JP7218270B2 - Copper alloy rolled sheet and quality judgment method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a copper alloy rolled sheet having strength, stress relaxation resistance and bending workability, and a method for judging the quality of the copper alloy rolled sheet.

Copper alloy rolled sheets used for terminals of automotive connectors and the like must have strength, bending workability, stress relaxation resistance and electrical conductivity. Of these, strength and conductivity are generally contradictory characteristics. Solid-solution-strengthened alloys with added elements have been used.
On the other hand, inhomogeneous parts inside the material, such as coarse precipitates, grain boundaries, grain boundary precipitates, and non-precipitated zones, have an adverse effect on bending workability and stress relaxation resistance. It was an issue. For example, in Patent Document 1, by distributing 20 or more precipitates with a diameter of 5 nm to 60 nm in a field of view of 500 nm × 500 nm in a transmission electron microscope photograph, press punchability, bending workability, and resistance of a copper alloy rolled plate are obtained. Techniques for improving stress relaxation properties have been demonstrated.

JP 2006-342389 A

In Patent Document 1, a copper alloy rolled sheet having excellent properties is specified by a microstructure observed with a transmission electron microscope. However, in order to observe a fine structure with a transmission electron microscope, a thin film sample processed as thin as about 100 nm is required, and there is a problem that it takes at least several days to obtain a single transmission electron microscope image. In addition, the size of a thin film sample is one billionth of the size of an industrial product, and transmission electron microscopes have the problem that only local information can be obtained. Furthermore, the transmission electron microscope itself also has the problem that it can only be installed in a special vibration-isolated and demagnetized environment.

An object of the present invention is to specify a copper alloy rolled sheet having strength, stress relaxation resistance and bending workability by simple means without using a transmission electron microscope and a thin film sample.

The copper alloy rolled sheet according to the present invention contains Ni: 0.7 to 2% by mass, Si: 0.6% by mass or less, Sn: 0.05 to 1.5% by mass, P: 0.1% by mass or less, It has a composition containing Zn: 1.2% by mass or less, Fe: 0.1% by mass or less, the balance being substantially Cu and unavoidable impurities, and satisfying all of the following (1) to (3).
(1) The resonance elastic modulus E0 measured at room temperature and the resonance elastic modulus E1 measured after heating from room temperature to the recrystallization temperature or higher and 550° C. or lower and then cooling to room temperature again are ₀ ≦E1−E0≦ ₀ . 2 (unit: GPa).
(2) When the internal friction is measured in the process of increasing the temperature from room temperature to 300 ° C. or higher, the value Q _max1 ⁻¹ obtained by subtracting the minimum value from the maximum value of the measured internal friction in the range from room temperature to 300 ° C. is 0.004 or less.
(3) When the internal friction was measured in the process of heating from room temperature to a temperature equal to or higher than the recrystallization temperature and then cooling to room temperature, the minimum value was subtracted from the maximum value of the measured internal friction values in the range from 300 ° C. to room temperature. The value Q _max2 ⁻¹ is less than or equal to 0.004.

When the resonance elastic modulus and internal friction of the copper alloy rolled sheet having the above composition satisfy the above conditions (1) to (3), the copper alloy rolled sheet has high strength, excellent stress relaxation resistance, and bending workability. do. In Patent Document 1, a copper alloy rolled sheet having excellent properties is specified by a microstructure observed with a transmission electron microscope, but in the present invention, a thin film sample and a transmission It is possible to solve the above problems when using an electron microscope.
The above conditions (1) to (3) can be used to determine the quality of the copper alloy rolled sheet having the above alloy composition. The above conditions (1) to (3) reflect the microstructure of the copper alloy rolled sheet, and the copper alloy rolled sheet having the above alloy composition is excellent when all the above conditions (1) to (3) are satisfied. If any one of them is not satisfied, any one of the characteristics is inferior. Measurement of the resonance modulus and internal friction of a copper alloy rolled sheet can be carried out easily in a much shorter period of time than directly observing the microstructure using a thin film sample and a transmission electron microscope.

Example No. 2 are scanning electron micrographs before and after heating (heating to 550° C. and cooling after heating to 550° C. to measure resonance elastic modulus) of No. 2. FIG. The photo on the left is before heating, and the photo on the right is after cooling. Example No. 1 shows the measured values of resonance elastic modulus and internal friction measured during the heating process and cooling process of No. 1. Example No. 2 shows measured values of resonance elastic modulus and internal friction measured during the heating process and cooling process of No. 2. Example No. 4 shows the measured values of the resonance elastic modulus and the internal friction measured during the heating process and the cooling process of No. 4. Example No. 9 shows the measured values of resonance elastic modulus and internal friction measured in the heating process and cooling process of No. 9. Example No. 2 and No. 4 is a scanning electron micrograph before heating. The photo on the left is No. 2, the photo on the right is No. 4. Example No. 14 (same as No. 1) is a transmission electron micrograph.

