The present invention relates to a copper alloy having the high strength and high electrical conductivity which is applied to a lead frame, a connector, a terminal material and the like for electric and electronic instruments and a process for producing a copper alloy, which produces this copper alloy.
Conventionally, in materials requiring electrical conductivity and spring property such as various terminals such as a lead frame and the like, a connector, a relay or a switch and the like of electronic instruments, inexpensive brass has been applied to utilities setting a high value on the manufacturing cost. On the other hand, in utilities setting a high value on a mechanical nature such as spring property and the like, phosphorus bronze has been applied thereto. Further, in addition to spring property, nickel silver has been applied to utilities setting a high value on corrosion resistance.
However, with weight saving, thinning and miniaturization of electronic instruments and parts thereof in recent years, if these materials are used, the necessary strength cannot be sufficiently satisfied under the current circumstances.
In recent years, in materials requiring electrical conductivity and spring property of various terminals and the like of electronic instruments, in place of the conventional solid-solution strengthening alloy, a representative of which is phosphorus bronze, brass and the like, a use amount of an aging hardening-type copper alloy is increasing, from a view point of the high strength and high electrical conductivity.
An aging hardening-type copper alloy is a copper alloy which, by aging-treating a supersaturated solid solution which has been solution-treated, contributes to improvement in strength property such as a proof stress or a spring limit value by uniform precipitation of fine particles, and improvement in electrical conductivity by decrease in a solid solution element amount.
Therefore, as a material satisfying demand of weight saving of electronic instruments and parts thereof, and high strengthening of materials, which are becoming severe increasingly, for example, an aging hardening-type copper alloy such as a Cu-Ni-Si alloy (Colson) and beryllium copper is used.
Additionally, as weight saving, and high strengthening of materials, improvement by a manufacturing process using a Cu-Ni-Si alloy (Colson) as a copper alloy responding to electronic instruments has been also tried. For example, Patent Literature 1 discloses a copper alloy material containing 1.0 to 5.0 mass% of Ni, 0.2 to 1.0 mass% of Si, 1.0 to 5.0 mass% of Zn, 0.1 to 0.5 mass% of Sn, and 0.003 to 0.3 mass% of P, with the remainder consisting of Cu and incidental impurities, which is obtained by a first cold rolling step of cold rolling to a thickness which is 1.3 to 1.7-fold of an objective final plate thickness, a first heat-treating step of heating a material after the first cold rolling to 700 to 900°C and, thereafter, cooling the material to 300°C or lower at a temperature lowering rate of 25°C or more per minute, a second cold rolling step of cold-rolling a material after the first heat treatment to a final plate thickness, a second heat-treating step of heating a material after the second cold rolling to 400 to 500°C, and holding it for 30 minutes to 10 hours, and a step of heating and holding a material after the second heat treatment at 400 to 550°C for 10 seconds to 3 minutes while a tensile force is applied in a longitudinal direction. However, a manufacturing step becomes complicated, and it is difficult to realize reduction in the manufacturing cost.
Improvement by addition of other metal elements utilizing this Cu-Ni-Si (Colson) alloy is disclosed (see Patent Literatures 2 to 4). For example, Patent Literature 2 describes a copper alloy for electronic materials containing Ni: 1.0 to 4.5 mass%, Si: 0.50 to 1.2 mass%, and Cr: 0.0030 to 0.3 mass% (provided that a weight ratio of Ni and Si is 3 ≤ Ni/Si ≤ 5.5), with the remainder being composed of Cu and incidental impurities, in which a Cr-Si compound having a size of 0.1 µm or more and 5 µm or less, which is dispersed in a material is such that an atomic concentration ratio of Cr relative to Si in the dispersed particle is 1 to 5, and a dispersion density thereof is 1×106/mm2 or less. However, this alloy improves the strength of a Ni-Si intermetallic compound, and there is a limit regarding the high strength and high electrical conductivity.
Further, a copper alloy in which a Cr-Si, Ni-P-Fe obtained by adding Fe to Ni-P, or Ni-Ti intermetallic compound, being an intermetallic compound different from a Ni-Si intermetallic is precipitated, is disclosed (see Patent Literatures 5 to 7). For example, Patent Literature 7 describes a copper alloy for electric and electronic instruments containing 1 to 3 mass% of Ni and 0.2 to 1.4 mass% of Ti, in which a ratio (Ni/Ti) of a mass percentage of the Ni and the Ti is 2.2 to 4.7, containing 0.02 to 0.3 mass% of one or both of Mg and Zr, and 0.1 to 5 mass% of Zn, with the remainder consisting of Cu and incidental impurities, in which the copper alloy contains at least one of an intermetallic compound consisting of Ni, Ti and Mg, an intermetallic compound consisting of Ni, Ti and Zr, or an intermetallic compound consisting of Ni, Ti, Mg, and Zr, a distribution density of the intermetallic compounds is 1×109 to 1×1013/mm2, the tensile strength is 650 MPa or more, electrical conductivity is 55 IACS% or more, and a stress relaxation ratio when held at 150°C for 1000 hours is 20% or less.
