JP2012097327A - Copper alloy improved in hot and cold workability, method for production thereof, and copper alloy strip or alloy foil obtained from copper alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Cu-Zr base copper ailloy having high strength, high electroconductivity, high elongation and excellent in hot workability and cold workability, and to provide a method for manufacturing the same and a copper alloy strip or a copper alloy foil for electronic/electric parts applying the Cu-Zr based on copper alloy.SOLUTION: The copper alloy in which the hot workability and the cold workability is improved contains, by mass, 0.01 to 0.28% of Zr and 0.0001 to 0.0012% of P as indispensable components, further contains three or more elements of 0.03 to 4% of Cr, 0.07 to 3% of Sn, 0.02 to 0.15% of Mg, 0.03 to 0.14% of Mn, 0.02 to 0.12% of Co, and 0.04 to 0.1% of Zn as additive components and the balance containg Cu with inevitable impurities.

Description

  The present invention is applied to electrical and electronic parts, has a high strength, a high elongation, a high electrical conductivity, and is excellent in hot and cold workability, a manufacturing method thereof, and a copper alloy obtained from the copper alloy It relates to strips or copper alloy foils.

  Along with the miniaturization of electric / electronic devices, the circuit to be loaded is required to have a finer pitch, and the copper alloy strip and the copper alloy foil incorporated therein are also required to be thin. However, a decrease in strength due to thinning must be avoided, and it is desired that strength be maintained even during heat treatment during lamination. Furthermore, in addition to the above strength and heat resistance, the copper foil or the like used for the battery current collector of the lithium ion secondary battery needs to be stretchable to withstand the contraction of the electrode during repeated charge and discharge. Examples of copper alloy materials that satisfy the above required characteristics include precipitation-strengthened copper alloys such as Cu—Cr, Cu—Cr—Zr, and Cu—Zr (see, for example, Patent Documents 1 to 10). ). These precipitation-strengthened copper alloys are copper alloys that not only improve strength but also have a small decrease in conductivity, so that the characteristics of both are well balanced. Among them, the Cu—Zr-based copper alloys disclosed in Patent Document 3 and Patent Documents 6 to 10 are listed as one of copper alloys that can greatly improve the heat resistance of the copper alloy by adding a small amount of Zr.

  Further, in Patent Document 1 and Patent Document 10 described above, in precipitation-strengthened copper alloys, ingot cracking and soundness deterioration during ingots are prevented, or pinhole generation and grain boundary concentration in ingots are suppressed. Therefore, it is described that the content of sulfur, oxygen and hydrogen must be reduced. Furthermore, Patent Document 11 describes that, in a Cu—Cr—Zr-based copper alloy, the content of carbon in Cr is reduced in order to ensure contact between metal Cr and molten copper.

JP-A-9-302427 JP 2008-88558 A JP 2003-89832 A JP 2006-283106 A Japanese Patent Laid-Open No. 10-330867 JP 2009-1850 A JP-A-6-33171 JP-A-3-243736 Japanese Patent Laid-Open No. 7-188810 JP 2008-255531 A JP 2010-189678 A

  The Cu-Zr-based precipitation-strengthened copper alloy is intended to improve strength by a strengthening mechanism in which a solute element excessively dissolved in a copper matrix by heat treatment is precipitated as an intermetallic compound in a high density. It is. Therefore, a solute element is often added beyond the solid solubility limit at room temperature during the melting and casting of a copper alloy. In that case, the amount of dissolved mass discharged into the liquid phase from the interface between the solid phase and the liquid phase increases during solidification, forming a partially concentrated phase of solute elements, and forming coarse microsegregation after solidification. There are things to do. When microsegregation contains phosphorus as an intermetallic compound or a constituent element, it is a crystallized product formed by phosphorus and a solute element (metal), so the surrounding copper matrix and strength, elongation, thermal conductivity, Various physical properties such as coefficient of thermal expansion differ greatly. Moreover, many of these microsegregations have a melting point lower than that of the copper matrix, and are easily formed at the grain boundaries. As a result, the strength and workability of the grain boundaries where coarse microsegregation exists are greatly reduced, and casting defects such as grain boundary cracks occur. In addition, when an ingot containing a casting defect is processed by hot rolling, cold rolling, etc., the casting defect develops by processing and changes as a defect on the surface and inside of the copper alloy strip and foil after processing. However, these defects greatly reduce the properties and quality of copper alloy strips and foils.

  From the above points, when phosphorus is included as a constituent element in the precipitation strengthened copper alloy, it is necessary to regulate not only the metal content but also the phosphorus content within a predetermined range. As described in Patent Documents 1 to 10, not only the strength improvement due to solid solution strengthening is not seen when the phosphorus content is small, but also the shear processability is lowered, and the deoxidation effect in the molten copper Cannot be obtained. On the other hand, when the phosphorus content is increased, the crystallized product of the contained metal and phosphorus is likely to be coarsened, the conductivity is decreased, the heat resistance is decreased, or the hot and cold workability is easily inhibited. Although the range of content of phosphorus is prescribed | regulated in the said patent documents 1-10, what is specifically described in the Example as the lower limit is 0.001 mass%. For example, although the above-mentioned Patent Document 1 defines that P is less than 0.01 wt%, the phosphorus content described in the examples and comparative examples is 0.001 wt% or more. As described above, in the elemental configuration of the conventional precipitation-strengthened copper alloy, it is generally performed to set the phosphorus content to 0.001% by mass or more in order to obtain effects such as strength improvement by solid solution strengthening. Yes.

  However, the Cu-Zr-based precipitation strengthened copper alloy not only suppresses the occurrence of coarse microsegregation, but also maintains high conductivity and heat resistance, and improves hot and cold workability. It is preferable to reduce the phosphorus content as much as possible. In that case, even if the phosphorus content is less than 0.001% by mass, the improvement of shear workability and the effect of deoxidation in the molten copper can be maintained to some extent, but the effect of improving the strength by solid solution strengthening can be obtained. Becomes difficult. Therefore, in a Cu—Zr-based precipitation-strengthened copper alloy, a configuration capable of improving the strength is very useful even if the phosphorus content is less than that of the conventional one. In addition, when applying precipitation-strengthening-type copper alloys as members for electric / electronic parts, it is strongly required to improve the elongation characteristics as well as the strength.