Hereinafter, the copper alloy rolled sheet according to the present invention will be described in more detail. First, the alloy composition of the copper alloy rolled sheet will be described.
Ni forms a solid solution in the copper alloy, suppresses the diffusion of Sn and P that exert viscous resistance on dislocations in the copper alloy, and has the effect of improving stress relaxation resistance. In addition, Ni forms precipitates between Si and P, and contributes to improving the strength of the copper alloy. In order to exhibit this effect, Ni must be added in an amount of 0.7% by mass or more. On the other hand, when Ni is added in excess of 2% by mass, Ni—Si grain boundary precipitates are formed that reduce bendability, resulting in Q _max1 ⁻¹ or Q _max2 ⁻¹ exceeding 0.004. Therefore, the Ni content should be 0.7 to 2% by mass.

Si has the effect of forming fine precipitates with Ni to improve the strength of the copper alloy. However, when Si is added in _excess of 0.6% by mass, the amount of solid-solution Si increases, and this solid-solution Si is internally oxidized by heat treatment during the manufacturing process. The stress relaxation properties of the alloy deteriorate. Therefore, the Si content should be 0.6% by mass or less. P has the same effect as Si (improves the strength of the copper alloy by forming fine precipitates with Ni), so when P is added, Si is not added (content 0% by mass). But I don't mind.

Sn dissolves in the copper alloy and has the effect of improving the strength and stress relaxation resistance of the copper alloy. In order to exhibit this effect, Sn must be added in an amount of 0.05% by mass or more. On the other hand, when Sn is added in an amount exceeding 1.5% by mass, the strength becomes excessive and the elongation decreases, resulting in a decrease in bending workability when the steel is strengthened by work hardening (rolling). Therefore, the Sn content should be 0.05 to 1.5% by mass.
P has the effect of forming fine precipitates with Ni to improve the strength of the copper alloy. However, when P is added in excess of 0.1% by mass, a Cu—P intermetallic compound with a low melting point is formed during melting and casting, and the hot-rolled material cracks during hot rolling. Therefore, the P content is set to 0.1% by mass or less. Since P has the same action as Si, when Si is added to the copper alloy, P may not be added (content of 0% by mass).

Zn has the effect of preventing peeling of solder plating and tin plating applied to the copper alloy over time and improving solder wettability. The above effect of Zn is remarkable when the copper alloy contains Si. When the copper alloy contains Si, Zn suppresses the internal oxidation of Si during heat treatment, thereby improving the solder wettability of the copper alloy and also improving the stress relaxation characteristics. On the other hand, since Zn lowers electrical conductivity, the Zn content is limited to 1.2% by mass or less. When the copper alloy does not contain Si, Zn may not be added (0% content).
Fe has the effect of suppressing the coarsening of crystal grains of the copper alloy in the heat treatment process at a substantial temperature of 600° C. or higher during production, and improving the bending workability of the copper alloy. However, when the Fe content exceeds 0.1% by mass, coarse Fe-based precipitates that do not redissolve even in a heat treatment process at a substance temperature of 600 ° C. or higher are generated, E1-E0 exceeds ₂ GPa, or Q _max1 ^-1 or Q _max2 ^-1 is greater than 0.004. Therefore, the Fe content is set to 0.1% by mass or less. Since Ni—Si-based precipitates also have the same effect of suppressing grain coarsening as Fe, when Si is added to the copper alloy, Fe may not be added (content of 0% by mass).

The copper alloy rolled sheet according to the present invention satisfies the above conditions (1) to (3).
The condition of (1) is that the resonance elastic modulus E0 measured at room temperature and the resonance elastic modulus E1 measured by heating from room temperature to a temperature range from the recrystallization temperature to 550 ° C. and then cooling to room temperature again are ₀ ≤ It has a relationship of E1−E ₀ ≦2 (unit: GPa).
From the same test piece taken from a copper alloy plate, in order to measure the elastic modulus E ₀ at room temperature and the elastic modulus E ₁ when the temperature is raised from room temperature to the above temperature range and then cooled to room temperature again, in the present invention, a tensile test The method of measuring the elastic modulus from the slope of the stress-strain curve using a piece cannot be used. In the present invention, resonance elastic moduli (E ₀ , E ₁ ) calculated from the resonance frequency of the test piece which is vibrated by externally driven vibration are used.

Resonance elastic modulus E is the magnitude of the elastic modulus due to the copper atomic force, α is the contribution to the elastic modulus due to additional elements and strengthening mechanisms (precipitation, etc.), and β is the contribution to the elastic modulus due to the crystal structure and crystal orientation. is expressed as E=α+β+γ-δ, where γ is the elastic modulus loss due to mobile dislocations and δ is the elastic modulus loss.
Since α (elastic modulus due to copper atomic force) is due to the interaction between copper atoms, there is no significant difference even after cycles of temperature rise and cooling.
β (contribution to elastic modulus due to added elements and strengthening mechanism) also varies after heating/cooling cycles unless the precipitates that contribute to strengthening redissolve and disappear during the temperature rise/cooling cycle. do not have.

