JP2017179545A - Aluminum alloy wire material, aluminum alloy twisted wire, coated wire and wire harness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy wire material capable of achieving high conductivity and high tensile strength while maintaining low Young modulus even when used as an ultrafine wire (for example with wire diameter of 0.5 mm or less.SOLUTION: There is provided an aluminum alloy wire material having a chemical composition containing 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 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:0 to 1.00 mass%, Zr:0 to 0.50 mass%, Ni:0 to 0.50 mass% and the balance:Al with inevitable impurities, maximum value of area of crystal particles in a cross section vertical to a longer direction of the wire material of 2000 μmor more and variation coefficient of 1.8 or less.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, as an electric wiring body of a moving body such as an automobile, a train, an aircraft, or an electric wiring body of an industrial robot, a terminal made of copper or a copper alloy (for example, brass) is used for an electric wire including a copper or copper alloy conductor ( A so-called wire harness member equipped with a connector has been used. In recent years, the performance and functionality of automobiles have been rapidly advanced, and as a result, the number of various electric devices and control devices mounted on the vehicle has increased, and these devices are used in these devices. There is also a tendency for the number of electric wiring bodies to increase. On the other hand, in order to improve the fuel efficiency of a moving body such as an automobile for environmental reasons, it is strongly desired to reduce the weight of the moving body.

As one of the means for achieving such weight reduction of the moving body, for example, it is considered to replace the conductor of the electric wiring body with a lighter aluminum or aluminum alloy instead of the conventionally used copper or copper alloy. It is being advanced. The specific gravity of aluminum is about 1/3 of the specific gravity of copper, and the electrical conductivity of aluminum is about 2/3 of the electrical conductivity of copper (pure aluminum is about 66% IACS when pure copper is used as a standard of 100% IACS). In order to pass the same current as the copper conductor wire through the aluminum conductor wire, the cross-sectional area of the aluminum conductor wire needs to be about 1.5 times the cross-sectional area of the copper conductor wire. Even if the aluminum conductor wire having a large cross-sectional area is used, the weight of the aluminum conductor wire is about half that of the pure copper conductor wire. This is advantageous from the standpoint of conversion. In addition, said "% IACS" represents the electrical conductivity when the resistivity 1.7241 * 10 < ^-8 > (ohm) m of universal standard annealed copper (International Annealed Copper Standard) is set to 100% IACS.

  However, pure aluminum wires represented by aluminum alloy wires for power transmission lines (A1060 and A1070 according to JIS standards) are generally known to have inferior tensile strength, impact resistance, bending fatigue characteristics, and the like. Therefore, for example, when using a pure aluminum wire in a part that requires an extra fine wire with a wire diameter of 0.5 mm or less, the load that is unexpectedly applied by an operator or industrial equipment during the installation work to the vehicle body, or the connection between the electric wire and the terminal It cannot withstand pulling at the crimping part or bending fatigue loaded at a bending part such as a door part. In addition, using wire alloyed with various additive elements can improve tensile strength and flexural fatigue properties, but it causes a decrease in conductivity due to the solid solution phenomenon of the additive elements in aluminum. At the same time, due to the hardening, there is a problem that the maneuverability is lowered and the productivity is lowered 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 handling property. Improvement in impact resistance and flexural fatigue characteristics has also been demanded by such an increase in strength.

  As a material that can obtain high conductivity and high strength, for example, a 6000 series aluminum alloy wire containing Mg and Si is known. By adjusting additive elements and performing aging treatment after solution treatment, high conductivity and High strength has been realized. Furthermore, in order to improve the tensile strength and elongation that contribute to the improvement of impact resistance, the crystal grain size may be refined. However, when the strength is increased by using a 6000 series aluminum alloy wire, the Young's modulus increases, a large force is required for deformation, and the mounting work efficiency to the vehicle body tends to decrease.

  On the other hand, Patent Document 1 can be cited as an example of developing a 6000 series aluminum alloy wire for ultrafine wire. Patent Document 1 is a patent application based on the results of research and development by the present inventors, which defines the average crystal grain size at the outer periphery and inside of the wire, and is equivalent to the conventional product. While maintaining the above-described extensibility and electrical conductivity, both appropriate proof stress and high bending fatigue resistance are achieved.

