HIGH-STRENGTH COPPER ALLOY

Abstract

 The present invention is a high strength copper alloy that is superior to mechanical properties, workability, corrosion resistance and economy. The present invention discloses high strength copper alloy characterized in that said copper alloy consists essentially of 4 to 19 mass percent of Zn, 0.5 to 2.5 mass percent of Si and the remaining mass percent of Cu, wherein said mass percent of Zn and said mass percent of Si satisfy the relationship Zn-2.5 • Si=0 to 15 mass percent; mean grain size D of crystalline structure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm; and 0.2% yield strength in recrystallization state of said copper alloy is higher than 250N/mm².

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to the high strength copper alloy suitable for materials comprising leads, switches, connectors, relays and sliding pieces etc. which are parts of electrical devices, electronic devices, communication equipments, information appliances, measuring instruments, automobiles and so on.

2. Prior Art

[0002] In general, high strength copper alloys are used as materials comprising leads, switches, connectors, relays and sliding pieces etc., which are used as parts of electrical devices, electronic devices, and communication devices, information appliances, measuring instruments, automobiles, and so on. Recently, their devices have been improved toward miniaturization, lightweighting, and higher efficiency, so that there are extremely severe demands for the improvements of characteristics of the materials. For example, the extremely thin plates are employed for the spring contact member of the connector. The higher strength is required for the high strength copper alloy comprising said extremely thin plates in order to thin the plate still more. It is also demanded for the high strength copper alloy to have higher balance between the strength and ductility including the bending characteristics, superiority in productivity and economy without problems of conductivity, stress relaxation characteristic, soldering characteristics, abrasion resistance, and corrosion resistance such as stress corrosion cracking resistance, dezincification corrosion resistance and migration resistance.

[0003] Incidentally, beryllium copper, titanium copper, aluminum bronze, phosphor bronze, nickel silver, brass and brass doped with Sn or Ni are generally well-known for the high strength copper alloys. However, there are following problems for these high strength copper alloys, so that it was impossible to satisfy the above demands.

[0004] The beryllium copper has the highest strength in the copper alloys, but the beryllium is extremely harmful to the humans: in particular the beryllium vapor in fusion state is significantly dangerous for the humans even in a very small amount, so that initial cost of melting arrangement becomes extremely expensive because of difficulty in disposal processes, particularly in a firing treatment of the beryllium copper materials or their products. Therefore, the melting process becomes necessary at the last step of manufacturing to obtain the predetermined characteristics, and then the problems appear in economy including the manufacturing cost.

[0005] In addition, the titanium copper shows the higher strength to next to beryllium copper, but the expensive melting arrangement is required because titanium is active element, and hence it becomes difficult to keep quality and yield in the melting. As well as the beryllium copper, since the melting process becomes necessary at the last step of manufacturing, the problems in economy appear.

[0006] For the aluminum bronze, it is difficult to obtain pure ingots because aluminum is an active element, and furthermore the aluminum bronze has the lower soldering characteristics.

[0007] Moreover, as the phosphor bronze and the nickel silver have the lower hot workability, it is difficult to produce them by hot rolling. Their alloys are usually produced with horizontal continuous casting. Consequently, their alloys are inferior in the productivity, the yield and the energy cost. Additionally, as to a spring phosphor-bronze and a spring nickel-silver which are representative copper alloys with high strength, problems in economy appear because expensive Sn and Ni are abundantly contained in the two alloys.

[0008] The brass or brass doped with Si and Ni is inexpensive, but there are problems with respect to the corrosion resistance such as the stress corrosion cracking and dezincification, and then they are unsuitable for the parts to realize miniaturization and higher efficiency.

[0009] As a result, these conventional high strength copper alloys are not satisfied as the parts used in the various devices with tendency toward miniaturization, lightweighting and higher efficiency, so that the development of a new high strength copper alloy is demanded greatly.

SUMMARY OF THE INVENTION

[0010] Present inventors have paid their attention to the Hall-Petch relationship (E. O. Hall, Proc. Phys. Soc. London. 64 (1951) 747. and N.J. Petch, J. Iron Steel Inst. 174 (1953) 25.) that 0.2% proof stress is proportional to grain size (D^-1/2), where said 0.2% proof stress is defined by the strength that permanent strain becomes 0.2%, and said 0.2% proof stress is sometimes abbreviated as "proof stress". The present inventors have considered that the high strength copper alloys satisfying the demands of said epoch can be obtained by grain refinement, and then several investigations and experiments have been performed on the grain refinement. From their results, it is found that the micronization for the crystal grain (grain refinement) of the copper alloys is realized by selecting suitably additive elements in the recrystallization. It is recognized that the strength including mainly the 0.2% proof stress is improved remarkably by making the crystal grain size smaller than a certain size and its strength also increases with decreasing of the grain size. Furthermore, from the results of various experiments with respect to influence of the additive elements for micronization of the grain size, it is clarified that addition of Si to Cu-Zn alloy increases the number of nucleation sites and addition of Co to Cu-Zn-Si alloy suppresses the grain growth. This means that Cu-Zn-Si or Cu-Zn-Si-Co alloy system with fine grains is obtained by exploiting their effects. In other words, the increase of nucleation sites is considered to be due to decreasing of stacking fault energy based on the addition of Si , and the suppression of the grain growth is considered to be due to the formation of fine precipitates based on the addition of Co.

[0011] The present invention is completed based upon these investigated results and relates to new high strength copper alloy superior in mechanical properties, workability and corrosion resistance without problems in economy. In particular the invention is suitable for materials of the parts composing several devices in tendency of miniaturization, lightweighting and higher efficiency. Accordingly, it is the object of the present invention to provide new high strength copper alloy that is extensively applied and extremely rich in utility.

[0012] Namely, it is mainly first object of the present invention to provide the high strength copper alloy (called "first invention copper alloy") suitable for rolled stocks (plates, rods and wires etc.) required high strength, or the work piece of rolled stock (press-forming product and bending product etc.), and this alloy is in the following. In addition, as parts and products suitably manufactured by use of first invention copper alloy, there are the portable or miniature communication equipments which are required thinization (to thin the plate still more) and lightweighting, electronic device parts used for personal computer, medical care instrument parts, accessory parts, machine parts, tubes or plates of heat exchanger, cooling instruments using sea water, parts composing inlet or outlet of sea water in small size ship, wiring tool parts, various instrument parts for automobile, measuring-instrument parts, play tools and daily necessities and so on. There are concretely connectors, relays, switches, sockets, springs, gears, pins, washers, coins for play, keys, tumblers, buttons, hooks, braces, diaphragms, bellows, sliding pieces, bearings, sliding pieces adjusting sound volume, bushes, fuse grips, lead frames and gauge board and so on.

[0013] It is mainly second object of the present invention to provide the high strength copper alloy (called "second invention copper alloy") suitable for rolled stocks (plates, rods and wires etc.) required highly balanced strength and electric conductivity, or the work piece of rolled stock (press-forming product and bending product etc.), where the strength required for first invention copper alloy is not needed. In addition, as parts and products suitably manufactured by use of second invention copper alloy, there are electronic device parts required electric conductivity, measuring-instrument parts, household electric appliance parts, tubes or plates of heat exchanger, cooling instruments using sea water, parts composing inlet or outlet of sea water in small size ship, machine parts, play tools and daily necessities and so on. There are concretely connectors, switches, relays, bushes, fuse grips, lead frames, wiring instruments, keys, tumblers, buttons, hooks, braces, diaphragms, bellows, sliding pieces, bearings, coins for play, and so on.

[0014] Furthermore, it is mainly third object of the present invention to provide the high strength copper alloy (called "third invention copper alloy") suitable for wire drawing materials [general wire material of round cross section and deformed wire material such as rectangle cross section (square etc.), polygon cross section (hexagon etc.) and so on] or the workpiece of wire drawing materials (bending product etc.), where the strength required for first invention copper alloy is needed. In addition, as parts and products suitably manufactured by use of third invention copper alloy, there are electronic device parts, parts for construction, accessory parts, machine parts, play tools, various instrument parts for automobile, measuring-instrument parts, electronic device parts and electrical device parts. There are concretely connectors, keys, header members, nails (nails for play instrument), washers, pins, screws, coiled springs, lead screws, shafts of copying machines etc., wire gauzes (wire gauze for culture or filter for inlet and outlet of seawater used in seawater cooling equipment and small ship etc.), sliding pieces, bearings, bolts and so on.