Patent Literature 8 discloses a beryllium-free precipitation hardenable copper alloy comprising 2-9% by weight nickel, 0.05-2% by weight of aluminium, chromium and silicon, with the balance being copper and impurities. The copper alloy possesses sufficient electrical conductivity to be useful in electrical applications.
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JP-A-2007-070651 - Patent Literature 2:
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GRYZIECKI JANUSZ ET AL: "The role of microadditions in the kinetic change of precipitation during the aging process of nickel-aluminium bronze",ARCHIVES OF METALLURGY, vol. 48, no. 3 (2003-01-01), pages 245-259
However, in any copper alloy, the high strength and high electrical conductivity which are possessed together are insufficient for a recent demand.
Then, the present invention was done in view of the aforementioned problems, and an object thereof is to provide a copper alloy which is excellent in workability in spite of the high strength, and is of high electrical conductivity, and a process for producing such the copper alloy.
Another object of the present invention is to provide a copper alloy which is excellent in workability in spite of the high strength, and has high electrical conductivity, and which can control physical property, and a process for producing such the copper alloy.
As the characteristic of the present invention which is the means to solve the aforementioned problems, the present inventors studied in order to obtain a high strength copper alloy and, as a result, found out that it is effective to finely precipitate a γ' phase of the L12 structure with Ni3Al in a parent phase of the FCC structure, in a Cu-Ni-Al alloy. Further, it was found out that the copper alloy is further highly strengthened by adding Si.
According to the present invention there is provided a high strength copper alloy of the FCC structure as defined in claim 1.
Therefore, the copper alloy of the present invention is a copper alloy including Ni, Al and Si in which a γ' phase of the L12 structure is precipitated at an average particle diameter of 100 nm or less, and an area fraction of the γ' phase of 5 to 40%, with Ni3(A1, Si), wherein an atom positioned at a corner is Al and Si, and an atom positioned at a face centre is Ni, in a parent phase of the copper alloy, and the high strength copper alloy has an electrical conductivity of 8.5 IACS or more, and has a Vickers hardness of 220 Hv or more.
Further features of the invention are described in the claims, which define the invention.
The process for producing a high strength copper alloy of the present invention is characterized in that raw materials are integrated, melted and mixed, and hot-worked and cold-worked and, thereafter, the mixture is solution heat-treated in a range of 700 to 1020°C for 0.1 to 10 hours and, thereafter, this
is aging-treated in a range of 400 to 650°C and 0.1 to 48 hours.
Further, the process for producing a high strength copper alloy of the present invention is further characterized in that, before or after the aging treatment, cold working at a working rate of 10 to 95% is performed.
High electrical conductivity was studied by the copper alloy of the present invention which is the means to solve the problems and, as a result, it was found out that both of the strength and electrical conductivity are satisfied in a region A and a region B. In the region A, a high strength copper alloy having, particularly, high electrical conductivity and excellent workability can be obtained and, in the region B, particularly, a high strength copper alloy having the high strength can be obtained.
Further, high electrical conductivity was studied by the process for producing a copper alloy of the present invention and, as a result, in the region A and the region B, a copper alloy satisfying both of the strength and electrical conductivity can be produced.
Fig. 1 is a photograph of a transmission electron microscope in which an upper side shows a crystal structure L12 of a precipitate according to electron beam diffraction, and a lower shows the state of a precipitate.
A best mode for carrying out the present invention will be explained below based on the drawing. In addition, a so-called person skilled in the art easily changes or modifies the present invention within the scope of the patent claims to create other embodiments. These change and modification are included in the patent claims, and the following explanation is an example of a best mode of the present invention, and does not limit the patent claims.
The copper alloy of the present invention is a copper alloy of the FCC structure containing Ni: 3.0 to 29.5 mass%, Al: 0.5 to 7.0 mass%, and Si: 0.1 to 1.5 mass%, with the remainder consisting of Cu and incidental impurities, in which a γ' phase of the L12 structure is precipitated at an average particle diameter of 100 nm or less with NiaAl including Si, in a parent phase of the copper alloy. The L12 structure can be confirmed, for example, by an arrangement structure of an electron beam diffraction image.
Fig. 1 is a photograph of a transmission electron microscope in which an upper side shows a crystal structure L12 of a precipitate by electron beam diffraction, and a lower side shows the state of a precipitate.
