KR101777987B1 - Copper alloy sheet and process producing copper alloy sheet - Google Patents

Abstract

Provided is a copper alloy plate excellent in stress corrosion cracking resistance, stress relaxation property, tensile strength, proof stress, conductivity, bending workability, and solder wettability.
The copper alloy sheet contains 4 to 14 mass% of Zn, 0.1 to 1 mass% of Sn, 0.005 to 0.08 mass% of P, and 1.0 to 2.4 mass% of Ni, the balance being Cu and inevitable impurities [Sn] -1.8 x [Ni]? 11, 0.3? (3 x [Sn] + 3 x [Sn] + 2 x [Ni]? 18, 0? Ni] / [Sn]? 10 and 16? [Ni] / [P]? 250, A ratio of the number of precipitates having a grain size of 3 to 75 nm is 70% or more, a conductivity is 24% IACS or more, and a stress relaxation property The stress relaxation rate at 25O < 0 > C and 1000 hours is 25% or less.

Description

TECHNICAL FIELD [0001] The present invention relates to a copper alloy sheet and a copper alloy sheet,

INDUSTRIAL APPLICABILITY The present invention relates to a copper alloy plate excellent in stress corrosion cracking resistance, stress relaxation property, tensile strength, proof stress, conductivity, bending workability and solder wettability, A copper alloy plate, and a method for producing the copper alloy plate.

The present application claims priority based on Japanese Patent Application No. 2014-196430 filed on September 26, 2014, and its contents are hereby incorporated herein by reference.

BACKGROUND ART Conventionally, copper alloy sheets having high strength and high strength have been used as constituent materials for connectors, terminals, relays, springs, switches, semiconductors, and lead frames used for automobile parts, electric parts, electronic parts, communication devices, electronic and electronic devices . However, in recent years, with the miniaturization, light weight, and high performance of such devices, there has been a demand for very strict characteristics improvement in the constituent materials used therefor. For example, in the spring contact portion of a connector, an ultrathin plate is used. In order to attain thinning, a high strength copper alloy constituting such an ultrathin plate is required to have high strength, high elongation and strength Is required. In addition, it is demanded that there is no problem in productivity and economical efficiency and in corrosion resistance (resistance to stress corrosion cracking, internal zinc corrosion, internal migration), stress relaxation property, solder wettability and the like which inhibit deterioration of conductivity and materials in use.

However, the strength and the electric conductivity are opposite characteristics, and when the strength is improved, the electric conductivity generally decreases. Further, for example, there is a case where the temperature is elevated to, for example, 100 deg. C to 150 deg. C in a high use environment temperature close to the engine room of an automobile, and there is a part that requires better stress relaxation characteristics and heat resistance. In addition, with the recent evolution of automobile engine electronic control technology, there is a demand for a copper alloy material which can be used under high temperature and which can secure high reliability under a high temperature environment. Of course, automobile parts and electric / electronic parts are exposed to serious competition, and copper alloy materials of low cost are required. From the viewpoint of global procurement, a copper alloy material which is easy to manufacture has been desired.

As the high-strength, high-strength copper alloy, beryllium copper, phosphor bronze, nickel silver, brass, or brass with Sn added thereto are predominant.

A Cu-Zn-Sn alloy as disclosed in, for example, Patent Document 1 is known as an alloy for meeting a demand for high conductivity and high strength.

Patent Document 1: JP-A-2007-056365

However, the above-mentioned general high-strength copper alloys such as beryllium copper, phosphor bronze, nickel silver, and brass have the following problems and can not meet the above-mentioned demands.

Beryllium copper has the highest strength among the copper alloys, but beryllium is very harmful to the human body (especially in the molten state, very low amounts of beryllium vapor are very dangerous). As a result, it is difficult to dispose the beryllium copper member or the product containing the beryllium copper member (especially, the incineration treatment), and the initial cost required for the melting equipment used in the production becomes very high. Therefore, in order to obtain predetermined characteristics, a solution treatment is required in the final stage of manufacturing, and there is a problem in economy including manufacturing cost.

Phosphor bronze and nickel silver are generally manufactured by horizontal continuous casting because of poor hot workability and difficulty in production by hot rolling. Therefore, the productivity is poor, the energy cost is high, and the yield is poor.

In addition, phosphor bronze for springs and nickel silver for spring, which are representative varieties of high-strength copper alloy, contain a large amount of high-priced Sn and Ni, resulting in poor conductivity and low cost.

Zn, which is a main element of brass, is inexpensive compared with Cu. When Zn is added to Cu, the density becomes smaller and the strength, that is, tensile strength, proof stress or yield stress, spring limit value, and fatigue strength are increased. However, in brass, as the Zn content is increased, the stress corrosion cracking susceptibility becomes very high and the reliability as a material is impaired. On the other hand, in brass, the stress relaxation property is poor as well known, and it can not be used for parts that reach high temperatures such as around the engine room. As the Zn content increases, the strength is improved, but the ductility and the bending workability are deteriorated, and the balance between strength and ductility is deteriorated.

As described above, brass and simply brass added with Sn are inexpensive, but they are not satisfactory in strength, have poor stress relaxation properties, poor in conductivity, have a problem in corrosion resistance (stress corrosion and dezinc corrosion) It is not suitable as a component material for achieving miniaturization and high performance.

Therefore, such a general high-strength / high-strength copper alloy can not be satisfactorily satisfied as a component component of various devices tending to be miniaturized, lightweight and high-performance as described above, and the development of new high- Is being requested.

Also, the Cu-Zn-Sn alloy described in Patent Document 1 did not have sufficient properties including conductivity and strength.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art described above and has an object of providing a copper alloy plate excellent in stress corrosion cracking resistance, stress relaxation property, tensile strength, proof stress, conductivity, bending workability, and solder wettability, A copper alloy plate suitable for a highly reliable terminal / connector electric / electronic component that can withstand high temperatures, and a method for producing the copper alloy plate.

In order to solve the above problems, the inventors of the present invention have repeatedly studied from various angles and have made various researches and experiments. The present inventors have found that a Cu-Zn alloy containing 4 to 14 mass% of Zn is first added with a proper amount of Ni and Sn And in order to optimize the interaction between Ni and Sn, the ratio of the total content and content of Ni to Sn is set within a proper range, and in consideration of the interaction between Zn and Ni and Sn, Sn] -1.8 x Ni and f3 3 x [Ni] + 0.5 x [Sn] + [Ni] + 3 x [Sn] + 2 x [Ni] The amount of Sn and the amount of Sn, and the amount of P and the amount of Ni within the appropriate range, and the size of the precipitate to be formed and By appropriately adjusting the crystal grain size, the cost performance is excellent, the density is low, and the balance between high strength, elongation, bending workability and conductivity, resistance to stress corrosion cracking resistance, Good, and to find a copper alloy which can accommodate a variety of used environment, leading to achieve the present invention.

Concretely, a high strength is obtained without impairing ductility and bending workability by containing an appropriate amount of Zn, Ni and Sn in the matrix by solid solution. Then, by co-addition of Sn, divalent Zn, Ni, and pentavalent P, the valence (or valence electron number, the same applies hereinafter) Corrosion cracking property and stress relaxation property are improved, and at the same time, the stacking defect energy is lowered, and the crystal grain at the time of recrystallization is made finer. In addition, by forming a fine compound mainly composed of Ni and P, grain growth is suppressed and fine crystal grains are maintained.

Further, by making the crystal grains (recrystallized grains) finer, the strength mainly on the tensile strength and the proof stress can be remarkably improved. That is, as the average crystal grain size decreases, the strength also increases. Specifically, the addition of Zn, Sn and Ni to Cu has the effect of increasing the nucleation sites of recrystallization nuclei. The addition of P and Ni to the Cu-Zn-Sn-Ni alloy has the effect of inhibiting grain growth. Therefore, it is possible to obtain a Cu-Zn-Sn-Ni-P alloy having fine crystal grains by utilizing these effects. The increase of the nucleation site of the recrystallized nuclei is considered to be one of the main reasons for lowering the stacking defect energy by addition of Zn, Ni, and Sn, which have valencies of 2, 2 and 4, respectively. It is considered that the suppression of the crystal growth which keeps the generated fine recrystallized grains finely is caused by the formation of fine precipitates by the addition of P and Ni. However, the balance between strength, elongation, and bending workability can not be balanced only by aiming at refinement of recrystallized grains. In order to maintain the balance, it has been found that the grain size of the grain size within a predetermined range is good in order to allow for refinement of the recrystallized grains. Regarding miniaturization or ultrafine graining of crystal grains, the minimum crystal grain size in JIS H 0501 is 0.010 mm in the standard photographs described. From this, it is considered that having an average grain size of less than 0.010 mm can be said to be fine grain size.

In order to improve the strength and the stress relaxation property and the stress corrosion cracking resistance by improving the strength without hindering the ductility and the bending workability by melting each element of Zn, Ni and Sn in Cu, From various perspectives, including the nature of the element, it is necessary to consider the interactions between the elements. That is, simply by specifying the content of each element of Zn, Ni and Sn, it is possible to improve the stress relaxation characteristics and the stress corrosion cracking resistance, and to ensure high strength without deteriorating ductility and bending workability You can not get it.

Therefore, the compositional relationship f1? [Zn] + 3 占 [Sn] + 2 占 [Ni] and the compositional relationship f2? [Zn] -0.3 占 [Sn] -1.8 占 [Ni] Ni] + 0.5 x [Sn]) / [Zn] needs to be within a predetermined range.

The lower limit values of the compositional relations f1 and f2 are the minimum necessary values for obtaining high strength even when considering the interaction of the respective elements of Zn, Ni and Sn. On the other hand, when the compositional relations f1 and f2 exceed the upper limit value, When the lower limit of the relational expression f3 is exceeded, the strength is increased but the stress relaxation property or the stress corrosion cracking resistance is impaired.

The upper limit value of the compositional relationship f1? [Zn] + 3 占 [Sn] + 2 占 [Ni] is a value whether or not the conductivity of the alloy of the present invention exceeds 24% IACS.

The upper limit value of the compositional relationship f2? [Zn] -0.3 占 [Sn] -1.8 占 [Ni] is also a threshold value for obtaining excellent stress relaxation characteristics, stress corrosion cracking resistance, good ductility, bending workability and solder wettability. As described above, the fatal defect of the Cu-Zn alloy is that the susceptibility to stress corrosion cracking is high and the stress relaxation property is bad.

The lower limit of the compositional relationship f3? (3 x [Ni] + 0.5 x [Sn]) / [Zn] is a value of a boundary for obtaining good stress relaxation property. As described above, the Cu-Zn alloy is an alloy excellent in cost performance, but lacks stress relaxation characteristics, and even if it has high strength, high strength can not be utilized. Generally, a brass alloy lacks the stress relaxation property, but a higher stress relaxation characteristic can be realized by optimizing the balance (3 x [Ni] + 0.5 x [Sn]) and the balance of [Zn] . The upper limit value increases the amount of Ni and Sn, increases the cost or deteriorates the conductivity, and also the stress relaxation characteristic is saturated.

Further, in the present invention, it is important to set the content of Ni and Sn, the content of P and the content of Ni, and the appropriate content so that excellent stress relaxation characteristics, strength and bending workability can be realized. Particularly, in order to improve the stress relaxation of the Cu-Zn alloy, it is a first condition to co-add 1 to 2.4 mass% of Ni and 0.1 to 1 mass% of Sn, and the content ratio of Ni and Sn is important , The compositional relationship f4? [Ni] / [Sn] needs to be set within a predetermined range. In detail, at least 3.5 Ni atoms are required for one Sn atom, which will be described later. Ni and P, which are important for stress relaxation characteristics, grain size, strength and bending workability, can be calculated from the relationship between Ni and P to be solved and the compound of Ni and P to be precipitated. Should be within a predetermined range.

In the above-described copper alloy plate, it is preferable to perform the recovery heat treatment step and the heat treatment corresponding thereto after the finish cold rolling step. In this case, since the recovery heat treatment is performed, the stress relaxation rate, Young's modulus, spring limit value, and elongation are improved.

