JP2014118624A - Aluminum alloy sheet for bus bar and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a bus bar excellent in creep resistance and bendability while maintaining conductivity, and to provide its manufacturing method.SOLUTION: An aluminum alloy sheet is constituted by an aluminum alloy containing Si:0.3 to 1.5 mass%, Mg:0.3 to 1.0 mass% and the balance Al with inevitable impurities, has conductivity of 45.0% IACS or more, a Cube orientation distribution density of a sheet surface by a crystal orientation distribution function analysis of 45 or more to random orientations, and an average crystal particle diameter in a rolling direction on the sheet surface of 150 μm or less.

Description

  The present invention electrically connects between electric devices (batteries, inverters, motors, etc.) mounted on various electric transportation devices using electricity as a power source such as an electric vehicle or between components inside the electric device. The present invention relates to an aluminum alloy plate for connecting parts used for connecting parts to be connected and a method for manufacturing the same.

  Various electric devices such as a battery group, an inverter, and a motor are mounted on various electric transport devices (such as hybrid vehicles, fuel cell vehicles, and electric locomotives) that use electricity as a power source, including electric vehicles. In order to electrically connect between these electric devices or between the components in the electric device, a connecting component called a bus bar is used.

Since this connection component must conduct electricity, it is naturally necessary to have excellent conductivity.
Further, when the connecting part is connected by a connecting tool such as a bolt, deformation (creep deformation) of the connecting part 1a (see FIG. 1) of the connecting part 1 occurs due to heat generation when energized, so that the tightening torque of the connecting tool is increased. The connecting parts must have a high creep resistance so that they do not drop and the couplings come loose or come off.
Furthermore, in order to satisfy the demand for space saving (miniaturization) of electrical equipment, the connecting component is often designed in a shape having a curved portion with a small bending radius (R). Therefore, the connection component needs to be excellent in bending workability.

Up to now, copper-based materials have been studied for connecting parts that satisfy the above conditions.
However, in recent years, in order to reduce the fuel consumption of automobiles, it has been required to reduce the weight of automobiles and, in turn, to reduce the weight of electrical devices mounted on automobiles.
In view of the above circumstances, connecting parts made of an aluminum alloy that is lighter than copper have been proposed.

  For example, Patent Document 1 discloses an aluminum alloy for connection parts that specifies the component composition and specifies the conditions of conductivity and tempering. Patent Document 1 describes that the aluminum alloy has excellent conductivity and excellent creep resistance.

  Patent Document 2 discloses a method for producing an aluminum alloy sheet in which a homogenized heat treatment, hot rolling, cold rolling, and final annealing under predetermined conditions are performed on an ingot with a specified component composition. And in patent document 2, it describes that the aluminum alloy plate manufactured with the said manufacturing method has the bending workability requested | required of a printed circuit board.

  Further, in Patent Documents 3 and 4, although it is a technique related to an aluminum alloy plate for an automobile panel, not for a connection part, in order to improve the bending workability of an Al—Mg—Si based alloy (JIS6000 based Al alloy). In addition, a technique in which the texture is controlled to set the Cube orientation distribution density to a predetermined value (Patent Document 3) or a crystal grain having an orientation difference of 20 ° or less with respect to the total grain boundary length between all crystal grains. A technique for specifying the intergranular length (Patent Document 4) is disclosed.

Japanese Patent No. 3557116 JP 2009-242813 A JP 2005-298922 A Japanese Patent No. 3749687

  However, although the technique disclosed in Patent Document 1 is a technique that focuses on the improvement of creep resistance, it is a technique that does not consider bending workability at all (see paragraph 0010 of Patent Document 1). Naturally, the bending workability required for the connecting parts could not be satisfied. Therefore, when the technique disclosed in Patent Document 1 is applied to a connection part, a bending crack may occur on the surface during molding.

  Further, although the technique disclosed in Patent Document 2 is a technique that focuses on the improvement of bending workability, it is a technique that does not consider creep resistance at all (see paragraph 0001 and the like in Patent Document 2). Of course, the creep resistance required for the connecting parts could not be satisfied. Therefore, when the technique disclosed in Patent Document 2 is applied to a connection component, a connecting portion 1a (see FIG. 1) of the connection component 1 is deformed by heat generated during energization, so that a bolt or the like for connecting the connection component can be obtained. There is a possibility that the connector will loosen or come off.

  Note that the techniques disclosed in Patent Documents 3 and 4 consider bending workability as well as Patent Document 2, but do not consider creep resistance at all, and are not for connecting parts. It is a technology for automobile panels. Therefore, the techniques disclosed in Patent Documents 3 and 4 do not satisfy the creep resistance required for connecting parts. Furthermore, even if it has the bending workability required for an automobile panel having a plate thickness of about 1 mm, the connecting part usually has a plate thickness of about 2 mm, so that it has a high bending workability as required for the connecting part. Hard to think.

As can be seen from the descriptions in Patent Documents 1 to 4, the aluminum alloy plate has both the creep resistance and the bending workability required for the connection parts while maintaining the conductivity that is an essential characteristic for the connection parts. No technology seems to exist.
In addition, this situation is technical common sense (in order to improve the creep resistance of a plate made of metal, it is necessary to improve the strength, but if the strength is improved, the bending workability of the plate will be reduced, that is, The creep resistance and the bending workability are in a trade-off relationship) and have been considered as a matter of course.

  Then, this invention makes it a subject to provide the aluminum alloy plate for connection components which is excellent also in creep resistance and bending workability, and its manufacturing method, hold | maintaining electroconductivity.

  In order to solve the above-mentioned problems, the inventors of the present invention show that the Cube orientation distribution density and the component composition on the surface of the aluminum alloy plate for connecting parts have a great influence on the creep resistance and bending workability. And found the present invention.