In addition, the present photograph is a composition of Ni: 12.3 mass%-Al: 1.0 mass%-Si: 0.3 mass%-Cu, and the composition has been subjected to solution treatment: 900°C 10 minutes-cold working 30%-aging treatment 500°C 6 hours.
As in Fig. 1, electron beam diffraction is directed to a regular phase having a diffraction plane 110. That is, the γ' phase is an intermetallic compound, and has a regularized FCC structure in which an atom positioning at a corner is Al and Si, and an atom positioning at a face center is Ni.
Further, as described later, in a lower photograph of Fig. 1, it is seen that the γ' phase of the L12 structure is finely precipitated.
Since these copper of a parent phase having the FCC structure and γ' phase having the L12 structure are both of the FCC structure, they are good in integrity, they contribute to improvement in the strength and, at the same time, a solute element concentration of a parent phase is decreased by precipitating the γ' phase, and they also contribute to improvement in electrical conductivity.
The copper alloy of the present invention is a copper alloy while it has the FCC structure. The FCC structure is a structure in which metal elements are laminated most closely, and is suitable as a parent phase alloy of the high strength and high electrical conductivity. Therefore, copper having the FCC structure is excellent in workability, and an objective shape can be easily made.
In the copper alloy of the present invention, inclusion of Ni: 3.0 to 29.5 mass%, Al: 0.5 to 7.0 mass%, and Si: 0.1 to 1.5 mass% is necessary for satisfying the high intensity and high electrical conductivity.
Ni and Al precipitate an intermetallic compound of Ni3Al to form a γ' phase in Cu of a parent phase. Further, since Al and Si together with Ni form a Ni3 (Al, Si) intermetallic compound, Al and Si together are required at an amount adapted for this system, and form not a system of Ni3Al or Ni3Si alone, but one Ni3 (Al, Si) intermetallic compound while it resides in mixture at a corner of the FCC structure in the L12 type.
The γ' phase having the L12 structure in the copper alloy of the present invention is an intermetallic compound, and has a regularized FCC structure in which an atom positioning at a corner is Al and Si, and an atom positioning at a face center is Ni.
Since these copper of a parent phase having the FCC structure and γ' phase having the L12 structure are both of the FCC structure, they are good in integrity, contribute to improvement in the strength and, at the same time, a solute element concentration of a parent phase is decreased by precipitating the γ' phase, and they also contribute to improvement in electrical conductivity.
Further, to explain in detail, since the γ' phase of the L12 structure belongs to the GCP (Geometrically close packing) phase, has ductility due to a closed packed structure thereof, and further, is high in integrity, a γ+γ' structure is formed, in which a γ' phase being a fine structure is precipitated, thereby, a copper alloy having high workability with toughness can be obtained.
This γ' phase is precipitated finely and spherically in a γ phase containing mainly copper being parent phase. Since the γ' phase is spherical, a highly workable copper alloy with toughness can be obtained without stress concentration at an interface between the γ' phase and the γ phase.
Further, by controlling an average particle diameter of the γ' phase small, it is possible to improve the strength more. By reducing an average particle diameter of the γ' phase, a pinning site of moving rearrangement is increased in the number, and the high tensile strength can be obtained.
Further, the γ' phase is an intermetallic compound, its own hardness is high, and the tensile strength is also high. Therefore, by preventing rearrangement from moving in the γ' phase, it can contribute to a hardness and the tensile strength of a copper alloy.
Further, generally, electrical conductivity is lowered as a concentration of a solute element which forms a solid solution in copper, but since a solute element concentration in a parent phase is decreased as compared with the solutionized state of a γ monophase by heat-treating an alloy at a low temperature to precipitate a γ' phase, precipitation of the γ' phase also contributes to improvement in electrical conductivity. In addition, since electrical conductivity of the γ' phase is lower than electrical conductivity of pure Cu, movement of electrons is reduced by a portion corresponding to a volumetric ratio occupied by this γ' phase, but high electrical conductivity can be maintained by adopting an area fraction of a suitable amount of the γ' phase.
Therefore, when formulated into a copper alloy, the copper alloy greatly contributes to mechanical property such as a hardness, the tensile strength and the like without considerably deteriorating ductility such as cold workability and the like, and as a second phase having the effect of improving electrical conductivity, the γ' phase is suitable. Thereupon, the area fraction of the γ' phase is 5 to 40%.
This area fraction can be obtained by comparing an area of each metal structure of a certain cross section of a copper alloy. In addition, usually, regarding an area fraction and a volume fraction, if areas of sections when two three dimensional-objects are cut with a plane parallel with a certain plane are equal in accordance with Cavalieri principle, volumes of two three dimensional-objects are equal. Therefore, there is no problem that this area fraction is grasped as a volume fraction.