Furthermore, it cannot be said that a Cu—Zr-based precipitation-strengthened copper alloy originally has good hot and cold workability for the following reasons. The size of micro-segregation generated during casting greatly depends on the manufacturing process such as the solute concentration of the molten metal, the concentration gradient of the solute in the primary crystal, and the solidification rate. If the concentration of the additive metal element as a solute is increased in order to improve the properties of the copper alloy, microsegregation during solidification increases and castability deteriorates. In particular, in a Cu—Zr-based alloy, as the amount of Zr added is increased, Zr discharged into the liquid phase is concentrated to form a Cu—Cu ₉ Zr ₂ eutectic structure. This composition is formed by eutectic solidification of Cu and Cu ₉ Zr _2, but has a melting point of 972 ° C. and is often formed at coarse grain boundaries as shown in FIG. The large microsegregation thus formed adversely affects hot and cold workability. Therefore, in the Cu-Zr-based precipitation-strengthened copper alloy, the influence of phosphorus that causes a decrease in hot and cold workability cannot be ignored at all, and even if the phosphorus content is reduced. A decrease in production yield is inevitable, and hot workability and cold workability are lowered, so that productivity cannot be increased.

  This problem can be solved by eradicating microsegregation that occurs during casting. Therefore, in the past, not only optimizing the content of constituent elements in precipitation-strengthened copper alloys but also in-mold cooling (indirect) (Cooling) and secondary cooling have been optimized for manufacturing methods. The optimization method will be described with reference to FIG. FIG. 2 shows a general continuous casting manufacturing method for precipitation strengthened copper alloys. As shown in FIG. 2, in general continuous casting, a solidified shell is formed by mold cooling of the primary cooling, and then the mold is completely solidified by secondary cooling in which direct cooling water is sprayed and cooled to near room temperature. The ingot is manufactured with. Since the size of micro-segregation increases as the solidification rate increases, countermeasures have been taken by adjusting the balance between primary cooling and secondary cooling and slowing the solidification rate so as not to cause micro-segregation. In addition, a method of forcibly diffusing a liquid phase enriched in solute elements has been adopted.

  The method of adjusting the primary cooling and secondary cooling of such continuous casting is an effective and quick method when the concentration of the solute element is low, but since the basic principle is to delay the solidification rate, the cooling rate is low. To increase productivity. In addition, when the solute concentration is increased to improve the properties of the alloy strip and alloy foil, the solute discharge rate from the solid phase to the liquid phase becomes too high, and microsegregation is eradicated only by adjusting the cooling rate. Not. The method of stirring the molten metal is not only costly, but it does not necessarily eliminate microsegregation reliably, and is not sufficiently cost-effective. Furthermore, methods such as mechanical agitation and gas agitation are methods for forcibly agitating the molten metal through substances, and conversely, there is a possibility that the molten metal will be contaminated. All of these methods have a high risk of breakout if the manufacturing conditions are changed in a direction to eradicate microsegregation. If the range of change in the conditions is mistaken, there is a high risk of breakout, and control for safe operation is very difficult.

  From the above points, in the production of Cu—Zr-based precipitation-strengthened copper alloys, even when the phosphorus content is smaller than the conventional, production conditions for maintaining a high yield without reducing the productivity as in the conventional case Optimization of is essential.

  Therefore, in order to solve the above problems, the present invention provides a Cu-Zr-based copper alloy having high strength, high electrical conductivity, and high elongation, and excellent in hot and cold workability, a method for producing the same, and An object of the present invention is to provide a copper alloy strip or a copper alloy foil for electric and electronic parts to which the Cu-Zr copper alloy is applied.

  In order to achieve the above object, the present inventors have achieved the desired physical properties and characteristics even when the content of phosphorus contained as a constituent element is less than that in the conventional Cu-Zr copper alloy having excellent heat resistance. As a result of optimizing the type and content of the constituent elements other than phosphorus that can be used, the present invention was accomplished as a result of intensive studies on the production conditions of the Cu-Zr copper alloy. That is, the present invention has the following configuration.

(1) The present invention contains Zr: 0.01 to 0.28% and P: 0.0001 to 0.0012% as essential components in mass composition, and Cr: 0.03 to 4% as additional components Sn: 0.07-3%, Mg: 0.02-0.15%, Mn: 0.03-0.14%, Co: 0.02-0.12%, Zn: 0.04-0 Provided is a copper alloy having improved hot and cold workability, characterized in that it contains at least three kinds of elements out of 1% and the balance is made of Cu and inevitable impurities.
(2) In the present invention, the copper alloy is produced in a continuous casting process, and the produced copper alloy ingot has oxygen, hydrogen, sulfur and carbon concentrations of oxygen: 0.0005% by mass or less, hydrogen: 0 The copper alloy with improved hot and cold workability according to (1), characterized in that the content is 0.0001% by mass or less, sulfur: 0.0015% by mass or less, and carbon: 0.0005% by mass or less. I will provide a.
(3) The present invention relates to the length of the Cu—Zr-based inclusions (Cu—Cu ₉ Zr ₂ eutectic structure and Cu ₉ Zr ₂ alone) in which the copper alloy is present at the grain boundary immediately after casting. The average value of the width is 5 to 20 μm and 1 to 5 μm, respectively, and the average value of the diameters of the Cu—Zr-based inclusions (Cu—Cu ₉ Zr ₂ eutectic structure and Cu ₉ Zr ₂ alone) present in the crystal grains The copper alloy having improved hot workability and cold workability as described in (2) above is provided.
(4) The present invention is the copper alloy according to any one of (1) to (3), wherein the molten copper composed of each element component constituting the copper alloy is melted and solidified. In the temperature range of 1100 to 960 ° C., the primary cooling rate when solidification proceeds from the end of the ingot to the center direction in a cross section perpendicular to the casting direction is 20 to 46 ° C./min, and solidification is completed. The secondary cooling rate when the cooling proceeds from the end of the ingot to the central direction in a cross section perpendicular to the casting direction at a temperature of 960 to 500 ° C. is 60 to 87 ° C./min. A copper alloy having improved hot and cold workability is provided.
(5) The present invention is any one of the above (1) to (4), wherein the tensile strength is 550 N / mm ² or more, the elongation is 3% or more, and the conductivity is 60% IACS or more. A copper alloy having improved hot and cold workability is provided.
(6) The present invention is a copper alloy produced by subjecting the copper alloy according to any one of (1) to (5) above to a process of hot rolling → cold rolling → annealing → cold rolling → aging heat treatment. A surface defect having a width of 0.005 mm or more and a length of 0.1 mm or more in a thickness of 0.02 mm of the copper alloy strip or copper alloy foil. was from 0.01 to 0.0001 cells / ^{m 2} to the rolling direction of the alloy foil, and, internal defects is wide is 0.01mm or more and length 0.001 mm .1-.005 Provided is a copper alloy strip or a copper alloy foil characterized by the number of pieces / m ³ .