Japanese Patent No. 5607533 Japanese Patent No. 5155464

  When attaching a wire harness, the smaller the rigidity (Young's modulus), the smaller the load on the operator, and the more efficient the installation work. In addition, a low Young's modulus is also required for aluminum alloy wires wired to the drive unit system from the same concept. However, Patent Document 1 balances each characteristic on the premise of plastic deformation, and does not describe particularly a study on Young's modulus. Therefore, in order to realize an aluminum alloy wire having a low Young's modulus and high electrical conductivity and tensile strength, it is necessary to review the alloy composition and the structure.

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

  In general, in 6000 series aluminum alloys, as described in Patent Document 2, it is known that the mechanical properties are adversely affected, for example, the tensile strength is lowered due to the coarsening of the crystal grain size. However, as a result of intensive studies, the present inventors have found that the Young's modulus can be reduced by coarsening the crystal grains, and further, the reduction in tensile strength can be suppressed by making the size of the crystal grains uniform.

That is, the gist configuration of the present invention is as follows.
(1) 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 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 : 0 to 1.00% by mass, Zr: 0 to 0.50% by mass, Ni: 0 to 0.50% by mass, balance: aluminum alloy wire having a chemical composition consisting of Al and inevitable impurities,
An aluminum alloy wire characterized by 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.
(2) The aluminum alloy wire according to (1) above, wherein an area ratio of 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 an area ratio of crystal grains in which the deviation angle from the {111} crystal orientation in the cross section is within 20 ° is 50% or more.
(4) The aluminum alloy according to (2) or (3), wherein an area ratio of crystal grains in which the deviation angle from the {111} crystal orientation is within 20 ° in the cross section is 90% or more wire.
(5) The aluminum alloy wire according to any one of (1) to (4), wherein the electrical conductivity is 45% IACS or more, the tensile strength is 150 MPa or more, and the Young's modulus is 70 GPa or less.
(6) Said chemical composition contains any one element among Ti: 0.001-0.100 mass% and B: 0.001-0.030 mass%, said (1)-( The aluminum alloy wire 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 Contains at least one element of 1.00% 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 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% by mass The aluminum alloy wire according to claim 1.
(10) The aluminum alloy wire according to any one of (1) to (9), which is an aluminum alloy wire having a strand 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).
(12) A covered electric wire having a coating layer on the outer periphery of the aluminum alloy wire according to (10) or the aluminum alloy twisted wire according to (11).
(13) A wire harness comprising the covered electric wire according to (12) 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 chemical composition, any of the elements whose lower limit value of the content range is described as “0% by mass” are optionally added as necessary. Means. That is, when the predetermined additive element is “0 mass%”, it means that the additive element is not included.

  The aluminum alloy wire of the present invention realizes high electrical conductivity, high strength, and low Young's modulus, so that even with a thin wire, wire breakage due to vibration and bending fatigue is not likely to occur, and it is flexible and easy to handle. is there. Therefore, it can be installed in places where different distortions are applied, such as the door bending part and the engine part, and it is not necessary to prepare multiple wires with different characteristics, and one type of wire can have the above characteristics. It is useful as a battery cable, a harness or a conductor for a motor, and a wiring body for an industrial robot.

FIG. 1 is a manufacturing process flowchart showing an embodiment of a preferable manufacturing method when the aluminum wire of the present invention is manufactured. FIG. 2 is a diagram showing an example of the relationship between the processing rate and the crystal structure in the final wire drawing. FIG. 3 is a schematic diagram showing a method for cutting out the observation surface of the measurement sample when performing cross-sectional observation in the 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% by mass>
Mg (magnesium) has an effect of strengthening by dissolving in an aluminum base material, and a part of it precipitates together with Si as a β ″ phase (beta double prime phase) to improve tensile strength. In addition, when an Mg-Si cluster is formed as a solute atom cluster, it is an element having an effect of improving the tensile strength and elongation, however, when the Mg content is less than 0.1% by mass, If the Mg content exceeds 1.0% by mass, the possibility of forming a Mg-concentrated portion at the grain boundary increases, and the tensile strength and elongation decrease. As the amount of solid solution increases, the 0.2% proof stress increases, the wire handling performance decreases, and the electrical conductivity decreases, so the Mg content should be 0.1 to 1.0% by mass. The Mg content is preferably 0.5 to 1.0% by mass when importance is placed on high strength, and 0.1% by mass or more and 0.5% when importance is placed on conductivity. It is preferable to set it as less than mass%, and it is preferable to set it as 0.3-0.7 mass% generally from such a viewpoint.