γ (contribution to elastic modulus by crystal structure and crystal orientation) does not change after heating/cooling cycles unless the crystal structure and crystal orientation of the copper alloy plate change during the temperature rise. In copper alloys with few or no grain boundary pinning precipitates, such as phosphor bronze and brass, this contribution is lost when recrystallization occurs during a temperature rise as the grains change. In addition, in the case where the structure of the copper alloy consists of worked structures and high-angle grain boundaries, this contribution is lost when the structure changes to low-angle grain boundaries due to recrystallization. On the other hand, when the structure of the copper alloy sheet has already become a low-angle grain boundary structure due to the heat treatment and precipitated grains pinning the grain boundaries exist, the recrystallization hardly changes the structure state. In this case, even if the temperature of the copper alloy plate exceeds the recrystallization temperature, this contribution hardly disappears. FIG. 1 shows No. 1 of the embodiment described later. 2 are scanning electron micrographs before and after heating (heating to 550° C. and cooling after heating to 550° C. to measure resonance elastic modulus) of No. 2. FIG. The observation surface is a cross section in a direction parallel to the rolling direction. The photograph on the left side of FIG. 1 is the one before the temperature rise, and the photograph on the right side is the one after the temperature rise.
δ (elastic modulus loss due to mobile dislocations) disappears due to dislocation rearrangement and density reduction occurring at recovery temperature (higher than room temperature and lower than recrystallization temperature).

The difference (E ₁ −E ₀ ) between the resonance elastic moduli E ₀ and E ₁ before and after the temperature rise of the copper alloy plate represents the magnitude of contribution of γ and δ to the resonance elastic modulus of the copper alloy plate, and its value is This reflects the microstructure of the copper alloy sheet.
In order to detect the contribution of δ to the resonance elastic modulus, the copper alloy plate must be heated to the recovery temperature or higher. In the copper alloy sheet having the alloy composition according to the present invention, the recovery temperature is generally less than 400°C, so the copper alloy sheet must be heated to 400°C or higher in order to detect the contribution of δ. Further, in order to detect the contribution of γ to the resonance modulus, it is necessary to heat the copper alloy plate to the recrystallization temperature or higher. In the copper alloy sheet having the alloy composition according to the present invention, the recrystallization temperature is approximately 470° C. or higher. On the other hand, when the temperature rise exceeds 550° C., it becomes the re-dissolution temperature of the precipitates that contribute to the strength of the copper alloy sheet having the alloy composition according to the present invention. When the temperature of the copper alloy plate rises above the resolution temperature, the contribution of β to the resonance elastic modulus cannot be ignored. From the above, in the measurement of the resonance elastic moduli E ₀ and E ₁ , the heating temperature should be above the recrystallization temperature and below 550°C.

When the difference (E ₁ −E ₀ ) between the resonance elastic moduli E ₀ and E ₁ is less than 0 GPa (E ₁ −E ₀ <0), the copper alloy plate (specimen) is regenerated when heated to the recrystallization temperature or higher. Crystal softening occurs, and such a copper alloy plate cannot be used as a terminal material that requires stress relaxation resistance. On the other hand, the phenomenon that the difference between the resonance elastic moduli E0 and E1 (E ₁ −E ₀ ) is greater than 2 GPa is caused by coarse precipitates present in the copper alloy plate (diameters of about 60 nm to 1 μm do not contribute to the improvement of strength characteristics). This is a phenomenon that occurs because the dislocations that have been dammed up in the lattice undergo rearrangement and density reduction during the thermal activation process during heating. Therefore, the difference (E ₁ −E ₀ ) between the resonance elastic moduli E ₀ and E1 must be within the range of 0 to 2 GPa (0≦E ₁ −E ₀ ≦2).
_Dislocation loops generated around coarse precipitates and mobile dislocations accumulated by being blocked by these may remain if the temperature rise is _less than the recrystallization temperature. 0≦E ₁ −E ₀ ≦2 in some cases. When the temperature of the copper alloy plate is raised to the recrystallization temperature or higher, these mobile dislocation lines disappear, so the difference between E ₀ and E ₁ (E ₁ −E ₀ ) becomes larger than 2 GPa, and the above coarse precipitates can more accurately determine the existence of

The condition of (2) is the maximum value of the internal friction measured in the range from room temperature to 300 ° C. when the internal friction is measured in the process of raising the temperature of the copper alloy plate (test piece) from room temperature to 300 ° C. or higher. The value Q _max1 ^-1 obtained by subtracting the minimum value from the value is 0.004 or less.
When the resonance elastic modulus of the copper alloy plate is measured, the resonance begins to attenuate from the moment the external drive is cut off. The internal friction is the ratio of the heights of adjacent peaks of the resonant vibration waveform at this time. The internal friction of the copper alloy plate at room temperature is about 0.0001 to 0.001. In other words, the resonance vibration is very slow to damp, but the internal friction increases if there are inhomogeneous structures, coarse precipitates, mobile dislocations, etc. that are not synchronized with the resonance vibration in the copper alloy plate. When measuring the resonance frequency while changing the temperature of the copper alloy plate, the resonance frequency decreases as the temperature rises, so measuring the internal friction while increasing the temperature is equivalent to sweeping at a lower frequency. be.

