KR101377391B1 - Cu-ni-si alloy with excellent bendability - Google Patents

Abstract

0.8-4.6 mass% of Ni and 0.3-1.6 mass% of Si, and one or more of arbitrary components Sn, Zn, Fe, Co, Cr, Mg, and Mn contain 2.0 mass% or less of total amounts, and the number of the lines of the front end of a surface layer (A) A Cu-Ni-Si-based alloy bath having a high strength and excellent appearance after bending, with respect to the number of lines of the shear band in the center portion of the plate thickness, preferably the number of shear bands in the surface layer is 10/100/100 µm ² or less, The number of precipitate particles having a particle size of 1 to 10 µm of the surface layer is 1.0 × 10 ² particles / mm ² or less, and the number of particle particles having a particle diameter of 1 to 10 µm of the surface layer is 1.0 or less with respect to the number of plate thickness center portions.

Description

Cu-Ni-Si alloys with excellent bendability {CU-NI-SI ALLOY WITH EXCELLENT BENDABILITY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high strength copper alloys used for electronic materials such as lead frames and connectors, terminals for vehicle connectors, and the like. Specifically, the present invention relates to a high-strength copper alloy exhibiting excellent bendability and no bend appearance without causing wrinkles or cracks in the bend appearance after bending.

In recent years, high-density packaging has been advanced in electronic devices such as mobile phones, digital cameras, and video cameras, and in-vehicle connectors, and parts thereof have been remarkably thin and short. The material to be used also has a tendency of thinning, and the material is required to have a higher strength. In addition, the shape of the parts is also complicated, and more cases are subjected to more stringent bending processes, and even if the strength is increased, the bendability is equivalent to that of the conventional material, or the box bending and the 180-degree close bending are also reduced to reduce the plate thickness. More excellent bending workability, such as bending after a floating process and there is no crack, has been calculated | required.

Corson alloy (Cu-Ni-Si type copper alloy) which is excellent in the balance of strength, electroconductivity, and bendability is used for these electrical equipment members. In general, when the strength of the alloy is increased, the bendability is deteriorated, and the bendability is low. Thus, various improvements have been made to achieve both strength and bendability. For example, in Patent Documents 1 and 2, in a Corson alloy containing a certain amount of a specific element, the tensile strength and the bending workability, by controlling the particle diameter and number of the precipitates consisting of Ni and Si and the precipitates containing the specific element, respectively, In addition, a copper alloy having excellent stress relaxation resistance is disclosed. Moreover, in patent document 3, while smoothing the surface of a Corson alloy, a compressive residual stress is provided and it opposes the tensile stress by product bending, and the generation | occurrence | production of a crack is suppressed.

Japanese Laid-Open Patent Publication 2006-161148 Japanese Laid-Open Patent Publication 2006-265731 Japanese Laid-Open Patent Publication 2005-48262

The appearance of the bent portion of the Corson alloy, in particular the appearance of the bending GW in which the bending axis is orthogonal to the rolling direction, is inferior to that of phosphor bronze, and has a great surface roughness. If a crack occurs in the terminal, the electrical conductivity and the spring property, which are required for the terminal, are lost and the reliability of the product is impaired. Therefore, the appearance inspection of the product bent portion is usually performed. However, for example, it is difficult to visually confirm the appearance of the bent portion of the state-of-the-art miniature terminal, and in the inspection step of confirming the situation after the bending press, it is seen using a magnifying glass or checked by a surface inspection device by a CCD camera. You can't help but rely on jigs or machines. In this inspection, it is not actually cracked. However, since the surface roughness of the bent portion appearance is severe, it is difficult to distinguish it from cracks, and inspection inspection takes time, and inspection efficiency is lowered. Therefore, the Corson alloy used for the microelectronic device material is not only required to cause cracks in the bent portion, but also to require a small surface roughness of the bent portion.

However, even in the examples of Patent Documents 1 and 2, even if the bendability is the most favorable, MBR / t (the ratio of the minimum bending radius and plate thickness that can be bent without cracking) is 0.5, and the conventional Corson alloy It is not shelled out from the relationship between strength and bendability, and it cannot cope with the strict bending process currently demanded. Further, in this embodiment, since the MBR / t having the best bendability is 0.5 or more, the wrinkles of the bent portion are considered to be large, which is not suitable for the use of a microminiature connector terminal which requires strict bending processing and its appearance inspection.

Moreover, although patent document 3 pays attention to product surface roughness for the purpose of improving the fatigue characteristic with respect to repeated bending, it does not aim at the improvement of the appearance of the bent part after a bending process. Therefore, only the surface roughness before bending is evaluated, and not after bending.

An object of the present invention is to improve the surface roughness of a bent portion, which has not been noticed in the past, after the bending of GW (good way), as well as the excellent bendability of the Corson-based copper alloy, in particular, the crack.

