[0001] The present invention relates to a lubricant for hot metal working. In particular,
it relates to a lubricant for the precision forging of superalloys for turbine engines.
[0002] The manufacture of precision engineered machines such as jet engines requires that
various metal component parts be hot worked by forging, extruding, rolling, or by
similar processes. These processes entail rapidly applying high pressure by means
of a metal die or other tool to the part being worked to induce a high strain rate.
The tools are often made of various steels such as H13 type tool steel. The parts
are typically fabricated from materials such as titanium alloys, nickel alloys, or
stainless steels. To facilitate these processes, the part and the tool are coated
with a lubricant which minimizes friction between the part and tool and prevents metal
to metal contact.
[0003] One class of hot metal working lubricants which is widely used is glass lubricants.
These lubricants comprise ground glass particles which are suspended in a carrier.
Such lubricants are applied to the part to be worked to reduce friction and minimize
metal to metal contact which results in damage to the tool and part. Examples of commercially
available lubricants include GP-803 available from Graphite Products (Brookfield,
OH) and Deltaglaze
TM 13 and 17 available from Acheson Colloids (Port Huron, MI).
[0004] Despite the use of commercially available glass lubricants, some materials remain
difficult to hot work, especially in precision or net forging operations. Titanium
alloys in particular have proven troublesome. Due to their high strength, these alloys
require extremely high pressures in order to be worked, resulting in high friction
conditions which commercially available lubricants cannot obviate entirely. For example,
forge loads of 454 metric tons (500 short tons) to 1814 metric tons (2000 short tons),
which can result in surface pressures in excess of 1.4 GPa (100 tons per square inch)
or more, are typical. At these pressures, lubricants are subjected to high shear stresses
and temperatures which cause them to lose their lubricating properties. The loss of
lubricating properties is related to changes in viscosity, surface tension, density,
and chemistry. Without adequate lubrication, metal tools wear rapidly and friction
between the tool and part often ruptures the surface of the part. In addition, metal
to metal contact occurring under these conditions can result in localized welding
of the part to the tool, further damaging the part and tool. As a result, dies must
be repaired or replaced frequently and parts can require extensive reworking.
[0005] Accordingly, much effort has been made in the past to develop lubricants which can
reduce the friction between a tool and part in hot working operations which are carried
out at extremely high pressures, but thus far has fallen short of meeting all of the
objectives. Therefore, what is needed in this field is a lubricant which will be capable
of operating at the extremely high pressures used to hot work titanium alloys and
like materials.
[0006] The present invention is directed towards providing a lubricant which can reduce
friction between a tool and part in hot working operations which are carried out at
extremely high pressures.
[0007] One aspect of the invention includes a rheologically controlled glass lubricant for
hot metal working comprising a mixture of a glass powder, a binder, a rheological
agent, and a wetting and viscosity modifier.
[0008] Another aspect of the invention includes a forged metal part with a smooth, rupture-free
surface comprising a metal body formed into a desired shape by coating the metal body
with a rheologically controlled glass lubricant. The lubricant comprises a mixture
of a glass powder, a binder, a rheological agent, and a wetting and viscosity modifier.
The coated metal body is heated, placed in a forge and sufficient pressure to deform
the coated metal body into a desired shape is rapidly applied.
[0009] The foregoing and other features and advantages of the present invention will become
more apparent from the following description and accompanying drawings.
Brief Description of the Drawings
[0010] Figure 1 shows a titanium alloy forging for which a prior art glass lubricant was
used.
[0011] Figure 2 shows a titanium alloy forging for which the present invention was used
as a lubricant.
[0012] The present invention is an improved lubricant for hot metal working under extremely
high pressures. It comprises a mixture of a glass powder, a binder, a rheological
agent, and a wetting and viscosity modifier. These components may be either a dry
mixture or dispersed in a carrier. This combination of materials provides a lubricant
which does not lose its lubricating properties when subjected to high pressures, temperatures,
and shear stresses. The lubricant may be used with a wide variety of metals and metal
working operations.
