EP3031937A1

EP3031937A1 - Copper alloy, copper alloy thin sheet and copper alloy manufacturing method

Info

Publication number: EP3031937A1
Application number: EP14834900.4A
Authority: EP
Inventors: Kazunari Maki; Kenichiro SUEHIRO; Shuhei ARISAWA
Original assignee: Mitsubishi Shindoh Co Ltd; Mitsubishi Materials Corp
Current assignee: Mitsubishi Shindoh Co Ltd; Mitsubishi Materials Corp
Priority date: 2013-08-09
Filing date: 2014-08-08
Publication date: 2016-06-15
Also published as: CN105452500B; KR20160041914A; JP2015057511A; TW201522670A; TWI522483B; WO2015020187A1; JP5866410B2; EP3031937A4; CN105452500A; KR102213955B1

Abstract

Provided is a copper alloy containing 1.5 to 2.7% by mass of Fe, 0.008 to 0.15% by mass of P, and 0.01 to 0.5% by mass of Zn, the balance being Cu and inevitable impurities. The amount of C contained as one of the inevitable impurities is less than 3 ppm by mass.

Description

TECHNICAL FIELD

The present invention relates to a copper alloy, a copper alloy thin sheet, and a method of manufacturing a copper alloy that are suitable as a copper alloy sheet strip that is used, for example, in household electrical appliances, semiconductor components such as a lead frame for a semiconductor device, electrical and electronic component materials such as a printed wiring board, switch components, bus bars, mechanism components such as a connector, industrial apparatuses, and the like.
Priority is claimed on Japanese Patent Application No. 2013-167045, filed August 9, 2013 , and Japanese Patent Application No. 2014-116287, filed June 4,2014 , the contents of which are incorporated herein by reference.

BACKGROUND ART

As a copper alloy for the above-described various usages, a Cu-Fe-P-based copper alloy that contains Fe and P is typically used in the related art. As the Cu-Fe-P-based copper alloy, a copper alloy (CDA19400 alloy), which contains 2.1 to 2.7% by mass of Fe, 0.015 to 0.15% by mass of P, and 0.05 to 0.20% by mass of Zn, is exemplified. The CDA19400 alloy is an international standard alloy that is defined in Copper Development Association (CDA).
Here, the above-described CDA19400 alloy is a precipitation strengthening type alloy in which Fe or an intermetallic compound such as Fe-P is allowed to precipitate in a copper parent phase, and is excellent in strength, conductivity, and thermal conductivity. Accordingly, the CDA19400 alloy is widely used for various usages.
Recently, in accordance with usage enlargement of the Cu-Fe-P-based copper alloy, a reduction in weight, thickness, and size of electrical or electronic apparatuses, and the like, the CDA19400 alloy is demanded to have further higher strength or conductivity, and excellent bending workability.
In addition, the above-described lead frame, connector, and the like are manufactured by etching or punching the copper alloy thin sheet. Here, when punching the copper alloy thin sheet that is composed of the CDA19400 alloy and the like, there is a problem that abrasion in a mold is significant, and it is necessary to replace the mold after use for a short time.
Accordingly, for example, PTL 1 and PTL 2 suggest that C is added to the Cu-Fe-P-based alloy so as to suppress cracking in a hot-rolling process, and to improve characteristics such as punching mold abrasion resistance. In addition, there is also suggested that Mg and the like are added so as to improve characteristics such as strength of the Cu-Fe-P-based alloy.

CITATION LIST

PATENT LITERATURE

[PTL 1] Japanese Unexamined Patent Application, First Publication No. H11-323464
[PTL 2] Japanese Unexamined Patent Application, First Publication No. H11-350055

DISCLOSURE OF INVENTION

TECHNICAL PROBLEM

However, in the copper alloy that is composed of the Cu-Fe-P-based alloy, when rolling an ingot to manufacture a copper alloy thin sheet, a lot of surface defects may occur. When the surface defects are present, a manufacturing yield ratio greatly decreases. Therefore, there is a problem that the manufacturing cost of the copper alloy thin sheet greatly increases.
In addition, when the copper alloy thin sheet composed of the above-described Cu-Fe-P-based alloy is subjected to pressing, etching, or silver plating, a non-smooth shape defect caused by coarse iron alloy particles may occur.
The invention has been made in consideration of the above-described circumstances, and an object thereof is to provide a copper alloy, a copper alloy thin sheet, and a method of manufacturing a copper alloy capable of suppressing occurrence of a surface defect and a shape defect in a Cu-Fe-P-based alloy.

