JPH01148489A - Al alloy brazing sheet for heat exchanger having excellent corrosion resistance at fillet forming part - Google Patents

Abstract

PURPOSE:To obtain the title Al alloy brazing sheet having excellent corrosion resistance by cladding one or both sides of the Al alloy core having a specified composition with the solder having a specified composition. CONSTITUTION:The Al alloy core contains, 0.1-0.7% Cu, 0.3-1.5% Mn, 0.7-1.3% Si, one or >=2 kinds among 0.05-0.2% Mg, 0.03-0.15% Zr, and 0.03-0.2% Cr, the balance Al, and inevitable impurities. One or both sides of the core are clad with an Al alloy solder contg., by weight, 0.03-0.2% Cu, 7-12% Si, the balance Al, and inevitable impurities. By this method, an Al alloy brazing sheet for a heat exchanger having excellent corrosion resistance at a fillet forming part is obtained.

Description

Detailed Description of the Invention [Industrial Field of Application] This invention provides a method for forming a fillet portion with excellent corrosion resistance when used in manufacturing A47 alloy heat exchangers such as air conditioners and evaporators by brazing. The present invention relates to an Al alloy brazing sheet that can be used.

[Conventional technology]

Conventionally, in general, in manufacturing the above-mentioned A47 alloy heat exchanger, Cu: 0.
1-0.7%, Mn: 0.3-1.5%.

Sl: 0.7-1.3%.

Further, Mg: 0.05 to 0.2%, Zr: 0
．． 03-0.15%.

C “20, 03-0.2%.

Contains IFli or 2N or more, and the rest is Ag.
One or both sides of the core material of /'47 alloy, which has a composition consisting of alloy and unavoidable impurities, contains Si Miniful 12°, and if necessary, Mg: 0.3 to 2%.

The Al alloy brazing sheet is made by cladding with a brazing filler metal of HeΩ alloy, which has a composition consisting of Al7 and unavoidable impurities. In addition, since it contains Cu, it is electrochemically noble to the brazing filler metal, and has good corrosion resistance, so it is widely used in practice.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional brazing sheet, the core material is more electrochemically noble than the brazing material as described above, so when it is used in the assembly of a heat exchanger and put into practical use. In particular, the fillet formed by the brazing filler metal corrodes preferentially. For example, if the heat exchanger has a laminated structure, the pressure resistance is applied to the fillet forming part, so the fillet Corrosion of the formed parts causes a decrease in the compressive strength of the heat exchanger over time,
This causes a shortened service life.

[Means for solving problems]

Therefore, from the above-mentioned viewpoint, the present inventors developed an Ag alloy brazing sheet that can corrode (sacrificial anode) but form a fillet portion with an extremely slow corrosion rate in order to effectively prevent corrosion of the core material. As a result of conducting research to develop the above-mentioned conventional Al1 alloy brazing sheet, we added 0.03 to 0.2 of Cu as an alloy component to the brazing material that constitutes the conventional Al1 alloy brazing sheet.
%, the core material is well protected from corrosion and the fillet formed thereby is further improved in corrosion resistance.

This invention was made based on the above findings, and includes 0.1 to 0.7% Cu2, M
n: 0.3 to 1.5%.

SI: 0.7-1.3%.

Further, Mg: 0.05 to 0.2%, Zr: 0
．． 03-0.15%.

Cr: 0.03-0.2%.

On one or both sides of an Al alloy core material containing one or more of the following, the remainder being Al and unavoidable impurities, 7 to 12% of Sl 7 and 0.03 to 0.03 of Cu.
0.2%.

Contains, and if necessary, Mg: 0.1-2%.

The AJ alloy brazing sheet for heat exchangers is characterized by excellent corrosion resistance in the fillet forming portion, which is made by cladding with an Al alloy brazing filler metal having a composition containing Al and unavoidable impurities.

Next, the reason why the compositions of the core material and brazing material of the Af1 alloy brazing sheet of the present invention are limited as described above will be explained.

A. Core material (a) Cu The Cu component not only improves the strength at room temperature, but also makes the core material electrochemically nobler than the brazing material and fin material, and has the effect of preferentially preventing corrosion of the core material. However, if the content is less than 0.1%, the desired effect cannot be obtained, while if the content exceeds 0.7%, localized corrosion such as intergranular corrosion will occur. From 0.1 to 0.
It was set at 7%.

(b) Mn and Sl These components have l! -Mn-8l
Brazing has the effect of forming microscopic compounds to improve the strength at room temperature as well as the high temperature strength at heating temperatures, but if the content is less than 04% Mn and less than 0.7% SI, the desired However, if the content exceeds Mn: 1.5% and Sl: 1.3%, the compound becomes coarse. Since the strength decreases and the processability decreases due to the formation of giant crystals, the contents are adjusted to Mn: 0.3 to 1.5% and Sl: 0.7 to I.
It was set at 4%.

(c) Mg, Zr, and Cr These components have the effect of further improving the strength at room temperature and high temperature, but their content is Mg:0.
Zr: less than 0.05%, Zr: less than 0.03%, and Cr
: If it is less than 0.03%, the desired strength improvement effect cannot be obtained,
On the other hand, the contents are Mg: 0.2%, Zr
Cr: 0.15% and Cr: 0.2%, the processability deteriorates, so the contents are respectively Mg: 0.05 to 0.2%, Zr: 0, H to 0.
．． 15%, and Cr: 0.08 to 0.2%.