<Si: 0.1-1.2% by mass>
Si (silicon) has a function of strengthening by dissolving in an aluminum base material, and a part thereof precipitates together with Mg as a β ″ phase and the like, and has an action of improving tensile strength and bending fatigue resistance. Si is an element that has the effect of improving tensile strength and elongation when Mg-Si clusters or Si-Si clusters are formed as solute atomic clusters.If the Si content is less than 0.1% by mass, When the above-described effects are insufficient, and the Si content exceeds 1.2% by mass, the possibility of forming Si-concentrated portions at the crystal grain boundaries increases, and the tensile strength and elongation decrease. As the solid solution amount of Si element increases, the 0.2% proof stress increases, the wire handling performance decreases and the electrical conductivity decreases, so the Si content is 0.1 to 1.2% by mass. Do The Si content is preferably 0.50 to 1.2% by mass when importance is placed on high strength, and 0.1% to 0.5% by mass when conductivity is important. It is preferable to set it as less than%, and it is preferable to set it as 0.3-0.7 mass% comprehensively from such a viewpoint.

<Fe: 0.10 to 1.40 mass%>
Fe (iron) is an element that contributes to refinement of crystal grains and mainly improves tensile strength by forming an Al—Fe-based intermetallic compound. Fe can only be dissolved at 0.05% by mass at 655 ° C. in Al and is still less at room temperature. Therefore, the remaining Fe that cannot be dissolved in Al is Al—Fe, Al—Fe—Si, Al—Fe. -Crystallizes or precipitates as an intermetallic compound such as Si-Mg. Such an intermetallic compound mainly composed of Fe and Al is referred to as an Fe-based compound in this specification. This intermetallic compound contributes to the refinement of crystal grains and improves the tensile strength. Moreover, Fe has the effect | action which improves a tensile strength also by Fe dissolved in Al. If the Fe content is less than 0.10% by mass, these effects are insufficient, and if the Fe content exceeds 1.40% by mass, the wire is drawn due to coarsening of the crystallized product or precipitate. As the workability decreases, the 0.2% proof stress increases, the wire handling performance decreases, and the elongation decreases. Therefore, the Fe content is set to 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 of the present invention contains Mg, Si, and Fe as essential components, but if necessary, any one of Ti and B, Cu, Ag, Among Au, Mn, Cr, Zr and Ni, at least one element can be included.

<Ti: 0.001 to 0.100 mass%>
Ti (titanium) is an element having an effect of refining the structure of the ingot at the time of melt casting. If the structure of the ingot is coarse, the ingot cracking in the casting or disconnection occurs in the wire processing step, which is not industrially desirable. If the Ti content is less than 0.001% by mass, the above-mentioned effects cannot be fully exhibited, and if the Ti content exceeds 0.100% by mass, the conductivity tends to decrease. It is. Therefore, the Ti content is 0.001 to 0.100 mass%, preferably 0.005 to 0.050 mass%, more preferably 0.005 to 0.030 mass%.

<B: 0.001 to 0.030 mass%>
B (boron) is an element having an effect of refining the structure of the ingot at the time of melt casting, like Ti. A coarse ingot structure is not industrially desirable because it tends to cause ingot cracking and disconnection in the wire processing step during casting. When the B content is less than 0.001% by mass, the above-described effects cannot be sufficiently exhibited, and when the B content exceeds 0.030% by mass, the conductivity tends to decrease. Therefore, the B content is 0.001 to 0.030 mass%, preferably 0.001 to 0.020 mass%, more preferably 0.001 to 0.010 mass%.