According to the present invention, by optimizing in the direction to reduce the phosphorus content as much as possible, while maintaining the effect of deoxidation in the molten metal and improvement of shear workability, high conductivity, high heat resistance, and hot And it can be set as the structure of the copper alloy which is excellent in cold workability. Moreover, since the microsegregation of the Cu—Cu ₉ Zr ₂ eutectic structure can be significantly suppressed by the combination of constituent metal elements other than phosphorus and the appropriate content thereof, the strength of the copper alloy should be improved by solid solution strengthening. Can do. Thereby, a Cu—Zr-based copper alloy that is applied for electric / electronic parts and has not only high strength, high conductivity, and high elongation but also excellent hot and cold workability can be obtained.

  According to the present invention, by optimizing not only the constituent elements of the Cu—Zr-based copper alloy but also the production conditions thereof, the hot and cold workability can be improved and the yield equal to or higher than that of the prior art can be ensured. At the same time, productivity can be increased.

  In addition, the copper alloy strip or copper alloy foil produced by hot and cold working using the copper alloy according to the present invention has a surface defect because the copper alloy is excellent in hot and cold workability. And it has the effect that the internal defects can be reduced very much.

It is the microstructure of the ingot cross section which the conventional Cu-Zr type | system | group copper alloy observed with the electron microscope has. It is a figure of the melting furnace and ingot cooling device which are used in a part of continuous casting process of the present invention. It is a Cu-Zr binary system equilibrium state figure. It is a figure which shows the manufacturing process of the copper alloy strip or copper alloy foil manufactured using this first clear copper alloy.

  In the present invention, phosphorus is an essential constituent component together with Zr in order to maintain the improvement of shear workability and the effect of deoxidation in the molten copper in the Cu—Zr alloy. At that time, in order to improve hot and cold workability with high conductivity and high heat resistance, it is necessary to optimize in a direction to reduce the phosphorus content in the Cu-Zr alloy.

In addition, the present invention aims to improve the strength of the copper alloy by solid solution strengthening, and to impart these functions by adding metal elements other than phosphorus as subcomponents in order to suppress microsegregation. Specifically, the metal to be added is any one of Cr, Sn, Mg, Mn, Co, and Zn. By adding these metal elements, it is possible to obtain an effect that the Cu—Cu ₉ Zr ₂ eutectic structure does not crystallize in the crystal grain boundary during the casting of the Cu—Zr alloy. These additive metal elements can further improve not only strength but also properties such as elongation when a Cu-Zr alloy is processed into strips and foils. In addition, since these additive metal elements have different functions and effects depending on the type, the strength and elongation of the copper alloy can be reduced with a smaller content than when only one type of metal element is used. Can be improved at the same time. With only one type of metal element, as described below, the addition of the metal causes a shift in the eutectic point of the Cu—Zr alloy and increases the concentration of Zr incorporated into the Cu matrix, or Cu expression of function of reducing Cu-Zr-based inclusions _(Cu-Cu 9 Zr ₂ eutectic structure and _Cu 9 Zr ₂ alone) by raising the melting point of -Zr-based inclusions suppressing the occurrence of micro segregation Therefore, the effect of simultaneously improving the strength and elongation cannot be obtained. That is, when the Cu-Zr alloy is sequentially cooled after casting, these functions appear only when the physical properties change due to the addition of one kind of metal element as the temperature decreases, and do not appear in multiple stages. As a result, only limited effects can be obtained. On the other hand, when a plurality of additive metal elements are used, a synergistic effect can be obtained by suppressing the eutectic point shift and the microsegregation in multiple stages corresponding to the change in physical properties of each metal. Due to this synergistic effect, the present invention can efficiently improve the strength and elongation of the additive metal element. In addition, since this synergistic effect is insufficient with the addition of two kinds of metal elements, in the present invention, by adding at least three kinds of metal elements, it can be obtained in multiple stages or continuously. It is preferable.

  Next, with respect to Zr and phosphorus, which are essential components of the present invention, and Cr, Sn, Mg, Mn, Co, and Zn that are additive components, the function and role of each constituent element in achieving the effects of the present invention will be described. To do.

