JP6712887B2 - Aluminum alloy wire rod, aluminum alloy stranded wire, coated electric wire and wire harness - Google Patents

Description

The present invention relates to an aluminum alloy wire rod, an aluminum alloy stranded wire, a covered electric wire, and a wire harness used as a conductor of an electric wiring body.

BACKGROUND ART Conventionally, as an electric wiring body of a moving body such as an automobile, a train, an aircraft or the like, or an electric wiring body of an industrial robot, an electric wire including a conductor of copper or a copper alloy, a terminal made of copper or a copper alloy (for example, brass) ( A member called a wire harness, which is equipped with a connector), has been used. In recent years, automobiles have been rapidly improved in performance and functionality, and along with this, the number of mounted various electric devices and control devices has been increased and used in these devices. The number of electric wiring bodies arranged also tends to increase. On the other hand, in order to improve the fuel efficiency of moving bodies such as automobiles for environmental protection, there is a strong demand for weight reduction of moving bodies.

As one of means for achieving the weight reduction of such a moving body, for example, the conductor of the electric wiring body is replaced with the conventionally used copper or copper alloy, and a study has been made on lighter aluminum or aluminum alloy. It is being advanced. The specific gravity of aluminum is about 1/3 of the specific gravity of copper, and the conductivity of aluminum is about 2/3 of the conductivity of copper (when pure copper is taken as the standard of 100% IACS, pure aluminum is about 66% IACS), In order to pass the same current as the copper conductor wire to the aluminum conductor wire, it is necessary to increase the cross-sectional area of the aluminum conductor wire to about 1.5 times the cross-sectional area of the copper conductor wire. Even if an aluminum conductor wire having a large cross-sectional area is used, since the mass of the aluminum conductor wire is about half the mass of the pure copper conductor wire, using the aluminum conductor wire is lightweight. It is advantageous from the viewpoint of conversion. In addition, the above-mentioned "%IACS" represents the electrical conductivity when the resistivity of the international standard annealed copper standard (1.7241×10 ⁻⁸ Ωm) is 100%IACS.

However, pure aluminum wire rods represented by aluminum alloy wire rods for power transmission lines (A1060 and A1070 according to JIS) are generally known to be inferior in tensile strength, impact resistance, bending fatigue characteristics, and the like. For this reason, for example, when using a pure aluminum wire rod in a portion that requires an ultrafine wire with a wire diameter of 0.5 mm or less, a load that is abruptly applied by an operator or industrial equipment at the time of installation work on the vehicle body, or connection between the wire and the terminal It is not possible to withstand pulling at the crimping portion of the portion and bending fatigue applied at a bending portion such as a door portion. Further, if a wire rod alloyed with various additive elements is used, it is possible to enhance tensile strength and bending fatigue characteristics, but the conductivity of the additive element is reduced due to the solid solution phenomenon of the additive element in aluminum. At the same time, there is a problem in that manufacturability is reduced due to the hardened structure, which reduces maneuverability when the wire harness is attached. Therefore, it is necessary to limit or select the additive element within a range that does not lower the conductivity, and to achieve both high tensile strength and maneuverability. Due to such high strength, improvement in impact resistance and bending fatigue characteristics has also been demanded.

As a material capable of obtaining high conductivity and high strength, for example, a 6000-series aluminum alloy wire rod containing Mg and Si is known, and it is possible to obtain high conductivity and Higher strength has been realized. Further, in order to improve the tensile strength and the elongation that contribute to the improvement of impact resistance, the crystal grain size may be reduced. However, when a 6000-series aluminum alloy wire rod is used to increase the strength, the Young's modulus increases, a large force is required for deformation, and the work efficiency of attachment to the vehicle body tends to decrease.

On the other hand, as an example of development of a 6000 series aluminum alloy wire for ultrafine wire use, Patent Document 1 can be cited. Patent Document 1 is a patent application based on the results of research and development by the present inventors, which defines the size of the average crystal grain size at the outer peripheral portion and inside of the wire, and is equivalent to the conventional product. While maintaining the above-mentioned extensibility and electrical conductivity, it is possible to achieve both appropriate yield strength and high flex fatigue resistance.

Japanese Patent No. 5607853 Patent No. 5155464

When the wire harness is attached, the smaller the rigidity (Young's modulus), the smaller the load on the operator and the more efficient the attaching work. Further, a lower Young's modulus is required for the aluminum alloy wire wired in the drive unit system from the same idea. However, in Patent Document 1, each characteristic is balanced on the premise of plastic deformation, and there is no description regarding Young's modulus in particular. Therefore, in order to realize an aluminum alloy wire with a low Young's modulus and high conductivity and tensile strength, it was necessary to reexamine the alloy composition and structure.

The object of the present invention is to achieve high electrical conductivity and high tensile strength while maintaining a low Young's modulus even when used as an ultrafine wire (for example, a wire diameter of 0.5 mm or less). An object is to provide an aluminum alloy wire rod, an aluminum alloy stranded wire, a coated electric wire, and a wire harness.

It is generally known that, in a 6000-series aluminum alloy, as described in Patent Document 2, mechanical properties are adversely affected such as a decrease in tensile strength due to coarsening of the crystal grain size. However, as a result of diligent studies, the present inventors have found that the Young's modulus can be reduced by coarsening the crystal grains, and the reduction in tensile strength can be suppressed by making the crystal grains uniform in size.