The present inventors have studied for the purpose of improving the bendability of the GW and the surface roughness of the bent portion, and as a result, the portion which becomes the starting point of uneven elongation such as foreign matters or defects is removed from the vicinity of the surface, and the plate thickness center portion (other than the surface layer below) By suppressing the formation of the shear zone of the surface layer (from the surface of the material to the depth of 1/6 of the plate thickness), the mechanical properties such as tensile strength of the material, 0.2% yield strength, spring limit value, etc. are roughly applied to the surface of the bent portion of the GW. The present invention was completed by finding that it can be improved.

The present invention has the following configuration.

(1) Based on the mass percentage (%) (hereinafter referred to as%) Ni: 0.8 to 4.6% and Si: 0.3 to 1.6%, and in the optional components Sn, Zn, Fe, Co, Cr, Mg and Mn It is a copper alloy containing at least one kind in a total amount of 2.0% or less, and the remainder is a copper alloy composed of Cu and unavoidable impurities. The ratio Ss / Sc of the number of lines of the band Ss and the number of lines Sc of the shear bands of the shear band of the portion other than the material surface layer (hereinafter referred to as the "plate thickness center part") is 1.0 or less, which is characterized by high strength and excellent appearance after bending. Cu-Ni-Si alloy bath.

(2) The Cu-Ni-Si-based alloy bath according to (1), wherein the number of lines of the front end of the material surface layer is 10/10000 µm ² or less.

(3) In the material surface layer, the number of precipitates having a particle size of 1 to 10 μm is 1.0 × 10 ² particles / mm ² or less, and the number Ns of precipitates having a particle size of 1 to 10 μm in the surface layer and the plate thickness center portion. The ratio Ns / Nc of the number Nc of the precipitate of particle size 1-10 micrometers is 1.0 or less, The Cu-Ni-Si-type alloy bath as described in (1) or (2) characterized by the above-mentioned.

This invention can provide the high strength copper alloy which shows the outstanding bending workability which is suitable as a copper alloy for electronic materials, such as a terminal and a connector, and the appearance of a bent part without wrinkles.

1 is an optical micrograph (800 times) of the surface layer part of the plate thickness cross section parallel to the rolling direction of the alloy bath manufactured in Example 4 (before bending deformation).
Fig. 2 is an optical microscope photograph (800 times) of the center of the plate thickness of the alloy bath of the present invention (before bending deformation, reference diagram).
3 is an optical micrograph (200 times left, 400 right) photographing the cross section parallel to the rolling direction after the bendability evaluation test of the alloy baths prepared in Example 4 (upper) and Comparative Example 34 (lower). Pear).

Specific elements of the invention are described below.

(1) composition of copper alloys

Ni: Ni reacts with Si to produce a compound having a Ni ₂ Si composition, and precipitates in the Cu matrix, thereby suppressing a decrease in conductivity and greatly improving strength. Ni addition amount with respect to the copper alloy of this invention is 0.8-4.6% (mass%, below same), and less than 0.8%, precipitation amount is small and sufficient strength is not obtained, but when it exceeds 4.6%, strength improves at the time of casting or hot working Precipitates which do not contribute to the formation of the resin are not produced, and the strength corresponding to the amount of addition is not obtained, and adversely affects the hot workability and the bending workability, and the precipitates coarsen and protrude from the cross section of the lead frame, thereby deteriorating the adhesion of the precious metal plating. .

Si: Si reacts with Ni without adversely affecting the conductivity to produce a compound having a Ni ₂ Si composition. Therefore, when the addition amount of Ni is determined, the optimum amount of Si addition is determined. Si addition amount with respect to the copper alloy of this invention is 0.3 to 1.6%, and when less than 0.3%, sufficient strength is not obtained similarly to the case of Ni, and when it exceeds 1.6%, various problems similar to the case of Ni arise.

Sn: It is anticipated that intensity | strength will become high by containing Sn. However, in general, in the case of recovering electronic materials such as Sn-plated connectors as scrap and reusing them at low cost without a smelting process, they are inevitably contained in the reused copper alloy material, and when the content exceeds 2.0% by mass, the conductivity decreases. Therefore, the upper limit was made into 2.0 mass%.

Although Zn: Zn improves heat resistance, such as heat-peelability of the tin plating layer in the case of tin plating a copper alloy, the conductivity is lowered when it exceeds 2.0% by mass, so the upper limit is set to 2.0% by mass.

Mg: Although Mg improves a stress relaxation characteristic, when it exceeds 2.0 mass% as a component which degrades the heat-peelable peelability of plating, the heat-peelable peelability of plating falls.

Fe, Co, Cr, Mn: Fe and Co react with Si to form a silicide and precipitate, contributing to the improvement of strength. Cr and Mn also have the effect of improving hot rolling properties. This is because these elements have a strong affinity with sulfur to inevitably form a compound with sulfur present in the alloy, thereby reducing the segregation of sulfur at the ingot grain boundary causing hot rolling cracking. The addition amount of one or more of these elements is 2.0% or less in total amount, and when it exceeds 2.0%, the lowering of the conductivity is not preferable.

