BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a method for manufacturing electrically conductive
substances such as power transmission cables, leads or wires used in electronic parts,
coiling wires and the like.
Description of Related Art
[0002] Linear metallic substances for use in power transmission cables, leads in electronic
parts and the like, and in electrically conductive composite wires or cables (for
convenience, referred to as composite wires hereinafter) consisting of a metallic
core cladded with non-ferrous metals such as copper, aluminum and the like have been
manufactured by producing linear metallic materials by any of known methods, for example,
hot or warm extrusion, or hot rolling and reducing the diameter of the materials with
a drawing bench having a die for working to produce linear substances having a desired
diameter. In industry, electrically conductive wires of a given dimension have been
manufactured by means of a continuous drawing equipment having a plurality of benches
bearing dies disposed on line.
[0003] In the production of composite wires, the ratio in cross sectional area of the core
to the cladding layer changes with the drawings of the wires, because the resistance
to deformation of the core is different from that of the cladding. Therefore, the
change of the ratio in cross-sectional area of the core to the cladding due to drawing
is predetermined, thereby the thickness of the cladding layer relative to the core
is determined, based on which the composite substances are made and then drawn to
give composite wires having desired dimensions.
[0004] The working such as the drawing described above has been carried out generally with
lubricants of liquid- and/or powder-types as lubricants for working.
[0005] When the drawing is conducted by means of the continuous drawing bench, the reduction
of the diameter of wires is increased as the wires pass through from a drawing die
to a next one. Therefore, the velocity of transferring a wire must be higher in the
later drawing step through which the wire passes. At the final drawing step, the velocity
may become as high as 250 to 400 m/min.
[0006] There is a stringent requirement for the uniformity of surface properties and conductivity,
particularly of the cladding thickness of the composite wires so as to have a constant
conductivity over the whole length thereof. Concurrently, the surface is required
to be in such a good surface condition as having no "galling" due to seizure between
dies and materials upon the plastic working, nor "discoloration" due to deterioration
of lubricants and the like.
[0007] The surface condition of composite wires is dependent on the ratio in cross-sectional
area of the core to the cladding layer, the configuration of drawing dies, the percentage
reduction, particularly to a great extent on the lubricants. Furthermore, there is
a need for increasing the speed of working to produce composite wires at a higher
productivity, and for the purpose, the quality of lubricants must be improved to a
great extent.
[0008] Although a wide variety of lubricants have been employed in attempting to satisfy
the aforementioned requirements and needs, there is still no lubricant capable of
satisfactorily attaining both the higher speed of working and the better surface condition.
[0009] Generally, a lubricant having a higher viscosity is more effective to prevent metal
materials from contacting with one another and the wires from galling during drawing.
[0010] Liquid lubricants include formulations consisting of a basic oil selected from mineral
oils, synthetic oils such as ester oils and the like, and mixtures thereof, with addition
of any of various additives such as oiliness improving agents, for example, higher
fatty acids and higher alcohols as described by T. SAKURAI in "PETROCHEMICAL ADDITIVES"
(published by Saiwai Shobo, Japan, May 1973) and extreme-pressure lubricants of a
phosphorus, chlorine or sulfur type.
[0011] Powder-type lubricants include metallic soaps such as calcium soap and sodium soap.
The soap powder is forced into a space between a die and a wire under pressure and
then the drawing is effected.
[0012] For drawing wires from steel material alone, there is a lubricant produced by incorporating
metallic soap powder of 100 µm or less into polybutene [see, JP-A-80-135198]. There
are also lubricants for use in metal wire drawing produced by incorporating paraffin
wax, chlorinated paraffine and phosphite ester or phosphate ester [see, JP-A-87-153396]
and those produced by dispersing fats and fatty oils or wax in water with a high molecular
dispersant, surfactant and the like [see, JP-A-80-147593]. Since the viscosity resistance
of these lubricants is high, however, the temperature rises during drawing and as
a result the viscosity of the lubricants is reduced to cause galling. In addition,
owing to the increase of temperature, the mechanical strength of the wire materials
themselves is reduced so that with the prior lubricants the drawing velocity is limited
at maximum to about 100 to 150 m/min.
