JP5107093B2 - Copper alloy with high strength and high conductivity - Google Patents

Description

  The present invention relates to a copper alloy having high strength and high conductivity used as a material for electrical / electronic parts such as connectors, relays, switches, and sockets.

  With the recent development of electronics, the electrical wiring of various mechanical devices has become complicated and highly integrated, and electrical and electronic parts such as connectors have been reduced in size, weight, and reliability. Under such circumstances, since the copper alloy material for connectors is thinned and processed into a complicated shape, it is required to have good strength, elasticity, electrical conductivity, bending workability, and press formability. In particular, as the size and thickness are reduced, the cross-sectional area of the material subjected to the same load is reduced, and the cross-sectional area of the material with respect to the amount of current is also reduced. Therefore, both high strength and high electrical conductivity are required. In addition to the electronic parts that are becoming thinner, the electrical conductivity is an important characteristic in parts that conduct a large current such as bus bars for automobiles.

  Among conductive copper alloys, Cu-Ni-Sn-P-based alloys can be improved in strength and conductivity at the same time by precipitating Ni-P-based compounds by aging treatment under appropriate conditions. This alloy system has excellent balance of proof stress, electrical conductivity and bending workability, and also has excellent stress relaxation properties, and is used for various applications including small terminals and bus bars for automobiles. It has been.

  As such an alloy, for example, in Patent Documents 1 and 2 listed below, in order to enhance properties such as strength and conductivity as much as possible, cold rolling-heat treatment is repeated, and in some cases, solution treatment and subsequent high processing are performed. A Cu—Ni—Sn—P based copper alloy is shown in which a Ni—P based compound is uniformly and finely precipitated by cold rolling at a rate and heat treatment.

  Patent Document 3 below discloses a Cu—Ni—Sn—P-based copper alloy that achieves high strength by strictly controlling the precipitate size, the distance between precipitates, and the number of precipitates. .

Furthermore, in the following Patent Documents 4, 5, and 6, the strength of the Cu—Ni—Sn—P alloy is increased by adding Fe, Cr, Co, Mn, Mg, etc., which are liable to form a phosphorus compound, as an accessory component. A copper alloy with improved other properties is shown.
JP 2001-262255 A JP 2001-262297 A JP 2006-291356 A JP 2000-119779 A JP 2007-31795 A Japanese Patent Laid-Open No. 4-31544

However, in recent years, the demand for thinner and smaller current-carrying parts has become more severe, and further enhancement of strength is required. Although the strength and electrical conductivity have been improved by the above-described conventional technique that actively uses Ni-P-based precipitates, the size of the precipitates is several nanometers to several tens of nanometers, and the number density is 500 to 5000. It has reached about 1 / μm ² and it is difficult to make further improvements.
In view of such a problem, an object of the present invention is to provide a copper alloy having higher strength and higher conductivity than conventional materials.

  Under the idea that the present inventor should improve the precipitation strengthening amount per unit precipitation amount of the phosphorus compound forming the precipitate, in order to improve the material strength without reducing the conductivity, As a result of various studies on means for improving the precipitation strengthening amount of the phosphorus compound, it has been found that by controlling the composition of the phosphorus compound and increasing the matching strain around the precipitate, it has both high strength and conductivity. The present invention has been completed based on such knowledge.

That is, the copper alloy of the present invention has a chemical composition of mass% (hereinafter, simply referred to as “%”),
Ni: 0.010 to 3.0%,
P: 0.010-0.3%
Sn: 0.010 to 3.0%,
One or more of Co, Cr, Ti, Mn, Zr, Fe, Mg: 0.010% to 1.5% in total
Each of which contains a balance Cu and inevitable impurities, and has a structure in which precipitates of phosphorus compounds are dispersed, and Co with respect to the atomic weight N (Ni) of Ni contained in the phosphorus compounds forming the precipitates , Cr, Ti, Mn, Zr, Fe, and Mg, the ratio N / N (Ni) of the total N (M) of the atomic weight of each element is
0.05 ≦ N (M) / N (Ni) ≦ 30
It is said that.