(2) causes of bending wrinkles

In general, when bending a material, the deformation is most imparted to the outermost circumference of the bend. In bending, the material surface is uniformly stretched up to a specific strain value, but the elongation is small locally at the boundary of the specific strain value, and bending wrinkles occur. As the bending process proceeds, cracking occurs from the wrinkles. The strain limit value at which local elongation (hereinafter, non-uniform elongation) occurs is largely dependent on the mechanical properties of the material, but if the material exists as a starting point for non-uniform elongation such as foreign matter or defects, Uneven elongation tends to occur below the strain limit value according to the mechanical properties of, and the wrinkles of the bent portion tend to increase. Therefore, bending wrinkles can be made small by reducing the starting point where these nonuniform extension occurs.

In addition, if there is a starting point where uneven stretching occurs inside the material, it is not as good as the starting point existing on the surface of the material, but since this affects the surface of the material as a cause, it is desirable to reduce the starting point where the uneven stretching occurs inside the material as well. .

As a factor which becomes a starting point of nonuniform elongation, the roughness of a material surface and the precipitate which exists in a surface layer are mentioned. Although the roughness of the material surface can be made small by conventional means such as surface polishing of the final rolled roll surface, it alone cannot cope with the bending processing required for the latest micro terminal.

(3) shearing zones in metal structures

In general, the copper alloy can be strengthened by adjusting the particle size (crystal refinement) of the metal crystal, the amount of the precipitate, the particle size, the distribution (precipitation strengthening), and the like, but can also be strengthened by adjusting the workability of the final cold rolling (work reinforcement). ). In rolling, the load by the rolling roll is applied to the material loaded with the tension in the longitudinal direction, and the material is deformed (rolled). During this rolling, the shear deformation is concentrated locally, the grain structure is strained and broken, and a band-like structure called a shear zone is formed regardless of the crystal orientation.

The line of the shear stage of the present invention intersects the flat grain structure parallel to the rolling direction observed when the plate thickness cross section parallel to the rolling direction of the rolled material is observed at an angle of about 10 to 60 °. Say the line that exists. For example, in the part enclosed with the ellipse of FIG. 2, it can be confirmed that the several shearing band which runs from the lower left to the upper right is parallel.

The shear zone is a tissue in which deformation is locally concentrated, that is, a portion in which dislocation density is increased due to a large accumulation of deformation, and it is difficult to deform compared to surrounding tissue. For this reason, in the material in which the shear band exists, uneven elongation generate | occur | produces from a shear band at the time of bending, and wrinkles and a crack generate | occur | produce when non-uniform elongation reaches the surface. However, since the work reinforcement is impossible unless the rolling process is performed until the shear stage is formed, and the required alloy strength cannot be achieved, the product after the final cold rolling inevitably includes the shear stage.

The present inventors pay attention to the distribution of shear zones, and found that the smaller the shear zones near the material surface, the less likely the uneven elongation to reach the surface occurs, so that fewer cracks and wrinkles occur. That is, when the deformation | transformation implement | achieved as a shear stage is less in the surface layer than a plate thickness center part, a crack and a wrinkle hardly arise at the time of bending work. Specifically, if the ratio Ss / Sc of the number of lines Ss of the shear stage observed in the material surface layer after the final rolling and the number of lines Sc of the shear stage of the plate thickness center portion (parts other than the surface layer) is 1.0 or less, preferably 0.95 or less, Even during intense bending, the occurrence of bending wrinkles is reduced.

Further, if the number of lines in the shear zone of the surface layer of the material after the final rolling is preferably 10/10000 µm ² or less, more preferably 5/10000 µm ² or less, the occurrence of bending wrinkles is less.

In addition, when the total workability in the final rolling is lowered and the work reinforcement is not sufficiently performed, and the shear zone is small in the surface layer of the material and in the sheet thickness center part, the alloy bath of the present invention of high strength cannot be obtained.

Here, the shear stage is subjected to mechanical polishing of a plate thickness cross-section parallel to the rolling direction, and then immersed in an acidic aqueous solution such as dilute sulfuric acid or dilute nitric acid to be etched to exhibit crystal grain boundaries and shear zones, and then 200 to 800 times using an optical microscope. It can be observed by the magnification of a degree (refer FIG. 1-3). The line of the shear zone is a line of 5 µm or more in length that intersects at one or more points with the grain boundaries at an inclination of about 10 to 60 ° with respect to the rolling direction. Typical sizes of the shear stages are 1 µm or less in width and 5 to 30 µm in length.

In addition, since the reverse rolling was performed toward the left and right directions in the photograph shown in FIGS. 1-3, the shear stand is also formed with respect to each direction, and the angle of the line of the shear stand is directed to both the left and right directions.

(4) particle size and number of precipitates

Shear zones are likely to occur in areas where deformations accumulate. In addition, the deformation tends to be locally accumulated at the periphery of the precipitate particles in the portion where the tissue becomes discontinuous, that is, in the corson alloy. Therefore, when the density of precipitate particles is low, localization of deformation is also suppressed, and shear zones are less likely to occur. Here, the "precipitate" of the present invention is a cooling process after ingot solidification, such as crystallized matter generated in the solidification process during casting, oxides or sulfides generated by reaction in the molten metal during melting, and hot After rolling, metal compounds, such as precipitates which precipitate in a Cu matrix base material at the cooling process and the aging treatment after solution treatment, are collectively named. Therefore, if the precipitate particle | grains also have the particle | grains which consist of Ni and Si, the particle | grains which added the addition alloy element to this particle further, may not contain either one of Ni and Si, or may not contain both.