  That is, the aluminum alloy plate for connecting parts according to the present invention contains Si: 0.3 to 1.5 mass%, Mg: 0.3 to 1.0 mass%, and the balance is made of Al and inevitable impurities. It is made of an aluminum alloy, has a conductivity of 45.0% IACS or more, a Cube orientation distribution density of the plate surface by a crystal orientation distribution function analysis of 20 or more, and an average crystal grain size in the rolling direction on the plate surface of 150 μm or less. It is characterized by that.

According to the aluminum alloy plate for connecting parts, since the Cube orientation distribution density on the surface of the plate is specified more than a predetermined value, the creep resistance can be improved and the bending workability can be improved. That is, according to the aluminum alloy plate for connecting parts, both creep resistance and bending workability required for the connecting parts can be achieved. Furthermore, the bending surface quality can be improved by reducing the crystal grain size.
Moreover, according to this aluminum alloy plate for connection parts, since the content of Si and Mg is specified within a predetermined range, the effect of improving creep resistance can be ensured.
Furthermore, according to this aluminum alloy plate for connection parts, since the electrical conductivity is specified to be 45.0% IACS or more, the electrical conductivity required for the connection parts can be ensured.

  Moreover, it is preferable that the aluminum alloy plate for connection components which concerns on this invention is less than Fe: 0.5 mass% and Zn: less than 0.5 mass% among the inevitable impurities.

  According to this aluminum alloy plate for connecting parts, the content of Fe and Zn among inevitable impurities is specified to be less than a predetermined value, so that the effect of improving the bending workability can be ensured. it can.

  In the aluminum alloy plate for connecting parts according to the present invention, the aluminum alloy contains Cu: less than 1.0% by mass, Mn: less than 1.0% by mass, Cr: less than 0.5% by mass, Zr: 0.0. It is preferable to further contain one or more selected from less than 3% by mass and Ti: less than 0.1% by mass.

  According to this aluminum alloy plate for connecting parts, since it further contains one or more selected from Cu, Mn, Cr, Zr, Ti less than a predetermined value, while ensuring the effect of improving the bending workability, The effect of improving the creep resistance can be further ensured.

  The method for producing an aluminum alloy plate for connecting parts according to the present invention includes a homogeneous heat treatment step of subjecting an ingot made of the aluminum alloy to a homogenization heat treatment at 500 to 570 ° C. for 1 to 24 hours, and the homogenization heat treatment. A hot rolling step of producing a hot rolled sheet by rolling a plurality of passes with a rolling start temperature of 350 to 450 ° C. on the ingot, and without subjecting the hot rolled sheet to cold rolling And a solution heat treatment step for performing a solution heat treatment for holding at 500 to 570 ° C. for 100 seconds or less, and an artificial aging treatment step for subjecting the hot-rolled sheet subjected to the solution heat treatment to an artificial aging treatment. And

  According to this method of manufacturing an aluminum alloy plate for connecting parts, the component composition of the aluminum alloy to be used is specified, the conditions for the homogenization heat treatment, hot rolling and solution heat treatment are specified, and cold rolling is not performed. Thus, the electrical conductivity, the Cube orientation distribution density and the proof stress of the aluminum alloy plate for connecting parts manufactured by the manufacturing method can be set to a predetermined value or more and the crystal grain size can be set to a predetermined value or less.

  According to the aluminum alloy plate for connecting parts according to the present invention, the conductivity, the Cube orientation distribution density of the plate surface is specified as a predetermined value or more, and the contents of Si and Mg are specified in a predetermined range. Since it retains conductivity and is excellent in creep resistance and bending workability, it can be suitably used as a connection part.

  Moreover, according to the manufacturing method of the aluminum alloy plate for connecting parts according to the present invention, the composition of the aluminum alloy to be used is specified, the conditions for the homogenization heat treatment and the solution heat treatment are specified, and cold rolling is not performed. As a result, it is possible to produce an aluminum alloy plate for connecting parts that is excellent in creep resistance and bending workability while maintaining conductivity.

It is a perspective view of the connection component (bus bar) concerning the embodiment of the present invention. It is a flowchart of the manufacturing method of the aluminum alloy plate for connection components which concerns on this invention. It is a schematic diagram explaining the method of the bending test in the Example of this invention.

  Hereinafter, the form for implementing the aluminum alloy plate for connection components which concerns on this invention, and its manufacturing method is demonstrated in detail.

[Aluminum alloy plate for connecting parts]
An aluminum alloy plate for connecting parts according to the present invention (hereinafter, appropriately referred to as an aluminum alloy plate) contains a predetermined amount of Si and Mg, and the balance is made of an aluminum alloy composed of Al and inevitable impurities, and has a conductivity, And the Cube orientation distribution density of the plate surface is not less than a predetermined value and the crystal grain size is not more than a predetermined value.
Further, the aluminum alloy plate for connecting parts according to the present invention preferably has Fe and Zn of unavoidable impurities less than a predetermined value, and is selected from Cu, Mn, Cr, Zr, and Ti that are less than a predetermined value. More preferably, it contains seeds or more.
Hereinafter, the reason why the respective alloy components, conductivity, Cube orientation distribution density on the plate surface, and crystal grain size of the aluminum alloy plate for connecting parts according to the present invention are numerically limited will be described.

(Si: 0.3-1.5% by mass)
Si forms aging precipitates together with Mg during the artificial aging treatment after solution heat treatment. Since Si inhibits the movement of dislocations in a high temperature environment and improves creep resistance, Si is an essential element for the aluminum alloy plate for connecting parts according to the present invention.
If the Si content is less than 0.3% by mass, desired creep resistance cannot be obtained. On the other hand, when the Si content exceeds 1.5% by mass, coarse crystallized substances and precipitates are formed, and particularly bending workability is deteriorated.
Therefore, the Si content is 0.3 to 1.5 mass%.
In addition, in order to ensure the effect of improving bending workability and creep resistance, the content of Si is preferably 0.4 to 1.5% by mass, and 0.5 to 1.3% by mass. % Is more preferable.