<Zr>
Zr is a component for forming a precipitate of Zr in the copper alloy of the present invention to improve the tensile strength or the strength, and its blending amount is 0.01 to 0.28 mass. % Is preferred. As compared with phosphorus and other metals, Zr can suppress a decrease in conductivity of the copper alloy even if its content is increased. Therefore, the copper alloy of the present invention defined in a direction in which the phosphorus content is less than that of the prior art does not show a significant decrease in conductivity even when the Zr content is increased, and the effect of increasing the strength of the copper alloy Can be obtained more than ever. Thus, the Cu—Zr-based alloy of the present invention has a great feature in that it can contain a higher concentration of Zr than in the prior art. However, even if the Zr content exceeds 0.28% by mass, the strength becomes too high and the elongation decreases, adversely affecting the extrudability and workability, and the decrease in conductivity. The influence cannot be ignored. On the other hand, if the Zr content is less than 0.01% by mass, the effect of improving the strength cannot be obtained sufficiently.

<Phosphorus (P)>
Phosphorus (P) is a component capable of improving the tensile strength and strength by forming a precipitate from the compound with Zr in the copper alloy of the present invention. Moreover, it has the effect of reducing the oxygen concentration of the molten metal when adding Zr, and is added for deoxidation. That is, phosphorus reacts with oxygen in the molten metal to form P ₂ O ₅ and is easily sublimated at a temperature around 1200 ° C. and hardly remains in the molten metal. Therefore, phosphorus is often used as a deoxidizer. However, when the phosphorus content is large, the electrical conductivity, heat resistance, hot workability and cold workability tend to decrease. Therefore, in the present invention, the phosphorus content is less than 0.0012 mass compared to the conventional case. % Or less, more preferably 0.001% by mass or less. Although it is difficult to completely control the reaction between phosphorus and oxygen, in the present invention, it is easy to adjust the content of phosphorus that does not react with oxygen to 0.0012% by mass or less. The effect of phosphorus as a deoxidizer is sufficiently obtained when the content is 0.0012% by mass or less. However, if the phosphorus content is very low and less than 0.0001% by mass, the deoxidation effect becomes insufficient, so that the oxide is caught in the ingot, and the soundness of the ingot is lowered and the workability is deteriorated. To do. Moreover, the effect of improving the strength of the copper alloy obtained by adding phosphorus cannot be expected at all. Therefore, in the present invention, the phosphorus content is set in the range of 0.0001 to 0.0012% by mass, preferably 0.0001 to 0.0010% by mass.

<Co, Zn>
The eutectic point generated by the Cu—Cu ₉ Zr ₂ eutectic structure, which is a problem in Cu—Zr alloy casting, is point A in the Cu—Zr phase diagram shown in FIG. Solute concentration is locally thickened, the composition ratio of the concentrated phase Cu and Zr is that to obtain the composition ratio of this portion, Cu-Cu ₉ Zr ₂ eutectic structure is formed.

In the present invention, it was found that the eutectic point shown in FIG. 3 is shifted to the right by adding a metal element of Co or Zn to the Cu—Zr alloy. Thus, both Co and Zn are metal elements having a function of improving the strength by solid solution strengthening and solid solution strengthening in the Cu matrix. When Co or Zn is added to the Cu—Zr alloy, it is considered that there is a function of lowering the concentration gradient of Zr in the Cu matrix. When the concentration gradient is lowered, the solid solubility limit of Zu into the Cu matrix at room temperature increases, and the concentration of Zr incorporated into the Cu matrix increases. Thereby, the crystallization amount of the Cu—Cu ₉ Zr ₂ eutectic structure which is microsegregation is reduced.

  In the present invention, when the Co content is 0.02% by mass or less, the above effects cannot be obtained sufficiently. Moreover, if it exceeds 0.12 mass%, the electrical conductivity of an alloy will be reduced and the required alloy characteristic will not be obtained. Similarly, when the Zn content is less than 0.04% by mass, the above effect cannot be obtained. When the Zn content exceeds 0.1% by mass, the conductivity of the copper alloy is lowered, and the required alloy characteristics are obtained. I can't.

<Cr, Sn, Mg, Mn>
Cr, Sn, Mg, or Mn is added to the Cu—Zr alloy as a subsidiary component, and thus Cu—Zr inclusions that crystallize (Cu—Cu ₉ Zr ₂ eutectic structure and Cu ₉ Zr ₂ alone) And has a function of suppressing generation at a crystal grain boundary. These elements are simultaneously discharged into the liquid phase when Zr is concentrated in the liquid phase during solidification, and raise the melting point of the Cu-Zr inclusions. By increasing the melting point, these inclusions are dispersed in the grains rather than in the grain boundaries, and the starting point of intergranular cracking in the ingot is reduced. In addition, it is considered that the intermetallic compound crystallized in the grains is obtained by concentrating Cr, Sn, Mg, and Mn on the Cu—Zr intermetallic compound.

Cr is easily crystallized by itself in a small amount addition region, and the above effect cannot be obtained when the content is less than 0.03% by mass. When it exceeds 0.4 mass%, it tends to form a phosphorus and compounds, Cr ₃ P or Cr ₂ P such crystallizes out. These crystallized materials remain in the grain boundaries and grains without being re-dissolved in the Cu matrix even in hot rolling or in the subsequent solution treatment, thereby reducing the workability of alloy strips and alloy foils. Let Therefore, in this invention, it is necessary to make content of Cr 0.03-0.4 mass%.

Sn, Mg, or Mn has a large solid solubility limit in Cu. In a small amount addition region, Sn, Mg, or Mn is solid-solved in the Cu matrix, and the function of increasing the melting point of the Cu—Zr-based intermetallic compound cannot be obtained. The lower limit of the content is 0.07% by mass for Sn, 0.02% by mass for Mg, and 0.03% by mass for Mn. In addition, when added at a high concentration, the amount discharged to the solidification interface at the time of solidification increases, and the function of increasing the melting point of the Cu-Zr intermetallic compound also increases, but the amount of solid solution in the Cu matrix is increased. Therefore, not only does the conductivity of the alloy strip and the alloy foil decrease, but the strength of the Cu matrix increases, so stress concentrates at the grain boundary during hot working or cold working, and the grain boundary Causes cracking. In addition, Mg and Mn crystallize intermetallic compounds such as Mg ₃ P and Mn ₃ P in the same manner as Cr and lower the workability of the material. From such a viewpoint, the content of these metals is The upper limit is 0.3% by mass for Sn, 0.15% by mass for Mg, and 0.14% by mass for Mn.