[0015] The first invention copper alloy consists essentially of 4 to 19 mass percent (preferably 6 to 15 mass percent, more preferably 7 to 13 mass percent) of Zn, 0.5 to 2.5 mass percent (preferably 0.9 to 2.3 mass percent, more preferably 1.3 to 2.2 mass percent)of Si and the remaining mass percent of Cu, wherein said mass percent of Zn and said mass percent of Si satisfy the relationship Zn-2.5 • Si=0 to 15 mass percent (preferably 1 to 12 mass percent, more preferably 2 to 9 mass percent); mean grain size D of crystalline structure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm (preferably 0.3 µm ≦ D ≦ 2.5 µm, more preferably 0.3 µm ≦ D ≦ 2 µm); and 0.2% proof stress in recrystallization state of said copper alloy is higher than 250N/mm² (preferably higher than 300N/mm²).

[0016] In addition, the second invention copper alloy consists essentially of 4 to 17 mass percent (preferably 5 to 13 mass percent, more preferably 6 to 11.5 mass percent) of Zn, 0.1 to 0.8 mass percent (preferably 0.2 to 0.6 mass percent, more preferably 0.2 to 0.5 mass percent) of Si and the remaining mass percent of Cu, wherein said mass percent of Zn and said mass percent of Si satisfy the relationship Zn-2.5 • Si=2 to 15 mass percent (preferably 4 to 12 mass percent, more preferably 5 to 10 mass percent); mean grain size D of crystalline structure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm (preferably 0.3 µm ≦ D ≦ 3 µm, more preferably 0.3 µm ≦ D ≦ 2.5 µm); and 0.2% proof stress in recrystallization state of said copper alloy is higher than 250N/mm² (preferably higher than 300N/mm²).

[0017] Furthermore, the third invention copper alloy consists essentially of 66 to 76 mass percent (preferably 68 to 75.5 mass percent) of Cu, 21 to 33 mass percent (preferably 22 to 31 mass percent) of Zn and 0.5 to 2 mass percent (preferably 0.8 to 1.8 mass percent, more preferably 1 to 1.7 mass percent) of Si, wherein said mass percent of Cu, said mass percent of Zn and said mass percent of Si satisfy the relationships Cu-5 • Si=62 to 67 (preferably Cu-5 • Si=63 to 66.5 mass percent) and Zn+6 • Si = 32 to 38 (preferably Zn + 6 • Si=33 to 37 mass percent); mean grain size D of crystalline structure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm (preferably 0.3 µm ≦ D ≦ 3 µm, more preferably 0.3 µm ≦ D ≦ 2.5 µm); and 0.2% proof stress in recrystallization state of said copper alloy is higher than 250N/mm² (preferably higher than 300N/mm²).

[0018] In order to obtain said each invention copper alloy, there are some cases receiving a plurality of recrystallization treatments in which a part or all of the alloy structure is recrystallized by the heat treatment. In such cases, said mean grain size D and said 0.2% proof stress in copper alloy are determined from said two physical quantities of the materials (called "recrystallization materials") obtained from the recrystallization treatment performed at last (called "last recrystallization treatment"). In the case that said recrystallization treatment is performed only once, it goes without saying that the recrystallization treatment is the last recrystallization treatment and the treated materials are the recrystallization materials.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] Each invention copper alloy is provided with any form shown in the following preferred embodiments.

(Embodiment 1)

[0020] Ingots are worked into plastic working blanks with predetermined forms by the plastic working including the hot working (rolling, extruding and forging etc.) and/or the cold working (rolling and wire drawing etc.). The plastic working blanks receive the recrystallization treatment (last recrystallization treatment) based upon heat treatment (annealing etc.) in the range of the recrystallization temperature, and then become the recrystallization materials. The recrystallization materials are rolled stocks in first and second invention copper alloys, and wire drawing materials in third invention copper alloy.

(Embodiment 2)

[0021] The recrystallization materials of said embodiment 1 are worked into the cold working materials with predetermined forms according to cold working (rolling, wire drawing and forging). The cold working materials are rolled stocks in first and second invention copper alloys, and wire drawing materials in third invention copper alloy.

(Embodiment 3)

[0022] The recrystallization materials of said embodiment 1 are worked into manufacture pieces with predetermined forms according to press working or bending etc.

(Embodiment 4)

[0023] The cold working materials of said embodiment 2 are worked into manufacture pieces with predetermined forms according to press working or bending etc.

[0024] In order to improve the property of first invention copper alloy, it is desired for the copper alloy composition to contain 0.005 to 0.5 mass percent (preferably 0.01 to 0.3 mass percent, more preferably 0.02 to 0.2 mass percent) of Co and/or 0.03 to 1.5 mass percent (preferably 0.05 to 0.7 mass percent, more preferably 0.05 to 0.5 mass percent) of Sn.

[0025] In this case, the contents of Co and Sn are determined from said each range under consideration of the content of Si. In other words, the content of Co is determined to satisfy the relationship Co/Si=0.05 to 0.5 (preferably Co/Si=0.01 to 0.3, more preferably Co/Si=0.03 to 0.2), wherein the value of Co content divided by Si content is defined by Co/Si. Additionally, the content of Sn is determined to satisfy the relationship Si/Sn≧1.5 (preferably Si/Sn≧2, more preferably Si/Sn≧3), wherein the value of Si content divided by Sn content is defined by Si/Sn.

[0026] In first invention copper alloy, it is possible for the copper alloy composition to contain 0.005 to 0.3 mass percent (preferably 0.01 to 0.2 mass percent) of Fe and/or 0.005 to 0.3 mass percent (preferably 0.01 to 0.2 mass percent) of Ni in substitution for Co or together with Co.

[0027] For said composition, the content of Fe or Ni is determined under consideration of the content of Si. In the case added with Co, the contents of Si and Co are considered. Namely, the content of Fe or Ni is determined to satisfy the relationship (Fe+Ni+Co) /Si =0.005 to 0.5 (preferably (Fe+Ni+Co) /Si =0.01 to 0.3, more preferably (Fe+Ni+Co) /Si =0.03 to 0.2), wherein the value of total contents containing Co divided by Si content is defined by (Fe+Ni+Co) /Si. It is desirable for such determination that said total content (Fe+Ni+Co) is adjusted to be 0.005 to 0.55 mass percent (more preferably 0.01 to 0.35 mass percent, much more preferably 0.02 to 0.2 mass percent).

[0028] In order to improve the characteristics more in second invention copper alloy, it is preferable to contain Co of 0.005 to 0.5 mass percent (preferably 0.01 to 0.3 mass percent, more preferably 0.02 to 0.2 mass percent) and/or Sn of 0.2 to 3 mass percent (preferably 1 to 2.6 mass percent, more preferably 1.2 to 2.5 mass percent) in alloy composition. In this case, the contents of Co and Sn are determined by considering the relation to Si content. In other words, the content of Co is determined to satisfy the relationship Co/Si=0.02 to 1.5 (preferably Co/Si=0.04 to 1, more preferably Co/Si=0.06 to 0.5) in the range described above. In addition, the content of Sn is determined to satisfy the relationship Si/Sn≦0.5 (preferably Si/Sn≦0.4, more preferably Si/Sn≦0.3) in the range described above.

[0029] In second invention copper alloy, it is possible to contain Fe of 0.005 to 0.3 mass percent (preferably 0.01 to 0.2 mass percent) and/or Ni of 0.005 to 0.3 mass percent (preferably 0.01 to 0.2 mass percent) in substitution for Co or together with Co. In this case, the content of Fe or Ni is determined by considering the content of Si (or both contents of Si and Co in case of co-adding Co). In other words, the contents of Fe and Ni are determined to satisfy the relationship (Fe+Ni+Co) /Si =0.02 to 1.5 (preferably (Fe+Ni+Co) /Si =0.04 to 1, more preferably (Fe+Ni+Co) /Si =0.06 to 0.5). It is desirable for such determination that said total content (Fe+Ni+Co) is adjusted to be 0.005 to 0.55 mass percent (preferably 0.01 to 0.35 mass percent, more preferably 0.02 to 0.25 mass percent).

[0030] Furthermore, for the first and second invention copper alloys, it is possible to contain at least one element selected from a group of P, Sb, As, Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In and Hf corresponding to characteristics required in their applications.
The contents of these elements are determined appropriately in the range of 0.003 to 0.3 mass percent.

