JPH04246141A - Copper-base alloy for heat exchanger - Google Patents

Abstract

PURPOSE:To provide a copper-base alloy for heat exchanger capable of meeting the recent demands in the industry for the lightening the weight of automobiles, etc., and its attendant necessity for making parts quality highly reliable. CONSTITUTION:The copper-base alloy, which has a composition consisting of, by weight, 15.6% Zn, 1.10% Si, and the balance Cu with inevitable impurities and also has 0.025mm crystalline grain size, shows various characteristics of 40.7kgf/mm<2> tensile strength, 62.8% elongation, and 14.0mm Erichsen value and can suitably be used for the material for manufacturing heat exchangers.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a copper-based alloy for heat exchangers, and more particularly to a copper-based alloy that is suitable and highly reliable as a manufacturing material for automobile radiators or various industrial or household heat exchangers. .

0002

BACKGROUND OF THE INVENTION Copper-based alloys have heretofore been used in automobile radiators and various industrial and domestic heat exchangers. In the case of automobile radiators, they are mainly used for the tanks, plates, tubes, and fins that make up the radiators.In particular, for tanks, plates, and tubes, materials such as Class 1 brass or Class 2 brass, which have excellent strength and formability, are used. A soft copper-based alloy was used.

[0003] In recent years, in the automobile industry, there has been a strong desire for lighter automobiles and more reliable materials, and efforts have been made to make individual parts of automobiles lighter and more reliable.

[0004] However, soft brass materials such as Class 1 brass or Class 2 brass used in the above-mentioned automobile radiators are susceptible to dezincification corrosion and stress corrosion cracking, so reliability is poor. There was a problem with the surface. Furthermore, in order to reduce weight, there has been a strong demand for further improvement in strength while satisfying the required moldability.

Dezincing corrosion and stress corrosion cracking that occur in automobile radiators using brass materials as members are considered to be due to the following reasons. Normally, radiators are forcibly cooled by air, so the SO2 in the air is
, NOx, Cl2 gas, etc. cause corrosion. Additionally, the addition of snow-melting materials (such as NaCl) and moisture into the engine room creates an environment that is prone to corrosion. Furthermore, the cooling medium is refluxing inside the radiator, and when used for a long period of time, corrosion products and dirt are generated. Impact corrosion causes dezincification corrosion, intergranular corrosion, pitting corrosion, etc. to occur from the inside, reducing the lifespan of the radiator.

Furthermore, each part of the radiator suffers from stress corrosion cracking due to residual stress from molding and stress from caulking during assembly, combined with a corrosive environment.
This could lead to serious defects such as liquid leakage.

[0007]

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art as described above, and provides a heat-resistant material that has excellent corrosion resistance such as stress corrosion cracking resistance, and has excellent strength, moldability, and solderability. The purpose is to provide a copper-based alloy for exchangers.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors conducted intensive research and found that they could improve the quality of brass by regulating the Zn component contained in conventional brass materials and further adding an appropriate amount of Si. It has been discovered that corrosion resistance, particularly stress corrosion cracking resistance, can be significantly improved, and strength and moldability can be improved, and the present invention has been achieved.

That is, the present invention provides Z
This relates to a copper-based alloy for heat exchangers, containing n: 7 to 22%, Si: 0.2 to 2.5%, and the balance consisting of Cu and inevitable impurities. This copper-based alloy has a grain size of 0.
．． 005 to 0.035 mm, and when this condition is satisfied, it becomes more preferable as a copper-based alloy for heat exchangers. Further, it is possible to obtain an alloy having a tensile strength of 33 kgf/mm2 or more. Furthermore, it is possible to obtain an alloy with an Erichsen value of 11 mm or more. When all of these conditions are met, it becomes the optimal alloy for heat exchangers, but depending on the purpose of the alloy, it is not always necessary to satisfy all of the conditions, so manufacturing must be done depending on the purpose and considering economic efficiency. Choose a condition. The present invention further provides a core plate member for a heat exchanger that is mainly made of the above copper-based alloy.

0010

[Function] The reasons for limiting the alloy components of the present invention and their functions will be explained below.

[0011] Zn has the effect of improving strength, moldability, and heat-resistant adhesion of soldered parts, and these effects are not sufficient when the Zn content is less than 7% by weight. If it exceeds 22%, dezincification corrosion and stress corrosion cracking are likely to occur even in the presence of Si. Therefore, the Zn content in the present invention is 7 to 22% by weight (
Preferably it is in the range of 13 to 17% by weight).

[0012] Like Zn, Si has the effect of improving strength and formability, as well as dezincification corrosion resistance and stress corrosion cracking resistance. If the content is less than 0.2%, it is not sufficient, and if it exceeds 2.5%, the hot and cold workability will be significantly reduced, and the solderability will further deteriorate. Therefore, the content of Si in the present invention is 0.2 to 2
．． 5% by weight (preferably 0.3-1.2% by weight)
The range of Incidentally, as the Zn content increases, strength and moldability improve, and it becomes advantageous in terms of price, but it is necessary to increase the amount of Si added in order to suppress dezincification corrosion and stress corrosion cracking.

Further, when the Zn content is reduced, the susceptibility to dezincification corrosion and stress corrosion cracking is reduced, but the strength is insufficient, so the amount of Si must be increased. Therefore, Si
The content is closely related to the Zn content. Increasing the Si content may have disadvantages in manufacturing, such as a decrease in flowability during casting, an increase in deformation resistance or deformability during hot and cold working, or the formation of a film during heat treatment. Become. Therefore, Zn that satisfies the characteristics with the smallest amount of Si added
The optimal amount of is found. The optimal amount of Zn is 13-17%,
The amount of Si added is in the range of 0.3 to 1.2%. Therefore, the preferred Zn content is 13 to 17%, and the S
The i content ranges from 0.3 to 1.2%.