SOLUTION TO PROBLEM

The present inventors have conducted extensive research to solve the problem. As a result, it was proven that surface defects and shape defects, which occur in the Cu-Fe-P-based alloy such as the CDA19400 alloy, are formed when iron alloy particles containing Fe and C are exposed to a surface of the copper alloy thin sheet.
In addition, it was proven that in a case where C is present in a copper alloy molten metal in an amount that is equal to or greater than a constant amount, a liquid phase that contains Fe as a main component and C, and a liquid phase that contains Cu as a main component are separated from each other, and a coarse Fe-C crystallized product is generated in the ingot. In addition, the present inventors found that the iron alloy particles, which are exposed to the surface of the copper alloy thin sheet, are generated due to the coarse Fe-C crystallized product generated in the ingot.
The invention has been made on the basis of the above-described finding. According to a first aspect of the invention, there is provided a copper alloy containing 1.5 to 2.7% by mass of Fe, 0.008 to 0.15% by mass of P, and 0.01 to 0.5% by mass of Zn, the balance being Cu and inevitable impurities. The amount of C contained as one of the inevitable impurities is less than 3 ppm by mass.
In the copper alloy configured as described above, the amount of C contained as one of the inevitable impurities is regulated to be less than 3 ppm by mass. As described above, C is an element that has a function of promoting liquid phase separation between a liquid phase that contains Fe as a main component and C, and a liquid phase that contains Cu as a main component. Therefore, when the amount of C contained increases, a coarse Fe-C crystallized product is likely to be generated in an ingot. Accordingly, when regulating the amount of C contained as described above, it is possible to suppress occurrence of the coarse Fe-C crystallized product, and it is possible to greatly reduce surface defects due to iron alloy particles. In addition, it is possible to suppress a shape defect of a product which is caused by the coarse Fe-C crystallized product.
Here, the copper alloy of the invention may further contain one or both of 0.003 to 0.5% by mass of Ni and 0.003 to 0.5% by mass of Sn.
In this case, Ni or Sn is solid-soluted in a parent phase of Cu. Accordingly, it is possible to realize an improvement in the strength of the Cu-Fe-P-based copper alloy.
In addition, the copper alloy of the invention may further contain at least one of Mg, Ca, Sr, Ba, rare-earth elements, Zr, Si, Al, Be, Ti, and Co in a range of 0.0007 to 0.5% by mass.
In this case, it is possible to attain an improvement in the strength of the Cu-Fe-P-based alloy and an improvement in punching mold abrasion resistance due to an element such as Mg, Ca, Sr, Ba, rare-earth elements, Zr, Si, Al, Be, Ti, and Co.
In addition, in the copper alloy of the invention, the amount of Mn contained as one of the inevitable impurities may be 20 ppm by mass or less, and the amount of Ta contained as one of the inevitable impurities may be 1 ppm by mass or less.
When the liquid phase separation occurs in the copper alloy molten metal as described above, an element such as Mn and Ta is contained in the liquid phase that contains Fe as a main component and C, and tends to promote the liquid phase separation. Therefore, there is a concern that when Mn and Ta, which are inevitable impurities, are contained in a large amount, the coarse Fe-C crystallized product is likely to be generated in an ingot. Therefore, when the amount of Mn contained is regulated to 20 ppm by mass or less, and the amount of Ta contained is regulated to 1 ppm by mass or less, it is possible to reliably suppress occurrence of the coarse Fe-C crystallized product.
According to a second aspect of the invention, there is provided a copper alloy thin sheet that is composed of the above-described copper alloy. The number of surface defects, which have a length of 200 µm or greater and are formed when iron alloy particles containing Fe and C are exposed to a surface, are 5 pieces/m² or less. More preferably, the number of the surface defects having a length of 200 µm or greater is 2 pieces/m² or less, and still more preferably less than 1 piece/m².
In addition, in the copper alloy thin sheet of the invention, the thickness of the thin sheet may be 0.5 mm or less.
According to the copper alloy thin sheet configured as described above, the copper alloy thin sheet is composed of a copper alloy in which the amount of C contained as one of the inevitable impurities is suppressed to be low. Accordingly, occurrence of iron alloy particles containing Fe and C is suppressed, and it is possible to suppress occurrence of the surface defects which are caused by the iron alloy particles. In addition, it is possible to suppress the shape defect of a product which is caused by the coarse Fe-C crystallized product. In addition, when the number of the surface defects having a length of 200 µm or greater is 5 pieces/m² or less, it is possible to significantly decrease a product failure rate when performing pressing, etching, or silver plating. Particularly, when the sheet thickness of the copper alloy thin sheet is 0.5 mm or less and surface defects of 200 µm or greater exist, there is a concern that defects also exist in a thickness direction. Therefore, for example, when machining a precise shape such as pressing and etching, the surface defects may cause a failure. From the above-described viewpoint, when the sheet thickness of the copper alloy thin sheet is 0.2 mm or less, the effect of the invention is further exhibited. When considering the manufacturing cost of the copper alloy thin sheet and the effect that is obtained, it is preferable that the lower limit of the sheet thickness of the thin sheet be set to 0.05 mm, but there is no limitation thereto.
According to a third aspect of the invention, a method is provided for manufacturing a copper alloy. The method includes a melting process of melting a raw material to produce a copper alloy molten metal, a high-temperature holding process of holding the copper alloy molten metal at 1300°C or higher, and a casting process of supplying the copper alloy molten metal, which is held at 1300°C or higher, into a mold so as to obtain an ingot.
As described above, the method of manufacturing a copper alloy includes the high-temperature holding process of holding the copper alloy molten metal at 1300°C or higher, and the casting process of supplying the copper alloy molten metal, which is held at a temperature as high as 1300°C or higher, into a mold so as to obtain an ingot. Accordingly, in the copper alloy molten metal, it is possible to suppress the liquid phase separation between the liquid phase that contains Fe as a main component and C, and the liquid phase that contains Cu as a main component, and it is possible to suppress generation of the coarse Fe-C crystallized product. Accordingly, it is possible to reduce the surface defects which are caused by the iron alloy particles. In addition, it is possible to suppress the shape defect of the product which is caused by the coarse Fe-C crystallized product.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the invention, it is possible to provide a copper alloy, a copper alloy thin sheet, and a method of manufacturing a copper alloy capable of suppressing occurrence of a surface defect and a shape defect in a Cu-Fe-P-based alloy.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a photograph obtained by observing a surface defect of a copper alloy thin sheet with an optical microscope.
FIG. 2 is a flowchart illustrating a method of manufacturing a copper alloy according to an embodiment of the invention.