<Cu: 0.01 to 1.00% by mass>, <Ag: 0.01 to 0.50% by mass>, <Au: 0.01 to 0.50% by mass>, <Mn: 0.01 to 1 0.00 mass%, <Cr: 0.01 to 1.00 mass%>, <Zr: 0.01 to 0.50 mass%> and <Ni: 0.01 to 0.50 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 Are elements that suppress the formation of abnormally grown 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 these is contained in an amount of 0.01% by mass or more, the above-described effects are obtained. Obtained, and the tensile strength and elongation can be improved. On the other hand, if any one of the contents of Cu, Ag, Au, Mn, Cr, Zr and Ni exceeds the above upper limit value, the compound containing the element becomes coarse and deteriorates the wire drawing workability. 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 the ranges specified above. Among these element groups, it is particularly preferable to contain Ni. When Ni is contained, the crystal 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 the wire drawing process are more easily suppressed. From the viewpoint of satisfying such effects in a balanced manner, the Ni content is more preferably 0.05 to 0.30% by 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% by mass, the conductivity and elongation are reduced. Further, the wire drawing workability deteriorates, and further, the wire handling property tends to decrease due to a 0.2% increase in yield strength. Therefore, the total content of these elements is preferably 2.00% by mass or less. In the aluminum alloy wire of the present invention, since Fe is an essential element, the total content of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr and Ni is 0.10 to 2.00% by mass. It is preferable to do this. However, when these elements are added alone, the larger the content, the more the compound containing the elements tends to become coarser, which deteriorates the wire drawing workability and easily causes disconnection. It was set as the content range prescribed | regulated above in the element.

  In order to moderately reduce the yield strength while maintaining high conductivity, the total content of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr and Ni is 0.10 to 0. .80% by mass is particularly preferable, and 0.15 to 0.60% by mass is more preferable. On the other hand, in order to further increase the tensile strength and elongation while appropriately reducing the proof stress value against the tensile strength, the total content is more than 0.80% by mass and 2.00%. It is especially preferable to set it as mass% or less, and it is still more preferable to set it as 1.00-2.00 mass%.

<Balance: Al and inevitable impurities>
The balance other than the components described above is Al (aluminum) and inevitable impurities. The inevitable impurities referred to here mean impurities in a content level that can be unavoidably included in the manufacturing process. Depending on the content of the inevitable impurities, it may be a factor for reducing the conductivity. Therefore, it is preferable to suppress the content of the inevitable impurities to some extent in consideration of the decrease in the conductivity. Examples of components listed as inevitable impurities include Ga (gallium), Zn (zinc), Bi (bismuth), and Pb (lead).

  Such an aluminum alloy wire can be realized by controlling the alloy composition and manufacturing process in combination. Hereinafter, the suitable manufacturing method of the aluminum alloy wire of this invention is demonstrated.

(2) Manufacturing method of aluminum alloy wire according to one embodiment of the present invention The aluminum alloy wire according to the present invention is characterized in that crystal grains are coarse and have a uniform structure.
Usually, since crystal grains grow during annealing, it is common to adjust the annealing conditions in order to obtain a coarse crystal grain structure (a structure with large crystal grains). However, the present inventors have found that a coarse crystal grain uniform structure (a crystal grain is large and uniform structure) can be realized by examining the processing rate in the wire drawing process, and have completed the present invention. Furthermore, as a result of further studies on the wire drawing, intermediate annealing, and solution treatment processes, the present inventors have maintained a low Young's modulus by adjusting these processes and controlling the crystal orientation. The present inventors have found that further increase in strength can be achieved.

  Such an aluminum alloy wire according to an embodiment of the present invention includes: [1] melting, [2] casting, [3] hot working (groove roll machining, etc.), [4] wire drawing, [5] final intermediate It can be manufactured by a manufacturing method including sequentially performing steps of heat treatment, [6] final wire drawing, [7] solution heat treatment, and [8] aging heat treatment. In addition, in order to determine the wire drawing rate before and after the final intermediate heat treatment, an intermediate heat treatment may be added in [4] wire drawing. Further, before or after solution heat treatment or after aging heat treatment, a step of forming a stranded wire (twisted wire processing) or a step of coating a wire with a resin may be provided. Hereinafter, the steps [1] to [8] will be described.

  First, FIG. 1 shows an example of an aluminum alloy wire manufacturing process flowchart. The steps indicated by broken lines in FIG. 1 are arbitrary steps, and are not limited to the description in FIG. 1, and the necessity, order, number of times, and the like can be changed as appropriate without departing from the effects 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 melted.

[2] Casting and [3] Hot working (groove roll processing, etc.)
Next, in the casting process, the cooling rate is increased, and the crystallization of the Fe-based compound is appropriately reduced and refined. Preferably, a rod having a diameter of 5 to 15 mm is used, for example, when the average cooling rate from the molten metal temperature during casting to 400 ° C. is 20 to 50 ° C./s and a Properti type continuous casting and rolling mill in which a cast wheel and a belt are combined is used. Can be obtained. Moreover, if the underwater spinning method is used, a rod having a diameter of 1 to 13 mm can be obtained at an average cooling rate of 30 ° C./s or more. Casting and hot working (rolling) may be performed by billet casting or extrusion. Further, after the casting or hot working, a reheat treatment at 400 ° C. or higher may be performed.

