JP2016199792A - Copper alloy wire material for spring, manufacturing method of the copper alloy wire material for spring, spring and manufacturing method of the spring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy wire material for springs having (1) high strength for maintaining high contact pressure, (2) high conductivity for transmitting current without loss, (3) high thermal conductivity for releasing heat generated in a semiconductor and (4) settling resistance due to heat in good balance.SOLUTION: There is provided a copper alloy wire material for springs containing Ni of 3.4 to 4.2 mass%, Si of 0.7 to 1.0 mass%, Zn of 0.4 to 0.6 mass%, Sn of 0.1 to 0.5 mass%, Mg of 0.05 to 0.25 mass% and the balance copper with inevitable impurities and having an average crystal particle diameter of over 5 to 50 μm, an average size of Ni-Si intermetallic compounds of 5 to 50 nm, a tensile strength of 800 to 1100 MPa and a conductivity of 30 to 45%IACS.SELECTED DRAWING: None

Description

  The present invention relates to a copper alloy wire for a spring having high conductivity, thermal conductivity, high strength, and excellent sag resistance used in a large current field such as an in-vehicle application, and a method for producing the copper alloy wire for a spring. And a spring, and a method of manufacturing the spring.

  In recent years, compared to the rate of increase in vehicles (cars, buses, trucks, etc.) driven only by gasoline engines and diesel internal combustion engines, hybrid vehicles driven by using an electric motor together with electricity driven only by an electric motor The increase rate of various drive systems such as automobiles is higher, and many drive systems have been proposed and put into practical use.

  Among them, the method using an electric motor drive is controlled with a high voltage of several hundred volts for the purpose of improving its efficiency and a frequency of several hundred to several thousand hertz for the purpose of performing fine control at the same time. Current is used.

  A so-called power semiconductor generates the current, and for example, an IGBT (Insulated Gate Bipolar Transistor) is mounted on these vehicles. The IGBT is excellent in that it can operate at high speed, has a high breakdown voltage, and a low on-resistance, and has a function of converting direct current into alternating current or alternating current into direct current.

  The IGBT is an aggregate of power semiconductors, and conventionally, electrical connection with an external circuit has been ensured by soldering or wire bonding to the plurality of power semiconductors. However, there are demands for technologies such as countermeasures against the environmental impact of substances contained in solder, and reduction of assembly and replacement man-hours by wire bonding. Therefore, instead of soldering or wire bonding, electrical connection using a terminal using a spring has been studied. However, the electrical connection using a conventional spring terminal is low in reliability in terms of the performance of the spring, and the spring terminal is used. Few examples have adopted electrical connections. This is because the spring wire used for the above electrical connection cannot ensure sufficient conductivity (low resistance) and long-term spring property (sag resistance), resulting in high reliability. This is because there is a problem that electrical connection cannot be secured. In recent years, therefore, research on spring wires having both high conductivity and sag resistance has been underway.

  Conventionally, it has been known that copper and copper alloys having excellent conductivity are advantageous as an example of a material for a spring wire used for electrical connection as described above. For example, JIS C1100W, which is pure copper, is called tough pitch copper and exhibits excellent conductivity and is 100% IACS (International Annealed Copper Standard), but a tensile strength of only about 200 MPa to 250 MPa is obtained. On the other hand, JIS-C2600W, a copper alloy, is called brass, and although the tensile strength exceeds 1000 MPa for a material that has been subjected to strong processing, the electrical conductivity is only 28% IACS. Similarly, JIS C5191W (phosphor bronze) also has low conductivity. Note that JIS C1100W, C2600W, and C5191W also have sag due to the heat generated by the power semiconductor. Therefore, materials other than these pure copper and copper alloys are necessary.

In addition to the above pure copper and copper alloy, stainless steel, titanium alloy, and the like were also candidates for spring wires, but these have higher strength than copper alloys and the like, but their conductivity is extremely low.
In addition, as vehicle control becomes more complex and faster in recent years, it is necessary to take measures against heat generated by high-speed switching of power semiconductors.