[0013] Moreover, the high viscosity lubricants as described above suffer from being reluctant
and unmanageable in replenishing and the like, and when they are splashed around adhering
to the surfaces of machinery and floor, their high viscosity may cause sticking of
work clothings and shoes of operators on the splashed spots. In such case, there may
be a risk that the operators fall down or be caught in the drawing machine to raise
the problem of safety practice.
[0014] On the other hand, lubricants suitable for drawing steel wires are unsuitable for
drawing non-ferrous metals, particularly soft metals such as copper or aluminum and
apt to cause galling and surface cracking. The surface cracking occurs when the non-ferrous
metal materials has a higher shearing strength than the frictional force between the
materials and the die.
[0015] Moreover, since these lubricants have a higher content of metal soap, they have a
disadvantage in that the surfaces of workpieces are discolored to diminish the commercial
value thereof.
[0016] As lubricants for use in plastic working of aluminum, one may employ polybutene having
a viscosity of 0.171 m²/s (171,000 cSt) (40°C) or more. As described above, however,
the lubricants have a less tendency to cause seizing of materials and dies making
it possible to draw wires even at a velocity of 200 m/min, though the higher viscosity
lubricants raise difficulties in workability and safety as pointed out above.
[0017] As above, there have been many problems in wire drawing with conventional lubricants.
[0018] "WIRE AND WIRE PRODUCTS", vol. 27, No 11, p. 1180-1184, discloses a wire-drawing
lubricant composition containing a mineral oil having a viscosity of up to 3000 Saybolt
(13900 cSt, i.e. 0.0139 m²/s) at 38°C and 10-30% of a fatty material such as lard
oil or tallow oil. A disadvantage thereof is a great temperature-dependency of the
viscosity, making a drawing operation hard at elevated temperatures.
[0019] EP-A-0242040 discloses a metal pipe- or metal sheet-drawing, metal rolling or metal
forging lubricant composition comprising at least one of 2-ethyl polyacrylate-hexyl
ester and polymethylacrylic acid lauryl ester, and an oiliness improver such as lard,
oleic acid, phosphate, hindered ester, isostearic acid, C₁₈ saturated higher alcohol
or mixtures thereof. It also refers to a base oil such as polybutene, α-olefin, α-olefin
oligomer, polyethylene glycol etc., and to an oiliness improver such as fats and oils,
saturated or unsaturated fatty acid with ten or more carbon atoms, fatty acid ester,
alcohol etc. It is silent, however, as to the viscosity of the base oil and as to
wire drawing non-ferrous metal material.
[0020] FR-A-1426791 discloses a lubricant composition for rolling metals, particularly steel,
comprising a liquid polybutene having a viscosity ranging from 30 to 1100 Saybolt
(5082 cSt) at 99°C and a molecular weight of 300 to 900, 2 to 50% of a fatty material
such as a high molecular weight fatty acid from animals, plants or sea products and
glyceride, an oxidized oil such as oxidized spermaceti or sulfurized fatty acids,
and 0 to 5% of an emulsifier. It is silent, however, as to wire drawing non-ferrous
metal material.
SUMMARY OF THE INVENTION
[0021] It is an object of the present invention to provide a method for manufacturing electrically
conductive substances by wire drawing substances having a non-ferrous metal surface
using a lubricant composition which allows to prevent the surfaces of wires manufactured
from seizing during drawing with wire materials resulting in the production of wires
having good surface properties.
[0022] It is another object of the present invention to provide a method for manufacturing
electrically conductive linear substances such as power transmission cables, leads
used in electronic parts, coiling wires and the like by effecting the plastic drawing
of metal materials at a high speed with the aforementioned lubricant composition.
[0023] It is another object of the present invention to provide a method for manufacturing
electrically conductive linear substances which do not cause any problem in improvement
of working environment and safety by using the aforementioned lubricant composition.