In addition, the area fraction can be measured with a metal microscope, an electron microscope (SEM, TEM), EPMA (X-ray analysis apparatus) or the like.
Further, the average particle diameter of this γ' phase is 100 nm or less. A smaller average particle diameter is preferable, but it is difficult to control a practical precipitation size finer than 1 nm due to coarsening by heat treatment, and when the size is 1 nm or more and 100 nm or less, the sufficient strength can be obtained.
An average particle diameter of the γ' phase is obtained by measuring diameters of a plurality of γ' phases by image analysis from structural observation with an electron microscope, and averaging them.
Thereupon, an intermetallic compound such as Ni2 (Al, Si), NiAl, Ni5Si2 and the like other than the γ' phase of an intermetallic compound of Ni3Al is precipitated by added Ni, Al and Si, in some cases.
However, Ni2 (Al, Si) is smaller in a precipitation amount as compared with that of Ni3 (Al, Si), and influences little on a mechanical nature and an electric nature of a copper alloy.
An intermetallic compound of a β phase represented by NiAl is precipitated. This β phase is of the B2 structure of the BCC regular structure, but a compositional range at which precipitation occurs, is narrow, and if precipitated, an amount thereof is smaller as compared with that of Ni3 (Al, Si), and the β phase influences little on a mechanical nature and an electric nature of a copper alloy.
Further, an intermetallic compound of Ni5Si2 is precipitated in some cases. This Ni5Si2 is also smaller in a precipitation amount as compared with that of Ni3 (Al, Si), and influences little on a mechanical nature and an electric nature of a copper alloy.
However, precipitation of a number of respective intermetallic compounds other than the γ' phase of Ni3 (Al, Si) influences on a mechanical nature and an electric nature of a copper alloy, but does not influence thereon more than Ni3 (Al, Si). However, by combining these all precipitated products, the copper alloy of the present invention is established.
Si has the effect of reducing a concentration of a solute element in a matrix, and has the effect of increasing a volume fraction of the γ' phase and, at the same time, enhancing electrical conductivity. For this reason, the γ' phase, by becoming an intermetallic compound of Ni3 (Al, Si), is excellent in the strength and electrical conductivity as compared with a single substance of Ni3Al. It is preferable that an amount ratio of Al and Si is in a range of Al/Si=1 to 5. This is because when the Al/Si ratio is less than 1, other compounds influencing on reduction in ductility and electrical conductivity, in addition to the γ' phase, are precipitated, and when the ratio is more than 5, a volume fraction of the γ' phase is insufficient, reduction in a concentration of a solute element in a matrix is also insufficient, and increase in the strength and electrical conductivity is not sufficiently obtained.
Therefore, by adopting a range of Al: 0.5 to 7.0 mass%, and Si: 0.1 to 1.5 mass% to precipitate the γ' phase, a compositional region excellent in the high strength, high electrical conductivity, and workability can be obtained.
Further, the copper alloy of the present invention has a compositional range containing Ni: 3.0 to 14.0 mass%, Al: 0.5 to 4.0 mass%, and Si: 0.1 to 1.5 mass%, and has electrical conductivity of 8.5 IACS% or more.
By adopting this compositional range to precipitate the γ' phase of 100 nm or less, electrical conductivity can be made to be 8.5 IACS% or more.
By making electrical conductivity 8.5 IACS% or more, the copper alloy as a copper alloy having high electrical conductivity is applied to a lead frame, a connector, a terminal material and the like of electronic instruments and the like.
Further, in the copper alloy of the present invention, by adopting this compositional range to precipitate the γ' phase of 100 nm or less, further, cold workability can be made to be 10 to 95%.
Cold workability is defined as a reduction ratio of a maximum thickness at which rolling is possible with no cracking without performing annealing in the case of rolling implemented at a temperature of 20°C, and is defined as a maximum area reduction ratio at which wire drawing is possible with no cracking without performing annealing in the case of wire drawing.
Since a Ni3 (Al, Si) intermetallic compound of the γ' phase has lower workability than that of pure Cu, a working ratio cannot be increased by a portion corresponding to a ratio of a volume occupied by this Ni3 (Al, Si) intermetallic compound.
Therefore, by adopting a compositional range containing Ni: 3.0 to 14.0 mass%, Al: 0.5 to 4.0 mass%, and Si: 0.1 to 1.5 mass%, a precipitation amount of the γ' phase can be controlled to adjust cold workability at 10 to 95% while electrical conductivity is maintained high.