BEST MODE FOR CARRYING-OUT THE INVENTION

Hereinafter, description will be given of a copper alloy according to a first embodiment of the invention.
The copper alloy according to the first embodiment of the invention contains 1.5 to 2.7% by mass of Fe, 0.008 to 0.15% by mass of P, and 0.01 to 0.5% by mass of Zn, the balance being Cu and inevitable impurities. The amount of C contained as one of the inevitable impurities is less than 3 ppm by mass.
Hereinafter, description will be given of the reason why the amounts of the elements contained are set in the above-described ranges.

[Fe]

Fe is solid-soluted in a parent phase of Cu, and generates P-containing precipitates (Fe-P compounds). When the Fe-P compounds are dispersed in the parent phase of Cu, strength and hardness are improved without decreasing conductivity.
Here, when the amount of Fe contained is less than 1.5% by mass, the effect of improving the strength, and the like are not sufficient. On the other hand, when the amount of Fe contained exceeds 2.7% by mass, a large crystallized product is generated. Therefore, there is a concern that surface cleanliness may be deteriorated. In addition, there is a concern that a decrease in conductivity and workability may be caused.
Accordingly, in this embodiment, the amount of Fe contained is 1.5 to 2.7% by mass. It is preferable that the amount of Fe contained be set in a range of 1.8 to 2.6% by mass so as to reliably exhibit the above-described operation effect.

[P]

P is an element having a deoxidizing operation. In addition, as described above, P generates Fe-P compounds in combination with Fe. When the Fe-P compounds are dispersed in the parent phase of Cu, the strength and the hardness are improved without decreasing the conductivity.
Here, when the amount of P contained is less than 0.008% by mass, the effect of improving the strength, and the like are not sufficient. On the other hand, when the amount of P contained exceeds 0.15% by mass, a decrease in the conductivity and the workability is caused.
Accordingly, in this embodiment, the amount of P contained is 0.008 to 0.15% by mass. It is preferable that the amount of P contained be set in a range of 0.01 to 0.05% by mass so as to reliably exhibit the above-described operation effect.

[Zn]

Zn is an element that is solid-soluted in the parent phase of Cu and has an operation of improving solder thermal-peeling resistance.
Here, when the amount of Zn contained is less than 0.01% by mass, the operation effect of improving the solder thermal-peeling resistance cannot be sufficiently exhibited. On the other, even when the amount of Zn contained exceeds 0.5% by mass, the above-described effect is saturated.
Accordingly, in this embodiment, the amount of Zn contained is 0.01 to 0.5% by mass. It is preferable that the amount of Zn contained be set in a range of 0.05 to 0.35% by mass so as to reliably exhibit the above-described operation effect.

[C]

C is contained in the above-described copper alloy as an inevitable impurity. Here, in a case where a large amount of C is contained, a surface defect of a copper alloy thin sheet greatly increases. A result obtained by observing an example of the surface defect with an optical microscope is illustrated in FIG. 1.
From an analysis result with an electron probe micro analyzer (EPMA), the surface defect that is observed in this embodiment is caused by iron alloy particles containing Fe and C.
Typically, when melting and casting the above-described copper alloy, the Fe element is present in a state of being melted in a liquid phase that contains Cu as a main component. However, when C is present in an amount that is equal to or greater than a constant amount, in a copper alloy molten metal, the liquid phase that contains Cu as a main component, and a liquid phase that contains Fe as a main component and C are separated from each other. As a result, a coarse Fe-C crystallized product is present in an ingot. Then, when the ingot is rolled, it is considered that iron alloy particles, which are caused by the coarse Fe-C crystallized product, are exposed to a surface of the copper alloy thin sheet, and the above-described surface defect occurs. In addition, when performing pressing, etching, or silver plating, a shape defect occurs due to the iron alloy particles.
Accordingly, when the element C is reduced, it is possible to suppress the surface defect and the shape defect which are caused by the iron alloy particles. Accordingly, in this embodiment, the amount of C contained is limited to be less than 3 ppm by mass. It is preferable that the amount of C contained be set to be less than 2 ppm by mass so as to reliably accomplish suppression of the surface defect and the shape defect.
Examples of the inevitable impurities other than C include Ni, Sn, Mg, Ca, Sr, Ba, rare-earth elements, Zr, Si, Al, Be, Ti, H, Li, B, N, O, F, Na, S, Cl, K, V, Cr, Mn, Co, Ga, Ge, As, Se, Br, Rb, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sb, Te, I, Cs, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, and the like. It is preferable that these inevitable impurities be contained in a total amount of 0.3% by mass or less. When considering the manufacturing cost of the copper alloy and an effect that is obtained, the lower limit of the total amount of the inevitable impurities is preferably 0.1% by mass, but there is no limitation thereto.
Next, description will be given of an example of the method of manufacturing the copper alloy according to this embodiment with reference to a flowchart illustrated in FIG. 2.

[Melting Process S01]

A copper alloy molten metal is generated by melting a copper raw material, pure iron, Zn or a Cu-Zn parent alloy, and P or a Cu-P parent alloy. In addition, as the copper raw material, so-called 4N Cu having purity of 99.99% by mass or greater is preferable. As the pure iron, so-called 3N Fe having purity of 99.9% by mass or greater or so-called 4N Fe having purity of 99.99% by mass or greater is preferable. As an atmosphere, Ar is preferable. A melting temperature is set to, for example, 1100 to 1300°C.

