JP4210706B1 - Copper alloy sheet with excellent stress relaxation resistance - Google Patents

Abstract

An object of the present invention is to provide a Cu—Ni—Sn—P based copper alloy sheet that satisfies stress relaxation characteristics in a direction perpendicular to the rolling direction and is excellent in required characteristics as other terminals and connectors. .
A Cu-Ni-Sn-P-based copper alloy plate having a specific composition, wherein the X-ray diffraction intensity ratio I (200) / I (220) on the surface of the copper alloy plate is set to a predetermined amount or less. Refinement of crystal grain size, improvement of stress relaxation resistance in the direction perpendicular to rolling, which is a required characteristic for terminals / connectors 3, and difference between stress relaxation resistance in parallel with rolling (anisotropy) Make it smaller.
[Selection] Figure 2

Description

  The present invention relates to a copper alloy plate excellent in stress relaxation resistance, and more particularly to a copper alloy plate excellent in stress relaxation resistance suitable for connection parts such as automobile terminals and connectors.

  In recent years, connection parts such as automobile terminals and connectors are required to have performance capable of ensuring reliability in a high temperature environment such as an engine room. One of the most important characteristics in reliability under this high temperature environment is a contact fitting force maintaining characteristic, so-called stress relaxation resistance characteristic.

  FIG. 2 shows a structure of a typical box connector (female terminal 3) as a connecting part such as an automobile terminal / connector. 2A is a front view, and FIG. 2B is a cross-sectional view. In FIG. 2, in the female terminal 3, a pressing piece 5 is cantilevered by an upper holder part 4. When the male terminal (tab) 6 is inserted into the holder, the pressing piece 5 is elastically deformed, and the male terminal (tab) 6 is fixed by the reaction force. In FIG. 2, 7 is a wire connecting portion, and 8 is a fixing tongue piece.

  As shown in FIG. 2, a constant displacement is applied to a spring-shaped component made of a copper alloy plate, and a male terminal (tab) 6 is fitted with a spring-shaped contact (pressing piece) 5 of a female terminal. In some cases, the contact fitting force is lost with the passage of time if the engine room is maintained in a high temperature environment such as an engine room. Therefore, the stress relaxation resistance is a resistance characteristic against a high temperature at which the contact fitting force of a spring-shaped part made of a copper alloy plate is not greatly reduced even when these connection parts are held in a high temperature environment.

  1A and 1B show a stress relaxation resistance test apparatus according to this standard. Using this test apparatus, one end of the test piece 1 cut into a strip shape is fixed to the rigid body test stand 2 and the other end is lifted and bent in a cantilever manner (warping magnitude d). After holding for a period of time, unloading is performed at room temperature, and the magnitude of warpage (permanent strain) after unloading is obtained as δ. Here, the stress relaxation rate (RS) is represented by RS = (δ / d) × 100.

  As such copper alloys having excellent stress relaxation resistance, Cu-Ni-Si based copper alloys, Cu-Ti based copper alloys, Cu-Be based copper alloys, and the like have been widely known. Cu-Ni-Sn-P-based copper alloys having a relatively small amount of additive elements are used. This Cu-Ni-Sn-P-based copper alloy can be ingoted in a shaft furnace, which is a large-scale melting furnace with a wide opening to the atmosphere, and its cost is greatly reduced due to its high productivity. It becomes possible.

  Various measures for improving the stress relaxation resistance of the Cu—Ni—Sn—P based copper alloy itself have been proposed. For example, in Patent Documents 1 and 2 below, Ni-P intermetallic compounds are uniformly and finely dispersed in a Cu-Ni-Sn-P-based copper alloy matrix to improve conductivity and at the same time stress relaxation resistance and the like. It is disclosed to improve.

Patent Documents 2 and 3 below disclose that a solid solution type copper alloy in which the P content of a Cu—Ni—Sn—P based copper alloy is lowered to suppress precipitation of a Ni—P compound is disclosed. Yes. Furthermore, the following Patent Document 4 specifies the substantial temperature and holding time of finish annealing in the production of a Cu—Ni—Sn—P based copper alloy plate to improve conductivity and at the same time stress relaxation resistance, etc. Is disclosed.
Japanese Patent No. 2844120 Japanese Patent No. 3871064 JP-A-11-293367 JP 2002-294368 A

  By the way, the stress relaxation rate of the rolled (obtained by rolling) copper alloy sheet is anisotropic, and the longitudinal direction of the female terminal 3 in FIG. 2 indicates which direction the rolling direction of the material copper alloy sheet is. Depending on whether it is facing, the stress relaxation rate becomes a different value. The same applies to the stress relaxation rate measurement, and the measured stress relaxation rate varies depending on which direction the longitudinal direction of the test piece is oriented with respect to the rolling direction of the material copper alloy sheet. In this respect, the stress relaxation rate tends to be lower in the direction perpendicular to the rolling direction of the copper alloy sheet than in the parallel direction.