(Mg: 0.3-1.0% by mass)
Mg forms an aging precipitate during the artificial aging treatment after solution heat treatment with Si. Since Mg inhibits the movement of dislocations under a high temperature environment and improves creep resistance, Mg is an essential element for the aluminum alloy plate for connecting parts according to the present invention.
If the Mg content is less than 0.3% by mass, desired creep resistance cannot be obtained. On the other hand, when the Mg content exceeds 1.0% by mass, coarse crystallized substances and precipitates are formed, and bending workability is particularly deteriorated.
Therefore, the Mg content is 0.3 to 1.0 mass%.
In addition, in order to make the effect of improvement of bending workability and creep resistance more reliable, the content of Mg is preferably 0.5 to 0.8% by mass.

(Inevitable impurities)
As an unavoidable impurity, Fe, Zn, or the like may be contained within a range that does not hinder the effects of the present invention. Specifically, Fe and Zn are each preferably less than 0.50% by mass (restricted to less than 0.50% by mass). This is because if the Fe content or Zn content is 0.50% by mass or more, the bending workability or the corrosion resistance is lowered.
Since Fe and Zn are contained to some extent in scrap and recycled bullion (for example, scraps of aluminum alloy materials for clad materials such as brazing sheets), scrap and recycled bullion are produced during production (dissolution). And, it can mix | blend in the grade from which the content of Fe and Zn in an aluminum alloy plate becomes less than the said range, and can reduce raw material cost.
Moreover, elements other than Fe and Zn may be contained as unavoidable impurities to the extent that the effects of the present invention are not hindered.

(Cu: less than 1.00% by mass)
Cu accelerates aging precipitate formation in the artificial aging treatment after the solution heat treatment. By inhibiting the movement of dislocations in a high temperature environment, Cu improves creep resistance.
In order to acquire the said effect, it is preferable to contain Cu 0.05 mass% or more.
On the other hand, if the Cu content is 1.00% by mass or more, the stress corrosion cracking resistance, weldability, and bending workability are remarkably deteriorated.
Therefore, when Cu is contained in the aluminum alloy plate, the Cu content is less than 1.00% by mass.

(Mn: less than 1.00% by mass)
Mn generates dispersed particles (dispersed phase) during the homogenization heat treatment, and these dispersed particles hinder grain boundary movement after recrystallization. Therefore, Mn is an element that has an effect of refining crystal grains. In addition, the bending workability of the aluminum alloy plate for connection parts according to the present invention improves as the crystal grains of the aluminum alloy structure become finer.
In order to acquire the said effect, it is preferable to contain 0.01 mass% or more of Mn.
On the other hand, when the content of Mn is 1.00% by mass or more, coarse Al-Fe-Si-Mn-based crystallized products are easily generated during melting and casting, which causes a decrease in bending workability.
Therefore, when Mn is contained in the aluminum alloy plate, the Mn content is less than 1.00% by mass.

(Cr: less than 0.50% by mass)
Cr, like Mn, produces dispersed particles (dispersed phase) during the homogenization heat treatment, and these dispersed particles hinder grain boundary movement after recrystallization. Therefore, Cr is an element that has an effect of refining crystal grains.
In order to acquire the said effect, it is preferable to contain 0.01 mass% or more of Cr.
On the other hand, if the Cr content is 0.50% by mass or more, a coarse intermetallic compound is likely to be produced during melting and casting, and the bending workability is deteriorated.
Therefore, when Cr is contained in the aluminum alloy plate, the Cr content is less than 0.50% by mass.

(Zr: less than 0.30% by mass)
Zr, like Mn, generates dispersed particles (dispersed phase) during the homogenization heat treatment, and these dispersed particles hinder grain boundary movement after recrystallization. Therefore, Zr is an element that has an effect of refining crystal grains.
In order to acquire the said effect, it is preferable to contain Zr 0.01 mass% or more.
On the other hand, when the Zr content is 0.30 mass% or more, a coarse intermetallic compound is likely to be produced during melting and casting, and bending workability is deteriorated.
Therefore, when Zr is contained in the aluminum alloy plate, the content of Zr is less than 0.30% by mass.

(Ti: less than 0.10% by mass)
Ti is an element having the effect of making the crystal grains of the ingot finer and improving the bending workability by containing a small amount of Ti.
In order to acquire the said effect, it is preferable to contain Ti 0.01 mass% or more.
On the other hand, if the Ti content is 0.10% by mass or more, a coarse compound is formed and bending workability is deteriorated.
Therefore, when Ti is contained in the aluminum alloy plate, the Ti content is less than 0.10% by mass.

(Conductivity: 45.0% IACS or higher)
The electrical conductivity of the aluminum alloy plate for connecting parts according to the present invention is 45.0% IACS or more.
When the electrical conductivity is 45.0% IACS or more, electrical conductivity as a connected device can be ensured. On the other hand, if the electrical resistance is high, that is, the conductivity is less than 45.0% IACS, it is necessary to increase the cross-sectional area of the connecting component in order to flow a desired current, leading to an increase in the component weight.
The conductivity is preferably as high as possible, preferably 47.0% IACS or more, and more preferably 50.0% IACS or more.

The adjustment of conductivity is achieved by controlling the Si content, Mg content, homogenization heat treatment conditions, solution heat treatment conditions, and artificial aging conditions in the aluminum alloy sheet manufacturing process. The
If the conductivity is too high, that is, the creep resistance tends to decrease due to excessive decrease in the amount of solid solution and coarsening of precipitates, the conductivity is preferably 60% IACS or less.