[High-temperature holding process S02]

Next, a temperature of the copper alloy molten metal that is obtained is raised to 1300°C or higher and is held at the temperature. When the copper alloy molten metal is held at the high temperature, it is possible to suppress the liquid phase separation in the copper alloy molten metal. In the high-temperature holding process S02, it is preferable that the temperature be set in a range of 1300 to 1500°C, and holding time is set in a range of 1 minute to 24 hours.

[Casting Process S03]

In addition, the copper alloy molten metal that is held at a temperature of 1300°C or higher is poured into a mold in a state of being held at the high temperature, thereby producing an ingot. According to this, the ingot of the copper alloy according to this embodiment is produced.
Here, it is preferable that a cooling rate during casting be as fast as possible.
For example, it is preferable that the cooling rate from 1300 to 900°C be 5 °C/s or greater, more preferably 10 °C/s or greater. When considering the manufacturing cost of the copper alloy and the effect that is obtained, it is preferable that the upper limit of the cooling rate be 200 °C/s, but there is no limitation thereto.
After subjecting the ingot that is obtained to hot-rolling, cold-rolling and a heat treatment are appropriately repeated to produce a copper alloy thin sheet having a predetermined thickness. Hot-rolling is performed in a reducing atmosphere under a condition of 750 to 1000°C. Cold-rolling reduction is set to 40 to 95%, heat treatment is performed at 400 to 700°C, and final annealing is performed at 200 to 350°C after final rolling.
In the copper alloy thin sheet, the number of surface defects, which have a length of 200 µm or greater and are formed when the iron alloy particles containing Fe and C are exposed to a surface, is 5 pieces/m² or less. Preferably, the number of surface defects having a length of 200 µm or greater is 2 pieces/m² or less, and more preferably 1 piece/m² or less.
According to this embodiment configured as described above, since the amount of C, which is one of the inevitable impurities, is less than 3 ppm by mass, it is possible to suppress generation of the coarse Fe-C crystallized product in the ingot. Accordingly, it is possible to suppress formation of the iron alloy particles which are caused by the coarse Fe-C crystallized product, and it is possible to greatly reduce occurrence of the surface defect. In addition, it is possible to suppress a shape defect of a product.
In addition, since the manufacturing method according to this embodiment includes the high-temperature holding process S02 of holding the copper alloy molten metal at a high temperature of 1300°C or higher, and the casting process S03 of supplying the copper alloy molten metal, which is held at 1300°C or higher, into a mold to manufacture the ingot, it is possible to suppress generation of the coarse Fe-C crystallized product.
Hereinafter, description will be given of a copper alloy according to a second embodiment of the invention.
The copper alloy according to the second embodiment of the invention contains 1.5 to 2.7% by mass of Fe, 0.008 to 0.15% by mass of P, 0.01 to 0.5% by mass of Zn, any one or both of 0.003 to 0.5% by mass of Ni and 0.003 to 0.5% by mass of Sn, and at least one or more of Mg, Ca, Sr, Ba, rare-earth elements, Zr, Si, Al, Be, Ti, and Co in a range of 0.0007 to 0.5% by mass, the balance being Cu and inevitable impurities. The amount of C contained as one of the inevitable impurities is less than 3 ppm by mass.
Hereinafter, description will be given of the reason why the amounts of the elements contained are set in the above-described ranges. In addition, description of the same elements as in the first embodiment will not be repeated.

[Ni]

Ni is solid-soluted in the parent phase of Cu, and has an operation of improving the strength and lead bending fatigue resistant characteristics (repetitive bending fatigue resistant characteristics).
Here, when the amount of Ni contained is less than 0.003% by mass, it is difficult to sufficiently exhibit the above-described effects. On the other hand, when the amount of Ni contained exceeds 0.5% by mass, the conductivity significantly decreases.
Accordingly, in this embodiment, the amount of Ni contained is 0.003 to 0.5% by mass. It is preferable that the amount of Ni contained be set in a range of 0.008 to 0.2% by mass so as to reliably exhibit the above-described operation effect.

[Sn]

Sn is solid-soluted in the parent phase of Cu, and has an operation of improving the strength and solderability.
Here, when the amount of Sn contained is less than 0.003% by mass, it is difficult to sufficiently exhibit the above-described effect. On the other hand, when the amount of Sn contained exceeds 0.5% by mass, the conductivity significantly decreases.
Accordingly, in this embodiment, the amount of Sn contained is 0.003 to 0.5% by mass. It is preferable that the amount of Sn contained be set in a range of 0.008 to 0.2% by mass so as to reliably exhibit the above-described operation effect.

[Mg, Ca, Sr, Ba, Rare-Earth Elements, Zr, Si, Al, Be, Ti, and Co]