The characteristics required for a spring wire used for electrical connection between a power semiconductor in a vehicle and an external circuit are summarized as follows. (1) high strength for maintaining high contact pressure, (2) high conductivity for passing current without loss, (3) high thermal conductivity for releasing heat generated in the semiconductor, and (4 ) Heat sag resistance. Therefore, having these in a well-balanced state is considered to be the optimum material used in the spring wire. In the case of a copper alloy, the electrical conductivity and the thermal conductivity are proportional to each other by the following formula based on the Viehman Franz law. Therefore, the above (2) and (3) can be regarded as equivalent characteristics.
λ / σ = LT
(Where λ: thermal conductivity, σ: electrical conductivity, L: Lorentz number, T: absolute temperature)

  In addition, heat sag or sag resistance can be rephrased as thermal creep characteristics or stress relaxation characteristics, and can be regarded as synonymous terms and equivalent functions. Therefore, in this specification, as an evaluation of the sag resistance due to the above (4) heat, a numerical value was obtained by a load loss test.

  As a result of investigating a commercially available copper alloy as to whether the above four characteristics can be satisfied, it was determined that a Cu—Ni—Si based alloy (Corson copper) was excellent in all characteristics. Cu-Be alloy (beryllium copper) may also satisfy these characteristics. However, when Cu-Be alloy is burned in the production process or easily discarded, beryllium is formed by oxygen in the air. Oxidized to beryllia (beryllium oxide). According to the International Chemical Safety Card, this beryllia is a carcinogen and is extremely toxic to aquatic organisms and is considered one of the environmentally hazardous substances.

  Therefore, the inventors focused on a commercially available Cu—Ni—Si alloy, but the alloys satisfying the characteristics required by the inventors and the values serving as the evaluation criteria are commercially available (conventional) Cu— It was not found in Ni-Si alloys. Therefore, the present inventors have focused on the Cu—Ni—Si based alloy and have advanced the material development of the Cu—Ni—Si based alloy satisfying each characteristic.

  The following are proposed as a conventional spring wire made of a Cu—Ni—Si alloy and a spring around which the wire is wound.

  For example, in Japanese Patent No. 417726, a wire is a Cu—Ni—Si alloy having a conductivity of 20 to 60% IACS and a tensile strength of 1000 MPa to 1300 MPa. The characteristic which is excellent in the stress relaxation resistance is described. In order to achieve these properties, solution treatment → aging treatment, solution treatment → aging treatment → wire drawing, solution treatment → wire drawing, solution treatment → wire drawing → aging treatment, solution treatment → Drawing process → Aging process → Drawing process is described. In this solution treatment, the wire is held at 700 to 950 ° C. for 10 minutes or more, more preferably 800 to 950 ° C. for 10 to 180 minutes, and further preferably 850 to 950 ° C. for 10 to 120 minutes. ing.

  Japanese Patent No. 5578991 describes a Cu—Ni—Si alloy having a tensile strength of 1300 MPa or more and excellent stress relaxation resistance and fatigue characteristics. Moreover, in order to achieve these characteristics, solution treatment, wire drawing, and aging treatment are performed. In this solution treatment, the wire is treated at 700 to 950 ° C. for 10 minutes or more, more preferably 800 ° C. or more and 950 ° C. The following is maintained for 10 minutes or more, preferably 10 minutes to 30 minutes.

  Japanese Patent No. 53066591 describes a wire conductor for wiring which is a Cu—Ni—Si alloy and has an average crystal grain size of 2.2 to 5.0 μm and excellent flexibility. In order to reduce the crystal grain size, it is preferably heated to 700 to 1000 ° C., more preferably 800 to 950 ° C., followed by hot extrusion and immediate quenching in water.

  Japanese Patent No. 5520438 describes various copper alloy manufacturing methods, among which are Cu—Ni—Si based alloys. In this production method, a temperature of 800 ° C. or more is 5 seconds or less, then a temperature in the range of 300 ° C. to 600 ° C. is 5 seconds or less, and a temperature in the range of 300 ° C. to 600 ° C. Heat for a run for 1200 seconds. Moreover, it describes that aging treatment can be performed by repeating continuous annealing. In addition, as annealing methods for highly productive wires, there are described running annealing in which a wire is continuously passed through a heated furnace, and current annealing in which current is passed through the wire and annealing is performed by Joule heat generated from itself. Yes.

  Japanese Patent Application Laid-Open No. 2014-196564 discloses a material having a crystal grain size of 5 μm or less and a spring obtained using the material at a heating temperature of 250 to 550 ° C. for 30 hours or less, although the alloy system is different. It includes a stage of an aging treatment in which a rapid treatment is performed at a cooling rate of 30 ° C./sec or more after heating in the above range.

