Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to metallurgy and more
particularl~ to a process which provides~ox the cold working of
metallic materials, for instance, extrusion molding, wire draw- -
ing, the drawing of profiles, the drawing of tubes, the drawing
of sheet metal, particularly drawing procedures in which the
principle of hydrodynamic lubrication can be maintained. The
cold working of metallic materials to which the present inven-
tlon relates is the cold working of metallic material below its
temperature of recrystallization, preferentially at ambient
temperatures. Well known procedures applied in the cold working
of metallic materials include drawing, pressing, cold-forging,
cold-rollins and extruding. Such metallic materials include all
the metals, specifically steel and non-ferrous metals. Hydro-
dynamic lubrication refers to conditions, which are maintained,
when hydrodynamic lubrication principles are applied, i.e. no
direct contact is made between the cold working tool and the
metallic material which is subject to cold working forces. The
tool and material are separated from each other by a lubricant
which is applied to maintain a fluid friction system.
In the drawing of metallic materials solid, semi-solid
and/or liquid lubricants are applied. Well known liquid lubri-
cants include alkali metal stearates, which are, most often,
used in the form of aqueous solutions. These lubricants are fed
as liquids either directly in to the hole of the drawing die or
are applied to the surface of the materials to be drawn, dried
on said surface, and carried with the material to be drawn into
the hole of the drawing die. These lubricants are characterised
by a relatively moderate dynamic viscosity. Therefore, they can-
not be of use, when metallic materials of higher tensile strength
i.e. with a tensile strength which exceedslOOON/mm2have to be
drawn. Sodiumstearate ~orinstance,canonlybeused in drawing
metallic
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materials, the tensile strength of which may approach 1000 N/
mm . Moreover, it is rather difficult to achieve a continuous
multi-step metal reshaping procedure with alkali metal stearates
as lubricants due to the fact that the solvent used together
with the lubricating cornpound has a boiling temperature of 100 C.
Drying of the lubricant on the surface of the material to be
drawn as an alternative approach, is time consuming and has to
be done carefully. Insufficient drying of the applied lubri-
cant lowers its moderate dynamic viscosity even further.
Another disadvantage of this type of lubricant is
its inability to dissolve oil or grease. This shortcoming of
said lubricants may require the material, which has to be
drawn, to be degreased beforehand.
The present invention widens the field of application
of solid and semi-solid lubricants as well as providing a re-
duction in expenditures required for cold working metallic
materials.
The present invention provides a process which allows
the preparation of a homogeneous layer of lubricants character-
ised by their high dynamic viscosity, on the surface of high-
strength metallic materials, said lubricants being of use in
cold working.
In accordance with the present invention lubricants
are applied to the surface of the material, which has to be
cold worked, or to the specific surface of the tool with which
work is applied i.e. areas of the tool one makes use of in
cold working metallic materials, said lubricants comprising
calcium or zinc stearate dissolved in organic solvents, said
organic solvents being characterised by a boiling temperature
at atmospheric pressure which is below 200C, selected from
benzene, trichloroethylene, chloro~luorohydrocarbons, fluoro-
bromohydrocarbons, chlorobromofluorohydrocarbons and trifluoro-
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acetone.
The present invention provides a lubricant for working
metallic work materials, which comprises (a) at least one or-
ganic solvent selected from benzene, trichloroethylene, chloro-
fluorohydrocarbons, fluorobromohydrocarbons, chlorobromofluoro-
hydrocarbons and trifluoroacetone and (b) calcium stearate or
zinc stearate.
Technical benzene, i.e. a benzene fraction with a
low degree of purity may be used as an inorganic solvent.
Calcium stearate, assaying 29% metal oxide content may be used
as lubricant. To achieve short drying times for the coating
the process of the present invention uses organic solvents, the
boiling temperature of which is below 30 C. Alternatively the
process of the present invention uses mixtures of organic
solvents, in which at least one component has a boiling tem-
perature which is below 30C at atmospheric pressuxe, whereby
the lubricating compounds are present in a dissolved and/or
dispersed form. Useful solvents include chloro-fluoro-hydro-
carbons, such as tri-chloro-monofluoro-methane and dichloro-
monofluoro-methane, bromo-fluoro-hydrocarbons such as bromo-
monofluoro-methane, l-bromo-2-fluoroethylene and dibromo-fluoro-
methane, chloro-bromo-fluoro-hydrocarbons such as monochloro-
monobromo-difluoromethane and/or other chlorinated or fluorin-
ated organic compounds such as for instance trifluoro-acetone.
Further, cationic, anionic, amphoteric and/or non-
ionic surfactants may be incorporated into the lubricant whence
residual films of the lubricants can be simply and easily re-
moved from the drawn material with water, if necessary with warm
water. The residual film of lubricant is the film of lubricant
which
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remains on the surface of the metallic material after being
reshaped under cold-flow conditions. Cationic surfactants, which
can be used include fatty acid amides, higher molecular weight
alkylamines and substituted higher molecular weight alkylamines.