<Oxygen (O ₂ ), Hydrogen (H ₂ ), Sulfur (S), Carbon (C)>
In the present invention, in order to improve the properties of the copper alloy, it is necessary to regulate the contents of oxygen, hydrogen, sulfur and carbon below a predetermined amount in addition to the above metals and phosphorus as constituent elements. Below, the influence which it has on the characteristic of the copper alloy of this invention about hydrogen, oxygen, sulfur, and carbon is demonstrated.

In the Cu-Zr alloy of the present invention, when the oxygen concentration in the ingot is high, an active compound and an acid compound such as Zr and Mg in the ingot are formed in the heat treatment step when the ingot is processed. A phenomenon called internal oxidation may be caused, and these oxides not only deteriorate the surface quality of the copper alloy strip and the copper alloy foil, but may be entangled on the surface of the material during rolling and become defects. Therefore, in the present invention, the oxygen concentration in the ingot needs to be 0.00005% by mass or less. When the concentration of hydrogen in the ingot is high, it may combine with oxygen in the ingot to form H ₂ O and expand during heat treatment such as annealing, thereby enlarging minute defects existing inside. Therefore, in the present invention, the hydrogen concentration needs to be 0.0001% by mass or less. Sulfur is a metal with a melting point as low as 112 ° C., and is the element that solidifies most slowly during casting, and solidifies in the form of segregating at the grain boundaries. Therefore, if a large amount of sulfur is contained in the ingot, sulfur at the grain boundary dissolves into the product during heating before hot rolling, and the grain boundary becomes brittle. Therefore, in the present invention, it is necessary to reduce the concentration of the sulfur component to 0.0015% by mass or less at the casting stage. In addition, Zr is an element that is easily carbonized, and when the carbon concentration in the ingot is high, Zr carbide is formed, and this carbide may become a surface defect of the copper alloy strip and the copper antibacterial foil as well as the oxide. In the present invention, the carbon concentration needs to be 0.0005 mass% or less.

  A Cu-Zr alloy is generally manufactured by a continuous casting method as shown in FIG. That is, the ingot that has passed through the melting furnace 3, the transfer rod 4, the casting rod 5, and the downcomer 6 is transferred into the mold 7, and then the ingot is subjected to primary cooling by the mold shower 8. At this time, the ingot is cooled while showing the solidification line 12. Subsequently, after the solidified shell is formed, the ingot is completely solidified by secondary cooling in which cooling water is directly sprayed by the secondary shower 9 sprayed with the shower cooling water 10, and the ingot is cooled to near room temperature. 11 is manufactured.

  The copper alloy production method of the present invention is produced by the continuous casting method shown in FIG. 2. However, since the phosphorus content is smaller than the conventional one, the microsegregation mechanism generated during casting is different from the conventional case. In order to ensure hot and cold workability equivalent to or better than the above, it is necessary to newly optimize each cooling condition for both primary cooling and secondary cooling during continuous casting. Although FIG. 2 shows a method using a shower as a cooling method, the present invention is not limited to this method. A method using cold air whose temperature is adjusted or a cooling method using both cold air and a shower may be used.

  In the present invention, the ranges of the respective cooling rates that are optimized in the temperature ranges of primary cooling (cooling during solidification) and secondary cooling (cooling after solidification) are based on the following reasons or grounds.

<Cooling rate of primary cooling (cooling during solidification)>
Although the temperature range during primary cooling (cooling during solidification) cannot be determined uniformly, in the present invention, primary cooling is performed within a range of 1100 to 960 ° C. When cooling in this temperature range, if the cooling rate exceeds 46 ° C./min, a coarse Cu—Cu ₉ Zr ₂ eutectic structure is likely to be crystallized at the grain boundaries when casting a Cu—Zr alloy. Cold workability deteriorates and manufacturing yield deteriorates. Moreover, if it is less than 20 degreeC / min, the solidified shell of sufficient thickness will not be formed in a casting_mold | template, but the risk of a breakout will increase and it will become easy to form a crack on the surface of an ingot. From the above points, the present invention needs to set the cooling rate in the temperature range of 1100 to 960 ° C. to 20 to 46 ° C./min. Here, the cooling rate defined in the present invention is such that when solidification proceeds from the end of the ingot to the center in a cross section perpendicular to the casting direction of the copper alloy, It can be obtained by measuring the time change of the temperature observed between.

<Cooling rate of secondary cooling (cooling after solidification)>
Similarly, the temperature range during secondary cooling (cooling after solidification) cannot be determined uniformly, but in the present invention, secondary cooling is performed within a range of 960 to 500 ° C. If the cooling rate exceeds 87 ° C./min when the ingot after solidification is cooled in this temperature range, the temperature difference between the center portion of the ingot and the end portion of the ingot becomes large, resulting in large casting distortion. In that case, the ingot is cracked by the stress acting on the grain boundary rather than the embrittlement of the grain boundary. In addition, when the cooling rate is less than 60 ° C./min, the ingot may not be sufficiently cooled and may be remelted under the mold, and the solute (Zr) may be highly concentrated at that portion, and eventually coarse. A Cu—Cu ₉ Zr ₂ eutectic structure crystallizes at the grain boundary, and grain boundary cracking occurs. From the above points, the present invention needs to set the cooling rate in the temperature range of 960 to 500 ° C. to 60 to 87 ° C./min. As described above, the cooling rate of the secondary cooling can be obtained by the same method as in the case of the primary cooling.