Japanese Patent No. 4177266 Japanese Patent No. 5578991 Japanese Patent No. 53066591 Japanese Patent No. 5520438 JP 2014-196564 A

  However, with any of the techniques described in the above-mentioned patent documents, it is not possible to obtain a copper alloy having the characteristics required by the inventors, and the manufacturing cost is higher than the intentions of the inventors. It was. The reason is as follows.

  First, in the technique of Japanese Patent No. 4177266, in order for the tensile strength to exceed 1000 MPa, it is necessary to perform strong processing until the crystal grain size is 5 μm or less. On the other hand, the crystal grain size correlates with sag resistance, and when the crystal grain size is 5 μm or less, sag resistance cannot be satisfied. Therefore, in this technique, it is not possible to obtain both desired tensile strength and sag resistance, and in this solution treatment, it is necessary to heat the wire at a high temperature for 10 minutes or more, resulting in high costs. .

  Similarly, even in the technology of Japanese Patent No. 5578991, in order for the tensile strength to exceed 1300 MPa, it is necessary to perform strong processing until the crystal grain size is 5 μm or less. On the other hand, the crystal grain size correlates with sag resistance, and when the crystal grain size is 5 μm or less, sag resistance cannot be satisfied. Therefore, in this technique, it is not possible to obtain both desired tensile strength and sag resistance, and this solution treatment requires heating the wire at a high temperature for 10 minutes or more, resulting in high costs.

  In the technique of Japanese Patent No. 5306591, the crystal grain size is 5 μm or less, and the sag resistance cannot be satisfied.

  In the technique of Japanese Patent No. 5520438, continuous annealing is repeated, and in the embodiment, a long heat treatment time of 900 seconds is required, resulting in high cost.

  The technique disclosed in Japanese Patent Application Laid-Open No. 2014-196564 relates to an alloy other than a Cu—Ni—Si alloy, and cannot be used as a reference for the present invention.

  In view of the above problems, the object of the present invention is (1) high strength for maintaining high contact pressure, (2) high conductivity for passing current without loss, and (3) generated in a semiconductor. Provided are a copper alloy wire for springs having a high thermal conductivity for escaping heat and (4) heat sag resistance in a balanced manner, a method for producing the copper alloy wire for springs, a spring, and a method for producing the spring There is to do.

  Here, we define the sag resistance. Since sag resistance is a characteristic that is difficult to quantify, it was evaluated in this specification by measuring load loss.

The present inventors have conducted extensive research and development to newly discover the relationship between sag resistance and crystal grain size, and as a result of various studies, the copper alloy wire for springs that achieves the above-described object Is as follows.
(1) Ni is contained in 3.4 to 4.2% by mass, Si is contained in 0.7 to 1.0% by mass, Zn is contained in 0.4 to 0.6% by mass, and Sn is contained in 0.1 to 0.5%. A copper alloy wire for springs comprising 0.05% to 0.25% by mass of Mg and 0.05% by mass of the balance, copper and inevitable impurities,
The average crystal grain size is more than 5 μm and not more than 50 μm, the average size of the Ni—Si intermetallic compound is 5 nm to 50 nm,
A copper alloy wire for springs having a tensile strength of 800 MPa to 1100 MPa and an electrical conductivity of 30 to 45% IACS.
(2) The copper alloy wire for a spring according to the above (1), containing 0.03 to 1.0% by mass in total of one or more of Cr, Mn, Zr, Fe, Co and Ag.
(3) A spring formed by winding the copper alloy wire for a spring according to the above (1) or (2).
(4) The spring according to (3) above, which is a coil spring or a deformed wire spring.
(5) After applying initial stress to the coil spring according to the above (4) and temporarily loading it, the initial stress is applied again and held at 150 ° C. for 1000 hours, and then the load loss is 20% or less. A spring characterized by
(6) The spring according to (5) above, wherein the initial stress is 400 to 500 MPa.
(7) A method for producing a copper alloy wire for a spring according to (1) or (2) above,
After melting and casting, a hot wire is formed to form a rough drawn wire, and then at least each process of solution heat treatment and aging heat treatment is performed,
The solution heat treatment is performed once at 800 to 1000 ° C. for 1 second to 10 seconds,
The method for producing a copper alloy wire for a spring, wherein the aging heat treatment is performed at 300 to 500 ° C. for 0.5 to 5 hours.
(8) A method for manufacturing a spring, further comprising coil processing for forming a spring by winding a wire having a predetermined wire diameter after the solution treatment in the manufacturing method according to (7).