[0013] The glass powder provides the basic lubricating activity of the present invention,
especially when the part being hot worked is subjected to mild pressures, by fusing
to form a continuous lubricating coating on the part when it is heated prior to the
metal working operation. This continuous lubricating coating will be referred to as
the glass base lubricant or base lubricant. The glass powder may be any of a number
of glass powders or frits which have been used in the manufacture or formation of
existing hot metal working lubricants. Generally, any glass powder with a viscosity
of between about 10² poises to about 10⁴ poises at a working temperature of about
899°C (1650°F) to about 1149°C (2100°F) would be suitable. Typically, such a glass
powder will have a softening point of about 649°C (1200°F) and an as received particle
size of about 150 microns to about 0.5 millimeters. Glass powder suitable for use
at temperatures up to about 954 °C (1750°F) is available from Specialty Glass (Oldsmar,
FL) and can have the following composition: 1 % by weight (%wt) to 3 %wt Al₂O₃; 25
%wt to 35 %wt PbO; <0.1 %wt MgO; <0.5 %wt CaO; 5 %wt to 8.5%wt Na₂O; balance SiO₂.
Of course, one skilled in the art will realize that this is but one of many compositions
which would be suitable for use with this invention. The glass powder should make
up about 48 %wt to about 55 %wt of the lubricant.
[0014] The binder improves the adhesion of the lubricant to the surface to which it is applied
by forming a mechanical bond with the surface. Suitable binders include alkyd and
silicone resins; water based emulsions such as vinyl acetate and vinyl alcohol; and
thermoplastic resins such as polyacrylates, polyvinyl benzene, and styrene butadienes.
The preferred binder is a styrene butadiene. The binder should make up between about
5 %wt to about 20 %wt of the lubricant. Preferably, the binder will make up about
15 %wt of the lubricant. The binders may be dissolved in a compatible carrier such
as xylene; trichloroethylene; glycol ether; alcohols, such as methyl alcohol and isopropyl
alcohol; ketones, such as methylethyl ketone; or water. Xylene is the preferred organic
carrier, while water is the preferred inorganic carrier.
[0015] Commercially available products which comprise a suitable glass powder and binder
dispersed in a carrier may be used to supply the glass powder and binder. Suitable
products include GP-803, available from Graphite Products (Brookfield, OH), and DeltaglazeTM
₁₃ and 17, available from Acheson Colloids (Port Huron, MI). The preferred commercial
product for use with this invention is Deltaglaze
TM 17 because it uses xylene as a carrier. If a commercial product is used, sufficient
product should be used to provide the above specified amounts of glass powder and
binder in the final lubricant.
[0016] The rheological agent serves to control the flow of the liquid glass base lubricant,
hence the use of term rheological agent. Secondarily, the rheological agent supports
the load on the part and prevents metal to metal contact between the part and tool
when the hydrodynamic glass base lubricant film suffers catastrophic breakdown at
high pressure. The rheological agent should be able to function as a lubricant under
pressures above about 40 tons/in². Typically, materials such as BN, Ni, NiO, and Cr₂O₃
will meet this requirement. They are incorporated into the invention as particles
which may be suspended in the carrier. BN is the preferred rheological agent because
it has a laminar structure. The particles should be about 5 microns to about 40 microns
in diameter. Preferably, the particles will be about 6 microns to about 15 microns
in diameter. They make up between about 3 %wt and about 6 %wt of the lubricant. Preferably,
they will make up about 5 %wt to about 6 %wt of the lubricant.
[0017] The wetting and viscosity modifier alters and controls the flow properties or rheology
of the glass base lubricant to extend the range of pressures over which it will provide
good lubricating properties by preventing the viscosity of the glass base lubricant
from breaking down at high pressures. Compounds which are silica lattice modifiers
make suitable wetting and viscosity modifiers. Preferred compounds include sodium
tetraborate, potassium tetraborate, boric acid, lead monosilicate, and lead bisilicate.