(Cube orientation distribution density: 20 or more)
The Cube orientation distribution density on the plate surface of the aluminum alloy plate for connection parts according to the present invention is 20 or more.
When the Cube orientation distribution density on the surface of the plate is 20 or more, both creep resistance and bending workability required for connecting parts can be achieved. On the other hand, if the Cube orientation distribution density on the surface of the plate is less than 20, bending workability is deteriorated.
The Cube orientation distribution density is preferably 30 or more, and more preferably 50 or more, in order to ensure the effect of improving creep resistance and bending workability.

According to a general manufacturing method, the Cube orientation distribution density is less than 20, which indicates that the crystal orientation of the plate surface is relatively random.
On the other hand, as specified by the present invention, when the Cube orientation distribution density is 20 or more, that is, when the Cube orientation is accumulated more than a certain amount, the proportion of small-angle grain boundaries having a small orientation difference between adjacent crystal grains increases. Reduce or eliminate grain boundary step during deformation.
In addition, in the Cube orientation, since a uniform slip deformation is possible compared to other orientations, formation of a shear band is suppressed.
As a result, since the formation of a shear boundary in the grain boundary step and the crystal grain which becomes the starting point or propagation path of the crack during bending is suppressed, the bending workability can be improved by setting the Cube orientation distribution density to 20 or more. Can improve (improve).
If the Cube orientation distribution density is excessively increased, the manufacturing conditions become severe and the productivity is lowered. Therefore, the Cube orientation distribution density is preferably 100 or less.

  Further, by setting the Cube orientation distribution density to 20 or more, even when compared with the same level of proof stress, the creep resistance required for the connecting parts can be improved. Although the reason for this is not necessarily clear, it is known that the Cube orientation has a small Taylor factor and a small amount of dislocation momentum (Tatsumi et al .: Light Metals, 49 (1999), P. 583). It is presumed that the recovery during holding is suppressed.

  In the present invention, when defining the Cube orientation distribution density, the Cube orientation distribution density is defined by a Cube orientation distribution density by crystal orientation distribution function analysis (hereinafter, referred to as ODF analysis as appropriate) with more accurate measurement of the crystal texture.

  The Cube orientation distribution density by ODF analysis can express a wide range quantitatively because the Cube orientation is represented by a ratio (dimensionalless) from a random orientation (non-oriented Al powder sample of a standard sample). On the other hand, in the measurement based on the integrated intensity, since the in-plane (100 plane) rotational orientation cannot be separated, only a pure Cube orientation cannot be extracted.

  The measurement of the Cube orientation distribution density by ODF analysis on the plate surface of this aluminum alloy plate is performed using, for example, an X-ray diffractometer manufactured by Rigaku Corporation [model “Rigaku RAD-rX” (Ru-200B)]. This is done by measuring. The X-ray diffractometer can perform ODF analysis with an incomplete pole figure. That is, incomplete pole figures of {100} plane and {111} plane are created by schluz reflection method, ODF analysis is performed by applying Bunge's iterative series expansion method (positivity method), and Cube orientation distribution density Can be requested.

The relationship between the bending direction and the Cube orientation (orientation direction) when bending the aluminum alloy plate is set so that the Cube orientation of the plate is parallel to the bending direction of the plate (the bending direction of the plate is the material plate). When the material is bent (parallel or perpendicular to the rolling direction), the Cube orientation during deformation becomes stable, and good bending workability is obtained. Since the Cube orientation of the plate has the same structure even when rotated 90 degrees, there is no distinction between 0 degrees and 90 degrees. For this reason, even if the bending direction of the plate is parallel or perpendicular to the rolling direction of the material plate, the Cube orientation has the same structure, and good bending workability can be obtained.
However, in the relationship between the bending direction of the plate other than the above two directions and the Cube orientation (distribution direction) of the plate, such as the rolling direction of the plate being 45 degrees with the bending direction of the plate, the Cube orientation is being deformed. Since the crystal orientation is randomized and the bending workability may be inferior, it is preferable that the bending direction of the plate when bending is the above two directions.

  The adjustment of the Cube orientation distribution density on the surface of the plate is achieved by the Si content, the Mg content, the hot rolling conditions in the manufacturing process of the aluminum alloy plate, and the absence of cold rolling. .

(Average grain size in rolling direction: 150 μm or less)
The aluminum alloy plate for connecting parts according to the present invention has an average crystal grain size in the rolling direction on the plate surface of 150 μm or less.
When the average grain size in the rolling direction is 150 μm or less, the surface quality during bending can be improved. On the other hand, if the average crystal grain size in the rolling direction exceeds 150 μm, the possibility of rough skin and cracks on the surface during bending increases.
The average crystal grain size in the rolling direction is preferably 100 μm or less, and more preferably 50 μm or less, in order to ensure the effect of improving the surface quality during bending. Further, the average crystal grain size in the rolling direction is preferably 10 μm or more because manufacturing conditions become stricter and productivity is lowered when trying to make it excessively small.

  The average particle size in the rolling direction can be measured by cutting a measurement piece from an aluminum alloy plate, polishing the plate surface, etching with an electrolytic solution, and then observing it at about 100 times with an optical microscope.

  The average grain size in the rolling direction is achieved by controlling the hot rolling start temperature and rolling end temperature in the production process of the aluminum alloy sheet.

(Yield strength: 180 MPa or more)
The proof stress (0.2% proof stress) of the aluminum alloy plate for connecting parts according to the present invention is preferably 180 MPa or more.
When the proof stress is 180 MPa or more, the creep resistance required for the connecting parts can be ensured. On the other hand, when the yield strength is less than 180 MPa, the creep resistance is lowered.
In order to secure the effect of ensuring creep resistance, the yield strength is preferably 190 MPa or more, and more preferably 195 MPa or more.