  According to the present invention, in a copper alloy wire for springs having electrical conductivity such as in-vehicle use, (1) high strength to maintain high contact pressure, (2) high conductivity to pass current without loss, ( 3) It is possible to provide a copper alloy having a high balance between high thermal conductivity for releasing heat generated in a semiconductor and (4) sag resistance due to heat.

It is a figure which shows the relationship between the load loss of the spring which concerns on embodiment of this invention, and an average crystal grain diameter. It is a figure which shows the relationship between the load loss and electrical conductivity of the spring which concern on this embodiment, and the relationship between the load loss of the spring which consists of conventional materials, and electrical conductivity. (A)-(f) is a figure which shows the structure of the spring obtained by winding the copper alloy wire for springs which concerns on this embodiment. (A)-(e) is a figure which shows the other structure of the spring obtained by winding the copper alloy wire for springs concerning this embodiment. It is a figure explaining the load loss test of the spring concerning this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The shape of the spring copper alloy according to this embodiment is not particularly limited, but “wire” is preferable. When the spring copper alloy is a wire, the wire diameter or equivalent circle diameter is 0.1 to 2.0 mm, preferably 0.5 to 1.0 mm.

(1) Chemical composition and crystal structure [Ni and Si]
By containing 3.4 to 4.2% by mass of Ni and 0.7 to 1.0% by mass of Si in Cu, a compound composed of Ni and Si is produced, and the strength and hardness are improved and the conductivity is increased. Can also recover. It is an element that develops so-called precipitation strengthening. The ratio (Ni / Si) is preferably 3-5. When the Ni content is 3.4 mass% or less and the Si content is 0.7 mass% or less, the precipitation strengthening amount is small. Conversely, when the Ni content is 4.2 mass% or more and the Si content is 1.0 mass% or more, The effect is saturated and cracks in the wire drawing become prominent.

[Zn]
Zn has the effect of preventing the adhesiveness with the solder from being lowered by heating. The effect is insufficient if it is less than 0.4% by mass, and if it exceeds 0.6% by mass, the effect is saturated.
Further, excessive addition causes a decrease in conductivity.

[Sn]
Sn contributes to solid solution strengthening and sag resistance (load loss). If it is less than 0.1% by mass, the effect is not observed, and if it exceeds 0.5% by mass, the conductivity is inhibited.

[Mg]
Mg contributes to solid solution strengthening and sag resistance (load loss). If it is less than 0.05% by mass, the effect does not appear, and if it exceeds 0.25% by mass, the effect is saturated. Further, the addition of Mg has an effect of preventing cracking of the ingot at the time of casting, and this addition amount is optimal for the effect.

[Cr, Mn, Zr, Fe, Co and Ag]
As an optional component, one or more of Cr, Mn, Zr, Fe, Co, and Ag may be added in the range of 0.03 to 1.0 mass% in total. These elements contribute to the improvement of properties by solid solution strengthening. If it is less than 0.03% by mass, the effect is not recognized, and if it is 1.0% by mass or more, the conductivity is lowered.

[Average crystal grain size]
The crystal grain size is related to sag resistance (load loss). In the present embodiment, if the average value of the crystal grain size (average crystal grain size) is 5 μm or less, the sag resistance (load loss) deteriorates, and if it exceeds 50 μm, the desired strength cannot be obtained. Therefore, the average crystal grain size is more than 5 μm and not more than 50 μm.

[Average size of Ni-Si precipitates]
The average size of the Ni—Si precipitate is 5 nm to 50 nm. If the average size of the Ni—Si precipitates is less than 5 nm, the electrical conductivity is low and the desired strength cannot be obtained, and if it exceeds 50 nm, the desired strength cannot be obtained. Here, the size refers to the length of the major axis when the cross section of the Ni—Si precipitate is viewed, and the average size is the average value.

(2) Properties of spring copper alloy wire [Tensile strength]
In order to obtain the optimum characteristics as a spring material, the strength is insufficient when it is less than 800 MPa, and when it exceeds 1100 MPa, the deterioration of sag resistance shown below is remarkable. Accordingly, the tensile strength is set to a value within the range of 800 MPa to 1100 MPa. In order to obtain this characteristic, the Ni—Si precipitate has an average size of 5 nm to 50 nm and an average crystal grain size of more than 5 μm and 50 μm or less.