That is, the gist configuration of the present invention is as follows.
(1) Mg: 0.1 to 1.0% by mass, Si: 0.1 to 1.2% by mass, Fe: 0.10 to 1.40% by mass, Ti: 0 to 0.100% by mass, B : 0 to 0.030 mass%, Cu: 0 to 1.00 mass%, Ag: 0 to 0.50 mass%, Au: 0 to 0.50 mass%, Mn: 0 to 1.00 mass%, Cr An aluminum alloy wire having a chemical composition consisting of: 0 to 1.00 mass%, Zr: 0 to 0.50 mass%, Ni: 0 to 0.50 mass%, balance: Al and inevitable impurities,
An aluminum alloy wire rod having a maximum area of crystal grains of 2000 μm ² or more and a coefficient of variation of 1.8 or less in a cross section perpendicular to the longitudinal direction of the wire rod.
(2) The aluminum alloy wire according to (1), wherein the area ratio of the crystal grains having an area of 2000 μm ² or more in the cross section is 50% or more.
(3) The aluminum alloy wire according to (2) above, wherein the area ratio of the crystal grains in the cross section that are oriented within a deviation angle of 20° from the {111} crystal orientation is 50% or more.
(4) The aluminum alloy according to the above (2) or (3), wherein the area ratio of the crystal grains in the cross section that are oriented within a deviation angle of 20° from the {111} crystal orientation is 90% or more. wire.
(5) The aluminum alloy wire according to any one of (1) to (4), which has an electrical conductivity of 45% IACS or more, a tensile strength of 150 MPa or more, and a Young's modulus of 70 GPa or less.
(6) The chemical composition contains any one of Ti: 0.001 to 0.100 mass% and B: 0.001 to 0.030 mass%, and the above (1) to ( The aluminum alloy wire rod according to any one of 5).
(7) The chemical composition is Cu: 0.01 to 1.00 mass%, Ag: 0.01 to 0.50 mass%, Au: 0.01 to 0.50 mass%, Mn: 0.01 to. 1.00 mass%, Cr: 0.01 to 1.00 mass%, Zr: 0.01 to 0.50 mass% and Ni: 0.01 to 0.50 mass% contained at least one element The aluminum alloy wire according to any one of (1) to (6) above.
(8) The aluminum alloy wire according to any one of (1) to (7), wherein the chemical composition contains Ni: 0.01 to 0.50 mass %.
(9) Any of (1) to (8) above, wherein the total content of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, and Ni is 0.10 to 2.00 mass %. The aluminum alloy wire according to item 1.
(10) The aluminum alloy wire according to any one of (1) to (9), which is an aluminum alloy wire having a wire diameter of 0.1 to 0.5 mm.
(11) An aluminum alloy twisted wire obtained by twisting a plurality of the aluminum alloy wires according to (10) above.
(12) A coated electric wire having a coating layer on the outer circumference of the aluminum alloy wire according to (10) or the twisted aluminum alloy wire according to (11).
(13) A wire harness comprising the covered electric wire according to (12) above and a terminal attached to an end of the covered electric wire from which the covering layer is removed.
In addition, among the elements whose content ranges are listed in the above chemical composition, any of the elements whose lower limit value of the content range is described as "0 mass%" is a selective addition element that is arbitrarily added as necessary. Means That is, when the predetermined additional element is “0 mass %”, it means that the additional element is not included.

The aluminum alloy wire rod of the present invention achieves high electrical conductivity, high strength and low Young's modulus, so that even a small-diameter wire is less prone to disconnection due to vibration or bending fatigue during wire harness installation, and is flexible and easy to handle. is there. Therefore, it can be installed in a place where different strains are applied, such as a door bending part and an engine part, and it is not necessary to prepare a plurality of wire rods having different characteristics, and one kind of wire rod can combine the above characteristics. It is useful as a battery cable, a harness or a conductor wire for a motor, and a wiring body for an industrial robot.

FIG. 1 is a manufacturing process flowchart showing one embodiment of a preferable manufacturing method when manufacturing the aluminum wire according to the present invention. FIG. 2 is a diagram showing an example of the relationship between the workability and the crystal structure in the final wire drawing. FIG. 3 is a schematic diagram showing a method of cutting out an observation surface of a measurement sample when observing a cross section in an example.

The reasons for limiting the chemical composition and the like of the present invention are shown below.
(1) Chemical composition <Mg: 0.1 to 1.0 mass%>
Mg (magnesium) has a function of strengthening by solid solution in the aluminum base material, and a part thereof precipitates together with Si as a β″ phase (beta double prime phase) or the like to improve tensile strength. When Mg-Si clusters are formed as solute atom clusters, it is an element having an effect of improving tensile strength and elongation.However, when the Mg content is less than 0.1% by mass, the above-mentioned effect is obtained. Is insufficient, and when the Mg content exceeds 1.0 mass %, the possibility of forming a Mg concentrated portion at the crystal grain boundary increases, and the tensile strength and elongation decrease. As the amount of solid solution increases, the 0.2% proof stress increases, the electric wire maneuverability deteriorates, and the electric conductivity also decreases, so the Mg content is 0.1 to 1.0% by mass. The Mg content is preferably 0.5 to 1.0 mass% when high strength is important, and is 0.1 mass% or more and less than 0.5 mass% when conductivity is important. From this viewpoint, it is preferably 0.3 to 0.7% by mass.

