JP4209145B2 - High strength phosphor bronze strip with excellent bending workability - Google Patents

Description

【００２３】
各試料の評価結果を表１に示す。対応関係にあるデータをグループ１〜７に分けて表示している。各グループのなかで比較すると、本発明のりん青銅の曲げ加工性が、従来のりん青銅である比較例の曲げ性より優れていることが明らかである。また、歪取り焼鈍を行なうことにより曲げ性が向上することもわかる。
グループ１とグループ２を比較すると、引張強さが同じ場合には、Ｓｎ濃度が高い方が曲げ性が良好であることがわかる。また、グループ３とグループ５を比較すると、Ｓｎ濃度を高くすることにより、曲げ性を低下させることなく、引張強さを高めることが可能であることがわかる。このようにＳｎを増やせば曲げ性を損なうことなく強度を改善することができるが、Ｓｎ濃度の上昇とともに導電率が低下し、Ｓｎが本発明での上限値である１１質量％を超えると導電率は１０％ＩＡＣＳを下回る。
【００２４】
【発明の効果】
圧延加工度を高くしてりん青銅を高強度化する場合、所定の強度を超えると曲げ性が著しく劣化する。この現象はせん断帯の発生に起因し、せん断帯が発生すると結晶方位に特徴的変化が現われる。以上の知見に基づき、結晶方位を制御することにより、高い強度と良好な曲げ性をあわせ持つりん青銅を得ることに成功した。本発明のりん青銅は、小型電子部品で使用される端子・コネクタ用の素材として好適である。また、本発明のりん青銅は、強度および曲げ性以外の特性が従来のりん青銅と同等であることから、工業的に極めて有用である。
【図面の簡単な説明】
【図１】りん青銅の引張り強度と(220)方位の集合度および曲げ加工性との関係を示す図である。
【図２】曲げ部外観の評価基準（日本伸銅協会技術標準T３０７（1999年））を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a phosphor bronze strip having high strength and good bending workability, and further to a terminal / connector using the same, used for electronic parts such as terminals / connectors.
[0002]
[Prior art]
In recent years, the progress of miniaturization and shortening of electronic parts has been remarkable, and correspondingly, thinner materials are required as copper alloy strips for electronic parts. As the material becomes thinner, the contact pressure of the connector decreases. In order to compensate for this decrease in contact pressure, it is necessary to increase the strength of the material. In addition, with the miniaturization of electronic components, finer processing is performed on the material, so that it is necessary to improve workability. As workability, bending workability is particularly important. This is because more severe bending of metal members such as terminals and connectors is performed with the progress of high-density mounting of cellular phones, digital cameras, video cameras, and the like.
As described above, copper alloy strips used for terminals, connectors, and the like are faced with contradictory problems of increasing strength and improving bendability.
[0003]
In response to this requirement, high-strength copper alloys such as beryllium copper and titanium copper, and in parts where conductivity is required, Corson alloy (Cu-Ni-Si), chromium copper (Cu-Cr, Cu- Medium strength and high conductivity type copper alloys such as Cr-Zr and Cu-Cr-Sn are used. However, since these copper alloys are relatively new as copper alloys for electronic parts, there are restrictions on the supply and demand and distribution in the market. For example, they tend to be avoided in markets that emphasize global standards. Moreover, the price is expensive compared with conventional copper alloys such as phosphor bronze and brass. Therefore, further improvements in strength and workability have been required for phosphor bronze having relatively excellent mechanical strength and workability among conventional copper alloys.
[0004]
Phosphor bronze strips are C5210 (8% Sn), C5212 (8% Sn), C5191 (6% Sn), C5102 (5% Sn), and C5111 (4% Sn) according to JIS H3110. In addition, C52400 (10% Sn) and the like have been standardized by ASTM. In general, there are solid solution strengthening, precipitation strengthening, dislocation strengthening, grain boundary strengthening, and the like as mechanisms for increasing the strength of metals. Phosphor bronze is a solid solution strengthened copper alloy. If it is assumed that the strength is improved within a standardized component range, dislocation strengthening or grain boundary strengthening is used. From this point of view, high strength has been achieved by optimizing cold rolling conditions or annealing conditions, but the current situation is behind the need for rapid progress in making electronic components lighter and thinner. is there.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide phosphor bronze having both high strength and good bending workability.
