is desirable to have a composition that further contains 0.01 to 0.3% by weight of one or both of Cr and Zr as necessary, and the remainder of Al and unavoidable impurities. As for the constituent Al-Mn-Zn alloy, Mn: 0.4 to 1.5
% by weight, Zn: 0.3 to 3.0% by weight, and further contains one or two of Cr and Zr as necessary.
An Al-Mg alloy containing 0.01 to 0.3% by weight of seeds, and consisting of Al and the remainder of unavoidable impurities is the Al-Mg alloy that also constitutes the inner layer.
Mg: 0.1-2.5% by weight, Al and inevitable impurities:
It is desirable to have a composition consisting of the remainder. In addition, in the outer layer, intermediate layer, and inner layer constituting the tube body of the heat exchanger of this invention, each
The reason why the desirable composition of the Al alloy was limited to the above is due to the reasons shown below.Since the same components were limited for the same reason for the outer layer and the intermediate layer, each component will be explained below. do. (a) Mn Mn content improves corrosion resistance and sagging resistance during high-temperature heating, but if the content is less than 0.4%, the desired improvement effect cannot be obtained;
On the other hand, if the content exceeds 1.5%, not only will further improvement effects not be achieved, but the plastic workability will decrease, so the content should be reduced to 0.4%.
~1.5%. (b) Cr and Zr These components have the uniform effect of further improving the sagging resistance of the thin plate, so they are included as necessary when particularly excellent sagging resistance is required. If the content is less than 0.01%, the desired effect of improving the above action cannot be obtained, while if the content exceeds 0.3%, the corrosion resistance and plastic workability will decrease, so the content should be adjusted to 0.01 to 0.3%. %
And so. (c) Zn Zn is contained to make the intermediate layer electrochemically more base than the Al-Mn alloy of the outer layer, and to protect the outer layer from corrosion through the sacrificial anode effect of the intermediate layer. If the content is less than 0.3%, Zn will remain in the intermediate layer because it will diffuse from the intermediate layer to the inner and outer layers and evaporate from the surface of the inner layer. Zn
If the content is less than 0.1%, the sacrificial anode will not be able to exhibit sufficient effect.
It is necessary to contain 0.3% or more, but if the content exceeds 3.0%, Zn diffusion into the inner and outer layers and evaporation of diffused Zn from the surface of the inner layer will become significant, resulting in electrical problems in the outer layer, intermediate layer, and inner layer. In some cases, the chemically lower ranking may be disrupted, resulting in a Zn concentration distribution that is more likely to cause local corrosion, and the high-temperature heating furnace may be contaminated by evaporated Zn. It was set at 0.3-3.0%. (d) Mg Pure Al and Al-Mg alloys are identified as materials that are electrochemically more base and have excellent corrosion resistance than the intermediate layer composed of Al-Mn-Zn alloys, but Al- Mg alloys have better corrosion resistance than pure Al and the ability to suppress the evaporation of diffused Zn. However, if the Mg content is less than 0.1%, the desired property improvement effect cannot be obtained;
If the content exceeds %, not only will the deformation resistance increase, making it difficult to manufacture the clad material, but also a large amount will evaporate during high-temperature heating during vacuum brazing, promoting contamination of the furnace. , the Mg content of the Al-Mg alloy that makes up the inner layer is 0.1 to 2.5%.
And so. Regarding the inner layer of the tube according to this invention,
The layer thickness must be selected taking into account the brazing temperature and time, the Zn content in the intermediate layer, etc., but from the viewpoint of suppressing Zn evaporation and initial erosion depth, it is usually the overall thickness of the pipe body. It is appropriate to set it at about 3 to 20%. Next, the heat exchanger of the present invention will be explained with reference to examples. First, Al and Al alloys 1 to 1 with the respective compositions shown in Table 1 were prepared by a normal melting method.
9 was melted and cast into an ingot. In addition, these Al
And Al alloys 1 to 9 contain Mn: 0.01% or less, Mg: 0.01% or less, respectively, as inevitable impurities.
Zn: 0.01% or less, Si: 0.10~0.13%, Fe: 0.21~
0.25%, and Cu: 0.03 to 0.04%.