Examples of the method for producing the above-described copper alloy sheet include a process for producing an ingot mixed with a predetermined component, a hot rolling step, a continuous casting step in which a hot rolling step is omitted, a cold rolling step, a recrystallization heat treatment step, And a finish cold rolling step in this order, wherein the hot rolling starting temperature in the hot rolling step is 800 to 950 占 폚, the final rolling is finished at 750 to 500 占 폚, and then the air cooling or the forced cooling by water cooling And cooled to room temperature. The recrystallization heat treatment step includes a batch method of heating for a long time and a continuous heat treatment method of continuously heating at a high temperature for a short time. After the final finish rolling, a tension leveler may be performed to improve the deformation of the material. In addition, a recovery heat treatment may be carried out by a continuous heat treatment method, or, in the case of additionally used for terminal and connector electrical and electronic parts, a molten Sn plating, a reflow solder plating or the like The plating process may be performed.

Depending on the thickness of the copper alloy plate, the cold rolling step and the annealing step, which are paired between the hot rolling step and the cold rolling step, may be performed once or plural times.

In particular, the production method of a copper alloy plate used for a terminal or a connector is preferably such that the cold working rate in the cold rolling step is 55% or more, and the recrystallization heat treatment step is carried out by using a continuous heat treatment furnace, A heating step of heating the copper alloy material to a predetermined temperature; a holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step; and a cooling step of cooling the copper alloy material to a predetermined temperature after the holding step Wherein the copper alloy material is heated in a temperature range from a temperature which is 50 占 폚 lower than a maximum attainable temperature of the copper alloy material to a maximum attainable temperature by setting a maximum reaching temperature of the copper alloy material to Tmax (占 폚) in the recrystallization heat treatment step, when the holding time is a tm (min), 560≤Tmax≤790, 0.04≤tm≤1.0 , 520≤It1≤ is ^{(Tmax-30 × tm -1/2)} ≤690, and also, A heating step of heating the copper alloy material to a predetermined temperature after the batch cold rolling step; a holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step; and a holding step of holding the copper alloy material at a predetermined temperature Wherein the copper alloy material has a maximum reaching temperature Tmax2 (占 폚), and the copper alloy material is heated and maintained at a temperature range from a temperature 50 占 폚 lower than the maximum attainable temperature of the copper alloy material to a maximum attainable temperature (Tmax2-25 x tm2-l ^{/ 2} ) < ^/ = 390, or a Sn-plating process, wherein tm2 ≪ / RTI > The stress relaxation rate, Young's modulus, spring limit value, bending workability and elongation can be improved by carrying out a recrystallization heat treatment at a high temperature for a short time and a recovery heat treatment step.

The present invention has been accomplished based on the above discovery. The first aspect of the present invention is a copper alloy sheet comprising 4 to 14 mass% of Zn, 0.1 to 1 mass% of Sn, 0.005 to 0.08 mass% of P And Sn in an amount of 1.0 to 2.4 mass% and the balance of Cu and inevitable impurities, and the content of Zn [mass%], the content of Sn [Sn] and the content of P [P] % And the Ni content [Ni]% by mass,

7? [Zn] + 3 x [Sn] + 2 x [Ni]? 18,

0? [Zn] -0.3 x [Sn] -1.8 x [Ni]? 11,

0.3? (3 x [Ni] + 0.5 x [Sn]) / [Zn]? 1.6,

1.8? [Ni] / [Sn]? 10,

16? [Ni] / [P]? 250

And the average grain size of the precipitate having a mean grain size of 2 to 9 占 퐉 and the average grain size of the precipitate having a circular or elliptic shape is 3 to 75 nm or the ratio of the number of precipitates having a grain size of 3 to 75 nm among the precipitates is 70 %, A conductivity of 24% IACS or more, and a stress relaxation rate of 150% or less at a temperature of 150 DEG C as a stress relaxation property of 25% or less.

The copper alloy sheet according to the second aspect of the present invention contains 4 to 12 mass% of Zn, 0.1 to 0.9 mass% of Sn, 0.008 to 0.07 mass% of P, and 1.05 to 2.2 mass% of Ni, And the remainder is made of Cu and inevitable impurities, and the content of [Zn], the content of Sn [Sn], the content of P [P] and the content of Ni [Ni] on,

7? [Zn] + 3 x [Sn] + 2 x [Ni]? 16,

0? [Zn] -0.3 x [Sn] -1.8 x [Ni]? 9,

0.3? (3 x [Ni] + 0.5 x [Sn]) / [Zn]? 1.3,

2? [Ni] / [Sn]? 8,

18? [Ni] / [P]? 180

And the average grain size of the precipitate having a mean grain size of 2 to 9 탆 and the average grain size of the precipitate having a circular or elliptic shape is 3 to 60 nm or the ratio of the number of precipitates having a grain size of 3 to 60 nm among the precipitates is 70 %, An electric conductivity of 26% IACS or more, and a stress relaxation rate of not more than 23% at 1000 DEG C at 150 DEG C as a stress relaxation property.

The copper alloy plate according to the third aspect of the present invention is characterized in that the above-mentioned copper alloy plate further contains at least one element selected from Al, Fe, Co, Mg, Mn, Ti, Zr, Cr, Si, Sb, As, Pb and rare earth elements At least one kind or two or more kinds thereof, respectively, in an amount of not less than 0.0005 mass% and not more than 0.05 mass%, and further in a total amount of not less than 0.0005 mass% and not more than 0.2 mass%.

The copper alloy sheet according to the fourth aspect of the present invention is characterized in that in the above-described copper alloy sheet, the copper alloy material includes a finish cold rolling process in which the copper alloy material is subjected to cold rolling and a recovery heat treatment process in which after the finish cold- (% IACS), and the effective stress at 150 DEG C for 1000 hours is Pw (N / mm < ² >),

Pw? 300,

Pw 占 C / 100)? ^1/2? 190

Have a relationship of the ratio of the yield strength YS _{of 90} in a direction forming a 90 ° to the rolling direction, the yield strength YS ₀ for forming the zero degree direction to the rolling direction, YS ₉₀ / YS is _0, 0.95≤YS ₉₀ / YS ₀ Lt; = 1.07.

The copper alloy plate according to the fifth aspect of the present invention is characterized by being used in electronic and electronic device parts such as connectors, terminals, relays, switches, and semiconductors.

A sixth aspect of the present invention is a method for producing a copper alloy sheet for producing the above-described copper alloy sheet, which comprises a hot rolling step, a cold rolling step, a recrystallization heat treatment step, a finish cold rolling step And a cold working ratio in the cold rolling step is 55% or more. The recrystallization heat treatment step includes a heating step of heating the copper alloy material after cold rolling to a predetermined temperature by using a continuous heat treatment furnace, A holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step; and a cooling step of cooling the copper alloy material to a predetermined temperature after the holding step, wherein in the recrystallization heat treatment step, The maximum reaching temperature of the alloying material is set to Tmax (占 폚), and a temperature lower by 50 占 폚 than the maximum reaching temperature of the copper alloy material, In the temperature range of up to reach the temperature, when the heating and holding time to tm (min),

560? Tmax? 790,

0.04? Tm? 1.0,

(Tmax-30 x tm-1 ^/2 ) < ^/ = 690 in the recrystallization heat treatment step, And cooling under the above conditions. Further, depending on the thickness of the copper alloy plate, the cold rolling step and the annealing step which are paired between the hot rolling step and the cold rolling step may be performed once or plural times.

The method for producing a copper alloy sheet according to a seventh aspect of the present invention includes a recovery heat treatment step performed after the finish cold rolling step, wherein the recovery heat treatment step is a heating step for heating the copper alloy material after the finish cold- A holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step and a cooling step of cooling the copper alloy material to a predetermined temperature after the holding step, Of the copper alloy material is Tmax2 (占 폚), and the time of heating and holding at a temperature range from a temperature 50 占 폚 lower than the maximum attained temperature of the copper alloy material to a maximum attained temperature is tm2 (min)

150? Tmax2? 580,

0.02? Tm2? 100,

120? It2 = (Tmax2-25? Tm2? ^1/2 )? 390

. ≪ / RTI >

A method for producing a copper alloy sheet according to an eighth aspect of the present invention is a method for producing a copper alloy sheet for producing the above-mentioned copper alloy sheet, comprising a cold rolling step, an annealing step, a cold rolling step, a recrystallization heat treatment step, , A finish cold rolling process, and a recovery heat treatment process, wherein the cold rolling process and the annealing process are performed once or plural times without performing hot working, and then the combination of the cold rolling process and the recrystallization process, and , And the combination of the finishing cold rolling step and the recovery heat treatment step is performed, and the cold working ratio in the cold rolling step is 55% or more, and the recrystallization heat treatment step is a step of heating the continuous heat treatment furnace A heating step of heating the copper alloy material after the cold rolling to a predetermined temperature by using the copper alloy, And a cooling step of cooling the copper alloy material to a predetermined temperature after the holding step, wherein in the recrystallization heat treatment step, the maximum reaching temperature of the copper alloy material is Tmax (° C), and when the time of heating and holding is tm (min) at a temperature range from a temperature 50 ° C lower than the maximum attained temperature of the copper alloy material to a maximum attained temperature,

560? Tmax? 790,

0.04? Tm? 1.0,

(Tmax-30 x tm-1 ^/2 ) < ^/ = 690 in the recrystallization heat treatment step, Cool under the above conditions. Wherein the recovery heat treatment step comprises a heating step of heating the copper alloy material after the final cold rolling to a predetermined temperature, a holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step, And a cooling step of cooling the material to a predetermined temperature, wherein a maximum arrival temperature of the copper alloy material is Tmax2 (占 폚), and a temperature range from a temperature 50 占 폚 lower than the maximum reaching temperature of the copper alloy material to a maximum reaching temperature (Tm2 (min)),

150? Tmax2? 580,

0.02? Tm2? 100,

120? It2 = (Tmax2-25? Tm2? ^1/2 )? 390

. ≪ / RTI >

According to the present invention, it is possible to provide a copper alloy plate excellent in stress corrosion cracking resistance, stress relaxation property, tensile strength, proof strength, conductivity, bending workability and solder wettability, A copper alloy sheet suitable for electric and electronic parts, and a method for producing the copper alloy sheet can be provided.

Hereinafter, a method of manufacturing a copper alloy plate and a copper alloy plate according to an embodiment of the present invention will be described. The copper alloy plate of the present embodiment is used as a constituent material for connectors, terminals, relays, springs, switches, semiconductors, and lead frames used for automobile parts, electric parts, electronic parts, communication equipment,

Here, in this specification, an element symbol enclosed in parentheses, such as [Zn], represents the content (mass%) of the element.

In the present embodiment, a plurality of compositional relationship expressions are defined as follows using the display method of the content. In addition, the effective additive elements such as Co and Fe and inevitable impurities do not affect the characteristics of the copper alloy plate at the contents specified in the present embodiment, and are not included in the respective calculation equations to be described later. For example, Cr of less than 0.005 mass% is inevitable impurities.

The compositional relationship f1 = [Zn] + 3 x [Sn] + 2 x [Ni]

Composition relation f2 = [Zn] -0.3 x [Sn] -1.8 x [Ni]

Composition relation f3 = (3 x [Ni] + 0.5 x [Sn]) / [Zn]

The compositional relationship f4 = [Ni] / [Sn]

Composition relation f5 = [Ni] / [P]

The copper alloy sheet according to the first embodiment of the present invention comprises 4 to 14 mass% of Zn, 0.1 to 1 mass% of Sn, 0.005 to 0.08 mass% of P, and 1.0 to 2.4 mass% of Ni And the remainder is made of Cu and inevitable impurities, and the compositional relationship f1 is in the range of 7? F1? 18, the compositional relationship f2 is in the range of 0? F2 11, and the compositional relationship f3 is in the range of 0.3? F3? , The compositional relationship f4 is within the range of 1.8? F4? 10, and the compositional relationship f5 is within the range of 16? F5? 250.

The copper alloy sheet according to the second embodiment of the present invention contains 4 to 12 mass% of Zn, 0.1 to 0.9 mass% of Sn, 0.008 to 0.07 mass% of P, and 1.05 to 2.2 mass% of Ni And the remainder is made of Cu and inevitable impurities, and the compositional relationship f1 is in the range of 7? F1 16, the compositional relationship f2 is in the range of 0? F2 9, and the compositional relationship f3 is in the range of 0.3? F3? , The compositional relationship f4 is within a range of 2? F4? 8, and the compositional relationship f5 is within a range of 18? F5? 180.

