ES2856029T3 - Copper alloy for use in a member for hydraulic works - Google Patents

Abstract

A copper alloy for use in a member for hydraulic works, the copper alloy consisting of: 0.5% by mass or less Ni; 12% by mass or more and 21% by mass or less of Zn; 1.4% by mass or more and 3.0% by mass or less of Sn, with a total content of Zn and Sn being 23.5% by mass or less; 0.005% by mass or more and 0.15% by mass or less of P; 0.05% by mass or more and 0.30% by mass or less of Pb; and the remainder, where the remainder is Cu and unavoidable impurities, where Bi, Si, Al, Sb, Zr, Fe, Mn, Cr, Mg, Ti, Te, Se and Cd are among the elements that constitute the unavoidable impurities.

Description

DESCRIPTION

Copper alloy for use in a member for hydraulic works

Technical field

The present invention relates to a material for use in a member for hydraulic works, which is made of a copper alloy and in which the level of lead leaching does not exceed a stipulated value.

Background of the technique

A cast bronze metal (JIS H5120 CAC406), which has been conventionally used for parts in materials and equipment for hydraulic works and in feed water supply systems, has excellent castability, corrosion resistance, machinability and / or strength. to water pressure and is used for parts in materials and equipment for hydraulic works and in feed water supply systems, and the like in various fields. This cast bronze metal (CAC406) contains 4.0 to 6.0% by weight of lead for high machinability and easy workability characteristics. However, this contained lead has the property of leaching into tap water in contact with it, which does not meet recent regulations for the amount of lead from leaching. Therefore, to reduce the amount of toxic lead leaching, a copper alloy containing reduced lead content or a lead-free copper alloy containing no lead has been examined.

For example, Patent Document 1, as mentioned below, discloses a brass alloy having an adjusted composition containing from 8 to 40% by mass of Zn, from 0.0005 to 0.04% by mass of Zr , from 0.01 to 0.25% by mass of P, at least one or more types from 0.005 to 0.45% by mass of Pb, from 0.005 to 0.45% by mass of Bi, from 0.03 to 0.45% by mass of Se and from 0.01 to 0.45% by mass of Te, and the remainder of Cu and unavoidable impurities. This brass alloy is an alloy in which solid metals and liquid metals mixed in a semi-solid state are solidified and, in the course of their solidification, primary to granular crystals crystallize or there is a solid phase a. Furthermore, it is disclosed that as conditions of other elements, one or more types of 2 to 5% by mass of Si, 0.05 to 6% by mass of Sn, and 0.05 to 3.5% by mass of Al may be contained and, in particular, Zr with coexistence with P is effective in size reduction in the semi-solid state.

On the other hand, patent document 2, as mentioned below, discloses a copper alloy for use in a member for hydraulic works, the copper alloy containing: less than 0.5% by mass Ni in a limited way ; less than the detection limit of Pb; 0.2% by mass or more and 0.9% by mass or less of Bi; 12.0% by mass or more and 20.0% by mass or less of Zn; 1.5% by mass or more and 4.5% by mass or less of Sn; and 0.005% by mass or more and 0.1% by mass or less of P; wherein a total content of Zn and Sn is 21.5% by mass or less, and the remainder is unavoidable impurities and Cu. Furthermore, it is proposed that it is additionally contained 0.0003 to 0.006% by mass of B.

Prior art document

Patent document

Patent Document 1: Japanese Patent No. 5116976

Patent Document 2: Japanese Patent No. 5406405

Documents US2009 / 0294087, US2010 / 0297464 and DE102012013817 also disclose copper alloys. Summary of the invention

Problems to be solved by the invention

Conventionally, as reduced toxic Pb containing copper alloys, a copper alloy containing Bi and Si has been used in substitution for Pb to avoid a reduction in properties such as machinability and resistance to water pressure. On the other hand, in non-lead leaching machine components other than members for hydraulic works and the like, a lead-containing molten bronze metal is often used. In cases where such copper alloys are produced on the same line, if a molten bronze metal containing lead is melted and cast after a lead-free copper alloy containing Bi and Si, the Bi and Si of The lead-free copper alloy produced above remains in a smelting furnace and is mixed into a molten bronze metal for production. In a cast bronze metal product in which these elements are unintentionally mixed, product defects can increase and mechanical properties can be greatly reduced, and therefore elements, such as Bi and Si, are desirably used. as little as possible for the convenience of the place of production.

