JP2005314779A - Copper alloy material having excellent bending workability and spring property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To find material characteristics with strong correlation to bending workability and the contact pressure in the contact part when worked into a connector terminal regarding a titanium copper based alloy. <P>SOLUTION: Regarding the titanium copper based alloy comprising 2 to 3.5 wt.% titanium, and the balance substantially copper with impurities, after final annealing, the difference between the compressive proof stress and tensile proof stress in a direction parallel to the rolling direction is controlled to ≤50 MPa, and the difference between the compressive proof stress and tensile proof stress in a direction orthogonal to the rolling direction is controlled to ≤200 MPa. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a metal material manufactured based on a method of evaluating bending workability and spring property of a metal material pressed for electronic parts such as connector terminals.

  Titanium copper is particularly excellent in mechanical strength among copper alloys, and has recently been used for connector terminals that require high strength in the field of electronic components. On the other hand, along with the downsizing and higher density of electronic equipment, electronic components are becoming lighter, thinner and shorter, and it is important to obtain sufficient contact pressure from the viewpoint of connector terminal reliability. ing.

JP 2001-279347 A

Under these circumstances, when selecting a material for a connector terminal, a sample is often taken from a parallel direction of rolling of the material, a tensile test is performed, and a material having high yield strength, tensile strength, and elongation is often selected. For example, in Patent Document 1, as one of the conditions for obtaining a high-strength copper alloy excellent in bending workability and heat resistance, the yield strength obtained by a tensile test in which a test piece is taken from a direction parallel to the rolling direction is 480 N / mm ² or more.

JP 2001-294957 A JP 2001-303158 A JP 2002-266042 A 2000 Plastic Processing Spring Lecture Proceedings (2000) P209-P210

Patent Document 2 pays attention not only to the direction parallel to the rolling direction of the material but also to the characteristics in the direction perpendicular to it, to obtain a copper alloy for connectors that is low in cost, high in strength, excellent in electrical conductivity, and good in pressability. one condition, 0.2% proof stress obtained by a tensile test taken test pieces from parallel direction and a perpendicular direction to the rolling direction 600N / mm ² or more, as the tensile strength is 650 N / mm ² or more Yes. Further, in Patent Document 3, one of the conditions for obtaining a copper alloy wrought material with low anisotropy and excellent bending workability has a tensile strength of 800 N / mm ² or more after aging treatment, and the rolling parallel direction and rolling The anisotropy represented by the difference in tensile strength in the perpendicular direction is 30 N / mm ² or less. Further, in Patent Document 4, as one of the conditions for obtaining a copper alloy sheet having excellent bending workability, the proof stress obtained by a tensile test in which test pieces are taken from a direction parallel to and perpendicular to the rolling direction is 450 N / mm ^2. As described above, the ratio between the proof stress and the tensile strength is set to 0.95 or less.

  As mentioned above, although the example of a prior art has been shown, all are paying attention only to the tensile property of material.

  However, when the material is processed into a connector terminal, the bending part is subject to tensile deformation on one side of the part closest to the outermost surface, and compressive deformation is applied to the outermost layer opposite to the one near the outermost surface. Is added. Therefore, when bending is applied to the material, both the tensile and compressive deformation occurs in the bent part, so the bending property to the connector terminal and the contact pressure of the contact part can be accurately determined only by the tensile properties of the material. It cannot be said that it can be predicted.

  Under such circumstances, many trials and errors have conventionally been required to determine the optimum material and processing conditions by press working, contact pressure test of the contact portion, and the like.

  Therefore, the object of the present invention is to clarify the material properties of titanium copper, which is a copper alloy excellent in mechanical strength, which has a close correlation with the bending workability and the contact pressure of the contact part when processed into a connector terminal. Provides a method for evaluating the bendability and springiness of metal materials, and further clarifies the material properties that are closely correlated with the bendability and contact pressure of the contact part when processed into connector terminals. It is to provide titanium copper excellent in contact pressure stability of a contact portion when being processed into a bendability and a connector terminal.

  As a result of diligent research on the existing titanium-copper alloy, whether or not there is a material characteristic that has a stronger correlation than the conventional method with respect to the bending workability and the contact pressure of the contact portion when processed into a connector terminal, It has been found that the tensile and compressive properties in the direction parallel to and perpendicular to the rolling direction have a great influence on the bendability to the connector terminal and the contact pressure of the contact part.