The copper alloy sheet according to the third embodiment of the present invention comprises 4 to 14 mass% of Zn, 0.1 to 1 mass% of Sn, 0.005 to 0.08 mass% of P, 1.0 to 2.4 mass% of Ni, At least one or more selected from the group consisting of Al, Fe, Co, Mg, Mn, Ti, Zr, Cr, Si, Sb, As, Pb and rare earth elements respectively in an amount of from 0.0005 mass% to 0.05 mass% Wherein the compositional relationship f1 is in the range of 7? F1? 18, the compositional relationship f2 is in the range of 0? F2? 11, the compositional relationship f3 In the range of 0.3? F3? 1.6, the compositional relationship f4 is within the range of 1.8? F4? 10, and the compositional relationship f5 is within the range of 16? F5? 250.

A copper alloy sheet according to a fourth embodiment of the present invention comprises 4 to 12 mass% of Zn, 0.1 to 0.9 mass% of Sn, 0.008 to 0.07 mass% of P, 1.05 to 2.2 mass% of Ni and Al At least one kind selected from the group consisting of Fe, Co, Mg, Mn, Ti, Zr, Cr, Si, Sb, As, Pb and rare earth elements in an amount of not less than 0.0005 mass% and not more than 0.05 mass% % And not more than 0.2% by mass, the balance being Cu and inevitable impurities, wherein the compositional relationship f1 is in the range of 7? F1? 16, the compositional relationship f2 is in the range of 0? F2? 9, The compositional relationship f4 is within the range of 2? F4? 8, and the compositional relationship f5 is within the range of 18? F5? 180 within the range of 0.3? F3? 1.3.

In the above-described copper alloy sheets according to the first to fourth embodiments of the present invention, the average crystal grain size is 2 to 9 占 퐉.

In the copper alloy sheets according to the first and third embodiments of the present invention, the average particle diameter of the precipitate having a circular or elliptical shape is 3 to 75 nm, or the number of precipitates occupied by precipitates having a particle diameter of 3 to 75 nm Is 70% or more.

In the copper alloy sheets according to the second and fourth embodiments of the present invention, the average particle diameter of the precipitate having a circular or elliptical shape is 3 to 60 nm, or the ratio of the number of precipitates occupied by precipitates having a particle diameter of 3 to 60 nm Is 70% or more.

In the copper alloy sheets according to the first to fourth embodiments of the present invention described above, the conductivity is 24% IACS or more, or the electrical conductivity is 26% IACS or more. As the stress relaxation resistance, The stress relaxation rate is 25% or less, or the stress relaxation rate is 23% or less at 150 ° C for 1000 hours.

In the copper alloy sheets according to the first to fourth embodiments of the present invention, the balance index f6 is set as an index indicating the balance between the conductivity and the stress relaxation property as follows. When the effective stresses in the conductivity C (% IACS), 150 ℃ , 1000 ℃ to Pw (N / mm ^2), balance index f6 are defined as f6 = Pw × C / 100) 1/2. That is, the balance index f6 is a product of Pw and (C / 100) ^1/2 . In the present embodiment, it is preferable that Pw? 300 and f6? 190.

In the copper alloy sheets according to the first to fourth embodiments of the present invention, the ratio of the internal force YS _{90 in the} direction forming 90 degrees to the rolling direction and the internal force YS _{0 in} the direction making 0 degrees with respect to the rolling direction, It is preferable that YS ₉₀ / YS ₀ is in the range of 0.95? YS ₉₀ / YS ₀ ?

Hereinafter, the reason why the component composition, compositional relations f1, f2, f3, f4, f5, metal structure, and various characteristics are defined as described above will be described.

(Zn)

Zn is a main element constituting the copper alloy plate of the present embodiment, has a valence of 2, lowers the stacking defect energy, increases the sites of recrystallization nuclei generation at the time of annealing, and makes the recrystallized grains finer and finer. In addition, Zn solubility improves the tensile strength, the proof stress, the spring characteristic, and the like without impairing the bending workability, improves the heat resistance and the stress relaxation property of the matrix, and improves the solder wettability and migration resistance. Zn is inexpensive, lowers the specific gravity of copper alloy, and is economically advantageous. Sn and the like. However, in order to exhibit the above effect, Zn must be contained in an amount of at least 4% by mass or more. As a result, the lower limit of the content of Zn is 4 mass% or more, preferably 4.5 mass% or more, optimally 5 mass% or more. On the other hand, although depending on the relationship with other added elements such as Sn, remarkable effects suitable for the content are not obtained with respect to the refinement of crystal grains and the improvement in strength even when Zn is contained in an amount exceeding 14 mass% The susceptibility to stress corrosion cracking increases, the Young's modulus lowers, elongation and bending workability deteriorate, stress relaxation characteristics deteriorate, and solder wettability also deteriorates. As a result, the upper limit of the content of Zn is 14 mass%, preferably 12 mass% or less, 11 mass% or less, and most preferably 9 mass% or less. When Zn is in a suitable composition range, the heat resistance of the matrix is improved, the stress relaxation property is improved by the interaction of Ni, Sn and P, and excellent bending workability, high strength, Young's modulus and desired conductivity are provided.

Even if the content of Zn having divalent valence is within the above range, it is difficult to make crystal grains finer if only Zn is added. In order to make the crystal grains finer to a predetermined grain size, it is necessary to consider the value of the compositional relationship formula f1 together with co-addition with Sn, Ni, and P to be described later. Similarly, in order to improve heat resistance, stress relaxation characteristics, strength, and spring characteristics, it is necessary to consider the values of the compositional relational expressions f1, f2, and f3 together with the coexistence with Sn, Ni, and P described later.

When the Zn content is 9% by mass or more, a high tensile strength and proof stress can be obtained. As described above, the bending workability, the stress corrosion cracking resistance and the stress relaxation property are deteriorated and the Young's modulus is lowered as described above . In order to further improve these characteristics, the interaction of Ni or Sn and the values of the compositional relations f1, f2 and f3 become more important.

(Sn)

Sn is a major element constituting the copper alloy plate of the present embodiment and has a valence of 4 and lowers the stacking defect energy. In addition to the content of Zn and Ni, Sn increases the sites of recrystallization nuclei generation at annealing, The microfibers. Particularly, the co-addition of at least 4 mass% of bivalent Zn and divalent Ni remarkably exhibits the effect even when Sn is contained in a small amount. Further, Sn is dissolved in a matrix to improve tensile strength, proof stress, spring characteristic, etc., improve heat resistance of the matrix, improve stress relaxation property, and improve stress corrosion cracking resistance. In order to exhibit the above effect, Sn must be contained in an amount of at least 0.1 mass% or more. As a result, the lower limit of the content of Sn is 0.1 mass% or more, optimally 0.2 mass% or more. On the other hand, the incorporation of a large amount of Sn deteriorates the electrical conductivity, deteriorates the bending workability, the Young's modulus and the solder wettability, and deteriorates the stress relaxation property and the stress corrosion cracking resistance. In particular, the stress relaxation property is greatly influenced by the compounding ratio of Ni. As a result, the upper limit of the content of Sn is 1% by mass or less, preferably 0.9% by mass or less, and most preferably 0.8% by mass or less.

(Cu)

Cu is the main element constituting the copper alloy plate of the present embodiment, and therefore, Cu is the remainder. However, in order to ensure conductivity and stress corrosion cracking resistance depending on the Cu concentration, and to maintain stress relaxation characteristics, elongation, Young's modulus and solder wettability, the lower limit of the Cu content is 84% by mass or more, Or more. On the other hand, in order to obtain high strength, the upper limit of the content of Cu is preferably 94.5 mass% or less, and more preferably 94 mass% or less.

(P)

P has a valence of 5 and has an action to refine the crystal grains and an action to suppress the growth of the recrystallized grains, but the latter action is significant because the content is small. It has an effect of improving the stress relaxation property in the P dissolved in the matrix and the precipitate in combination with P and Ni although the amount is small. A part of P may be combined with Ni to be described later to form a precipitate, and depending on the case, Ni may be mainly combined with Co or Fe to form a precipitate, thereby further enhancing the effect of inhibiting grain growth. In order to suppress crystal grain growth, it is necessary to have a circular or elliptic precipitate, the average particle size of the precipitate is 3 to 75 nm, or the ratio of the number of precipitated particles having a particle size of 3 to 75 nm among the precipitated particles is 70% Do. This precipitate has a greater effect and effect than the precipitation strengthening for suppressing the growth of the recrystallized grains at the time of annealing, and is distinguished from the strengthening effect by simply precipitation. P has an effect of remarkably improving the stress relaxation characteristic, which is one of the subjects of the present application, by the interaction with Ni under the presence of Zn and Sn within the above-mentioned range.

In order to exhibit these effects, the lower limit of the content of P is 0.005 mass% or more, preferably 0.008 mass% or more, optimally 0.01 mass% or more. On the other hand, if the content exceeds 0.08% by mass, the effect of inhibiting the recrystallized grains growth by the precipitates is saturated, and if the precipitates are present in excess, the elongation, bending workability and stress relaxation characteristics are deteriorated. Therefore, the upper limit of the content of P is 0.08 mass%, preferably 0.07 mass% or less.

(Ni)

Ni combines with P to form a compound, and others are employed. Ni improves the stress relaxation characteristics and increases the Young's modulus of the alloy by the interaction of P, Zn, and Sn contained in the concentration range defined as described above to improve the solder wettability and stress corrosion cracking resistance, And the growth of the recrystallized grains is inhibited by the compound to be formed. In order to exert their action remarkably, it is necessary to contain 1% by mass or more. Therefore, the lower limit of the content of Ni is 1% by mass or more, preferably 1.05% by mass or more, and most preferably 1.1% by mass or more. On the other hand, since the increased amount of Ni hinders the conductivity and saturates the stress relaxation property, the upper limit of the content of Ni is 2.4 mass% or less, preferably 2.2 mass% or less, and most preferably 2 mass% or less. In order to improve the stress relaxation characteristics, the Young's modulus and the bending workability, it is preferable that the content of Ni is 1.8 times or more of the Sn content and more than 2 times . This is because the bivalent Ni in the atomic concentration contains not less than 3.5 times, particularly not less than 4 times, of the tetravalent Sn, whereby the stress relaxation property is particularly improved. On the other hand, it is preferable that the content of Ni is fixed to 10 times or less, more preferably 8 times or less, most preferably 6 times or less of the Sn content from the relationship between the strength and the conductivity and the stress relaxation property.

(At least one or more species selected from Al, Fe, Co, Mg, Mn, Ti, Zr, Cr, Si, Sb, As, Pb,

Elements such as Al, Fe, Co, Mg, Mn, Ti, Zr, Cr, Si, Sb, As, Pb and rare earth elements have an effect of improving various characteristics. Therefore, the copper alloy sheet of the third embodiment and the copper alloy sheet of the fourth embodiment contain at least one kind or two or more kinds selected from these elements.

Here, Al, Fe, Co, Mg, Mn, Ti, Zr, Cr, Si, Sb, As, Pb and rare earth elements make fine grains of the alloy. Al, Fe, Co, Mg, Mn, Ti, and Zr form a compound for both P and Ni, suppress the growth of recrystallized grains during annealing, and have a great effect of grain refinement. In particular, Fe and Co have a large effect and form a compound of Ni and P containing Fe or Co to make the particle size of the compound finer. The fine compounds improve the strength by further reducing the size of recrystallized grains during annealing. However, if the effect becomes excessive, the bending workability and the stress relaxation property are inhibited. Al, Sb, and As have an effect of improving the stress corrosion cracking resistance and corrosion resistance of the copper alloy. Sb having a valence of 5 improves the stress relaxation property and Pb has an effect of improving press formability .

In order to exhibit these effects, at least one or more elements selected from Al, Fe, Co, Mg, Mn, Ti, Zr, Cr, Si, Sb, As, Pb and rare- %. On the other hand, if any selected element exceeds 0.05 mass%, rather than saturating the effect, the bending workability is deteriorated. Particularly, when Fe, Co or the like, which easily forms a compound with P, exceeds 0.05% by mass, the stress relaxation property is deteriorated. Preferably, the selected element is 0.03 mass% or less. If the total content of these elements exceeds 0.2 mass%, the effect is not saturated, but rather the bending workability is deteriorated. Therefore, the upper limit of the total content of these elements is 0.2 mass% or less, preferably 0.15 mass% or less, and more preferably 0.1 mass% or less.

(Inevitable impurities)

Copper alloy plates contain inevitable elements such as oxygen, hydrogen, carbon, sulfur, water vapor, and the like, though they are in trace amounts in the raw material containing the return material and in the manufacturing process including mainly dissolution in the atmosphere. And inevitable impurities of these.