[0006]
[Means for Solving the Problems]
In order to increase the strength of phosphor bronze by the manufacturing process, the degree of rolling process may be increased. However, bendability decreases when the degree of processing is increased. In particular, the bending workability of the rolled material of phosphor bronze varies depending on the bending direction, the bending property in the direction (Bad Way) where the bending axis is parallel to the rolling direction is the worst, and the improvement in bending workability in this direction is the greatest. It is a problem. FIG. 1 shows this state, and the relationship between the tensile strength (σ _B ) and the bendability of ordinary phosphor bronze (C5210) containing 8% Sn is shown by the data of ○.
[0007]
Here, the bending workability is evaluated according to the Japan Copper and Brass Association technical standard “Bending workability evaluation method for copper and copper alloy sheet” (JBMA, T307 (1999)). ) Is 0.2 mm, width is 10 mm, length is 50 mm, W-bend is performed at various bending radii, and the minimum bending radius (MBR) that does not cause cracking is obtained, and the MBR / t value is calculated. is doing. The tensile strength is measured in parallel with the rolling direction.
It can be seen that when the degree of work is increased and the strength is increased, the bendability decreases, and particularly when σ _B exceeds 750 MPa, the bendability deteriorates rapidly. Materials with σ _B exceeding 850 MPa are extremely brittle and cracks occur even at MBR / t = 5.
[0008]
The present inventors investigated a change in structure accompanying an increase in the rolling degree in order to improve rapid deterioration of bendability at σ _B ≧ 750 MPa in phosphor bronze containing 8% Sn. As a result, a remarkable feature was found in the change in crystal orientation. When a metal material composed of a face-centered cubic lattice is rolled, the tensile strength usually increases with an increase in workability, and the degree of integration of (220) planes on the rolled surface increases with respect to crystal orientation. However, as indicated by ● in FIG. 1, in the case of the conventional phosphor bronze, the degree of aggregation of the (220) plane decreased from the point where the tensile strength exceeded 750 MPa. Note that the degree of assembly of the (220) plane in FIG. 1 is defined by the composition ratio with respect to the four main planes ((220), (111), (200), (311)) in the rolled copper alloy material.
r (220) = I (220) / (I (220) + I (111) + I (200) + I (311)) × 100
Here, I (hkl) is an integral value of the X-ray diffraction intensity of the (hkl) plane measured using a Co tube with an X-ray diffractometer.
[0009]
Plastic deformation due to rolling is mainly due to slip deformation, and this deformation increases the degree of accumulation of (220) on the rolled surface. However, when the degree of processing increases, slip deformation becomes difficult and a shear band occurs. The shear band is a non-uniformly deformed structure that appears parallel to the plate width direction at an angle of about 35 ° with the rolling surface due to shear deformation, and is generated through the crystal grains regardless of the crystal orientation. In the phosphor bronze containing 8% Sn described above, the decrease in r (220) in the region of σ _B ≧ 750 MPa is considered to be due to the generation of a shear band.
[0010]
The present inventors presumed that if the development of the shear band was suppressed, the bendability was improved, and the phosphor bronze with the orientation indicated by ▲ in FIG. 1 was obtained by optimizing the rolling conditions. That is, in phosphor bronze containing 8% Sn, r (220) was successfully maintained at a level of 70% or more in the range of σ _B ≧ 750 MPa. As shown by Δ in FIG. 1, the bending workability of this phosphor bronze was clearly superior to that of phosphor bronze rolled in the conventional manner. The following factors can be considered for rolling conditions that suppress the development of shear bands:
-Rolling oil: Low viscosity is good.-Rolling temperature: Higher is better.-Degree of processing in each plate: Lower is better.-Rolling roll: Smaller diameter is better.
[0011]
The present inventors collected similar data for phosphor bronze with different Sn concentrations and analyzed this data. As a result, for phosphor bronze with a Sn content of 3.5 to 11.0 mass%, the range of σ _B that causes shear band development and significant decrease in bendability due to the decrease in r (220) is Sn mass concentration ([% Sn ])
σ _B ≧ 550 + 25 [% Sn]
I found that it is given in relation to. In addition, as in the case of 8% Sn, it has been found that if r (220) is controlled to 70% or more, bendability superior to that of conventional phosphor bronze can be obtained.