Anionic surfactants include alkylarylsulphonates, alkylsulphates,
alkylsulphonates, alkylarylphosphates, alkylphosphates and deri-
vatives thereof. Amphoteric surfactants include betaines, for
instance betaine/sulphate and sulphobetaine. Non-ionic sur-
factants include ethyleneoxide addition products and alkylolamides
of fatty acids.
In accordance with the process of the present invention
the lubricant is in liquid form and is applied homogeneously to
the material, which has to be drawn. The solvents are removed.
A residue of the lubricating compound remains on the surface of
the metal in the form of a solid film with good adherence to the
carrier. In general, it will not be necessary to first apply
lubricant bonding agents to improve the adherence of the lubri-
cants to the metal. Such bonding agents for lubricants are chemi-
cal compounds such as phosphates oxalates, bor~tes or burnt/lime,
with which the metallic material is coated before the lubricant is
applied mainly to improve the bond between the metal surface and
the lubricant. Lubricants, which are applied in this
manner combine in them the following advantages. They can be
prepared at moderate costs. As solid lubricants, characterised
by elevated dynamic viscosity they can be of use, when metallic
materials of higher strength have to be drawn. ~ homogeneous
application of the lubricant can be guaranteed as in the applica-
tion of liquid and semi-solid lubricants. The homogeneously
applied coating of solid lubricant on the material to be drawn
provides stable wire-drawing conditions i.e. hydrodynamic lubri-
cation is maintained throughout the drawing operation. The
lubricant can be of use in continuously running multi-stage wire
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drawing operations i.e. drawing procedures in which the metallic
material is transported through a number of drawing machines
assembled in series without interuption. When, in accordance
with the present invention, organic solvents are used, the boiling
temperature of which is below 30~C or when mixtures of organic
solvents are used, in which at least one component of the mixture
has a boiling temperature, which is below 30C, high speed draw-
ing i.e. speeds in drawing which are in excess of 5 meters per
second can be achieved due to the low boiling temperature of
the organic solvents which are used. This is true for continuous
multi-stagewire drawing operations which require intermediate
recoating steps i.e. applying another coating of lubricant onto
the material to be drawn in between two drawing machines operated
in series. When in accordance with the present invention, sur-
factants are incorporated into the lubricant the usual aftertreat-
ment procedures such as an aggressive pickling or the treatment
with degreasing compounds to remove residual lubricating films
can be eliminated.
Savings result. Smaller quantities of benzene or of
chlorinated hydrocarbons are consumed in removing the residual
lubricatin~ film, an operation which was required when the drawn
goods needed further processing. The cost of finishing the drawn
goods can be lowered substantially. By eliminating organic sol-
vents from the finishing operation the protective measures to be
operated and maintained in the area of work aresimpler and cost
less. Gases aspirated from the working area do not have to pass
a dust filter. They do not have to be purified either. No
environmental problems will arise.
The present invention will be further illustrated by
way of the following Examples.
Example 1
A practical form of realisation of this invention con- ¦
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sists of a proces5, in which th~ metallic material, which has
to ~e cold worked is coated with a lubricant preparation which
contains benzene as thè organic solvent and calcium stearate,
assaying 29% of metal oxide, as lubricating compound. The cal-
cium stearate is dissolved in benzene. This lubricant is parti-
cularly suited to be applied in hydrodynamic drawing operations,
for instance in the drawing of spring steel wire. A spring
steel wire, diameter 10 m~, in~tial tensile strength 1600 N/mm ,
E = 15%, coated with said lubricant preparation was reshaped in
excess of 8Q% by drawing it under cold flow conditions. After
passing the drawing die the drawn wire shows excellent surface
characteristics, and carries a homogeneous residual film of the
solid lubricant.
Example 2:
150 grams of calcium stearate are dissolved in 0.8
liters of benzene. To this solution are added 1.0 liter of tri-
chloro-fluoro-methane. This preparation leaves a solid and well
adhering coating on the material to be drawn. The drying time of
this lubricating preparationishalf of what is usually required.
With this lubricant applied in drawing operations high speeds
of drawing and high degrees of reshaping under cold-flow condi-
tions can be achieved due to the excellent dynamic viscosity of
the solid lubricant.
Example 3:
The metallic material to be drawn is coated with a
lubricating preparation obtained by dispersing and dissolving 90
grams of calcium stearate and 18 grams of octadecylbenzene sul-
phonate in 1 liter of trichloroethylene. After coating the me-
tallic material to be drawn with this preparation, a partial so-
lution and di$~ersion of the solid compounds in the organic sol-
vent, and after removal of the solvent, a solid film of the lu-
bricant remains characterised by high dynamic viscosity, which
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can easily be removed with water from the carrier before,as well
as after the reshaping operations such as: the drawing of wire,
of tubes, and of profiles, as well as after extrusion molding.
'O