<Si: 0.1 to 1.2 mass%>
Si (silicon) has a function of forming a solid solution in the aluminum base material and strengthening it, and part of it has a function of precipitating as a β" phase together with Mg to improve tensile strength and flexural fatigue resistance. Further, Si is an element having an action of improving tensile strength and elongation when forming a Mg—Si cluster or a Si—Si cluster as a solute atom cluster.If the Si content is less than 0.1 mass %. However, the above-mentioned effects are insufficient, and when the Si content exceeds 1.2 mass %, the possibility of forming Si-enriched portions at the grain boundaries increases, and the tensile strength and elongation decrease. Since the solid solution amount of the Si element is increased, the 0.2% proof stress is increased, the electric wire maneuverability is reduced, and the electrical conductivity is also reduced, so that the Si content is 0.1 to 1.2% by mass. The Si content is preferably 0.50 to 1.2% by mass when high strength is important, and 0.1% by mass or more and 0.1% by mass or more when conductivity is important. The content is preferably less than 5% by mass, and from such a viewpoint, it is preferably 0.3 to 0.7% by mass.

<Fe: 0.10 to 1.40 mass%>
Fe (iron) is an element that contributes to the refinement of crystal grains by mainly forming an Al—Fe-based intermetallic compound and improves the tensile strength. Fe can only form a solid solution in Al at 0.05% at 655° C., and is even less at room temperature. Therefore, the remaining Fe that cannot form a solid solution in Al is Al-Fe, Al-Fe-Si, and Al-Fe. Crystallized or precipitated as an intermetallic compound such as -Si-Mg. Intermetallic compounds mainly composed of Fe and Al as described above are referred to as Fe-based compounds in this specification. This intermetallic compound contributes to refinement of crystal grains and improves tensile strength. In addition, Fe also has the effect of improving the tensile strength by the solid solution of Fe in Al. If the Fe content is less than 0.10% by mass, these actions and effects are insufficient, and if the Fe content is more than 1.40% by mass, wire drawing is caused due to coarsening of crystallized substances or precipitates. The workability deteriorates, the 0.2% proof stress increases, the wire handling property decreases, and the elongation decreases. Therefore, the Fe content is 0.10 to 1.40% by mass, preferably 0.15 to 0.70% by mass, and more preferably 0.15 to 0.45% by mass.

As described above, the aluminum alloy wire rod of the present invention contains Mg, Si, and Fe as essential components. However, if necessary, one or both of Ti and B, Cu, Ag, At least one element of Au, Mn, Cr, Zr, and Ni can be contained as a component.

<Ti: 0.001 to 0.100 mass%>
Ti (titanium) is an element having the function of refining the structure of the ingot during melt casting. If the structure of the ingot is coarse, ingot cracks in casting and wire breakage in the wire rod processing step are industrially undesirable. When the Ti content is less than 0.001% by mass, the above-mentioned effects cannot be sufficiently exhibited, and when the Ti content exceeds 0.100% by mass, the conductivity tends to decrease. Is. Therefore, the Ti content is 0.001 to 0.100% by mass, preferably 0.005 to 0.050% by mass, and more preferably 0.005 to 0.030% by mass.

<B: 0.001 to 0.030 mass%>
B (boron) is an element having a function of refining the structure of the ingot at the time of melting and casting, like Ti. If the structure of the ingot is coarse, ingot cracks easily occur in casting and wire breakage easily occurs in the wire rod processing step, which is industrially undesirable. If the B content is less than 0.001% by mass, the above-mentioned effects cannot be sufficiently exhibited, and if the B content exceeds 0.030% by mass, the conductivity tends to decrease. Therefore, the B content is 0.001 to 0.030% by mass, preferably 0.001 to 0.020% by mass, and more preferably 0.001 to 0.010% by mass.

<Cu: 0.01 to 1.00 mass%>, <Ag: 0.01 to 0.50 mass%>, <Au: 0.01 to 0.50 mass%>, <Mn: 0.01 to 1>. 0.00% by mass>, <Cr: 0.01 to 1.00% by mass>, <Zr: 0.01 to 0.50% by mass> and <Ni: 0.01 to 0.50% by mass> Contain at least one element Cu (copper), Ag (silver), Au (gold), Mn (manganese), Cr (chromium), Zr (zirconium), and Ni (nickel) all have fine crystal grains. And Cu, Ag, and Au are elements that also have the effect of increasing the grain boundary strength by precipitating at the grain boundaries. If at least one of the above is contained in an amount of 0.01% by mass or more, the above-described effects can be obtained, and the tensile strength and the elongation can be improved. On the other hand, if any of the contents of Cu, Ag, Au, Mn, Cr, Zr, and Ni exceeds the above upper limits, the compound containing the element becomes coarse and the wire drawability is deteriorated. Therefore, disconnection is likely to occur, and the conductivity tends to decrease. Therefore, the ranges of the contents of Cu, Ag, Au, Mn, Cr, Zr and Ni are set to the ranges defined above. In addition, it is particularly preferable that Ni is contained in these element groups. When Ni is contained, the grain refining effect and the abnormal grain growth suppressing effect become remarkable, the tensile strength and the elongation are improved, and the decrease in conductivity and the disconnection during wire drawing are more easily suppressed. From the viewpoint of satisfying such effects in a well-balanced manner, the Ni content is more preferably 0.05 to 0.30 mass %.

