hitachi alloy cable

7/29/2019 Hitachi Alloy Cable

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HITACHI CABLE REVIEW No.25 (AUGUST 2006)18

50

55

60

65

0 0.1 0.2 0.3 0.4 0.5

Ratio of an addition element (mass%)

Electricalconductivity(%IACS)

Cr Mn

Mo

Ti

Li

Zr

Mg

Si

Cu

Ag

Fe

Zn, B

Ni

Sn, Cd

Sb

ABSTRACT: In recent years, lightweight aluminum alloy conductor with high elec-

trical conductivity characteristics is expected. Al-Fe-Zr alloy wire was developed in-

dustrially, although without having the tensile strength and elongation and spoiling

electrical conductivity characteristics.

The developed Aluminum alloy is expected to be applied in various fields such as the

automotive and electric wire for equipment.

Development of Aluminum Alloy Conductor with High ElectricalConductivity and Controlled Tensile Strength and Elongation

Toshiyuki Horikoshi*

Hiromitsu Kuroda*

Michiaki Shimizu**

Seigi Aoyama*

[1] INTRODUCTION

In recent years the automobile and electronics industries

have developed remarkably, and the demand for electric con-

ductive materials used for these applications is increasing com-

pared to the past. Conventionally, aluminum alloy has been ap-

plied mainly to the overhead conductor field taking advantage

of density of 1/3 and high conductivity of 2/3 in electrical con-

ductivity compared with copper. From the viewpoint of ef-

fective use of energy, the lightweight aluminum alloy conductor

is very effective, and possible advantages can also be expected

in the automotive and electronics industry. In order to use alu-

minum alloy electrical conductive material for industrial appli-

cations, we think that it is indispensable to develop an alloy that

responds also to recent social structural changes, such as envi-

ronmental issues and material requirements for recycling. The

present study introduces our recently developed aluminum al-

loy conductor with improved balance between tensile strength

and elongation properties that were demerits of the conventionalAluminum alloy while maintaining, at the same time, high con-

ductivity properties.

[2] DEVELOPMENT CONCEPT

2.1 The target properties of an aluminum alloy wire

In annealed pure Aluminum, the electrical conductivity is

about 64%IACS (International Annealed Copper Standard), ten-

sile strength reaches 100 MPa and elongation reaches about

20%.These properties conform to industrial use by annealing.

From an industrial point of view, for this type of aluminum wire,

electrical properties are not the only requirements, but also han-

dling and good balance of tensile strength and elongation are

important factors. In the present development, we set higher tar-

gets, with tensile strength higher than 30% and above 130MPa

compared with pare aluminum and elongation above 5% from

handling. We achieved these mechanical properties, reducing

the electrical conductivity decline as much as possible, and we

set the target for electrical conductivity above 58%IACS.

2.2 Examination of metal additions

Figure 1 shows changes in electrical conductivity after add-

ing various elements to pure aluminum.

Ni, Zn, Fe, Ag, Cu, Si, Mg, Zr, etc. can be considered pos-

sible additives in small quantities to reduce the decline in elec-

trical conductivity to a minimum.

Table 1 shows the influence on tensile strength after adding

various elements to pure aluminum. Although results show im-

provements on the strength of Cu and Fe, aluminum is used in

many cases with steel material, and the need for recycling

should be taken into consideration. Under these considerations

we excluded Cu as a possible additive, since it is known that

this has a negative influence if contained in steel even in very

small quantities. On the other hand, Fe is completely satisfac-

tory on this point. Moreover, Fe is reported as a material which

performs process softening of the aluminum and as a material

used to improve elongation. Moreover, since it is added in small

quantities, Fe can form a solid solution with aluminum, and im-

provement in tensile strength may be expected with the Properzi

process and the precipitation processing by heat treatment. Un-der these considerations we decided to utilize Fe as an additive.

Furthermore, thermal resistance improvement was also consid-

* Resarch & Develpment Group, Hitachi Cable, Ltd.

** Electronic & Automotive Products Group

Fig. 1 -Influence of the addition element exerted on electrical conduc-

tivity of aluminum2)

Selection of an addition element and quantity is considered so that elec-

trical conductivity may be set to about 60% IACS.