The internal friction from room temperature to 300°C reflects the inhomogeneity, defects, mobile dislocations, and precipitates in the copper alloy plate. It increases like a mountain or has a sharp peak. When the temperature of the copper alloy plate exceeds 300° C., the viscous displacement of the grain boundaries causes a rapid increase in internal friction, and the details inside the copper alloy plate cannot be discerned. On the other hand, the overall measured value of internal friction from room temperature to 300° C. is affected by the thickness of the plate to be vibrated in resonance, the atmosphere, and other test factors, and each measured value fluctuates. Therefore, the difference Q _max1 ⁻¹ between the maximum and minimum values of internal friction measured in the range from room temperature to 300° C. is the internal friction reflecting the microstructure inside the copper alloy plate. If this value exceeds 0.004, bending workability and stress relaxation resistance deteriorate, making the copper alloy sheet unsuitable for terminals.

The condition of (3) is that when the internal friction is measured in the process of heating the copper alloy plate (test piece) from room temperature to the recrystallization temperature or higher and then cooling it again to room temperature, the internal friction in the range from 300 ° C. to room temperature The value Q _max2 ⁻¹ obtained by subtracting the minimum value from the maximum value of the measured friction values is 0.004 or less.
Under the condition (2) above, the internal friction is measured during heating from room temperature to 300°C. Therefore, the copper alloy plate at the time of measurement has the strength required as a copper alloy for terminals, has a high dislocation density, and is in a state in which dislocations are entangled with each other. If internal friction is measured in this state, inhomogeneities and defects inside the material are fixed by intertwined dislocations, and the measured internal friction value does not reflect the inhomogeneities and defects (i.e. , the peaks and peaks of internal friction associated with temperature rise are shielded).

In order to compensate for this, condition (3) is added. Under the condition (3), the internal friction is measured in the cooling process (300° C. or less) after softening the copper alloy plate by heating it to a temperature equal to or higher than the recrystallization temperature. With this measurement method, the internal friction reflects the inhomogeneity and defects inside the material, so that the peaks and peaks of the internal friction caused by the inhomogeneity and defects in the material can be overlooked. When the difference Q _max2 ⁻¹ between the maximum and minimum values of internal friction measured in the cooling process from 300° C. to room temperature exceeds 0.004, the bendability and stress relaxation resistance of the copper alloy plate are reduced. It deteriorates and is unsuitable as a copper alloy for terminals.

In the measurement of the internal friction (Q _max1 ⁻¹ , Q _max2 ⁻¹ ), as in the measurement of the resonance elastic modulus (E ₀ , E ₁ ), the upper limit of the temperature rise is above the recrystallization temperature and below 550 ° C. A range is desirable. As will be described in the examples below, the resonance elastic modulus (E ₀ , E ₁ ) and internal friction (Q _max1 ⁻¹ , Q _max2 ⁻¹ ) of the copper alloy plate were measured by intermittently raising the same test piece. The heating and cooling process can be done simultaneously. Considering this point, it makes sense to set the upper limit of the temperature rise to the recrystallization temperature or higher and 550° C. or lower in the measurement of the internal friction (Q _max1 ⁻¹ , Q _max2 ⁻¹ ).
When the temperature of the test piece is intermittently raised, an isothermal step in which the test piece is maintained at a constant temperature and a heating step in which the temperature is raised until the test piece reaches a target temperature of from room temperature to the recrystallization temperature or higher and 550 ° C. or lower is repeated. Similarly, when the test piece is intermittently cooled, the isothermal step of maintaining the test piece at a constant temperature and the cooling step of decreasing the temperature are repeated until the test piece reaches room temperature from the target temperature. Measurements of resonance modulus and internal friction are made in the isothermal step. The temperature increase rate in the temperature increase step is not particularly limited, but may be, for example, about 10° C./1 minute to 10° C./7 minutes. The cooling step is also not particularly limited, but may be discharge cooling (cooling rate: about 10° C./5 minutes).

The copper alloy rolled sheet according to the present invention can be produced, for example, by the following steps.
After the copper alloy ingot is homogenized, it is subjected to hot rolling and cold rolling, followed by continuous annealing for a short time, followed by precipitation annealing, or final cold rolling and low temperature annealing for a short time. . In each step described above, for example, the following conditions are selected.
The homogenization treatment is carried out at a holding temperature of 800-1000° C. for a holding time of 0.5-4 hours. The subsequent hot rolling is maintained at a temperature of 600° C. or more until the end, and after the end is water-cooled or allowed to cool. Continuous annealing after cold rolling is for solution treatment, and the holding temperature is 600° C. or higher and the holding time is several tens of seconds. Precipitation annealing is carried out at a holding temperature of 450 to 550° C. for several hours. The working ratio of the final cold rolling is about 30 to 80%, and the low temperature annealing is performed at a holding temperature of 250 to 450° C. and a holding time of 20 to 40 seconds.