[0024] Said objects are achieved according to the present invention, by a method for manufacturing
electrically conductive substances, characterized by coating the surface of a non-ferrous
metal material with a liquid lubricant composition comprising as base oil a liquid
high molecular compound, having a viscosity of 0.0003 to 0.05 m²/s (300 to 50,000
cSt) at 40°C, and an additive of an oiliness agent, added 2 to 25% by weight to said
base oil, selected from the group consisting of animal and vegetable fats and oils
and aliphatic dicarboxylic acids, and wire drawing on said non-ferrous metal material
with a die while forming a lubricant film on the surface of the material.
[0025] Advantageous additional features are claimed with the sub-claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026]
FIGURE 1 is a diagrammatical view of a system for manufacturing wires by drawing linear
metal materials in a single stage,
FIGURE 2 is a diagrammatical view of a system for manufacturing wires by drawing linear
metal materials in multiple stages,
FIGURE 3 is a diagrammatical cross-sectional view of a die part of a system for manufacturing
wires by drawing linear metal materials,
FIGURE 4 is a plot of an variation of the temperature of the die as a function of
the viscosity of the lubricant composition according to the present invention when
the wire drawing is effected therewith,
FIGURE 5 is a diagrammatical cross-sectional view of an aluminum material prior to
plastic working,
FIGURE 6 is a diagrammatical cross-sectional view of an aluminum part after plastic
working, and
FIGURE 7 is a diagrammatical view showing three stages for producing a superconductive
composite wires and tapes; (a) is a diagrammatical cross-sectional view of a composite
substance produced by enclosing superconductive material 18 with a cladding pipe 17;
(b) is a diagrammatical cross-sectional view of an elongated composite substance produced
by swaging the substance as shown in (b); and (c) shows diagrammatically both a composite
wire produced by drawing and a composite tape produced by rolling the swaged substance.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0027] The method of the present invention will be described in detail here under with reference
to the drawings.
[0028] Referring to FIGURE 2, continuous linear material 2 is unwound from supply 1, guided
by first roller 8, passes via guide 3 of wire drawing machine No. 1 coated on its
surface with lubricant 4, pulled by storage drum 7 to be drawn to have the first reduced
diameter with drawing die 5 and wound on the storage drum.
[0029] Then the resulting wire is guided by rollers 8′ and 8˝ to wire drawing machine No.
2 where it is drawn to have the second reduced diameter as described above. The thinner
wire may further drawn sequentially by a desired number of wire drawing machines (the
last one is designated as No. n) to have a desired diameter.
[0030] Then the wire is introduced into treating chamber 9, passed through straightening
machine 10 where the strain is removed, thereafter the lubricant adhered on the surface
of the wire is removed by rolling brush 12 with solvent 11 and then the wire is dried
in the blower 13. The dried wire is wound on winding drum 15 of winding machine 14.
[0031] The lubricant comprises a base oil and an additive. As a common prior art base oil,
one may mention mineral oil. However, mineral oil has a viscosity index not higher
than 100 and its viscosity is rapidly reduced with an increase of temperature. For
the reason, adhesion force of mineral oil to the surface of wire materials is lowered
rendering lubrication poor, so that galling and fracturing of the wires are apt to
occur and smooth drawing is unattainable. Moreover, if the temperature of the drawing
die is 120°C or higher, the use of mineral oils as base oil leads to discoloration
of the surface of the wires and is unsuitable for the high velocity drawing.
[0032] It has been found that as base oils, liquid high molecular compounds do not diminish
the excellent lubricating properties of animal and vegetable fats and oils or aliphatic
dicarboxylic acid as additives, have less tendency to lower the viscosity with an
increase of the temperature and have excellent adherability and heat resistance. The
present invention has been made on the basis of this finding.
[0033] Liquid high molecular compounds include, for example, polybutene, polymethacrylate,
polyisobutylene, ethylene-α-olefin copolymers. In addition, polyphenyl ether, fluorinated
ester, polyether, and the like may be employed.