Here, in the copper alloy of the present embodiment, the elements other than the prescribed constituent elements may be treated as inevitable impurities, and the total content of the inevitable impurities is preferably 0.2 mass% or less, more preferably 0.1 % Or less. The elements other than Zn, Ni, Sn, P, and Cu among the elements specified in the copper alloy sheet of this embodiment may be contained in an amount lower than the lower limit defined above as an impurity.

(Compositional relation f1)

When the compositional relationship f1 = [Zn] + 3 x [Sn] + 2 x [Ni] is 7, this embodiment alloy is a boundary value at which high strength is obtained and is also a threshold value for improving stress relaxation characteristics. Therefore, the lower limit of the compositional relationship formula f1 is 7 or more, and preferably 7.5 or more. On the other hand, if the value of f1 exceeds 18, the desired conductivity is not obtained, and the stress relaxation property, the stress corrosion cracking resistance, the bending workability and the solder wettability are also badly affected. Therefore, the upper limit of the compositional relationship f1 is 18 or less, preferably 16 or less, optimally 14 or less.

(Compositional relationship f2)

Is a boundary value of whether or not cracks occur under a severe stress corrosion cracking environment when the compositional relationship f2 = [Zn] -0.3 x [Sn] -1.8 x [Ni] is 11 or 10. At the same time, it is also a threshold value for obtaining excellent ductility, bending workability, good solder wettability, and good stress relaxation characteristics. As described above, the fatal defect of the Cu-Zn alloy is that the susceptibility to stress corrosion cracking is high. In the case of the Cu-Zn alloy, the susceptibility of the stress corrosion crack depends on the content of Zn, The susceptibility to stress corrosion cracking becomes high with 10% by mass as a boundary. Therefore, the upper limit of the compositional relationship f2 is 11, preferably 9 or less, and optimally 8 or less. The compositional relationship f2 = 10 corresponds to a Zn content of 10% by mass or 9% by mass in the case of a Cu-Zn binary alloy. Within the composition range in which Ni and Sn of the present invention are co-added, in the compositional relationship formula f2, the coefficient of Ni is large and the stress corrosion cracking susceptibility can be reduced particularly by the inclusion of Ni. On the other hand, if f2 is less than 0, the strength is lowered. Therefore, the lower limit of the compositional relationship formula f2 is 0 or more, preferably 0.5 or more, and more preferably 1 or more.

(Compositional relation f3)

By appropriately setting the compositional relationship f3 = (3 x [Ni] + 0.5 x [Sn]) / [Zn], that is, 3 x [Ni] + 0.5 x [Sn] To 14% by mass, and exhibits excellent stress relaxation characteristics. When the value of f3 is 0.3 or more, that is, the value of (3 x [Ni] + 0.5 x [Sn]) is 0.3 or more with respect to [Zn], good stress relaxation characteristics are exhibited. Preferably at least 0.35, more preferably at least 0.4. At the same time, solder wettability and stress corrosion cracking resistance also become good. On the other hand, even if the value of f3 exceeds 1.6, rather than saturating the effect, the electric conductivity and the stress relaxation characteristics are deteriorated rather than Zn, which contains a large amount of expensive Sn and Ni. Therefore, the upper limit value of the compositional relationship formula f3 is 1.6 or less, preferably 1.3 or less, and optimally 1.2 or less.

(Composition relation formula f4)

In the Cu-Zn-Ni-Sn-P alloy, a compositional relationship f4 = [Ni] / [Sn] indicating the mixing ratio of Ni and Sn is important in order to improve stress relaxation characteristics. When Sn having a valence of 4 is 1.8 times in mass concentration ratio of Ni having a valence of 2 and 3.5 times or more in atom concentration ratio, the stress relaxation property is remarkably improved. When the value of f4 is 2 or more, that is, when there are four or more divalent Ni atoms per one tetravalent Sn atom, the stress relaxation property is more excellent, and bending workability and stress corrosion cracking resistance are also good. On the other hand, if the number of atoms of Ni is too large, the stress relaxation property becomes saturated and, in some cases, becomes rather poor and the strength becomes low. The upper limit of the compositional formula f4 is 10 or less, preferably 8 or less, and most preferably 6 or less. When in the above range, the effects of Ni and Sn can be maximized.

(Compositional relation f5)

Also, the stress relaxation characteristics are affected by the compound of Ni, P, and Ni and P in the solid state. Here, when the compositional relationship f5 = [Ni] / [P] is less than 16, the ratio of Ni and P compound to Ni in the solid solution state is increased, so that the stress relaxation property is deteriorated and the bending workability is deteriorated. That is, when the compositional relationship f5 = [Ni] / [P] is 16 or more, preferably 18 or more and optimally 20 or more, the stress relaxation property and bending workability become good. On the other hand, if the compositional relationship f5 = [Ni] / [P] exceeds 250, the amount of the compound formed of Ni and P and the amount of P to be solved become small, and the stress relaxation property is deteriorated. In addition, the effect of making the crystal grains finer is reduced, and the strength of the alloy is lowered. Therefore, the upper limit value of f5 is 250 or less, preferably 180 or less, and optimally 120 or less.

(Average crystal grain size)

In the copper alloy plate according to the present embodiment, the average crystal grain size can be set to about 1.5 탆 although it varies depending on the process. However, if the average crystal grain size of the copper alloy plate of the present embodiment is reduced to 1.5 占 퐉, the proportion of the grain boundaries formed with a width of several atoms becomes large, and the elongation, bending workability and stress relaxation characteristics are deteriorated. Therefore, in order to have high strength, high elongation, and good stress relaxation characteristics, an average crystal grain size is required to be 2.0 m or more. The lower limit of the average crystal grain size is preferably not less than 3 mu m, and most preferably not less than 4 mu m. On the other hand, as the crystal grain size increases, good elongation and bending workability are exhibited, but desired tensile strength and proof stress can not be obtained. It is necessary to make the average crystal grain size at least 9 μm or less. The upper limit of the average crystal grain size is preferably 8 占 퐉 or less, particularly 7 占 퐉 or less when the strength is emphasized. Thus, by setting the average crystal grain size to a narrower range, a highly excellent balance can be obtained between the bending workability, elongation, strength, conductivity, or stress relaxation characteristics.

(Precipitate)

For example, there is a relationship with time when annealing a rolled material subjected to cold rolling at a cold working rate of 50% or more. However, when the temperature exceeds a certain critical temperature, recrystallization nuclei are generated centering on grain boundaries in which processing strain is accumulated. In the case of the copper alloy plate according to the present embodiment, the grain size of recrystallized grains generated after nucleation is a recrystallized grain of 1 占 퐉 or 2 占 퐉 or smaller, though depending on the composition of the alloy. Is not replaced by recrystallized grains at all. In order to replace all or, for example, 95% or more of the recrystallized grains, a temperature higher than the temperature at which recrystallization nucleation is started, or a time longer than the time at which recrystallization nucleation is initiated is required. During this annealing, the recrystallized grains first generated grow together with temperature and time, and the crystal grain size becomes large. In order to maintain a fine recrystallized grain diameter, it is necessary to suppress the growth of recrystallized grains. In order to suppress the growth of recrystallized grains, P and Ni are contained in the present embodiment. Compounds (precipitates containing P and Ni) produced by P and Ni act like fins that inhibit the growth of recrystallized grains. The properties of the compound itself and the particle size of the compound are important for the compound (the precipitate containing P and Ni) produced by P and Ni to function as a fin as described above. That is, from the results of the study, it is found that the compounds (P and Ni-containing precipitates) produced by P and Ni in the composition range of the copper alloy sheet of this embodiment rarely inhibit elongation, When the grain size was 3 to 75 nm, it was found that the inhibition of elongation was small and the grain growth was effectively suppressed.

The precipitates containing P and Ni that inhibit the growth of the recrystallized grains have a circular or elliptic precipitate at the stage of the recrystallization heat treatment step and the average particle size of the precipitates is 3 to 75 nm, And the ratio of the number of 75 nm is 70% or more. If the average particle size of the precipitate is small, precipitation strengthening of the precipitate and effect of inhibiting the crystal grain growth are excessively passed, the recrystallized phase is reduced, the strength of the rolled material is increased, but the bending workability is poor. On the other hand, when the precipitate reaches, for example, 100 nm, the effect of suppressing grain growth is almost lost, and the bending workability is deteriorated. In addition, a circular or elliptical precipitate includes not only a complete circle or an ellipse, but also a circle or an ellipse.

In order to surely achieve the above-described action and effect, it is preferable that the average particle diameter of the circular or elliptic precipitate is 3 to 60 nm or the ratio of the number of the particle diameter of 3 to 60 nm in the precipitated particles is 70% or more. Optimally, the average particle diameter is 5 to 20 nm.

(Conductivity)

The copper alloy plate according to the present embodiment is used for a conductive member such as a connector, a terminal, a relay, a spring, a switch, a semiconductor, and a lead frame used for an automobile part, an electric part, an electronic part, a communication device, It is necessary to secure a conductivity of at least 24% IACS, preferably at least 26% IACS, and more preferably at least 28% IACS.

(Stress relaxation property)

The terminal and the connector are heated to a temperature of about 100 ° C when used in a place close to the engine room of an automobile. Therefore, in a state where stress of 80% of the proof stress of the alloy is applied at 150 ° C for 1000 hours, Rate is 25% or less, preferably 23% or less, optimally 20% or less. When the stress relaxation rate is increased, the strength (contact pressure, spring pressure) substantially equal to the stress relaxation rate is inhibited. Alternatively, the maximum contact pressure and the spring pressure of the effective value can be evaluated. That is, the maximum contact pressure and the spring pressure (effective stress) Pw of the effective value are represented by Pw = internal force x 80% (100% - stress relaxation rate (%)) Not only the stress relaxation property is high, but also the value of the above formula is desired to be high. The lowest level that can withstand use in a high temperature condition is 300 N / mm < ² > if the proof stress x 80% x (100% - stress relaxation rate (%)) If it is ² or more, it is suitable for use in a high temperature condition, and it is optimum if it is 330 N / mm ² or more. For example, in the case of Cu-30 mass% Zn, which is a representative alloy of brass having a proof stress of 500 N / mm ² , the proof stress x 80% x (100% - stress relaxation rate %)) in the value of about 70N / mm ^2, a proof stress, like 550N / mm ² of Cu-6 mass% Sn Phosphor Bronze, it is about 180N / mm ^2, the current practical alloys, possibly can not be satisfied.

(Balance index f6)

In the case of the rolled material after finish cold rolling or the rolled material subjected to the recovery heat treatment after finish cold rolling, or the rolled material subjected to the reflow Sn plating or the molten Sn plating, R / t = 1.0 T is the thickness of the rolled material), cracks do not occur, preferably, no cracks occur at R / t = 0.5, and a balance Index f6 = Pw x C / 100) ^1/2 is important. If the balance index f6 is a high value, it can be a material suitable for the terminal and connector in an environment close to a severe engine room. That is, (C / 100) ^1/2 which is an index of electrical characteristics, and the product of the effective stress can be a criterion for evaluating the terminal / connector in an environment close to a severe engine room. The balance index f6 needs to be at least 180 or more, preferably 190 or more, more preferably 200 or more, and most preferably 210 or more.

(Strength ratio YS ₉₀ / YS ₀ )

Generally, when the metal structure of the finished cold rolled steel sheet is observed, the test specimens taken in the rolling direction and the test specimens taken in the vertical direction exhibit a shape in which the crystal grains are elongated and compressed in the thickness direction in the rolling direction, , A difference in strength, bending workability occurs. In the concrete metal structure, the crystal grains are elongated crystal grains when viewed in a section parallel to the rolling surface, and when viewed from the cross section, the grains become grains compressed in the thickness direction and the tensile strength TS ₉₀ of the rolled material taken perpendicularly to the rolling direction, YS ₉₀ is higher than the tensile strength TS ₀ and the proof stress YS ₀ of the rolled material collected in the parallel direction. The strength ratio TS ₉₀ / TS ₀ and the yield ratio YS ₉₀ / YS ₀ of the rolled material are in excess of 1.05 and more than 1.07 , And in some cases it may reach 1.1. As the strength ratio TS ₉₀ / TS ₀ and the proof stress ratio YS ₉₀ / YS ₀ increase beyond 1.05, the bending workability of the specimen taken in the direction perpendicular to the rolling direction deteriorates. Conversely, depending on the manufacturing process, the strength ratio TS ₉₀ / TS ₀ and the yield ratio YS ₉₀ / YS ₀ may be 0.97, and in some cases, less than 0.95. With respect to the anisotropy of the strength plane, the yield strength ratio YS ₉₀ / YS ₀ and the tensile strength ratio TS ₉₀ / TS ₀ are all preferably 1.07 or less, more preferably 1.05 or less, optimally 1.03 or less, , Preferably 0.95 or more, more preferably 0.97 or more, optimally 0.99 or more. Various members such as a terminal and a connector to be subjected to the copper alloy sheet of the present embodiment are used in the rolling direction and in the vertical direction, that is, in the direction parallel to the rolling direction and in the direction perpendicular to the rolling direction It is desired that there is no difference in properties such as tensile strength, proof stress and bending workability in the rolling direction and the vertical direction from the yarn-used surface and the product processing surface because both directions are often used.