Mg, Ca, Sr, Ba, rare-earth elements, Zr, Si, Al, Be, Ti, and Co are solid-soluted in the parent phase of Copper, or are present as a precipitate or a crystallized product, and have an operation of improving the strength of the Cu-Fe-P-based alloy and an operation of improving punching mold abrasion resistance.
Here, when the amount of Mg, Ca, Sr, Ba, rare-earth elements, Zr, Si, Al, Be, Ti, and Co, which are contained, is less than 0.0007% by mass, it is difficult to exhibit the above-described effect. On the other hand, when the amount of Mg, Ca, Sr, Ba, the rare-earth elements, Zr, Si, Al, Be, Ti, and Co, which are contained, exceeds 0.5% by mass, the conductivity greatly decreases, and a large oxide, precipitate, or crystallized product is likely to be generated, and there is a concern that the surface cleanliness may be deteriorated.
Accordingly, in the copper alloy of this embodiment, the amount of Mg, Ca, Sr, Ba, the rare-earth elements, Zr, Si, Al, Be, Ti, and Co, which are contained, is 0.0007 to 0.5% by mass. In addition, it is preferable that the amount of Mg, Ca, Sr, Ba, the rare-earth elements, Zr, Si, Al, Be, Ti, and Co, which are contained, be set in a range of 0.005 to 0.15% by mass so as to reliably exhibit the above-described operation effect.
Here, the rare-earth elements represent Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
Examples of the inevitable impurities other than C include H, Li, B, N, O, F, Na, S, Cl, K, V, Cr, Mn, Ga, Ge, As, Se, Br, Rb, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sb, Te, I, Cs, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, and the like. It is preferable that the total amount of the inevitable impurities be 0.3% by mass or less. When considering the manufacturing cost of the copper alloy and the effect that is obtained, it is preferable that the lower limit of the total amount of the inevitable impurities be set to 0.1% by mass, but there is no limitation thereto.
As is the case with the first embodiment, the copper alloy according to the second embodiment is manufactured by the melting process S01, the high-temperature holding process S02 of the molten metal, and the casting process S03. In the melting process S01, for addition ofNi, Sn, Mg, Ca, Sr, Ba, the rare-earth elements, Zr, Si, Al, Be, Ti, and Co, metal element elementary substances or parent alloys containing the elements are used.
According to this embodiment configured as described above, since Ni and Sn are contained, it is possible to realize an improvement of the strength through solid-solution strengthening.
In addition, since at least one of Mg, Ca, Sr, Ba, the rare-earth elements, Zr, Si, Al, Be, Ti, and Co are contained in a range of 0.0007 to 0.5% by mass, it is possible to realize additional high strengthening of the Cu-Fe-P-based alloy, and it is possible to realize an improvement of the punching mold abrasion resistance.
In addition, since the amount of C contained is less than 3 ppm by mass, it is possible to suppress formation of the iron alloy particles containing Fe and C, and it is possible to greatly reduce occurrence of the surface defect. In addition, it is possible to suppress the shape defect in a product.
Hereinafter, description will be given of a copper alloy according to a third embodiment of the invention.
The copper alloy according to the third embodiment of the invention contains 1.5 to 2.7% by mass of Fe, 0.008 to 0.15% by mass of P, and 0.01 to 0.5% by mass of Zn, the balance being Cu and inevitable impurities. The amount of C contained as one of the inevitable impurities is less than 3 ppm by mass, the amount of Mn contained as one of the inevitable impurities is 20 ppm by mass or less, and the amount of Ta contained as one of the inevitable impurities is 1 ppm by mass or less.
Hereinafter, description will be given of the reason why the amounts of the elements contained are set in the above-described ranges. In addition, description of the same elements as in the first embodiment will not be repeated.

[Mn and Ta]

Mn and Ta are inevitable impurities, and are contained in the above-described copper alloy.
Typically, when melting and casting the above-described copper alloy, the Fe element is present in a state of being melted in a liquid phase that contains Cu as a main component. However, in a case where C is present in an amount that is equal to or greater than a constant amount, in the copper alloy molten metal, the liquid phase that contains Cu as a main component, and a liquid phase that contains Fe as a main component and C are separated from each other. Here, when the liquid phase separation occurs in the copper alloy molten metal as described above, Mn and Ta are elements which are contained in the liquid phase that contains Fe as a main component and C, and may promote the liquid phase separation.
Accordingly, when the element C is reduced, and the amount of Mn and Ta, which are contained, is reduced, it is possible to suppress the liquid phase separation in the copper alloy molten metal. As a result, it is possible to suppress generation of the coarse Fe-C crystallized product, and it is possible to suppress the surface defect and the shape defect which are caused by the iron alloy particles. Accordingly, in the copper alloy according to this embodiment, the amount of C contained is limited to be less than 3 ppm by mass, the amount of Mn contained is limited to 20 ppm by mass or less, and the amount of Ta contained is limited to 1 ppm by mass or less. It is preferable that the amount of C contained be set to be less than 2 ppm by mass, the amount of Mn contained is less than 15 ppm by mass, and the amount of Ta contained is less than 0.7 ppm by mass so as to reliably accomplish suppression of the surface defect and the shape defect.
Examples of the inevitable impurities other than C, Mn, and Ta include Ni, Sn, Mg, Ca, Sr, Ba, rare-earth elements, Zr, Si, Al, Be, Ti, H, Li, B, N, O, F, Na, S, Cl, K, V, Cr, Co, Ga, Ge, As, Se, Br, Rb, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sb, Te, I, Cs, Hf, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, and the like. It is preferable that the total amount of the inevitable impurities be 0.3% by mass or less. When considering the manufacturing cost of the copper alloy and the effect that is obtained, the lower limit of the total amount of the inevitable impurities is preferably 0.1% by mass, but there is no limitation thereto.
As is the case with the first embodiment and the second embodiment, the copper alloy according to the third embodiment is manufactured by the melting process S01, the high-temperature holding process S02 of the molten metal, and the casting process S03.
In the melting process S01, it is preferable to use a raw material in which the amount of Mn and Ta contained is small. Particularly, there is a high possibility that the element Mn is mixed-in from an iron-based raw material and the like. Accordingly, it is preferable that the iron-based raw material be carefully selected and used. Preferably, an Fe raw material, which contains 0.1% by mass or less of Mn and 0.005% by mass or less of Ta, is used.
According to this embodiment configured as described above, since the amount of C contained as one of the inevitable impurities is less than 3 ppm by mass, the amount of Mn contained as one of the inevitable impurities is 20 ppm or less, and the amount of Ta contained as one of the inevitable impurities is 1 ppm by mass or less, it is possible to suppress the liquid phase separation in the copper alloy molten metal and the formation of the iron alloy particles containing Fe and C. As a result, it is possible to greatly reduce occurrence of the surface defect. In addition, it is possible to suppress the shape defect of a product.
Hereinbefore, description has given of the copper alloy, the copper alloy thin sheet, and the method of manufacturing a copper alloy according to the embodiments of the invention. However, the invention is not limited thereto and can be appropriately modified in a range not departing from the technical spirit of the invention.
For example, description has been given of a configuration in which the copper raw material is melted to produce the copper molten metal, and various elements are added to the copper molten metal. However, there is no limitation thereto, and component preparation may be performed by melting a scrap raw material and the like.
In addition, in this embodiment, description has been given of a configuration in which the high-temperature holding process S02 is provided. However, there is no limitation thereto, and the amount of C contained may be reduced by another means. For example, the element C may be prevented from being mixed-in through careful selection of a raw material that is used. There is a high possibility that the element C may be mixed-in from an iron-based raw material and the like. Accordingly, it is preferable that the iron-based raw material be carefully selected and used.
In addition, in the third embodiment, any one or both of 0.003 to 0.5% by mass of Ni and 0.003 to 0.5% by mass of Sn may be contained, and at least of Mg, Ca, Sr, Ba, rare-earth elements, Zr, Si, Al, Be, Ti, and Co may be contained in a range of 0.0007 to 0.5% by mass.

