JPH06330211A - Heat resistant copper alloy - Google Patents

Abstract

PURPOSE:To produce a heat resistant Cu alloy excellent in brazability and suitability to wettability of a brazing filler metal and having high heat resistance by incorporating each a specified percentage of Ni, Ti, Co and Zn into Cu. CONSTITUTION:This heat resistant Cu alloy consists of, by weight, 0.1-4.0%, preferably 0.4-0.8% Ni, 0.05-0.4%, preferably 0.1-0.3% Ti, 0.05-1.0%, preferably 0.1-0.3% Co, 0.01-1.0% Zn and the balance Cu with ineviatble impurities. About <=0.2%, in total, of elements such as B, Cr, Zn, Mg and Sn are allowed to be contained as the inevitable impurities. This Cu alloy has high mechanical characteristics and durability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant copper alloy which has excellent brazing properties and wettability and spreadability of the brazing material, and does not coarsen crystal grains due to heat of brazing, etc., and has high heat resistance. .

[0002]

2. Description of the Related Art Conventionally, phosphorous deoxidized copper has been generally used for can bodies and pipes of heat exchangers such as bath kettles and water heaters. Since these cans and pipes are assembled by welding or brazing, the materials used for them must have good weldability and brazeability, and because they are components of heat exchangers, they must have good thermal conductivity. Good and
Even if heating and cooling are repeated, it is necessary that fatigue failure does not occur in the brazed portion and the welded portion due to the load of thermal stress. It is known that phosphorous deoxidized copper is relatively weak against repeated thermal stress and that fatigue failure easily occurs in the brazed portion and the welded portion.

1 (a) and 1 (b) are a schematic front view and a side view of a general heat exchanger, respectively. A plurality of pipes 3 are provided between the pair of can bodies 1a and 1b that are spaced apart from each other in the up-down direction. The pipes 3 connect the two to each other. The fins 2 for heat dissipation are brazed to these pipes 3. Has been done. In such a heat exchanger, cracks may occur in the brazing parts A, B, C and in the vicinity thereof due to repeated heating and cooling. This is because the brazing parts A, B, C and their neighboring crystal grains are coarsened due to the heat during brazing to reduce the resistance to fatigue, and at the same time places where these parts receive large structural stress. This is because the thermal stress due to the difference in thermal expansion between the pipes is repeatedly applied due to the temperature difference caused by the non-uniform heating during use, and fatigue fracture occurs. Conventionally, phosphorus deoxidized copper, which has been used as a material for a heat exchanger, has the drawback that crystal grains are likely to be coarsened and the above-mentioned cracks are likely to occur due to the characteristics of the material. Therefore, as a copper alloy for a heat exchanger, which has excellent heat resistance and whose crystal grains are less likely to coarsen, for example, C
u-1.9Fe-0.4Co-0.03P-0.05Z
n alloy (Japanese Patent Laid-Open No. 04-272148) and Cu-0.
9Ni-0.3Ti-0.2Sn alloy (Japanese Patent Laid-Open No. 62-0
06733) has been proposed. These copper alloys for heat exchangers are superior in tensile strength and proof stress to phosphorus deoxidized copper, have a fine crystal grain size, and are excellent in fatigue properties. Moreover, since the wetting and spreading property of the brazing material and the adhesiveness of the solder are equal to or higher than those of the phosphorous deoxidized copper, it is extremely useful for improving the reliability of the heat exchanger.

[0004]

However, in recent years,
In order to perform more accurate temperature control, the heat exchanger is required to quickly reach the target temperature of the heat exchange medium by rapid heating and rapid cooling. Therefore, materials for heat exchangers are required to have high thermal conductivity, in other words, high electrical conductivity. JP 04-272
As described above, the copper alloys disclosed in JP-A No. 148 and JP-A-62-006733 have fine crystal grains and are excellent in characteristics such as strength and solder adhesion, but are not as good as phosphorus deoxidized copper. Then, there is a drawback that the conductivity is low.

The present invention has been made in view of the above problems, and is excellent in electrical conductivity after heat treatment assuming brazing, and also has mechanical properties, brazing / wetting spreadability of solder and solder adhesion. It is an object of the present invention to provide a heat-resistant copper alloy that is excellent in heat resistance, can suppress the coarsening of crystal grains due to heat such as brazing and welding, and has high durability against fatigue fracture due to repeated thermal stress.

[0006]

A heat-resistant copper alloy according to the first invention of the present application comprises 0.1 to 4.0% by weight of Ni and 0.0
5 to 0.4% by weight of Ti, 0.05 to 1.0% by weight of Co, 0.01 to 1.0% by weight of Zn, and the balance Cu and inevitable impurities Is characterized by.

