JPS61243146A - Heat exchanger having corrosion preventing property - Google Patents

Abstract

PURPOSE:To improve the corrosion preventing property of a heat exchanger by using an Al alloy contg. specified amounts of Si, Fe, Cu, Mn and Zn and having a specified grain size as the material of the constituent members of the heat exchanger. CONSTITUTION:The constituent members of a heat exchanger are made of an Al alloy having a composition consisting of, by weight, <0.6% Si, <0.7% Fe, <0.25% Cu, 1-1.5% Mn, 0.25% Zn and the balance Al with inevitable impurities or further contg. 0.8-1.3% Mg. The Al alloy has 1,500-5,000mum grain size by recrystallization heat treatment after cold drawing.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a heat exchanger having anti-corrosion properties, and more specifically, to a heat exchanger having anti-corrosion properties, in particular, to a heat exchanger having a crystal grain size of 1500 to 5000μ after heating recrystallization treatment of an aluminum alloy material as a constituent member thereof. This is intended to impart anti-corrosion properties to the heat exchanger.

C. Prior Art and Problems to be Solved by the Invention] Conventionally, aluminum alloys for heat exchanger construction have generally been made as fine as possible to improve their strength, and have been painted or chemically coated depending on the conditions of use. It is used in a state where it has anti-corrosion properties through treatments such as treatment, metal spraying, plating, or metal diffusion coating, but metals such as dislocations and segregation occur at the grain boundaries of the structure whose grain size has been refined. There are many microstructural defects, so the grain boundaries are easily corroded, and pitting corrosion occurs in those areas when used as a heat exchanger.

Furthermore, the various treatments described above to impart corrosion resistance have not yet been able to completely prevent pitting corrosion of aluminum alloy materials in heat exchangers.

[Means and effects for solving the problem] The present invention improves the grain size of the aluminum alloy structure of the heat exchanger component to 150.
By setting the thickness to 0 to 5000 μm, the purpose is to reduce the above-mentioned grain boundaries, thereby reducing the chance of pitting corrosion occurring, and to ensure anticorrosive properties that delay the progress of pitting corrosion even if it occurs.

That is, in the present invention, the constituent members include S'i 0.6% or less, Fe 0.7% or less, Cu 0.25% or less, Mn
1.0-1.5%, Zn 0.25% or less, Mg
An alloy containing or not containing 0.8 to 1.3%, the balance A1 and unavoidable impurities, and having a crystal grain size of 1500 to 5000 after heating recrystallization treatment following cold stretching and cold working.
The subject matter is a patented heat exchanger characterized by being made of an aluminum alloy material with μ.

In the recrystallized state, the crystal grain size specified in the present invention is 1500 to 5.
000μ can be obtained by controlling the recrystallized grain size by utilizing the following properties of aluminum alloy.

Generally, when an aluminum alloy is subjected to cold working such as intense rolling or drawing, and then heated and recrystallized, the grain size becomes coarse. That is, to obtain a large grain size, the degree of cold working may be reduced, and to obtain a small grain size, the degree of cold working may be increased.

In the present invention, the reason why the crystal grain size in the recrystallized state of the aluminum alloy material as a constituent member is limited as described above is as follows. The larger the crystal grain size, the more likely it is that corrosion will be suppressed, but in the present invention, as is clear from the description of the test examples described later, a grain size of 1500 to 5000μ has been confirmed to have a remarkable effect on corrosion resistance. The range of

In addition, the alloy components of the constituent members are limited as described above.
From the original purpose of the invention, it is not particularly necessary to limit the alloy components, but here, aluminum alloys commonly used as materials for heat exchangers, specifically 30
03 (excluding those without addition of Si and Zn),
3203.3004 (JIS standard) and narrowed the scope.

(Example) The following examples demonstrate that the aluminum alloy material according to the present invention exhibits remarkable corrosion resistance compared to the conventionally used materials with fine grain size. The results of a comparative corrosion resistance test conducted for the invention will be described.

Contents of the comparative test (1) Test piece The test piece is a plating sheet for an aluminum alloy heat exchanger with fins vacuum brazed and the fins are cut out leaving only the brazed part), with dimensions of 100 m x 400 m x provisional thickness One of the test pieces had a fine crystal grain size for both the plating sheet and the fin, and the other had a coarse grain size for both.

(2) Corrosion test Corrosion test was carried out at 40°C, Cl. P at COOH}
The product was immersed in a NaC 12 solution adjusted to a temperature of 13 for 30 minutes, then lifted out of the solution and dried with warm air at 50°C for 30 minutes, a process repeated for one month! ! continued.

(3) Test results After the corrosion test was completed, several locations where corrosion was particularly severe were selected from each test piece, cut out as test pieces, and the cross section was polished and the corrosion status was investigated under a microscope.

Regarding the above table, the first
The micrographs shown in the figure and Fig. 2 clearly show the corrosion state.

As is clear from the above test results, the heat exchanger using aluminum alloy material with increased grain size based on the present invention is different from the conventional heat exchanger using aluminum alloy material with fine grain size as a component. It can exhibit outstanding anti-corrosion properties compared to ceramics.

[Brief explanation of drawings]

Figures 1 and 2 are micrographs (magnification x 20) of the cross sections of test piece numbers 1 and 2 used in the corrosion test, respectively.
This is to show the corrosion status of each type. Procedural amendment (method) May 1986 IG Date Patent Application No. 38058 2゜ Name of the invention Heat exchanger with anti-corrosion properties 3゜ Relationship with the case of the person making the amendment Patent applicant address Amagasaki, Hyogo Prefecture 2-6 Hondori, Nagasu, Ichinishi Name: Sumitomo Precision Industries Co., Ltd. Representative: Nobuji Seki 4, Agent 6: Document certifying the power of representation subject to amendment, "Detailed description of the invention" in the specification
column, "Brief explanation of the drawing" column, Drawing 7, contents of amendment il1 Submit a document certifying power of attorney as attached. (2) Lines 8 to 7 from the bottom of page 6 of the specification “Figure 1...
...It's raining. "Figures 1 and 2 are diagrams of the corroded parts of specimen 1.2, respectively, based on microscopic observation, and the difference in the corrosion status shown in the table above is clear from a comparison of both figures. ”. (3) The brief explanation of the drawings on page 7 of the specification will be amended as follows. "Figures 1 and 2 are diagrams of the cross-section of the corroded part of test specimen 1.2 based on microscopic observation." (4)
Correct the drawing as shown in the attached sheet.

Claims (1)

[Claims] (1) Components include Si 0.6% or less, Fe 0.7% or less, Cu 0.25% or less, Mn 1.0-1.5%, Zn
An alloy containing 0.25% or less, containing or not containing 0.8 to 1.3% Mg, and the balance consisting of Al and unavoidable impurities, the crystal grain size after heating recrystallization treatment following cold stretching A heat exchanger having anticorrosion properties characterized by being made of an aluminum alloy material with a thickness of 1500 to 5000μ.