  In this regard, in FIG. 2, when the female terminal 3 is manufactured by pressing the material copper alloy plate, the longitudinal direction of the female terminal 3 (longitudinal direction of the pressing piece 5) is perpendicular to the rolling direction. May be chamfered. The high stress relaxation resistance is usually required for bending (elastic deformation) in the length direction of the pressing piece 5. Therefore, when the sheet is cut so as to face the direction perpendicular to the rolling direction, the copper alloy sheet has a high stress relaxation resistance in the perpendicular direction, not in the parallel direction. Is required.

  For this reason, if the stress relaxation rate in the direction perpendicular to the rolling direction as well as the direction parallel to the rolling direction is high, the direction parallel to the rolling direction and the direction perpendicular to the rolling direction can be used regardless of the plate-up direction of the material copper alloy sheet. Even when the plate is cut in any direction, the stress relaxation resistance as a terminal / connector can be satisfied.

  In view of this point, the present invention provides Cu-Ni-Sn- as a terminal / connector that has a high stress relaxation rate in a direction perpendicular to the rolling direction as well as a direction parallel to the rolling direction and excellent stress relaxation resistance. An object is to provide a P-based copper alloy sheet.

  In order to achieve this object, the gist of the copper alloy sheet excellent in stress relaxation resistance of the present invention is mass%, Ni: 0.1 to 3.0%, Sn: 0.01 to 3.0%, P: A copper alloy plate containing 0.01 to 0.3% each and consisting of the remaining copper and inevitable impurities, the X-ray diffraction intensity I (200) from the (200) plane of the plate surface, and the plate The ratio to the X-ray diffraction intensity I (220) from the (220) plane of the surface, I (200) / I (220) is 0.25 or less, and the average crystal grain size is 5.0 μm or less.

  Here, the copper alloy plate is further, in mass%, Fe: 0.5% or less, Zn: 1% or less, Mn: 0.1% or less, Si: 0.1% or less, Mg: 0.3 % Or less is preferable. Moreover, it is preferable that the content of Ca, Zr, Ag, Cr, Cd, Be, Ti, Co, Au, and Pt in the copper alloy is 1.0% by mass or less in total of these elements. . Further, the copper alloy is Hf, Th, Li, Na, K, Sr, Pd, W, S, C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As, Sb, Bi. , Te, B, and the content of misch metal are preferably 0.1% by mass or less in total of these elements.

  In the present invention, the X-ray diffraction intensity ratio, I (200) / I (220), is regulated while suppressing the development of the Cube orientation of the Cu—Ni—Sn—P based copper alloy plate and the Cube. This is to develop a specific crystal orientation other than the orientation. In addition, in the present invention, the average crystal grain size is made as fine as 5.0 μm or less together with this. Accordingly, in the present invention, the anisotropy with respect to a specific direction such as a direction parallel to or perpendicular to the rolling direction is reduced, and the stress relaxation property in the direction perpendicular to the rolling direction is improved. The difference in stress relaxation resistance between the parallel direction and the perpendicular direction is reduced.

  On the other hand, contrary to the present invention, when the Cube orientation is developed, the development of a specific crystal orientation other than the Cube orientation is suppressed, or the average crystal grain size is coarsened, in any case In addition, the anisotropy in a specific direction such as a direction parallel to the rolling direction becomes strong, and on the contrary, the stress relaxation resistance property in the perpendicular direction is not improved. In addition, the difference in stress relaxation resistance between the direction parallel to and perpendicular to the rolling direction cannot be reduced, and the anisotropy (difference in stress relaxation characteristics) between the two directions increases.

(X-ray diffraction intensity ratio)
The X-ray diffraction intensity ratio of the present invention is determined by using an ordinary X-ray diffraction method, with the X-ray diffraction intensity I (200) from the (200) plane being the Cube orientation on the plate surface and an orientation other than the Cube orientation. The X-ray diffraction intensity I (220) from a certain (220) plane is measured. And it can obtain | require from these X-ray-diffraction intensity ratio (X-ray-diffraction peak ratio), I (200) / I (220).

  The texture of a normal copper alloy plate is composed of a considerable number of orientation factors. However, when these constituent ratios change, the plastic anisotropy of the plate material changes and the stress relaxation resistance changes. Among these, by controlling the orientation density of Cube orientation [also referred to as D (Cube)] and the other specific crystal orientation density within an appropriate range, it is possible to specify a direction parallel to or perpendicular to the rolling direction. The anisotropy with respect to the direction is reduced.

  That is, the development of a specific crystal orientation other than the Cube orientation is strengthened while suppressing the development of the Cube orientation. As a result, the stress relaxation resistance in the direction perpendicular to the rolling direction is improved, and the difference between the stress relaxation characteristics in the direction parallel to and perpendicular to the rolling direction is reduced. And, regardless of the plate direction of the raw material copper alloy plate, even when the plate is cut in a direction parallel to or perpendicular to the rolling direction, along with the direction parallel to the rolling direction and the rolling direction. The stress relaxation rate in the perpendicular direction is increased to satisfy the stress relaxation resistance characteristics of terminals and connectors.

  Therefore, in the present invention, the X-ray diffraction intensity I (200) from the (200) plane that is the Cube orientation on the surface of the plate and the X-ray diffraction intensity I (( 220), I (200) / I (220) is 0.25 or less, preferably 0.20 or less.