Further, when Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, and Ni are contained in a total amount of more than 2.00 mass%, the conductivity and the elongation decrease. The wire drawing workability tends to deteriorate, and the wire handling property tends to decrease due to an increase in 0.2% proof stress. Therefore, the total content of these elements is preferably 2.00 mass% or less. Since Fe is an essential element in the aluminum alloy wire rod of the present invention, the total content of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, and Ni is 0.10 to 2.00 mass %. Preferably. However, in the case of adding these elements alone, as the content increases, the compound containing the element tends to become coarser, which deteriorates the wire drawing workability and easily causes wire breakage. The content range of the element is defined as above.

In order to reduce the proof stress value appropriately while maintaining high conductivity, the total content of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, and Ni is 0.10 to 0. Particularly preferred is 80% by mass, more preferably 0.15 to 0.60% by mass. On the other hand, in order to further increase the tensile strength and elongation, but also to appropriately reduce the proof stress value with respect to the tensile strength, the total content exceeds 0.80% by mass and 2.00 It is particularly preferable to set the content to be not more than mass%, more preferably to be 1.00 to 2.00 mass%.

<Remainder: Al and unavoidable impurities>
The balance other than the above-mentioned components is Al (aluminum) and inevitable impurities. The unavoidable impurities referred to here mean impurities at a content level that can be unavoidably included in the manufacturing process. Since the unavoidable impurities may be a factor that decreases the conductivity depending on the content, it is preferable to suppress the content of the unavoidable impurities to some extent in consideration of the decrease in the conductivity. Examples of the components that can be cited as the inevitable impurities include Ga (gallium), Zn (zinc), Bi (bismuth), and Pb (lead).

Such an aluminum alloy wire rod can be realized by controlling the alloy composition and the manufacturing process in combination. Hereinafter, a suitable method for manufacturing the aluminum alloy wire according to the present invention will be described.

(2) Method for producing aluminum alloy wire according to one embodiment of the present invention The aluminum alloy wire according to the present invention is characterized by having coarse crystal grains and a uniform structure.
Since crystal grains usually grow during annealing, it is common to adjust the annealing conditions in order to obtain a coarse grain structure (structure with large crystal grains). However, the present inventors have found that a grain coarse and uniform structure (structure with large and uniform crystal grains) can be realized by examining the processing rate in the wire drawing step, and have completed the present invention. Furthermore, as a result of further studying the wire drawing, intermediate annealing and solution treatment steps, the present inventors have adjusted the crystal orientation by adjusting these steps to maintain a low Young's modulus. Have found that higher strength can be achieved.

Such an aluminum alloy wire rod according to one embodiment of the present invention includes [1] melting, [2] casting, [3] hot working (groove roll working, etc.), [4] wire drawing, and [5] final intermediate. It can be manufactured by a manufacturing method including sequentially performing each step of heat treatment, [6] final wire drawing, [7] solution heat treatment, and [8] aging heat treatment. For the purpose of determining the wire drawing ratio before and after the final intermediate heat treatment, an intermediate heat treatment may be added in [4] wire drawing. Further, before and after the solution heat treatment, or after the aging heat treatment, a step of forming a twisted wire (twisted wire processing) or a step of coating the electric wire with a resin may be provided. The steps [1] to [8] will be described below.

First, FIG. 1 shows an example of a manufacturing process flowchart of an aluminum alloy wire. The process shown by a broken line in FIG. 1 is an arbitrary process and is not limited to the description of FIG. 1, and necessity, order, number of times, etc. can be appropriately changed within a range not hindering the effect of the invention.

[1] Melting In the melting step, a material in which the amount of each component is adjusted so as to have the above-described aluminum alloy composition is prepared and then melted.

[2] Casting and [3] Hot working (groove roll processing, etc.)
Next, in the casting step, the cooling rate is increased to moderately reduce the crystallization of the Fe-based compound and make it finer. Preferably, the average cooling rate from the molten metal temperature to 400° C. at the time of casting is 20 to 50° C./s, and if a Propelti type continuous casting and rolling machine combining a casting wheel and a belt is used, for example, a bar material having a diameter of 5 to 15 mm Can be obtained. Moreover, if the underwater spinning method is used, a bar material having a diameter of 1 to 13 mm can be obtained at an average cooling rate of 30° C./s or more. The casting and hot working (rolling) may be performed by billet casting, extrusion method or the like. Further, re-heat treatment at 400° C. or higher may be performed after the above casting or after hot working.

[4] Wire Drawing Next, the surface is peeled off to obtain a bar material having an appropriate thickness, for example, a diameter of 5 to 12.5 mmφ, and this is cold drawn. Peeling of the surface cleans the surface by performing the peeling, but it may not be performed. In the wire drawing, an intermediate heat treatment may be added if necessary for the purpose of determining the wire drawing work ratio before and after the final intermediate heat treatment. The wire drawing process may be performed once or may be repeated multiple times until the desired wire diameter is obtained. In the wire drawing work up to the final intermediate heat treatment, the working rate is preferably 40 to 99.99%, and more preferably 95 to 99.99%. Here, the "working ratio" is {(a cross-sectional area perpendicular to the longitudinal direction of the wire material before wire drawing)-(after wire drawing (if there is a plurality of wire drawing operations, after the last wire drawing)) Of the wire rod perpendicular to the longitudinal direction)}×100/(Cross sectional area perpendicular to the longitudinal direction of the wire rod before wire drawing). By setting the working rate in the wire drawing process up to the final intermediate heat treatment to 40% or more, the deviation angle from the {111} crystal orientation occupying in the cross section perpendicular to the longitudinal direction of the obtained wire is oriented within 20°. The area ratio of the crystal grains to be formed can be 50% or more, and the processing rate in the wire drawing process up to the final intermediate heat treatment is 95% or more, thereby occupying the {111} crystal orientation in the cross section. The area ratio of the crystal grains oriented within an angle of deviation of 20° or less can be 90% or more.