[conductivity]
If the conductivity is 30% IACS or less, the effect of releasing the heat is insufficient. Of course, the higher the electrical conductivity, the better. However, in the case of a Corson alloy, when it becomes 45% IACS or more, the average size of the Ni-Si compound becomes larger than 50 nm, and the balance with the strength becomes worse. Therefore, the conductivity is set to a value within the range of 30 to 45% IACS.

[Load loss]
A spring load loss test is performed to quantify the sag resistance. In this embodiment, it is set as the environmental conditions of initial stress 400-500 MPa, 150 degreeC, and 1000 hours. The load loss is calculated using the formula (1) described later, and if it is 30% or less, it is sufficient as a copper alloy wire for a spring.

  A plot of the relationship between spring load loss and average grain size is shown in FIG. In the figure, it can be seen that the load loss tends to decrease as the average crystal grain size increases, and in particular, the load loss is as low as 10 to 13% at a particle size of 10 μm or more. Since the copper alloy wire for springs of this embodiment has an average crystal grain size exceeding 5 μm, the load loss can be 20% or less.

FIG. 2 is a diagram showing the relationship between the load loss of the spring and the conductivity. In the figure, a group G1 shows a representative example of this embodiment.
Group G2 represents beryllium copper, which is a conventional material, and group G3 represents Elemetal (registered trademark), which is a conventional material. Other plots are other Corson alloys which are conventional materials other than the Corson alloy of this embodiment.

  As shown in FIG. 2, in order to increase the conductivity, it is generally necessary to select a component close to pure copper, and broken lines A to C (broken line A: average crystal grain size 0.2 μm, broken line B: average crystal) As shown by a grain size of 1 μm, a broken line C: an average crystal grain size of 4 μm), when the crystal grain size is the same, spring sag, that is, load loss tends to increase. On the other hand, in this embodiment, as shown in the figure, a low load loss can be achieved while securing a higher conductivity than that of the conventional material, and the application can be greatly expanded.

(3) Copper alloy wire for spring and method for producing spring The copper alloy wire for spring and the method for producing the spring of the present embodiment include [1] melting, [2] casting, [3] hot working, [4] elongation. Manufacturing method including sequentially performing each step of wire processing, [5] first heat treatment (solution heat treatment), [6] cold work, [7] second heat treatment (aging heat treatment) and [8] coil processing Can be manufactured.

[1] Melting Melting is performed by adjusting the amount of each component so that the copper alloy composition described above is obtained.

[2] Casting and [3] Hot working The melting casting temperature is desirably 1200 to 1300 ° C., and a cylindrical billet having a diameter of 100 mm to 300 mm is manufactured. Subsequently, after hold | maintaining at 800-1000 degreeC for 1 hour-5 hours, it processes to a diameter of 10-50 mm (rough drawing line) with a hot extruder.

[4] Wire drawing The wire drawing and surface grinding (peeling) are performed at least once to finish, for example, a wire having a wire diameter or equivalent circle diameter of 0.5 to 2.6 mm.

[5] First heat treatment (solution heat treatment)
Heat treatment (solution heat treatment) is performed once at a temperature of 800 to 1000 ° C. for 1 to 10 seconds. At 800 ° C. or lower, recrystallization does not occur and the crystal grain size varies greatly. Above 1000 ° C., the particle size becomes coarser than the desired size, and fine cracks and patterns on the surface are generated in the next wire drawing step. Similarly, recrystallization does not occur in 1 second or less, and coarsening occurs in 10 seconds or more. In terms of productivity, production efficiency and energy saving, it is performed in 10 seconds or less, and it is also performed once.

  This heat treatment is desirably performed by continuous annealing. Continuous annealing is a highly productive annealing method of wire rods, and is a running annealing in which a wire rod is continuously passed through a heated furnace, or a current annealing in which an electric current is passed through a wire rod and annealing is performed by Joule heat generated from itself.

[6] Cold working (drawing)
Then, cold working can be performed at a working rate of 0 to 99% to form a wire. The cold working rate is preferably 0 to 90%, and more preferably 0 to 50%. In this cold working, when the crystal grains formed by the solution heat treatment are stretched, the crystal grain diameter in the cross section perpendicular to the wire drawing direction is gradually reduced. That is, the crystal grain size becomes fine and small according to the cross-sectional reduction rate. For example, the crystal grain size at a cold work rate of 50% is reduced to about ½ compared to the case of a cold work rate of 0%. Therefore, a desired crystal grain size can be obtained by selecting an optimum cold working rate.