In addition, the above basic components include Group A (Zn: 1.0% or less, Si: 0.1% or less), Group B (Ca, Ag, Cd, Be, Au, Pt, one or more of: By adding one or more elements from 1.0% or less in total), the following chemical compositions (1) and (2) can be obtained. Furthermore, for these chemical compositions, the impurity elements Hf, Th, Li, Na, K, Sr, Pd, W, S, C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As, Sb, Bi, Te, B, and misch metal are preferably limited to 0.1% or less in terms of the total amount of each element.
(1) Basic component + 1 or more from group A
(2) Basic component or component (1) above + one or more from group B

  According to the present invention, a copper alloy material having good conductivity after achieving a yield strength of over 500 Mpa, for example, a copper alloy of a class with a yield strength of over 500 Mpa, having a conductivity of 50% IACS or more and a yield strength of 550 MPa or more. It is possible to provide a copper alloy material having a high strength and high conductivity of 45% IACS or higher at the same time in a class of copper alloys. For this reason, the copper alloy according to the present invention can be suitably used as a material such as a material for electric / electronic parts that is becoming smaller and thinner and a bus bar material that requires strength and conductivity.

In the copper alloy according to the embodiment of the present invention, a precipitate composed of a phosphorus compound is finely dispersed in a matrix, and the phosphorus compound forming the precipitate has compositional characteristics. Will be described in detail. In the chemical composition range of the copper alloy described later, the size of the precipitate is about several nm to 50 nm, and the number density is about 500 to 5000 / μm ² .

  The phosphorus compound (Ni-MP) is composed of Co, Cr, Ti, Mn, Zr, Fe and Mg (hereinafter referred to as “M” with respect to the atomic weight N (Ni) of Ni contained therein). The ratio N (M) / N (Ni) of the total N (M) of the atomic weights of the respective elements of 0.05) is 0.05 or more so as to increase the precipitation strengthening amount per unit precipitation amount of the phosphorus compound. , Limited to 30 or less.

  The larger the N (M) / N (Ni) ratio in the phosphorus compound, the greater the difference in lattice constant between the precipitate and the parent phase Cu, and the greater the matching strain around the precipitate. This matched strain around the precipitate serves to hinder the dislocation movement and strengthen the material. Therefore, the larger the N (M) / N (Ni) ratio in the Ni-MP-based precipitate, the greater the alignment strain around the precipitate and the greater the precipitation strengthening amount per unit precipitation amount. However, if the N (M) / N (Ni) ratio is too small as less than 0.05, the lattice constant is almost the same as that of the Ni—P compound, and therefore a greater strength improvement effect than conventional cannot be expected. On the other hand, if the N (M) / N (Ni) ratio exceeds 30 and the difference between the lattice constants of the precipitate and the matrix becomes too large, the precipitate loses its consistency and a long-range matching strain. The field disappears and no significant precipitation strengthening can be expected. For this reason, the lower limit of the N (M) / N (Ni) ratio in the precipitated phosphorus compound is limited to 0.05 and the upper limit to 30. Preferably, the lower limit is 0.5 and the upper limit is 20. More preferably, the lower limit is 2 and the upper limit is 15.

Next, the chemical composition of the copper alloy according to the embodiment will be described.
Ni: 0.010 to 3.0%
Ni is an element necessary for generating a Ni—P compound with P to improve strength and stress relaxation resistance. If the content is less than 0.010%, the amount of precipitated phosphorus compound or the absolute amount of Ni solid solution is insufficient even when the production is performed under optimum conditions. Further, the smaller the amount of added Ni, the larger the N (M) / N (Ni) ratio in the precipitated phosphorus compound. When the Ni content is less than 0.010%, the N (M) / N (Ni) ratio is 0.00. The contribution to the strength of the precipitate is small. For this reason, the lower limit of the Ni amount is 0.010%. On the other hand, if the content exceeds 3.0%, coarse oxides, crystallized substances, precipitates, and the like are generated, and strength, stress relaxation resistance, and bending workability deteriorate. On the other hand, if it exceeds 3.0%, the N (M) / N (Ni) ratio in the precipitated phosphorus compound exceeds 30 and the contribution to the strength of the precipitate is reduced. For this reason, the upper limit of Ni amount is set to 3.0%. Preferably, it is 0.1 to 2.0% of range.