Potassium tetraborate is the most preferred viscosity modifier because of its effect
on viscosity adjustment. The viscosity modifier should make up about 4 %wt to about
8 %wt of the lubricant. Preferably, the lubricant will comprise 5 %wt to about 7 %wt
viscosity modifier.
[0018] The glass powder, binder, rheological agent, and wetting and viscosity modifier may
be a dry mixture or may be dispersed in a carrier. Preferably, the materials will
be dispersed in a carrier to make the lubricant more convenient to apply. If the glass
powder and binder are already dispersed in a carrier, as would be the case if a commercial
product were the source of these components, any additional carrier must be compatible
with the carrier in which the glass powder and binder are dispersed. Preferably, any
additional carrier will be the same material used as a carrier for the glass powder
and binder. The carrier may be any of a number of organic or inorganic materials including
xylene; trichloroethylene; glycol ether; alcohols, such as methyl alcohol and isopropyl
alcohol; ketones, such as methylethyl ketone; or water. Xylene is a preferred carrier.
The carrier should make up between 35 %wt to about 45 %wt of the lubricant. Preferably,
it will be about 38 %wt to about 42 %wt.
[0019] The invention is made by mixing the glass powder, binder, rheological agent, viscosity
modifier, and carrier, if any, and milling them in a reduction mill, such as a ball
mill, until the mixture is homogeneous and the particles are of a suitable size. The
majority of the glass particles should be between 1 micron and 30 microns in diameter
after milling. Preferably, the majority of the particles should be 5 microns to 12
microns in diameter. The milling operation may take up to 8 hours.
[0020] If the lubricant contains a carrier, the milling operation produces a complex suspension
whose viscosity will tend to fluctuate during the first several hours after it is
prepared, making its properties somewhat unpredictable. Therefore, the lubricant should
be stabilized before use to ensure adequate results. One way to stabilize the lubricant
is to store it in sealed containers for at least 24 hours and preferably for at least
48 hours to permit it to age. Another way to stabilize the lubricant is to put it
into a dynamic storage device, such as a constantly rotating container. Dynamic storage
prevents viscosity fluctuation by constantly mixing the lubricant. If the lubricant
is stored in a dynamic storage device, it may be used at any time after preparation.
If the lubricant is a dry mixture, it needs no stabilization and can be used immediately
after preparation.
[0021] The finished lubricant may be applied to a part to be worked by any appropriate method.
For example, if the lubricant is a mixture dispersed in a carrier, it can be applied
by painting, dipping, electrostatic spraying, or conventional spraying. If the lubricant
is a dry mixture, it can be applied by conventional spraying, electrostatic spraying,
electrophoretic application, or by placing a heated part in a fluidized bed of the
lubricant. Regardless of whether the lubricant is a wet or dry mixture, it should
form a dry film of about 0.004 g/cm² to about 0.015 g/cm² when applied to the part
to be worked. This loading corresponds to a coating of about 0.025 mm (0.001 inch)
to about 0.13 mm (0.005 inch) thick. If the film is too thin, it will not provide
adequate lubrication. If the film is too thick, poor metal flow will result when operating
pressures are applied. Preferably, the lubricant will form a dry film of about 0.0060
g/cm² to about 0.0107 g/cm², corresponding to a coating of about 0.051 mm (0.002 inch)
to about 0.076 mm (0.003 inch) thick, especially when it is to be used with titanium
alloys. If a test sample of the coating is found to be too thick, additional carrier
may be added to dilute the lubricant. If the coating is too thin, carrier may be allowed
to evaporate from the lubricant or a thixotrope may be added. Thixotropes are inorganic
or organic rheological additives which can thicken the lubricant. They must be compatible
with the carrier used in the lubricant. Preferred organic thixotropes include bentones,
micronized hydrogenated castor oil, castor oil, ethane diol, or methyl cellulose.