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HITACHI CABLE REVIEW No.25 (AUGUST 2006) 19

TensileStorength(MPa)

Elongation(%)

: Tensile Strength

: Elongation

0

50

100

150

200

250

300

0

5

10

15

20

25

30

54

56

58

60

62

64

66

RT 100 150 200 250 300 350ElectricalConductivity(%IACS

)

Annealing temperature ( ,1hr)

(a)

(b)

: Al: Al-0.3%Fe: Al-0.6%Fe

Tensile strength

Elongation

Fe concentration (mass%)

TensileStrength(MPa)

80

90

100

110

120

130

140

0 0.2 0.4 0.6 0.820

25

30

35

Elongation(%)

(Annealing temperature : 320 )

Elementy /C

(MPa/mass%)

f/C

(MPa/mass%)

Ag

Be

Cd

Ce

Cu

Fe

Ga

Ge

Hf

Mg

Mn

Si

V

Zn

19.6

46.6

98

7.35

19.6

10.8

5.0

14.7

19.6

66.6 or 58.8

90.2

56.8

125

12.7

15.7

37.2

24.5 or 15.7

18.6

19.6

45.1

9.8 or 2.9

ered and Zr was considered as an element to improve thermal re-

sistance. As a result, tensile strength and heat-resistance were im-

proved by adding Zr in amounts of 0.28mass% with aluminum. It

was decided to utilize Fe and Zr as additive to be included in this

study.

[3] EXAMINATION MATERIAL AND METHOD

At first, we produced aluminum alloy wire rods (of 9.5-mm

diameter) including 0.3 - 0.6mass% of Fe and 0.02 - 0.05mass%

of Zr, additions within the limits to allow Zr to form a solid

solution with aluminum(99.7% of purity) using the Properzi

process. Next, we carried out the cold-drawing process and per-

formed heat treatment, furthermore, through the cold-drawing

process we produced a wire of 0.25-mm diameter. This was con-

sidered as material for further experiment. Moreover, aluminum

(99.7% purity) produced with a similar process was used as

comparison material for the experiment. Next, we estimated

their softening characteristics.

[4] EXPERIMENT RESULT OF ALUMINUM-Fe-Zr SYS-TEM ALLOY WIRE, AND CONSIDERATIONS

4.1 Influence of the iron addition on the properties of an alu-

minum alloy wire

Figure 2 (a) shows the influence of heat treatment tempera-

ture on tensile strength and elongation of an Al-Fe alloy wire

(0.25-mm diameter). Figure 2 (b) shows the influence of heat

treatment temperature on electrical conductivity. It turns out that

the specimen added Fe compared with pure aluminum shows

high tensile strength in a wide range of annealing temperatures.

Moreover, at an annealing temperature of above 250C, the elec-

trical conductivity of any specimen is carried out at about2%IACS recovery compared with the no annealing specimen.

The reason is thought to be that processed strain was removed.

Table 1 Contribution of each element to solid solution hard-ening of aluminum3)

(sy / C, sf/ C : 0.2% proof stress and the amount of increasesof modification resistance by addition of unit mass % )It turns out that the effect of the improvement of 0.2% proofstress and modification resistance in Fe is high especiallyas an element.

Fig. 2 -Influence of heat treatment temperature on the tensile strength

and electrical conductivity of Al-Fe alloy wire (0.25-mm diameter)(a: Tensile strength, b: Electrical conductivity)

Fig. 3 -Influence of Fe concentration on tensile strength and elongation

after annealing.

When the concentration of Fe increases, tensile strength and elongation

also increase.

Figure 3 shows the tensile strength and elongation of pure alu-

minum and Al-Fe alloy wire annealed at 320C. As for an Al-Fe

alloy wire, this shows as expected that tensile strength and elon-

gation after re-crystallization are large compared with the pure

aluminum wire.

4.2 Influence of Zr addition on the properties of aluminum al-

loy wire

In section 4.1, Fe addition showed an improvement of ten-

sile strength and elongation compared with pure aluminum.

There is little influence on electrical conductivity at both

0.3mass% and 0.6mass% of Fe. For this reason, improvement

in tensile strength and the drawing process were thought as im-portant and the amount of Fe added was changed to 0.6mass%.