P: 0.010 to 0.3%
P is an element necessary for precipitating a phosphorus compound between Ni, Co, Cr, Ti, Mn, Zr, Fe, and Mg and improving strength and stress relaxation resistance. If the content is less than 0.010%, the phosphorus compound precipitation amount is insufficient, so the upper limit of the P content is 0.010%. On the other hand, if the content exceeds 0.3%, the phosphorus compound precipitated particles become coarse, and not only the strength and stress relaxation resistance, but also the hot workability deteriorates. For this reason, the lower limit of the amount of P is set to 0.3%. Preferably, it is 0.05 to 0.2% of range.

Sn: 0.010 to 3.0%
Sn is dissolved in the copper alloy to improve the strength. If the Sn content is small, it is necessary to increase the strength by increasing the rolling reduction of the final cold rolling after annealing. In this case, there is a slight decrease in conductivity and stress relaxation resistance. If the Sn content is less than 0.010%, Sn is too little, and even if the rolling reduction of the final cold rolling after annealing is increased, the strength is too low, and the balance of these properties does not reach the desired level. On the other hand, if it is added excessively, the electrical conductivity is lowered and the hot workability is also lowered. For this reason, the lower limit of the Sn content is 0.010%, and the upper limit is 3.0%. Preferably it is 0.1 to 2.0% of range.

One or more of Co, Cr, Ti, Mn, Zr, Fe, Mg: 0.010% to 1.5% in total
These elements are an MP compound between P and M (as described above, M represents one or more of Co, Cr, Ti, Mn, Zr, Fe, and Mg) or Ni. It is an element necessary for producing a Ni-MP compound containing N and improving strength and stress relaxation resistance. In addition, the MP and Ni-MP compounds have a larger difference in lattice constant from the Cu matrix than the Ni-P compounds, and increase the strain around the precipitates, so the precipitation strengthening amount must be increased. Is possible. Similar to Ni, if these elements are contained in a total amount of less than 0.010%, the absolute amount of precipitated phosphorus compounds is insufficient. Further, the smaller the amount of these elements added, the smaller the N (M) / N (Ni) ratio in the precipitated phosphorus compound. If the content is less than 0.010%, the N (M) / N (Ni) ratio is less than 0.05, and the contribution to the strength of the precipitate is small. For this reason, the minimum of the total amount of these elements is made into 0.010%. On the other hand, if the total amount exceeds 1.5%, excessive oxides, crystallized substances, precipitates, etc. are formed, and the strength, stress relaxation resistance and bending workability are lowered, and the solid solution. As a result, the conductivity decreases. Moreover, when it adds excessively, N (M) / N (Ni) ratio in a phosphorus compound will exceed 30, and the contribution to the intensity | strength of a precipitate will become small. Therefore, the upper limit of the total amount of these elements is 1.5%. Preferably, it is 0.05 to 0.8%, more preferably 0.05 to 0.3%.

In order to further improve the mechanical properties of the copper alloy with respect to the basic component, the basic component includes the group A (Zn: 1.0% or less, Si: 0.1% or less), the group B (Ca, Ag). , Cd, Be, Au, or Pt, one or more of them: 1.0% or less in total) to which one or more elements are added, and the chemical composition of the following (1) or (2) can do. Further, impurity elements Hf, Th, Li, Na, K, Sr, Pd, W, S, C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As, Sb, Bi, Te, B, and misch metal are preferably limited to a total amount of each element of 0.1% or less.
(1) Basic component + 1 or more from group A
(2) Basic component or component (1) above + one or more from group B

Zn: 1.0% or less, Si: 0.1% or less Zn prevents peeling of tin plating. However, if it is added excessively, the conductivity is lowered, and the susceptibility to stress corrosion cracking is increased. Si has an effect as a deoxidizer. However, if it is added in a large amount, the conductivity will decrease. Therefore, the Zn content is limited to 1% or less, and the Si content is limited to 0.1% or less.

One or more elements of group B: 1.0% or less in total Each element of group B has the effect of preventing the coarsening of crystal grains. Will fall. For this reason, these elements are made into 1.0% or less in total.