[0014] The finer the grain size, the better the strength and stress corrosion cracking resistance, but the lower the moldability. Therefore, 0.005mm or more is desirable, and 0.035mm
If it exceeds this, the strength and stress corrosion cracking resistance will decrease. In addition, rough skin is more likely to occur after molding. Therefore, the grain size is in the range of 0.005 to 0.035 mm.

[0015] Also, in order to cope with the thinning of radiator tanks, plates, and fins, the tensile strength was increased to 33 kgf/
mm2 or more and Erichsen value of 11 mm or more are required. Furthermore, the tensile strength is 37kg in response to the recent demand for weight reduction.
f/mm2 or more and an Erichsen value of 13 mm or more are preferable. Unless we improve both strength and formability,
Achieving weight reduction of the radiator becomes difficult. Furthermore, the above-mentioned improvement in corrosion resistance allows for thinner walls.

[0016] The present invention will now be explained in more detail with reference to Examples. However, the scope of the present invention is not limited by the following examples.

[0017]

[Example] Copper-based alloy samples 1 to 12, the chemical composition values (wt%) of which are shown in Table 1, were melted using a high frequency induction melting furnace and cast into ingots of 40 mm x 40 mm x 140 mm. In this case, the melting and casting atmosphere was completely shielded with an inert gas.

[0018] Next, each ingot is 40 mm x 40 mm x 15
The slab was cut into pieces of 5 mm in size, and the slab was hot rolled at 810°C to obtain a hot rolled plate with a thickness of 5 mm. After face cutting, it was cold rolled to a thickness of 1.5 mm and annealed at a temperature of 500 to 550°C. After pickling, it was cold rolled to a thickness of 0.4 mm, and the grain size was reduced to 0 at a temperature of 400 to 600 °C.
．． It was annealed to a thickness of 0.025 mm. However, only sample 8 was annealed at 650℃ and the grain size was 0.060m.
m (the crystal grain size was determined with reference to JIS H 0501).

The obtained plate material was pickled and then buffed to adjust the surface roughness to Rmax 0.0015 mm. Using this as a test material, the tensile strength, elongation, Erichsen value, and stress corrosion cracking resistance were examined, and the results are also listed in the same table.

[0020] Measurement of tensile strength, elongation and Erichsen value is performed according to JISZ 2244 and JIS Z22, respectively.
41, and JIS Z 2247 (Method A). Regarding stress corrosion cracking resistance, commercially available ammonia water (25 to 28%) was diluted with pure water, and the solution was put into the bottom of a desiccator to make it about 13%, and then the stress in the center was 9 kgf.
The test piece bent into an arch shape so as to have an angle of 1/2 mm was placed in a desiccator together with its holder and kept at room temperature.

[0021] After each predetermined period of time, these test pieces were taken out of the desiccator, and the surface of the test pieces was examined using a stereomicroscope.
It was observed under 0x magnification, and the crack generation time was measured.

[0022] Furthermore, after exposing the tensile test piece to an ammonia atmosphere for 1000 minutes, a tensile test was conducted, and the degree of intergranular corrosion was evaluated by measuring the tensile strength and elongation.
These results are also listed in the same table.

[0023]

[Table 1] From the results in the same table, the following was found. No. 1, which is a preferred embodiment of the present invention. 1~No. Alloy No. 5 has excellent tensile strength, elongation, and Erichsen value, and also has good stress corrosion cracking resistance, and is therefore an extremely excellent alloy as a copper-based alloy for heat exchangers.

On the other hand, comparative alloy No. 1 containing less Si than the amount specified in the present invention. 6 has low strength and elongation;
Comparative alloy No. 1 has poor stress corrosion cracking resistance and conversely contains more Si than the specified amount. No. 7 could not be manufactured because cracks occurred during cold rolling. In addition, comparative alloy No. 1 with a small amount of Zn. Comparative alloy No. 9 has low strength, elongation, and Erichsen value, and conversely contains more Zn than the specified amount. 10 is
Poor stress corrosion cracking resistance.

Comparative alloy No. 1, which is a conventional brass material containing no Si. 11 and no. It can be seen that No. 12 is inferior in both strength and stress corrosion cracking resistance.

[0026] Zn amount and Si within the range specified in the present invention
Even if the grain size is too large, alloy No.
Although No. 8 is superior in strength, workability, and stress corrosion cracking resistance to other comparative alloys, it is insufficient as a copper-based alloy for heat exchangers.

[0027]

[Effects of the Invention] As mentioned above, the copper-based alloy according to the present invention has
It has excellent properties for use in heat exchangers, such as strength, moldability, and resistance to stress corrosion cracking, and can meet the recent demands for lighter weight and higher reliability heat exchangers in various fields.

Claims (4)

[Claims] [Claim 1] Zn: 7 to 22% by weight
, Si: 0.2 to 2.5%, the balance being Cu and inevitable impurities. [Claim 2] Crystal grain size is 0.005 to 0.035.
The copper-based alloy for heat exchangers according to claim 1, which is mm. 3. The copper-based alloy for a heat exchanger according to claim 2, which has a tensile strength of 33 kgf/mm 2 or more and an Erichsen value of 11 mm or more. [Claim 4] Zn: 7 to 22% by weight
, Si: 0.2 to 2.5%, the balance being Cu and unavoidable impurities.