In the copper alloy plates according to the first to fourth embodiments of the present invention, the interaction of Zn, Sn, P, and Ni, and compositional relations f1 to f5 are satisfied and the average crystal grain size is 2 to 9 占 퐉. By controlling the size of the precipitate formed of Ni and the ratio between these elements to a predetermined value and by making the rolled material in the manufacturing process to be described next, The difference between the tensile strength and the proof stress of the rolled material is eliminated. As a result, in the copper alloy sheets of the first to fourth embodiments of the present invention, the ratio of the internal force YS _{90 in the} direction of 90 degrees to the rolling direction and the ratio YS ₀ of the internal force YS _{0 in} the direction of 0 degrees to the rolling direction ₉₀ / YS ₀ , and 0.95? YS ₉₀ / YS _0? 1.07. In this embodiment, about 90 degrees, a tensile strength TS of the direction forming ₉₀ with respect to the rolling direction, a tensile strength of forming 0 degrees to the rolling direction, the direction ₀ TS TS ratio of ₉₀ / TS _0, 0.95≤TS ₉₀ / TS ₀ & le; 1.07.

(Other characteristics)

In the copper alloy plate of the present embodiment, it is preferable that the characteristics other than the above-described conductivity and stress relaxation resistance are also defined as follows.

It is preferable that the copper alloy plate according to the present embodiment has a high strength and a bending workability of R / t ≤ 1.0 when evaluated by W bending for many applications, and more preferably R / t? 0.5. Particularly, in the use of terminals, connectors, and electric and electronic parts, it is preferable that the bending workability is R / t? 1.0 with respect to bending in both directions parallel and perpendicular to the rolling direction, and R / t < / = 0.5.

Further, terminals, connectors and the like are usually subjected to Sn plating on the surface in terms of corrosion resistance, contact resistance, and bonding. In this case, in the state of the coil, the Sn-plated, the reflowed-Sn-plated, or the terminal and the connector are formed, and then the Sn plating is performed. Therefore, it is necessary that Sn plating property, that is, solder wettability, is good for terminal / connector use or electric / electronic parts. In the case of Sn plating, particularly Pb-free solder plating after forming the terminal and the connector, the Sn plating property is not particularly problematic in the coil state, but is left for a predetermined period of time, There is a possibility that the plating property and the solder wettability are deteriorated by the surface oxidation during the settling period. There is a demand for a copper alloy having good solder wettability on its material, having a slight surface oxidation, hard to oxidize the surface, and good solder wettability after being left atmospheric. The evaluation of the solder wettability varies, but from the viewpoint of industrial production, it is appropriate to evaluate the time at which the solder is wetted quickly.

Next, a method of manufacturing a copper alloy plate according to the first to fourth embodiments of the present invention will be described.

Further, in the present specification, it is assumed that the processing to be performed at a temperature lower than the recrystallization temperature of the copper alloy material to be processed at a temperature higher than the cold processing and recrystallization temperature is referred to as hot processing, , Cold rolling, and hot rolling. The recrystallization is defined as the formation of a new, undistorted crystal structure from a structure in which there is a change from one crystal structure to another, or a deformation caused by processing.

First, an ingot having the above-described composition is prepared, and the ingot is hot-worked (typically, hot-rolled). The starting temperature of the hot rolling is set to 800 ° C or higher, preferably 840 ° C or higher, in order to make each element solid, and 950 ° C or lower, preferably 920 ° C or lower in terms of energy cost and hot ductility . In order to make the P and Ni more solid-state, the temperature at the end of the final rolling or the temperature range of 650 to 350 占 폚 is set so that at least these precipitates do not become coarse (rough, coarse) It is preferable to cool at a cooling rate of 1 deg. C / second or more. If the precipitate is coarsened in the hot rolling step, it is difficult to disappear by the heat treatment such as the subsequent annealing step and the elongation of the final rolled product is inhibited.

Further, in the case of producing a plate-like ingot having a thickness of about 15 to 20 mm according to the continuous casting method, hot working (hot rolling) can be omitted. In this case, homogenization heat treatment may be performed at 650 ° C to 850 ° C after casting. When the hot rolling is not carried out, heat treatment is performed at about 700 ° C. or about 800 ° C. for 1 hour or more, and the coarse compound of Ni and P produced in the casting step is once solid-solved, It is preferable to make the concentration distribution of Ni or the like uniform.

Then, the copper alloy material is subjected to cold rolling to a predetermined thickness, followed by cold rolling followed by recrystallization heat treatment. The cold rolling step, annealing step or recrystallization heat treatment step is carried out once or plural times depending on the final product thickness.

As the annealing method and recrystallization heat treatment method, there are a batch type heat treatment method in which heating is maintained for a long time and a continuous heat treatment in high temperature and short time. The final recrystallization heat treatment method has a favorable stress relaxation property particularly in a high-temperature and short-time heat treatment. This is because P does not completely precipitate with Ni, and a predetermined concentration of P exists in a solid state. In the recrystallization heat treatment step by continuous heat treatment at a high temperature for a short time, a heating step of heating the copper alloy material to a predetermined temperature by using a continuous heat treatment furnace, and a step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step And a cooling step of cooling the copper alloy material to a predetermined temperature after the retaining step. In the recrystallization heat treatment step, the maximum reaching temperature of the copper alloy material is set to Tmax (占 폚) (Tm (min)) is a time period during which the substrate is heated and held in a temperature range from a temperature 50 deg. C lower than the maximum attained temperature to a maximum attained temperature,

560? Tmax? 790,

0.04? Tm? 1.0,

520? It1 = (Tmax-30 占 tm-1 ^/2 )? 690

.

Under the conditions of the final recrystallization heat treatment, if the lower limit of the maximum reaching temperature, the holding time, or the range of the heat treatment index It1 of the continuous heat treatment conditions at high temperature and short time is less than the lower limit of the range of the heat treatment index It1, an unrecrystallized portion remains or an average crystal grain size Ultrafine grain state. In addition, when annealing is performed beyond the upper limit of the maximum reaching temperature, the holding time, or the upper limit of the range of the heat treatment index It1, a fine metal structure having an average crystal grain size of 9 占 퐉 or less can not be obtained. If the concentration is outside the range, the amount of Ni to be solubilized, the amount of P, and the balance between Ni and precipitates of P are collapsed and the stress relaxation characteristics are deteriorated.

In cooling the recrystallization heat treatment step, it is preferable to cool at a temperature of 5 占 폚 / sec or more in a temperature range from "the maximum attained temperature -50 占 폚" to 400 占 폚, more preferably 10 占 폚 / sec Cooling under the above conditions and optimally cooling under the conditions of 15 deg. C / sec or more improves the stress relaxation characteristics. If the cooling rate is low, coarse precipitates appear, the ratio of the precipitates of P and Ni increases, and the amount of P solubilized decreases, resulting in poor stress relaxation characteristics and bending workability.

In order to obtain a homogeneous fine-grained recrystallized grains having no blisters in the recrystallization heat treatment step, it is not sufficient to lower the stacking defect energy. Therefore, in order to increase the site of formation of recrystallization nuclei, deformation by cold rolling, It is necessary to accumulate deformation of Therefore, the cold working rate in the cold rolling before the recrystallization heat treatment step is required to be 55% or more, preferably 60% or more. On the other hand, if the cold working rate of the cold rolling before the recrystallization heat treatment step is too high, problems such as deformation may occur. Therefore, it is preferably 98% or less and optimally 96% or less. That is, in order to increase the site of recrystallization nucleus formation due to the physical action, it is effective to increase the cold working rate, and by adding a high processing rate within a range allowing deformation of the product, Can be obtained.

The recrystallization heat treatment step can also be heat-treated by batch annealing, and is maintained at a temperature in the range of 400 占 폚 to 650 占 폚 for 1 hour to 24 hours. However, even in batch annealing, it is necessary to adjust the conditions so that the average crystal grain size and the grain size of the precipitate become the above-mentioned predetermined range in the final heat treatment step. The final heat treatment step is preferably a continuous heat treatment at a high temperature for a short period of time which allows a predetermined constant concentration of P to be in a solid state and the intermediate recrystallization heat treatment to be carried out if necessary, - Even with a continuous heat treatment for a short time, the properties of the final rolled material are not greatly affected.

Next, finish rolling is performed on the copper alloy material subjected to the final recrystallization heat treatment step. After the finish cold rolling, a heat treatment at a maximum attained temperature of 150 to 580 占 폚, a holding time of 0.02 to 100 minutes in a temperature range from a "maximum attained temperature -50 占 폚" to a maximum attained temperature, It is preferable to carry out the recovery heat treatment step in which the index It2 satisfies the relationship of 120? It2?

Specifically, the method includes a heating step of heating the copper alloy material to a predetermined temperature after the finish cold rolling step, a holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step, And a cooling step of cooling the material to a predetermined temperature, wherein a maximum reaching temperature of the copper alloy material is set to Tmax2 (占 폚), and a temperature range from a temperature 50 占 폚 lower than the maximum reaching temperature of the copper alloy material to a maximum reaching temperature , The time of heating and holding is set to tm2 (min)

150? Tmax2? 580,

0.02? Tm2? 100,

120? It2 = (Tmax2-25? Tm2? ^1/2 )? 390

It is preferable that the heat treatment is performed in a heat treatment process.

This recovery heat treatment step improves the stress relaxation rate, spring limit value, bending workability and elongation of the rolled material by a low-temperature or short-time recovery heat treatment without recrystallization, and restores the electric conductivity decreased by cold rolling . In the heat treatment index It2, the lower limit is preferably 200 or more, and the upper limit is preferably 380 or less. By performing the above-described recovery heat treatment step, the stress relaxation rate becomes about 1/2, the stress relaxation property is improved, the spring limit is improved to 1.5 to 2 times, and the conductivity is 0.5 to 2% IACS is improved.

In addition, in a Sn plating process such as molten Sn plating or reflow Sn plating, it is heated at a temperature of about 150 캜 to about 300 캜 for a short period of time but after molding in a rolled material, and in some cases, terminals and connectors. This Sn plating process has little effect on the characteristics after the recovery heat treatment even after the recovery heat treatment. On the other hand, the heating process of the Sn plating process becomes an alternative process of the recovery heat treatment process, and improves the stress relaxation characteristics, the spring strength, and the bending workability of the rolled material.

By the above-described manufacturing process, the copper alloy sheets of the first to fourth embodiments of the present invention are produced.

As described above, the copper alloy plates according to the first to fourth embodiments of the present invention have excellent stress corrosion cracking resistance, stress relaxation characteristics, high strength, and good bending workability. From these characteristics, it is a suitable material for electronic / electronic parts and automobile parts, such as connectors, terminals, relays, switches, etc., which are excellent in cost performance.

It is preferable that the average crystal grain size is 2 to 9 占 퐉 and the conductivity is not less than 24% IACS, preferably not less than 26% IACS, and the upper limit is not specifically defined but is 42% IACS or less and circular or elliptical precipitates And the average particle size of the precipitate is 3 to 75 nm, the balance of the strength, strength and bending workability is excellent, and the balance of the stress relaxation property, the stress relaxation property and the electric conductivity, and the effective stress at 150 캜 are high It becomes a suitable material for electronic / electronic parts such as connectors, terminals, relays, switches, and automobile parts, which are used in a harsh environment.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and can be appropriately changed without departing from the technical idea of the invention.

Example

Hereinafter, the results of verification tests conducted to confirm the effects of the present invention are shown. The following embodiments are for explaining the effects of the present invention, and the configurations, processes, and conditions described in the embodiments do not limit the technical scope of the present invention.

A copper alloy plate according to the first to fourth embodiments of the present invention and a copper alloy plate having a composition for comparison were used and the manufacturing process was changed to produce a sample. The composition of the copper alloy is shown in Tables 1 to 3. Tables 1 to 3 show the values of the composition relation expressions f1, f2, f3, f4, and f5 shown in the above-described embodiments.