EXAMPLES

Hereinafter, description will be given of results of a confirmation experiment that was performed to confirm the effect of the invention.

(Example 1)

A copper raw material composed of oxygen-free copper (ASTM B152 C10100), which had purity of 99.99% by mass or greater and in which the amount of C contained was 1 ppm by mass or less, was prepared. The copper raw material was placed in an alumina crucible, and was melted by using a high-frequency melting furnace that was set to an Ar gas atmosphere.
As raw materials, pure iron, a Cu-Zn parent alloy, a Cu-Ni parent alloy, a Cu-Sn parent alloy, a Cu-P parent alloy, and raw materials or parent alloys of Mg, Ca, Sr, Ba, rare-earth elements, Zr, Si, Al, Be, Ti, and Co were added to the resultant copper molten metal, which was obtained, according to the necessity, and then melting was performed at 1200°C in an Ar atmosphere for preparation in a component composition illustrated in Table 1. Then, the resultant molten metal that was prepared was poured into a water-cooled copper mold to produce an ingot. In addition, the amount of C contained in each raw material was 10 ppm by mass or less. The size of the ingot that was produced was set to have a thickness of approximately 30 mm, a width of approximately 150 mm, and a length of approximately 200 mm. In addition, in Examples 1 to 27, as the iron raw material, high-purity iron (purity of 99.99% by mass) was used.
In addition, in Examples 23 to 26, a temperature of the molten metal, which was obtained, was raised once from 1200 to 1300°C, and then the ingot was produced.
A cooling rate from 1300 to 900°C when the temperature of the molten metal was set to 1300°C, and a cooling rate from 1200 to 900°C when the temperature of the molten metal was set to 1200°C were set to approximately 10 °C/s or greater.
In addition, in Comparative Examples 1 and 2, a C powder was added to the molten metal to come into contact therewith, thereby increasing the amount of C.
The ingot, which was obtained, was heated at 950°C, and hot-rolling was performed up to a thickness of 5.0 mm. After the hot-rolling, surface grinding was performed to remove an oxidized film, and the thickness was set to 4.0 mm.
Then, rough rolling was performed to set the thickness to 0.4 mm. Next, a heating process was performed at 550°C for 1 hour, and then cold-rolling was additionally performed to set the thickness to 0.2 mm.
Next, a heating process was performed at 450°C for 1 hour, and final cold-rolling was performed to produce a strip material having a thickness of approximately 0.1 mm and a width of approximately 150 mm.
In addition, a heating process was performed at 250°C for 1 hour as final annealing, and a strip material, which was obtained, was set as a strip material for evaluation of characteristics. Here, all of the heat treatments were performed in an Ar atmosphere.
The following characteristic evaluation was performed by using the obtained strip material for evaluation of characteristics.

(Method of Measuring Amount of Fe, P, Zn, Other Additional Elements, and Impurity)

In compositions of Table 1, Fe, P, Zn, and other additional elements were measured with a glow discharge mass spectrometer (GD-MS), and C was measured with an infrared absorption spectrometry.

(Mechanical Characteristics)

A test specimen of No. 13B, which is defined in JIS Z 2241: 2011 (based on ISO 6892-1: 2009), was collected from the strip material for evaluation of characteristics, and 0.2% proof stress was measured in accordance with an offset method.
In addition, the test specimen was collected in such a manner that a tensile direction during a tensile test becomes parallel to a rolling direction of the strip material for evaluation of characteristics.

(Number of Defects)

With respect to 25 sheets of copper strips which were obtained from the strip material for evaluation of characteristics and had the size of 0.2 m², the number of surface defects, which had a length of 200 µm or greater and were formed when foreign substances were exposed to a surface, was inspected. The length of the defects was set to the maximum length of a surface damage, which occurred when the foreign substances were exposed to the surface, in the rolling direction. In accordance with the evaluation method, an average number of defects (pieces/m²) was calculated.

Evaluation results are illustrated in Table 1.