Hf, Th, Li, Na, K, Sr, Pd, W, S, C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As, Sb, Bi, Te, B, Misch Metal These elements are not more than 0.1 in total. These elements are impurity elements and are preferably as small as possible. However, in the component system of the embodiment, as long as these elements remain at 0.1% or less in total, the mechanical properties are improved. Does not affect much. Therefore, these elements are allowed to be 0.1% or less in total amount. Note that, by controlling the amounts of these elements contained in the raw material, the total amount of these impurity elements can be controlled to 0.1% or less under a conventional manufacturing method. When using ordinary copper alloy raw materials, these elements are rarely included, but when the raw material contains a large amount of these elements, for example when recycled products are used, handle with care. It is important to adjust the components so that the total amount is 0.1% or less.

  Next, the manufacturing method of the copper alloy plate which concerns on embodiment is demonstrated below. The copper alloy plate according to the embodiment is prepared by melting and casting a copper alloy having an adjusted component composition, homogenizing the ingot (soaking treatment), performing hot rolling and cold rough rolling, and further solution annealing. It is manufactured by performing a final finish cold rolling. Moreover, after performing solution annealing as needed, an aging treatment can be performed. The final finish rolling after solution annealing or further after aging treatment may be a reduction rate of 50% or less according to a conventional method from the viewpoint of strength and bending workability.

  The melting, casting, subsequent soaking, and hot rolling can be performed by ordinary methods. For hot rolling, the entry temperature is about 600 ° C. to 1000 ° C., and the end temperature is about 600 ° C. to 850 ° C. After hot rolling, it is cooled with water or allowed to cool, and then cold rough rolling is performed.

  The solution annealing performed after the cold rough rolling is held at 700 ° C. to 900 ° C. for 30 seconds, and the subsequent cooling rate is set to 1 ° C./sec or more in the temperature range up to 650 ° C., and 650 ° C. to 300 ° C. In the temperature range of 0.1 to 1.0 ° C./sec, cooling is performed at a cooling rate of 100 ° C./sec or more in the temperature range from 300 ° C. to room temperature.

The reason why the cooling rate after the solution annealing is set to the above range is to precipitate the phosphorus compound during cooling. At this time, the generation temperature range of the MP compound is higher than the generation temperature range of the Ni-P compound. For this reason, the N (M) / N (Ni) ratio in the Ni-MP compound increases as the generation temperature of the precipitate increases.
If the cooling rate is lower than 1 ° C./sec in the temperature range up to 650 ° C., the time during which the copper alloy is held in the high temperature region of 650 ° C. or more where the MP compound is easily formed becomes longer. As a result, the proportion of the MP compound that progresses in the high temperature range increases, and the N (M) / N (Ni) ratio of the Ni-MP precipitate becomes larger than 30. For this reason, a cooling rate shall be 1 degree-C / sec or more in the temperature range to 650 degreeC.
When the cooling rate is lower than 100 ° C./sec in the temperature range from 300 ° C. to room temperature, the time that is maintained in the temperature range of about 300 to 250 ° C. at which only the Ni—P compound is easily generated becomes longer. As a result, the proportion of Ni—P compounds that progress in the low temperature region increases, and the N (M) / N (Ni) ratio in the Ni—MP precipitates becomes smaller than 0.05. For this reason, a cooling rate shall be 100 degrees C / sec or more in the temperature range from 300 degreeC to room temperature.
In addition, in the temperature range of 650 ° C. to 300 ° C., 0.1 to 1.0 ° C./sec balances the generation of the MP compound and the Ni—P compound, and N (M) / N (Ni) This is because a Ni-MP precipitate having a ratio of 0.05 to 30 is generated.

  By the way, in the manufacture of the conventional copper alloy, regarding the solution annealing conditions, the temperature conditions for performing the solution forming are examined, but the subsequent cooling is hardly considered. Therefore, even if it is simply allowed to cool or is considered, as described in the examples of Patent Document 4, it is only about the degree of water cooling (rapid cooling) from the solution annealing temperature, and the cooling rate is It was not precisely controlled in that temperature range. Incidentally, even if the solution annealing temperature is 700 ° C. to 900 ° C. as described above, the cooling rate is lower than 100 ° C./sec at least in the temperature range from 300 ° C. to room temperature if it is allowed to cool. Therefore, the N (M) / N (Ni) ratio in the Ni-MP precipitate cannot be controlled. In addition, when rapidly cooled from the solution annealing temperature, the cooling rate in the temperature range of 650 ° C. to 300 ° C. becomes too fast, and the N (M) / N (Ni) ratio in the Ni—MP precipitates cannot be controlled.