B. Brazing material (a) 31 The Sl component has the effect of imparting properties to brazing by lowering the melting point and improving fluidity, but if its content is less than 7%, desired brazing cannot be achieved. On the other hand, if the content exceeds 12%, the melting point will rise again, making it impossible to perform the desired brazing, so the content should be reduced to 7 to 12%. It was determined that

(b) Cu The Cu component has the effect of increasing the potential of the brazing filler metal in a state that is electrochemically less noble than the core material, thereby improving the corrosion resistance of the fillet formed in the brazing part in particular. If the content is less than 0.03%, the desired corrosion resistance cannot be secured, while if the content exceeds 0.2%, it may become electrochemically noble compared to the core material. become,
Since the corrosion protection of the core material is impaired, its content is set at 0.03 to 0.2%.

(c) Mg The Mg component has a getter action that destroys the natural oxide film on the surface of the brazing material, prevents reoxidation, and further improves the fluidity of the brazing material, so it is included as necessary. However, if the content is less than 0.3%, the desired effect cannot be obtained, while if the content exceeds 2%, not only the processability will decrease, but also the furnace failure due to the evaporation of Mg. Since internal contamination becomes significant, the content was reduced to 0.3
It was set at ~2%.

〔Example〕

Next, the Al alloy brazing sheet of the present invention will be specifically explained using examples.

By a normal melting method, AfI alloys 1 to 8 for core materials having the compositions shown in Table 1, A for core materials of the present invention, and
N alloys A-H and conventional brazing filler metals Table 1 Al alloys b were melted and cast under normal conditions to form ingots, which were then subjected to homogenization treatment. Although not shown in Table 1, these Al alloys all contain unavoidable impurities such as Cu: 0.01% or less, Mn:
0.01% or less, Mg: 0.01% or less.

Zr: 0.01% or less, Cr: 0.01% or less,
It contains Zn: 0.01% or less and Fo: 0.35% or less.

Next, after solidifying Ag alloys 1 to 8 for core material, hot rolling was performed to form a hot rolled plate with a thickness of 8 mm (however, Al alloy 3 for core material had a thickness of 9 mm), and Al alloy for brazing material After solidifying in the same way, both were hot-rolled to form a hot-rolled plate with a thickness of 911I11, further cold-rolled to form a cold-rolled plate with a thickness of 1, and then the core material Ag Both sides of hot-rolled alloy sheet (A for core material)
In the case of a hot-rolled plate of l1 alloy 3, the cold-rolled plate of the aluminum alloy for brazing filler metal is superimposed on one side according to the combinations shown in Table 2, and this is hot-rolled to a thickness of 2 mm. The Al alloy brazing sheets 1 to 8 of the present invention and the conventional A47 alloy brazing sheet 1 are prepared by applying appropriate intermediate annealing and cold rolling.
-8 were produced, respectively.

Next, from the various A and Q alloy brazing sheets obtained as a result, two test pieces each having dimensions of 280 mm in length x 40 mm in width were cut out, and each was cut into L.
Bend it into a shape and place the two sides back to back in a vacuum of 10 torr if the filler metal contains Mg, or 1 atm (7 (loto)) if the filler metal does not contain Mg.
Brazing was carried out in a N2 gas atmosphere of rr), with the temperature = 600°C maintained for 10 minutes, and after brazing, the test materials were subjected to an acidic salt spray test for 500 hours, and the back-to-back parts were The maximum corrosion depth of the formed fillet portion and the maximum pitting depth on surfaces other than the fillet forming surface were measured. The measurement results are shown in Table 2. Table 2 also shows the potential after brazing the core material and brazing material.

[Effects of the Invention] From the results shown in Table 2, in the Al alloy brazing sheets 1 to 8 of the present invention, the potential difference between the core material and the brazing material was small, and the brazing material well protected the core material from corrosion. The corrosion resistance of the fillet portion formed by the brazing filler metal is further improved, whereas in the conventional Ag alloy brazing sheets 1 to 8, the potential difference between the core material and the brazing filler metal is large.
Although there is no problem with corrosion prevention by the brazing filler metal in the core material, it is clear that the corrosion of the fillet portion increases further.

As mentioned above, the AJ alloy brazing sheet of the present invention has excellent corrosion resistance in the fillet portion formed when it is brazed, and therefore it is particularly used in the manufacture of heat exchangers such as laminated structure doron cup type heat exchangers. in case of,
Since the fillet portion with high pressure resistance can be maintained for an extremely long period of time, it has industrially useful properties such as extending the service life of the heat exchanger.

Claims (1)

[Claims] (1) Cu: 0.1-0.7%, Mn: 0.3-1.5
%, Si: 0.7-1.3%, and further contains Mg: 0.05-0.2%, Zr: 0.03-0.15
%, Cr: 0.03-0.2%. Cu: 0.03~0.2%, Si: 7~ on one or both sides of an Al alloy core material having a composition containing one or more of the following, and the remainder consisting of Al and unavoidable impurities. 12%, with the remainder consisting of Al and unavoidable impurities (wt%) for a heat exchanger with excellent corrosion resistance in the fillet forming part.
Alloy brazing sheet. (2) Cu: 0.1-0.7
%, Mn: 0.3-1.5%, Si: 0.7-1.3%
, and further contains Mg: 0.05-0.2%, Zr: 0.03-0.15
%, Cr: 0.03 to 0.2%, Cu: on one or both sides of an Al alloy core material having a composition of: 0.03 to 0.2%, Si: 7 to 12%, further contains Mg: 0.3 to 2%, and the remainder is Al and unavoidable impurities (wt%). Al for heat exchanger with excellent corrosion resistance of fillet forming part formed by cladding with Al alloy brazing material with
Alloy brazing sheet.