  The adjustment of the proof stress is achieved by the Si content in the aluminum alloy plate, the Mg content, the homogenization heat treatment condition, the solution treatment condition and the artificial aging treatment condition in the production process of the aluminum alloy sheet.

(Connecting parts)
The connection component is a component that electrically connects a plurality of members. Specifically, it is a bus bar that is electrically connected to various electric devices such as battery groups, inverters, motors, etc. is there.
And although a bus bar is not specifically limited about a shape, while it has predetermined thickness, it is a component which exhibits plate shape or a square material shape. For example, the bus bar is a component having a shape as shown in FIG.

Here, since aluminum has a lower conductivity than copper, the bus bar made of aluminum alloy has to have a larger cross-sectional area than the bus bar made of copper in order to ensure the conductive performance. When considering the installation area of the component, it is often difficult to increase the width of the component, and the plate thickness increases. In general, when the plate thickness increases, the amount of deformation on the bending surface increases, so the bus bar made of an aluminum alloy has a problem of occurrence of bending cracks during bending processing. The problem that workability must be improved will clearly appear.
In other words, the aluminum alloy plate for connection parts according to the present invention is preferably applied to a bus bar having a thickness of 1.5 mm or more, in particular, 1.8 to 5.0 mm, among the connection parts. Effect of achieving both creep resistance and bending workability).

Next, the manufacturing method of the aluminum alloy plate for connection parts which concerns on this invention is demonstrated, referring FIG.
[Method of manufacturing aluminum alloy plate for connecting parts]
The method for producing an aluminum alloy plate for connecting parts according to the present invention includes a homogenization heat treatment step S2, a hot rolling step S3, a solution heat treatment step S4, and an artificial aging treatment step S5. .
Hereinafter, the respective steps will be mainly described.

(Casting process)
In the casting step S1, an aluminum alloy having the above component composition is melted, cast by a known casting method such as a DC forging method, cooled to below the solidus temperature of the aluminum alloy, and cast to a thickness of about 400 to 600 mm. Make a lump and chamfer as necessary.

(Homogenization heat treatment process)
In the homogenization heat treatment step S2, homogenization heat treatment (soaking) is performed at a predetermined temperature before rolling the ingot cast in the casting step S1. By subjecting the ingot to homogenization heat treatment, internal stress is removed, solute elements segregated at the time of casting are homogenized, and intermetallic compounds precipitated at the time of casting cooling and thereafter grow.
The heat treatment temperature (ingot temperature) in the homogenization heat treatment step S2 is 500 to 570 ° C. When the heat treatment temperature is less than 500 ° C., Si or Mg crystallized at the time of casting remains undissolved, and an appropriate precipitate distribution cannot be obtained after solution heat treatment and artificial aging treatment, yield strength and creep resistance. Decreases. On the other hand, when it exceeds 570 ° C., local melting (burning) occurs on the surface of the ingot. More preferably, it is 560 degrees C or less.
The heat treatment time (holding time) in the homogenization heat treatment step S2 may be 1 hour or longer in order to complete the homogenization, and may be within 24 hours from the viewpoint of production efficiency.

(Hot rolling process)
In the hot rolling step S3, the homogenized ingot is hot rolled. The rolling start temperature at this time shall be 350-450 degreeC. By performing hot rolling consisting of a plurality of passes, a hot rolled plate (hot coil) having a desired thickness is obtained.

(Mode of cooling after homogenization heat treatment)
Here, after the homogenization heat treatment, the mode when cooling to a temperature range of 350 to 450 ° C. where the hot rolling is started may be directly cooled to this temperature range and the hot rolling may be started within this temperature range. (Hereinafter also referred to as two-stage soaking). Moreover, it cools to the temperature range of 350 degrees C or less, Then, it may reheat to the temperature range of 350-450 degreeC which starts hot rolling further, and may start hot rolling in this temperature range (henceforth, Also called twice soaking).

  When the hot rolling start temperature exceeds 450 ° C., it causes rough skin during bending. Moreover, if the hot rolling start temperature is less than 350 ° C., the hot rolling itself becomes difficult.

As will be described later, the present invention is characterized in that the cold rolling process is not performed after hot rolling, and thus the structure control of the hot rolled sheet is very important. In particular, the present inventors have found that recrystallized grains generated during hot rolling tend to be coarse and this structure is maintained even after solution heat treatment, which causes rough skin during bending. By setting the hot rolling start temperature to 450 ° C. or less, recrystallization during hot rolling can be suppressed, and the crystal grain size after the subsequent solution heat treatment can be set to a predetermined value or less. In addition, during the cooling to the hot rolling start temperature after the homogenization heat treatment, an Mg ₂ Si compound is formed in the ingot, and this Mg ₂ Si compound is a nucleation site of recrystallized grains during the solution heat treatment Therefore, the crystal grain size can be reduced.

Although the cooling rate to the hot rolling start temperature range after the homogenization heat treatment is not particularly specified, it is preferably in the range of 20 to 200 ° C./h. When the cooling rate is 20 ° C./h or less, the Mg ₂ Si compound becomes coarse. Therefore, if it is attempted to re-solidify the Mg ₂ Si compound in order to obtain a desired strength, a solution heat treatment is required for a long time, and productivity is increased. descend.
On the other hand, if the cooling rate is too high at 200 ° C./h, the temperature distribution in the ingot becomes non-uniform, and there is a possibility that a new problem in which an abnormality such as deformation or warping due to heat shrinkage occurs.

On the other hand, if the cooling rate is too high, the average size of the Mg ₂ Si compound formed while cooling to the hot rolling start temperature range after the homogenization heat treatment becomes too small, and it is necessary as a nucleation site for recrystallized grains. In addition, there is a possibility that an appropriate number of relatively coarse Mg ₂ Si compounds having a diameter of 2 μm or more cannot be distributed.