[0034] The liquid high molecular compounds are liquid polymers which can be produced by
any of known methods, and their viscosity can be freely controlled by varying their
molecular weight or selecting and incorporating those having different molecular weights.
[0035] The liquid high molecular compounds to be used as base oils should have a viscosity
of 0.0003 to 0.05 m²/s (300 to 50,000 cSt) at 40°C in view of the conditions of drawing,
workability and manageability.
[0036] Additives (lubricity improving agents) to be incorporated into the base oils include
animal and vegetable oils such as hardened castor oil, lard oil, linseed oil, soybean
oil, hardened tallow, lanolin and the like.
[0037] Aliphatic dicarboxylic acids include those having 5 to 36 carbon atoms such as glutaric
acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic
acid, tridecanoic acid, dimer acid and the like.
[0038] An amount of animal and vegetable fats and oils or aliphatic dicarboxylic acids to
be incorporated into the base oil, liquid high molecular compound is 2 to 25% by weight,
preferably 5 to 20% by weight. It an amount of animal and vegetable fats and oils
or aliphatic dicarboxylic acids to be incorporated is less than 2% by weight, the
effect of improving lubricity is insufficient and galling is apt to occur during drawing.
Although one may use a higher amount than 25% by weight of the additives, any further
improvement of antigalling will not be attained.
[0039] To the lubricants used in drawing according to the present invention, one may add
an oiliness improving agent such as higher fatty acids, higher alcohol and the like,
an extreme-pressure lubricant of phosphorus-, chlorine- or sulfur-type, or metal soap
powder and the like, if necessary. Moreover, to the lubricants as described above
may be added water so as to produce the lubricants of emulsion type. In this case,
any of known emulsifiers may be added.
[0040] The present invention allows composite wires consisting of superconductive core material
cladded with non-ferrous metal material such as copper, aluminum and the like to be
drawn at a higher velocity.
[0041] Although the present invention has been explained primarily with respect to wire
drawing, it can be applied to general plastic working of non-ferrous metal materials
for forming parts therefrom.
[0042] The lubricants used in the present invention exhibit a lower reduction of viscosity
with an increase of the temperature and are thermally stable and excellent in adhesion
to the surface of metal material with formation of a good lubricant film (oil film)
at the frictional interface upon plastic working. Particularly, the film produced
by the reaction of the surface of non-ferrous metal material and the additive in the
lubricant, i.e., animal and vegetable fats and oils or aliphatic dicarboxylic acid
is formed on the surface subjected to plastic working resulting in prevention of galling
and in facility of plastic working because the film has an excellent lubricating property.
[0043] It may be postulated that the film is a metal soap film produced by primarily the
reaction of the surface of the non-ferrous metal material and the additive with frictional
heat generated at the interface between the material and the die; see, T. SAKURAI,
"LUBRICANT OIL ADDITIVES ― STATE AND FUTURE", LUBLICATION,
15, No. 6302-310, (1970).
[0044] The metal soap film is effectively formed locally at a part of the surface of the
material in contact with the die to become a stiff film preventing the "galling" which
occurs owing to direct contact of the metal material with the die. Therefore, smooth
plastic working can be achieved. Such effect can be most remarkably attained in wire
drawing with no galling occurring even in high velocity wire drawing.
[0045] The present invention will be illustrated practically with the following Examples.
Examples 1 to 11
[0046] To polyisobutylene having a viscosity of 0.00065 m²/s (650 cSt) at 40°C to be used
as lubricant base oil, were added 10% by weight of fats and oils or aliphatic dicarboxylic
acid as shown in Table 1 which had been heated and molten to prepare lubricant oils.
With these oils, composite linear substances consisting of steel core cladded with
copper were subjected to wire drawing by means of the drawing machine as shown in
FIGURE 1. FIGURE 3 shows a diagrammatical cross-sectional view of the die.
[0047] Composite linear substance 2 unwound from supply 1 was guided by guide 3, immersed
in and coated with lubricant 4, drawn through drawing die 5 equipped with thermocouple
6 to reduce the diameter of the substance and wound on dram 7 disposed in the drawing
machine.