Also, the alloy of patent document 1 has a problem that in a range in which the Zn content is high, dezincification corrosion is prone to occur, and it has a property that in a range in which the Zn content is high, As long as the Pb content is high, the lead leaching level is not satisfied. On the other hand, since Bi is contained, there has been a recycling problem as described above. Also, if it is in a range where the Zn content is high and the Sn content is low, Zr is contained, the improvement in properties is effectively realized during a casting process that has a small temperature range. solidification, such as solidification from a semi-solid state, whereas if it is in a range in which the Zn content is low and the Sn content is high, Zr is contained and in a casting process of a metal, which is not in a semi-solid state but completely liquid, in a mold, the temperature range until solidification is large, so that a Zr compound can be generated and shrinkage cavities can be facilitated to reduce mechanical properties .

On the other hand, in the alloy of patent document 2, since Bi is contained, there has been a recycling problem as described above.

Accordingly, an object of the present invention is to provide a copper alloy for use in a member for hydraulic works, which has adequate mechanical properties and moldability, while not only inhibiting the leaching of lead but also maintaining recyclability.

Means to solve problems

The present invention has solved the aforementioned problems by a copper alloy for use in a member for hydraulic works, the copper alloy consisting of: 0.5% by mass or less Ni; 12% by mass or more and 21% by mass or less of Zn; 1.4% by mass or more and 3.0% by mass or less of Sn, with a total content of Zn and Sn being 23.5% by mass or less; 0.005% by mass or more and 0.15% by mass or less of P; 0.05% by mass or more and 0.30% by mass or less of Pb; and the rest, where the rest is Cu and unavoidable impurities. Preferably, Bi is limited to be less than the detection limit so that it can be used even when mixed with another alloy in recycling. Meanwhile, even when Bi is less than the detection limit described below, if Pb is 0.30 mass% or less, property improvement effects, such as machinability, may occur due to the addition of Pb, as long as the leachate lead quantity regulations are met. Furthermore, the Zn and Sn values are adjusted together to be such a mixture that it is capable of exhibiting sufficient mechanical properties without using Bi, which has a great influence on recycling.

On the other hand, Ni is 0.5% by mass or less to be able to inhibit the occurrence of shrinkage cavities.

Furthermore, this copper alloy may contain in a limited way an element that can be mixed in it as another unavoidable impurity. Note that its total amount is required to fall within a range such that it does not inhibit the effects of the present invention, and is preferably less than 1.0% by mass and the content of each of said elements is preferably less than 0, 5% by mass.

Effects of the invention

According to the present invention, it is possible to obtain a copper alloy that also has excellent recyclability and has good mechanical properties by limiting the Pb content and not containing Bi to be able to produce a member for hydraulic works where safety is still more assured.

Brief description of the drawings

Figure 1 is a schematic view of type A defined in JISH 5120 to obtain a sample used in a tensile test evaluation method in the Examples.

Figure 2 is a schematic view of a type 4 specimen defined in JISZ 2241 used in a tensile test evaluation method in the Examples.

Figure 3 is a structural view illustrating the structure of an erosion-corrosion test.

Figures 4 (a) and 4 (b) are views illustrating a spiral-shaped test mold used in a flow test in the Examples.

Figure 5 is a structural view of a stepped mold used in a shrink cavity test in the Examples.

Figure 6 shows photographs illustrating the results of a liquid penetrant test in the Examples. Mode for carrying out the invention

The present invention will now be described in detail. The present invention relates to a copper alloy for use in a member for hydraulic works, which contains Pb in a limited way and is mixed without containing Bi.

In the above-mentioned copper alloy, the Zn content is required to be 12% by mass or more, and preferably 13% by mass or more. Zn content of less than 12% by mass gives as result in the production of curly machining chips that reduce machinability. Meanwhile, the Zn content is required to be 21% by mass or less, and preferably it is 20% by mass or less and more preferably 18% by mass or less. Too high a Zn content results not only in a reduction in mechanical properties, but also in an increase in zinc residue which complicates casting.