Based on these, Zr was added within the limits of Zr forming a


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HITACHI CABLE REVIEW No.25 (AUGUST 2006)20

TensileStorength(MPa)

Elongation(%)

0

50

100

150

200

250

300

0

5

10

15

20

25

30

: Al: Al-0.6%Fe: Al-0.6%Fe-0.02%Zr: Al-0.6%Fe-0.05%Zr

: Tensile Strength

: Elongation

54

56

58

60

62

64

66

RT 100 150 200 250 300 350ElectricalConductivity(%

IACS)

Annealing temperature ( ,1hr )

(a)

(b)

Alloy composition

Tensile

Strength

(MPa)

Elongation

(%)

Electrical

Conductivity

(%IACS)

Developed

material

Al-0.6mass%Fe-

0.02mass%Zr

Annealed

material 146 8 60.4

Annealed

material 120 8 63.0

Comparison

material Pure AluminumConventional

material 104 22 63.8

0

5

10

15

20

25

30

100 120 140 160 180 200

Tensile strength (MPa)

Elongation(%)

: Al: Al-0.6%Fe

: Al-0.6%Fe-0.02%Zr

: Al-0.6%Fe-0.05%Zr

Target property

solid solution with Al-0.6mass%Fe, and we estimated the vari-

ous properties.

Figure 4 (a) shows the influence of the annealing tempera-

ture on the tensile strength and elongation of an Al-Fe-Zr alloy

wire (0.25-mm diameter). Figure 4 (b) shows the influence of

the annealing temperature on electrical conductivity. The addi-

tion of Zr showed that thermal resistance was improved. How-

ever, the consequence of adding Zr is the remarkable decline inelectrical conductivity compared with improvement in strength,

when 0.05mass%Zr is added, it turns out that electrical conduc-

tivity falls below 60%IACS. As mentioned above, in consider-

ation of the decline in electrical conductivity and drawing

processabi li ty, the amount of addition of Zr was set to

0.02mass%. From section 4.1 and 4.2, Al-0.6mass%Fe-

0.02mass%Zr was selected as the Al-Fe-Zr alloy sample.

[5] COMPREHENSIVE CHARACTERISTIC EVALUATIONOF AN Al-Fe-Zr SYSTEM ALLOY WIRE

If considering use as a wire for electric equipment, then it is

required to combine tensile strength and elongation triggered

by the advantage of handling. For this reason, it is required that

tensile strength and elongation be adjusted. As in section 4, it

turns out that improvement in tensile strength and elongation is

expected by softening examination at the time. Then, examina-

tion obtains the balance tensile strength and elongation by spe-

cial heat treatment. Figure 5 shows the tensile strength and elon-

gation of Al-Fe alloy and Al-Fe-Zr alloy wire under various con-ditions of heat treatment. It turns out that the tensile strength

and elongation of Al-Fe-Zr alloy wire are excellent compared

with Al-Fe alloy wire. For example, when the amount of added

Zr is 0, 0.02, and 0.05mass%, the elongation of 8, 12, and 15%

are respectively obtained at a fixed tensile strength of 140 MPa.

It is reported that crystal grain turn minutely by 0.2mass% of Zr

added, and it is thought that the improvement in tensile strength

and elongation is based on the crystal grain effect. From the

above, it turns out that Al-Fe-Zr alloy has high tensile strength

above 30% compared with pure aluminum and elongation byacquiring above 5% and furthermore their properties can be con-

trolled. Table 2 shows the properties of the specimen. The im-

provement in above 30% of tensile strength above 5% of elon-

gation, and above 58%IACS of electrical conductivity which

Al-0.6mass%Fe-0.02mass%Zr made the target to the pure alu-

minum wire of the conventional system was acquired. The ten-

sile strength and elongation of this specimen alloy can be ad-

justed to a necessary value.

Fig. 4 -Influence of heat treatment temperature on the tensile strength

and electrical conductivity of Al-Fe-Zr alloy wire (0.25-mm diameter)

(a: Tensile strength, b: Electrical conductivity)

Fig. 5 -Comparison of tensile strength of Al -Fe-Zr alloy wires (0.25mm-

diameter) with pure aluminum. Al-Fe-Zr alloy combines tensile strength

and elongation.