[4] Wire Drawing Next, the surface is peeled to obtain a bar having an appropriate thickness of, for example, a diameter of 5 to 12.5 mmφ, and this is cold drawn. Although the surface is cleaned by performing surface peeling, it may not be performed. In wire drawing, intermediate heat treatment may be added as necessary for the purpose of determining the wire drawing rate before and after the final intermediate heat treatment. Further, the wire drawing may be performed once or may be repeated a plurality of times until a target wire diameter is obtained. In the wire drawing until the final intermediate heat treatment, the processing rate is preferably 40 to 99.99%, and more preferably 95 to 99.99%. Here, the “processing rate” is {(cross-sectional area perpendicular to the longitudinal direction of the wire before drawing) − (after drawing (after the final drawing if there are multiple drawing)) The cross-sectional area perpendicular to the longitudinal direction of the wire)} × 100 / (cross-sectional area perpendicular to the longitudinal direction of the wire before drawing). By setting the processing rate in the wire drawing until the final intermediate heat treatment to 40% or more, the deviation angle from the {111} crystal orientation in the cross section perpendicular to the longitudinal direction of the obtained wire is oriented within 20 °. The crystal grain area ratio can be 50% or more, and the processing rate in the wire drawing until the final intermediate heat treatment is 95% or more, thereby occupying the {111} crystal orientation in the cross section. The area ratio of crystal grains oriented within an angle of deviation from 20 ° can be 90% or more.

[5] Final intermediate heat treatment Next, a final intermediate heat treatment is performed on the workpiece that has been cold drawn by wire drawing. The final intermediate heat treatment of the present embodiment is not only performed to regain the flexibility of the work material and enhance the wire drawing workability, but also compounds such as Fe, Mn, and Ni that have the role of pinning grain boundaries during solution treatment There is 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 for performing the final intermediate heat treatment include batch annealing. For the purpose of determining the wire drawing ratio before and after the final intermediate heat treatment [4] When adding an intermediate heat treatment in the wire drawing, the intermediate heat treatment is performed at a heat treatment temperature of 250 to 450 ° C., and the holding time is the above final time. It is preferable to adjust so as to be 2 to 5 hours in total with the intermediate heat treatment.

[6] Final wire drawing After the final intermediate heat treatment, wire drawing is further performed cold. In the final wire drawing, the processing rate is preferably 3 to 60%, and more preferably 3 to 30%. By setting the processing rate in the final wire drawing to 60% or less, the maximum value of the area of crystal grains can be set to 2000 μm ² or more in the cross section perpendicular to the longitudinal direction of the obtained wire. 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 processing rate and the crystal structure in the final wire drawing. In FIG. 2, an EBSD image is an image taken by analyzing a cross section perpendicular to the longitudinal direction of a wire corresponding to each processing rate by an EBSD method to be described later. Further, in FIG. 2, the crystal grain distribution chart is a graph obtained by measuring the area of the crystal grain based on the captured image, and the maximum value and coefficient of variation of the crystal grain area are analyzed as described above. 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 crystal grain area is 2000 μm ² or more in the cross section perpendicular to the longitudinal direction of the wire. In addition, a wire having a variation coefficient of 1.8 or less can be produced efficiently.
Note that the difference in crystal grain color in the EBSD image shown in FIG. 2 represents the difference in crystal orientation. That is, in the EBSD image, the more particles having the same color, the more crystal grains having the same crystal orientation.

[7] Solution heat treatment Further, a solution heat treatment is performed on the work material cold drawn by the final wire drawing. The solution heat treatment of the present embodiment is a heat treatment performed to dissolve a randomly contained Mg and Si compound in the aluminum matrix. Specifically, the solution heat treatment is performed by heating at a predetermined temperature in 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 to a temperature of at least 150 ° C. Heat treatment. When the predetermined temperature at the time of heating in the solution heat treatment is higher than 580 ° C., the crystal grains become coarse and abnormally grown grains are generated. When the predetermined temperature is lower than 500 ° C., Mg ₂ Si is sufficiently dissolved. I can't. Therefore, the predetermined temperature at the time of heating in the solution heat treatment is in the range of 500 to 580 ° C., and also varies depending on the contents of Mg and Si, but is preferably in the range of 500 to 540 ° C., more preferably in the range of 500 to 520 ° C. . Moreover, it is preferable that the time hold | maintained at the said predetermined temperature in solution heat processing shall be 10 second or more and 30 minutes or less, More preferably, it is 10-30 minutes.