[0031] In order to improve the characteristics of third invention copper alloy, it is preferable to contain Co of 0.005 to 0.3 mass percent (preferably 0.01 to 0.2 mass percent, more preferably 0.02 to 0.15 mass percent) and/or Sn of 0.03 to 1 mass percent (preferably 0.05 to 0.7 mass percent, more preferably 0.05 to 0.5 mass percent) in alloy composition.

[0032] In this case, the contents of Co and Sn are determined by considering the content of Si in above range. In other words, the content of Co is determined to satisfy the relationship Co/Si=0.005 to 0.4 (preferably Co/Si=0.01 to 0.2, more preferably Co/Si=0.02 to 0.15). In addition, the content of Sn is determined to satisfy the relationship Si/Sn≧1 (preferably Si/Sn≧1.5, more preferably Si/Sn≧2).

[0033] For the third invention copper alloy, it is possible to contain Fe of 0.005 to 0.3 mass percent (preferably 0.01 to 0.2 mass percent) and/or Ni of 0.005 to 0.3 mass percent (preferably 0.01 to 0.2 mass percent) in substitution for Co or together with Co.

[0034] In this case, the content of Fe or Ni is determined by considering the content of Si (or both contents of Si and Co in case of co-adding Co). In other words, the contents of Fe and Ni are determined to satisfy the relationship (Fe+Ni+Co) /Si =0.005 to 0.4 (preferably (Fe+Ni+Co) /Si =0.01 to 0.2, more preferably (Fe+Ni+Co) /Si =0.02 to 0.15). It is desirable for such determination that said total content (Fe+Ni+Co) is adjusted to be 0.005 to 0.35 mass percent (more preferably 0.01 to 0.25 mass percent, much more preferably 0.02 to 0.2 mass percent).

[0035] Furthermore, in alloy composition for third invention copper alloy, it is possible to contain at least one element selected from a group of P, Sb, As, Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In and Hf corresponding to characteristics required in their applications, where each content of P, Sb, or As is 0.005 to 0.3 mass percent and each content of Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In or Hf is 0.003 to 0.3 mass percent, and the total content in cases selecting at least one element from P, Sb and As is 0.005 to 0.25 mass percent.

[0036] By the way, the strength, particularly the 0.2% proof stress, is enhanced by the grain (recrystallized grain) refinement. The present inventors have confirmed experimentally that the 0.2% proof stress is enhanced remarkably for the mean grain size less than 3.5µm in comparison with the case larger than 3.5 µm. In addition, by reducing gradually the mean grain size D from 3.5µm, it is identified that the enhanced ratio of the proof stress increase rapidly at 3, 2.5 and 2µm. From such experimental results, it is found that the proof stress (generally higher than 250N/mm², preferably higher than 300N/mm²) required for the parts of the electrical devices, electronic devices, communication equipments and measuring instruments is ensured in the mean grain size D less than 3.5µm. In the case demanding high strength (the proof stress), it is preferable for mean grain size D to be less than 3.0µm, and in the case demanding higher strength, it is preferable to be less than 2.5µm.In order to improve rapidly the strength in the possible range, it is preferable for mean grain size D to be less than 2µm. On the other hand, although the proof stress is improved with decrease of the mean grain size D, it is predictably difficult to obtain practically grains less than 0.3µm because the smallest grain size confirmed by the experiments is 0.3µm.

[0037] From such points, in order to ensure the proof stress higher than 250N/mm² (preferably higher than 300N/mm²) in the first, second and third invention copper alloys, the recrystallized structure of 0.3µm≦D≦3.5µm is required. In other words, it is necessary that the mean grain size D in the recrystallization state (state after the last recrystallization treatment) distributes in 0.3µm ≦ D ≦ 3.5µm and 0.2% proof stress is higher than 250N/mm². In the case demanding the higher strength for the second and third invention copper alloys, it is preferable to distribute in 0.3µm≦D≦3µm, and more preferable to distribute in 0.3µm≦D≦2.5µm. On the other hand, in the first invention copper alloy required sometimes the strength higher than the second and third invention copper alloys, it is preferable to distribute in 0.3µm≦D≦2.5µm, and more preferable to distribute in 0.3µm≦D≦2µm.

[0038] Additionally, in the first to third invention copper alloys of which grain refinement is realized by recrystallization due to the suitable heat-treatment (generally annealing), such grain refinement becomes possible in alloy composition described above.

[0039] Namely, in the first to third invention copper alloys, Zn and Si cause the stacking fault energy to decrease, the dislocation density to increase, and the nucleus sites of recrystallized grain generation to increase. The functions which contributes to the grain refinement and the material strengthening due to solid solution into the Cu matrix (both functions are called "grain refinement and strengthening" as following) are given, and the contents of those elements are determined by said ranges as mentioned below. In other words, for first and second invention copper alloys used mainly as the rolled stocks or the manufacture pieces, when the functions of grain refinement and strengthening due to the addition of Zn appear enough, the content of Zn is more than 4 mass percent, and in order to improve largely the strength in first invention copper alloy, it is required that the content is more than 6 mass percent (preferably higher than 7 mass percent). For second invention copper alloy of which strength is allowed to be inferior to the first invention, it is preferable that the content is more than 5 mass percent (more preferably higher than 6 mass percent). On the other hand, when the content of Zn becomes excessively, the sensitivity of the stress-corrosion cracking increases and the bending characteristic deteriorates. Accordingly, when the relation of the content of Si for the applications of the rolled stock and the inhibition function of the stress corrosion cracking is taken into consideration, the content of Zn in the first invention copper alloy is less than 19 mass percent (preferably less than 15 mass percent, more preferably less than 13 mass percent), and the content in the second invention copper alloy is less than 17 mass percent (preferably less than 13 mass percent, more preferably less than 11.5 mass percent).

[0040] On the other hand, although the grain refinement and strengthening functions due to addition of Si appear remarkably in pretty little quantity comparing with Zn, the functions are caused by interaction with Zn. In addition, Si improves the characteristics of the stress-corrosion cracking by co-addition of Zn. However, the surplus addition of Si decreases the electric conductivity of this alloy. When these points are taken into consideration, it is required that the content of Si is higher than 0.5 mass percent for first invention copper alloy which accomplishes the strength improvement and grain refinement. The more or much more preferable content is more than 0.9 or 1.3 mass percent, respectively. However, the electric conductivity, hot workability and cold workability in first invention copper alloy are decreased by the Si content (also called the content of Si) in excess over 2.5 mass percent, and in order to keep those characteristics enough, it is preferable that the Si content is less than 2.3 mass percent, and the more preferable content is less than 2.2 mass percent.
On the other hand, in second invention copper alloy that thinks the balance between the strength and the electric conductivity important, in order to realize the grain-refinement effect required for the predetermined strength, the Si content of 0.1 mass percent at least is necessary, and it is preferable to be higher than 0.2 mass percent. However, in order to ensure the predetermined electric conductivity considering balance with strength, it is required that the Si content is less than 0.8 mass percent, and in order to ensure the electric conductivity enough to be used for the applications, it is preferable to be less than 0.6 mass percent (more preferably less than 0.5 mass percent).

[0041] Furthermore, in first and second invention copper alloys, it is necessary that balance among the effect of grain refinement, stress-corrosion cracking characteristics and the strength is kept by the co-addition of Zn and Si, but it is unsuitable in these alloys to determine independently the individual content in said range. Accordingly, it is necessary that the relation of the Zn and Si contents is specified by the relationship Zn-2.5 • Si and the values of this formulae are determined to be in above predetermined range. In order to obtain the predetermined strength based upon the grain refinement, it is necessary for first invention copper alloy to satisfy the relationship Zn-2.5 • Si ≧0 mass percent, and the preferable relationship is Zn-2.5 • Si ≧1 mass percent (more preferably Zn-2.5 • Si ≧2 mass percent), and it is necessary for second invention copper alloy to satisfy the relationship Zn-2.5 • Si ≧ 2 mass percent, and the preferable relationship is Zn-2.5 • Si ≧4 mass percent (more preferably Zn-2.5 • Si ≧5 mass percent). On the other hand, in any of first and second invention copper alloys, it is necessary to satisfy the relationship Zn-2.5 • Si ≦15 mass percent because the stress corrosion cracking arises remarkably for Zn-2.5 • Si >15 mass percent. In order to inhibit effectively the stress corrosion cracking, it is preferable to satisfy the relationship Zn-2.5 • Si ≦ 12 mass percent (more preferably Zn-2.5 • Si ≦ 9 mass percent for first invention copper alloy, and Zn-2.5 • Si ≦ 10 mass percent for second invention copper alloy).