  When this I (200) / I (220) exceeds 0.25, the Cube orientation develops, the development of a specific crystal orientation other than the Cube orientation is suppressed, and a specific direction such as a direction parallel to the rolling direction is suppressed. The anisotropy with respect to the direction becomes strong, and on the contrary, the stress relaxation resistance in the perpendicular direction is not improved. In addition, the difference in stress relaxation resistance between the direction parallel to and perpendicular to the rolling direction cannot be reduced, and the anisotropy (difference in stress relaxation characteristics) between the two directions increases.

(Average crystal grain size)
In the present invention, the parallel or perpendicular direction to the rolling direction is specified by the combined technique of controlling the texture of the Cu—Ni—Sn—P based copper alloy sheet and controlling the average grain size to be reduced. The anisotropy with respect to the rolling direction is reduced to improve the stress relaxation resistance in the direction perpendicular to the rolling direction, and the difference between the stress relaxation characteristics in the direction parallel to and perpendicular to the rolling direction is reduced.

  Therefore, in the present invention, the average crystal grain size is made as fine as 5.0 μm or less. When the average crystal grain size exceeds 5.0 μm and the average crystal grain size is increased, even if the texture is controlled, anisotropy with respect to a specific direction such as a direction parallel to the rolling direction On the other hand, the stress relaxation resistance property in the perpendicular direction is not improved. In addition, the difference in stress relaxation resistance between the direction parallel to and perpendicular to the rolling direction cannot be reduced, and the anisotropy (difference in stress relaxation characteristics) between the two directions increases.

  This average crystal grain size can be measured in orientation distribution density measurement of a specific orientation by a crystal orientation analysis method using FESEM / EBSP. That is, this crystal orientation analysis method analyzes the crystal orientation based on a backscattered electron diffraction pattern (Kikuchi pattern) generated when an electron beam is obliquely applied to the sample surface. This method is also known as a high resolution crystal orientation analysis method (FESEM / EBSP method) for crystal orientation analysis of diamond thin films, copper alloys, and the like. Examples in which the crystal orientation analysis of a copper alloy is performed by this method as in the present invention are also disclosed in JP-A-2005-29857, JP-A-2005-139501, and the like.

  Analysis procedure by this crystal orientation analysis method, first, the measurement region of the material to be measured is usually divided into hexagonal regions, etc., and for each divided region, from the reflected electrons of the electron beam incident on the sample surface, Get Kikuchi pattern (specific orientation mapping). At this time, if the electron beam is scanned two-dimensionally on the sample surface and the crystal orientation is measured at every predetermined pitch, the orientation distribution on the sample surface can be measured.

  Next, the obtained Kikuchi pattern is analyzed to know the crystal orientation at the electron beam incident position. That is, the obtained Kikuchi pattern is compared with data of a known crystal structure, and the crystal orientation at the measurement point is obtained. Similarly, the crystal orientation of the measurement point adjacent to the measurement point is obtained, and those whose crystal orientation difference is within ± 10 ° (deviation within ± 10 ° from the crystal plane) are located on the same crystal plane. Shall belong. Further, when the orientation difference between both crystals exceeds ± 10 °, the interval (such as the side where both hexagons are in contact) is defined as the grain boundary. In this way, the distribution of grain boundaries on the sample surface is obtained.

  More specifically, a specimen for observing the structure is collected from the manufactured copper alloy plate, subjected to mechanical polishing and buffing, and then subjected to electrolytic polishing to adjust the surface. For the specimen obtained in this way, for example, using FESEM manufactured by JEOL Ltd. and EBSP measurement / analysis system OIM (Orientation Imaging Macrograph) manufactured by TSL, analysis software of the system (software name “OIM Analysis”) ) Can be used to measure the average grain size of each crystal grain. The measurement visual field range is, for example, an area of about 500 μm × 500 μm, and this is measured at an appropriate number of places on the test piece and averaged.

(Copper alloy component composition)
Next, the component composition of the copper alloy of the present invention will be described below. In the present invention, based on the premise of the composition of the copper alloy, as described above, the shaft furnace ingot is possible, and the Cu-Ni-Sn-P-based copper alloy that can greatly reduce the cost due to its high productivity and To do.

  And it corresponds to the press molding process for manufacturing connection parts such as automobile terminals / connectors with high efficiency and high speed, and also satisfies the required characteristics as connection parts such as automobile terminals / connectors, strength and stress resistance Basically, Ni: 0.1 to 3.0%, Sn: 0.01 to 3.0%, and P: 0.01 to 0.3%, respectively, in order to improve relaxation characteristics and conductivity. A copper alloy containing copper and the inevitable impurities is contained. In addition,% display of content of each element means the mass% altogether. The reasons for addition and suppression of alloy elements of copper alloy will be described below.

(Ni)
Ni is an element necessary to improve strength and stress relaxation resistance by forming a solid precipitate or a compound with a solid solution or other alloy elements such as P in a copper alloy matrix. If the Ni content is less than 0.1%, the amount of fine Ni compound of 0.1 μm or less or the absolute amount of Ni solid solution is insufficient even by the optimum production method of the present invention. For this reason, in order to exhibit these Ni effects effectively, the content of 0.1% or more is necessary.