When cold workability is less than 10%, there is a problem that a material having an objective shape cannot be made. When cold workability exceeds 95%, there is a problem that a burden on a facility is great. Therefore, cold workability is preferably in a range of 10 to 95%, further preferably 20 to 90%.
By adjusting cold workability at 10 to 95%, the copper alloy as a copper alloy having the high strength is applied to a lead frame, a connector, a terminal material and the like of electronic instruments and the like.
Further, in the copper alloy of the present invention, addition amounts of Ni, Al and Si are in a region A surrounded by four points of (Al: 2.0 mass%, Ni: 3.0 mass%), (Al: 4.0 mass%, Ni: 9.5 mass%), (Al: 1.5 mass%, Ni: 14.0 mass%), and (Al: 0.5 mass%, Ni: 5.0 mass%), in a Ni vs Al equivalent view represented by Al equivalent (mass%) = (Al mass%+1.19Si mass%) and Ni mass%.
The copper alloy of the present invention can afford high electrical conductivity and high cold workability by residing in a range of this region A and adopting 5 to 20% of a volume fraction at which the γ' phase is precipitated.
In a range of this region A, since electrical conductivity of approximately 10 to 25 IACS% can be obtained, and cold workability of 10 to 95% can be obtained, the copper alloy as a contact material can reduce abrasion even when the material is contacted and sliding-rubbed frequently.
Therefore, the copper alloy can be applied to a lead frame, a connector, a terminal material and the like of electronic instruments and the like, as a copper alloy having high electrical conductivity and high cold workability.
Further, in the copper alloy of the present invention, Ni: 9.5 to 29.5 mass%, Al: 1.5 to 7.0 mass%, and Si: 0.1 to 1.5 mass% are contained, and a Vickers hardness is in a range of 220 to 450 Hv.
By adding a high amount of Ni to increase a volume and an area occupied by the γ' phase, a Vickers hardness can be enhanced.
In this case, by adjusting a volume fraction at which the γ' phase is precipitated, at 20 to 40%, this can contribute to the strength represented by a Vickers hardness on copper.
Thereupon, an average particle diameter of the γ' phase is preferably 100 nm or less like the above. A smaller average particle diameter is preferable, but it is difficult to perform practical precipitation completely uniformly, and the sufficient strength can be obtained at an average particle diameter of 1 nm or more and 100 nm or less, and 30 nm or less is more preferable.
In addition, in the copper alloy of the present invention, since as electrical conductivity in this compositional range, electrical conductivity of approximately 7 to 15 IACS% can be obtained, abrasion is little, and durability is good, the copper alloy can stand use for a long term, even when applied to a lead frame, a connector, a terminal material and the like of electronic instruments and the like, by possession of a high Vickers hardness together..
In addition, the copper alloy of the present invention is in a region B surrounded by four points of (Al : 4.0 mass%, Ni: 9.5 mass%), (Al: 7.0 mass%, Ni: 16.0 mass%), (Al: 2.5 mass%, Ni: 29.5 mass%), and (Al: 1.5 mass%, Ni: 14.0 mass%), in a Ni vs Al equivalent view represented by Al equivalent (mass%) = (Al mass% +1.19Si mass%) and Ni mass%.
The copper alloy of the present invention can further have the high strength represented by a Vickers hardness by residing in a range of this region B and adjusting a volume fraction at which the γ' phase is precipitated, at 25 to 40%. This is derived from that the γ' phase is an intermetallic compound, and the strength is very high. However, when an area ratio of the γ' phase is increased, there is a demerit that electrical conductivity is reduced.
Therefore, by residing in a range of this region B, the copper alloy can be also provided with a high Vickers hardness, while high electrical conductivity is obtained.
Thereby, the copper alloy can be widely applied to a lead frame, a connector, a terminal material and the like of electronic instruments and the like.
Further, in the copper alloy of the present invention, further, a total amount of 0.01 to 5.0 mass% of one or two or more elements selected from the group consisting of Co, Ti, Sn, Cr, Fe, Zr, Mg and Zn can be contained as an addition element.
Since Co, Ti, Cr and Zr stabilize the γ' phase and promote precipitation thereof, they contribute to improvement in the strength, and since they also have the effect of decreasing a concentration of a solute element in Cu, they also contribute to improvement in electrical conductivity.
Since Sn, Mg and Zn have the effect of improving stress relaxation resistance property and, at the same time, dissolve in Cu, they contribute to improvement in the strength.
Fe has the effect of miniaturization of a crystal grain by dispersion of a fine grain of Fe in Cu, and contributes to improvement in the strength and improvement in heat resistance.