  After solution annealing, an aging treatment can be performed to improve the strength-conductivity balance. At this time, attention should be paid to the aging temperature and time. That is, the aging treatment is performed at a temperature of 300 ° C. to 650 ° C. for 2 to 10 hours, and after aging, water cooling or standing cooling is performed. When aging is performed at a temperature of 650 ° C. or higher, as described above, only the formation of the MP compound proceeds significantly, and as a result, the N (M) / N (Ni) ratio becomes larger than 30. In addition, the aging does not progress at a temperature of 300 ° C. or lower in the range of 300 ° C. or lower, and only the formation of the Ni—P compound proceeds remarkably in the range of 300 to 250 ° C. The ratio is less than 0.05. By aging in the range of 300 to 650 ° C., the formation of MP compound and Ni—P compound proceeds in a balanced manner as in the case of cooling of the solution treatment, and the N (M) / N (Ni) ratio is desired. Can be controlled within the range. Further, the time required for the aging treatment may be 2 to 10 hours adopted in the normal aging treatment. If it is too short, the aging will not proceed and the conductivity will be low. On the other hand, if the aging time exceeds 10 hours, the strength will decrease.

  The copper alloy of the embodiment subjected to such an aging treatment has a proof stress of more than 500 Mpa and a conductivity of 55% IACS or higher, a proof strength of 550 MPa or higher, a conductivity of 50% IACS or higher, and a proof stress of 600 MPa. In the above class, a copper alloy having an extremely excellent high strength and high conductivity of 45% IACS or more is obtained.

The size of precipitates in the copper alloy manufactured by the above manufacturing method is about several nm to 50 nm, the number density is about 500 to 5000 / μm ² , and the size and number density of the precipitates are the same as those of conventional copper alloys. There is no big difference.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limitedly interpreted by this Example.

  Examples of the present invention will be described below. Copper alloy thin plates made of various Cu-Ni-Sn-P alloys were produced so that the chemical composition and the composition of precipitates in the structure were different, and the strength and conductivity characteristics were evaluated. The specific manufacturing process and evaluation method are as follows.

  The copper alloy was melted under a charcoal coating in the atmosphere in a kryptor furnace and cast to obtain a 150 mm thick ingot having the chemical composition shown in Table 1. Subsequently, after soaking at 965 ° C. for 3 hours, it was hot-rolled to a thickness of 15 mm, quenched with water at 750 ° C. or higher. Thereafter, both sides were chamfered by 1 mm to a thickness of 13 mm, and then cold rough rolling was performed to a thickness of 0.8 mm.

  This copper alloy plate was solution annealed by holding for 30 seconds at a temperature shown in Table 2 in a glass furnace, then cooled to room temperature under various cooling conditions shown in the same table, except for some, the same table An aging treatment was performed under the conditions shown in FIG. After aging treatment and water cooling, final finish rolling with a reduction rate of 50% was performed to produce a copper alloy sheet.

  A structure observation piece was taken from the obtained copper alloy thin plate of each sample, and the N (M) / N (Ni) ratio in the precipitate was determined in the following manner. Observation using a TEM (transmission electron microscope) at a magnification of 100000 times, randomly selecting three precipitates from the observed precipitates, and using EDX (energy dispersive X-ray analyzer) The characteristic X-rays of the constituent elements were detected, and the atomic weight of each element was measured. The N (M) / N (Ni) ratio obtained based on the atomic weight thus measured is also shown in Table 2. In any sample, the size and number density of precipitates were observed by TEM, and as a result, it was confirmed that they were at the same level as conventional copper alloys.

  The mechanical properties of each copper alloy thin plate were measured as follows. A JIS No. 5 tensile test piece was produced by machining so that the longitudinal direction of the test piece was perpendicular to the rolling direction of the plate material from the copper alloy thin plate of each sample. Then, mechanical characteristics were measured with a 5882 type Instron universal testing machine under the conditions of room temperature, a test speed of 10.0 mm / min, and GL = 50 mm. The measurement results are also shown in Table 2. In Table 2, in addition to the yield strength of each sample, hardness and tensile strength are also shown for reference.