Preferred inorganic thixotropes include fumed silica, bentonite, or water.
[0022] If the lubricant has a carrier, it must be dried after being applied to the part.
This can be accomplished by heating the lubricant to a temperature above the solvent's
boiling point or by allowing the lubricant to air dry. If the lubricant is a dry mixture,
it needs no drying. After the lubricant has been dried, the part must be heated to
fuse the glass powder into the base lubricant. The part must be heated to at least
the softening point of the glass. Once the glass powder has fused, the part is ready
to be hot worked.
[0023] The lubricant may be used with a wide range of metals in a number of different hot
working operations. For example, the lubricant has been found to be suitable for use
with titanium alloys, particularly Ti8-1-1, Ti6-4, and Ti6-2-4-2 over the temperature
range of about 946°C (1735°F) to about 1004°C (1840°F). It is also compatible with
nickel alloys and stainless steels used in aerospace engines and commonly called superalloys.
The lubricant is useful in reducing friction in forging operations in general, and
particularly in conventional precision or net forging operations in which pressure
is rapidly applied to the part to be worked, inducing a high strain rate. It can also
be used to reduce friction in extrusion, blocking, heading, and rolling operations.
The lubricant can be used at temperatures ranging from about 849°C (1560°F) up to
the temperature at which the rheological agent decomposes. If the working temperature
is much below about 840°C (1560°F), the lubricant will be too stiff to function properly.
Preferably, the minimum working temperature will be about 899°C (1650°F).
Example
[0024] A ball milling machine manufactured by U.S. Stoneware (Mahwah, NJ) was prepared for
mixing the lubricant. 12 kg of pebbles were milled in a ball mill jar in the presence
of 1 kg of abrasive material and an ample amount of clean water for 48 hours in order
to condition the media. The abrasive material was then removed and the water and any
very small or split pebbles were discarded. The jar and its pebble charge were thoroughly
dried.
[0025] After the jar and pebbles were dry, 6.245 kg of Deltaglaze
TM 17 (available from Acheson Colloids, Port Huron, MI) and 915.4 g of xylene were added
to the jar. 432.4 g of BN particles available as Grade HCP from Union Carbide Coatings
Service Corp. (Cleveland, OH) were carefully added to the jar. Finally, 506.6 g of
potassium tetraborate available from United States Borax Corp. (Los Angeles, CA) were
added to the jar. The ball mill jar was place on the mill and the mill was started.
After 7 hours, the mill was stopped and the jar was removed. The lubricant was strained
into a clean metal can through a muslin cloth and a straining plate. The can was closed
and the lubricant was permitted to age for 48 hours.
[0026] After the aging period was over, the can was opened and the lubricant was gently
stirred with a wooden paint stirrer to ensure that all sediment was blended into the
body of the lubricant. While stirring, care was taken to avoid entrapping air in the
lubricant. A clean, chemically milled metal extrusion was dipped into the lubricant
and hung up to dry for 1 hour at ambient temperature. When dry, the coating thickness
was measured with a micrometer and found to be 0.064 mm (0.0025 inch) thick. As this
thickness was within the preferred range of 0.051 mm (0.002 inch) to 0.076 mm (0.003
inch), which corresponds to a loading of about 0.01 g/cm2, no additional carrier was
needed.
[0027] This invention was found to drastically reduce wear on forging dies and surface damage
to titanium alloy parts when applied to the parts prior to forging. For example, die
life measured in average pieces per die improved by up to 300% to 400% when a prior
art lubricant was replaced with the invention for forging titanium alloy parts. The
decrease in die wear is attributed to the improved ability of the invention to reduce
friction and prevent metal to metal contact between the part and die during forging
at extremely high pressures.
[0028] A comparison of Figs. 1 and 2 shows the improvement to the part surface which results
from using the invention. Fig. 1 is a photomicrograph of the surface of a Ti6-2-4-2
part which was coated with a prior art lubricant before forging. Areas of shearing
and surface rupture which result from metal to metal contact with the die are evident.