[5] Final Intermediate Heat Treatment Next, a final intermediate heat treatment is applied to the work drawn by cold drawing by wire drawing. The final intermediate heat treatment of the present embodiment is performed not only to regain the flexibility of the material to be processed and to improve the wire drawing workability, but also to compounds such as Fe, Mn, and Ni that have the role of pinning the grain boundaries during solution treatment. Has a role to generate. The final intermediate heat treatment is preferably performed at a heat treatment temperature of 250 to 450° C. and a holding time of 2 to 5 hours. Examples of the method of performing the final intermediate heat treatment include batch annealing. In addition, when the intermediate heat treatment is added in [4] wire drawing for the purpose of determining the wire drawing ratio before and after the final intermediate heat treatment, the intermediate heat treatment is performed at a heat treatment temperature of 250 to 450° C. It is preferable to adjust the total heat treatment time to 2 to 5 hours.

[6] Final Wire Drawing After the final intermediate heat treatment, cold drawing is performed. In the final wire drawing, the working rate is preferably 3 to 60%, more preferably 3 to 30%. By setting the working ratio in the final wire drawing process to 60% or less, the maximum value of the area of the crystal grains can be set to 2000 μm ² or more in the cross section perpendicular to the longitudinal direction of the obtained wire rod. By setting the processing rate in processing to 30% or less, the area ratio occupied by crystal grains having an area of 2000 μm ² or more in the cross section can be 50% or more.

FIG. 2 is a diagram showing an example of the relationship between the workability and the crystal structure in the final wire drawing. In FIG. 2, the EBSD image is an image photographed by performing a tissue analysis on a cross section perpendicular to the longitudinal direction of the wire corresponding to each processing rate by the EBSD method described later. In addition, in FIG. 2, the crystal grain distribution diagram is a graph obtained by measuring the area of the crystal grain based on the photographed image and graphing it, and the maximum value of the area of the crystal grain and the coefficient of variation are shown in the above analysis. The value calculated by
As can be seen from the relationship shown in FIG. 2, in the final wire drawing, by setting the processing rate to 60% or less, the maximum value of the area of the crystal grains is 2000 μm ² or more in the cross section perpendicular to the longitudinal direction of the wire. A wire rod having a coefficient of variation of 1.8 or less can be efficiently manufactured.
The difference in the color of the crystal grains in the EBSD image shown in FIG. 2 represents the difference in the oriented crystal orientation. That is, in the EBSD image, the more grains having the same color shade, the more grains having the same crystal orientation.

[7] Solution heat treatment Further, the solution heat treatment is applied to the cold drawn wire to be worked by the final wire drawing. The solution heat treatment of the present embodiment is a heat treatment performed to dissolve the randomly contained compound of Mg and Si in the aluminum matrix. Specifically, the solution heat treatment is performed by heating at a predetermined temperature within a range of 500 to 580° C., holding for a predetermined time, and then cooling at an average cooling rate of 10° C./s or more up to a temperature of at least 150° C. Heat treatment. If the predetermined temperature during the heat treatment in the solution heat treatment is higher than 580° C., the crystal grains become coarse and abnormally grown grains are generated, and if the predetermined temperature is lower than 500° C., Mg ₂ Si is sufficiently solid-dissolved. I can't. Therefore, the predetermined temperature at the time of heating in the solution heat treatment is set in the range of 500 to 580°C and is preferably set to 500 to 540°C, more preferably 500 to 520°C, though it varies depending on the contents of Mg and Si. .. Further, the time of holding at the above-mentioned predetermined temperature in the solution heat treatment is preferably 10 seconds or more and 30 minutes or less, and more preferably 10 to 30 minutes.

As a method of performing solution heat treatment, for example, batch annealing, salt bath (salt bath), continuous heat treatment such as high-frequency heating, electric heating (current annealing), or running heating (running annealing) may be used.

If one or both of the wire temperature and the heat treatment time are smaller than the conditions specified above, solution treatment will be incomplete and solute atom clusters, β” phase, and Mg ₂ Si precipitates that will be generated during the subsequent aging heat treatment. When the wire rod temperature and/or heat treatment time are higher than the conditions specified above, the crystal will be reduced. Along with the coarsening of the grains, the compound phase in the aluminum alloy wire rod is partially melted (eutectic melting), the tensile strength and the elongation are lowered, and the wire breakage easily occurs when the conductor is handled.

[8] Aging heat treatment Next, an aging heat treatment is performed to generate Mg, Si compounds or solute atom clusters. The aging heat treatment is heating at a predetermined temperature within the range of 20 to 250°C. If the predetermined temperature in the aging heat treatment is less than 20° C., the solute atom clusters are slowly formed, and it takes time to obtain the required tensile strength and elongation, which is disadvantageous in mass production. When the predetermined temperature is higher than 250° C., coarse Mg ₂ Si precipitates are formed in addition to the Mg ₂ Si acicular precipitates (β″ phase) that most contribute to the strength, and the strength decreases. Therefore, the above-mentioned predetermined temperature is preferably 20 to 70° C. when solute atom clusters that are more effective in improving elongation are formed, and the β″ phase is also precipitated at the same time, so that tensile strength and elongation When balancing, it is preferably 100 to 150°C.