In the above-mentioned copper alloy, the Sn content is required to be 1.4% by mass or more, and preferably 2.0% by mass or more. Sn content of less than 1.4% by mass results in the production of crimped machining chips that reduce machinability, similar to the effects of Zn. On the other hand, an oxide film protecting a surface of a member for hydraulic works is removed by the stream of water so that the erosion-corrosion resistance in which the corrosion of the alloy progresses becomes insufficient. Meanwhile, the Sn content is required to be 3.0% by mass or less. This is because too high a Sn content results in reduced elongation and / or shrinkage cavities during sand casting.

In the above-mentioned copper alloy, a total content of Zn and Sn is required to be 23.5% by mass or less, and preferably 21.0% by mass or less. If an amount of solid Zn solubilized in Cu is too high, the solid solubility of Sn is reduced, resulting in a higher concentration of Sn in the residual liquid phase during solidification and, as a result, crystallization of the p phase due to the peritectic reaction. Ultimately, the a or phases, composed of a phases dispersed in hard or phases (Cu ³¹ Sns), are generated between dendrites, resulting in a reduction in tensile strength. Furthermore, the presence of dispersed Bi in the vicinity of the a or phases, during their generation, leads to a synergistic reduction of the mechanical properties of the alloy. Also, when casting is carried out under conditions of low solidification rate, such as when thick-walled casting or sand casting occurs, there is a potential risk that the resulting casting may develop casting defects during casting. final solidification, such as a so-called "tin sweat" defect, a state in which Sn exudes from the alloy surface as if it were sweating, or shrinkage cavity defects. If the total content of Zn and Sn exceeds 23.5% by mass, a reduction in mechanical properties and the appearance of casting defects will be unavoidable.

In the above-mentioned copper alloy, a content of P is required to be 0.005% by mass or more, and preferably 0.01% by mass or more. Since P produces a deoxidizing effect, too low a P content reduces the deoxidizing effect during casting, resulting not only in a greater appearance of gas defects, but also in a lower fluidity of the molten metal due to the oxidation of the metal. molten. On the other hand, the content of P is required to be 0.15% by mass or less, and preferably 0.05% by mass or less. If the water content is too low, the P reacts with the water in the mold to increase the occurrence of gas defects and shrinkage cavity defects in the resulting molding, and its mechanical properties are also reduced. On the other hand, since the above-mentioned copper alloy contains a large amount of Zn, gas absorption is reduced due to the degassing effect of Zn. This enables the production of a molded part with small casting defects, even if the P content is low compared to a representative bronze alloy, JIS H5120 CAC406.

In the above-mentioned copper alloy, the Pb content is required to be 0.05% by mass or more, and preferably 0.07% by mass or more. This is because while Pb is contained slightly to greatly improve machinability, Pb content less than 0.05% by mass results in its insufficient effects. On the other hand, the Pb content is required to be 0.30% by mass or less, and preferably 0.20% by mass or less. Pb is an element whose leaching should be avoided as far as possible, and if the Pb content exceeds 0.30% by mass, it will be difficult to meet a leaching reference value in a leaching test.

In the above-mentioned copper alloy, the Ni content is required to be 0.5% by mass or less. Ni may not be contained but it produces effects that exhibit stable mechanical properties and, at the same time, produces effects of inhibiting the appearance of cavities by shrinkage, which facilitates the production of a suitable molded part. On the other hand, if the Ni content exceeds 0.5% by mass, the machinability tends to decrease.

The above-mentioned copper alloy may contain other impurities as a moiety, in addition to Cu, within a range such that it does not inhibit the effects of the present invention. Note that the content is low and restricted to the point of being contained as unavoidable impurities which are inevitably contained in view of raw material problems and problems during production. This is because if too many unexpected elements are incorporated into the alloy, there is a potential risk that the physical properties of the alloy will deteriorate.

Among the elements constituting the above-mentioned unavoidable impurities, a Bi content is preferably less than the detection limit. Since Bi is not solubilized in solids in Cu, but dispersed, a higher Bi content is more likely to cause a reduction in strength, such as tensile strength. Furthermore, such dispersed Bi leads to a tendency to easily cause cavities by shrinkage during sand casting. Furthermore, too high a Bi content gives rise to the appearance of various demerits, such as a reduction in mechanical properties caused by mixing Bi in an alloy to be recycled in the recycling of a member for hydraulic works produced using the alloy. above mentioned copper, so the member for hydraulic works must be collected separately.

Among the elements that constitute the inevitable impurities that the aforementioned copper alloy may contain is Si. Too high a Si content results in the facilitation of shrinkage cavities, whereby a suitable molding cannot be produced.