[0012]
The present invention has been made based on the above findings.
(1) Processed to a thickness of 0.4 mm or less by rolling, Sn: 9.0 to 11.0% by mass, P: 0.03 to 0.35% by mass, balance of Cu and inevitable impurities, tensile The strength (σB (MPa)) is related to the mass% concentration of Sn ([% Sn]),
σB ≧ 550 + 25 [% Sn]
In the copper alloy strip in the range of (2), the phosphor bronze strip characterized in that the composition ratio (r (220) (%)) of the (220) plane defined by the following formula is 70% or more,
r (220) = I (220) / (I (220) + I (111) + I (200) + I (311)) × 100
(I (hkl) is the integral value of the X-ray diffraction intensity of the (hkl) plane when measured using a Co tube).
(2) The phosphor bronze strip according to (1), which is processed by cold rolling and finally subjected to strain relief annealing.
(3) Terminals and connectors using the phosphor bronze strips of (1) and (2).
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Details of the present invention will be described below.
Aggregation degree of (200) plane on the rolled surface The phosphor bronze of the present invention has an aggregation degree r (220) of (220) plane of 70% or more in the range of σ _B ≧ 550 + 25 [% Sn]. It is characterized by that. The r (220) value in this case is an index of the degree of occurrence of the shear band. When r (220) is lower than 70%, bending workability is not improved, so r (220) is specified to be 70% or more.
[0014]
Sn concentration The above relationship is established when the Sn concentration is in the range of 3.5 to 11.0%. The higher the Sn concentration in this range, the higher the strength can be obtained with the same bending workability. Therefore, it is effective to increase the Sn concentration as a means to improve the strength without reducing the bendability, but the raw material cost is increased, the conductivity is decreased, and the Sn segregation of the ingot becomes prominent and the productivity is increased. There are problems such as lowering. Therefore, the Sn concentration is determined in consideration of various characteristics required for the material, allowable cost, and the like.
Phosphor bronze is classified according to Sn concentration within the Sn concentration range of 3.5 to 11.0% by mass, and is standardized by JIS and ASTM. For example, the range of σ _B in which the present invention is effective for each phosphor bronze is as follows.
(1) C5111 (JIS): When [% Sn] = 4, σ _B ≧ 650
(2) C5102 (JIS): When [% Sn] = 5, σ _B ≧ 675
(4) C5191 (JIS): [% Sn] = 6 and σ _B ≧ 700
(5) C5210, C5212 (JIS): When [% Sn] = 8, σ _B ≧ 750
(6) C52400 (ASTM): When [% Sn] = 10, σ _B ≧ 800
[0015]
P concentration
The P concentration is in the range of 0.03 to 0.35 mass% in accordance with the standards of JIS and ASTM. If the P concentration is too low, when the phosphor blue ingot is melted, the deoxidation of the molten metal becomes insufficient, the viscosity of the molten metal becomes high, and it becomes difficult to produce a healthy ingot. Further, even if the strip can be manufactured, coarse oxide inclusions are generated, and the bendability deteriorates. On the other hand, if the P concentration is too high, the electrical conductivity decreases.
[0016]
Application to phosphor bronze containing trace alloy elements σ _B ≧ 550 + 25 [% Sn] In the range of controlling r (220) to 70% or more, the effect of improving bendability is Fe, Ni, Co, Zn It can also be found in phosphor bronze in which a small amount of alloying elements such as are added and the characteristics are fine-tuned. However, when the addition amount of the alloy element exceeds 0.5 mass%, a change that cannot be ignored appears in σ _B and r (220). Therefore, the range of the alloy element amount to which the present invention can be applied is 0.5 mass% or less.
[0017]
Effect of strain relief annealing The bending workability of the rolled material of phosphor bronze is improved by performing strain relief annealing. Therefore, if increase in manufacturing cost is allowed, it is desirable to perform strain relief annealing.
[0018]
Thickness If the thickness of the strip is greater than 0.4 mm, fine bending becomes difficult, so the thickness of the material is limited to 0.4 mm or less.
[0019]
【Example】
The various phosphor bronze materials shown in Table 1 were evaluated for tensile strength and bending workability. The P concentration of these phosphor bronzes is adjusted in the range of 0.10 to 0.15 mass% where P does not affect the bendability. In the evaluation of the tensile strength, a tensile test was performed in parallel with the rolling direction using JIS No. 5 tensile test piece in accordance with JIS Z2241.