The samples were produced in three types of A, B, and C, and the manufacturing conditions were further changed in each of the production steps. The manufacturing process A was carried out by an actual mass production facility, and the manufacturing processes B and C were performed by an experimental facility. Table 4 shows the manufacturing conditions of each manufacturing process. In the manufacturing process A8 and the manufacturing process A9, the heat treatment index deviates from the setting condition range of the present invention.

In the manufacturing process A (A1 to A33), raw materials were melted in a medium-frequency melting furnace having an internal volume of 10 tons, and an ingot having a thickness of 190 mm and a width of 630 mm was produced in semi-continuous casting. The ingots were each cut to a length of 1.5 m and then subjected to a hot rolling step (plate thickness: 13 mm) - cooling step - milling step (plate thickness: 12 mm) - a first cold rolling step (Plate thickness: 1.5 mm, cold working rate: 67%) - Final annealing step (recrystallization) (second annealing step (second annealing step) Heat treatment process) - Finish cold rolling process (plate thickness 0.3 mm, cold working rate 40%) - Recovery heat treatment process was performed. In the manufacturing process A10, the first cold rolling step and the annealing step are omitted. The above-mentioned holding time is a time to be maintained in a high-temperature region from the highest attained temperature to the highest attained temperature -50 캜.

The hot rolling starting temperature in the hot rolling step was 860 占 폚, hot rolled to a plate thickness of 13 mm, and then subjected to shower water cooling in the cooling step. In this specification, the hot rolling starting temperature and the ingot heating temperature have the same meaning. The average cooling rate in the cooling step is set to be the average cooling rate in the temperature range from the temperature of the rolled material after the final hot rolling or the temperature of the rolled material to 650 ° C to 350 ° C, Respectively. The average cooling rate measured was 4 ° C / sec.

In the recrystallization heat treatment step, the maximum arrival temperature Tmax (° C) of the rolled material and the holding time tm (min) in the temperature range from the temperature 50 ° C lower than the maximum attained temperature of the rolled material to the maximum attained temperature are set to (690 ° C, 0.09 min), (660 캜, 0.07 min), (710 캜, 0.16 min), (770 캜, 0.25 min) and (620 캜, 0.06 min). In the production step A1, the recrystallization heat treatment was carried out at 470 占 폚 for 4 hours using batch annealing. In the steps of performing the high-temperature recrystallization heat treatment for a short period of time, in steps A31 and A32, an average cooling rate in the range of 50 占 폚 lower to 400 占 폚 than the maximum attainable temperature of the rolled material at 3 占 폚 / Deg.] C / sec, and the other steps were performed at 20 to 30 [deg.] C / sec.

Then, as described above, the cold working ratio in the finish cold rolling step was set to 40%.

In the recovery heat treatment step, the holding time tm (min) in the temperature range from the temperature which is lower than the maximum attained temperature of the rolled material by 50 占 폚 to the maximum attained temperature is 450 占 폚, Was set to 0.05 minute. However, in the manufacturing process A6, the recovery heat treatment process was not performed. In the production step A5, the obtained sample was heated in an electric furnace at 300 DEG C for 30 minutes and air-cooled. In the production step A4, the obtained sample was completely immersed in an oil bath at 350 DEG C for 0.07 minutes and then air-cooled. This heat treatment is a heat treatment condition corresponding to the molten Sn plating treatment.

The manufacturing steps B (B1 to B4) were performed as follows.

A test ingot in a laboratory having a thickness of 40 mm, a width of 120 mm and a length of 190 mm was cut out from the ingot of the manufacturing process A and then subjected to a hot rolling step (plate thickness 6 mm) - a cooling step (shower water cooling) - Cold rolling process (thickness 0.5 mm) - Recrystallization heat treatment process - Finish cold rolling process (plate thickness 0.3 mm, processing rate 40%) - Recovery heat treatment process was performed.

In the hot rolling step, the ingot was heated to 860 캜 and hot-rolled to a thickness of 6 mm. The cooling rate in the cooling step (the temperature of the rolled material after hot rolling, or the cooling rate from when the temperature of the rolled material was 650 ° C to 350 ° C) was 3 ° C / second.

After cold rolling at a sheet thickness of 0.5 mm, the recrystallization heat treatment step was carried out at a Tmax of 690 (캜) and a holding time tm of 0.09 min, and an average cooling rate of 640 캜 to 400 캜 at 25 캜 / sec. In the manufacturing process B1, the recrystallization heat treatment was performed under the condition of 4 hours holding at 480 DEG C by batch annealing. Then, it was cold-rolled to 0.3 mm in the finish cold rolling process. Regarding the manufacturing process B1 and the manufacturing process B2, the recovery heat treatment process was performed under conditions of Tmax of 450 (° C) and holding time tm of 0.05 minute. In the manufacturing process B4, the resultant was heated in an electric furnace at 300 DEG C for 30 minutes and then air-cooled. In the manufacturing process B3, the obtained sample was completely immersed in an oil bath at 250 占 폚 for 0.15 minutes and then air-cooled. This heat treatment is also a heat treatment condition corresponding to the molten Sn plating treatment.

In the manufacturing process B5 and the manufacturing process B5A, after the homogeneous annealing at 700 占 폚 for 4 hours without hot rolling, the plate thickness was reduced to 6 mm by cold rolling, and annealing was performed at 620 占 폚 for 4 hours. The average thickness Tmax was set to 690 占 폚, the holding time tm was set to 0.09 minutes, the average cooling rate from 640 占 폚 to 400 占 폚 was set at 25 占 폚 / In the manufacturing process B5A, recrystallization heat treatment was performed under the condition of 4 hours holding at 480 占 폚 using batch annealing. Then, the steel sheet was cold-rolled down to 0.3 mm in the finish cold rolling process, and the recovery heat treatment process was carried out under the condition of heating in an electric furnace at 300 ° C for 30 minutes.

In the manufacturing process B and a manufacturing process C described later, in the manufacturing process A, a process corresponding to a short-time heat treatment performed in a continuous annealing line or the like is performed by immersing a rolled material in a salt bath, The temperature of the solution in the bath was set to be the time during which the rolling material was completely immersed. In addition, a salt (solution) was a mixture of BaCl, KCl and NaCl.

Further, as a laboratory test, the manufacturing process C (C1, C1A, C2) was performed as follows. And melted and cast into an electric furnace of a laboratory so as to be a predetermined component to obtain a test ingot in a laboratory having a thickness of 40 mm, a width of 120 mm and a length of 190 mm. Thereafter, the same process as in the above-described manufacturing process B was performed. That is, the ingot was heated to 860 占 폚, hot rolled to a thickness of 6 mm, and the temperature of the rolled material after the hot rolling was changed from the temperature of 650 占 폚 to 350 占 폚 at the cooling rate 3 Lt; 0 > C / sec. After cooling, the surface was pickled and cold rolled to a thickness of 0.5 mm. In the recrystallization heat treatment step, the manufacturing process C1 is carried out under the conditions of Tmax of 690 (占 폚), a holding time tm of 0.09 min, an average cooling rate of 640 占 폚 to 400 占 폚 at 25 占 폚 / The conditions of time and the production process C2 were carried out at 380 DEG C for 4 hours. The recovering heat treatment step is maintained at 300 DEG C for 30 minutes by using an electric furnace in a laboratory in the manufacturing step C1 and the manufacturing step C1A, and is maintained at 30 DEG C for 230 DEG C in the manufacturing step C2 in a cold rolling step in the finish cold- Minute maintenance.

As the evaluation of the copper alloy sheet prepared by the above-mentioned method, it was confirmed that the evaluation of the copper alloy sheet was conducted by observing the metal structure (mean grain size and average particle size of the precipitate), conductivity, stress relaxation property, stress corrosion cracking resistance, solder wettability, The processability was evaluated. The evaluation results are shown in Tables 5 to 20.

(Average crystal grain size)

The average grain size of the recrystallized grains was measured by a metal microscope photograph such as 600 times, 300 times, and 150 times, and an appropriate magnification was selected according to the grain size, and the grain size of the new copper product (expanded copper product) in JIS H 0501 It was measured according to the quadrature method of the test method. Also, twin crystals are not regarded as crystal grains. The difficulty in judging from the metallographic microscope was obtained by the FE-SEM-EBSP (Electron Back Scattering Diffraction Pattern) method. That is, FE-SEM is JSM-7000F manufactured by Nihon Denshi Co., Ltd., and TSL Solutions OIM-Ver. 5.1 was used, and the average crystal grain size was obtained from a grain size map (Grain map) having an analysis magnification of 200 times and 500 times. The calculation method of the average crystal grain size is according to the quadratic method (JIS H 0501).

Further, one crystal grain is stretched by rolling, but the volume of the crystal grain is hardly changed by rolling. It is possible to estimate the average crystal grain size in the recrystallization step from the average crystal grain size measured in accordance with the quadratic method in the section cut parallel to the rolling direction of the plate material.

(Particle size of the precipitate)

The average particle diameter of the precipitate was obtained as follows. The contrast of the precipitate was elliptically approximated using an image analysis software "Win ROOF" of 500,000 times and 100,000 times (detection limits are 1.0 nm and 5 nm, respectively), and the rising average value of the long axis and short axis All the precipitated particles in the field of view were determined, and the average value was determined as the average particle diameter. In addition, the detection limits of the particle diameters were set to 1.0 nm and 5 nm, respectively, at a measurement of 500,000 times and 100,000 times, and those below the detection limits were regarded as noise and were not included in the calculation of the average particle diameter. In addition, the average particle diameter was measured at a value of 100,000 times, and a value of 100,000 times or less with an average particle diameter of 10 nm or less as the boundary. In the case of a transmission electron microscope, it is difficult to accurately grasp precipitate information because the dislocation density is high in cold working materials. Since the size of the precipitate does not change depending on the cold working, the recrystallization portion after the recrystallization heat treatment step before the finish cold rolling step was observed at this time. Two measurement points were averaged at two places where a length of 1/4 of the plate thickness was measured from both the front and back surfaces of the rolled material.

(Conductivity)

The electric conductivity was measured using a conductivity meter (SIGMATEST D2.068) manufactured by Nihon Ulster K.K. In this specification, the terms "electrical conduction" and "conduction" are used interchangeably. Since the thermal conductivity and the electrical conductivity are strongly correlated, the higher the electrical conductivity, the better the thermal conductivity.

(Stress relaxation property)

The stress relaxation rate was measured according to JCBA T309: 2004 as follows. One side support beam screw type jig was used for the stress relaxation test of the specimen. The test specimens were taken from the direction of 0 degree (parallel) and 90 degree (vertical) in the rolling direction, and the shape of the test piece was a plate thickness t 占 10 mm width 占 60 mm length. The load stress on the specimen was 80% of the 0.2% proof stress and exposed for 1000 hours in an atmosphere of 150 캜 and 120 캜. The stress relaxation rate,

Stress relaxation rate = (displacement after opening / displacement during stress load) x 100 (%)

Respectively. In the present invention, the stress relaxation rate is preferably small.

In the evaluation at 120 占 폚, the stress relaxation rate was 8% or less as the evaluation A (excellent), 8% to 13% as the evaluation B (good), and the evaluation exceeding 13% as the evaluation C . The stress relieving property required here is assumed to be a high reliability or severe case.

The effective stress Pw at 150 DEG C for 1000 hours is expressed as

Pw = proof stress {(YS ₀ + YS ₉₀ ) / 2} x 80% (100% - stress relaxation rate (%))

. The proof stress and the stress relaxation characteristics may not be obtained from the relationship of the slitter width after the slitter, that is, when the width is smaller than 60 mm, from the direction making 90 degrees (vertical) in the rolling direction. In that case, it is assumed that the stress relaxation property and Pw are evaluated only in the 0 degree (parallel) direction in the rolling direction.

In addition, T3 and T36 (alloys Nos. 1 and 3), the effective stress Pw calculated from the result of the stress relaxation test in the direction of 90 degrees (vertical) in the rolling direction and the 0 degree (parallel) direction in the rolling direction, The effective stress Pw calculated from the result of the stress relaxation test only in the 0 degree (parallel) direction in the rolling direction and the effective stress Pw calculated from the result of the stress relaxation test only in the 90 degree Confirmed.

(Balance index f6)

From the measured conductivity C (% IACS) and effective stress Pw (N / mm ² ), the balance index f6 was calculated by the following equation.

f6 = Pw x (C / 100) ^1/2

(Stress corrosion cracking resistance)

The stress corrosion cracking resistance was measured by using a test vessel and a test solution specified in JIS H 3250, and using an aqueous solution of an equal amount of ammonia water and water.