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

If one or both of the wire temperature and heat treatment time are smaller than the conditions specified above, solute atom clusters, β ″ phase and Mg ₂ Si precipitates generated during incomplete aging heat treatment due to incomplete solution. If the numerical value of one or both of the wire temperature and heat treatment time is higher than the conditions specified above, the crystalline As the grains become coarser, partial melting (eutectic melting) of the compound phase in the aluminum alloy wire occurs, the tensile strength and elongation decrease, and breakage easily occurs during handling of the conductor.

[8] Aging heat treatment Next, an aging heat treatment is performed to form Mg, Si compounds or solute atom clusters. The aging heat treatment is performed at a predetermined temperature within a range of 20 to 250 ° C. If the predetermined temperature in the aging heat treatment is less than 20 ° C., the formation of solute atomic clusters is slow, and it takes time to obtain the necessary tensile strength and elongation, which is disadvantageous in mass production. On the other hand, when the predetermined temperature is higher than 250 ° C., in addition to the Mg ₂ Si needle-like precipitate (β ″ phase) that contributes most to the strength, coarse Mg ₂ Si precipitates are generated and the strength is lowered. Therefore, the above-mentioned predetermined temperature is preferably 20 to 70 ° C. when a solute atom cluster that is more effective in improving the elongation is generated, and the β ″ phase is also precipitated at the same time, and the tensile strength and elongation are increased. When taking a balance, it is preferable to set it as 100-150 degreeC.

  Furthermore, 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 for improving tensile strength and elongation. In the long-time heating, for example, it is within 10 days, and in the short-time heating, it 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 if it cannot cool quickly in the manufacturing process, it can be appropriately set as long as it is an aging condition that can sufficiently generate the solute atom clusters.

  In the aluminum alloy wire of this embodiment, the wire diameter is not particularly limited and can be appropriately determined according to the application, but in the case of a thin wire, 0.1 to 0.5 mmφ, in the case of a medium thin wire It is preferable to set it as 0.8-1.5 mmphi. The aluminum alloy wire of this embodiment is one of the advantages that it can be used as an aluminum alloy wire by thinning it with a single wire, but it can also be used as an aluminum alloy twisted wire obtained by bundling a plurality of wires, Among the steps [1] to [8] constituting the production method of the present invention, after the aluminum alloy wire materials obtained by sequentially performing the steps [1] to [6] are bundled and twisted, 7) Solution heat treatment and [8] aging heat treatment may be performed.

  Moreover, in this embodiment, it is also possible to perform the homogenization heat processing which is performed by the conventional method after a casting process or after hot working as an additional process. Homogenization heat treatment makes it possible to uniformly disperse the added elements, which makes it easier to form solute atomic clusters and β ”precipitated phases in the subsequent solution heat treatment, improving tensile strength and elongation, and tensile strength. A moderate low proof stress value can be obtained more stably for the homogenization heat treatment, preferably at a heating temperature of 450 to 600 ° C., more preferably 500 to 600 ° C. Further, the homogenization heat treatment In the cooling, it is preferable to gradually cool at an average cooling rate of 0.1 to 10 ° C./min because a uniform compound is easily obtained.

(3) Organizational characteristics of the aluminum alloy wire of the present invention The aluminum alloy wire of the present embodiment manufactured by the manufacturing method as described above has a maximum area of crystal grains in a cross section perpendicular to the longitudinal direction of the wire. 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 boundary is defined as “crystal grain”. Further, the longitudinal direction of the wire is an axial direction perpendicular to the wire diameter, and corresponds to the wire drawing direction when the wire is manufactured.

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 crystal grain area is preferably 2000 to 30000 μm ² , and more preferably 2000 to 8000 μm ² .

  The coefficient of variation is an index by which the uniformity of crystal grains can be compared in a state where the dependence on the crystal grain size is small. Therefore, by setting the coefficient of variation to 1.8 or less, it is possible to make the particle size uniform, thereby realizing a low Young's modulus while 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).

The area ratio of 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 as the said range, Young's modulus can be maintained low.