(Cooling means after homogenization heat treatment)
As a method for cooling the ingot, there are, for example, forced fan air cooling in the soaking furnace or outside the furnace, contact cooling, and cooling by mist or spray.

  The hot rolling end temperature is not particularly defined. However, by lowering the hot rolling end temperature to 300 ° C. or less in particular, the accumulated strain during hot rolling can be increased and the recrystallization driving force in the subsequent solution heat treatment can be increased. The recrystallized grain size can be further refined while increasing the Cube orientation distribution density.

(Solution heat treatment process)
In the solution heat treatment step S4, the hot rolled plate manufactured in the hot rolling step S3 is solution heat treated. Here, the heat treatment temperature (ingot temperature) in the solution heat treatment step S4 is 500 to 570 ° C. When the heat treatment temperature is less than 500 ° C., undissolved Si or Mg remains, so that an appropriate precipitate distribution cannot be obtained after solution heat treatment and artificial aging treatment, and desired proof stress and creep resistance can be obtained. I can't. On the other hand, when it exceeds 570 ° C., local melting (burning) occurs on the plate surface. More preferably, it is 520-550 degreeC.
The holding time at the heat treatment temperature in the solution heat treatment step S4 is within 100 seconds (may be 0 seconds). This is because when the time exceeds 100 seconds, the effect is saturated and the productivity is lowered.
In addition, by not performing cold rolling after the hot rolling step S3 and setting the heat treatment temperature in the solution heat treatment step S4 within the above range, the Cube orientation is appropriately developed, and the Cube orientation distribution density on the plate surface is increased. Becomes a predetermined value or more.

In the solution heat treatment step S4, the rate of temperature increase from 200 ° C. to the heat treatment temperature is preferably 5 ° C./s or more, and the rate of temperature decrease from the heat treatment temperature to 200 ° C. is 10 ° C./s or more. preferable.
By setting the temperature rising rate to be equal to or higher than the above rate, it is possible to ensure that the Cube orientation is appropriately developed. Moreover, desired intensity | strength can be acquired reliably by making temperature-fall rate more than the said speed | rate.

(Artificial aging treatment process)
In the artificial aging treatment step S5, the artificial aging treatment is performed at a predetermined temperature and a predetermined time on the hot-rolled sheet subjected to the solution heat treatment in the solution heat treatment step S4.
Although it does not specifically limit about the heat processing temperature in artificial aging treatment process S5, It is preferable that it is 150-250 degreeC. When the temperature is lower than 150 ° C., desired proof stress and creep resistance cannot be obtained, and when the temperature exceeds 250 ° C., precipitates are coarsened and the proof strength and creep resistance are lowered. Further, the heat treatment time is not particularly limited, but is preferably 1 to 30 hours. If the time is less than 1 hour, particularly when mass production is assumed, a non-uniform temperature distribution occurs in the coil or the sheet, and the material characteristics tend to become unstable. In consideration of productivity, the upper limit is 30 hours.

The manufacturing method of the aluminum alloy plate for connecting parts according to the present invention is as described above. However, in carrying out the present invention, other processes may be performed between or before and after the respective steps within a range that does not adversely affect the respective steps. These steps may be included. For example, after the artificial aging treatment step S5, a cutting step for cutting into a predetermined size or a processing step for processing into a predetermined shape (bending, punching, etc.) as shown in FIG. 1 may be included.
In addition, as for conditions that are not clearly shown in the respective steps, it is sufficient to use conventionally known conditions, and it is needless to say that the conditions can be appropriately changed as long as the effects obtained by the processing in the respective steps are exhibited.

Next, the aluminum alloy plate for connecting parts and the manufacturing method thereof according to the present invention will be specifically described by comparing an example satisfying the requirements of the present invention with a comparative example not satisfying the requirements of the present invention.
[Production of test materials]
Aluminum alloys (alloys 1 to 17) having the compositions shown in Table 1 were melted, ingots were produced by semi-continuous casting, and surface treatment was performed. The ingot was subjected to homogenization heat treatment under the conditions shown in Table 2, and then subjected to hot rolling at a rolling rate of 99% continuously without cooling (hot rolling end temperature is Table 2). A rolled sheet was used. Thereafter, solution rolling heat treatment was performed under the conditions shown in Table 2 without performing cold rolling (the test materials 24 and 25 were subjected to cold rolling). Then, after the solution heat treatment, a test material (thickness 2 mm) was prepared by performing an artificial aging treatment (not applied to the test material 24) held at 200 ° C. for 2 hours.
In addition, about the test materials 1-4, hot rolling was performed by two-step soaking, and about the test materials 5-18, 20, and 23, hot rolling was performed twice by soaking.

[Evaluation]
(Tensile test)
A test piece of JIS No. 5 was cut out from the specimen so that the tensile direction was parallel to the rolling direction. Using this test piece, a tensile test was performed in accordance with JIS Z 2241, and tensile strength, yield strength (0.2% yield strength), and elongation were measured.
The crosshead speed was 5 mm / min, and the test was performed at a constant speed until the test piece broke.

(Cube orientation distribution density)
Cube orientation distribution density was calculated | required by measuring the surface of the produced test material using the X-ray-diffraction apparatus [model "Rigaku RAD-rX" (Ru-200B)] by Rigaku Corporation. ODF analysis was performed using an incomplete pole figure using the X-ray diffractometer. In detail, the incomplete pole figure of {100} plane and {111} plane is created by schluz reflection method, ODF analysis is performed by applying Bunge's iterative series expansion method (positivity method), and Cube orientation The distribution density was determined.

(conductivity)
The conductivity was measured by an eddy current conductivity measuring device [model “Sigma Test D2.068”] manufactured by Nippon Ferster Co., Ltd. In addition, the measurement of the conductivity was performed at any five locations on the surface of the test material with a space of 100 mm or more between each other. The electrical conductivity in the present invention is obtained by averaging the measured electrical conductivities.