[7] Second heat treatment (aging heat treatment)
An aging heat treatment is performed at 300 to 500 ° C. on the wire subjected to the first heat treatment (solution heat treatment) and the cold working (drawing). When the cold working rate in the previous step is 0 to 90%, the aging heat treatment temperature is preferably 350 to 450 ° C., and when the cold working rate is 0 to 50%, it is preferably 400 to 500 ° C. At that time, the soaking time (holding time) within ± 10 ° C. is 0.5 hour to 5 hours, preferably 1 hour to 4 hours, more preferably 1 hour to 2 hours.

  When the aging heat treatment temperature is lower than the above temperature range, or when the aging heat treatment time is shorter than the treatment time, desired strength and conductivity cannot be obtained. On the contrary, when the aging heat treatment temperature is higher than the above temperature range, or when the aging heat treatment time is longer than the treatment time, the precipitation state is overaged, and a desired strength cannot be obtained. In this second heat treatment, the crystal grain size does not change.

  Thereafter, cold working (second cold working) may be performed at a working rate of 0 to 90% as necessary. The cold working rate at this time is preferably 0 to 50%.

[8] Coil processing The wire finished to a predetermined wire diameter by the above process is wound to form a spring. Although there is no restriction | limiting in the shape of a spring, It can shape | mold to the coil spring mentioned later, a deformed wire spring, etc.

[Modification of manufacturing method]
Although the manufacturing method of the copper alloy wire for springs was demonstrated, a manufacturing method is not restricted to this, For example, in [5] 1st heat processing-[8] coil processing (henceforth manufacturing process (I)) of the said manufacturing method, [6] Cold working may be omitted. That is, each process may be performed in the order of solution heat treatment → aging heat treatment → coil processing (hereinafter referred to as manufacturing process (II)).

  In the [5] first heat treatment to [8] coil processing of the above manufacturing method, the order of [7] second heat treatment and [8] coil processing may be switched. That is, each process may be performed in the order of solution heat treatment → cold working (drawing) → coil processing → aging heat treatment (hereinafter referred to as manufacturing process (III)). Also in this case, after coil processing, an aging heat treatment is performed at 300 to 500 ° C. for 0.5 to 5 hours. If the temperature and time are out of the ranges, the desired strength cannot be obtained. In addition, the crystal grain size does not change even in the aging heat treatment in the manufacturing method performed in this order. Moreover, it is not necessary to perform the aging heat processing after coil processing according to a use.

  Moreover, in [5] 1st heat treatment-[8] coil processing of the above-mentioned manufacturing method, the order of [6] cold work and [7] 2nd heat treatment may be changed. That is, each process may be performed in the order of solution heat treatment → aging heat treatment → cold processing (drawing) → coil processing (hereinafter referred to as manufacturing process (IV)).

  Further, the spring produced by any one of the above manufacturing methods can be further heat-treated (third heat treatment) in a reducing atmosphere, for example, heat-treated in a nitrogen atmosphere at 400 ° C. for 2 hours. Thereby, it becomes possible to ensure more excellent electrical conductivity and tensile strength.

(4) Structure of spring formed of copper alloy wire for spring The structure of the spring obtained by the copper alloy wire for spring is shown in FIGS. The spring may be a cylindrical coil spring 1 as shown in FIG. 3A or a conical coil spring 2 (FIG. 3B). Moreover, the spring in which a coil diameter changes partially, for example, the drum-shaped coil spring 3 (FIG. 3C) and the barrel-shaped coil spring 4 (FIG. 3D) may be used. Moreover, the elliptical coil spring 5 (FIG.3 (e)) wound by the ellipse may be sufficient. Furthermore, it may be an unequal pitch spring having a varying coil pitch, for example, a single-drawing coil spring 6 (FIG. 3 (f)). The cross-sectional shape of such a coil spring includes a round shape (perfect circle, ellipse) and a square shape, but is not limited thereto.