In the above manufacturing method, the copper alloy is subjected to a heat treatment at a substantial temperature of 600° C. or higher two or more times. The first is a heat treatment to eliminate the inhomogeneous ingot structure and realize a single α-phase state in which all elements are dissolved, and mainly applies to the heating process of hot rolling (including homogenization treatment). . The second heat treatment is to cancel the worked structure formed by cold rolling from the hot-rolled sheet to the product thickness or a thickness close to it, and to realize an α single-phase state in which all elements are dissolved. , mainly the solution treatment process. The copper alloy defined in the present invention has a recrystallization temperature in the range of 450 ° C. to 550 ° C., and in order to decompose Ni-Si, Ni-P compounds, etc. and redissolve, hot rolling and continuous annealing processes , a substance temperature of 600° C. or higher is required. If the substance temperature is lower than 600° C., coarse precipitates that degrade the non-uniform structure of the copper alloy or the bending workability remain.
According to this production method, a copper alloy rolled sheet having the composition specified in the present invention and satisfying the conditions (1) to (3) can be produced. This copper alloy rolled sheet has a yield strength of 500 MPa or more, has excellent bending workability of R / t = 0.5 or more (R: bending radius, t: plate thickness), and after 150 ° C. × 1000 hours It has an excellent stress relaxation rate of 15% or less. Moreover, it has sufficient electrical conductivity for terminals.

Next, examples of the copper alloy rolled sheet according to the present invention will be described.
Copper alloys were melted in a Kryptor furnace in air under a charcoal coating to obtain 45 mm thick ingots (Nos. 1-10) having the alloy compositions shown in Table 1. This ingot was homogenized under the conditions shown in Table 1, hot rolled to a thickness of 15 mm, and quenched at 800° C. or higher (water cooling). Both sides of this hot-rolled material were chamfered by 1 mm each to a thickness of 13 mm, and then subjected to the process shown in Table 1 (process after hot rolling). 1 to 14 product sheets (copper alloy rolled sheets) were obtained. The plate thickness of each product plate is 0.25 mm. In addition, No. 11 and 12 are Nos. No. 1 divided cold-rolled material (1 t). 13 is No. 2 split cold-rolled stock (0.5t). No. 14 is No. No. 1 product plate was used.

Using the obtained product sheet (copper alloy rolled material) as a test material, the resonance elastic modulus, internal friction, conductivity, hardness, yield strength, stress relaxation resistance (stress relaxation rate) and bending workability were measured in the following manner. measured by However, no. For No. 14, the microstructure was observed with a transmission electron microscope without measuring the resonance modulus and internal friction. Table 2 shows the above results. Structural inhomogeneity, coarse precipitates, mobile dislocation groups, and the resulting Bausinger effect generated in the material are more strongly affected in the direction parallel to rolling (LD direction) than in the direction perpendicular to rolling (TD direction). receive. For this reason, the LD direction was the longitudinal direction of the test piece for measuring the yield strength and stress relaxation rate. On the other hand, since the structural inhomogeneity has a distribution extending in the rolling direction, bending is more strongly affected in the TD direction than in the LD direction. For this reason, a so-called badway bending was performed on a test piece for bending measurement so that the TD direction was the longitudinal direction.

ここでＬは試験片の長さ（単位：ｍｍ）、ρは密度（ｇ／ｃｍ^３）、ｔは板厚（単位：ｍｍ）である。
内部摩擦は共振の振動エネルギーの減衰率であり、共振弾性率と同時測定できる。試験片が共振している状態から加振を停止すると、試験片は共振周波数で徐々に減衰する。この減衰を１周期ごとに測定し対数減衰率として計算する。 (Resonant elastic modulus and internal friction)
An elastic modulus and internal friction measuring device JE-HT manufactured by Technoplus Japan was used to measure the resonance modulus and internal friction. A test piece with a width of 10 mm, a thickness of 0.25 mm, and a length of 45 mm was taken from each test material and placed so that the plate surface was horizontal. Be suspended. Heating of the specimen and measurement of resonance modulus and internal friction are performed in a metal chamber in which nitrogen gas is circulated. A static induction transducer installed on the underside of the test piece induces bending vibration, and an adjacent non-contact sensor monitors the vibration of the test piece. A thermocouple is installed just before the test piece, and this is measured as the actual temperature of the test piece. At this time, the resonance frequency f (unit: Hz) and the elastic modulus E (unit: GPa) have the following relationship.

Here, L is the length of the test piece (unit: mm), ρ is the density (g/cm ³ ), and t is the plate thickness (unit: mm).
Internal friction is the damping rate of resonance vibration energy and can be measured simultaneously with the resonance elastic modulus. When the vibration is stopped while the test piece is resonating, the test piece gradually attenuates at the resonance frequency. This decay is measured every cycle and calculated as a logarithmic decay rate.

The test piece placed in the chamber was intermittently heated from room temperature (30° C.) to a temperature exceeding the recrystallization temperature (550° C. or less) at a constant heating rate. In this temperature rising process, the resonance modulus and internal friction were first measured at room temperature, and then the resonance modulus and internal friction were measured each time the temperature was increased by 10°C. The time required for one measurement was 7 minutes, three measurements were performed at each measurement temperature, and the test piece was maintained at the measurement temperature during the measurements. When the measurement was completed at each measurement temperature, the test piece was heated to the next measurement temperature (+10°C) at a heating rate of 10°C/1 minute. After intermittently raising the temperature and measuring until the test piece exceeded the recrystallization temperature and reached the target temperature, it was immediately cooled intermittently to room temperature (30°C) at a constant cooling rate. During this cooling process, the resonance modulus and internal friction were also measured every 10°C of cooling. The time required for one measurement is 7 minutes, three measurements are performed at each measurement temperature, the test piece is maintained at the measurement temperature during the measurement, and when the measurement is completed, the next measurement temperature ( −10° C.), the test piece was allowed to cool together with the chamber. The cooling rate at that time was 10° C./5 minutes.