[0042] In addition, for the Zn content in third invention copper alloy, the grain refinement and strength are rightly considered as well as first and second invention copper alloys. Furthermore, since the third invention copper alloy is mainly used as wire drawing material and its manufactured piece, the Zn content should be determined in consideration of hot extruding characteristics, so that the Zn content is set to be abundantly in comparison with first and second invention copper alloys. In order to ensure the hot extruding characteristics enough, it is necessary for Zn content to be higher than 21 mass percent. It is more preferable for Zn content to be higher than 22 mass percent so that hot extruding-wire drawing can be kept more excellent. Although the characteristics of stress-corrosion cracking resistance of third invention copper alloy is inferior in comparison with first and second invention copper alloys, this characteristics can be satisfied enough for use of wire etc. because Zn content is a little in comparison with general Cu-Zn system alloy (for example, JIS-C2700 (65Cu-35Zn)). However, in order to ensure enough the stress-corrosion cracking resistance and cold workability, it is required that Zn content of third invention copper alloy is lower than 33 mass percent. In other words, when Zn content is higher than 33 mass percent, β and γ phases are easy to remain and give a wrong influence upon the cold workability. Furthermore, the stress corrosion cracking resistance and dezincification corrosion become also problems. In order to carry out the hot extrusion-wire drawing well while the stress corrosion cracking resistance and the cold workability are ensured, it is preferable for Zn content to be less than 31 mass percent. In order to ensure the hot extrusion characteristics and the cold workability, it is necessary in third invention copper alloy to consider the Cu content, and the β and γ phases are easy to remain when the Cu content is less than 66 mass percent. On the other hand, when the content is higher than 76 mass percent, it gets difficult to perform the hot extrusion. Therefore, it is necessary for the Cu content to be 66 to 76 mass percent. Furthermore, in order to ensure the cold workability and the hot extrusion characteristics enough, it is preferable to be 68 to 75.5 mass percent.

[0043] In addition, as mentioned above, Si shows the grain refinement, strength improvement and inhibition function of stress-corrosion cracking by adding together with Zn. Accordingly, in the case that the grain refinement and strength improvement are the principal object of third invention copper alloy used as wire drawing material, it is necessary for the content of Si to be higher than 0.5 mass percent as well as first invention copper alloy. Considering that said copper alloy is utilized as wire drawing material, it is preferable to be higher than 0.8 mass percent and the most preferable to be higher than 1 mass percent. However, when the Si content becomes higher than 2 mass percent, the γ or β phase which is a factor obstructing cold workability precipitate. Therefore, it is required to be less than 2 mass percent so that the cold workability is ensured, and if considering that plenty of Zn is added, it is preferable to be less than 1.8 mass percent, and more preferable to be less than 1.7 mass percent.

[0044] Furthermore, in order to ensure the hot extrusion characteristics, cold workability and stress corrosion cracking resistance in third invention copper alloy, it is unsuitable that the individual contents of Cu, Si and Zn are determined independently. Namely, it is necessary that the contents of Cu, Si and Zn are determined so as to satisfy the relationship Cu-5 • Si = 62 to 67 mass percent and Zn-6 • Si = 32 to 38 mass percent. In other words, even though the contents of Cu, Si and Zn are in said range, the preferable hot workability can not be ensured when the contents of Cu, Si and Zn satisfy the relationships Cu-5 · Si > 67 mass percent or Zn+6 • Si < 32 mass percent. On the other hands, when Cu-5 · Si < 62 mass percent or Zn+6 • Si > 38, the cold workability worsens because concentrations of Zn and Si at grain boundary become higher, and β and γ phases became easy to remain. Additionally, it becomes easy for the stress corrosion cracking to appear, and for some applications, problems of dezincification corrosion are also caused easily.
In order to ensure enough the cold workability and stress-corrosion cracking resistance without these problems, it is preferable that the contents of Cu, Si and Zn are determined to satisfy the relationships Cu-5 • Si = 63 to 66.5 mass percent and Zn + 6 • Si = 33 to 37 mass percent.

[0045] Incidentally, the grains grow with the rise of temperature or with time, and then in the recrystallization process, the whole of grains does not recrystallize at the same time and the parts easy to recrystallize start to recrystallize at first and a long time becomes necessary until its recrystallization finish in all structures. Therefore, the crystal grains recrystallizing at the initial stage of the recrystalization process continue to grow till the recrystallization process finishes, and then the crystal grains become considerably large at the time point that all structures have recrystallized completely. Consequently, it is preferable to inhibit growth of recrystallized grains in the recrystallization, so that the fine recrystallized grains distribute uniformly in all structures. Co has a function inhibiting growth of the recrystallized grains, and this is the reason of Co addition in first to third invention copper alloys. In other words, Co combines with Si, and the growth of crystal grains is suppressed by forming fine precipitates (Co2Si of about 0.01 µm, etc.). In order that the Co shows the function inhibiting the growth of crystal grain, it is necessary for the Co content to be higher than 0.005 mass percent. All of the added Co is not concerned with formation of said precipitate but the solid solution part of Co improves the heat resistance of matrix and stress relaxation characteristic. Accordingly, in order that such functions improving stress relaxation characteristic and heat resistance are shown enough, it is preferable for all copper alloys of first to third inventions to be higher than 0.01 mass percent, and it is more preferable to be higher than 0.02 mass percent. On the other hands, when the Co addition becomes higher than 0.5 mass percent or 0.3 mass percent in the first and second invention copper alloys, and the third invention copper alloy, respectively, it is difficult to improve still more the effect of grain-growth inhibition and the improvement effect of stress relaxation characteristic needed in applications because of those saturation, and then it is useless economically. Furthermore, there is a possibility that such additions lower the bending characteristics because of enlarging of precipitating particle and increasing of precipitating amount. Therefore, it is necessary for content of Co in the first and second invention copper alloys to be lower than 0.5 mass percent and for content of Co in the third invention copper alloy to be lower than 0.3 mass percent. However, in order to show effectively said functions and to ensure bending characteristics enough, it is preferable that the contents of Co in the first and second invention copper alloys become less than 0.3 mass percent, and it is more preferable that the contents become less than 0.2 mass percent. From the same reasons, it is preferable that the content of Co in the third invention copper alloy becomes less than 0.2 mass percent, and it is more preferable that the content becomes less than 0.15 mass percent.

[0046] In addition, since Co have the close relation with Si in the grain refinement, the content of Co needs to be determined from relation to the content of Si. For the grain refinement with purpose of strength improvement required in applications, it is necessary that the ratio Co/Si in the first and third invention copper alloys is determined to be higher than 0.005 mass percent and the ratio Co/Si in the second invention copper alloy is determined to be higher than 0.02. In other words, when Co/Si dose not reach these values, there is a little formation of said precipitate and the effect of grain-growth inhibition are not shown, and then it is difficult to obtain the strength needed in applications of said invention copper alloys. Furthermore, in order to show the growth inhibition effect of crystal grain enough and improve the strength more, in the first and third invention copper alloys, it is preferable that Co/Si is higher than 0.01 and more preferable that Co/Si is high than 0.02 mass percent. In addition, the preferable and more preferable values in the second invention copper alloy are higher than 0.04 and 0.06, respectively.

[0047] As described above, in the relation to Si content, Co content must be determined to satisfy the ratio Co/Si which becomes higher than the predetermined values, and since said precipitate becomes rough and increases, the bending characteristics are obstructed. For example, when Co/Si in the first invention copper alloy used as the rolled stock becomes higher than 0.5 or Co/Si in the third invention copper alloy used as the wire drawing material or the manufactured piece becomes higher than 0.4, the bending characteristics decreases suddenly. Additionally, even in the second invention copper alloy whose strength has not to satisfy the strength condition required in the first invention copper alloy, when Co/Si exceeds 1.5, it becomes difficult to ensure the minimum condition required for the bending characteristics. Therefore, the upper limit of Co/Si must be determined by comparing said point with the effect of grain growth inhibition, taking the applications, worked history and shapes into consideration in this invention copper alloy. Concretely, the range of Co/Si is determined as follows. In other words, it is necessary that the upper limit of Co/Si in the first invention copper alloy satisfies the relationship Co/Si ≦ 0.5, and the preferable and optimum relationships are Co/Si ≦ 0.3 and Co/Si ≦ 0.2, respectively. In addition, in the second invention copper alloy, it is necessary to satisfy the relationship Co/Si ≦ 1.5, and the preferable and optimum relationships are Co/Si ≦ 1 and Co/Si ≦ 0.5, respectively. Furthermore, in the third invention copper alloy, it is necessary to satisfy the relationship Co/Si ≦ 0.4, and the preferable and optimum relationships are Co/Si ≦ 0.2 and Co/Si ≦ 0.15, respectively.