An addition amount of an addition element is so that selected one or two more addition elements are contained at a total amount of 0.01 to 5.0 mass%. When a total amount of selected one or two or more addition elements is less than 0.01 mass%, there is a problem that this does not contribute to improvement in electrical conductivity and improvement in the strength, for a copper alloy. Further, when a total amount of addition elements exceeds 5.0 mass%, this contributes to improvement in electrical conductivity and improvement in the strength, but there is a problem that it becomes impossible to control electric property such as electrical conductivity and the like, and mechanical property such as a Vickers hardness and the like in a suitable range.
The copper alloy of the present invention can further contain a total amount of 0.001 to 0.5 mass% of one or two or more elements selected from the group consisting of C, P and B as an addition element.
C is thought to have the effect on miniaturization of a crystal grain, and contributes to improvement in the strength. Further, C reduces solid solubility of a solute element in Cu, and contributes to improvement in electrical conductivity.
P is used as a deoxidant, has the effect of decreasing a concentration of impurities of Cu, and contributes to improvement in electrical conductivity.
B has the effect of suppressing growth of a crystal grain and, therefore, has the effect of miniaturizing a crystal grain to improve the strength. B can improve heat resistance.
An addition amount is such that selected one or two or more addition elements are contained at a total amount of 0.001 to 0.5 mass%. When a total amount of addition elements is less than 0.001 mass%, there is a problem that addition elements do not contribute to improvement in electrical conductivity and improvement in the strength, for a copper alloy. On the other hand, when a total amount of addition elements exceeds 0. 5 mass%, there is a problem that addition elements contribute to improvement in electrical conductivity and improvement in the strength, but it becomes impossible to control electric property such as electrical conductivity and the like and mechanical property such as a Vickers hardness and the like in a suitable range.
Further, in the process for producing a copper alloy of the present invention, raw materials are integrated, melted, mixed and cast and, thereafter, the cast product is formed into a shape such as a plate material, a wire material, a tube material and the like by hot working such as hot forging and, if necessary, cold working such as cold rolling, cold wire drawing and the like. Then, the formed material is heat-treated in a range of 700 to 1020°C and 0.1 to 10 hours and, thereafter, aging-treated in a range of 400 to 650°C and 0.1 to 48 hours.
The process for producing a copper alloy of the present invention has (a) a step of integrating, melting and mixing Ni: 3.0 to 29.5 mass%, Al: 0.5 to 7.0 mass%, Si: 0.1 to 1.5 mass% and Cu to form a copper alloy material as an ingot, (b) a step of performing solution treatment of heat-treating the copper alloy material at a temperature in a range of 700°C to 1020°C for a time in a range of 0.1 to 10 hours, after the material is formed by hot working and, if necessary, cold working, and (c) a step of performing aging treatment of heating the copper alloy material after solution treatment at a temperature in a range of 400°C to 650°C for a time in a range of 0.1 to 48 hours.
In the (a) step of forming a copper alloy material, as a raw material of a copper alloy, a total amount of 0.01 to 5.0 mass% of one or two or more elements selected from the group consisting of Co, Ti, Sn, Cr, Fe, Zr, Mg and Zn can be also further added as an addition element. Further, as raw material of a copper alloy, a total amount of 0.001 to 0.5 mass% of one or two or more elements selected from the group consisting of C, P and B can be also added.
In melting and mixing, in order to prevent decrease in Al and Si due to oxidation, for example, a deoxidant such as calcium boride and the like may be used, a bubbling treatment may be performed using an argon gas or a nitrogen gas, or melting may be performed in vacuum in a vacuum container. A method of melting is not particularly limited, but a raw material may be heated at a temperature of a melting point of a copper alloy raw material or higher using the known apparatus such as a high frequency melting furnace and the like.
In the (b) step of performing solution treatment, a copper alloy material is heat-treated at a temperature in a range of 700°C to 1020°C for a time in a range of 0.1 to 10 hours. Thereby, a solid solution in which added alloy elements are uniformly homogenized in a parent phase of Cu without segregation is attained. A method of heating is not particularly limited, but heating may be performed according to the known method.
By this solution treatment, Ni, Al, Si and the like are dispersed homogeneously, thereby, the γ' phase having a fine average particle diameter of 100 nm or less can be precipitated by aging treatment described later.
In the (c) step of performing aging treatment, a copper alloy material is aging-treated at 400 to 650°C, for a time in a range of 0.1 to 48 hours. The γ' phase cannot be precipitated at lower than 400°C and/or for shorter than 0.1 hour. At higher than 650°C and/or for longer than 48 hours, a problem arises that the γ' phase is grown, an average particle diameter exceeds 100 nm, and desired electrical conductivity and working ratio cannot be obtained. Therefore, in order to obtain desired electrical conductivity and hardness, such the aging treatment becomes essential requirement.