The particle diameter and number of precipitates can be observed at a magnification of about 200 to 2000 times using FE-SEM (electrolytic emission scanning electron microscope) after etching the material with ferric chloride aqueous solution. The component was measured using particle analysis software and EDS (energy dispersive X-ray analysis), and the particle | grains comprised from the component different from a base material component were determined as a precipitate. The particle size of each precipitate was measured and counted. Here, the diameter of the circle circumscribed to the precipitate is taken as the particle size of the precipitate.

Although the present invention is not limited by theory, in the surface layer from the surface of the material after the aging treatment to the depth of 1/6 sheet thickness, if the number of precipitates having a particle size of 1 to 10 μm is 1.0 × 10 ² particles / mm ² or less, Since the density of the precipitate which becomes the starting point of shear band generation is low, generation | occurrence | production of the shear band in a surface layer part becomes few, and the wrinkle which arises in a bending part can also be made small. On the other hand, when it exceeds 1.0x10 <^2> pieces / mm < ² >, generation | occurrence | production of the shear zone in a surface layer will increase and the wrinkles which generate | occur | produce in a bending part will become large. The number of precipitates having a particle diameter of 1 to 10 µm in the surface layer is preferably 1 × 10 ^-6 particles / mm ² or more, and if less than that, the precipitates are less in the material as a whole. There is this.

Moreover, if the ratio Ns / Nc of the number Ns of the particle | grains of the particle diameter of 1-10 micrometers in the surface layer, and the number Nc of the particle | grains of the particle diameter of 1-10 micrometers of a plate thickness center part is 1.0 or less, Preferably it is 0.95 or less, The occurrence of wrinkles is reduced even after the intense bending process. This is because deformation is not accumulated in the surface layer because the number of precipitate particles in the surface layer is smaller than the plate thickness center part, so that the shear zone is small, and cracks and wrinkles are less likely to occur during bending.

In addition, in the Corson alloy, even though fine precipitates are uniformly present, the strength improvement effect is observed, but precipitates having a particle size of 1 µm or more cause deterioration in the distribution density and grain boundary area of the precipitates, and are considered to be not preferable from the viewpoint of strength improvement. However, in the present invention, attention is paid to a precipitate having a particle size of 1 to 10 µm, which is likely to cause a shearing zone by localizing deformation by rolling, and adjusting the distribution to achieve the desired characteristics.

Precipitate particles having a particle diameter of less than 1 µm contribute to strengthening the precipitation but do not contribute very much to localization of deformation, and do not affect wrinkles of the bent portion because they hardly affect the generation of shear zones. In addition, the precipitate particle | grains whose particle diameter is less than 0.5 micrometer is too small so that the component judgment of whether it is a precipitate can not be made. On the other hand, in the whole including the surface layer and the plate thickness center part, since the precipitate which exceeds 10 micrometers of particle diameters becomes a cause of a crack, the number becomes like this. Preferably it is 1 piece / mm <2> or less, More preferably, it is 0 piece / mm <2>.

(5) Manufacturing method of alloy bath of the present invention

Next, the manufacturing method for obtaining the alloy of this invention is demonstrated.

Usually, manufacture of the ingot of a Corson alloy is performed by the semicontinuous casting method. It is desirable to control the temperature, time and cooling rate of the casting conditions so as not to produce coarse Ni-Si precipitates in the solidification process during casting. Ni-Si-based precipitates of a certain size or less can be dissolved in the Cu matrix by strengthening the heating of the hot rolling carried out after casting, but if the heating temperature is raised to solidify all the coarse precipitates in the matrix, the heating is performed. If the furnace refractory life of the furnace is shortened and the heating time is extended for a long time, the lead time is long and productivity is extremely deteriorated.

After heating at 800 degreeC or more for 1 hour or more, and performing hot rolling which makes end temperature 650 degreeC or more, the precipitate of the predetermined size or less precipitated and cast by casting is solid-solution in Cu matrix. In that case, when heated at a high temperature, precipitates precipitated and crystallized at the time of casting can be dissolved in the Cu matrix. However, when the heating temperature before hot rolling is 1000 ° C or higher, such as generation of a large scale and cracking during hot rolling Since a problem arises, the heating temperature before hot rolling is preferably 800 ° C or more and less than 1000 ° C.

The corson alloy is subjected to the solution treatment by heat treatment at a temperature lower than the solution treatment temperature to melt the Ni-Si-based precipitate that has been heated and precipitated by casting or hot rolling in the Cu matrix after the hot rolling process. It is often manufactured by the process which combined the aging treatment which precipitates solid solution Ni and Si, and the rolling which hardens before and after hardening treatment. Generally, it is manufactured by the process of solution treatment, rolling, an aging treatment, rolling, and a stress relief annealing. In the rolling before and after the aging treatment, in consideration of mechanical properties such as required tensile strength and 0.2% yield strength and bending workability, it is possible to omit either rolling before or after aging.