  In addition, the area ratio of the crystal grains in which the deviation angle from the {111} crystal orientation in the cross section is within 20 ° is preferably 50% or more, and more preferably 90% or more. Here, the above-mentioned 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 crystal grain area, grain size, and crystal orientation as described above is performed by image analysis using the EBSD method. EBSD is an abbreviation for Electron Back Scatter Diffraction (Electron Backscatter Diffraction). Reflected electron Kikuchi line diffraction (Kikuchi pattern) that occurs when a sample is irradiated with an electron beam in a scanning electron microscope (SEM). This is the crystal orientation analysis technology used. In the present invention, a surface perpendicular to the longitudinal direction of the wire material as a sample (a surface parallel to the wire diameter) is scanned in steps of 2 μm, and analysis software (EDAX / TSL (currently AMETEK), product name, "Orientation Imaging Microscopy v5") is used to analyze the crystal grain area and crystal orientation 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 the foreign matter adhering to the measurement surface and simultaneously perform mirror finishing. Examples of the mirror finishing method include a method of polishing a cross section by CP (cross section polisher) processing.

(4) Characteristics of the aluminum alloy wire of the present invention In order to prevent heat generation due to Joule heat, the electrical conductivity is preferably 45% IACS or more, more preferably 50% IACS or more. The higher the electrical conductivity, the better the diameter reduction.

  The Young's modulus is preferably 70 GPa or less, more preferably 68 Pa or less. The lower the Young's modulus, the higher the flexibility and the better the handling properties, so that the load on the operator is reduced and the installation work becomes more efficient.

  Further, as in the prior art, since high tensile strength is required in order to enable use without breaking even when applied to a thin wire having a small cross-sectional area, the tensile strength is preferably 150 MPa or more. 200 MPa or more is more preferable.

  In addition, the measuring method of each said characteristic is demonstrated in the Example mentioned later.

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

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, All the aspects included in the concept of this invention and a claim are included, and various within the scope of this invention. Can be modified.

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

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

This alloy material was rolled using a Properti-type continuous casting rolling machine while continuously casting the molten metal under the conditions shown in Table 2 using a mold in which the molten metal was water-cooled to obtain a bar having a diameter of 9.5 mm. Next, this was drawn so that the processing rates shown in Table 2 were obtained.
Next, the processed material subjected to the wire drawing is subjected to final intermediate heat treatment under the conditions shown in Table 2, and the final wire drawing is performed so that the processing rate shown in Table 2 is obtained up to a wire diameter of φ0.3 mm. went.
Next, solution heat treatment was performed on the processed material subjected to the final wire drawing under the conditions shown in Table 2.
In the batch type heat treatment in the final intermediate heat treatment and the 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 becomes the highest, so the fiber type radiation thermometer (manufactured by Japan Sensor Co., Ltd.) is in front of the part where the temperature of the wire becomes the highest. The temperature was measured, and the maximum temperature reached was calculated in consideration of Joule heat and heat dissipation. In the high frequency heating and continuous running heat treatment, the wire temperature near the exit of the heat treatment section was measured.
Furthermore, an aging heat treatment was performed on the processed material subjected to the solution heat treatment under the conditions shown in Table 2 to produce an aluminum alloy wire (wire diameter: 300 μm).

(Evaluation)
The aluminum alloy wires according to the above examples and comparative examples were measured and evaluated as follows. Each evaluation condition is as follows. The results are shown in Table 3.