[0048] Then the resulting wires were allowed to pass through straightening machine 10 where
the strains were removed, and thereafter the lubricants adhered on the surfaces of
the wires were removed by rotating brushes 12 while spraying trichlene solvent onto
the surface. After removing the solvent by air blowing with blower 13, the wires were
wounded on winding dram 15 disposed in winding machine 14.
[0049] The surfaces of the wires were observed with the naked eyes to determine the surface
condition on the basis of appearance of galling and surface cracking. In addition,
the temperature increase of the die [(Temperature during drawing) ― (Initial temperature)]
was determined. The results are indicated in Table 1. The wire drawing was performed
under the following condition:
- substance for wire:
- steel core ― copper cladding composite
(Cu-steel linear substance)
- Shape of die:
- conical shape die having the dimensions of:
reduction angle; 2°
drawing diameter; 2.89 mm
bearing length; 2 mm
- Reduction ratio:
- 20.4% (wire drawing reduction from a
diameter of 3.24 mm to that of 2.89 mm)
- Drawing velocity:
- 110/min
- Die temperature:
- room temperature, 12°C.

Comparative Example 1 to 7
[0050] The lubricant used in each Comparative Example is shown in Table 2. The parenthesized
number indicates the viscosity at 40°C (m²/s).

Example 12
[0051] Using the same lubricants as in Examples 1 to 11, the composite linear substances
consisting of a steel core cladded with aluminum were subjected to wire drawing by
means of the drawing machine as shown in FIGURE 1. The surface conditions (with respect
to galling and surface cracking) after drawing were observed with the naked eyes and
the die temperature increase was determined. The results are shown in Table 3.
[0052] The analysis with the roundness measuring apparatus (available from KOSAKA Laboratory,
Modle EC-4S) indicates that the surface roughness after wire drawing is about ± 2
µm in the circumferential direction.
[0053] The surface roughnesses of the wires of the Comparative Examples 2 (using polybutene)
and 5 (using polybutene and calcium soap) analyzed in the same procedure are both
about ± 4 µm.
Example 13 ∼ 38
[0055] It can be seen from the results shown in Table 4 that if an amount of fats and oils
or aliphatic dicarboxylic acids to be incorporated is lower than 2% by weight, the
die temperature rises rapidly and the surfaces of the wires become in the state just
before galling. Even if it is higher than 20% by weight, there is a tendency that
further improvement of the surface properties is unattainable.
Example 39
[0056] Using the lubricant prepared by incorporating 10% by weight of lanolin into polybutene
having a viscosity of 0.0002 to 0.3 m²/s (200 to 300,000 cSt at a temperature of 40°C,
the same aluminum-cladding steel composite substances as in Example 2 were subjected
to wire drawing under a working reduction of 20% with the drawing machine as shown
in FIGURE 1. Variation of the die temperature was measured as a function of the viscosity
of the base oil. The results are shown in FIGURE 4.
[0057] When the viscosity was not higher than 0.0003 m²/s (300 cSt), the die temperature
increased greatly. Moreover, when the drawing was temporarily stopped and then again
started, there were cases where the wires fracture.
[0058] On the other hand, if the viscosity is above 0.035 m²/s (35,000 cSt), the die temperature
begins to rise and the carry-over of lubricant increases with the lubricant being
apt to adhere to the single decked wire drawing machine, winding dram, floor and the
like, that is, the workability, particularly, manageability of the lubricant during
replenishment thereof being poor. The viscosity of lubricants should be up to about
0.05 m²/s (50,000 cSt).
Example 40
[0059] Using the lubricant comprising 90% by weight of ethylene-α-olefin copolymer having
a viscosity of 0.031 m²/s (31,000 cSt) at a temperature of 40°C and 10% by weight
of lanolin, the aluminum-cladding steel composite substances having a diameter of
8.4 mm were subjected to wire drawing through eleven stages with the continuous multi-stage
wire drawing machine as shown in FIGURE 2. The practical performance of the lubricant
was evaluated. The results obtained by observing the surface properties of the wires
after drawing, working condition and the ratio in cross-sectional area of the core
to the cladding layer are indicated in Table 5.