Table 2 Example of room temperature properties of Al-Fe-

Zr alloy wire in an experiment (0.25mm-diameter)In annealed Al-0.6mass%Fe-0.02mass%Zr, tensile strengthincreases 22%, equivalent elongation and above 60%IACSelectrical conductivity as compared with annealed pure alu-minum.


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HITACHI CABLE REVIEW No.25 (AUGUST 2006) 21

Twist wire

20 mm

0.5 mm

Insulation

Twisted wires

Development materialCable

composition

Existence of

covering

Breakingstrength

(N)

Elongation

(%)

Electricalconductivity

(%IACS)

With nocoveringThose withcovering

42.2 16.4Al-0.6mass%Fe-0.02mass%Zr 7 / 0.25

59.7 20.360.7

[6] CABLE UTILIZING DEVELOPED ALUMINUM ALLOYWIRE

The cable (0.3SQ, 7/0.25) was produced as a cable used for the

car and the rebot for which lightering was needed. Figure 6

shows the cable utilizing the developed Al-0.6mass%Fe-

0.02mass%Zr as an experiment. Figure 7 shows a cross-section

photograph. In the trial production of this cable, the processes

of drawing and twisting covering of the wire and insulator etc.

are no problem. Table 3 shows the properties of the cable. We

expect the use of this aluminum alloy to expand in the future.

that responded to the new concept and, at the same time, can

control tensile strength and elongation. Moreover, the possibil-

ity of being supplied with similar conductivity as pure alumi-

num so that it can respond to customer's various needs and re-

spect environmental and recycling requirements. One of the fea-

tures of this alloy wire is its possibility to be manufactured us-

ing the Properzi process of continuity casting rolling method in

consideration of the homogeneity of the composition. With thisdeveloped aluminum alloy wire, while offering the function ac-

cording to demand of a Customer, the it is hoped that its use can

be extended to various fields.

[8] ACKNOWLEDGEMENT

We wish to express our deep gratitude to Ibaraki University

and to Professor Goroh Ito for their precious counsel and coop-

eration in the development of this aluminum alloy wire.

REFERENCES

(1) Y.Miyake: Keikinzoku, 36(1986), 51-60, 112-121.(2) E.E.Handbook: The Institute of Electrical Engineers of Ja-

pan, (1978), 619.

(3) The organization and character of aluminum: The Japan

Institute of Light Metals, (1991), 160.

(4) K.Shibata. et al: Fyeramu,7(2002),18-22.

(5) H.Takei. et al: Keikinzoku,30(1980),626-633.

(6) T.Fukui: Keikinzoku, 18(1968)320-331

(7) H.Suzuki. et al: Keikinzoku,33(1983),29-37.

(8) W.A.Dean: Aluminum,Ed.by J.E.Hatch,American Soc.Met.,Metals

Park,Ohio,(1984),240.

Toshiyuki Horikoshi

Resarch & Develpment GroupMaterials Technology Research & Development CenterCurrently engagad in research and development of elec-tric materials

Hiromitsu Kuroda

Resarch & Develpment GroupMaterials Technology Research & Development CenterCurrently engagad in research and development of elec-tric materials

Michiaki Shimizu

Electronic & Automotive Products GroupAutomotive Components Production Div.Electric Components Dept.

Seigi Aoyama

Resarch & Develpment GroupMaterials Technology Research & Development CenterPh.D. degree in Material Sciene

The Japan insutitute of MetalsCurrently engaged in research and development of elec-tric materials.

Fig. 6-Twist wire from the cable (0.3SQ, 7/0.25) produced using the

newly developed aluminum alloy.

The cable was insulated after twisting seven Al-Fe-Zr alloy wires

(0.25mm-diameter).

Fig. 7-A cross section of the trial production cable (0.3SQ, 7/0.25)

Table 3 Cable properties using Al-Fe-Zr alloy wire at roomtemperature

In the trial production of this cable, wire drawing and twist-ing wire and insulated covering, etc. have been conductedwithout any problems.

[7] CONCLUSION

In recent years the remarkable progress of the automotive

and electronics industry, the need for lightweight electric con-

duction material has increaseed and the development of alumi-num electric conduction material was considered with this in

mind. This development of an alloy wire focused on a material

hitachi alloy cable

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