  However, when Ni is contained excessively exceeding 3.0%, compounds such as Ni oxides, crystallized substances, and precipitates are coarsened or coarse Ni compounds are increased. As a result, the amount of fine Ni compound and the solid solution amount of Ni are reduced. Moreover, since these coarsened Ni compounds serve as starting points for fracture, the strength and bending workability also deteriorate. Therefore, the Ni content is in the range of 0.1 to 3.0%, preferably in the range of 0.3 to 2.0%.

(Sn)
Sn is dissolved in the copper alloy matrix to improve the strength. Further, Sn that is in solid solution suppresses softening due to recrystallization during annealing. If the Sn content is less than 0.01%, the amount of Sn is too small to improve the strength. On the other hand, when the Sn content exceeds 3.0%, not only the electrical conductivity is remarkably lowered, but also the solid solution of Sn is segregated at the grain boundaries, and the strength and bending workability are also lowered. Therefore, the Sn content is in the range of 0.01 to 3.0%, preferably 0.1 to 2.0%.

(P)
P is an element necessary for forming fine precipitates with Ni and improving strength and stress relaxation resistance. P also acts as a deoxidizer. If the content is less than 0.01%, the P-based fine precipitate particles are insufficient, so the content must be 0.01% or more. However, when it exceeds 0.3% and contains excessively, the Ni-P intermetallic compound precipitation particle | grains will coarsen and not only the intensity | strength and stress relaxation characteristics but hot workability will also fall. Therefore, the P content is in the range of 0.01 to 0.3%. Preferably, it is set as 0.02 to 0.2% of range.

(Fe, Zn, Mn, Si, Mg)
Fe, Zn, Mn, Si, and Mg are impurities that are easily mixed from melting raw materials such as scrap. Although these elements have their respective effects, they generally lower the electrical conductivity. Moreover, when content increases, it will become difficult to agglomerate with a shaft furnace. Therefore, when obtaining high conductivity, Fe: 0.5% or less, Zn: 1% or less, Mn: 0.1% or less, Si: 0.1% or less, Mg: 0.3% or less And regulate. In other words, in this invention, content below these upper limits is permitted.

  Fe raises the recrystallization temperature of a copper alloy like Sn. However, if it exceeds 0.5%, the electrical conductivity decreases. Preferably, it is 0.3% or less.

  Zn prevents peeling of tin plating. However, if it exceeds 1%, the conductivity is lowered and high conductivity cannot be obtained. Moreover, when ingot-making with a shaft furnace, 0.05% or less is desirable. And if it is a temperature range (about 150-180 degreeC) used as a terminal for motor vehicles, even if it contains 0.05% or less, there exists an effect which can prevent peeling of tin plating.

  Mn and Si have an effect as a deoxidizer. However, if it exceeds 0.1%, the electrical conductivity is lowered and high electrical conductivity cannot be obtained. Further, when ingot forming is performed in a shaft furnace, it is further preferable to set Mn: 0.001% or less and Si: 0.002% or less.

  Mg has the effect of improving the stress relaxation resistance. However, if it exceeds 0.3%, the electrical conductivity is lowered and a high electrical conductivity cannot be obtained. Moreover, when ingot-making with a shaft furnace, 0.001% or less is desirable.

(Ca, Zr, Ag, Cr, Cd, Be, Ti, Co, Au, Pt)
The copper alloy of the present invention further allows Ca, Zr, Ag, Cr, Cd, Be, Ti, Co, Au, and Pt to be contained as impurities in an amount of 1.0% or less in total. These elements have the effect of preventing the coarsening of crystal grains, but when the total of these elements exceeds 1.0%, the conductivity is lowered and high conductivity cannot be obtained. Moreover, it becomes difficult to ingot in a shaft furnace.

  In addition, Hf, Th, Li, Na, K, Sr, Pd, W, S, C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As, Sb, Bi, Te, B Misch metal is also an impurity, and the total of these elements is preferably limited to 0.1% or less.

(Copper alloy plate manufacturing method)
Next, the manufacturing method of this invention copper alloy board is demonstrated below. The manufacturing process itself of the copper alloy sheet of the present invention can be manufactured by a conventional method except for the conditions of the finish annealing process. That is, a final (product) plate is obtained by casting a molten copper alloy with an adjusted composition, ingot chamfering, soaking, hot rolling, and repeating cold rolling and annealing. However, in order for the copper alloy sheet of the present invention to obtain necessary characteristics such as strength and stress relaxation characteristics, there are preferable production conditions, which will be described below. Moreover, in order to make the structure of the copper alloy sheet of the present invention, as described later, it is necessary to carry out a combination of the final cold rolling and the subsequent low temperature annealing, and the conditions of these steps are as follows. Need to control.

  First, when casting the above-described copper alloy composition of the present invention, a highly productive ingot is possible in a shaft furnace which is a large-scale melting furnace. However, the time required from the completion of addition of the alloy element in the copper alloy melting furnace to the start of casting is set to within 1200 seconds, and further, the time required from the ingot extraction from the ingot heating furnace to the end of hot rolling is set to 1200 seconds. It is preferable to make it as short as possible, such as less than a second.