[0020]
In the evaluation of bending workability, according to the Japan Copper and Brass Association technical standard “Bending workability evaluation method for copper and copper alloy thin plates” (JBMA, T307 (1999)), the width 10 mm, length taken in the Bad way direction A 50 mm sample was subjected to W bending with various bending radii. However, in FIG. 1, the minimum bending radius at which cracks do not occur was obtained, but in this evaluation, the appearance of the bending portion at a predetermined bending radius ratio (bending radius / plate thickness: expressed in r / t) is shown in FIG. Ranked A to E. Further, F was given when the sample was broken and the surface of the bent portion could not be observed.
[0021]
In X-ray diffraction for evaluation of r (220), RINT2500 manufactured by Rigaku Corporation was used as an X-ray diffractometer, a Co tube (λ = 17.899 nm) was used, tube voltage: 30 kv, tube current: 100 mA, divergence slit: 1 °, scattering slit: 1 °, receiving slit: 0.3 °, divergence longitudinal limiting slit: 10 mm, monochrome receiving slit: 0.8 mm, scanning speed: 7 ° / min, step width: 0.02 ° Measurement was performed under the conditions. The range of 2θ in which the diffraction intensity was measured on each surface (θ is the diffraction angle) is (111): 48.0-53.0 °, (200): 56.0-61.0 °, (220): 85.5-90.5 °, (311): The integrated value of diffraction intensity was determined at 106.0 to 111.0 °. The above conditions are the same in the measurement of FIG.
[0022]
[Table 1]

[0023]
The evaluation results of each sample are shown in Table 1. Corresponding data is divided into groups 1 to 7 and displayed. When compared among the groups, it is clear that the bending workability of the phosphor bronze of the present invention is superior to that of the comparative example which is a conventional phosphor bronze. It can also be seen that bendability is improved by performing strain relief annealing.
When Group 1 and Group 2 are compared, it can be seen that when the tensile strength is the same, the higher the Sn concentration, the better the bendability. Further, when comparing the group 3 and the group 5, it can be seen that the tensile strength can be increased without decreasing the bendability by increasing the Sn concentration. If Sn is increased in this way, the strength can be improved without impairing the bendability, but the conductivity decreases as the Sn concentration increases, and if Sn exceeds 11% by mass, which is the upper limit in the present invention, the conductivity is increased. The rate is below 10% IACS.
[0024]
【The invention's effect】
When increasing the degree of rolling and increasing the strength of phosphor bronze, the bendability is significantly deteriorated when the strength exceeds a predetermined level. This phenomenon is caused by the generation of a shear band, and when the shear band occurs, a characteristic change appears in the crystal orientation. Based on the above findings, we succeeded in obtaining phosphor bronze having both high strength and good bendability by controlling the crystal orientation. The phosphor bronze of the present invention is suitable as a material for terminals and connectors used in small electronic components. The phosphor bronze of the present invention is extremely useful industrially because the properties other than strength and bendability are equivalent to those of conventional phosphor bronze.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the tensile strength of phosphor bronze, the degree of assembly of (220) orientation, and bending workability.
FIG. 2 is a diagram showing an evaluation standard for the appearance of a bent portion (Japan Copper and Brass Association Technical Standard T307 (1999)).

Claims (3)

It is processed to a thickness of 0.4 mm or less by rolling, Sn: 9.0 to 11.0 mass%, P: 0.03 to 0.35 mass%, the balance is made of Cu and inevitable impurities, and tensile strength ( σB (MPa)) is related to the mass% concentration of Sn ([% Sn]),
σB ≧ 550 + 25 [% Sn]
In the copper alloy strip in the range of (2), the phosphor bronze strip characterized in that the composition ratio (r (220) (%)) of the (220) plane defined by the following formula is 70% or more,
r (220) = I (220) / (I (220) + I (111) + I (200) + I (311)) × 100
(I (hkl) is the integral value of the X-ray diffraction intensity of the (hkl) plane when measured using a Co tube). 2. The phosphor bronze strip according to claim 1, wherein the phosphor bronze strip is finally subjected to strain relief annealing after being processed by cold rolling. A terminal / connector using the phosphor bronze strip according to claim 1.

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