  The spring obtained by the copper alloy wire for spring is also applied to a deformed wire spring having one end fixed and a load applied to the vicinity of the opposite end, such as a cantilever beam. For example, the spring may be a straight spring 7 (FIG. 4A), a one-stage bending spring 8 (FIG. 4B), or a two-stage bending spring 9 (FIG. 4C). The hook-shaped spring 10 (FIG. 4D) may be used. Further, it may be a double torsion spring 11 (FIG. 4E). The cross-sectional shape of such a deformed wire spring includes, but is not limited to, a square shape, a flat round shape, and a tapered shape.

  Here, the spring index is represented by the ratio (D / d) of the wire diameter or equivalent circle diameter d of the wire to the coil center diameter D, as shown as a representative example in FIG. In the spring of this embodiment, the wire diameter or equivalent circle diameter d is 0.1 mm to 2.0 mm, preferably 0.5 mm to 1.0 mm, and the spring index D / d is in the range of 5 to 15. It is desirable to be. If the wire diameter or equivalent circle diameter d and the spring index D / d are within the above ranges, sufficient performance as a high-strength conductive spring is exhibited.

Examples of the present invention will be described below.
Ni, Si, Zn, Sn, Mg, and selectively added Cr, Mn, Zr, Fe, Co, and Ag are melted so as to have the contents (mass%) shown in Table 1, and melt casting temperature A cylindrical billet having a diameter of 100 mm to 300 mm was manufactured at 1200 to 1300 ° C. Subsequently, after hold | maintaining at 800-1000 degreeC for 1 to 5 hours, it processed into the diameter 10mm-50mm with the hot extruder.

  Wire drawing and surface grinding (peeling) are repeated to finish the wire with a wire diameter or equivalent circle diameter of 0.5 mm to 2.6 mm, and heat treatment of 800 to 1000 ° C., preferably 850 to 940 ° C., 1 to 10 seconds (Solution heat treatment) was performed once.

  Next, aging heat treatment was performed at 300 to 500 ° C. for 0.5 to 5 hours, and final wire drawing was performed to finish a wire having a diameter of 0.5 to 0.8 mm.

  The obtained wire was processed into a coil spring having a predetermined spring index by a dedicated coiling machine.

In addition to the above manufacturing steps, a solution obtained by adding cold working to any of the steps of solution heat treatment, aging heat treatment and coil processing, or changing the order of aging heat treatment and coil processing was performed. . The process from wire preparation to coil is shown below.
(I) Solution heat treatment → Cold working → Aging heat treatment → Coil processing (II) Solution heat treatment → Aging heat treatment → Coil processing (III) Solution heat treatment → Cold working (drawing) → Coil processing → Aging heat treatment (IV ) Solution heat treatment-> aging heat treatment-> cold working (drawing)-> coil processing In any of the above steps, the relationship between the crystal grain size of the material and the load loss of the characteristics could be arranged.

  Further, as comparative examples, coil springs were produced in the same manner as in the above examples, except that the element content and processing conditions were changed to the values shown in Table 2.

Next, Examples and Comparative Examples were measured and evaluated by the following methods.
(A) Tensile strength Tensile strength was measured according to JIS Z 2241. Three samples were measured for each example (comparative example), and the average value was determined. A tensile strength of 800 MPa to 1100 MPa was regarded as an acceptable level.

(B) Conductivity Conductivity was measured according to JIS Z 0505. Three samples were measured for each example (comparative example), and the average value was determined. The electrical conductivity was 30% IACS or more and 45% IACS or less as an acceptable level.

(C) Crystal grain size measurement Crystal grain size measurement was performed in accordance with JIS Z 0501. However, in order to further improve the accuracy, the cutting method described in this JIS was performed on a surface perpendicular to the longitudinal direction of the wire rod and measured. For measurement, an optical microscope (Olympus, device name “GX51”) and a scanning electron microscope (Hitachi, Ltd., device name “SEMEDX TypeM”) are used at an optimum magnification (× 100 to × 1000). The three places were photographed, 50 to 200 crystal grains were measured and analyzed, and the average value was calculated. The average crystal grain size was more than 5 μm and 50 μm or less.

(D) Size measurement of Si-Ni precipitates An observation specimen was prepared using an ultramicrotome (manufactured by Leica, device name “EM UC7”), and a transmission electron microscope (manufactured by JEOL Ltd., device name “JEM”). -3010 "), and photographed 10,000 to 50,000 times, and the average size of 10 to 100 precipitates was binarized with image processing software (manufactured by JEOL Ltd., software name" Image Σ "). I went and asked. The average size of the Ni—Si precipitates was determined to be an acceptable level from 5 nm to 50 nm.