In this case, the higher the solution treatment temperature, the higher the solid solution amount of Ni and Si into the Cu matrix, and the Ni-Si-based intermetallic compound is precipitated from the matrix during the aging treatment to improve the strength. The solution treatment temperature for obtaining this effect is 700 degreeC or more, Preferably it is 800-950 degreeC. Further, the copper alloy of the present invention is about 950 ° C., but Ni and Si are sufficiently dissolved in the matrix. However, at temperatures exceeding 950 ° C., the oxidation of the material surface is vigorous during the solution heat treatment to remove the oxide layer. Since the load of an acid washing process becomes large, the processing temperature of 950 degreeC or less is preferable.

Usually, in the solution treatment process, it is quenched in order to maintain the solid solution state of Ni and Si as much as possible. In the present invention, it is noted that even in the cooling process of the solution treatment, no matter how rapidly it is quenched, a certain amount of Ni-Si intermetallic compounds are deposited almost uniformly inside the material. By slowing down, the temperature gradient is applied to the surface layer and the plate thickness center in the cooling process of the solution solution, and the number of precipitates having a particle diameter of 1 to 10 µm is changed to increase stepwise from the surface layer to the plate thickness center, and the surface layer shear zone after the final cold rolling The number of alloys was reduced and the alloy bath which showed the outstanding surface appearance after a bending process was obtained. Although the present invention is not limited by theory, the slower the cooling rate, the greater the difference in cooling rate between the surface layer and the sheet thickness center portion, the rapid cooling in the vicinity of the surface layer, the less precipitates, and the greater the precipitates in the plate thickness center portion. do.

The average cooling rate from solution temperature to 400 degreeC becomes like this. Preferably it is 500 degrees C / min or less, More preferably, it is 500-300 degrees C / min, Most preferably, it is 500-400 degrees C / min. If it is the said range, since it will quench in surface layer, the number of precipitates of 1 micrometer or more of particle diameters will fall, and since it cools in a plate thickness center part, the precipitate of particle diameters 1-10 micrometers will generate | occur | produce. If it exceeds 500 deg. C / min, the material is precipitated almost uniformly inside the material, so the bendability and appearance after the bending process are inferior. If it is less than 300 degreeC / min, the precipitate of a plate thickness center part will coarsen and the effect of precipitation strengthening by aging will not fully be acquired.

The average cooling rate from 400 degreeC to 70 degreeC becomes like this. Preferably it is 300 degrees C / min or less, More preferably, it is 300-100 degrees C / min. When it exceeds 300 degreeC / min, it will precipitate almost uniformly inside a material, and inferior in appearance after a bending process. On the other hand, when it is less than 100 degreeC / min, the precipitate of a center part of a plate thickness will coarsen and the effect of precipitation strengthening by aging will not fully be acquired. Moreover, since it takes time, it is not industrially preferable either.

In the present invention, since it is difficult to make the cooling rate constant in cooling from the solution temperature, the average cooling temperature is used. The average cooling rate of the present invention is obtained by dividing the difference between the solutionization temperature and 400 ° C or 400 ° C and 70 ° C by the time taken for cooling.

In addition, the theoretical solution heat temperature for the changing depending on the Ni and Si content, the actual solution treatment for in was performed in the range of +50 ~ 200 ℃ from the solubility limit temperature of the respective Ni ₂ Si concentration in the phase diagram of Cu-Ni ₂ Si .

The aging treatment is performed to grow fine precipitates in the material after the solution treatment to obtain desired strength and conductivity. The aging treatment temperature is preferably 300 to 700 ° C, more preferably 400 to 650 ° C. This is because the aging treatment is time-consuming and less economical at less than 300 ° C. Ni-Si particles are coarsened at temperatures exceeding 650 ° C, and Ni and Si are dissolved at temperatures above 700 ° C, so that the strength and conductivity are not improved. . When aging in the range of 300-700 degreeC, sufficient intensity | strength and electroconductivity are acquired as the aging treatment time is 1 to 10 hours.

Shear zones are caused by localization of the strain introduced into the material. As described above, when the number of precipitates having a particle diameter of 1 to 10 µm is reduced at the surface layer portion and largely at the plate thickness center portion, when the strain (rolling) is uniformly applied to the surface layer and the plate thickness center portion, the shear zone is small at the surface layer and the plate In the middle of the thickness is generated enough to enhance the processing.

In final cold rolling, the rolling load per length of 1 mm in the width direction of the material is preferably 50 to 150 kg / mm, more preferably 70 to 150 kg / mm. If it is less than 50 kg / mm, it cannot fully be reduced. On the other hand, when it exceeds 150 kg / mm, deformation tends to concentrate on the material surface, and the shear zone of a surface layer increases.