[0048] Fe and Ni show the same effect inhibiting crystal grain as Co (exactly, its effect due to Fe, Ni is less than or equal to the effect of Co). Therefore, it is possible to contain Fe, Ni as substitutive element of Co. Of course, further improvement of the effect can be expected by co-adding Fe and Ni together with Co. In the case that Fe and/or Ni are added in substitution of Co or with Co, those additions have the remarkable effect in economy because of decreasing of the expensive Co. As to the relationship (Co+Fe+Ni)/Si among the contents of Fe, Ni and Si in the case of the additions of Fe and/or Ni, the content of Fe or Ni is adjusted to be equal to the content of Co, and (Co+Fe+Ni)/Si is set to be equal to the value of Co/Si in single addition of Co, in all of first, second and third invention copper alloys. This admixture is based upon the reason described above on the relationship Co/Si between the contents of Co and Si. In other words, the relationship (Fe+Ni+Co)/Si in the first invention copper alloy is 0.005 to 0.5 (preferably 0.01 to 0.3, more preferably 0.002 to 0.2), and said relationship in the second invention copper alloy is 0.02 to 1.5 (preferably 0.04 to 1, more preferably 0.06 to 0.5), and said relationship in the third invention copper alloy is 0.005 to 0.4 (preferably 0.01 to 0.2, more preferably 0.02 to 0.15). Incidentally, since Fe and Ni can become substitutive elements with the same function as Co, the total content in the case that two or three elements selected from a group of Fe, Ni and Co are added must be equal to the content of the single addition of Co (the content of Co described above). However, in the case that two or three elements selected from Fe, Ni and Co are added, the upper limit of co-addition content of Fe, Ni and Co (total content) is permitted to be higher than the Co content by about 0.05 mass percent under consideration of the solid solution and precipitation. From said consideration, in the case that two or three elements selected from Fe, Ni and Co are co-added, it is desirable for the upper limit of total content (Fe+Ni+Co) to be set higher than the Co content by 0.05 mass percent. In other words, it is desirable that this total content (Fe+Ni+Co) in the first and second invention copper alloys are 0.005 to 0.55 mass percent (more preferably 0.01 to 0.35 mass percent, much more preferably 0.02 to 0.25 mass percent), and it is desirable that said total content in the third invention copper alloy is 0.005 to 0.35 mass percent (preferably 0.01 to 0.25 mass percent, much more preferably 0.02 to 0.2 mass percent).

[0049] Sn shows the strength improvement function, grain refinement function and improvement function of stress relaxation characteristic, corrosion resistance and wear resistance, etc. In the first and third invention copper alloys, in order to show the strength improvement function, grain refinement function, improvement function of heat resistance in matrix and improvement function of stress relaxation characteristic, corrosion resistance and wear resistance, it is necessary that the Sn content is higher than 0.03 mass percent, and it is preferable to be higher than 0.05 mass percent.
However, when the Sn content becomes higher than 1.5 mass percent or 1 mass percent in the first invention copper alloy used as the rolled stock or the third invention copper alloy used as wire drawing material, respectively, the bending characteristics decrease suddenly. Therefore, in order to ensure the bending characteristics, it is necessary that the Sn content in the first and third invention copper alloys is less than 1.5 mass percent and less than 1 mass percent, respectively. Additionally, in order to ensure enough the bending characteristics in both the first and third invention copper alloys, it is preferable for the Sn content to be less than 0.7 mass percent, and it is optimum to be less than 0.5 mass percent.

[0050] On the other hand, in the second invention copper alloy which has lower minimum strength than the first and third invention copper alloys, it is preferable to try the strength improvement, grain refinement, improvement of stress relaxation characteristic, stress corrosion crack resistance, corrosion resistance and improvement of wear resistance, while considering the relation with Si content. Accordingly, it is necessary for the Sn content to be higher than 0.2 mass percent, and it is preferable to be higher than 1 mass percent and more preferable to be higher than 1.2 mass percent corresponding to required strength. However, when the Sn content exceeds 3 mass percent, the hot workability is obstructed, and then the bending characteristics become lower, too. Therefore, in order to ensure the workability, it is necessary for Sn content to be less than 3 mass percent, and it is preferable to be less than 2.6 mass percent so as to ensure more satisfactory hot-workability and bending characteristics, and more preferable to be less than 2.5 mass percent.

[0051] Additionally, in the case that Sn is added, it is necessary that its content is determined by considering the relationship (Si/Sn) with the Si content. In the first invention copper alloy whose strength improvement is a principal purpose, when high strength is obtained with increase of Si content, ductility such as bending characteristics decreases remarkably for Si/Sn<1.5. Therefore, in the first invention copper alloy, it is necessary for the Sn content to satisfy the relationship Si/Sn ≧ 1.5. Furthermore, in order to ensure said ductility enough, it is preferable to satisfy the relationship Si/Sn ≧ 2, and it is optimum to satisfy the relationship Si/Sn ≧ 3. Moreover, in the third invention copper alloy that Sn content is suppressed to a little amount slightly comparing with the first invention copper alloy, from the same reasons described above, it is necessary for Sn content to satisfy the relationship Si/Sn ≧ 1. Furthermore, in order to ensure said ductility enough, it is preferable for the Sn content to satisfy the relationship Si/Sn ≧ 1.5, and it is optimum to satisfy the relationship Si/Sn ≧ 2.

[0052] On the other hand, in the second invention copper alloy of which electric conductivity is required so as to balance with the strength, the addition of Si is restricted. Therefore, in order to ensure the high strength without loss of the ductility, it is necessary for Sn content to satisfy the relationship Si/Sn ≦ 0.5 with Si content. For more improvement of the ductility and strength, the preferable and optimum relationships are Si/Sn ≦ 0.4 and Si/Sn ≦ 0.3, respectively.

[0053] At least one element selected from a group of P, Sb, As, Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In and Hf is added according as the applications of said alloys, and the effects are mainly the grain refinement, improvement of hot workability, improvement of corrosion resistance, action making the accessory elements mixturing inevitably harmless and improvement of stress relaxation characteristic, etc. Such effects are hardly expected in the case that the content of each element is less than 0.003 mass percent, and on the contrary the effects balanced with the additive quantity are not obtained in the case beyond 0.3 mass percent. Accordingly, the addition is useless in economy and rather loses the bending characteristics. However, in the third invention copper alloy with much Zn content, P, Sb and As are especially added for the improvement of dezincification corrosion resistance and stress corrosion cracking resistance. Similarly to the case described above, the effects of P, Pb and As added for such purposes scarcely appear in the addition less than 0.005 mass percent. On the other hand, when the P content exceeds 0.2 mass percent, adversely the cold bending characteristics are lost. Therefore, for the additions of P, Sb and As in the third invention copper alloy, it is necessary for the contents to be 0.005 to 0.2 mass percent, and in the case adding at least two kinds of element from P, Sb and As, it is necessary for the total content to be 0.005 to 0.25 mass percent.

[0054] By the way, annealing is generally adopted for the heat treatment to obtain recrystallization materials (recrystallization treatment), where the annealing keep plastic working blank mentioned in said (1) the temperature of 200 to 600 °C for 20 minutes to 10 hours. In the heat treatment usually carried out by batch processing system, when the time of heat treatment is long, the grains recrystallized at the early stage of heat treatment gradually grow, and then there is possibility that the uniform grain refinement is obstructed, even if the effect of grain growth inhibition appears by the Co addition. However, in the case with such possibility, when the heat treatment (rapid heating treatment at high temperature) of molding material is performed in a short time at higher temperature (body temperature of molding material) than general annealing temperature, the grain refinement due to the recrystallization for both Co addition and no addition is preferably carried out by the growth inhibition of early recrystallized grains. In other words, the recrystallization in many nucleation sites is realized by acting the large thermal energy almost simultaneously in a short time, because the time span generating the crystal growth is not given. To be concrete, for example, the crystalline structure of molding material are completely recrystallized by the heat treatment of said plastic working blank in the range from 450 to 750 °C for 1 to 1000 seconds.