Comparing the three measurements made at each measurement temperature, No. In all test pieces 1 to 13 and at all measurement temperatures, the difference between the maximum and minimum values of resonance elastic modulus was within 0.2, and the difference in internal friction was within 0.0002. The values of resonance modulus and internal friction at each measurement temperature were the average of three measurements.
From the resonance modulus _E0 measured at room temperature in the process of increasing the temperature from room temperature and the resonance modulus E1 measured at room temperature in the process of cooling down to room temperature, the difference between the resonance moduli _E0 and E1 ( _E1 - E ₀ ) was calculated. The difference Q _max1 ⁻¹ was calculated from the maximum and minimum values of the internal friction (from room temperature to 300° C.) measured during the temperature rising process from room temperature. Also, the difference Q _max2 ⁻¹ was calculated from the maximum and minimum values of internal friction (from 300° C. to room temperature) measured during cooling to room temperature.

Figures 2 to 5 show No. 1 during the heating process and cooling process. 1, 2, 4, and 9 illustrate graphs of resonance moduli and internal friction measurements. The vertical axis is the resonance modulus and the internal friction, and the horizontal axis is the temperature.
No. 1 (FIG. ₂ ) has a resonance modulus E0 of _128.59 GPa measured at room temperature during the heating process, and a resonance modulus E1 of 130.00 GPa measured at room temperature during the cooling process. , E1 is _{1.41 GPa} . The maximum value of internal friction (from room temperature to 300°C) measured during the heating process is 0.00299 (280°C), the minimum value is 0.00169 (30°C), and the difference Q _max1 ^-1 is 0.00130. is. The maximum value of internal friction (from 300°C to room temperature) measured during the cooling process is 0.00345 (300°C), the minimum value is 0.00170 (300°C), and the difference Q _max2 ^-1 is 0.00175. be.

No. 2 (FIG. 3) has a resonance modulus E0 of _128.71 GPa measured at room temperature during the heating process, and a resonance modulus E1 of _129.00 GPa measured at room temperature during the cooling process. , E1 is _{0.29 GPa} . The maximum value of internal friction (from room temperature to 300°C) measured during the heating process is 0.00366 (80°C, 280°C), the minimum value is 0.00265 (240°C), and the difference Q _max1 ^-1 is 0.00101. The maximum value of internal friction (from 300°C to room temperature) measured during the cooling process is 0.00394 (300°C), the minimum value is 0.00229 (60°C), and the difference Q _max2 ^-1 is 0.00165. be.

No. 4 (FIG. 4) has a resonance elastic modulus E0 of _127.48 GPa measured at room temperature during the heating process, and a resonance elastic modulus E1 of _130.32 GPa measured at room temperature during the cooling process. , E1 is _{2.84 GPa} . The maximum value of internal friction (from room temperature to 300°C) measured during the heating process is 0.00596 (290°C), the minimum value is 0.00180 (40°C), and the difference Q _max1 ^-1 is 0.00416. is. The maximum value of internal friction (from 300 ° C to room temperature) measured during the cooling process is 0.00378 (300 ° C), the minimum value is 0.00184 (50 ° C, 30 ° C), and the difference Q _max2 ^-1 is 0 .00194.

No. 9 (FIG. 5) has a resonance modulus E0 of _112.65 GPa measured at room temperature during the heating process, and a resonance modulus E1 of _109.43 GPa measured at room temperature during the cooling process. , E1 difference (E ₁ −E ₀ ) is −3.22 GPa. The maximum value of internal friction (from room temperature to 300°C) measured during the heating process is 0.00778 (300°C), the minimum value is 0.00199 (40°C), and the difference Q _max1 ^-1 is 0.00579. is. The maximum value of internal friction (from 300°C to room temperature) measured during the cooling process is 0.00787 (300°C), the minimum value is 0.00200 (30°C), and the difference Q _max2 ^-1 is 0.00587. be.

(conductivity)
The conductivity was measured by a four-probe method using a double bridge in conformity with the method for measuring the conductivity of non-ferrous metal materials specified in JISH0505.
(Hardness)
The hardness was measured with a test load of 500 g (4.9 N) in accordance with the microhardness test method for Vickers hardness defined in JISZ2244.
(proof strength)
Yield strength was measured by machining a JIS No. 5 tensile test piece so that the longitudinal direction was the LD direction of the test material, and performing a tensile test in accordance with JISZ2241. Yield stress is the tensile strength corresponding to 0.2% permanent elongation.

(Stress relaxation rate)
The stress relaxation rate was measured using the cantilever beam method specified in the Japan Copper and Brass Association technical standard JCBAT309. A strip-shaped test piece with a width of 10 mm is cut out from the test material so that the length direction is in the LD direction, one end is fixed to a rigid test stand, and the height d (= 10 mm) is attached to the span length L of the test piece. ) to give the amount of deflection by biting the pillow block. At this time, the span length L is determined so that a surface stress corresponding to 80% of the material proof stress is applied to the test piece. After holding this in an oven at 180 ° C. for 30 hours, it was taken out, the permanent strain δ was measured when the amount of deflection d was removed, and the stress relaxation rate (RS) calculated by RS = (δ / d) × 100 was calculated. demand. Note that holding at 180° C. for 30 hours corresponds to holding at approximately 150° C. for 1000 hours when calculated using Larson-Miller parameters.