The heat-resistant copper alloy according to the second invention of the present application is
4 to 0.8 wt% Ni and 0.1 to 0.3 wt%
Ti and 0.1 to 0.3 wt% Co, 0.01
To 1.0 wt% Zn, and the balance being Cu and inevitable impurities.

[0008]

The function of the heat-resistant copper alloy according to the present invention and the reason for limiting the composition will be described below.

Ni Ni is an element that can improve the tensile strength, yield strength and hardness of a copper alloy when added together with Ti described later. However, if the Ni content is less than 0.1% by weight, the effect of improving tensile strength, proof stress and hardness cannot be sufficiently obtained even if 0.05 to 0.4% by weight of Ti is added. Further, when the Ni content exceeds 4.0% by weight, the effect of improving the tensile strength, proof stress and hardness commensurate with the content cannot be obtained, which is not only wasteful but also the workability is deteriorated and the conductivity is deteriorated. The rate also decreases. Therefore, the Ni content is 0.1
To 4.0% by weight. By setting the Ni content to 0.4 to 0.8% by weight, the tensile strength, the proof stress, the hardness and the electrical conductivity can all be made extremely good.

Ti Ti is an element that can improve the tensile strength, yield strength and hardness of a copper alloy when added together with Ni and Co described later. However, since the affinity between Ti and Ni is stronger than the affinity between Ti and Co, when the Ti content is less than 0.05% by weight, the Co remaining without combining with Ti is Cu. Excessive solid solution in the matrix leads to a decrease in conductivity. On the other hand, if the Ti content exceeds 0.4% by weight, Ti is easily oxidized and a large amount of Ti oxide is entrained in the molten metal, which significantly deteriorates the soundness of the ingot of the heat-resistant copper alloy. Therefore, the Ti content is set to 0.05 to 0.4% by weight. By setting the Ti content to 0.1 to 0.3% by weight, the tensile strength, proof stress, hardness, conductivity, and soundness of the ingot can all be made very good.

Co Co is an element that can improve the tensile strength, yield strength and hardness of a copper alloy when added together with Ti. Further, Co is also an element necessary for suppressing the coarsening of crystal grains. That is, Co contains about 800 to 900
Even in the brazing process at a temperature of ℃, it has the effect of suppressing the growth of crystal grains, maintaining a fine structure, and improving the thermal fatigue resistance. However, if the Co content is less than 0.05% by weight, such an effect cannot be obtained, and if the Co content is more than 1.0% by weight, the excessive amount of solid solution Co in the Cu matrix causes copper to dissolve. The conductivity of the alloy is reduced. Therefore, the Co content is 0.05 to 1.0% by weight.
By setting the Co content to 0.1 to 0.3% by weight, the tensile strength, the proof stress, the hardness, the heat resistance and the electrical conductivity can all be made extremely good.

Zn Zn has the effect of improving the adhesion of the plating layer and improving the wettability of the solder when supplementary repair such as Sn plating or solder plating is performed after brazing. Zn
If the content is less than 0.01% by weight, these effects cannot be sufficiently obtained. On the other hand, Zn content is 1.0
When it exceeds the weight%, the brazing property and the electric conductivity decrease. Therefore, the Zn content is 0.01 to 1.0% by weight.
And

It is considered that elements such as B, Cr, Zr, Mg and Sn are mixed as unavoidable impurities from the scrap material into the heat resistant copper alloy. When the total content of these elements is 0.2% by weight or less, there is no possibility of exerting a great influence on the physical properties of the heat resistant copper alloy of the present invention, and thus the inclusion of such inevitable impurities is allowed.

[0014]

EXAMPLES Next, the results of manufacturing the heat-resistant copper alloys according to the examples of the present invention and testing the characteristics thereof will be described in comparison with comparative examples that depart from the claims of the present application.

First, using a Cryptor furnace, the following Table 1 is used.
The alloy raw materials of Examples 1 to 9 having the composition shown in Table 1 and the alloy raw materials of Comparative Examples 1 to 11 having the compositions shown in Table 2 below were melted in the atmosphere under the flux coating. Next, a graphite book mold is used to cast these melts to a thickness of 50
An ingot having a size of mm, a width of 80 mm, and a length of 200 mm was obtained.
Then, both front and back surfaces of these ingots were chamfered by 5 mm each. Then, these ingots were heated to a temperature of 880 ° C for 15 mm.
After hot-rolling to a thickness of 1, these rolled materials were put into water and rapidly cooled. Then, after removing the oxide scale of these rolled materials, cold working is performed to obtain a thickness of 0.5.
It processed into the board material of mm, and used these board materials as a test material. In addition, Comparative Example 6 in which the content of Ti exceeds 1.0% by weight,
Since many internal defects occurred due to the inclusion of oxide during casting, the subsequent steps were not performed.