[Table 1]

		Component composition						Impurity	High-temperature holding process	Average number of defects (pieces/m²)	0.2% proof stress (MPa)
		Fe (% by mass)	P (% by mass)	Zn (% by mass)	Others (% by mass)		Cu	C (ppm by mass)	High-temperature holding process	Average number of defects (pieces/m²)	0.2% proof stress (MPa)
	1	1.6	0.027	0.076	-	-	Balance	0.8	Not performed	0.2	480
	2	2.5	0.025	0.072	-	-	Balance	2.4	Not performed	1.8	481
	3	2.2	0.011	0.074	-	-	Balance	2.0	Not performed	0.4	485
	4	2.1	0.146	0.073	-	-	Balance	2.0	Not performed	0.4	484
	5	2.3	0.025	0.021	-	-	Balance	1.7	Not performed	0.2	484
	6	2.1	0.025	0.396	-	-	Balance	2.1	Not performed	0.4	483
	7	2.2	0.028	0.074	-	-	Balance	2.1	Not performed	0.4	483
	8	2.2	0.029	0.067	Ni	0.034	Balance	2.1	Not performed	0.4	508
	9	2.2	0.028	0.071	Sn	0.081	Balance	1.7	Not performed	0.2	509
	10	2.1	0.026	0.067	Mg	0.015	Balance	1.9	Not performed	0.2	509
	11	2.2	0.026	0.067	Ca	0.010	Balance	2.2	Not performed	0.4	498
	12	2.1	0.025	0.076	Sr	0.008	Balance	2.0	Not performed	0.4	498
	13	2.2	0.029	0.070	Ba	0.009	Balance	2.0	Not performed	0.4	499
	14	2.2	0.029	0.076	La	0.009	Balance	1.9	Not performed	0.2	500
	15	2.2	0.028	0.071	Zr	0.006	Balance	1.9	Not performed	0.2	506
	16	2.3	0.029	0.066	Si	0.015	Balance	1.6	Not performed	0.2	502
Examples	17	2.3	0.029	0.067	Al	0.032	Balance	2.1	Not performed	0.4	506
	18	2.1	0.025	0.071	Be	0.009	Balance	1.7	Not performed	0.2	505
	19	2.1	0.028	0.074	Ti	0.010	Balance	2.0	Not performed	0.2	506
	20	2.2	0.027	0.069	Ni	0.027	Balance	2.0	Not performed	0.2	505
	20	2.2	0.027	0.069	Co	0.032	Balance	2.0	Not performed	0.2	505
	21	2.2	0.029	0.064	Sn	0.023	Balance	2.1	Not performed	0.4	505
	21	2.2	0.029	0.064	Co	0.014	Balance	2.1	Not performed	0.4	505
	22	2.1	0.025	0.066	Ni	0.024	Balance	1.7	Not performed	0.2	507
					Sn	0.006
					Si	0.015
					Al	0.016
	23	2.1	0.026	0.071	-	-	Balance	1.8	Performed	0.2	479
	24	2.2	0.025	0.077	Ni	0.028	Balance	1.8	Performed	0.2	497
	25	2.3	0.027	0.076	Sn	0.027	Balance	1.7	Performed	0.2	508
	26	2.1	0.029	0.075	Ni	0.032	Balance	1.7	Performed	0.2	507
	26	2.1	0.029	0.075	Si	0.014	Balance	1.7	Performed	0.2	507
	27	2.7	0.026	0.066	-	-	Balance	2.9	Not performed	4.4	485
Comparative Examples	1	2.3	0.029	0.072	-	-	Balance	14.3	Not performed	11.2	483
	2	2.4	0.026	0.076	Ni	0.031	Balance	13.0	Not performed	11.0	512
	2	2.4	0.026	0.076	Si	0.011	Balance	13.0	Not performed	11.0	512

In Comparative Examples 1 and 2 in which the amount of C contained as one of the inevitable impurities exceeded the range of the invention, the number of defects was as large as 11.2 pieces/m² and 11.0 pieces/m², respectively.
In contrast, in Examples 1 to 27 in which the amount of C as the inevitable impurity was less than 3 ppm by mass, the number of defects was 4.4 pieces/m² or less, and it was confirmed that the number of defects was greatly reduced in comparison to Comparative Examples.
In Examples 8 to 22, and 24 to 26 in which Mg, Ca, Sr, Ba, the rare-earth elements, Zr, Si, Al, Be, Ti, and Co were added, the 0.2% proof stress was approximately 500 MPa, and an improvement in the strength characteristics was confirmed.
In Examples 23 to 26 in which the ingot was produced after the copper alloy molten metal was held at 1300°C, and high-temperature holding of the molten metal was performed, the number of defects was further reduced. From this result, it was confirmed that it is possible to further suppress the surface defects of the copper alloy thin sheet by performing the high-temperature holding of the copper alloy molten metal.

(Example 2)