In addition, the viscosity of the rolled oil is preferably lower so that processing deformation occurs uniformly in the surface layer and the plate thickness center part by the final cold rolling. The viscosity of the rolled oil is preferably 11 to 7 cST, more preferably 10 to 8 cST. If it is less than 7 cST, it does not sufficiently engage between the roll and the material and does not play the role of the rolled oil. On the other hand, when it exceeds 11 cST, rolling oil will engage with the material surface at the time of rolling, inferior in surface smoothness, deformation will accumulate in a surface layer, and the number of shear zones of a surface layer will increase.

In addition, the total workability of cold rolling is 15 to 80%, and can be arbitrarily selected about mechanical properties and bending workability, such as required tensile strength and 0.2% yield strength. The workability per pass exceeds 5%, Preferably it is 10% or more. If it is 5% or less, the number of passes increases, and the number of front end bands of a surface layer increases.

In the copper alloy of the present invention, heat treatment (stress removal annealing) may be performed after the final cold rolling.

Since the copper alloy of this invention evaluates the change of the surface appearance after a bending process, material surface appearance is important. Adjustment of surface roughness can be performed by rolling, grinding | polishing, etc., for example. In actual operation, the surface roughness of a copper alloy can be adjusted by rolling using the rolling roll etc. which adjusted the surface roughness. In addition, the surface roughness can also be adjusted by performing buff polishing in which the roughness of the scale is different with respect to the material surface in the process after rolling, for example.

Surface average roughness Ra after the following bending process evaluation of the alloy bath of this invention is 2.0 micrometers or less, Preferably it is 1.5 micrometers or less.

Example

The results of the production examples and characteristic tests of the Cu-Ni-Si-based alloy according to the present invention are shown below, which are provided to better understand the present invention and its advantages, and are not intended to limit the present invention. It should be noted that

(Manufacturing method)

Copper alloys of various component compositions were dissolved in a high frequency melting furnace to cast ingots having a thickness of 20 mm, a width of 50 mm, and a length of 150 mm. Next, in order to sufficiently solidify Ni and Si in the matrix, the ingot is heated at a heating temperature of 800 ° C. or more and less than 900 ° C. for 2 hours or more, and then hot rolling is performed so that the end temperature is 650 ° C. or more to a thickness of 8 mm. It was. Subsequently, in order to remove the scale of a surface, it surface-treated and then rolled to predetermined | prescribed plate | board thickness.

Subsequently, after performing solution treatment for 10 minutes at the temperature of 850-950 degreeC according to plate | board thickness, it cools, adjusting each average cooling rate in solution temperature-400 degreeC and 400 degreeC-70 degreeC at predetermined speed. The number of precipitates having a particle diameter of 1 to 10 µm at the surface layer and the plate thickness center portion was adjusted.

Then, about Examples 1-29 and Comparative Examples 32-45, the aging treatment is performed for 5 hours at the temperature (400-600 degreeC) from which the highest intensity | strength is obtained by precipitation strengthening in each composition, and then cold rolling to 0.25 mm It was. In cold rolling, the rolling load and the viscosity of the rolling oil were variously selected to adjust the number of shear zones in the sample surface layer. The used rolled oil was the brand name Daphne stainless steel oil X-60 (viscosity 9.5 cST) made from Idemitsu Corporation, or the brand name Daphne stainless oil X-3K viscosity (12 cST) from Idemitsu Corporation. Mineral oil was added to the rolling oil of viscosity 12cST, or the rolling oil of viscosity 9.5cST, and the viscosity of the rolling oil was adjusted.

Moreover, about Example 30 and 31, after performing the solution process mentioned above similarly to Examples 1-29 and Comparative Examples 32-45, it cold-rolled to 0.25 mm. In cold rolling, the rolling load and the viscosity of the rolling oil were variously selected to adjust the number of shear zones in the sample surface layer. The used rolling oil is the same as the above. Thereafter, aging treatment was performed for 5 hours at a temperature (400 to 600 ° C) at which the highest strength was obtained by precipitation strengthening in each composition.

The number of passes of the final rolling in Examples 1 to 31 and Comparative Examples 32 to 43 is, for example, two passes in the case of one pass and a total workability of 30 to 50% in the case of 15 to 30% of the total workability. The above was changed according to the workability like 3 passes. Therefore, the processing rate per one pass was 10% or more at least.

In Examples 1 to 29 and Comparative Examples 32 to 45, since they were cold rolled after aging treatment, stress relief annealing (550 ° C., 15 seconds) was performed thereafter. In this invention, you may roll before an aging treatment, In that case, the stress removal annealing after aging can be abbreviate | omitted. In Examples 30 and 31, the stress relief annealing after aging was omitted. In the case of cold rolling before and after the aging treatment, stress removal annealing is performed after the final cold rolling.

(Assessment Methods)

In Examples 1 to 29 and Comparative Examples 32 to 45, the number of shear zones, the number of precipitate particles, the average crystal grain size, the strength, the conductivity, the bending workability evaluation, the tensile test, and the conductivity test were performed on the sample after the stress relief annealing. It was.

In Examples 30 and 31, the same test was performed on the sample after the aging treatment.