The copper alloy of the present invention is a Cu—Zr-based inclusion (Cu—Cu ₉ Zr ₂ eutectic) which is a microsegregation present in the grain boundary at the stage immediately after casting produced through the continuous casting process shown in FIG. This means not only the structure and Cu ₉ Zr ₂ alone, but also the generation at the grain boundaries is suppressed. Thereby, Cu—Zr-based inclusions are present in the crystal grains with a small shape. The crystal grain size and the Cu-Zr inclusions present in the crystal grains are identified after the Cu-Zr inclusions are identified by energy dispersive X-ray spectroscopy (SEM-EDX) using a scanning electron microscope. Can be measured. As for the size of the Cu-Zr inclusions, the length, width, or diameter of all the Cu-Zr inclusions in the SEM-EDX photographs observed at five randomly measured copper alloy samples were measured. And averaging by multiplying by magnification.

  The size of the Cu-Zr inclusions for achieving the effect of the present invention is that the average length is 5 to 20 μm and the average width is 1 to 5 μm at the grain boundaries. preferable. When the average values of length and width are less than 5 μm and less than 1 μm, respectively, the precipitation effect for improving the strength of the copper alloy cannot be obtained. On the other hand, if the average values of length and width exceed 20 μm and 5 μm, respectively, it means that the microsegregated material is large, and not only the strength of the copper alloy cannot be sufficiently improved, but also the decrease in elongation becomes remarkable. . Further, since the Cu-Zr inclusions present in the crystal grains are generally present in a shape close to a sphere, the effect of the present invention can be achieved if the size is in the range of 2 to 10 μm in diameter. . When the diameter is less than 2 μm, the effect of improving the strength of the copper alloy by precipitation of Zr is not sufficiently obtained, and when it exceeds 10 μm, microsegregation to the grain boundary is promoted, and the strength, elongation and It becomes difficult to balance characteristics such as workability.

The Cu—Zr alloy of the present invention is excellent in strength, elongation and electrical conductivity. That is, a copper alloy having a tensile strength of 520 N / mm ² or more, preferably 550 N / mm ² or more, an elongation of 3% or more, and a conductivity of 60% IACS or more. Conventional Cu—Zr alloys have a tensile strength of 370 to 440 N / mm ² , an elongation of 1.6 to 2.2, and a conductivity of less than 60% IACS. When improving the characteristics using a conventional Cu-Zr alloy, it is difficult to improve all three characteristics, whereas the Cu-Zr alloy having the structure of the present invention has these characteristics. It has a great feature in that it can improve all in good balance. When a copper alloy is applied as a copper alloy strip or copper alloy foil for high-performance electric / electronic parts, it is essential to satisfy the above ranges for all of strength, elongation and conductivity.

  FIG. 4 shows a manufacturing process of a copper alloy strip or copper alloy foil that is manufactured using the present copper alloy. Each element constituting the copper alloy is blended in a predetermined blending amount to obtain a uniform composition, and then melted in a vacuum melting furnace and filled with an inert gas such as Ar gas as shown in FIG. The molten metal is transferred to a mold through a transfer rod, and an ingot of a predetermined shape size is produced by continuous casting. Thereafter, the ingot is heated at a high temperature, and hot rolling is performed in that state. Next, the process proceeds to a cold rolling process, followed by low temperature annealing, finish rolling and aging heat treatment to produce a copper alloy foil having a predetermined thickness. The foil thus obtained can be obtained as it is or after being subjected to a rework process as a copper alloy strip or copper alloy foil for electric / electronic parts having a predetermined thickness and shape.

The copper alloy strip or copper alloy foil of the present invention produced through the process shown in FIG. 4 is uniform in characteristics, shape, thickness, etc. when applied for high-quality electrical / electronic parts such as semiconductors and batteries. In order to improve the property and homogeneity, it is necessary to reduce the surface and internal defects as much as possible. In the present invention, surface defects can be measured by observing the surface of a copper alloy having a predetermined length, width and thickness using a 50 to 400 magnification microscope. Moreover, an internal defect can be measured about the copper alloy of the same shape using an ultrasonic flaw detector. The copper alloy strip or copper alloy foil of the present invention has a surface defect having a thickness of 0.02 mm, a width of 0.005 mm or more and a length of 0.1 mm or more with respect to the rolling direction of 0.01 to 0.0001. It is preferable that the number of internal defects is in the range of 0.1 to 0.005 pieces / m ^{3 in} a range of pieces / m ² and a width of 0.001 mm or more and a length of 0.01 mm or more. If the number of surface defects and internal defects whose width and length are in the above ranges exceeds 0.01 / m ² and 0.1 / m ³ , respectively, variation in characteristics of the copper alloy is observed. Therefore, strict inspection is required for use as a high-performance electrical / electronic component, and the manufacture of the component may not be stable depending on the electrical / electronic product. Further, when the number of surface defects and internal defects is less than 0.0001 / m ² and less than 0.005 / m ^3, respectively, surface defects and internal defects are hardly seen, and there is no influence on the characteristics, The manufacturing cost of the copper alloy strip or copper alloy foil is greatly increased.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to a following example.

[Examples 1 to 12, Comparative Examples 1 to 11]
An alloy having a blending ratio of each component shown in Table 1 is melted in a vacuum melting furnace, and as shown in FIG. 2, the molten metal is transferred to a mold through a transfer rod to be filled with Ar gas. An ingot having a size of × 480 × 6000 (mm) was produced. The primary cooling (cooling during solidification) rate in the range of 1100-960 ° C. and the secondary cooling (cooling after solidification) rate in the range of 960-500 ° C. were set to the conditions shown in Table 1 during continuous casting. . The primary cooling rate and the secondary cooling rate were obtained by casting thermocouples at the center and end of the molten metal in the mold after 40 minutes from the start of casting, and measuring changes in temperature during casting. Table 2 shows the concentrations of oxygen (O ₂ ), hydrogen (H ₂ ), sulfur (S), and carbon (C) at the stage immediately after casting for each alloy shown in Table 1. Then, the ingot produced by continuous casting was heated to 900 degreeC, and it hot-rolled in the state. The crack at the time of hot rolling checked the surface of the alloy plate after rolling visually, and determined the crack. At this point, the material that could not proceed to the next cold rolling process was finished at this point and no further evaluation was performed. Only those that were not cracked by hot rolling or remained small cracks were advanced to the next cold rolling step, and cracks on the surface of the alloy sheet after cold rolling were visually determined in the same manner as during hot rolling. Furthermore, annealing, finish rolling, and aging heat treatment were performed to produce a final material (plate thickness 0.02 mm).