(E) Load Loss Test As shown in FIG. 5, the obtained coil spring A is set in a load tester as a single spring, and the initial stress is set to a predetermined tightening load P1 (actual use stress: 400 MPa). The spring height H1 at that time (hereinafter referred to as the initial spring set height) was measured. Then, after unloading once, the initial stress was reapplied, and the spring was tightened at room temperature using a jig or the like so as to have a height of H1 when actually used. In the set state, it was put into an atmospheric pressure atmosphere at 150 ° C. and held for 1000 hours, then taken out and cooled to room temperature, and then the jig was removed from the set state and unloaded.

The spring was set on the load tester again, and the tightening load P2 after the test at the initial spring set height H1 was measured. From these values P1 and P2, the load loss was calculated using the following formula (1). The load loss was 30% or less as an acceptable level.
(Load loss) = (P1−P2) / P1 × 100 (1)

The results measured by the above method are shown in Tables 1 and 2.

  From Table 1, the following is clear. That is, it was found that all the springs of Examples 1 to 10 exhibited high tensile strength, high electrical conductivity (high thermal conductivity), and high sag resistance, and had these characteristics in a well-balanced manner.

  On the other hand, as shown in Table 2, in Comparative Example 1, the crystal grain size and the size of the precipitate were outside the range of the present invention, the tensile strength was inferior, and the load loss was large. In Comparative Example 2, the solution heat treatment temperature and time were outside the scope of the present invention, the tensile strength and conductivity were inferior, and the load loss was large. In Comparative Example 3, the contents of Ni, Si, Zn and Mg were outside the range of the present invention, the tensile strength was inferior, and the load loss was large. In Comparative Example 4, the content of Ni and Si was outside the scope of the present invention, and processing cracks occurred. In Comparative Example 5, the amount of Sn and Mn added was excessive, the conductivity was inferior, and the load loss was large. In Comparative Example 6, the solution heat treatment temperature and the crystal grain size were outside the scope of the present invention, and the load loss was large.

DESCRIPTION OF SYMBOLS 1 Cylindrical coil spring 2 Cone-shaped coil spring 3 Drum-shaped coil spring 4 Barrel-shaped coil spring 5 Oval coil spring 6 Single-drawn coil spring 7 Straight-shaped spring 8 Single-stage bent spring 9 Two-stage bent-type spring 10 Hook-shaped spring 11 Double torsion spring

Claims (8)

It contains 3.4 to 4.2% by mass of Ni, 0.7 to 1.0% by mass of Si, 0.4 to 0.6% by mass of Zn, 0.1 to 0.5% by mass of Sn, A copper alloy wire for spring comprising 0.05 to 0.25% by mass of Mg, the balance being made of copper and inevitable impurities,
The average crystal grain size is more than 5 μm and not more than 50 μm, the average size of the Ni—Si intermetallic compound is 5 nm to 50 nm,
A copper alloy wire for springs having a tensile strength of 800 MPa to 1100 MPa and an electrical conductivity of 30 to 45% IACS.   The copper alloy wire for springs according to claim 1, comprising 0.03 to 1.0 mass% in total of at least one of Cr, Mn, Zr, Fe, Co, and Ag.   A spring formed by winding the copper alloy wire for a spring according to claim 1 or 2.   The spring according to claim 3, which is a coil spring or a deformed wire spring.   An initial load is applied to the coil spring according to claim 4, and after the initial load is gradually applied, the initial load is applied again, and after holding at 150 ° C for 1000 hours, the load loss becomes 20% or less. And spring.   The spring according to claim 5, wherein the initial stress is 400 to 500 MPa. It is a manufacturing method of the copper alloy wire for springs according to claim 1 or 2,
After melting and casting, a hot wire is formed to form a rough drawn wire, and then at least each process of solution heat treatment and aging heat treatment is performed,
The solution heat treatment is performed once at 800 to 1000 ° C. for 1 second to 10 seconds,
The method for producing a copper alloy wire for a spring, wherein the aging heat treatment is performed at 300 to 500 ° C. for 0.5 to 5 hours. 8. The method for manufacturing a spring according to claim 7, further comprising coil processing for forming a spring by winding a wire having a predetermined wire diameter after the solution treatment in the manufacturing method according to claim 7.

Images