(Measurement of average crystal grain size)
The surface of the test material was polished, the polished surface was etched with an electrolytic solution, and photographed with an optical microscope at a magnification of 100. With this micrograph, the crystal grain size in the rolling direction was measured by the section method. The crystal grain size was measured at five locations, and the average value is shown in Table 2.

(Bending workability)
A test piece of JIS No. 3 (JIS Z 2204) was cut out from the specimen so that the longitudinal direction of the test piece coincided with the rolling direction. The test piece was subjected to a bending test by the V-block method according to JIS Z 2248 (see FIG. 3), and the bending workability was evaluated. The bending test was performed under the conditions of θ (bending angle): 90 °, r (inner bending radius): 0 mm, and t (test material plate thickness): 2 mm.
Observe the occurrence of cracks in the bent part (curved part, width: 30 mm) after the bending test, and among the five test pieces, all of the test pieces that did not generate rough skin or cracks were very good (○ ), One with at least one acceptable level of rough skin is good (△), marked with rough skin (×), or cracked with a crack length of 2 mm or more (×× ) Was evaluated as bad.

(Residual stress ratio)
The residual stress ratio was measured by the cantilever method described in the Japan Electronic Materials Manufacturers Association Standard EMAS-3003.
Specifically, a strip-shaped test piece (sample thickness: 2 mm) having a width of 10 mm and a length of 250 mm was cut out so that the longitudinal direction of the test piece was perpendicular to the rolling direction. One end of the test piece was fixed to a rigid test table. The test piece was given a span of 150 mm and an initial deformation amount (δ0 = 10 mm), held in that state at 120 ° C. for 100 hours, and then the stress was removed to measure the deformation amount (ε) of the test piece. The residual stress ratio was determined by “residual stress ratio = (δ0−ε) ÷ δ0 × 100”. When the residual stress ratio value is 75% or more, it has the ability to withstand the phenomenon (creep) that is deformed by continuous stress at high temperature, that is, it has the creep resistance required for connecting parts. evaluated.

  Detailed aluminum alloy components, production conditions for the test materials, and material properties (test results) are shown in Table 1 or Table 2. In Tables 1 and 2, numerical values that do not satisfy the configuration of the present invention are underlined.

[Examination of results]
About the test materials 1-9, since all the requirements prescribed | regulated by this invention are satisfy | filled, even when it is set as very severe bending process conditions with internal bending R = 0mm, it is very favorable ((circle)). Or, it was evaluated as good (Δ) and evaluated as having creep resistance required for the connecting parts.

  The specimen 10 (alloy 9) had a Si content that was less than the lower limit of the numerical range defined in the present invention, and the Mg content exceeded the upper limit of the numerical range defined in the present invention. The proof stress did not exceed a predetermined value, and as a result, the evaluation was that the bending workability and creep resistance were not excellent.

  In the test material 11 (alloy 10), the Si content exceeded the upper limit of the numerical range defined in the present invention, and the Mg content was less than the lower limit of the numerical range defined in the present invention. Was not higher than the predetermined value, and the bending workability and creep resistance were not excellent.

  Since the test materials 12 to 18 (alloys 11 to 17) were Fe, Zn, Cu, Mn, Cr, Zr, and Ti, any one of which was equal to or greater than the numerical value defined in the present invention, the bending workability was high. The evaluation was bad.

  Since the heat treatment temperature of the homogenization heat treatment exceeded the upper limit value of the numerical value range defined in the present invention, the test material 19 was burned and could not be manufactured and tested thereafter.

  Since the heat treatment temperature of the solution heat treatment exceeded the upper limit of the numerical range defined in the present invention, burning occurred in the test material 20, and the subsequent manufacturing and testing could not be performed.

  In the test materials 21 and 22, since the starting temperature of hot rolling exceeded the upper limit of the numerical range defined in the present invention, the average crystal grain size in the rolling direction exceeded a predetermined value, and as a result, bending The processability was poor. On the other hand, since the start temperature of the hot rolling was less than the lower limit value of the numerical range specified in the present invention, the hot rolling became difficult and the subsequent production and test could not be performed.

  Since the specimens 24 and 25 were cold-rolled, the Cube orientation distribution density was less than a predetermined value, resulting in poor bending workability. Furthermore, since the sample material 24 was subjected to batch furnace annealing (240 ° C. × 5 hours (temperature increase rate: 50 ° C./hour, temperature decrease rate: 50 ° C./hour)) as a solution heat treatment, the creep resistance was improved. The evaluation was not good.

  The sample material 24 is assumed to be an aluminum alloy plate described in Patent Document 2, and the sample material 25 is assumed to be an aluminum alloy plate described in Patent Document 1.

1 Connecting parts (bus bar)
1a connecting part

The present invention electrically connects between electric devices (batteries, inverters, motors, etc.) mounted on various electric transportation devices using electricity as a power source such as an electric vehicle or between components inside the electric device. The present invention relates to an aluminum alloy plate for bus bars used for connecting parts to be connected and a method for manufacturing the same.

Then, this invention makes it a subject to provide the aluminum alloy plate for bus bars which is excellent also in creep resistance and bending workability, and its manufacturing method, maintaining electroconductivity.

In order to solve the above-mentioned problems, the inventors of the present invention show that the Cube orientation distribution density, the component composition, and the like on the surface of the aluminum alloy plate for bus bars have a great influence on creep resistance and bending workability. Heading, created the present invention.

That is, the aluminum alloy plate for bus bars according to the present invention contains Si: 0.3 to 1.5% by mass, Mg: 0.3 to 1.0% by mass, with the balance being Al and inevitable impurities. It is composed of an alloy, the conductivity is 45.0% IACS or more, the Cube orientation distribution density of the plate surface by the crystal orientation distribution function analysis is 45 or more with respect to the random orientation, and the average crystal grain size in the rolling direction on the plate surface is It is 150 μm or less.