Since the heat exchanger member needs to be subjected to processing such as bending and flange forming (deep drawing),
Generally, a soft material (O material or 1 / 2H material) of phosphorus deoxidized copper (C1020 alloy) is used. Therefore, phosphorus-deoxidized copper was soft-treated and prepared as Comparative Example 9. Further, JP-A-04-272148 and JP-A-62-00673.
The alloys disclosed in No. 3 are Cu-1.9Fe-, respectively.
0.4Co-0.03P-0.05Zn alloy (Comparative Example 1
0) and Cu-0.9Ni-0.3Ti-0.2Sn alloy (Comparative Example 11) were prepared.

[0017]

[Table 1]

[0018]

[Table 2]

Next, assuming actual brazing conditions, each of the test materials of Examples 1 to 9 and Comparative Examples 1 to 11 was heat-treated at a temperature of 830 ° C. for 70 minutes, and each heat-treated material was heat-treated. The characteristics were investigated. However, each property was measured by the following test methods.

Tensile Test The tensile strength, proof stress and elongation were measured using test pieces of JIS No. 5 standard cut out from each test material in parallel with the rolling direction.

Hardness test The hardness was measured using a Vickers hardness tester under a load of 2 kg.

Fatigue test Using a thin plate fatigue tester, for each test piece with a width of 10 mm cut out from each test material of Examples and Comparative Examples,
Repeated swinging stress was applied under the condition that the cycle was 60 Hz and the stress amplitude was 15 kgf / mm ² . Then, the number of times until the test piece was broken by the repeated stress was measured.

Brazing (wetting and spreading) test FIG. 2 shows an apparatus used for measuring brazing. In this device, the airtight tube 4 is installed horizontally in the tubular furnace 5,
Both ends of the airtight tube 4 are closed by plug members 7 and 8 so that the inside of the airtight tube 4 is kept airtight. On the other hand, a support rod 12 for moving the test table 11 in the longitudinal direction in the airtight tube 4 is inserted into the stopper member 7, and the test table 11 can be operated from outside the furnace via the support rod 12. It has become. Further, an N ₂ gas introducing portion 9 is provided on the upper wall of the end of the airtight tube 4 on the plug member 7 side, and the other plug member 8 is provided.
Is provided with a discharge portion 10 for N ₂ gas. And
At the center of the airtight tube 4, a water cooling zone 6 is provided for cooling the test member in the airtight tube by injecting water on the outer periphery of the airtight tube 4. The test member 13 cut out from the example and the comparative example is placed on the test table 11.

3 (a) and 3 (b) are a front view and a side view showing the test member 13, respectively. According to Examples 1 to 9 and Comparative Examples 1 to 11, a U-shape is formed in a side view and the length is 3
A 00 mm test piece 20 is formed. A brazing material 21 having a columnar shape is placed on the test piece 20, and the test member 1
Make up 3. The brazing material 21 has a diameter of 2.5 mm and a length of 30 mm, and has a composition of BCuP-2 (Cu containing 7 to 7.5% by weight of P).

The test table 11 on which the test member 13 was placed was inserted into the airtight tube 4, the plug member 7 was fitted into the end of the airtight tube 4, and then N ₂ gas was introduced into the airtight tube 4. Next, the test member 13 was moved to the heater position of the tubular furnace 5, and heat treatment of heating at a temperature of 830 ° C. for 10 minutes was performed to melt the brazing filler metal 21. Next, the test member 13 was moved to the water cooling zone 6 and cooled to solidify the brazing material 21. And brazing material 21
The brazing property was evaluated from the ratio of the initial length of the above and the length after the solidification (wetting and spreading length).

Crystal grain size The crystal grain size was measured with an optical (metal) microscope using a scale.

Adhesion of Solder First, from each of the test materials of Examples 1 to 9 and Comparative Examples 1 to 11, the thickness was 0.8 mm, the width was 25 mm, and the length was 50 mm.
The test pieces were cut out and the bath temperature was 230
It was immersed in a solder bath at ℃ for 5 seconds. The composition of the solder used in the solder bath is 60 wt% Sn and 40 wt% Pb. As the flux, a weakly active flux (Alpha # 611; manufactured by Alpha Metal) was used.
Next, after heating for 100 hours in the atmosphere at a temperature of 175 ° C., reciprocal bending was performed at a bending radius of 2 mm and an angle of 180 °, and the presence or absence of solder peeling was examined.

Conductivity Using test pieces having a width of 10 mm and a length of 300 mm cut out from the test materials of Examples 1 to 9 and Comparative Examples 1 to 11, the electric resistance of these test pieces was measured by a double bridge. It was measured and calculated by the average cross-sectional area method.