[0060] As can be seen from the results shown in Table 5, remarkably good surface properties
and smooth wire drawing could be achieved. The ratio in cross-sectional area of the
core and the cladding was excellently in the range of 34.8 to 36.0%. Moreover, the
surfaces contaminated with the lubricant of the wires after the eleven stages was
washed by rotating brush 12 with trichlene solvent 11 in treating chamber 9 as shown
in FIGURE 2 and one washing step was sufficient to remove almost perfectly the lubricant
adhered to the surface.

Example 41
[0061] The aluminum-cladding steel wires (the individual wire has a diameter of 2.9 mm)
obtained in Example 40 were twisted under the conditions of a number of wires of 30
and a cross-sectional area of 200 mm² with the tandem high velocity twisting machine
and the practical performance was evaluated. As a result, there could be obtained
a normal twisted wires having no flaw on the surfaces thereof.
[0062] The use of the aforementioned lubricant upon twisting operation is more effective
to give such twisted wires.
Examples 42 to 52 and Comparative Examples 8 to 14
[0063] A number of aluminum substances of A 2218 (O) (annealed from 400°C to room temperature
according to JIS-H4000) of a ring type having dimensions of 63 mm in outside diameter × 12
mm in inside diameter × 12 mm in thickness as shown in FIGURE 5 was coated on its
surface with the lubricants having the same compositions as in Examples 1 to 11 and
Comparative Examples 1 to 7 and were subjected to plastic working at a velocity of
40 pieces/min to produce 2000 parts having the configuration as shown in FIGURE 6.
The surface conditions are indicated in Table 6. It can be seen from the table that
workpieces worked in accordance with the present invention have no galling generated,
but excellent surface conditions.

Example 53
[0064] Y-Ba-Cu-O and Bi-Ca-Cu-O system superconductive substances in the form of pellet
produced by an oxide-kneading process were introduced in a tube of oxygen-free copper
C 1020 (JIS H 3300) and an aluminum tube A 1070 (JIS H 4080) having dimensions 8 mm
in outside diameter × 0.6 mm in thickness. After the opposite ends are sealed, the
tubes were subjected to swaging by using a lubricant composition comprising 90% by
weight of ethylene-α-olefin copolymer having a viscosity of 0.031 m²/s (31000 cSt)
at a temperature of 40°C and 10% by weight of lanolin to reduce the outside diameter
to 6 mm. These substances were subjected to wire drawing at a drawing velocity of
110/min through five stages with the same die as in Example 1 to produce superconductive
wires having a diameter of 2.9 mm. The results are indicated in Table 7.

[0065] As clearly seen from Table 7, the surfaces of the wires after drawing are excellent
without any galling generated and no cracks were formed inside the wires.
Example 54
[0066] The superconductive wires having a diameter of 2.9 mm obtained in Example 53, No.
1 and No. 3, were rolled repeatedly 5 to 8 times by using a lubricant composition
comprising 90% by weight of ethylene-α-olefin copolymer and 10% by weight of lanolin
to produce tapes having a thickness of 0.1 mm. The resulting tapes were remarkably
good without any galling generated on their surfaces. No cracks were generated inside
the tapes.
[0067] The method for plastic drawing in according to the present invention allows the plastic
drawing to be effected generating no galling and the like and to provide high quality
non-ferrous parts since the parts after working have an excellent surface condition.
[0068] Furthermore, the lubricant composition according to the present invention has an
excellent antigalling property and a high lublicity even during high velocity wire
drawing. Therefore, it allows the high velocity wire drawing and the high velocity
twisting to be smoothly effected and allows excellently the quality of wires and the
productivity to be improved.
[0069] Moreover, the wire drawing method according to the present invention can provide
sufficiently acceptable composite wires with respect to conductivity (the thickness
of the cladding is constant).
[0070] The lubricant for use in wire drawing in accordance with the present invention is
excellent in workability and safty of operation because of its low viscosity.