Based on this knowledge, the inventor created the following invention.
(1) About titanium copper alloy containing 2.0 mass% or more and 3.5 mass% or less of titanium, and the balance substantially consisting of copper and impurities, after final annealing, the difference between the compression proof strength and the tensile strength in the rolling parallel direction A titanium-copper alloy having excellent spring properties, characterized in that the difference between the compression proof strength and the tensile proof strength in the direction perpendicular to the rolling is 200 MPa or less.

Here, the final annealing condition can be arbitrarily set as long as it is within the range of the tensile proof strength and the compressive proof strength satisfying the present invention.
The present invention is characterized in that the tensile strength and compression strength of the titanium-copper alloy are determined within an appropriate range for the purpose of obtaining bending workability suitable for use as a connector terminal and contact pressure of the contact portion. .

  As is apparent from the above description, according to the present invention, a titanium-copper alloy for electronic materials that is superior in bending workability as compared with the prior art can be obtained. Furthermore, when processed into a connector terminal, a titanium-copper alloy for electronic materials that can provide a stable contact pressure to the contact portion is obtained.

  The reason why the Ti concentration and the ranges of tensile strength and compression strength are limited in the present invention will be described below.

(1) Ti concentration Ti undergoes spinodal decomposition when Cu-Ti alloy is subjected to aging treatment to produce a modulation structure of concentration in the base material, thereby providing very high strength, but its content is 2 If less than 0.0%, the desired strengthening cannot be expected. On the other hand, if Ti exceeds 3.5%, precipitation at the grain boundary reaction type is likely to occur, conversely leading to a decrease in strength or deterioration of workability. Or Therefore, the Ti content is set to 2.0 to 3.5% by mass.

(2) Titanium copper alloy after final annealing In the titanium copper alloy after final annealing, the difference between the tensile strength and compression strength in the rolling parallel direction is 50 MPa or more, or the difference between the tensile strength and compression strength in the direction perpendicular to the rolling is 200 MPa. In the above, when bending the connector terminal, “the plastic deformation occurs on the bending compression side or the tension side” or “the crack occurs on the bending tension side”, so the inner bending radius of the bending portion becomes smaller or the contact portion This causes a problem that a predetermined contact pressure cannot be obtained. Therefore, the difference between the tensile strength and the compression strength in the rolling parallel direction is 50 MPa or less, and the difference between the tensile strength and the compression strength in the direction perpendicular to the rolling is 200 MPa or less.

Hereinafter, embodiments of the present invention will be described.
Titanium copper alloys having the compositions shown in Table 1 and Table 2 were melted and cast in a vacuum melting furnace to produce an ingot having dimensions of width 100 mm × thickness 40 mm × length 150 mm. The ingot is homogenized and annealed at 850 ° C. for 1 hour in the air, and then hot rolled. During hot rolling, the material surface temperature is measured with a two-color radiation thermometer, and when it reaches a predetermined temperature, it is cooled with water. Furthermore, after the solution treatment at 1173 K (900 ° C.) for 1 hour, the surface is shaved, and then cold rolling and annealing are repeated several times as necessary, and the strain relief annealing is performed after the final cold rolling, A plate material having a thickness of 0.2 mm was obtained.

  And various test pieces were extract | collected from the board | plate material obtained by performing a series of said processing and heat processing, and the evaluation shown below was performed.

(Evaluation of tensile strength / compression strength)
Tensile strength / compression strength was evaluated by taking a No. 5 test piece (JIS Z 2201) from a direction parallel to the rolling direction and a direction perpendicular to the rolling direction, and conducting a tensile / compression test. FIG. 1 is an explanatory diagram showing an outline of a tensile / compression test.

The comb-shaped dies 1 and 2 are composed of parts 2a and 2b and parts 1a and 1b.
The components 2a and 2b have comb-tooth shaped portions 2g and 2h, are slidably fitted to each other, and can move slightly in a straight line in the direction 5 in which the tension / compression force acts. Further, the parts 2a and 2b have pins 2c, 2d, 2e and 2f which protrude in a direction perpendicular to the direction 5 in which the tension / compression force acts.

  The parts 1a and 1b have comb-like portions 1g and 1h, are slidably fitted to each other, and can slightly move linearly in the direction 5 in which the tension / compression force acts. The parts 1a and 1b have engagement holes 1c, 1d, 1e and 1f, respectively.