Further, the heating/holding time in the aging heat treatment varies depending on the temperature. Heating at a low temperature for a long time and at a high temperature for a short time is preferable in order to improve tensile strength and elongation. The heating for a long time is, for example, 10 days or less, and the heating for a short time is preferably 15 hours or less, more preferably 8 hours or less. The cooling in the aging heat treatment is preferably as fast as possible in order to prevent variations in characteristics. Of course, even in the case where cooling cannot be performed quickly in the manufacturing process, the aging condition can be appropriately set as long as the aging condition is sufficient to generate solute atom clusters.

In the aluminum alloy wire rod of the present embodiment, the wire diameter is not particularly limited and can be appropriately determined according to the application. In the case of a fine wire, it is 0.1 to 0.5 mmφ, and in the case of a medium fine wire, It is preferably 0.8 to 1.5 mmφ. Aluminum alloy wire rod of the present embodiment, as an aluminum alloy wire, one of the advantages that can be used in a thin single wire, it can also be used as an aluminum alloy stranded wire obtained by bundling a plurality of, Among the steps [1] to [8] constituting the manufacturing method of the present invention, the aluminum alloy wire rods obtained by sequentially performing the steps [1] to [6] are bundled into a plurality of wires and twisted, The steps of 7] solution heat treatment and [8] aging heat treatment may be performed.

Further, in the present embodiment, as an additional step, a homogenizing heat treatment, which is performed by a conventional method, can be performed after the casting step or after the hot working. In the homogenization heat treatment, the additive elements can be uniformly dispersed, so that solute atom clusters and β” precipitation phases can be easily generated uniformly in the subsequent solution heat treatment, improving tensile strength and elongation, and increasing tensile strength. It is possible to more stably obtain a moderately low yield strength for the homogenizing heat treatment, and it is preferable to carry out the homogenizing heat treatment at a heating temperature of 450° C. to 600° C., and more preferably 500 to 600° C. For the cooling in (1), it is preferable to gradually cool at an average cooling rate of 0.1 to 10° C./minute in order to easily obtain a uniform compound.

(3) Systematic features of the aluminum alloy wire rod of the present invention The aluminum alloy wire rod of the present embodiment manufactured by the above-described manufacturing method has the maximum value of the area of crystal grains in a cross section perpendicular to the longitudinal direction of the wire rod. Is 2000 μm ² or more and the coefficient of variation is 1.8 or less. In this specification, when the angle difference between two aligned crystal grains is 15° or more, the crystal interface is defined as a grain boundary, and the portion surrounded by the grain boundaries is defined as a “crystal grain”. The longitudinal direction of the wire rod is the axial direction perpendicular to the wire diameter and corresponds to the wire drawing direction when manufacturing the wire rod.

In the cross section, the Young's modulus can be kept low by setting the maximum value of the crystal grain area to 2000 μm ² or more. The maximum value of the area of the crystal grains is preferably 2000 to 30000 μm ² , and more preferably 2000 to 8000 μm ² .

Further, the coefficient of variation is an index by which the uniformity of crystal grains can be compared while the dependence of the crystal grain size is small. Therefore, by setting the coefficient of variation to be 1.8 or less, it is possible to achieve a low Young's modulus while making the particle diameters uniform, thereby suppressing a decrease in elongation and a decrease in tensile strength. The coefficient of variation is preferably 1.3 or less, more preferably 1.0 or less. The coefficient of variation can be calculated (a/b) by dividing the standard deviation (a) obtained from the crystal grain distribution of the wire by the average crystal grain size (b).

Further, the area ratio of the crystal grains having an area of 2000 μm ² or more in the cross section is preferably 50% or more, and more preferably 80% or more. By setting it in the above range, the Young's modulus can be kept low.

In addition, the area ratio of the crystal grains in the above-mentioned cross section, which are oriented within 20° from the {111} crystal orientation, is preferably 50% or more, more preferably 90% or more. Here, the area ratio represents the degree of accumulation of crystal grains oriented within a deviation angle of 20° from the {111} crystal orientation. By setting it as the said range, high tensile strength can be maintained.

In the present invention, the measurement of the area, grain size, and crystal orientation of crystal grains as described above is performed by image analysis using the EBSD method. EBSD is an abbreviation for Electron BackScatter Diffraction (electron backscattering diffraction), and is a reflection electron Kikuchi diffraction (Kikuchi pattern) generated when a sample is irradiated with an electron beam in a scanning electron microscope (SEM: Scanning Electron Microscope). This is the crystal orientation analysis technology used. In the present invention, the surface of the sample which is perpendicular to the longitudinal direction (the surface parallel to the wire diameter) is scanned in steps of 2 μm, and the analysis software (manufactured by EDAX/TSL (current AMETEK), trade name "Orientation Imaging Microscopy v5") is used to analyze the area and crystal orientation of crystal grains in a cross section perpendicular to the longitudinal direction of the wire. In the EBSD measurement, in order to obtain a clear Kikuchi line diffraction image, it is necessary to remove foreign matter adhering to the measurement surface and at the same time perform mirror finishing. As a mirror finishing method, for example, a method of polishing the cross section by CP (cross section polisher) processing can be mentioned.

(4) Characteristics of Aluminum Alloy Wire of the Present Invention The electrical conductivity is preferably 45% IACS or more, and more preferably 50% IACS or more, in order to prevent heat generation due to Joule heat. The higher the conductivity, the more suitable it is for the diameter reduction.