[0055] In addition, the first, second and third invention copper alloys are generally produced as the recrystallization materials of (1), cold working materials of (2) and manufacture pieces of (3)(4), and alloy characteristics such as strength are improved more by adding the following treatment in the manufacturing process.

[0056] For example, in the case that a working rate in the cold working before obtaining the recrystallized materials is higher than 30 percent (preferably 60 percent), and more concretely when the rolling or wire drawing rate of the cold working in the process obtaining the plastic working blank of (1) is higher than 30 percent (preferably 60 percent), the strength improvement due to the grain refinement is effectively reached by promoting the refinement. In other words, in order that the grain refinement can be caused, the nucleation sites are necessary. As mentioned above, the nucleation sites increase by the cold working with the higher working rate, and the increment rate of nucleation sites becomes large with increasing of working rate. Furthermore, since the recrystallization originates in releasing of strain energy, more fine grains are obtained by increasing of shearing strain through said cold working. As a result, the strength improvement due to the grain refinement is effectively reached. Incidentally, it is preferable that the plastic working blank performed the last recrystallization treatment has the small mean size of grains, and concretely the mean grain size is less than 20 µm (preferably less than 10 µm). As the mean crystal grain size before recrystallization becomes small, the places causing the recrystallized nucleation in the following heat treatment increase, and in particular, when dislocation density at the grain boundaries becomes higher, it is easy to form nucleation sites. However, since the strength increases with decreasing of the mean grain size, the energy cost for manufacturing the high strength copper alloy becomes expensive, and manufacturing time becomes longer. Therefore, it is preferable that the mean grain size of plastic working blank in (1) is determined from balance with said working rate.
In addition, when the recrystallization materials lack the strength, this materials can obtain higher strength by performing the cold working or cold drawing with the working rate of 10 to 60 percent.

[0057] Furthermore, in the case that said plastic working blank is obtained, when the rolling or wire drawing work of one path is performed, it is preferable that the rolling or wire drawing rate is set to be large (higher than 15 percent, preferably 25 percent).
The more refinement of recrystallized grains can be realized by increment of the shearing strain and nucleation sites resulting from the cold working that the rolling and wire drawing rates are higher. In addition, if the rolling is carried out by using of the roll of small diameter or extremely large diameter, or if the wire drawing is carried out by wire dice with large dice angle or extremely small dice angle, the nucleation sites or the local distortion energy increases, so that the further refinement of recrystallized grain can be effectively realized. Furthermore, if the rolling is carried out by the rolling method with different peripheral speed, and in other words if the rolling is carried out varying the velocity by use of the rolling machine providing for top and bottom rolls having different diameters, the large shearing strain is given to the rolling material, so that the grain refinement can be reached.

[0058] Additionally, in each invention copper alloy, according to those applications, the spring elastic limit and stress relaxation characteristic can be remarkably improved by performing the suitable heat treatment (generally annealing in range of 150 to 600 °C for 1 second to 4 hours) without recrystallization. Concretely, heat treatment is carried out for the cold working materials of (2) (including cold working materials in (4)) or the manufacture pieces of (3) (4), for instance, under the condition of 200 °C for 2 hours or 600 °C for 3 seconds.

EXAMPLES

[0059] As embodiment 1, the copper alloy of composition shown in tables 1 to 4 was dissolved in atmospheric air, and prism-shaped ingots of 35 mm in thickness, 80 mm in width and 200 mm in length were obtained. And intermediate plate materials of 6 mm in thickness were formed by hot rolling (four paths) of this ingot at 850 °C, and the materials after acid cleaning became final plate materials of 1 mm in thickness by the cold rolling. Each final plate material was performed the heat treatment for one hour at temperature causing the recystallization of 100 percent (called "recrystallization temperature"), so that there were obtained the first invention copper alloy from No.101 to No.186 by performing complete recrystallization treatment of structure. For the recrystallization treatment, in advance, samples (a square plate with one side of about 20 mm) picked up from each final plate material were annealed for one hour at each temperature rising with spacing of 50 °C starting from 300 °C, and the lowest temperature causing the complete recrystallization was found out, so that the lowest temperature was determined as said recrystallization temperature of the samples (refer to Tables 15 to 17).

[0060] Furthermore, the final plate materials of the same quality (same form, same composition) as composing materials of alloy No.102, No.107, No.111, No.154 and No.180 were obtained due to the same process described above, and these final plate materials were recrystallization-treated under condition different from said condition, so that there were obtained the first invention copper alloy No.102A, No.107A, No.111A, No.154A and No.180A with the same composition as No.102, No.107, No.111, No.152 and No.175, respectively. In other words, the first invention copper alloy No.102A, No.107A, No.111A, No.154A and No.180A were obtained by the recrystallization treatment (rapid heating treatment at higher temperature) in which the heating was maintained for a short time at much higher temperature than recrystallization temperature, where the temperature a (°C) and heating time b (second) are shown as "a(b)" in the column titled "recrystallization temperature" in Tables 15 to 17. For example, "480(20)" in column of "recrystallization temperature" of No.102A in Table 15 means the heating at 480 °C for 20 seconds.

[0061] As embodiment 2, the copper alloy of composition shown in Tables 5 to 8 was dissolved in atmospheric air, and prism-shaped ingots of 35 mm in thickness, 80 mm in width and 200 mm in length were obtained. And intermediate plate materials of 6 mm in thickness are formed by hot rolling (four paths) of this ingot at 850 °C, and the materials after acid cleaning became final plate materials of 1 mm in thickness by the cold rolling. Each final plate material was performed by the heat treatment (annealing) for one hour at temperature causing the recystallization of 100 percent (by recrystallized treatment), so that there were obtained the second invention copper alloy from No.201 to No.281. In addition, the recrystallization temperature was determined in advance by method similar to example 1 (refer Table 18 to 20).

[0062] Furthermore, the final plate materials of the same quality as composing materials of alloy No.202, No.209, No.250 and No.265 were obtained due to the same process described above, and these final plate materials were recrystallized by the above-described rapid heating treatment at higher temperature, so that there were obtained the second invention copper alloy No.202A, No.209A, No.250A and No.265A with the same composition as No.202, No.209, No.250 and No.265, respectively. In other words, condition obtaining alloy No.202A, No.209A, No.250A and No.265A in the rapid heating treatment at high temperature (a (°C) and heating time b (second)) is described as "a(b)" in column titled "recrystallization temperature" of Tables 18 to 20 by the same description as Tables 15 to 17.

[0063] As embodiment 3, the copper alloy of composition shown in Tables 9 to 12 was dissolved in atmospheric air, and column-shaped ingots of 95 mm in diameter and 180 mm in length were obtained. Round bars of 12 mm in diameter were obtained by extruding press (500 t) while heating the ingots at 780 °C. This round bars after cleaning were worked by wire drawing into 8 mm in diameter, and after heat-treating the round bars for one hour at 500 °C and cleaning them, the wires of 4 mm in diameter (molding materials) were obtained by wire drawing. Furthermore, each wire was heat-treated (annealing) for 1 hour at the temperature (recrystallization temperature) that recrystallization of 100 percent was realized (recrytallization treatment), and third invention copper alloys No.301 to 397 were obtained. For the recrystallization treatment, in advance, samples (wires of 20 mm in length (4 mm in diameter)) picked up from each wire were annealed for one hour at each temperature rising with spacing of 50 °C starting from 300 °C, and the lowest temperature causing the complete recrystallization was found out, so that the lowest temperature was determined as said recrystallization temperature of the samples (refer to Tables 21 to 24).

[0064] Furthermore, the wires (molding materials) of the same quality as composing materials of alloy No.302, No.314 and No.338 were obtained due to the same process described above, and these wires were recrystallized by the above-described rapid heating treatment at higher temperature, so that there were obtained the third invention copper alloy No.302A, No.314A and No.338A with the same composition as No.302, No.314 and No.338, respectively. The condition obtaining alloy No.302A, No.314A and No.338A due to the rapid heating treatment at high temperature (temperature a (°C) and heating time b (second)) is described as "a(b)" in column titled "recrystallization temperature" of Tables 21 to 24 by the same descriptive method as Tables 15 to 17.