  By shortening the time from the completion of addition of the alloy element in the copper alloy melting furnace to the start of casting, and further shortening the time from extraction of the ingot from the ingot heating furnace to the end of hot rolling. In addition to suppressing coarse Ni compounds, a fine Ni compound amount and a solid solution amount of Ni can be secured. As a result, the conductivity, stress relaxation resistance, and strength of the copper alloy plate can be ensured.

  Even if it is intended to control the amount of fine Ni compound and the solid solution amount of Ni mainly by the cold rolling conditions and annealing conditions in the latter stage, the fine Ni compound amount and Ni in the preceding stage until the end of hot rolling. The absolute amount of the solid solution is less. Furthermore, when there are many coarse Ni compounds produced | generated in the process of the said front | former stage, the fine product which precipitated in the cold rolling and annealing process will be trapped by this coarse product, and will exist independently in a matrix. There are fewer and fewer fine products. For this reason, there is a possibility that sufficient strength and excellent stress relaxation resistance cannot be obtained for a large amount of Ni added.

  About hot rolling, what is necessary is just to follow a usual method, the entrance temperature of hot rolling is about 600-1000 degreeC, and end temperature shall be about 600-850 degreeC. After hot rolling, it is cooled with water or allowed to cool.

  Thereafter, cold rolling and annealing are repeated to obtain a copper alloy plate having a product thickness. Annealing and cold rolling may be repeated depending on the final (product) plate thickness. In cold rolling, the processing rate is selected so that a processing rate of about 30 to 80% is obtained in the final finish rolling. An intermediate recrystallization annealing can be appropriately sandwiched during the cold rolling.

  The final annealing temperature is set in a range where the maximum temperature is 500 to 800 ° C. as the actual temperature of the plate, and the holding time in this temperature range is preferably 10 to 60 seconds.

(Final cold rolling)
In the final cold rolling, the rolling speed is increased to 200 m / min or more. In addition to this, as will be described later, final annealing at a low temperature is performed. By increasing the rolling speed in the final cold rolling, the strain rate introduced into the Cu—Ni—Sn—P based copper alloy sheet is increased. Thereby, the crystal orientation other than the Cube orientation is easily developed, and the development of the Cube orientation is suppressed, so that the anisotropy of the stress relaxation resistance can be reduced. Further, randomization of crystal orientation is promoted, and a group of grains having the same orientation (crystal grains having similar crystal orientations form a group adjacent to each other) is reduced, so that individual crystal grain sizes are also refined. Therefore, the surface X-ray diffraction intensity ratio I (200) / I (220) of the Cu—Ni—Sn—P based copper alloy plate can be 0.25 or less, and the average crystal grain size is 5.0 μm or less. Can be fine. As a result, the stress relaxation resistance in the direction perpendicular to the rolling direction can be improved, and the difference from the stress relaxation rate in the direction parallel to the rolling direction can be reduced.

  On the other hand, if the rolling speed in the final cold rolling is too small as less than 200 m / min, the strain rate is small, so in the Cu—Ni—Sn—P based copper alloy plate as in the present invention, in particular, crystals other than the Cube orientation. The development of the orientation is suppressed, the same orientation grain group is easily formed, and the individual crystal grain size is increased. For this reason, the X-ray diffraction intensity ratio I (200) / I (220) cannot be made 0.25 or less, and the average crystal grain size easily exceeds 5.0 μm.

  The number of final cold rolling passes is preferably 3 to 4 times as usual, avoiding too few or too many passes. Also, the rolling reduction per pass need not exceed 50%, and each rolling reduction per pass takes into account the original plate thickness, the final plate thickness after cold rolling, the number of passes, and this maximum rolling reduction. It is determined.

(Final annealing)
In the present invention, final annealing at a low temperature is performed in a continuous heat treatment furnace after the final cold rolling. In the continuous annealing process in the continuous heat treatment furnace, it is possible to perform the low temperature annealing in the range of the maximum temperature of 100 to 400 ° C. for a short time by controlling the plate passing speed of the plate passing through the furnace. . In this respect, the development of the Cube orientation of the Cu—Ni—Sn—P-based copper alloy plate is achieved by setting the plate reaching speed in the range of 10 to 100 m / min in the range where the maximum temperature reaches 100 to 400 ° C. In addition, the anisotropy can be reduced by strengthening the development of a specific crystal orientation other than the Cube orientation. Further, the growth of crystal grains can be suppressed. Therefore, the surface X-ray diffraction intensity ratio I (200) / I (220) of the Cu—Ni—Sn—P based copper alloy plate can be 0.25 or less, and the average crystal grain size is 5.0 μm or less. Can be fine. As a result, the stress relaxation resistance in the direction perpendicular to the rolling direction can be improved, and the difference from the stress relaxation rate in the direction parallel to the rolling direction can be reduced.