The Young's modulus is preferably 70 GPa or less, and more preferably 68 Pa or less. The lower the Young's modulus is, the higher the flexibility is and the better the maneuverability is. Therefore, the load on the operator is reduced, and the mounting work becomes efficient.

Further, as in the conventional case, even if it is applied to a thin wire having a small cross-sectional area, high tensile strength is required so that it can be used without breaking, so that the tensile strength is preferably 150 MPa or more. , 200 MPa or more is more preferable.

The measuring method of each of the above characteristics will be described in Examples described later.

The aluminum alloy wire rod of the present invention can be used as an aluminum alloy wire or as an aluminum alloy stranded wire formed by twisting a plurality of aluminum alloy wires, and further, on the outer periphery of the aluminum alloy wire or the aluminum alloy stranded wire. It can be used as a covered electric wire having a covering layer, and in addition, it is used as a wire harness (assembled electric wire) including a covered electric wire and a terminal attached to an end of the covered electric wire from which the covering layer is removed. It is also possible.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and includes various aspects included in the concept of the present invention and the scope of the claims, and various modifications within the scope of the present invention. Can be modified to

Next, in order to further clarify the effect of the present invention, examples and comparative examples will be described, but the present invention is not limited to these examples.

(Examples 1 to 7 and Comparative Examples 1 to 5)
A table showing Mg, Si, Fe and Al which are essential components and at least one component of Ti, B, Cu, Ag, Au, Mn, Cr, Zr and Ni which are components that are selectively added. An alloy material having the chemical composition (mass %) shown in 1 was prepared.

This alloy material was rolled using a Propelti type continuous casting and rolling machine while continuously casting the molten metal in a water-cooled mold under the conditions shown in Table 2 to obtain a φ9.5 mm bar. Next, this was wire-drawn so that the processing rates shown in Table 2 could be obtained.
Next, the drawn material is subjected to final intermediate heat treatment under the conditions shown in Table 2, and finally drawn so that the processing rate shown in Table 2 can be obtained up to a wire diameter of φ0.3 mm. went.
Next, the processed material subjected to the final wire drawing was subjected to solution heat treatment under the conditions shown in Table 2.
In the batch type heat treatment in the final intermediate heat treatment and solution heat treatment, the wire temperature was measured by winding a thermocouple around the wire. In continuous energization heat treatment, it is difficult to measure at the part where the temperature of the wire is the highest, so the fiber type radiation thermometer (made by Japan Sensor Co., Ltd.) should be placed at a position before the part where the temperature of the wire is highest. The temperature was measured by using the above method, and the maximum temperature was calculated in consideration of Joule heat and heat dissipation. In the high frequency heating and the heat treatment during continuous running, the wire temperature near the exit of the heat treatment section was measured.
Further, the processed material subjected to the solution heat treatment was subjected to an aging heat treatment under the conditions shown in Table 2 to manufacture an aluminum alloy wire (wire diameter 300 μm).

(Evaluation)
The aluminum alloy wires according to the above Examples and Comparative Examples were subjected to the following measurements and evaluations. The evaluation conditions are as follows. The results are shown in Table 3.

[Observation of crystal grains and analysis of crystal orientation]
Observation of crystal grains and analysis of crystal orientation were performed by electron beam backscattering diffraction (EBSD) using a Schottky field emission scanning electron microscope (JSM-7001F, manufactured by JEOL Ltd.). As a measurement sample, a wire rod having a diameter of 300 μm was prepared, and after being embedded with resin, CP (cross section polisher) processing was performed to cut out a cross section perpendicular to the longitudinal direction of the wire rod to obtain an observation surface. The scan step during measurement was 2 μm. In addition, this measurement was performed on 10 observation surfaces for each alloy wire. As shown in FIG. 3, the method of cutting out the observation surface of 10 is to cut out a cross section of an arbitrary portion N1, first cut out a cross section of a portion N2 500 mm apart, and then see N1 from the cross section of N2. A cross section of a portion N3 separated by 500 mm in the direction opposite to the cross section of is cut out. A cross section was cut to N10 by the same method, 10 measurement samples were prepared, and CP processing was performed after resin embedding as described above to obtain 10 observation surfaces.
For analysis of the obtained data, analysis software (trade name "Orientation Imaging Microscopy v5" manufactured by EDAX/TSL (currently AMETEK)) was used. The grain boundary definition is defined as the interface between crystals having an angle difference of 15° or more, and after calculating all the crystal grain areas, the area of crystal grains having an area of 2000 μm ² or more occupying the cross section perpendicular to the longitudinal direction of the wire. The ratio, the standard deviation (a), the average crystal grain size (b), and the coefficient of variation (a/b) were obtained, and the average value (N=10) was calculated.
In addition, according to the above image analysis, the area ratio of the crystal grains in the cross section perpendicular to the longitudinal direction of the wire rod, the deviation angle from the {111} crystal orientation being within 20° [(deviation from the {111} crystal orientation] The average value (N=10) was calculated by calculating the area of the crystal grains oriented within an angle of 20°×100/(area of the cross section perpendicular to the longitudinal direction of the wire)]. Also, regarding the area ratio of the crystal grains oriented within 20° from the {100} crystal orientation and the area ratio of the crystal grains oriented within 20° from the {101} crystal orientation, {111 } An average value (each N=10) was calculated by the same method as in the case of crystal orientation.

[Electrical conductivity (EC)]
The resistivity was measured by the four-terminal method in a constant temperature bath in which 300 mm long test pieces (three for each wire) were kept at 20° C. (±0.5° C.), and the average conductivity (N=3) was measured. ) Was calculated. The distance between the terminals was 200 mm. In this example, the conductivity was 45% IACS or higher as the pass level.