A copper raw material composed of oxygen-free copper (ASTM B152 C10100), which had purity of 99.99% by mass or greater and in which the amount of C contained was 1 ppm by mass or less, the amount of Mn contained was 0.1 ppm by mass or less, and the amount of Ta contained was 0.1 ppm by mass or less, was prepared. The copper raw material was placed in an alumina crucible, and was melted by using a high-frequency melting furnace that was set to an Ar gas atmosphere.
As raw materials, pure iron, an Fe-Mn parent alloy, an Fe-Ta parent alloy, a Cu-Zn parent alloy, a Cu-Ni parent alloy, a Cu-Sn parent alloy, a Cu-P parent alloy, raw materials or parent alloys of Mg, Ca, Sr, Ba, rare-earth elements, Zr, Si, Al, Be, Ti, and Co were added to the resultant copper molten metal, which was obtained, according to the necessity, and an ingot (thickness of approximately 30 mm x width of approximately 150 mm x length of approximately 200 mm) having a component composition illustrated in Table 2 was produced by the same method as in Example 1. In Examples 39 to 41, a temperature of the molten metal, which was obtained, was raised once from 1200 to 1300°C, and then the ingot was produced.
A strip material for evaluation of characteristics having a thickness of approximately 0.1 mm and a width of approximately 150 mm was produced by the same method as in Example 1 by using the ingot.
The following characteristic evaluation was performed by using the obtained strip material for evaluation of characteristics.
With regard to the number of defects, both front and rear surfaces of 50 sheets of copper strips of 0.2 m², which were obtained from the strip material for evaluation of characteristics, were observed for more detailed evaluation, and the number of surface defects, which had a length of 200 µm or greater and were formed when foreign substances were exposed to a surface, was inspected. The length of the defects was set to the maximum length of a surface damage, which occurred when the foreign substances were exposed to the surface, in the rolling direction. In accordance with the evaluation method, an average number of defects (pieces/m²) was calculated.

(Method of Measuring Amount of Fe, P, Zn, Mn, Ta, Other Additional Elements, and Impurity)

Fe, P, and Zn were measured with an inductively coupled plasma atomic emission spectrometer (ICP-AES). Mn, Ta, and other additional elements were measured with the glow discharge mass spectrometer (GD-MS).
C was measured with the infrared absorption spectrometry.

Evaluation results are illustrated in Table 2.

[Table 2]

		Component composition (% by mass)						Impurities (ppm by mass)			High-temperature holding process	Average number of defects (pieces/m²)
		Fe	P	Zn	Others		Cu	C	Mn	Ta	High-temperature holding process	Average number of defects (pieces/m²)
	31	2.3	0.029	0.074	-	-	Balance	1.7	25.0	1.7	Not performed	0.50
	32	2.2	0.030	0.064	-	-	Balance	2.6	32.0	2.5	Not performed	0.85
	33	2.1	0.025	0.077	Ni	0.035	Balance	1.3	27.0	1.3	Not performed	0.35
	34	2.2	0.025	0.067	Mg	0.023	Balance	0.8	22.0	2.8	Not performed	0.20
	35	2.3	0.028	0.076	-	-	Balance	1.6	14.0	0.9	Not performed	0.15
Examples	36	2.1	0.027	0.077	-	-	Balance	2.5	7.0	0.1	Not performed	0.15
	37	2.2	0.027	0.070	Ni	0.034	Balance	1.7	15.0	0.7	Not performed	0.10
	38	2.2	0.025	0.071	Mg	0.021	Balance	1.8	14.0	0.1	Not performed	0.05
	39	2.2	0.025	0.075	-	-	Balance	1.4	4.0	0.1	Performed	0.05
	40	2.3	0.026	0.076	Ni	0.032	Balance	1.6	18.0	0.2	Performed	0.10
	41	2.3	0.024	0.066	Mg	0.030	Balance	1.8	10.0	0.1	Performed	0.10

In Examples 35 to 41 in which the amount of Mn contained as one of the inevitable impurities was defined to 20 ppm by mass or less, and the amount of Ta contained as one of the inevitable impurities was defined to 1 ppm by mass or less, the average number of defects was further reduced.
From this result, it was confirmed that it is possible to further suppress the surface defects of the copper alloy thin sheet by setting the amount of Mn contained as one of the inevitable impurities to 20 ppm by mass or less, and the amount of Ta contained as one of the inevitable impurities to 1 ppm by mass or less.

INDUSTRIAL APPLICABILITY

According to the copper alloy, the copper alloy thin sheet, and the method of manufacturing a copper alloy according to the invention, it is possible to suppress occurrence of the surface defects and the shape defect in the Cu-Fe-P-based alloy.

REFERENCE SIGNS LIST

S01:: Melting process
S02:: High-temperature holding process
S03:: Casting process
RD:: Rolling direction
L:: Length of surface defect

Claims

A copper alloy, containing:
1.5 to 2.7% by mass of Fe;

0.008 to 0.15% by mass of P; and

0.01 to 0.5% by mass ofZn, the balance being Cu and inevitable impurities,
wherein the amount of C contained as one of the inevitable impurities is less than 3 ppm by mass.
The copper alloy according to claim 1, further containing:
one or both of 0.003 to 0.5% by mass of Ni and 0.003 to 0.5% by mass of Sn.
The copper alloy according to claim 1 or 2, further containing:
at least one of Mg, Ca, Sr, Ba, rare-earth elements, Zr, Si, Al, Be, Ti, and Co in a range of 0.0007 to 0.5% by mass.
The copper alloy according to any one of claims 1 to 3,
wherein the amount of Mn contained as one of the inevitable impurities is 20 ppm by mass or less, and the amount of Ta contained as one of the inevitable impurities is 1 ppm by mass or less.
A copper alloy thin sheet that is composed of the copper alloy according to any one of claims 1 to 4,
wherein the number of surface defects, which have a length of 200 µm or greater and are formed when iron alloy particles containing Fe and C are exposed to a surface, is 5 pieces/m² or less.
The copper alloy thin sheet according to claim 5,
wherein the thickness of the thin sheet is 0.5 mm or less.
A method of manufacturing a copper alloy according to any one of claims 1 to 4, the method comprising:
a melting process of melting a raw material to produce a copper alloy molten metal;

a high-temperature holding process of holding the copper alloy molten metal at 1300°C or higher; and

a casting process of supplying the copper alloy molten metal, which is held at 1300°C or higher, into a mold so as to obtain an ingot.