[Table] These ingots were then hot rolled under normal conditions to a plate thickness of 8 mm, and alloys 4 to 9 were further cold rolled to a plate thickness of 1 mm. Next, the Al alloy 1 for outer layer prepared in this way
Layer each of Al and Al alloys 4 to 9 for the intermediate layer and inner layer on the upper surface of each of the thick plates of ~3 according to the combinations shown in Table 2, and hot-roll under normal conditions. Depending on the board thickness 1mm
Then, after further intermediate annealing, the material was cold rolled to a thickness of 0.4 mm to obtain a three-layer cladding material for a tube body of a heat exchanger of the present invention (hereinafter referred to as a cladding material for a tube body of the present invention). Examples 1 to 8 and conventional two-layer cladding materials for pipe bodies (hereinafter referred to as conventional cladding materials for pipe bodies) for comparison were manufactured, respectively. Clad material 1 for pipes of the present invention obtained as a result
Test pieces with dimensions of 50 mm in width x 80 mm in length were cut out from the conventional clad material for pipes, and these test pieces were subjected to heat treatment under substantially the same conditions as vacuum brazing treatment, i.e. Pressure: approx.
The specimens of cladding materials 3 and 4 for pipes of the present invention were heated to 550°C in the atmosphere for 3 minutes in a vacuum of 10 ^-4 torr.
Zn diffusion heat treatment was performed for 10 minutes. Regarding the test piece of the above-mentioned cladding material 3 for pipes of the present invention,
The Zn concentration distribution before the Zn diffusion heat treatment in the cross section is shown in FIG. 1, and the Zn concentration distribution after the Zn diffusion heat treatment is shown in FIG. From the results shown in FIGS. 1 and 2, the evaporation of Zn contained in the intermediate layer is significantly suppressed by providing the inner layer, so the residual amount of Zn in the intermediate layer is extremely high. It is also clear that by applying the Zn diffusion heat treatment, Zn is also contained on the surface of the inner layer, resulting in an extremely ideal Zn concentration distribution in terms of corrosion protection. Subsequently, each of the test pieces subjected to the heat treatment or further Zn diffusion heat treatment as described above was coated with insulation, leaving the inner layer surface intact.
A 500-hour CASS test and a 500-hour tap water immersion test in 30℃ tap water containing 10 ppm Cu ions were conducted to determine the number of pitting corrosion and maximum pitting corrosion after the test.

[Table] Depths were measured for each. The measurement results are also shown in Table 2. From the results shown in Table 2, all of the cladding materials 1 to 8 for pipes of the present invention exhibited superior pitting corrosion resistance compared to the conventional cladding materials for pipes, and in particular, the cladding materials of the present invention subjected to Zn diffusion heat treatment. It is clear that the pipe cladding materials 3 and 4 exhibit remarkable pitting corrosion resistance, and corrosion is completely stopped in the inner layer. As mentioned above, in the Al alloy heat exchanger of the present invention, the tube body is composed of a three-layer clad material, so during vacuum brazing for manufacturing the heat exchanger, the Al--Mn-- which constitutes the intermediate layer is The evaporation of Zn from the Zn-based alloy is suppressed by the inner layer, and the arrangement is such that the middle layer is electrochemically less noble than the outer layer, and the inner layer is electrochemically less noble than the middle layer. When exposed to water, it is preferentially eluted from the inner layer and exhibits a sacrificial anode effect, which significantly extends the service life of the tube and, in particular, the service life of the heat exchanger. This brings about industrially useful effects such as the ability to

[Brief explanation of the drawing]

FIGS. 1 and 2 show Zn before (FIG. 1) and after Zn diffusion heat treatment (FIG. 2) in the cross section of the cladding material 3 for pipe bodies of the present invention.
It is a graph showing concentration distribution.

Claims (1)

[Claims] 1 Al-Si is applied to both sides of the fin material body made of a single layer or multiple layers of Al and Al alloy in an Al alloy tube body.
In an Al alloy heat exchanger manufactured by brazing in a vacuum a fin material made of a brazing sheet made of a brazing sheet clad with an Al-Mn alloy brazing filler metal, the tube body is The outer layer of alloy, the middle layer of Al-Mn-Zn alloy, and the pure Al
Alternatively, an Al alloy heat exchanger comprising a three-layer clad material with an inner layer of Al--Mg alloy, and the outer layer, middle layer, and inner layer are made electrochemically more base in that order. 2. The Al alloy according to claim 1, wherein the outer layer of the tube is made of an Al--Mn alloy having a composition of 0.4 to 1.5% by weight of Mn, Al, and the remainder of unavoidable impurities. manufactured heat exchanger. 3 The outer layer of the tube is made of Mn: 0.4 to 1.5% by weight, one or two of Cr and Zr: 0.01
0.3% by weight, Al and unavoidable impurities:
Al alloy heat exchanger. 4 Mn: 0.4 to 1.5 for the intermediate layer in the above tube.
% by weight, Zn: 0.3 to 3.0% by weight, Al and unavoidable impurities: the remainder. The Al alloy heat exchanger according to item 3. 5 Mn: 0.4 to 1.5 for the intermediate layer in the above tube.
Al-- having a composition consisting of: weight%, Zn: 0.3 to 3.0 weight%, one or two of Cr and Zr: 0.01 to 0.3 weight%, Al and unavoidable impurities: the remainder.
Claims 1, 2, or 3, characterized in that the device is made of a Mn--Zn alloy.
Al alloy heat exchanger. 6. Claims 1 and 2, characterized in that the inner layer of the tube is made of an Al--Mg alloy having a composition of 0.1 to 2.5% by weight of Mg, Al, and the remainder of unavoidable impurities. , the Al alloy heat exchanger according to item 3, item 4, or item 5.