Further, the process for producing a high strength copper alloy of the present invention is further characterized in that, before or after the aging treatment, cold working of 10 to 95% is performed.
In the process for producing a high strength copper alloy of the present invention, in addition to the aforementioned production steps, further, (d) a step of subjecting the copper alloy material to cold working of 10 to 95% before or after the aging treatment is provided.
By cold-working a copper alloy material before aging treatment, a lattice defect such as a crystal grain boundary, rearrangement, a lamination defect and the like is formed to miniaturize and working-cure a crystal grain and, at the same time, thereafter, disperse and precipitate a number of γ' phases of Ni3 (Al, Si), thereby, an average particle diameter of the γ' phase can be made to be 100 nm or less and, at the same time, a temperature of aging treatment can be lowered, and a time of aging treatment can be shortened. A method of cold working is not particularly limited, but the method may be performed by the known method such as rolling with a roller and the like.
Further, since by cold-working a copper alloy material after aging treatment, rearrangement, a lamination defect and the like can be introduced to working-cure the material, the material can be highly strengthened.
Thereupon, working is performed at a working ratio in a range of 10 to 95%. When the working ratio is less than 10%, introduction of a defect is little, and the aforementioned effect of working is not sufficiently obtained. When the working ratio exceeds 95%, a burden on a processing facility becomes great, raising a problem.
After these steps, in order to impart spring property, low temperature aging may be performed in a range of 100 to 400°C. A method of low temperature aging is not particularly limited, but the method can be performed according to the known method.
Since a copper alloy obtained by such the production process can precipitate a sufficient amount of a fine γ' phase while suppressing coarsening of a γ' phase of the L12 structure precipitating in a copper alloy, electric property such as electrical conductivity and the like, and mechanical property such as cold workability, a Vickers hardness and the like can be easily controlled.
In a range of the copper alloy of the present invention, copper alloy materials of compositions of Examples 1 to 57 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as-cast).
Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Heat treatment condition is representative production condition, and is hot rolling (900°C, rolling reduction 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity, workability, a Vickers hardness at each composition thereupon are shown.
Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of the FCC structure via production heat treatment condition steps shown in Table 3.
In Table 4, electrical conductivity and a Vickers hardness at each production condition in Table 3 are shown using copper alloys of compositions of Nos. 16 to 23 as a copper alloy.
As seen from this Table 4, under all heat treatment working conditions other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more, and a Vickers hardness was 220 Hv or more.
Then, addition elements were added. Copper alloy materials of compositions of Examples 58 to 70 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as-cast).
Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Heat treatment condition is representative production condition, and is hot rolling (900°C, rolling reduction 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity and a Vickers hardness at each composition thereupon are shown.
As seen in Table 6, under production condition of the production process of the present invention, under all of heat treatment working conditions essentially including aging treatment other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more, and a Vickers hardness was 220 Hv or more.
Then, Sn was added as an addition element.
Copper alloy materials of compositions of Examples 71 to 76 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as-cast). Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Compositions of Examples 71 to 76 are shown in the following Table 7.
*74~76 Ni13Al1Si1
Heat treatment condition is representative production condition, and is hot rolling (900°C, rolling reduction 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity and a Vickers hardness at each composition thereupon are shown.
As seen from Table 8, under production condition of the production process of the present invention, under all heat treatment working conditions essentially including aging treatment other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more.
Further, under all heat treatment working conditions essentially including aging treatment other than treatment working conditions 1, 5, 6, 7, 8, 12 and 13, a Vickers hardness was 220 Hv or more.
Then, as an addition element, Ti was added.
Copper alloy materials of compositions of Examples 77 to 82 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as-cast). Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Compositions of Examples 77 to 82 are shown in the following Table 9.
*79~82 Ni13Al1Si1
Heat treatment condition is representative production condition, and is hot rolling (900°C, rolling reduction 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity and a Vickers hardness at each composition thereupon are shown.
As seen from Table 10, under production condition of the production process of the present invention, under all heat treatment working conditions essentially including aging treatment other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more, and a Vickers hardness was 220 Hv or more.
Then, as an addition element, Zr was added.
Copper alloy materials of compositions of Examples 83 to 88 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as-cast). Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Compositions of Examples 83 to 88 are shown in the following Table 11.
*86~88 Ni13Al1Si1
Heat treatment condition is representative production condition, and is hot rolling (900°C, rolling reduction 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity and a Vickers hardness at each composition thereupon are shown.
As seen from Table 12, under production condition of the production process of the present invention, under all heat treatment working conditions essentially including aging treatment other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more, and a Vickers hardness was 220 Hv or more.