Among the elements that constitute the unavoidable impurities that the aforementioned copper alloy may contain is Al. Similar to Si, too high an Al content results in the facilitation of cavities by shrinkage, so it cannot be produce a suitable molded part.

Among the elements that constitute the unavoidable impurities that said copper alloy may contain, an Sb content is preferably less than the detection limit. Since Sb tends to form intermetallic compounds based on Cu-Sn-Sb, which tend to reduce the toughness of the alloy, there is a risk that the mechanical properties of the alloy will be reduced.

Among the elements that constitute the inevitable impurities that said copper alloy may contain, a Zr content is preferably less than the detection limit. The Zr content results in the degradation of mechanical properties and the facilitation of shrinkage cavities, so that a suitable molding cannot be produced.

Among the elements that constitute the unavoidable impurities that said copper alloy may contain, the content of each of the unavoidable impurities is preferably less than the detection limit. Examples of such impurities include Fe, Mn, Cr, Mg, Ti, Te, Se, Cd. Among them in particular, the content of Se and Cd, which are known to be toxic, is each preferably less than the detection limit. .

Note that the content values of the elements described in the present invention denote the content values of the elements in the resulting molded or forged part, not their content in the raw materials. The remainder of the aforementioned copper alloy is Cu. The copper alloy according to the present invention can be produced by a common method for producing a copper alloy. When a member for hydraulic works is produced using the copper alloy thus obtained, a common casting method (such as sand casting) can be used. For example, a member for hydraulic works can be prepared by a method in which an alloy is cast using an oil furnace, a gas furnace, or a high frequency induction melting furnace, and then cast using molds in various ways. .

Examples

Examples in which the copper alloy of the present invention was actually produced will be described below. First, the test methods for copper alloy will be described.

<Mechanical Properties Test>

A sample prepared by casting into a type A sample shape defined in JISH 5120 was processed into a type 4 specimen defined in JISZ 2241. Each of the specific shapes is indicated in Figures 1 and 2. Among them, a specimen Type A in Figure 1 is a hatched part in the figure, and the size unit is mm. Furthermore, a diameter dü is 14 ± 0.5 mm, an original specimen gauge length Lo is 50 mm, a length of a parallel part Lc is 60 mm or more, and the radius of a protruding part R is 15 mm or more. With respect to this specimen, the tensile strength and elongation were then measured according to JIS Z2241. The mechanical properties of each of the specimens were evaluated based on the values thus obtained.

• Tensile strength was evaluated as follows: 195 MPa or more was evaluated as "or"; and less than 195 MPa was evaluated as "x".

• Elongation was evaluated as follows: 15% or more was evaluated as "or"; and less than 15% was evaluated as "x".

Note that these threshold values are reference values for JIS H5120 CAC406 generally used in a member for hydraulic works.

<Erosion-corrosion test>

A sample prepared by casting into a metal mold having a size of 20mm in diameter x 120mm (length) was processed to have a cylindrical shape with a size of 16mm in diameter, as shown illustrated in Figure 3, to be a specimen 12, a nozzle 11 having a diameter of 1.6 mm is provided in a position separated from this specimen 12 by 0.4 mm, the solution 13 of 1% ^{CuCl 2} flowed from the nozzle 11 into the sample at a flow rate of 0.4 L / min in the normal flow direction for 5 hours, and the weight loss (amount of abrasion) and the maximum depth of the sample was measured before and after rehearsal.

• The amount of abrasion was evaluated as follows: less than 150 mg was evaluated as "or"; 150 mg or more and less than 200 mg was evaluated as "A"; and 200 mg or more was evaluated as "x".

• The maximum depth was evaluated as follows: less than 100 pm was evaluated as "or"; 100 pm or more and less than 150 pm was evaluated as "A"; and 150 pm or more was evaluated as "x".

<Machinability test and perforation test>

For each of the alloys, the drilling test was carried out with a drilling machine. The perforation test was carried out using each of the samples formed by machining to cylindrical samples of a size of 18 mm diameter x 20 mm (height), and using a drilling machine, the times required to drill a hole with a depth of 5 mm from a deep part of the cylinder was measured under the drilling conditions indicated in Table 1. Times with results of less than 6 seconds were evaluated as "or"; times with results of 6 seconds or more and less than 7 seconds were evaluated as "A"; and times with results of 7 seconds or more were evaluated as "x".