(a) Number of shear strips

Observation of the shear stage was performed by mechanical polishing using a 3 μm diamond paste for a plate thickness section parallel to the rolling direction, and then immersed in a solution of 5 g of ferric chloride + 30 ml of hydrochloric acid + 100 ml of water for 5 to 15 seconds. After the crystal grain boundary and the shear zone were exposed, a total field of view of 2 mm 2 randomly selected from the surface to the depth of 1/6 of the plate thickness was observed using an 800-fold optical microscope. Similarly, the plate thickness center part (between 1/6 depth of plate thickness to 5/6 depth) other than surface layer was observed. The shear stage was evaluated as a line having a length of 5 μm or more that forms an angle of 10 to 60 ° with the rolling direction and spans one or more grain boundaries.

(b) number of precipitate particles

Parallel to the rolling direction and the plate thickness perpendicular cross-section is etched for 2 minutes at room temperature with 47 Bume ferric chloride aqueous solution, followed by FE-SEM (Electromagnetic Radial Scanning Electron Microscope, Part Number XL30 / SFEG / TMP manufactured by Philips). A secondary electron image of a total field of view of 2 mm2 randomly selected from the depth of plate to 1/6 of the plate thickness and the center of the plate thickness (parts other than the surface layer), and first using the attached particle analysis software, The other part was binarized, the component was measured using EDS (Energy Dispersive X-ray Analysis), and the precipitate comprised from the component different from a base material component was identified. The number of particle diameters 1-10 micrometers was counted among these identified precipitate particle | grains using particle analysis software (EDS particle | grains / phase analysis software by Phoenix Corporation). In addition, in all the Examples and the comparative examples, the precipitate exceeding 10 micrometers of particle diameters did not exist in the surface layer and plate thickness center part.

(c) average crystal grain size

The crystal grain diameter was measured based on the cutting method (JIS H 0501) prescribed | regulated by JIS. Specifically, the sample was embedded in a resin such that the observation surface was perpendicular to the rolling direction, and after the mirror surface finish by mechanical polishing, the solution was mixed in a ratio of 10 parts by volume hydrochloric acid having a concentration of 36% to 100 parts by volume of water, 5% by weight of ferric chloride was dissolved in the solution weight. In this way, the sample was immersed in the completed solution for 10 seconds to reveal the metal structure. Next, the metal structure was enlarged by 1000 times with an optical microscope to take a picture, and a cutting line (JIS H 0501) prescribed by JIS specifies a line segment of 200 mm on the picture parallel to the plate width direction of the sample. Ten pieces of five pieces and five orthogonal lines were drawn at intervals of 25 mm each, and the number of crystal grains n cut by the line segments was counted and obtained from a formula of [200 mm × 10 / (n × 1000)]. The observed number of views is one field of view arbitrarily selected for the plate thickness center portion for each sample.

(d) tensile test

In accordance with JIS Z 2241, a tensile test was performed in parallel with the rolling direction using a JIS 13B No. tensile test piece to obtain tensile strength (tensile strength, MPa). In the Cu-Ni-Si-based alloy bath of the present invention, the high strength means that the tensile strength is usually 680 MPa or more, preferably 780 MPa or more, and more preferably 800 MPa or more.

(e) conductivity

Electrical conductivity (% IACS) was measured by the four terminal method based on JISH0505. Preferably it is 44.0% IACS or more, More preferably, it is 45.0% IACS or more.

(f) Bending workability evaluation

GOOD WAY bending (R = 0.125, R / t = 0.5) was performed according to JIS Z 2248, and the bending surface was observed. The observation method photographed the bending surface using Lasertec Corporation Confocal Microscope HD100, and measured and compared average roughness Ra using the attached software. In addition, as a result of observing the sample surface before the bending process using a confocal microscope, unevenness could not be confirmed. The case where surface average roughness Ra after bending process exceeds 2.0 micrometers evaluated the external appearance after bending process inferior. In addition, in this invention, "excellent external appearance after a bending process" means that surface average roughness Ra after the said bending process is 2.0 micrometers or less.

The manufacturing conditions and the characteristic of the material manufactured as mentioned above are shown to Tables 1-3. In Table 1, Examples 1-16 are the alloy baths of this invention which do not add another metal component, In Table 2, Examples 17-31 are the examples which added other arbitrary metal components within the range. The surface layer / plate thickness center part ratio Ss / Sc of the number of shear stages is less than 1.0, and the number Ss of the shear stages of a surface layer is ten or less / 10000 micrometer <^2> . Therefore, the external appearance of the surface part after bending process was excellent. Further, Examples 30 and 31 are examples in which rolling and aging are sequentially performed after solution formation, and final stress relief annealing is not performed. By adjusting the number Ss, Ss / Sc, and the like of the shear stages of the surface layer into the present invention, It turns out that the same characteristic as invention is acquired.

In Table 3, since the addition amount of Ni and Si was small, the comparative example 32 had the tensile strength as low as 643 Mpa although it manufactured on the same conditions as Example. In Comparative Example 33, since Ni was added at 5.0%, cracking occurred badly during hot rolling, and the subsequent steps could not be advanced.