Each alloy plate thus obtained was evaluated for tensile strength, elongation and electrical conductivity by the following methods. Moreover, in each copper alloy obtained after the continuous casting step, the size of the Cu—Zr-based inclusions (Cu—Cu ₉ Zr ₂ eutectic structure and Cu ₉ Zr ₂ simple substance) existing in the grain boundaries and in the crystal grains Further, defects on the surface and the inner surface of the final material after processing were also determined by the following method.
(1) Tensile strength and elongation: Measured according to JIS-Z 2241.
(2) Conductivity: measured according to JIS-H 0505.
(3) Surface defect: The above-mentioned final material was cut into a length of 10 cm and a width of 10 cm, and the surface was observed using a 200 × microscope.
(4) Size of Cu-Zr inclusions: After identifying Cu-Zr inclusions by energy dispersive X-ray spectroscopy (SEM-EDX) using a scanning electron microscope at five random locations of a copper alloy sample The lengths, widths, and diameters of all Cu-Zr inclusions in the SEM-EDX photographs were measured and then averaged by multiplying them.
(5) Internal defect: The above-mentioned final material was cut into a length of 10 cm and a width of 10 cm, and the internal defect was observed using an ultrasonic flaw detector.

  Tables 3 and 4 show the evaluation results of the physical properties and characteristics of the copper alloys prepared using the blending ratios and manufacturing conditions of the respective elements shown in Table 1.

  As shown in Table 1, in Examples 1 to 8, the Zr concentration was increased, and three or four elements were added from Cr, Sn, Mg, Mn, Co, and Zn. In Examples 1 to 8, the primary cooling (cooling during solidification) rate and the secondary cooling (cooling after solidification) rate are included in the ranges of 20 to 46 ° C / min and 60 to 87 ° C / min, respectively. Manufactured under conditions. In Example 9, although the secondary cooling rate was included in the above range, casting was performed with the primary cooling rate set as large as 52 ° C./min. In Example 10, although the primary cooling rate was included in the above range, casting was performed with the secondary cooling rate set large as 116 minutes / minute. In Example 11, casting was performed with both the temporary cooling and the secondary cooling being larger than the above ranges.

  As can be seen from Tables 3 and 4, in the alloys of Examples 1 to 8, no casting cracks or hot rolling cracks occurred in all the ingots. Also in the cold rolling, the center part and cracks of the ingot were not confirmed at all, and good workability was shown. The Cu—Zr inclusions had appropriate values in the crystal grain boundaries and in the crystal grains, and there were no defects on the surface and the inner surface of the final material. In Example 9, the contents of Zr and P, and additional components Cr, Sn, Mg, Mn, Co, or Zn are within the scope of the present invention. Small cracks were observed. Therefore, various samples for characteristic evaluation were prepared in such a shape that a portion where a micro crack was observed was excluded as much as possible, and the characteristics were evaluated. Tensile strength, elongation, and conductivity showed better characteristics than before, but the size of Cu-Zr inclusions was larger at the grain boundaries and within the grains, and the number of surface and internal defects in the final product. Tends to increase, but is not at a practically problematic level. In addition, the same tendency is observed in Example 10 and Example 11, and in particular, Example 11 was cast with both the primary cooling and the secondary cooling rate set large, so that the effect of the present invention can be finally achieved. It was in a state. In addition, it is thought that the micro crack seen in the ingot of Examples 9-11 originates in the distortion which generate | occur | produces at the time of cooling. As described above, in the copper alloys of Examples 9 to 11, microcracks are likely to occur during production, and the production yield may not be lowered and the productivity may not be sufficiently improved.

In Example 12, since the addition amounts of Zr, P, and a small amount of metal components were optimized, the tensile strength, elongation, and conductivity shown in Table 3 exceeded the target values. On the other hand, as shown in Table 2, since it was a copper alloy with slightly higher contents of O ₂ , H ₂ , S and C, as shown in Table 4, the surface and internal defects of the final material increased. Therefore, in order to use the copper alloy of Example 12 for high-performance electric and electronic products, a stricter inspection process may be required for the presence or absence of surface and internal defects than the copper alloy of Examples 1-11. is there. In Example 12, the reason why the contents of O ₂ , H ₂ , S, and C are slightly increased is considered to be because the total amount of metal elements other than Cu is large, but details are unknown. . Thus, in the present invention, in order to reduce defects on the surface and the interior of the copper alloy strip or copper alloy foil, not only the size of the Cu-Zr inclusions but also the O ₂ in the copper alloy, It is preferable to reduce the contents of H ₂ , S and C.

  In Comparative Examples 1 to 4, cast ingots with small amounts of components other than Zr and P were cast, and cooling was performed within an appropriate range, and the same evaluation as in Examples was performed. As shown in Table 3, under these conditions, cracks occurred in the ingot cross section immediately after casting. In Comparative Example 1, hot rolling was performed because cracks in the ingot were minute as in Examples 9 to 11, but large cracks were generated in the process, and subsequent processing was abandoned. In Comparative Example 1, since the alloy composition was not optimized, it is considered that cracks developed during processing. Thus, in Comparative Examples 1 to 4, the effect of suppressing the segregation of Zr due to the addition of a trace component is not sufficiently obtained.