Then, as an addition element, Cr was added.
Copper alloy materials of compositions of Examples 89 to 94 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as-cast). Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Compositions of Examples 89 to 94 are shown in the following Table 13.
*92~94 Ni13Al1Si1
Heat treatment condition is representative production condition, and is hot rolling (900°C, rolling reduction 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity and a Vickers hardness at each composition thereupon are shown.
As seen from Table 14, under production condition of the production process of the present invention, under all heat treatment working conditions essentially including aging treatment other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more, and a Vickers hardness was 220 Hv or more.
Then, as an addition element, Fe was added.
Copper alloy materials of compositions of Examples 95 to 100 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as cast). Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Compositions of Examples 95 to 100 are shown in the following Table 15.
*98~100 Ni13Al1Si1
Heat treatment condition is representative production condition, and is hot rolling (900°C, rolling reduction ratio 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity and a Vickers hardness at each composition thereupon are shown.
As seen from Table 16, under production condition of the production process of the present invention, under all heat treatment working conditions essentially including aging treatment other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more, and a Vickers hardness was 220 Hv or more.
Then, as an addition element, P was added.
Copper alloy materials of compositions of Examples 101 to 106 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as-cast). Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Compositions of Examples 101 to 106 are shown in the following Table 17.
*104~106 Ni13Al1Si1
Heat treatment condition is representative production condition, and is hot rolling (900°C, rolling reduction 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity and a Vickers hardness at each composition thereupon are shown.
As seen from Table 18, under production condition of the production process of the present invention, under all heat treatment working conditions essentially including aging treatment other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more, and a Vickers hardness was 220 Hv or more.
Then, as an addition element, Zn was added.
Copper alloy materials of compositions of Examples 107 to 112 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as-cast). Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Compositions of Examples 107 to 112 are shown in the following Table 19.
*110~112 Ni13Al1Si1
Heat treatment condition is representative production condition, and is hot rolling (900°C, rolling reduction 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity and a Vickers hardness at each composition thereupon are shown.
As seen from Table 20, under production condition of the production process of the present invention, under all heat treatment working conditions essentially including aging treatment other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more, and a Vickers hardness was 220 Hv or more.
Then, as an addition element, Mg was added.
Copper alloy materials of compositions of Examples 113 to 118 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as-cast). Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Compositions of Examples 113 to 118 are shown in the following Table 21.
*116~118 Ni13Al1Si1
Heat treatment condition is representative production condition, and is hot rolling (900°C, rolling reduction 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity and a Vickers hardness at each composition thereupon are shown.
As seen from Table 22, under production condition of the production process of the present invention, under all heat treatment working conditions essentially including aging treatment other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more, and a Vickers hardness was 220 Hv or more.
Then, as an addition element, B was added.
Copper alloy materials of compositions of Examples 119 to 122 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as-cast). Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Compositions of Examples 119 to 122 are shown in the following Table 23.
*121/122 Ni13Al1Si1
Heat treatment condition is representative production condition, and is hot rolling (900°C, rolling reduction 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity and a Vickers hardness at each composition thereupon are shown.
As seen from Table 24, under production condition of the production process of the present invention, under all heat treatment working conditions essentially including aging treatment other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more, and a Vickers hardness was 220 Hv or more.
Then, as an addition element, Co was added.
Copper alloy materials of compositions of Examples 123 to 128 were integrally placed into a high frequency induction melting furnace, fused, melted and mixed. This was formulated into a cast ingot (as-cast). Thereafter, a γ' phase of the L12 structure was precipitated in a parent phase of Cu of the FCC structure.
Compositions of Examples 123 to 128 are shown in the following Table 25.
*126~128 Ni13Al1Si1
Heat treatment condition is representative productive condition, and is hot rolling (900°C, rolling reduction 90%)-solutionizing (900°C, 10 minutes)-cold rolling (20°C, rolling reduction 30%)-aging precipitation treatment (500°C, 18 hours).
Electrical conductivity and a Vickers hardness at each composition thereupon are shown.
As seen from Table 26, under production condition of the production process of the present invention, under all heat treatment working conditions essentially including aging treatment other than heat treatment working conditions 1, 5, 12 and 13, electrical conductivity was 8.5 IACS% or more, and a Vickers hardness was 220 Hv or more.
Therefore, the copper alloy of the present invention is a copper alloy having a predetermined composition, which is obtained by a predetermined production process, and since the copper alloy can precipitate a sufficient amount of a fine γ' phase while coarsening of a γ' phase of the L12 structure which is precipitated in a copper alloy is suppressed, it was seen that it can easily control electric property such as electrical conductivity and the like, and mechanical property such as cold workability, a Vickers hardness and the like.