According to this aluminum alloy plate for bus bars , the Cube orientation distribution density on the surface of the plate is specified more than a predetermined value, so that creep resistance can be improved and bending workability can be improved. In other words, according to this busbar aluminum alloy plate, it is possible to achieve both workability and bending creep resistance required of the bus bar. Furthermore, the bending surface quality can be improved by reducing the crystal grain size.
Moreover, according to this aluminum alloy plate for bus bars , since the contents of Si and Mg are specified within a predetermined range, the effect of improving creep resistance can be ensured.
Furthermore, according to this aluminum alloy plate for bus bars , since the electrical conductivity is specified to be 45.0% IACS or more, the electrical conductivity required for the bus bar can be ensured.

Moreover, it is preferable that the aluminum alloy plate for bus bars which concerns on this invention is less than Fe: 0.5 mass% and Zn: less than 0.5 mass% among the inevitable impurities.

According to this aluminum alloy plate for bus bars , the content of Fe and Zn among inevitable impurities is specified to be less than a predetermined value, so that the effect of improving the bending workability can be ensured. .

Further, in the aluminum alloy plate for bus bars according to the present invention, the aluminum alloy is Cu: less than 1.0 mass%, Mn: less than 1.0 mass%, Cr: less than 0.5 mass%, Zr: 0.3 It is preferable to further contain one or more selected from less than mass% and Ti: less than 0.1 mass%.

According to this aluminum alloy plate for bus bars , since it further contains one or more selected from Cu, Mn, Cr, Zr, Ti less than a predetermined value, while ensuring the effect of improving the bending workability, The effect of improving the creep property can be further ensured.

The method for producing an aluminum alloy plate for a bus bar according to the present invention comprises a homogeneous heat treatment step of subjecting an ingot made of the aluminum alloy to a homogenization heat treatment at 500 to 570 ° C. for 1 to 24 hours, and the homogenization heat treatment. A hot rolling step of producing a hot rolled plate by rolling a plurality of passes with a rolling start temperature of 350 to 450 ° C. to the ingot, and without subjecting the hot rolled plate to cold rolling, It includes a solution heat treatment step for performing a solution heat treatment for holding at 500 to 570 ° C. for 100 seconds or less, and an artificial aging treatment step for performing an artificial aging treatment on the hot-rolled sheet subjected to the solution heat treatment. To do.

According to this method for producing a bus bar aluminum alloy sheet, the component composition of the aluminum alloy to be used is specified, the conditions for the homogenization heat treatment, hot rolling and solution heat treatment are specified, and cold rolling is not performed. The electric conductivity, the Cube orientation distribution density and the proof stress of the aluminum alloy plate for a bus bar manufactured by the manufacturing method can be set to a predetermined value or more and the crystal grain size can be set to a predetermined value or less.

According to the aluminum alloy plate for bus bars according to the present invention, the conductivity and the Cube orientation distribution density on the surface of the plate are specified to be not less than a predetermined value, and the contents of Si and Mg are specified to be within a predetermined range. It is excellent in creep resistance and bending workability while maintaining the properties, and can be suitably used as a bus bar .

Moreover, according to the manufacturing method of the aluminum alloy plate for bus bars according to the present invention, the composition of the aluminum alloy to be used is specified, the conditions for the homogenization heat treatment and the solution heat treatment are specified, and cold rolling is not performed. It is possible to produce an aluminum alloy plate for a bus bar that is excellent in creep resistance and bending workability while maintaining conductivity.

It is a perspective view of the connection component (bus bar) concerning the embodiment of the present invention. It is a flowchart of the manufacturing method of the aluminum alloy plate for bus bars which concerns on this invention. It is a schematic diagram explaining the method of the bending test in the Example of this invention.

Hereinafter, embodiments for carrying out an aluminum alloy plate for a bus bar and a method for manufacturing the same according to the present invention will be described in detail (where appropriate, “aluminum alloy plate for bus bar” will be described as “aluminum alloy plate for connecting parts”). .

Claims (4)

Si: 0.3-1.5% by mass, Mg: 0.3-1.0% by mass, the balance is composed of an aluminum alloy consisting of Al and inevitable impurities,
Connection having a conductivity of 45.0% IACS or more, a Cube orientation distribution density on the plate surface by a crystal orientation distribution function analysis of 20 or more, and an average crystal grain size in the rolling direction on the plate surface of 150 μm or less. Aluminum alloy sheet for parts.   2. The aluminum alloy plate for connection parts according to claim 1, wherein among the inevitable impurities, Fe: less than 0.5 mass% and Zn: less than 0.5 mass%.   The aluminum alloy is Cu: less than 1.0 mass%, Mn: less than 1.0 mass%, Cr: less than 0.5 mass%, Zr: less than 0.3 mass%, Ti: less than 0.1 mass%, The aluminum alloy plate for connecting parts according to claim 1 or 2, further comprising at least one selected from the group consisting of: A homogenization heat treatment step of subjecting the ingot made of the aluminum alloy according to any one of claims 1 to 3 to a homogenization heat treatment at 500 to 570 ° C for 1 to 24 hours,
A hot rolling step of producing a hot-rolled sheet by performing rolling consisting of a plurality of passes with a rolling start temperature of 350 to 450 ° C. on the ingot subjected to the homogenization heat treatment;
Without subjecting the hot-rolled sheet to cold rolling, a solution heat treatment step of performing a solution heat treatment for holding at 500 to 570 ° C. for 100 seconds or less;
An artificial aging treatment step of performing an artificial aging treatment on the hot-rolled sheet subjected to the solution heat treatment;
The manufacturing method of the aluminum alloy plate for connection components characterized by including this.

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