This sort of damage to the part results in corresponding damage to the die which must
be repaired by dressing, a hand operation which reduces die life. A part with damage
like this is unacceptable as a finished piece and must be reworked by hand to repair
the surface.
[0029] Fig. 2 is a photomicrograph of the surface of a similar Ti6-2-4-2 part which was
coated with a lubricant of a composition similar to that disclosed in the example
before forging. The surface is uniform and displays no evidence of shearing or rupture.
This is evidence of little or no metal to metal contact between the part and die.
A part with a surface like this is acceptable as a finished piece and needs no reworking.
[0030] The improved die life and decreased part damage result from improved lubrication
and less metal to metal contact at forging conditions. The viscosity modifier in the
invention enhances the glass base lubricant so it can provide lubrication at the extremely
high pressures encountered when forging titanium alloy and nickel and stainless steel
superalloy parts. The rheological agent controls glass base lubricant flow and provides
additional lubrication under these pressures and helps to prevent metal to metal contact.
[0031] The invention also improves the movement or deformation of the metal being forged
by decreasing the friction between the tool and the part. As a result, when the invention
is used as the lubricant, lower forge pressures are needed to achieve the desired
deformation than if a prior art lubricant is used. The lower forging pressures further
improve die life and decrease part damage.
[0032] Decreased die wear means that dies need to be replaced less frequently and require
less hand dressing to repair damage. The improvement to the part surface reduces or
eliminates the need for hand repair. Another benefit of reduced part damage is improved
dimensional reproducibility of the parts. Because the parts do not require hand working,
each part is more uniform. This can also be expressed as an improvement in process
control because the results obtained during the forging operation are more uniform
and predictable.
[0033] The fact that dies do not need to replaced as frequently and parts do not require
extensive rework means that forge throughput can be increased for the same expenditures
in materials and labor. Alternately, throughput can be held constant and material
and labor requirements can be decreased.
[0034] Finally, the range of temperatures over which the lubricant can function was found
to be broader than that of many prior art lubricants. Therefore, it is possible to
use the invention for a wider range of applications than is possible with a single
prior art lubricant. This can simplify inventory requirements because, in essence,
the invention can replace several prior art lubricants.
1. A rheologically controlled glass lubricant for hot metal working, comprising a mixture
of:
(a) a glass powder comprising 1 wt% to 3 %wt Al₂O₃, 25 %wt to 35 %wt PbO, <0.1 %wt
MgO, <0.5 %wt CaO, 5 %wt to 8.5 %wt Na₂O, balance SiO₂, wherein the glass powder has
a particle size of 1µ to 30µ, a viscosity of about 10² poises to about 10⁴ poises
when heated to temperatures between 899°C and 1149°C and is capable of forming a glass
base lubricant on a metal part that will be hot worked;
(b) a binder selected from the group consisting of alkyd and silicone resins, water-based
emulsions, and thermoplastic resins;
(c) a rheological agent capable of functioning as a lubricant at pressures higher
than about 550 MPa; and
(d) a wetting and viscosity modifier selected from the group consisting of sodium
tetraborate, potassium tetraborate, boric acid, lead monosilicate, and lead bisilicate,
wherein the wetting an viscosity modifier is capable of inhibiting the viscosity of
the glass base lubricant from breaking down at high pressures to extend the range
of pressures over which the glass base lubricant has lubricating properties.
2. The glass lubricant of claim 1 further comprising a carrier selected from the group
consisting of xylene, trichloroethylene, glycol ether, alcohols, ketones, and water.
3. The glass lubricant of claim 2 comprising 48 %wt to 55 %wt glass powder, 5 %wt to
20 %wt binder, 3 %wt to 6 %wt rheological agent, 4 %wt to 8 %wt wetting and viscosity
modifier, and 35 %wt to 45 %wt carrier.