(bendability)
A test piece having a width of 10 mm and a length of 35 mm was cut from the test material such that the length direction was the TD direction of the test material. The test piece is sandwiched using a B-type bending jig for the CES-M0002 metal material W bending test specified in the Japan Copper and Brass Association technical standard JBMAT307 so that the bending line of the test piece is perpendicular to the length direction, and the load is applied. Bending was performed with a hand press of 1 ton. The R/t just before bending cracks occurred was calculated from the curvature radius R of the bent portion and the plate thickness t (=0.25 mm) of the test piece.
(Transmission electron microscope observation)
A thin film for transmission electron microscope observation was made from a sample taken from the test material by manual polishing and electrolytic thin film method (twin jet method). Using a transmission electron microscope H-800 (accelerating voltage of 200 kV) manufactured by Hitachi, Ltd., the images were photographed at a magnification of 100,000 times, and printed on high-quality photographic paper at a magnification of 1.5 times.

No. 1 and 2 have an alloy composition within the specified range of the present invention, and the difference (E ₁ −E ₀ ) between the resonance elastic moduli E ₀ and E ₁ is within the range of 0 GPa to 2 GPa. In addition, the difference Q _max1 ^-1 between the maximum and minimum values of internal friction in the heating process (room temperature → 300 ° C) and the difference Q _max2 ^-1 between the maximum and minimum values of internal friction in the cooling process (300 ° C → room temperature) are both 0.004 or less. From this measurement result, No. It is presumed that the copper alloy rolled sheets of 1 and 2 have a homogeneous microstructure with few inhomogeneous structures, coarse precipitates, and mobile dislocations blocked by coarse precipitates.
FIG. 2 and No. 2 described later. 4 is a scanning electron microscope photograph (observation surface is a cross section in a direction parallel to the rolling direction) before temperature rise of No. 4, and the photograph on the left is No. 4. 2, the photo on the right is No. 4, the observation surface is a cross section in the direction parallel to the rolling direction. No. In 2, a considerable number of fine precipitates are observed, but no coarse precipitates are observed. No. 4, relatively coarse precipitates are observed especially at grain boundaries.
And no. The copper alloy rolled sheets of 1 and 2 are excellent in yield strength, stress relaxation resistance and bending workability. In addition, No. In manufacturing processes 1 and 2, there are two heat treatment processes including hot rolling in which the steel is heated to 600° C. or higher.
No. In Nos. 1 and 2, the time required to measure the values of resonance elastic modulus and internal friction was within 50 hours, including processing of the test piece (this point is the same for Nos. 3 to 13).

On the other hand, No. 3 to 13 are the alloy composition, the difference in resonance elastic modulus (E ₁ - E ₀ ), the difference Q _max1 ^-1 between the maximum and minimum values of internal friction in the heating process (room temperature → 300 ° C.), the cooling process (300 °C to room temperature), any one or more of the difference Q _max2 ^-1 between the maximum and minimum values of internal friction is outside the scope of the present invention. For this reason, No. 3 to 13 are inferior in one or more properties of yield strength, stress relaxation resistance and bending workability.
No. No. 3, because the Ni content is insufficient. Despite undergoing the same manufacturing process as No. 1, E ₁ -E ₀ became negative, both Q _max1 ^-1 and Q _max2 ^-1 were larger than the prescribed values, and the stress relaxation rate exceeded 15%.
No. In No. 4, the Ni content was excessive, so E ₁ -E ₀ and Q _max1 ^-1 exceeded the prescribed values. From this measurement result, No. In 4, it is presumed that there are many coarse precipitates inside the copper alloy plate that do not contribute to the improvement of mechanical properties. In fact, according to the photograph on the right side of FIG. 6 (scanning electron microscope photograph of No. 4), relatively coarse precipitates are observed especially at grain boundaries. And no. 4, the stress relaxation property and bending workability were deteriorated.

No. No. 5 has an excessive Si content. Despite undergoing the same manufacturing process as No. 1, E ₁ -E ₀ and Q _max2 ^-1 exceeded the specified values, and the stress relaxation characteristics and bending workability were degraded. No. In 5, it is presumed that the excess Si causes internal oxidation during the high-temperature heat treatment process.
No. In No. 6, since the P content was excessive, cracks occurred during hot rolling. Therefore, the subsequent steps were abandoned. The grain boundary segregation of the low-melting intermetallic compound due to the excessive P content is presumed to be the cause of cracking during hot rolling.
No. In No. 7, since the Sn content was insufficient, Qmax1-1 and Qmax2-1 exceeded the specified values, and the stress relaxation characteristics were lowered. No. In No. 7, the Sn content is small, and the Sn that fixes the dislocations is considered to be insufficient.
No. No. 8 has an excessive Sn content and is inferior in bending workability. The reason why E ₁ -E ₀ , Q _max1 ⁻¹ , and Q _max2 ⁻¹ were all within the specified ranges is presumed to be that the high Sn content resulted in excellent adhesion of mobile dislocations.