[Table 1]

<Fluency test>

Each of the copper alloys of the Examples and Comparative Examples was heated and melted, and then cast using a spiral-shaped test mold as illustrated in Figures 4 (a) and 4 (b), to obtain a spiral-shaped test tube. Since each of the alloys that vary in their Zn content has a different temperature at which solidification begins, it is impossible to evaluate the adequate fluidity of the molten metal for each of the alloys, using the same pouring temperature. Therefore, the temperature at which solidification begins for each of the alloys was measured by the thermal analysis method, and then the casting was carried out at a temperature of 110 ° C above the measured temperature. Then, the flow length of the spiral-shaped part of the spiral-shaped specimen thus cast was measured. Flow lengths with results of 300 mm or more were evaluated as "or"; flow lengths with results of 280 mm or more and less than 300 mm were evaluated as "A"; and flow lengths with results less than 280 mm were evaluated as "x".

<Test to determine casting defects>

<Liquid penetrant test using a stepped sample>

For each of the alloys, a liquid penetrant test was performed using a staggered sample and an evaluation of the defects of the molded part was performed. "-" in the Table indicates that the evaluation was not carried out. Specifically, the test was carried out as follows. ^{A staggered CO 2} mold was prepared as illustrated in Figure 5 (casting temperature at 1120 ° C), which was provided with three staggered parts with different wall thicknesses of 10, 20 and 30 mm, so that the effect The feed rate was reduced and the resulting molded part was more likely to develop casting defects, and the molded part thus obtained was cut in two in half, and the liquid penetration test was carried out according to JIS Z2343 to be tested. the occurrence of casting defects and small voids in this liquid penetrant test. Those in which no evidence of defects such as shrinkage cavity defects and gas defects was observed in a part having a thickness of 10 and 20 mm were evaluated as "or"; those in which some signs of defects were not observed in the part having a thickness of 10 mm but if they were observed in the part having a thickness of 20 mm were evaluated as "A"; and those in which some indications of defects were observed in the parts having a thickness of 10 and 20 mm were evaluated as "x". A part that had a thickness of 30 mm.

<Production method>

The materials containing each of the elements were mixed and melted in a high frequency induction melting furnace, followed by casting using a CO ² mold to produce samples each with the composition indicated in Table 2. Note that all Element content values are expressed as% by mass and are values measured after production. In addition, a conventionally used lead-containing bronze material, JIS H5120 CAC406, was used as Comparative Example 12, which was used for comparison of physical properties. Its content is also indicated in the Table. The following tests were carried out for each of the resulting copper alloys. Note that "-" in the Table indicates that it is less than the detection limit. Note that, the content of each of B, Bi, Sb, Al, Si, and Fe was less than the detection limit, in each of the Examples and Comparative Examples except Comparative Example 11. The overall evaluation was carried out performed according to the following standards: those with evaluation "or" in all the tests performed were defined as "or"; those who had at least an "A" assessment in any of the trials were defined as "A"; and those with at least one "x" rating in any of the trials were defined as "x".

[Table 2]

*: Comparative Example [Table 3]

*: Comparative Example

First, CAC406 of Comparative Example 12. CAC406 has mechanical properties, such as a tensile strength of 195 MPa or more, and an elongation of 15% or more, which are JIS defined values. On the other hand, since CAC406 contains 5.38 mass% Pb, good results were obtained in the drilling test. Furthermore, the flow length measured in the molten metal flow test was 298 mm, which was evaluated as "A". On the other hand, since it contains 4 to 6% by mass of Pb, Comparative Example 12 has a problem in leaching lead.

First, Comparative Example 1 and Examples 1 to 4 were prepared to have a variable Zn content, with the content of elements other than Zn as close to each other as possible. These were arranged in the first group in Table 2 and Table 3 in ascending order of Zn content. With respect to mechanical properties, each showed values above the tensile strength of 195 MPa and elongation of 15%, while in Comparative Example 1 in which Zn is less than 12% by mass, the time required for machining it was too long. On the other hand, in Example 4 where the Zn is almost 21% by mass, which is the upper limit, it was found that the machinability tended to be reduced.