Comparative Example 34 is an example in which the average cooling rate from the solution temperature to 400 ° C. was increased to 650 ° C./min. The ratio Ns / Nc of the number of precipitates having a particle diameter of 1 to 10 μm at the surface layer and the number of precipitates at the plate thickness center portion is greater than 1, and as a result, the number of shear zones of the surface layer is larger than the plate thickness center portion, and the surface of the bent portion after bending The appearance was inferior. In Comparative Example 35, on the contrary, the average cooling rate from the solution temperature to 400 ° C. was slowed down to 100 ° C./min. The bending surface was bad because the number of precipitates in the surface layer was relatively large and the number of shear zones in the surface layer was large, The tensile strength was low, probably due to the coarsened effect of the precipitate.

Comparative Examples 36 and 37 are examples of changing the average cooling rate from 400 ° C to 70 ° C. In Comparative Example 36, the average cooling rate was increased, and as a result, the ratio Ns / Nc of the number of precipitates having a particle diameter of 1 to 10 μm in the surface layer and the number of precipitates in the center of the plate thickness was greater than 1, and as a result, the number of shear zones in the surface layer was increased. More than the plate thickness center part, the surface appearance of the bent part after bending process was inferior. In Comparative Example 37, since the cooling rate was too slow, the number of precipitates having a particle diameter of 1 to 10 µm in the surface layer was large. Moreover, the precipitate in the center part of plate | board thickness aggregated and coarsened. As a result, the ratio Ns / Nc of the number of precipitates having a particle diameter of 1 to 10 µm in the surface layer and the number of precipitates in the plate thickness center portion was greater than 1, the number of shear zones in the surface layer increased, and the appearance of the bent portion was inferior. Moreover, the tensile strength was low whether the precipitate was coarsened.

In Comparative Examples 38 and 39, the average cooling rate from the solution temperature to 70 degreeC is constant, but the comparative example 38 has a fast average cooling rate from 400 degreeC to 70 degreeC, and the comparative example 39 is 400 degreeC at the solution temperature. Since both the average cooling rate up to and the average cooling rate from 400 ° C. to 70 ° C. are all fast, the amount of precipitates having a particle diameter of 1 to 10 μm in the surface layer is large compared to the plate thickness center portion, and as a result, the number of shear zones in the surface layer is large. The appearance of the bent portion was inferior.

In Comparative Example 40, since the rolling load was too large, the number of shear zones in the surface layer was large, and the appearance of the bent portion was inferior. In Comparative Example 41, since the rolling load was small and the rolling force was small, even if the number of rolling passes was 20, the sheet could not be rolled to a predetermined plate thickness, and the evaluation was stopped on the way because it was not industrial.

In Comparative Example 42, since the viscosity of the rolled oil was too high, the number of shear zones in the surface layer was large, and the appearance of the bent portion was inferior. In Comparative Example 43, the viscosity of the rolled oil was low, slip occurred between the material and the rolled roll, and the surface of the material was severely scratched due to it, so that subsequent evaluation was not performed.

Comparative Example 44 is an example in which the workability per pass at the time of final rolling was 5%. Since the workability per one pass was made small, the number of passes is ten times and productivity is bad. Moreover, since plastic deformation was given to the surface layer intensively, the number of shear zones of the surface layer was 31, and the surface roughness after the bending process was large. Comparative Example 45 is an example in which the stress relief annealing conditions after the final rolling under the same conditions as in Comparative Example 44 were changed to 600 ° C. × 1 min. The number of precipitates in the surface layer slightly decreased to 42, but the number of shear zones in the surface layer was There were still 30 pieces, and the bend appearance was inferior.

As described above, according to the present invention, a high-strength copper alloy exhibiting excellent appearance of the bent portion that does not cause wrinkles or cracks in the appearance of the bent portion after bending is obtained, which is preferable as a copper alloy for electronic materials such as terminals and connectors.

Claims (3)

Based on the mass percentage (%) (hereinafter referred to as%) Ni: 0.8 to 4.6% and Si: 0.3 to 1.6%, and one or more of the optional components Sn, Zn, Fe, Co, Cr, Mg, and Mn In a total amount of 2.0% or less, and the remainder is a copper alloy composed of Cu and unavoidable impurities, and the number of lines of the shear stage (hereinafter referred to as "surface layer") from the material surface to 1/6 depth of the plate thickness The ratio Ss / Sc of the number Sc of the number of lines of the shear stage of Ss and the portions other than the material surface layer (hereinafter referred to as the "plate thickness center portion") is 1.0 or less, which is characterized by high strength and excellent appearance after bending. -Si alloy bath. The method of claim 1,
Cu-Ni-Si-based alloy bath, characterized in that the number of lines of the shear zone of the material surface layer is 10/10000 ㎛ ² or less. 3. The method according to claim 1 or 2,
In the material surface layer, the number of precipitates having a particle diameter of 1 to 10 μm is 1.0 × 10 ² particles / mm ² or less, and the number Ns of precipitates having a particle size of 1 to 10 μm in the surface layer and the particle diameter in the plate thickness center portion 1 to 10. The ratio Ns / Nc of the number Nc of 10 micrometers precipitates is 1.0 or less, Cu-Ni-Si system alloy tank.

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