No. 9 is brass (C2600) and has poor stress relaxation resistance. E ₁ -E ₀ , Q _max1 ⁻¹ and Q _max2 ⁻¹ are also all outside the specified range.
No. In No. 10, since the Fe content was excessive, E ₁ -E ₀ and Q _max2 ^-1 greatly exceeded the specified ranges, and the stress relaxation resistance and bending workability deteriorated.
No. 11 is No. 1 was produced by dividing the intermediate rolled material, and was produced to the final thickness only by rolling without performing a heat treatment process exceeding 600° C. other than hot rolling. Since the material structure is a worked structure, when the temperature is raised above the recrystallization temperature in the heating process for measuring the resonance modulus and internal friction, the worked structure transforms into a small tilt grain boundary structure, thereby It is considered that the elastic modulus contribution (γ described above) due to the processed structure disappeared, and E1-E0 became a negative value. And no. 11 does not have suitable yield strength and stress relaxation resistance properties for terminal applications. Also, No. No. 11 is presumed to contain relatively coarse precipitates generated during cooling after hot rolling because no heat treatment process exceeding 600° C. was performed other than hot rolling.
In addition, No. The samples other than No. 11 were already recrystallized once when they became product sheets. As a result, even if the recrystallization temperature was exceeded in the heating process, large-scale structural transition hardly occurred.

No. 12 is also No. The intermediate rolled material of No. 1 was divided and used, but the annealing temperature during cold rolling was less than 600 ° C., E ₁ -E ₀ , Q _max1 ^-1 , Q _max2 ^-1 were outside the specified range, and bending Poor strength and stress relaxation resistance. This is probably because the annealing temperature was low and coarse Ni--P precipitates in the material could not be dissolved again.
No. 13 is No. The intermediate rolled material No. 2 was used, but the annealing temperature during cold rolling was less than 600°C, Q _max2 ^-1 exceeded the specified range, and the bending workability and stress relaxation resistance were low.
No. 14 is No. 1 is used. No. in FIG. 14 transmission electron micrographs are shown. According to FIG. 7, there is no precipitate exceeding 60 nm in diameter in the structure, and about 90 or more precipitates with a diameter of 5 nm or more and 60 nm or less are observed within a field of view of about 500 nm×500 nm. It took about 170 hours to prepare a thin film sample from the product plate, observe it with a transmission electron microscope, and judge whether or not the fine structure was sound.

Claims (2)

Ni: 0.7 to 2% by mass, Si: 0.6% by mass or less, Sn: 0.05 to 1.5% by mass, P: 0.1% by mass or less, Zn: 1.2% by mass or less, Fe : A copper alloy rolled sheet having a composition containing 0.1% by mass or less, the balance being Cu and inevitable impurities, and satisfying all of the following (1) to (3).
(1) The resonance elastic modulus E0 measured at room temperature and the resonance elastic modulus E1 measured after heating from room temperature to the recrystallization temperature or higher and 550° C. or lower and then cooling to room temperature again are ₀ ≦E1−E0≦ ₀ . 2 (unit: GPa).
(2) When the internal friction is measured in the process of increasing the temperature from room temperature to 300 ° C. or higher, the value Q _max1 ⁻¹ obtained by subtracting the minimum value from the maximum value of the measured internal friction in the range from room temperature to 300 ° C. is 0.004 or less.
(3) When the internal friction is measured in the process of heating from room temperature to a temperature equal to or higher than the recrystallization temperature and then cooling to room temperature again, subtract the minimum value from the maximum value of the measured internal friction values in the range from 300 ° C. to room temperature. The value Q _max2 ⁻¹ is 0.004 or less. Ni: 0.7 to 2% by mass, Si: 0.6% by mass or less, Sn: 0.05 to 1.5% by mass, P: 0.1% by mass or less, Zn: 1.2% by mass or less, Fe : For a copper alloy rolled sheet having a composition containing 0.1% by mass or less and the balance consisting of Cu and unavoidable impurities, if one or more of the following (1) to (3) are not satisfied, it is determined to be unsuitable. A method for determining the quality of a copper alloy rolled sheet, characterized by:
(1) The resonance elastic modulus E0 measured at room temperature and the resonance elastic modulus E1 measured after heating from room temperature to the recrystallization temperature or higher and 550° C. or lower and then cooling to room temperature again are ₀ ≦E1−E0 ≦ ₀ . 2 (unit: GPa) .
(2) When the internal friction is measured in the process of increasing the temperature from room temperature to 300 ° C. or higher, the value Q _max1 ⁻¹ obtained by subtracting the minimum value from the maximum value of the measured internal friction in the range from room temperature to 300 ° C. is 0.004 or less .
(3) When the internal friction is measured in the process of heating from room temperature to a temperature equal to or higher than the recrystallization temperature and then cooling to room temperature again, subtract the minimum value from the maximum value of the measured internal friction values in the range from 300 ° C. to room temperature. The value Q _max2 ⁻¹ is 0.004 or less .

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