  When the plate passing speed exceeds 100 m / min, the temperature change of the plate suddenly occurs from room temperature to the maximum temperature range of 100 to 400 ° C. Therefore, the residual strain remaining on the plate after the plate passing is Increasing, rearrangement of dislocations and recovery phenomenon are likely to occur. That is, the stress relaxation resistance decreases in both the direction perpendicular to the rolling direction and in the parallel direction. On the other hand, when the plate passing speed is less than 10 m / min, not only is the treatment time too long in the maximum temperature range of 100 to 400 ° C., but also the temperature rise and temperature drop rates are small. In such a Cu—Ni—Sn—P based copper alloy plate, the development of crystal orientations other than the Cube orientation is suppressed, and the growth of crystal grains is promoted. For this reason, the anisotropy of the stress relaxation resistance is increased, the X-ray diffraction intensity ratio I (200) / I (220) cannot be made 0.25 or less, and the average crystal grain size is too large exceeding 5.0 μm. It becomes easy to become.

  Moreover, in the temperature which annealing temperature is lower than 100 degreeC, or the conditions which do not perform this low-temperature annealing, possibility that the structure | tissue and characteristic of a copper alloy plate will hardly change from the state after the last cold rolling is high. On the other hand, when the annealing temperature exceeds 400 ° C., recrystallization occurs, dislocation rearrangement and recovery phenomenon occur excessively, and precipitates also become coarser, so the strength is likely to decrease.

  Examples of the present invention will be described below. By controlling the rolling speed in the final cold rolling, the sheet feeding speed in the low-temperature final annealing in the continuous heat treatment furnace after the final cold rolling, and the annealing temperature, the X-ray diffraction intensity ratio I (200) / Copper alloy sheets with different I (220) were produced. Then, various properties such as electrical conductivity, tensile strength, 0.2% proof stress and stress relaxation resistance of each of these copper alloy thin plates were evaluated.

  Specifically, after each copper alloy having the chemical composition shown in Table 1 (the remaining composition excluding the element amount is Cu) is melted in a coreless furnace, a semi-continuous casting method (cooling solidification rate of casting). (2 ° C./sec) to obtain an ingot having a thickness of 70 mm, a width of 200 mm, and a length of 500 mm. These ingots were commonly rolled under the following conditions to produce a copper alloy sheet. After chamfering and heating the surface of each ingot, it is heated at 960 ° C. in a heating furnace, and immediately hot-rolled at a hot rolling end temperature of 750 ° C. to form a plate having a thickness of 16 mm. Quenched into water.

  At this time, the time required from the completion of addition of the alloy element in the melting furnace to the start of casting is 1200 seconds or less in common with each example, and the time required from the heating furnace extraction to the end of hot rolling is common with each example. It was set to 1200 seconds or less.

  After removing the oxide scale, this plate was subjected to cold rolling → continuous finish annealing → cold rolling → strain relief annealing to produce a copper alloy thin plate. That is, the plate after primary cold rolling (rough cold rolling, intermediate cold rolling) was faced. The final annealing of this plate was performed in an annealing furnace with a maximum temperature of 600 ° C. and a holding time of 60 seconds at this temperature as the actual temperature of the plate.

  After this finish annealing, final cold rolling with a rolling reduction of 60% was performed. The rolling speed in this final cold rolling was controlled respectively. In the final cold rolling, rolls having the same roll diameter (60 mm) and roll length (500 mm) were used for all four passes, and the rolling reduction per pass was the same as 30%.

  After this final cold rolling, the solid temperature (maximum temperature reached) was kept constant at 350 ° C., and the low-speed annealing was performed in a continuous annealing furnace with various plate feeding speeds changed to the values shown in Table 2. A copper alloy thin plate having a thickness of 0.25 mm was obtained.

  In addition, in each copper alloy shown in Table 1, the balance composition excluding the element amount described is Cu, and as other impurity elements, elements of group A, Ca, Zr, Ag, Cr, Cd, Be, Ti The content of Co, Au, and Pt was 1.0% by mass or less in total of these elements, except for Invention Example 9 in Table 1 (Invention Example 10 in Table 2).

  Further, B group elements Hf, Th, Li, Na, K, Sr, Pd, W, S, Si, C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As , Sb, Bi, Te, B, misch metal content was 0.1% by mass or less in total of these elements except for Invention Example 10 in Table 1 (Invention Example 11 in Table 2). .

  With respect to the copper alloy plate thus obtained, in each example, a sample was cut out from the copper alloy plate, and various properties such as conductivity, tensile strength, 0.2% proof stress, and stress relaxation resistance of each sample were evaluated. did. These results are shown in Table 2, respectively.

(Tissue measurement)
For a copper alloy plate sample, using an X-ray diffraction analyzer (model: RINT1500) manufactured by Rigaku Corporation, using Co as the target, tube voltage 40 kV, tube current 200 mA, scanning speed 2 ° / min, sampling width 0.02 °, measurement The X-ray diffraction intensity I (200) from the (200) plane of the plate surface and the X-ray diffraction intensity I (220) from the (220) plane are measured in the range (2θ) of 30 ° to 115 °. The X-ray diffraction intensity ratio I (200) / I (220) was determined. Measurement was performed at two locations, and I (200) / I (220) was an average value thereof.

(Measurement of average crystal grain size)
The average crystal grain size was measured by the crystal orientation analysis method using FESEM / EBSP described above. The measurement points of the test pieces were commonly used as arbitrary five points, and the average crystal grain sizes measured at these five points were averaged to obtain the average crystal grain size.