  In Comparative Examples 5 to 7, cast ingots with a large amount of components other than Zr and P were cast, and casting was performed within an appropriate range of cooling conditions, and the same evaluation as in Examples was performed. As shown in Table 3, ingot cracking did not occur under these conditions, but cracking occurred during hot rolling and cold rolling. In these ingots, the added trace metal element and P form a compound, and cracking in hot rolling and cold rolling is the starting point, or the amount of solid solution of elements such as Mg, Sn, and Mn increases. This is considered to be because stress due to strain during rolling was concentrated at the grain boundaries.

  In Comparative Examples 8 to 9, although the amount of addition of metal elements other than Zr and P was large, cracks did not occur in ingot cracking, hot rolling and cold rolling, and good workability was exhibited. Further, the Cu—Zr inclusions had appropriate values in the crystal grain boundaries and in the crystal grains, and there were no defects on the surface and the inner surface of the final material. However, although Cu—Zr inclusions are not large, the amount of solid solution of elements such as Mg, Sn, and Mn is large, the conductivity is lower than the target value, and the elongation is also greatly reduced.

  In Comparative Example 10, there are two types of metal elements added as subcomponents in addition to Zr and P. As shown in Table 3, the effect of suppressing the segregation of Zr is not sufficiently obtained by adding two kinds of metal elements, microcracks are generated in the ingot, and the conductivity and elongation of the copper alloy are also expected. It has not improved as much as I did. The fact that the effect of suppressing the segregation of Zr is insufficient can also be seen from the fact that Cu-Zr inclusions are large in the crystal grain boundaries and crystal grains as shown in Table 4. Therefore, there are many defects on the surface and inner surface of the final material.

  Comparative Example 11 was a copper alloy cast with an increased P content. As shown in Table 2, the content of sulfur (S) was slightly higher. This is thought to be due to impurities in P, but details are unknown. As shown in Table 3, a copper alloy having a high P content cannot improve elongation and conductivity as much as the copper alloy of the present invention, and it is difficult to balance the characteristics. Moreover, as shown in Table 4, the crystal grain boundaries and Cu—Zr inclusions in the crystal grains become large, and in addition, it is difficult to reduce defects on the surface and inside of the final material.

  Table 5 shows the result of comparing the characteristics of the copper alloy of the present invention and the conventional Cu-Zr alloy. According to the present invention, not only a copper alloy added with a higher concentration of Zr than conventional ones can be obtained, but also by adding at least three kinds of metal elements from Cr, Sn, Mg, Mn, Co, and Zn, More improved tensile strength, elongation and electrical conductivity.

  Furthermore, in the elemental composition of the copper alloy of the present invention in which the P content is less than that of the prior art, by optimizing the production conditions of the copper alloy, the hot and cold workability is improved and the production yield is improved. High productivity can be secured by preventing reduction. Therefore, the copper alloy strip and foil produced by the copper alloy of the present invention are extremely useful for electric / electronic parts.

1 ··· _Cu-Cu 9 Zr ₂ eutectic structure, 2 ... Cu matrix phase, 3 ... melting furnace, 4 ... transporting tubs, 5 ... casting trough, 6 ... downcomer, 7 ... mold, 8 ... mold shower, 9 ... secondary shower, 10 ... shower cooling water, 11 ... ingot, 12 ... solidification line (molten pool), 13 ... -Molten metal.

Claims (6)

  It contains Zr: 0.01-0.28% and P: 0.0001-0.0012% as essential components in the mass composition, and Cr: 0.03-4%, Sn: 0.07- as additional components 3%, Mg: 0.02-0.15%, Mn: 0.03-0.14%, Co: 0.02-0.12%, Zn: 0.04-0.1% A copper alloy having improved hot and cold workability, comprising three or more elements, the balance being Cu and inevitable impurities.   The copper alloy is produced by a continuous casting process, and the concentrations of oxygen, hydrogen, sulfur and carbon in the produced copper alloy ingot are oxygen: 0.0005% by mass or less, hydrogen: 0.0001% by mass or less, The copper alloy with improved hot and cold workability according to claim 1, wherein sulfur: 0.0015 mass% or less, carbon: 0.0005 mass% or less. In the copper alloy, the average values of the length and width of Cu—Zr-based inclusions (Cu—Cu ₉ Zr ₂ eutectic structure and Cu ₉ Zr ₂ alone) existing at the grain boundaries immediately after casting are 5 respectively. The average value of the diameters of Cu-Zr inclusions (Cu-Cu ₉ Zr ₂ eutectic structure and Cu ₉ Zr ₂ alone) existing in the crystal grains is ₂ to 10 µm. The copper alloy having improved hot and cold workability according to claim 2.   It is a copper alloy in any one of Claims 1-3, Comprising: In the temperature range of 1100-960 degreeC of the stage which melts the molten copper which consists of each element component which comprises the said copper alloy, and is solidified, casting The primary cooling rate when solidification proceeds from the end of the ingot to the center direction in a cross section perpendicular to the direction is 20 to 46 ° C./min, and is 960 to 500 in the stage of cooling after solidification is completed. At ℃, the secondary cooling rate when cooling proceeds from the end of the ingot to the center in a cross section perpendicular to the casting direction is 60 to 87 ° C / min. Copper alloy with improved workability. The hot and cold workability according to claim 1, wherein the tensile strength is 550 N / mm ² or more, the elongation is 3% or more, and the conductivity is 60% IACS or more. Improved copper alloy. The copper alloy according to any one of claims 1 to 5, wherein the copper alloy strip or the copper alloy foil is manufactured through a process of hot rolling → cold rolling → annealing → cold rolling → aging heat treatment, When the thickness of the copper alloy strip or copper alloy foil is 0.02 mm, a surface defect having a width of 0.005 mm or more and a length of 0.1 mm or more is 0. 0 mm relative to the rolling direction of the copper alloy strip or copper alloy foil. The number of internal defects is 01 to 0.0001 pieces / m ² , the width is 0.001 mm or more, and the length is 0.01 mm or more, and is characterized by 0.1 to 0.005 pieces / m ^3. Copper alloy strip or copper alloy foil.

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