[Observation of crystal grains and analysis of crystal orientation]
The observation of the crystal grains and the analysis of the crystal orientation were performed by electron beam backscatter diffraction (EBSD) using a Schottky field emission scanning electron microscope (JSM-7001F, manufactured by JEOL Ltd. (JEOL)). As a measurement sample, a wire having a diameter of 300 μm was prepared, CP (cross section polisher) processing was performed after resin filling, and a cross section perpendicular to the longitudinal direction of the wire was cut out to obtain an observation surface. The scan step during measurement was 2 μm. Further, this measurement was performed on 10 observation planes per one alloy wire. As shown in FIG. 3, the method of cutting out the 10 observation planes is to first cut out a cross section of an arbitrary portion N1, then cut out a cross section of a portion N2 separated by 500 mm, and then look at the cross section of N2 to see N1 A cross section of a portion N3 that is 500 mm away in the direction opposite to the cross section is cut. A cross section was cut out to N10 in the same manner, 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 (manufactured by EDAX / TSL (currently AMETEK), trade name “Orientation Imaging Microscopy v5”) was used. In addition, the definition of crystal grain boundary is an interface between crystals having an angle difference of 15 ° or more, and after calculating all crystal grain areas, the area of crystal grains having an area of 2000 μm ² or more in a cross section perpendicular to the longitudinal direction of the wire Each of the ratio, standard deviation (a), average crystal grain size (b), and coefficient of variation (a / b) was determined, and each average value (N = 10) was calculated.
Further, according to the above image analysis, the area ratio of the crystal grains in which the deviation angle from the {111} crystal orientation is within 20 ° in the cross section perpendicular to the longitudinal direction of the wire [[deviation from the {111} crystal orientation] The area of crystal grains oriented within an angle of 20 ° × 100 / (area of the cross section perpendicular to the longitudinal direction of the wire)] was determined, and the average value (N = 10) was calculated. Further, the area ratio of crystal grains oriented within 20 ° of the deviation angle from the {100} crystal orientation and the area percentage of crystal grains oriented within 20 ° of the deviation angle from the {101} crystal orientation are also {111 } Average values (each N = 10) were calculated by the same method as in the case of crystal orientation.

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

[Tensile strength]
In accordance with JIS Z 2241: 2011, tensile tests were performed on test pieces (three for each wire), tensile strength was calculated (MPa), and an average value (N = 3) was obtained. In this example, 150 MPa or more was set as an acceptable level.

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

[Elongation]
In accordance with JIS Z2241: 2011, tensile tests were performed on test pieces (three for each wire), elongation was calculated (%), and an average value (N = 3) was obtained. The larger the elongation, the better, and more preferably 5% or more.

From the results of Table 3, in each aluminum alloy wire, various conditions relating to the maximum value of the crystal grain area, 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 wires of Examples 1 to 7 have a predetermined alloy composition, and in the cross section perpendicular to the longitudinal direction of the wire, the maximum value of the crystal grain area is 2000 μm ² or more and the variation coefficient is 1.8. Since it was controlled to be as follows, it was confirmed that all exhibited high conductivity, high strength, and low Young's modulus.

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

Claims (13)

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 to 0 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: 0 to 0 1.00 mass%, Zr: 0 to 0.50 mass%, Ni: 0 to 0.50 mass%, balance: aluminum alloy wire having a chemical composition consisting of Al and inevitable impurities,
An aluminum alloy wire characterized by 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. The aluminum alloy wire 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 according to claim 2, wherein an area ratio of crystal grains in which the deviation angle from the {111} crystal orientation in the cross section is within 20 ° is 50% or more.   The aluminum alloy wire according to claim 2 or 3, wherein an area ratio of crystal grains in which the deviation angle from the {111} crystal orientation occupies the cross section is within 20 ° is 90% or more.   The aluminum alloy wire according to any one of claims 1 to 4, wherein the electrical conductivity is 45% IACS or more, the tensile strength is 150 MPa or more, and the Young's modulus is 70 GPa or less.   The chemical composition according to any one of claims 1 to 5, wherein the chemical composition contains any one element 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% by mass, Ag: 0.01 to 0.50% by mass, Au: 0.01 to 0.50% by mass, Mn: 0.01 to 1.00. It contains at least one element among mass%, Cr: 0.01-1.00 mass%, Zr: 0.01-0.50 mass%, and Ni: 0.01-0.50 mass%. Item 7. The aluminum alloy wire according to any one of items 1 to 6.   The aluminum alloy wire according to any one of claims 1 to 7, wherein the chemical composition contains Ni: 0.01 to 0.50 mass%.   The total content of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, and Ni is 0.10 to 2.00% by mass, according to any one of claims 1 to 8. Aluminum alloy wire.   The aluminum alloy wire according to any one of claims 1 to 9, which is an aluminum alloy wire having an element wire diameter of 0.1 to 0.5 mm.   An aluminum alloy twisted wire obtained by twisting a plurality of the aluminum alloy wires according to claim 10.   The covered electric wire which has a coating layer in the outer periphery of the aluminum alloy wire of Claim 10, or the aluminum alloy twisted wire of Claim 11. A wire harness comprising the covered electric wire according to claim 12 and a terminal attached to an end of the covered electric wire from which the covering layer is removed.

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