[0065] As comparative example 1, first comparative example alloys No.401 to No.422 shown in Table 13 were obtained on the basis of the same process as the first embodiment. In addition, as comparative example 2, second comparative example alloys No.423 to No.431 shown in Table 14 were obtained due to the same process as third embodiment. Incidentally, the first comparative example alloys No.401 to 407, respectively, have the same compositions as C2100, C2200, C2300, C2400, C2600, C2680 and C4250 of Japanese Industrial Standards (JIS), and the second comparative example alloys No.423 and 424, respectively, have the same compositions as C2600 and C2700 of JIS. Additionally, in Tables 1 to 12, the expression of relationship "(Co+Fe+Ni)/Si" for alloy that contains only Co without Fe and Ni is replaced by "Co/Si".

[0066] Incidentally, since the following problems in manufacturing process occurred for the comparative example alloys No.421, No.425, No. 427 and No.431, the manufacturing has been abandoned because of impossibility of manufacturing thereafter. In other words, No.421 causes large cracking in the step that ingots are hot-rolled, and No.425 cannot be hot-extruded. No.427 and No.431 rupture in the wire drawing process. Accordingly, their manufacturing was abandoned because it is difficult to carry out the process thereafter.

[0067] In the first invention copper alloys of No.101 to 186 and No.102A, 107A, 111A, 154A, 180A, the second invention copper alloys of No.201 to 281 and No.202A, 209A, 250A, 265A, the third invention copper alloys of No.301 to 397 and No.302A, 314A, No.338A, and the first and second comparative example alloys of No.401 to 431 (except for No.421, No. 425, No. 427 and No. 431 abandoned the manufacturing), the mean grain size D (µm) of recrystallized structures was measured on the basis of intercept method with the use of optical image (JIS-H0501). The results are shown in Tables 15 to 26.

[0068] In the first invention copper alloys of No.101 to No.186 and No.102A, 107A, 111A, 154A, 180A, the second invention copper alloys of No.201 to 281, No.202A, 209A, 250A, 265A and the first comparative example alloys No. 401 to 422 (except for No.421), the electric conductivity was measured. The results are shown in Tables 15 to 26 and Table 25. In addition, the electric conductivity (% IACS) is defined by a percentage of the ratio of the volume specific resistance of international standard soft copper (17.241 × 10^-9 µΩ • m) divided by that of said alloy.

[0069] Additionally, in the first invention copper alloys of No.101 to No.186 and No.102A, 107A, 111A, 154A, 180A, the second invention copper alloys of No.201 to 281, No.202A, 209A, 250A, 265A and the first comparative example alloys of No. 401 to 422 (except for No.421), proof stress (0.2% proof stress), tensile strength and elongation were measured by tensile test using an Amsler-type universal testing machine. Furthermore, after each alloy was cold-rolled until its thickness becomes 0.7mm, 0.2% proof stress, tensile strength and elongation of the rolling materials (called "post workpiece") were measured by the same tensile test as one described above, and then evaluation of bending characteristics and stress corrosion cracking test were carried out. The results are shown in Tables 15 to 20 and Table 26.
In addition, for the first invention copper alloys of No.101 to No.186 and No.102A, 107A, 111A, 154A, 180A and the second invention copper alloys of No.201 to 281, No.202A, 209A, 250A, 265A, it goes without saying that the post workpieces obtained by 30% rolling are also high strength copper alloy of the present invention.

[0070] In addition, the bending characteristics are evaluated from bending rate R/t at cracked moment (R: inside radius at bending positions). This cracking is suffered when the samples that are vertically cut from the worked pieces to the rolling direction are bend in W shape. In Tables 12 to 17 and Table 22, the pieces that the cracking is not caused for R/t = 0.5 are indicated by a symbol ⓞ as superior bending characteristics. The pieces that the cracking is not caused for R/t = 1.5 but is found for 0.5≦R/t<1.5 are indicated by a symbol ○ as preferable bending characteristics (there is no problem in application). The pieces that the cracking is not caused for R/t = 2.5 but is found for 1.5≦R/t<2.5 are indicated by a symbol Δ as general bending characteristics (there is problem in applications but it is possible to use). The pieces that the cracking is caused for R/t = 2.5 are indicated by a symbol × as superior bending characteristics (it is difficult for applications to use).

[0071] In addition, testing of stress corrosion cracking is carried out by use of test container and testing liquid prescribed in JISH3250, and characteristics of stress corrosion cracking resistance are evaluated from the relationship between ammonia atmosphere exposure time and stress relaxation rate (stress of proof stress value 80% of the post workpiece is added on the surface of the post workpiece) by using the fluid which mixed ammonia fluid and water, where two quantities are equal. In Tables 15 to 20 and Table 25, the pieces that the stress relaxation rate is less than 20% in the exposure for 75 hours are indicated by a symbol ⓞ as superior bending characteristics. The pieces that the stress relaxation rate is higher than 20% in the exposure for 75 hours but less than 20% in the exposure for 30 hours are indicated by a symbol ○ as superior bending characteristics (there is no problem in application). The pieces that the stress relaxation rate is less than 20% in the exposure for 12 hours are indicated by a symbol Δ as general bending characteristics (there is problem in applications but it is possible to use). The pieces that the stress relaxation rate is higher than 20% in the exposure for 12 hours are indicated by a symbol × as superior bending characteristics (it is difficult for applications to use).

[0072] Additionally, in the third invention copper alloys of No.301 to 397 and No.302A, 314A and 338A, the second invention copper alloys of No.423 to 431 (except No.425, No.427 and No.431 of abandoned manufacture), tensile strength and elongation are determined from tensile testing with use of an Amsler-type universal testing machine.
Furthermore, each alloy is straightened to 0.7 mm in thickness, and tensile strength and elongation in the wire drawing material (called "post workpiece") are determined by the same tensile testing as being described above. Additionally, evaluation of bending characteristics and testing of stress corrosion cracking are carried out. The results are shown in Tables 21 to 24 and Table 26. In addition, the post workpieces are obtained by the wire drawing of the third invention copper alloys of No.301 to 397 and No.302A, 314A and 338A and the second invention copper alloys of No.201 to 281, No.202A, 209A, 250A and 265A, and it go without saying that the after working pieces are also the high strength copper alloy of the present invention.

[0073] Additionally, the bending characteristics was evaluated from bending rate R/d when the post workpieces were bent to 90 degree by use of V-block, and the cracking was caused (R (mm): radius of curvature of inner side at the bending portion, d (mm): radius of post workpices). In Tables 18 to 22, the pieces that the cracking is not caused for R/d = 0 are indicated by a symbol ⓞ as superior bending characteristics. The pieces that the cracking is not caused for R/d = 0.25 but found for 0≦R/d<0.25 are indicated by a symbol ○ as preferable bending characteristics (there is no problem in application). The pieces that the cracking is not caused for R/d = 0.5 but found for 0.25 ≦ R/d<0.5 are indicated by a symbol Δ as general bending characteristics (there is problem in applications but it is possible to use). The pieces that the cracking is caused for R/d = 0.5 are indicated by a symbol × as inferior bending characteristics (it is difficult to use in applications).

[0074] In addition, the stress corrosion cracking test using the post workpiece used for the evaluation of bending characteristics with R/d=1.5 and 90 degree bending is carried out by use of test device and test liquid prescribed in JISH3250. After ammonia exposure using the fluid that mixed equal amounts of ammonia aqueous solution and water, and pickling due to sulfuric acid, the stress corrosion cracking resistance was evaluated from the research of cracking existence due to the stereoscopic microscope with 10 times magnification. In Tables 15 to 20 and Table 25, the pieces that the cracking is not caused in the exposure for 40 hours are indicated by a symbol ⓞ as superior corrosion cracking resistance. The pieces that the cracking is caused in the exposure for 40 hours but is not caused in the exposure for 15 hours are indicated by a symbol ○ as preferable corrosion cracking resistance (there is no problem in application). The pieces that the cracking is caused in the exposure for 15 hours but is not caused in the exposure for 6 hours are indicated by a symbol Δ as general corrosion cracking resistance (there is problem in applications but it is possible to use). The pieces that the cracking is caused in the exposure for 6 hours are indicated by a symbol × as inferior stress corrosion cracking resistance (it is difficult to use in applications).