Next, with Example 2 as a reference, Comparative Example 2, Examples 5, 6 and 7 and Comparative Example 3 were prepared to have a variable Sn content, with the content of elements other than Sn as close as possible each. These were organized into the second group in Table 2 and Table 3 in ascending order of Sn content. In Example 5, in which the Sn content is 1.43% by mass, which is close to the lower limit value, the erosion-corrosion resistance had a tendency to decrease slightly, and in Comparative Example 2 it was Since the Sn content is 0.99% by mass, the erosion-corrosion resistance was notably absent. On the other hand, in Example 7 where Zn is 4.5% by mass, the machinability had a tendency to decrease, and in Comparative Example 3 where the Sn content is 4.92% by mass that exceeds 3.0% by mass, elongation and machinability problem occurred.

Next, Examples 5, 3, and 4 were arranged in ascending order of the total Zn Sn content in Table 2, and Comparative Example 4 was prepared in which the Zn Sn content further exceeds compared to those and exceeds 23.5% by mass, and were ranked in the third group in Table 2 and Table 3 in ascending order of the total Zn Sn content. In Comparative Example 4, both tensile strength and elongation were considerably reduced.

Next, with Example 2 as a reference, Comparative Example 5, Examples 8 and 9 and Comparative Example 6 were prepared to have a variable P content, with the content of elements other than P as close to each other as possible. . These were arranged into the fourth group in Table 2 and Table 3 in ascending order of P content. In each of Comparative Example 5, in which the P content is less than 0.005% by mass, and in Example Comparative 6, in which the P content exceeds 0.15% by mass, consequently, a flow problem occurred. Furthermore, the results of the liquid penetrant test are indicated in Figure 6. In Comparative Example 6 where the P content exceeds 0.15% by mass, shrinkage cavities were completely produced. Note that in the photograph, the parts having a thickness of 30 mm were not estimated and the parts where red and fine spots are generated in a thinner part were examined. In examples other than Comparative Example 6, in the parts having a thickness of 20 mm or less, no stains were found, which gave good results.

Next, with Example 2 as a reference, Comparative Example 7, Examples 10 and 11 and Comparative Example 8 were prepared to have a variable Pb content, with the content of elements other than Pb as close to each other as possible. . These were organized into the fifth group in Table 2 and Table 3 in ascending order of Pb content. In Comparative Example 7 where the Pb content is 0.03% by mass, which is less than 0.05% by mass, consequently, a machinability problem occurred.

Furthermore, with compositions similar to Example 2, Examples 13, 14 and 15 and Comparative Examples 9 and 10 were prepared to contain Ni. None of them had problems with mechanical properties. However, in Comparative Examples 9 and 10 where the Ni content exceeds 0.5 mass%, a problem in machinability occurred.

Still further, with a composition similar to Example 2, Comparative Example 11 was prepared to contain 0.3 mass% Bi. The tensile strength was greatly reduced, so there was a problem in the mechanical properties. On the other hand, this content presented a problem in view of recyclability.

with the content of elements other than Pb as close as possible to each other. These were organized into the fifth group in Table 2 and Table 3 in ascending order of Pb content. In Comparative Example 7 where the Pb content is 0.03% by mass, which is less than 0.05% by mass, consequently, a machinability problem occurred.

Furthermore, with compositions similar to Example 2, Examples 13, 14 and 15 and Comparative Examples 9 and 10 were prepared to contain Ni. None of them had problems with mechanical properties. However, in Comparative Examples 9 and 10 where the Ni content exceeds 0.5 mass%, a problem in machinability occurred.

Still further, with a composition similar to Example 2, Comparative Example 11 was prepared to contain 0.3 mass% Bi. The tensile strength was greatly reduced, so there was a problem in the mechanical properties. On the other hand, this content presented a problem in view of recyclability.

Claims (1)

1. A copper alloy for use in a member for hydraulic works, the copper alloy consisting of: 0.5% by mass or less Ni; 12% by mass or more and 21% by mass or less of Zn; 1.4% by mass or more and 3.0% by mass or less of Sn, with a total content of Zn and Sn being 23.5% by mass or less; 0.005% by mass or more and 0.15% by mass or less of P; 0.05% by mass or more and 0.30% by mass or less of Pb; and the rest, where the rest is Cu and unavoidable impurities, where Bi, Si, Al, Sb, Zr, Fe, Mn, Cr, Mg, Ti, Te, Se and Cd are among the elements that constitute the unavoidable impurities.