In the stress corrosion cracking test, in order to investigate the susceptibility of the stress corrosion crack to the load stress, a rolled material having a bending stress of 80% of proof stress was applied to the above ammonia atmosphere And the stress corrosion cracking resistance was evaluated from the stress relaxation rate. That is, if fine cracks are generated, the stress relaxation rate is increased when the degree of cracking does not return to the original state and the stress corrosion cracking resistance can be evaluated. The stress relaxation rate of 25% or less at 48-hour exposure was evaluated as A, and the stress relaxation rate was 25% or less at 24 hours exposure even when the stress relaxation rate exceeded 25% at 48-hour exposure. (No problem in practical use) and rated as B, and the stress relaxation rate exceeded 25% at 24 hours exposure, and the stress corrosion cracking resistance was poor (there was a problem in practical use) And rated C for evaluation. In addition, the stress corrosion cracking resistance required in the present invention is assumed to be a high reliability or a severe case.

(Solder wettability)

The solder wettability was measured by a meniscograph method. The test equipment is RHESCA (type: SAT-5200). A test piece was taken from the rolling direction and cut to a thickness of 0.3 mm x width of 10 mm x length of 25 mm. The solder used was Sn-3.5 mass% Ag-0.7 mass% Cu and pure Sn. As a pre-treatment, acetone degreasing → 15% sulfuric acid washing → water washing → acetone degreasing was carried out. As the flux, a standard rosin flux (NA200, Seisakusho Co., Ltd.) was used. An evaluation test was conducted under the conditions of a soldering bath temperature of 270 캜, an immersion depth of 2 mm, an immersion speed of 15 mm / sec, and an immersion time of 15 seconds.

Evaluation of the solder wettability was performed at zero cross time. That is, the time required until the solder is immersed in the bath and then completely wetted, and when the zero cross time is completely wetted within 5 seconds, that is, within 5 seconds after the immersion in the solder bath, the solder wettability is a problem in practical use , And when the zero cross time is within 2 seconds, it is evaluated as being particularly excellent. When the zero cross time exceeds 5 seconds, there is a problem in practical use, so the evaluation is made in C. Further, after the final step of the finish rolling or the recovery heat treatment, the sample was cleaned with sulfuric acid and the surface was polished with an abrasive paper of 800 times to obtain a surface free from oxidation, and the sample was allowed to stand in an indoor environment for 3 days or 10 days I used something. Further, in the table, "-1" and "-2" were evaluated by using solder of Sn-3.5 mass% Ag-0.7 mass% Cu for 3 days and 10 days respectively. And the results of the test in three days.

(Mechanical Properties)

The tensile strength, the proof stress and the elongation were measured according to the methods specified in JIS Z 2201 and JIS Z 2241, and the test specimen was made with the No. 5 test specimen. The test was conducted in the direction of 0 占 with respect to the rolling direction and in the direction of 90 占 with respect to the rolling direction.

(Bending workability)

The bending workability was evaluated by W bending at a bending angle of 90 degrees specified in JIS H 3110. The bending test (W bending) was carried out as follows. The bending radius R of the tip of the bending jig is 0.5 times (bending radius = 0.15 mm, R / t = 0.5) times the thickness t of the material (bending radius = 0.3 mm, R / . The sample was taken from the so-called Bad Way direction at 90 degrees to the rolling direction and from the direction at 0 degree in the rolling direction in the direction called Good Way. The evaluation of the bending workability was made by observing with a real microscope of 50 times and judging the presence or absence of cracks. It was evaluated that the bending radius was 0.5 times the thickness of the material (R / t = 0.5) The evaluation C was that the radius was 1.0 times the thickness of the material and no crack occurred, and B was the thickness of the material (R / t = 1.0) and cracks occurred. Further, in the bending test where the bending workability is R / t? 0.5, the bending radius is not more than 0.5 times the thickness of the material (R / t = 0.5).

From the above-described evaluation results, the following were confirmed with respect to the composition and compositional relationship formula and characteristics.

The composition of the copper alloy plate was as follows. The comparative alloy is as follows.

Alloy No. 100, and 121, the content of Zn is smaller than the composition range of the invention alloy.

Alloy No. 101 has a smaller amount of Sn than the composition range of the inventive alloy.

Alloy No. 102, the content of P is larger than the composition range of the inventive alloy.

Alloy No. 103, the content of Zn is larger than the composition range of the inventive alloy.

Alloy No. 104, the content of P is smaller than the composition range of the invention alloy.

Alloy No. 105 has a higher content of Sn than the composition range of the inventive alloys.

Alloy No. 106, and 122 have a Ni content lower than that of the inventive alloys.

Alloy No. 107 does not satisfy the range of the compositional relations f2 and f3 of the inventive alloys.

Alloy No. 108 and 109 do not satisfy the composition relation formula f1 of the invention alloy.

Alloy No. 110 to 113 do not satisfy the composition relation formula f4 of the inventive alloy.

Alloy No. 114 does not satisfy the composition relation formula f3 of the inventive alloy.

Alloy No. 115 and 116 do not satisfy the composition relation formula f5 of the invention alloy.

Alloy No. 118 to 120 are ordinary brass.

Alloy No. 117, and 123 have a large content of Fe and Co.

(1) If the content of P is larger than the range of the alloy of the present invention, the average grain size of the precipitated grains after the recrystallization heat treatment step becomes small and the average grain size becomes small, so that the bending workability and the stress relaxation rate become worse Reference). When the content of P is smaller than the range of the alloy of the present invention or Ni / P of the compositional relationship f5 is larger than 250, the average grain size and average grain size of the precipitated grains after the recrystallization heat treatment step become larger, The strength is lowered and the stress relaxation rate is deteriorated. When Ni / P is 180 or less, or more preferably 120 or less, the tensile strength and the proof stress are increased, and the stress relaxation rate is improved. When the Ni / P of f5 is smaller than the set range, the bending workability and the stress relaxation rate are deteriorated (see alloys Nos. 104, 116, 115, 13 and 18).

(2) If the content of Zn is less than the range of the alloy of the present invention, the average crystal grain size after the recrystallization heat treatment step becomes large and the tensile strength becomes low. Further, an effect suited to the Ni content can not be obtained, and the stress relaxation rate is deteriorated (see Alloy No. 100, etc.). Zn content: about 4 mass% is a boundary value to satisfy tensile strength, stress relaxation property, and effective stress Pw (see alloys Nos. 1, 10 and 100). If the content of Zn is larger than the range of the invention alloy, the conductivity, tensile strength, proof stress, stress relaxation rate, bending workability, stress corrosion cracking resistance and solder wettability are deteriorated. When the content of Zn is 12 mass% or less and 10 mass% or less, the above characteristics become good (see Alloys No. 103, 12, 15, 18, etc.).

(3) If the content of Sn is larger than the range of the present invention, the bending workability and the stress relaxation property are also deteriorated, and the conductivity is also lowered. The tensile strength and the proof stress in the vertical direction become larger with respect to the rolling direction. On the other hand, if the content of Sn is less than the range of the present invention, the strength is low and the stress relaxation property is deteriorated. When the Ni content is less than 1.0% by mass, the stress relaxation property becomes good (see Alloys Nos. 101, 105, 106, 122, 17, 19, etc.).

(4) When the compositional relationship f1 is smaller than the conditional range of the invention alloy, the average crystal grain size after the recrystallization heat treatment step is large, the tensile strength and the proof stress are low, and the stress relaxation characteristics do not have an effect suited to the Ni content , bad. If the compositional relationship f1 is larger than the range of the invention alloy, the stress corrosion cracking resistance, bending workability, and solder wettability are poor and the conductivity is also low. In addition, an effect suited to the Ni content is not obtained, and the stress relaxation property is poor. The value of f1 corresponds to the boundary value of these characteristics at the lower limit of about 7 and at the upper limit of about 18 or about 16. When the value of f1 is smaller than 14, the above characteristics become slightly better (see alloys Nos. 108, 109, 12, 1, 15, 18, etc.).

(5) If the compositional relationship f2 is larger than the range of the invention alloy, the stress corrosion cracking resistance is deteriorated and the stress relaxation property and bending workability are also poor. The value of the compositional relationship f2, 9 to 11, corresponds to the value of the boundary with respect to both good and bad of these characteristics. When the value of f2 is less than 8, the stress corrosion cracking resistance, the stress relaxation property and the bending workability are improved (see alloys Nos. 107, 103, 12, 15 and 18).

(6) If the compositional relationship f3 is smaller than the range of the invention alloy, the stress corrosion cracking resistance, the stress relaxation property, and the bending workability are deteriorated. The value of the boundary of f3 is in the vicinity of 0.3 to 0.35. When the value of f3 is larger than 0.4, the stress corrosion cracking resistance, the stress relaxation property and the bending workability are improved (see alloys Nos. 107, 114, 2, 15 and the like).

(7) If the compositional relation f4 is smaller than the range of the invention alloy, the stress relaxation property is deteriorated, and the bending workability and the stress corrosion cracking resistance are lowered. The tensile strength and the proof stress in the vertical direction become larger with respect to the rolling direction. If the compositional relationship f4 is larger than the range of the invention alloy, the stress relaxation property is deteriorated (see alloys Nos. 110 to 113, 14, 17, etc.).

As described above, even when the concentrations of Zn, Sn, Ni and P are in the predetermined concentration ranges, if the values of the compositional relations f1, f2, f3, f4 and f5 deviate from the predetermined ranges, the stress corrosion cracking resistance, It does not satisfy any one of characteristics, strength, bending workability, solder wettability, and conductivity.

(8) It is preferable to contain at least one element selected from Al, Fe, Co, Mg, Mn, Ti, Zr, Cr, Si, Sb, As, and Pb to improve the strength, Improvement of the stress corrosion cracking resistance is confirmed (see Alloys No. 20 to 32 and the like).

(9) If the content of Fe is 0.08% by mass or the content of Co is 0.07% by mass, the average crystal grain size becomes small, and the bending workability and the stress relaxation property become poor (see alloy Nos. 117 and 123).

In the case of using the copper alloy plate of the present invention, the following results were obtained.

(1) Manufacturing process A using mass production facilities and manufacturing process B using experimental equipment In the case of alloys, when the manufacturing conditions are the same, the metal structures after the recrystallization heat treatment in both processes have the same average crystal grain size and precipitate size, The average particle diameter is almost the same, and almost equal mechanical properties, stress relaxation characteristics (including stress relaxation rate, effective stress relaxation property, product of effective stress and half power of conductivity), stress corrosion cracking resistance, (See Test Nos. T10, T12, T26, T28 and the like).

(2) Even when the number of times of annealing (recrystallization heat treatment step) is once or twice, there is no difference in the average crystal grain size, and substantially equivalent mechanical properties, stress relaxation characteristics, stress corrosion cracking resistance and solder wettability are obtained T2, T3, T10, T18, T19, T26, etc.).

(3) The final recrystallization heat treatment step has a better stress relaxation property than the annealing step in the high temperature and short time heat treatment (see Test Nos. T1, T2, T3, T17, T18, T19, T102, . Further, in the high-temperature and short-time heat treatment, the stress relaxation is slightly improved at a cooling rate of 5 占 폚 / sec as a boundary. 10 deg. C / sec or more, or 15 deg. C / sec or more becomes slightly better. T39, T50, T55, T55, T55, T55, T55, T55, T55, T55, T55, T55, , T3, etc.).

(4) Even though the process is not subjected to hot rolling, the grain size of the precipitate is slightly larger than that in the step of passing through the hot rolling step, but almost equivalent mechanical properties, stress relaxation characteristics, stress corrosion cracking resistance and solder wettability are obtained Test No. T14, T15, T46, T47, etc.).

(5) If the coefficient It1 of the recrystallization heat treatment is within the setting range, the average crystal grain size and precipitate become large and the proof stress is slightly low, but the stress relaxation characteristic is slightly better. When the coefficient It1 of the recrystallization heat treatment is within the setting range and is small, the average crystal grain size and precipitate become small and the proof stress is slightly high, but the stress relaxation characteristic is slightly worse. If it is lower than the set condition, it is not completely recrystallized and the bending workability is poor. If It1 is too large, the average crystal grain size becomes large, the particle size of the precipitate becomes large, the proof stress is low, and the stress relaxation characteristic also becomes low (see Tests T3, T3C, T7, T8 and T9).