INDUSTRIAL APPLICABILITY

[0075] As understood from Tables 15 to 26, in comparison with first and second comparative example alloys having neither alloy composition nor recrytallized structure specified at the beginning, it becomes possible for the first to third invention copper alloys to realize the grain refinement and to improve greatly the machinability and bending characteristics. It is possible for the present invention alloy to be used preferably as plate, rod and wire materials even in difficult applications in which the prior high strength copper alloy cannot be used. In addition, it is possible to obtain the grain refinement and strength improvement by the recrystallization treatment due to the rapid high temperature heating processes. Furthermore, though not shown in Tables 15 to 26, as regards said post workpiece (pieces that the cold rolling and wire drawing are performed additionally for the rolled stock and wire drawing material after the recrystallization) heat-treated for 1 second to 4 hours at 150 to 600 °C, it was confirmed that spring deflection limit and stress relaxation characteristics are greatly improved.

Claims

1. A high strength copper alloy characterized in that said copper alloy consists essentially of 4 to 19 mass percent of Zn, 0.5 to 2.5 mass percent of Si and the remaining mass percent of Cu, wherein said mass percent of Zn and said mass percent of Si satisfy the relationship Zn-2.5 • Si=0 to 15 mass percent; mean grain size D of crystalline structure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm; and 0.2% yield strength in recrystallization state of said copper alloy is higher than 250N/mm².

2. The high strength copper alloy according to Claim 1, wherein said copper alloy contains 0.005 to 0.5 mass percent of Co, wherein said mass percent of Co and said mass percent of Si satisfy the relationship Co/Si=0.005 to 0.5.

3. The high strength copper alloy according to Claim 1, wherein said copper alloy contains 0.03 to 1.5 mass percent of Sn, wherein said mass percent of Sn and said mass percent of Si satisfy the relationship Si/Sn≧1.5.

4. The high strength copper alloy according to Claim 2, wherein said copper alloy contains 0.03 to 1.5 mass percent of Sn, wherein said mass percent of Sn and said mass percent of Si satisfy the relationship Si/Sn≧1.5.

5. The high strength copper alloy according to Claim 1, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent of Fe, said mass percent of Ni and said mass percent of Si satisfy the relationship (Fe + Ni)/Si=0.005 to 0.5.

6. The high strength copper alloy according to Claim 3, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent of Fe, said mass percent of Ni and said mass percent of Si satisfy the relationship (Fe + Ni)/Si=0.005 to 0.5.

7. The high strength copper alloy according to Claim 2, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent of Fe, said mass percent of Ni, said mass percent of Co and said mass percent of Si satisfy the relationship (Fe+Ni+Co)/Si=0.005 to 0.5.

8. The high strength copper alloy according to Claim 4, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent of Fe, said mass percent of Ni, said mass percent of Co and said mass percent of Si satisfy the relationship (Fe+Ni+Co)/Si=0.005 to 0.5.

9. A high strength copper alloy characterized in that said copper alloy consists essentially of 4 to 17 mass percent of Zn, 0.1 to 0.8 mass percent of Si and the remaining mass percent of Cu, wherein said mass percent of Zn and said mass percent of Si satisfy the relationship Zn-2.5 • Si=2~15 mass percent; mean grain size D of crystalline structure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm; and 0.2% yield strength in recrystallization state of said copper alloy is higher than 250N/mm².

10. The high strength copper alloy according to Claim 9, wherein said copper alloy contains 0.005 to 0.5 mass percent of Co, wherein said mass percent Co and said mass percent of Si satisfy the relationship Co/Si=0.02 to 1.5.

11. The high strength copper alloy according to Claim 9, wherein said copper alloy contains 0.2 to 3 mass percent of Sn, wherein said mass percent of Sn and said mass percent of Si satisfy the relationship Si/Sn≦0.5.

12. The high strength copper alloy according to Claim 10, wherein said copper alloy contains 0.2 to 3 mass percent of Sn, wherein said mass percent of Sn and said mass percent of Si satisfy the relationship Si/Sn≦0.5.

13. The high strength copper alloy according to Claim 9, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent of Fe, said mass percent of Ni and said mass percent of Si satisfy the relationship (Fe+Ni)/Si=0.02 to 1.5.

14. The high strength copper alloy according to Claim 11, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent Fe, said mass percent of Ni and said mass percent of Si satisfy the relationship (Fe+Ni)/Si=0.02 to 1.5.

15. The high strength copper alloy according to Claim 10, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent of Fe, said mass percent of Ni, said mass percent of Co and said mass percent of Si satisfy the relationship (Fe+Ni+Co)/Si=0.02 to 1.5.

16. The high strength copper alloy according to Claim 12, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent of Fe, said mass percent of Ni, said mass percent of Co and said mass percent of Si satisfy the relationship (Fe+Ni+Co)/Si=0.02 to 1.5.

17. The high strength copper alloy according to any one of Claims 1 through 16, wherein said copper alloy contains at least one element selected from a group of P, Sb, As, Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In and Hf, wherein content of said element is 0.003 to 0.3 mass percent.

18. A high strength copper alloy characterized in that said copper alloy consists essentially of 66 to 76 mass percent of Cu, 21 to 33 mass percent of Zn and 0.5 to 2 mass percent of Si and the remaining mass percent of Cu, wherein said mass percent of Cu, said mass percent of Zn and said mass percent of Si satisfy the relationship Cu-5 • Si=62 to 67 mass percent and Zn+6 • Si=32 to 38 mass percent; mean grain size D of crystalline structure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm; and 0.2% yield strength in recrystallization state of said copper alloy is higher than 250N/mm².

19. The high strength copper alloy according to Claim 18, wherein said copper alloy contains 0.005 to 0.3 mass percent of Co, wherein said mass percent of Co and said mass percent of Si satisfy the relationship Co/Si=0.005 to 0.4.

20. The high strength copper alloy according to Claim 18, wherein said copper alloy contains 0.03 to 1 mass percent of Sn, wherein said mass percent of Si and said mass percent of Sn satisfy the relationship Si/Sn≧1.

21. The high strength copper alloy according to Claim 19, wherein said copper alloy contains 0.03 to 1 mass percent of Sn, wherein said mass percent of Si and said mass percent of Sn satisfy the relationship Si/Sn≧1.

22. The high strength copper alloy according to Claim 18, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent of Fe, said mass percent of Ni and said mass percent of Si satisfy the relationship (Fe+Ni)/Si=0.005 to 0.4.

23. The high strength copper alloy according to Claim 20, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent of Fe, said mass percent of Ni and said mass percent of Si satisfy the relationship (Fe+Ni)/Si=0.005 to 0.4.

24. The high strength copper alloy according to Claim 19, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent of Fe, said mass percent of Ni, said mass percent of Co and said mass percent of Si satisfy the relationship (Fe+Ni+Co)/Si=0.005 to 0.4.

25. The high strength copper alloy according to Claim 21, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent of Fe, said mass percent of Ni, said mass percent of Co and said mass percent of Si satisfy the relationship (Fe+Ni+Co)/Si=0.005 to 0.4.

26. The high strength copper alloy according to any one of Claims 18 through 25, wherein said copper alloy contains at least one element selected from a group of P, Sb, As, Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In and Hf, wherein content of P, Sb, or As is 0.005 to 0.3 mass percent, content of Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In or Hf is 0.003 to 0.3 mass percent, and total content in a case selected from at least P, Sb or As is 0.005 to 0.25 mass percent.

27. The high strength copper alloy according to any one of Claims 1 through 26, wherein said copper alloy is recrystallized material obtained from recrystallization of plastic working blank, which is formed by plastic working including cold working with working rate being more than 30 percent.

28. The high strength copper alloy according to Claim 27, wherein said recrystallized materials are obtained by heat-treatment of said plastic working blank at the range from 450 to 750 °C for 1 to 1000 seconds.

29. The high strength copper alloy according to Claim 27, wherein said cold working materials are obtained by cold rolling works or cold wire drawing of said recrystallized materials.

30. The high strength copper alloy according to Claim 29, wherein said copper alloy is obtained by heat-treatment of said cold working materials at the range from 150 to 600 °C for 1 second to 4 hours.

31. The high strength copper alloy according to Claim 29, wherein said copper alloys are manufactured pieces obtained by working said cold working materials to a predetermined form.

32. The high strength copper alloy according to Claim 31, wherein said copper alloy is obtained by heat-treatment of said cold working materials at the range from 150 to 600 °C for 1 second to 4 hours.

33. The high strength copper alloy according to any one of Claims 1 through 17, wherein said copper alloy is rolled material or manufactured piece with a predetermined form obtained by working said rolled material.

34. The high strength copper alloy according to any one of Claims 18 through 26, wherein said copper alloys are wire drawing material or manufactured pieces with a predetermined form obtained by working said wire drawing material.