The measurement results of each of these characteristics are shown in Tables 3 to 6 below. However, in the column of wettability and spreadability of brazing filler metal, ○ indicates that the wettability and spread length is 3 times or more of the initial length, and that the wettability and spread length exceeds 1.5 times and is less than 3 times the initial length. Is indicated by Δ, and the case where the wet spread length is 1.5 times or less of the initial length is indicated by x.

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Table 5]

[0033]

[Table 6]

As is clear from these Tables 3 to 6,
All of Examples 1 to 9 according to the present invention showed excellent material properties even when heated at a temperature of 830 ° C. for 10 minutes. That is, these material properties have a tensile strength of 1. compared to the phosphorus deoxidized copper (Comparative Example 9) used for the conventional heat exchanger.
4 times or more, proof stress 8 times or more, hardness is 2 times or more, showing excellent characteristics. Further, the crystal grain size is as fine as 20 to 30 μm, and fatigue characteristics are remarkably excellent. Moreover, these Examples 1 to 9 are also excellent in brazing property, and the wet spreadability and the adhesiveness of solder are equal to or higher than those of Comparative Example 9. Further, as compared with Comparative Examples 10 and 11 which are alloys disclosed in JP-A-04-272148 and JP-A-62-006733, respectively, tensile strength, proof stress, hardness,
Excellent in crystal grain size, fatigue characteristics, wettability and spreadability of brazing filler metal, and solder adhesion. Particularly, in Examples 3 to 6 having compositions defined in claim 2 of the present application, the conductivity is 16 to 18% IAC as compared with Comparative Example 10.
S is high, and is 7 to 9% IACS as compared with Comparative Example 11.
high. Therefore, these alloys can obtain high reliability as a material for a heat exchanger.

On the other hand, Comparative Example 1, which has a low Ni content of 0.07% by weight, is inferior to Examples 1 to 9 in tensile strength, proof stress, hardness, fatigue characteristics and electrical conductivity. Comparative Example 5 having a large Ni content of 4.5% by weight also has poor conductivity. Further, the conductivity of Comparative Example 2, which has a low Ti content of 0.01% by weight, is inferior to that of Examples 1 to 9. Furthermore, Comparative Example 3, which has a small Co content of 0.01% by weight, has coarser crystal grains and is inferior in fatigue properties as compared with Examples 1 to 9, and conversely the Co content is 2.1% by weight. %, The conductivity of Comparative Example 7 is inferior. Furthermore, in Comparative Example 4 in which the Zn content is as low as 0.006% by weight, the adhesiveness of the solder is inferior to that in Examples 1 to 9, and conversely, the Zn content is as high as 2.0% by weight. In Example 8, the brazing material has poor wettability and conductivity. Furthermore, Comparative Example 9, which is a conventional phosphorous deoxidized copper, is significantly inferior to Examples 1 to 9 in properties such as proof stress, fatigue properties and solder adhesion. JP-A-04-272148 and JP-A-62-006733.
Comparative Examples 10 and 11 which are the alloys disclosed in No. 1 have inferior electric conductivity as compared with Examples 1 to 9 as described above.

[0036]

As described above, since the heat-resistant copper alloy according to the present invention contains a predetermined amount of Ni, Ti, Co and Zn, it is different from phosphorus deoxidized copper which is a conventional copper alloy for heat exchangers. While having the same or greater wettability and spreadability of the brazing material, the tensile strength after brazing, the proof stress, the hardness, the grain size and the fatigue characteristics are remarkably excellent, and the conductivity is excellent, and the heat Good conductivity. Therefore, the present invention is extremely useful for improving the reliability of the heat exchanger.

[Brief description of drawings]

1A and 1B are a front view and a side view showing a general heat exchanger, respectively.

FIG. 2 is a schematic cross-sectional view showing a brazing furnace used for a wetting and spreading test of a brazing material.

3 (a) and 3 (b) are respectively a front view and a side view showing a test member used for a wet spread test.

[Explanation of symbols]

 1a, 1b; can body 2; fin 3; pipe 4; airtight tube 5; tubular furnace 6; water cooling zone 7, 8; stopper member 9; gas introduction part 10; gas discharge part 11; test stand 12; support rod 13; Test member 20; Test piece 21; Brazing material A, B, C; Brazing part

Claims (2)

[Claims] 1. A Ni content of 0.1 to 4.0% by weight;
05 to 0.4% by weight of Ti, 0.05 to 1.0% by weight of Co, 0.01 to 1.0% by weight of Zn, and the balance Cu and unavoidable impurities A heat resistant copper alloy. 2. Ni of 0.4 to 0.8% by weight;
1 to 0.3 wt% Ti and 0.1 to 0.3 wt%
Of Co and 0.01 to 1.0% by weight of Zn, with the balance being Cu and inevitable impurities, a heat-resistant copper alloy.