  Moreover, the electrical conductivity of each said copper alloy thin plate was measured in the following ways. A strip-shaped test piece of width 10mm x length 300mm is processed from the copper alloy thin plate of each sample by milling, and in accordance with the nonferrous metal material conductivity measurement method stipulated in JIS-H0505, double bridge resistance measurement The electrical resistance was measured with an apparatus, and the conductivity was calculated by the average cross-sectional area method. The measurement results are also shown in Table 2.

  From Table 2, since sample Nos. 1 to 18 (Examples), which are examples of the present invention, have appropriate chemical compositions and production conditions, the N (M) / N (Ni) ratio in the precipitated phosphorus compound Is controlled in the range of 0.05 to 30, and as a result, it achieves high strength exceeding 500 MPa in proof stress and also has excellent conductivity. However, sample Nos. 3, 6, 11, and 18 in which the ratio of N (M) / N (Ni) in the precipitated phosphorus compound is relatively large and samples No. 4, 5, and 10 in which the ratio is relatively small have the same ratio of 2. As compared with Sample Nos. 1, 2, 7 to 9, 12 to 17 in a more preferable range of ˜15, the proof stress or the conductivity is slightly lowered. Moreover, compared with sample Nos. 1 and 12 that were subjected to aging treatment even in the same component system, the strength and conductivity were somewhat lowered in Nos. 2 and 13 that were not subjected to aging treatment. Moreover, although sample No. 7-9 is an appropriate component, since P or Sn exists in the vicinity of the boundary of a regulation range, yield strength or electrical conductivity has fallen a little.

  On the other hand, although Sample Nos. 21 to 26 which are comparative examples are alloy compositions in the composition of the present invention, Nos. 21 to 24 have an inappropriate cooling rate after solution treatment. Since the aging temperature is inappropriate, the N (M) / N (Ni) ratio of the phosphorus compound to be precipitated is less than 0.05 or more than 30, and the proof stress or conductivity is reduced as compared with the examples. . Samples Nos. 27, 28, 33, and 34 of the comparative examples are manufactured because the amount of Ni or M (Co, Cr, Ti, Mn, Zr, Fe, Mg) is out of the scope of the present invention. Although the conditions are appropriate, the N (M) / N (Ni) ratio in the precipitated phosphorus compound is less than 0.05 or more than 30, and the proof stress or conductivity is reduced. In Nos. 29 to 32, the ratio of N (M) / N (Ni) in the precipitated phosphorus compound satisfies the range of 0.05 to 30, but the addition amount of P or Sn is outside the range of the present invention. For this reason, the proof stress or conductivity is reduced.

Claims (4)

Chemical composition is mass%,
Ni: 0.010 to 3.0%,
P: 0.010-0.3%
Sn: 0.010 to 3.0%,
One or more of Co, Cr, Ti, Mn, Zr, Fe, Mg: 0.01% to 1.5% in total
Each of which contains a balance Cu and inevitable impurities, and has a structure in which precipitates made of a phosphorus compound are dispersed,
The ratio N (M) of the total atomic weight N (M) of each element of Co, Cr, Ti, Mn, Zr, Fe and Mg to the atomic weight N (Ni) of Ni contained in the phosphorus compound forming the precipitate ) / N (Ni)
0.05 ≦ N (M) / N (Ni) ≦ 30
A copper alloy with high strength and high electrical conductivity.   The copper alloy according to claim 1, wherein the chemical composition further includes, in mass%, Zn: 1.0% or less and Si: 0.1% or less.   The copper alloy according to claim 1 or 2, wherein the chemical composition further comprises 1% or more of Ca, Ag, Cd, Be, Au, and Pt: 1.0% or less in total in terms of mass%.   Hf, Th, Li, Na, K, Sr, Pd, W, S, C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As, Sb, Bi, Te, in the chemical composition The copper alloy according to any one of claims 1 to 3, wherein a total amount of each element of B and Misch metal is limited to 0.1% or less by mass%.