A part in which a Teflon (registered trademark) sheet 4b, a tensile test piece 3, and a Teflon (registered trademark) sheet 4a are sequentially stacked between the parts 2a and 2b and the parts 1a and 1b are sandwiched between the pins 2c, 2d, 2e, 2f is inserted into the engagement holes 1c, 1d, 1e, and 1f, respectively, and engaged. Then, the assembling force 6 is applied to couple the parts 2a and 2b and the parts 1a and 1b.
It attached to the hydraulic cylinder in such a state, and performed the tension / compression test.

(Evaluation of bending workability)
The bending workability was evaluated by collecting strip-shaped test pieces from a direction parallel to and perpendicular to the rolling direction, and then performing a W bending test (JIS H 3130) under the condition of bending radius / sheet thickness = 2. By observing the part with an optical microscope, the degree of rough skin and the presence or absence of cracks were investigated and evaluated. The evaluation results are: ◎: very good (no cracking and surface gloss), ○: excellent (no cracking), △: slightly inferior (significant skin roughness), × : Inferior (cracking occurred).

(Contact contact pressure evaluation)
The contact pressure evaluation of the contact part is shown in the figure after taking a strip-shaped test piece having a width of 0.8 mm × 20 mm from a direction parallel to and perpendicular to the rolling direction and then press-bending into the shape shown in FIG. Evaluation was made by the pressure when the contact portion 7a was pushed down by 1.0 mm. The evaluation results are as follows: ◎: very good (pressure when the contact part is pushed down by 1.0 mm is 55 g or more), ○: excellent (pressure when the contact part is pushed down by 1.0 mm is 50 g or more and 55 g) Less than), x: inferior (pressure when the contact part is pushed down 1.0 mm is less than 50 g).

In Table 1, Example No. Nos. 1 to 5 are titanium copper alloys of the examples according to the present invention according to claim 1. 6 to 9 are titanium copper alloys of comparative examples.
Example No. For 1 to 5, the difference obtained by subtracting the compression proof strength from the tensile proof strength in the rolling parallel direction is −40, −48, −24, −14, and −19 MPa, respectively. Of the present invention is within the range of 50 MPa or less, and the difference obtained by subtracting the compression strength from the tensile strength in the direction perpendicular to the rolling is −68, −94, −79, −69, −, respectively. The absolute value of each is in the range of 200 MPa or less.

On the other hand, Comparative Example No. 6, the difference obtained by subtracting the compressive strength from the tensile strength in the rolling parallel direction is −9 MPa, and the difference obtained by subtracting the compressive strength from the tensile strength in the direction perpendicular to the rolling is −54 MPa. However, the Ti concentration is 1.8%, which is outside the range of 2.0 to 3.5% defined in the present invention of claim 1, and sufficient strength cannot be obtained. The contact pressure is insufficient.
Comparative Example No. For No. 7, the difference obtained by subtracting the compression strength from the tensile strength in the rolling parallel direction is −55 MPa, and the absolute value of 55 MPa is out of the range of 50 MPa or less as defined in the first aspect of the present invention. Therefore, bending workability in the rolling parallel direction is poor.
Example No. For No. 8, the difference obtained by subtracting the compression strength from the tensile strength in the direction perpendicular to the rolling is −210 MPa, and the absolute value of 210 MPa is outside the range of 200 MPa or less defined in the present invention of claim 1. The bending workability in the perpendicular direction is poor.
In Example 9, the Ti concentration was 3.8%, which was outside the range of 2.0 to 3.5% defined in the present invention of claim 1, and the hot workability was poor, and evaluation was not possible.

It is explanatory drawing which shows the outline | summary of a tension | pulling / compression test. It is a figure which shows the outline | summary of the contact pressure evaluation of a contact part.

Explanation of symbols

1 Comb-like die 1a Part 1b Part 1c Engagement hole 1d Engagement hole 1e Engagement hole 1f Engagement hole 1g Comb-like part 1h Comb-like part 2 Comb-like die 2a Part 2b Part 2c Pin 2d Pin 2e Pin 2f Pin 2g Comb tooth 2h Comb tooth 3 Tensile test piece 4a Teflon (registered trademark) sheet 4b Teflon (registered trademark) sheet 5 Direction of action of tension / compression force 6 Assembly force 7a Contact part

Claims (1)

About titanium copper-based copper alloy containing 2.0 mass% or more and 3.5 mass% or less of titanium, and the balance substantially consisting of copper and impurities, after final annealing, there is a difference between the compression proof stress and the tensile proof strength in the rolling parallel direction. A titanium copper-based copper alloy having excellent spring properties, characterized in that the difference between the compression proof strength and the tensile proof strength in the direction perpendicular to the rolling is 50 MPa or less and 200 MPa or less.