[Tensile strength]
According to JIS Z 2241:2011, a tensile test was performed on test pieces (three for each wire), the tensile strength was calculated (MPa), and the average value (N=3) was calculated. In this example, 150 MPa or more was set as the pass level.

[Young's modulus]
Using a device similar to the above tensile strength measurement, a tensile test was conducted on test pieces (three for each wire), and the tangent line of the SS curve in the elastic deformation region was calculated as Young's modulus (GPa), The average value (N=3) was calculated. In the present example, the Young's modulus was 70 GPa or less as a pass level.

[Stretch]
According to JIS Z2241:2011, tensile tests were performed on test pieces (three for each wire), elongations were calculated (%), and their average value (N=3) was determined. The larger the elongation, the more preferable and the more preferable is 5% or more.

From the results of Table 3, in each aluminum alloy wire rod, various conditions relating to the maximum value of the area of the crystal grains, the coefficient of variation, and the like, and the correlation between the evaluated characteristics can be read. The following is clear. That is, the aluminum alloy wire rods of Examples 1 to 7 have a predetermined alloy composition, and in the cross section perpendicular to the longitudinal direction of the wire rod, the maximum value of the area of crystal grains is 2000 μm ² or more and the coefficient of variation is 1.8. It was confirmed that all of them have high conductivity, high strength and low Young's modulus because they are controlled to be as follows.

On the other hand, the aluminum alloy wire rod of Comparative Example 1 does not particularly contain Mg and Si which are essential components, and the alloy composition is outside the proper range of the present invention. It was confirmed that the tensile strength was significantly inferior to that of the aluminum alloy wire rod.
Further, in the aluminum alloy wire rods of Comparative Examples 2 and 3, the maximum value of the area of the crystal grains is less than 2000 μm ² in the cross section perpendicular to the longitudinal direction of the wire rod, which is outside the proper range of the present invention, so It was confirmed that the Young's modulus was higher than those of the aluminum alloy wire rods of Examples 1 to 7. Furthermore, it was confirmed that the aluminum alloy wire rod of Comparative Example 2 was inferior in electrical conductivity to the aluminum alloy wire rods of Examples 1 to 7 according to the present invention.
Further, in the aluminum alloy wire rods of Comparative Examples 4 and 5, the coefficient of variation exceeds 1.8 in the cross section perpendicular to the longitudinal direction of the wire rod, which is outside the proper range of the present invention. It was confirmed that the tensile strength was inferior to the aluminum alloy wire rods of 1 to 7.

Claims (12)

Mg: 0.1 to 1.0 mass%, Si: 0.1 to 1.2 mass%, Fe: 0.10 to 1.40 mass%, Ti: 0 to 0.100 mass%, B: 0 0.030 mass%, Cu:0-1.00 mass%, Ag:0-0.50 mass%, Au:0-0.50 mass%, Mn:0-1.00 mass%, Cr:0- An aluminum alloy wire rod having a chemical composition of 1.00% by mass, Zr:0 to 0.50% by mass, Ni:0 to 0.50% by mass, and the balance: Al and inevitable impurities.
The total content of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, and Ni is 0.10 to 2.00 mass %,
An aluminum alloy wire rod having a maximum area of crystal grains of 2000 μm ² or more and a coefficient of variation of 1.8 or less in a cross section perpendicular to the longitudinal direction of the wire rod. The aluminum alloy wire rod according to claim 1, wherein an area ratio of crystal grains having an area of 2000 μm ² or more in the cross section is 50% or more. The aluminum alloy wire rod according to claim 2, wherein an area ratio of crystal grains oriented within a deviation angle from a {111} crystal orientation within 20° in the cross section is 50% or more. The aluminum alloy wire rod according to claim 3 , wherein an area ratio of crystal grains oriented within a deviation angle from the {111} crystal orientation within 20° in the cross section is 90% or more. The aluminum alloy wire rod according to any one of claims 1 to 4, which has an electric conductivity of 45% IACS or more, a tensile strength of 150 MPa or more, and a Young's modulus of 70 GPa or less. 6. The chemical composition according to claim 1, wherein the chemical composition contains at least one of Ti: 0.001 to 0.100 mass% and B: 0.001 to 0.030 mass %. The aluminum alloy wire according to item. The chemical composition is Cu: 0.01 to 1.00 mass%, Ag: 0.01 to 0.50 mass%, Au: 0.01 to 0.50 mass%, Mn: 0.01 to 1.00. %, Cr: 0.01 to 1.00% by mass, Zr: 0.01 to 0.50% by mass, and Ni: 0.01 to 0.50% by mass, at least one element is contained. Item 7. The aluminum alloy wire rod according to any one of Items 1 to 6. The aluminum alloy wire rod according to claim 1, wherein the chemical composition contains Ni: 0.01 to 0.50 mass %. Wire diameter is aluminum alloy wire is 0.1 to 0.5 mm, the aluminum alloy wire according to any one of claims 1-8. An aluminum alloy stranded wire formed by twisting a plurality of the aluminum alloy wires according to claim 9 . A coated electric wire having a coating layer on the outer periphery of the aluminum alloy wire according to claim 9 or the stranded aluminum alloy wire according to claim 10 . A wire harness comprising the covered electric wire according to claim 11 and a terminal attached to an end of the covered electric wire from which the covering layer is removed.

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