(Tensile test)
A test piece was collected from the copper alloy thin plate, and a JIS No. 5 tensile test piece was prepared by machining so that the longitudinal direction of the test piece was perpendicular to the rolling direction of the plate. Then, mechanical characteristics including elongation were measured with a universal testing machine manufactured by Instron, Inc., 5882 type under the conditions of room temperature, a test speed of 10.0 mm / min, and GL = 50 mm. The proof stress is a tensile strength corresponding to a permanent elongation of 0.2%.

(Conductivity measurement)
A sample was taken from the copper alloy thin plate and the conductivity was measured. The electrical conductivity of the copper alloy plate sample is a double-bridge type in accordance with the nonferrous metal material conductivity measurement method specified in JIS-H0505 by processing a strip-shaped test piece of width 10 mm x length 300 mm by milling. The electrical resistance was measured with a resistance measuring device, and the conductivity was calculated by the average cross section method.

(Stress relaxation characteristics)
The stress relaxation rate of the copper alloy sheet was measured in the parallel direction with respect to the rolling direction and in a direction perpendicular to the direction perpendicular to the parallel direction, and the stress relaxation resistance in this direction was evaluated. In the stress relaxation rate measurement test below, the stress relaxation rate in the direction perpendicular to the direction parallel to the rolling direction is less than 10%, and the difference between the stress relaxation rates in the direction parallel to the direction perpendicular to the rolling direction is within 3%. Passed as stress relaxation resistance.

  Specifically, the stress relaxation rate was measured using a cantilever system shown in FIG. 1 by collecting a test piece from the copper alloy thin plate. A strip-shaped test piece 1 having a width of 10 mm (with the length direction perpendicular to the rolling direction of the plate material) is cut out, one end thereof is fixed to the rigid body test stand 2, and the span length L of the test piece 1 is d. A deflection amount having a size of (= 10 mm) is given. At this time, L is determined so that a surface stress corresponding to 80% of the material yield strength is applied to the material. This is held in an oven at 120 ° C. for 3000 hours and then taken out. The permanent distortion δ when the deflection amount d is removed is measured, and the stress relaxation rate (RS) is calculated by RS = (δ / d) × 100.

  As is apparent from Table 2, Invention Examples 1 to 11 which are copper alloys (alloy numbers 1 to 10) within the composition of the present invention in Table 1 are manufactured such as rolling speed in final cold rolling and sheet passing speed in final annealing. Each of the methods is also manufactured within preferred conditions. For this reason, as for the invention example of Table 2, the said X-ray-diffraction intensity ratio I (200) / I (220) of the Cu-Ni-Sn-P type copper alloy plate surface is 0.25 or less. Also, the average crystal grain size is as fine as 5.0 μm or less.

  In addition, since the composition of the invention example is suitable and manufactured under the above-mentioned preferable conditions, Ni compounds such as coarse Ni oxides, crystallized substances, and precipitates are suppressed, It is presumed that the amount of fine Ni compound and the like and the solid solution amount of Ni can be secured.

  As a result, Invention Examples 1 to 9 have terminal / connector characteristics in which the electrical conductivity is 30% IACS or more and the stricter stress relaxation rate in the direction perpendicular to the rolling direction is less than 10%. Further, the difference in stress relaxation rate between the direction perpendicular to the rolling direction and the direction parallel to the rolling direction is as small as about 2-3%. And it has further the mechanical characteristic that 0.2% yield strength is 500 Mpa or more. That is, the inventive example is a copper alloy plate having high electrical conductivity and strength, particularly excellent in stress relaxation resistance, and having these characteristics.

  However, among Invention Examples in Table 2, Invention Examples 10 and 11 (alloy numbers 9 and 10 in Table 1) in which the amount of other elements exceeds the above-described preferable upper limit are compared with other Invention Examples having relatively high conductivity. Thus, the conductivity is low. Invention Example 10 shows that the total of the elements A group: Ca, Zr, Ag, Cr, Cd, Be, Ti, Co, Au, and Pt is as shown in Alloy No. 9 in Table 1, and the preferable upper limit is 1.0. Higher than mass%. Invention Example 11 includes element B group: Hf, Th, Li, Na, K, Sr, Pd, W, S, C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As, Sb , Bi, Te, B, and the misch metal are higher than the preferable upper limit of 0.1% by mass as described in Alloy No. 10 of Table 1.

  Invention Example 4 in Table 2 (Alloy No. 3 in Table 1) has a Ni content of a lower limit of 0.1%. Invention Example 5 (Alloy No. 4 in Table 1) has an upper limit of 3.0% for the Ni content. Invention Example 6 (Alloy No. 5 in Table 1) has a Sn content of 0.01%. Invention Example 7 (Alloy No. 6 in Table 1) has an Sn content of 3.0% as the upper limit. Invention Example 8 (Alloy No. 7 in Table 1) has a lower P content of 0.01%. Invention Example 9 (Alloy No. 8 in Table 1) has an upper limit of 0.3% for the P content.

  Inventive Example 2 in which the production conditions such as the rolling speed in the final cold rolling and the sheet passing speed in the final annealing are on the lower limit side have relatively lower stress relaxation resistance and strength than Inventive Example 1.