(6) When the value of f1 is about 16, which is close to the upper limit, the bending workability and the solder wettability are slightly deteriorated, and the susceptibility to stress corrosion cracking is slightly increased (see alloys Nos. 12 and 27).

(7) If the value of f2 is about 9, the susceptibility to stress corrosion cracking becomes slightly higher (See alloys Nos. 15, 20, and 22).

(8) When the value of f3 is about 0.35 which is lower in the setting range, the stress relaxation property is slightly worse, and the susceptibility to stress corrosion cracking is slightly increased (see Alloys No. 20, 27, 31, etc.).

(9) If the value of f4 is 1.8 to 2, which is slightly lower than the setting range, the stress relaxation property is slightly deteriorated (see Alloy No. 14, etc.).

(10) When the value of f5 is about 19, which is lower in the setting range, and about 250, which is close to the upper limit, the stress relaxation characteristics are slightly deteriorated (see alloys Nos. 13 and 15).

(11) When Co and Fe are contained, the average crystal grain size becomes smaller, thereby increasing the tensile strength and the proof strength. However, the elongation is low and the bending workability is slightly poor (see Alloys No. 22 and 123).

(12) Even when the conditions of the recovery heat treatment are annealed under the condition corresponding to Sn plating, the tensile strength, the proof stress, the stress relaxation characteristics, the bending strength, and the tensile strength are substantially equal to those of the copper alloy material produced under the conditions of the recovery heat treatment before the recovery heat treatment (See Test Nos. T3 to T6, T12 to T14, T19 to T22, T28 to 30, etc.).

(13) Even when the final heat treatment is carried out by batch annealing at 470 占 폚 for 4 hours or at 480 占 폚 for 4 hours, the stress relaxation properties are slightly inferior to those at high temperature for short time annealing, but tensile strength, (See Test Nos. T1, T2, T11, T12, T15, T16, T102, T103, and the like) regarding corrosion resistance, elongation, and stress corrosion cracking resistance.

Industrial availability

The copper alloy sheet of the present invention is excellent in stress corrosion cracking resistance, stress relaxation characteristics, high strength, good solder wettability, and excellent balance of strength, bending workability, stress relaxation property and effective conductivity. Thus, the copper alloy sheet of the present invention can be suitably applied to connectors, terminals, as well as components for electrical and electronic components such as relays, springs, switches, semiconductor applications, and lead frames.

Claims (11)

4 to 14 mass% of Zn, 0.1 to 1 mass% of Sn, 0.005 to 0.08 mass% of P, and 1.0 to 2.4 mass% of Ni, the balance being Cu and inevitable impurities, , The content [Zn] mass%, the content Sn [Sn], the content P [P] and the content Ni [Ni]
7? [Zn] + 3 x [Sn] + 2 x [Ni]? 18,
0? [Zn] -0.3 x [Sn] -1.8 x [Ni]? 11,
0.3? (3 x [Ni] + 0.5 x [Sn]) / [Zn]? 1.6,
1.8? [Ni] / [Sn]? 10,
16? [Ni] / [P]? 250
Lt; / RTI >
An average crystal grain size of 2 to 9 mu m,
The average particle diameter of the precipitate having a circular or elliptical shape is 3 to 75 nm or the ratio of the number of precipitates having a particle diameter of 3 to 75 nm in the precipitate is 70%
The conductivity is 24% IACS or more,
And a stress relaxation rate at 25O < 0 > C and 1000 hours at 25O < 0 > C as an internal stress relaxation property. Wherein the alloy contains 4 to 12 mass% of Zn, 0.1 to 0.9 mass% of Sn, 0.008 to 0.07 mass% of P, and 1.05 to 2.2 mass% of Ni, the balance being Cu and inevitable impurities,
The content of Zn [Zn], the content of Sn [Sn], the content of P [P], and the content of Ni [Ni]
7? [Zn] + 3 x [Sn] + 2 x [Ni]? 16,
0? [Zn] -0.3 x [Sn] -1.8 x [Ni]? 9,
0.3? (3 x [Ni] + 0.5 x [Sn]) / [Zn]? 1.3,
2? [Ni] / [Sn]? 8,
18? [Ni] / [P]? 180
Lt; / RTI >
An average crystal grain size of 2 to 9 mu m,
Wherein the average particle diameter of the precipitate having a circular or elliptical shape is 3 to 60 nm or the ratio of the number of precipitates having a particle diameter of 3 to 60 nm in the precipitate is 70%
The conductivity is greater than 26% IACS,
Wherein the stress relaxation property is not more than 23% at 150 DEG C and 1000 hours as the stress relaxation property. The method according to claim 1 or 2,
Also, at least one or more selected from Al, Fe, Co, Mg, Mn, Ti, Zr, Cr, Si, Sb, As, Pb and rare earth elements are contained in an amount of 0.0005 mass% By mass, more preferably 0.0005% by mass or more and 0.2% by mass or less in total. The method according to claim 1 or 2,
When the electric conductivity at C (% IACS) and the effective stress at 150 DEG C for 1000 hours is Pw (N / mm < ² >),
Pw? 300,
Pw 占 (C / 100) ^1/2? 190
Lt; / RTI >
The ratio of yield strength YS _{of 90} in a direction forming a 90 ° to the rolling direction and a proof stress YS ₀ for forming the zero degree direction to the rolling direction, into YS ₉₀ / YS is _0, 0.95≤YS ₉₀ / YS range of ₀ ≤1.07 Wherein the copper alloy plate is a copper alloy plate. The method according to claim 1 or 2,
A copper alloy plate characterized by being used for electronic and electronic parts. The method according to claim 1 or 2,
A connector, a terminal, a relay, a switch, or a semiconductor. A process for producing a copper alloy sheet for producing a copper alloy sheet according to claim 1 or 2,
A hot rolling step, a cold rolling step, a recrystallization heat treatment step, and a finish cold rolling step in this order,
The cold working ratio in the cold rolling step is 55% or more,
Wherein the recrystallization heat treatment step comprises a heating step of heating the copper alloy material after cold rolling to a predetermined temperature by using a continuous heat treatment furnace, a holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step, And a cooling step of cooling the copper alloy material to a predetermined temperature after the maintaining step, wherein in the recrystallization heat treatment step, the maximum reaching temperature of the copper alloy material is set to Tmax (占 폚) (Tm (min)) in the temperature range from a temperature lower than 50 deg. C to a maximum attained temperature,
560? Tmax? 790,
0.04? Tm? 1.0,
520? It1 = (Tmax-30 占 tm-1 ^/2 )? 690
And the cooling is performed under the condition of 5 ° C / second or more in a temperature range from a temperature 50 ° C lower than the maximum attained temperature to 400 ° C in the recrystallization heat treatment process. A process for producing a copper alloy sheet for producing a copper alloy sheet according to claim 3,
A hot rolling step, a cold rolling step, a recrystallization heat treatment step, and a finish cold rolling step in this order,
The cold working ratio in the cold rolling step is 55% or more,
Wherein the recrystallization heat treatment step comprises a heating step of heating the copper alloy material after cold rolling to a predetermined temperature by using a continuous heat treatment furnace, a holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step, And a cooling step of cooling the copper alloy material to a predetermined temperature after the maintaining step, wherein in the recrystallization heat treatment step, the maximum reaching temperature of the copper alloy material is set to Tmax (占 폚) (Tm (min)) in the temperature range from a temperature lower than 50 deg. C to a maximum attained temperature,
560? Tmax? 790,
0.04? Tm? 1.0,
520? It1 = (Tmax-30 占 tm-1 ^/2 )? 690
And the cooling is performed under the condition of 5 ° C / second or more in a temperature range from a temperature 50 ° C lower than the maximum attained temperature to 400 ° C in the recrystallization heat treatment process. The method of claim 7,
And a recovery heat treatment step performed after the finish cold rolling step,
Wherein the recovery heat treatment step comprises a heating step of heating the copper alloy material after the final cold rolling to a predetermined temperature, a holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step, And a cooling step of cooling the material to a predetermined temperature, wherein a maximum reaching temperature of the copper alloy material is Tmax2 (占 폚), and a temperature range from a temperature 50 占 폚 lower than the maximum reaching temperature of the copper alloy material to a maximum reaching temperature (Tm2 (min)),
150? Tmax2? 580,
0.02? Tm2? 100,
120? It2 = (Tmax2-25? Tm2? ^1/2 )? 390
Wherein the copper alloy plate is made of a metal. A method of manufacturing a copper alloy plate according to claim 1 or 2,
A first step of performing a cold rolling step and an annealing step which are performed in pairs without hot working,
After the first step,
(a1) a combination of a cold rolling process and a recrystallization heat treatment process, and
(a2) a second step of performing either or both of a final cold rolling step, which is a final cold rolling step carried out during the manufacturing step, and a combination of a recovery heat treatment step,
The cold working ratio in the cold rolling step before the recrystallization heat treatment step is 55% or more,
In the recrystallization heat treatment step,
(b1) a heating step of heating the copper alloy material after cold rolling to a predetermined temperature by using a continuous heat treatment furnace,
(b2) a holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step,
(b3) a cooling step of cooling the copper alloy material to a predetermined temperature after the holding step,
In the recrystallization heat treatment step, the maximum temperature reached by the copper alloy material is Tmax (占 폚), and the time during which the copper alloy material is heated and held at a temperature in a range from a temperature 50 占 폚 lower than the maximum attained temperature of the copper alloy material Is set to tm (min)
560? Tmax? 790,
0.04? Tm? 1.0,
520? It1 = (Tmax-30 占 tm-1 ^/2 )? 690
In addition,
In the recrystallization heat treatment step, is cooled at a temperature of 5 占 폚 / second or higher in a temperature range from a temperature 50 占 폚 lower than the maximum attained temperature to 400 占 폚,
(c1) the recovery heat treatment step includes a heating step of heating the copper alloy material after the final cold rolling to a predetermined temperature,
(c2) a holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step,
(c3) a cooling step of cooling the copper alloy material to a predetermined temperature after the holding step,
The time at which the copper alloy material is heated and held at a temperature ranging from a temperature lower than the maximum reaching temperature of the copper alloy material by 50 deg. C to a maximum attained temperature is set to tm2 (min), where Tmax2 At that time,
150? Tmax2? 580,
0.02? Tm2? 100,
120? It2 = (Tmax2-25? Tm2? ^1/2 )? 390
Wherein the copper alloy plate is made of a metal. A method for producing a copper alloy plate according to claim 3,
A first step of performing a cold rolling step and an annealing step which are performed in pairs without hot working,
After the first step,
(a1) a combination of a cold rolling process and a recrystallization heat treatment process, and
(a2) a second step of performing either or both of a final cold rolling step, which is a final cold rolling step carried out during the manufacturing step, and a combination of a recovery heat treatment step,
The cold working ratio in the cold rolling step before the recrystallization heat treatment step is 55% or more,
In the recrystallization heat treatment step,
(b1) a heating step of heating the copper alloy material after cold rolling to a predetermined temperature by using a continuous heat treatment furnace,
(b2) a holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step,
(b3) a cooling step of cooling the copper alloy material to a predetermined temperature after the holding step,
In the recrystallization heat treatment step, the maximum temperature reached by the copper alloy material is Tmax (占 폚), and the time during which the copper alloy material is heated and held at a temperature in a range from a temperature 50 占 폚 lower than the maximum attained temperature of the copper alloy material Is set to tm (min)
560? Tmax? 790,
0.04? Tm? 1.0,
520? It1 = (Tmax-30 占 tm-1 ^/2 )? 690
In addition,
In the recrystallization heat treatment step, is cooled at a temperature of 5 占 폚 / second or higher in a temperature range from a temperature 50 占 폚 lower than the maximum attained temperature to 400 占 폚,
(c1) the recovery heat treatment step includes a heating step of heating the copper alloy material after the final cold rolling to a predetermined temperature,
(c2) a holding step of holding the copper alloy material at a predetermined temperature for a predetermined time after the heating step,
(c3) a cooling step of cooling the copper alloy material to a predetermined temperature after the holding step,
The time at which the copper alloy material is heated and held at a temperature ranging from a temperature lower than the maximum reaching temperature of the copper alloy material by 50 deg. C to a maximum attained temperature is set to tm2 (min), where Tmax2 At that time,
150? Tmax2? 580,
0.02? Tm2? 100,
120? It2 = (Tmax2-25? Tm2? ^1/2 )? 390
Wherein the copper alloy plate is made of a metal.