  In Comparative Examples 12 to 17 in Table 2, the production methods such as the rolling speed in the final cold rolling and the sheet feeding speed in the final annealing are also produced within preferable conditions. For this reason, Comparative Examples 12 to 17 have anisotropy in which the X-ray diffraction intensity ratio I (200) / I (220) on the surface of the Cu—Ni—Sn—P based copper alloy plate is 0.25 or less. . Nevertheless, since these comparative examples use copper alloys outside the composition of the present invention of alloy numbers 11 to 16 in Table 1, any one of the conductivity, strength, and stress relaxation resistance characteristics is the invention example. Remarkably inferior.

  In Comparative Example 12, the Ni content deviates from the lower limit (alloy number 11 in Table 1). For this reason, strength and stress relaxation resistance are low. In Comparative Example 13, the Ni content is higher than the upper limit (Alloy No. 12 in Table 1). For this reason, the balance between strength and conductivity is low.

  In Comparative Example 14, the Sn content is slightly lower than the lower limit (Alloy No. 13 in Table 1), so the strength and stress relaxation resistance are too low. In the copper alloy of Comparative Example 15, the Sn content is higher than the upper limit (alloy number 14 in Table 1), and thus the conductivity is low.

  In Comparative Example 16, since the P content deviates from the lower limit (alloy number 15 in Table 1), the strength and the stress relaxation resistance are low. In Comparative Example 17, since the P content was higher than the upper limit (Alloy No. 16 in Table 1), cracking occurred during hot rolling, and the characteristics could not be evaluated.

  Comparative Examples 18 and 19 in Table 2 are copper alloys (Alloy Nos. 1 and 2) within the composition of the present invention in Table 1, and other production conditions are also in the preferred range as in the inventive examples. Nevertheless, the rolling speed in the final cold rolling and the sheeting speed in the final annealing are out of the preferred ranges. In Comparative Example 18, the rolling speed in the final cold rolling is too slow. In Comparative Example 19, the rolling speed in the final cold rolling is too slow, and the sheet passing speed in the final annealing is too slow.

  As a result, in Comparative Examples 18 and 19, the X-ray diffraction intensity ratio I (200) / I (220) on the surface of the Cu—Ni—Sn—P-based copper alloy plate exceeds 0.25. Also, the average crystal grain size is coarsened exceeding 5.0 μm. As a result, these comparative examples are remarkably inferior in stress relaxation resistance in the direction perpendicular to the rolling direction as compared with the inventive examples. Moreover, the difference between the stress relaxation rate in the direction perpendicular to the rolling direction and the stress relaxation rate in the direction parallel to the rolling direction is also large. Furthermore, the strength is also lower than that of the inventive examples.

  From the above results, the stress relaxation characteristics in the direction perpendicular to the rolling direction are satisfied, there is not much difference between the stress relaxation characteristics in the direction parallel to the rolling direction, and the required characteristics as other terminals and connectors. The component composition and structure of the copper alloy sheet of the present invention for obtaining an excellent Cu—Ni—Sn—P based copper alloy sheet, and the significance of preferable production conditions for obtaining this structure are supported.

  As described above, according to the present invention, the stress relaxation characteristics in the direction perpendicular to the rolling direction are satisfied, and there is not much difference between the stress relaxation characteristics in the direction parallel to the rolling direction. It is possible to provide a Cu—Ni—Sn—P based copper alloy plate that is excellent in required characteristics as a connector. As a result, it is particularly suitable for connection parts such as automobile terminals and connectors.

It is sectional drawing explaining the stress relaxation test of a copper alloy plate. It is sectional drawing which shows the structure of a box-type connector.

Explanation of symbols

1: Test piece, 2: Test stand, 3: Box-shaped connector (female terminal), 4: Upper holder part, 5: Press piece, 6: Male terminal, 7: Wire connection part, 8: Fixing tongue

Claims (4)

  In mass%, Ni: 0.1-3.0%, Sn: 0.01-3.0%, P: 0.01-0.3%, respectively, the balance copper and copper consisting of inevitable impurities The ratio of the X-ray diffraction intensity I (200) from the (200) plane of the plate surface to the X-ray diffraction intensity I (220) from the (220) plane of the plate surface, I (200) A copper alloy sheet excellent in stress relaxation resistance, wherein / I (220) is 0.25 or less and the average crystal grain size is 5.0 μm or less.   The copper alloy plate is further, in mass%, Fe: 0.5% or less, Zn: 1% or less, Mn: 0.1% or less, Si: 0.1% or less, Mg: 0.3% or less The copper alloy plate excellent in stress relaxation resistance according to claim 1.   2. The copper alloy plate according to claim 1, wherein the content of Ca, Zr, Ag, Cr, Cd, Be, Ti, Co, Au, and Pt is 1.0% by mass or less in total of these elements. 2. A copper alloy sheet excellent in stress relaxation resistance as described in 2.   The copper alloy plate is Hf, Th, Li, Na, K, Sr, Pd, W, S, C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As, Sb, Bi, The copper alloy sheet excellent in stress relaxation resistance according to any one of claims 1 to 3, wherein the content of Te, B, and misch metal is 0.1% by mass or less in total of these elements.

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