4. The glass lubricant of claims 1 to 3 wherein:
the rheological agent is selected from the group consisting of BN, Ni, NiO, and
Cr₂O₃.
5. The glass lubricant of claims 1, to 3 wherein:
the binder is a styrene butadiene,
the rheological agent is BN, and
the wetting and viscosity modifier is potassium tetraborate.
6. The glass lubricant of claim 2 wherein the carrier is xylene.
7. The glass lubricant of claims 1 or 2 wherein the glass lubricant forms a dry film
of 0.004 g/cm² to 0.015 g/cm² on the metal part to be hot worked.
8. A method of forging a metal body into a desired shape, comprising the steps of:
(a) coating the metal body with a rheologically controlled glass lubricant which comprises
a mixture of:
(i) a glass powder comprising 1 wt% to 3 %wt Al₂O₃, 25 %wt to 35 %wt PbO, <0.1 %wt
MgO, <0.5 %wt CaO, 5 %wt to 8.5 %wt Na₂O, balance SiO₂, wherein the glass powder has
a particle size of 1µ to 30µ, a viscosity of 10² poises to 10⁴ poises when heated
to temperatures between 899°C and 1149°C and is capable of forming a glass base lubricant
on a metal part that will be hot worked;
(ii) a binder selected from the group consisting of alkyd and silicone resins, water-based
emulsions, and thermoplastic resins;
(iii) a rheological agent capable of functioning as a lubricant at pressures higher
than about 550 MPa; and
(iv) a wetting and viscosity modifier selected from the group consisting of sodium
tetra borate, potassium tetraborate, boric acid, lead monosilicate, and lead bisilicate,
wherein the wetting an viscosity modifier is capable of inhibiting the viscosity of
the glass base lubricant from breaking down at high pressures to extend the range
of pressures over which the glass base lubricant has lubricating properties;
(b) heating the coated metal body;
(c) placing the coated metal body in a forge;
(d) rapidly applying sufficient pressure to deform the coated metal body into a desired
shape;
whereby the forged metal body has a smooth, rupture-free surface.
9. The method of claim 8 wherein the metal body comprises a material selected from the
group consisting of a titanium alloy, a nickel superalloy, and a stainless steel superalloy.
10. The method of claim 8 or 9 wherein the rheologically controlled glass lubricant further
comprises a carrier selected from the group consisting of xylene, trichloroethylene,
glycol ether, alcohols, 5 ketones, and water.
11. The method of claims 8 to 10 wherein: the rheological agent is selected from the group
consisting of BN, Ni, NiO, and Cr₂O₃.
1. Rheologisch gesteuertes Glasschmiermittel zur Metallwarmumformung, beinhaltend eine
Mischung aus:
(a) ein Glaspulver bestehend aus 1 Gew.% bis 3 Gew.% Al₂O₃, 25 Gew.% bis 35 Gew.%
PbO, <0,1 Gew.% MgO, <0,5 Gew.% CaO, 5 Gew.% bis 8,5 Gew.% Na₂O, Rest SiO₂, wobei
das Glaspulver eine Partikelgröße von 1 µm bis 30 µm, eine Viskosität von etwa 10²
Poise bis etwa 10⁴ Poise hat, wenn es auf Temperaturen zwischen 899 °C und 1149 °C
erhitzt wird, und in der Lage ist, ein Glasbasisschmiermittel auf einem Metallteil
zu bilden, das warmumgeformt wird;
(b) einem Bindemittel, das aus der Gruppe ausgewählt ist, die aus Alkyd und Siliconharzen,
Emulsionen auf Wasserbasis und thermoplastischen Harzen besteht;
(c) einem rheologischen Mittel, das in der Lage ist, bei Drücken über mehr als etwa
550 MPa als ein Schmiermittel zu dienen; und
(d) einem Benetzungs- und Viskositätsmodifiziermittel, ausgewählt aus der Gruppe,
die aus Natriumtetraborat, Kaliumtetraborat, Borsäure, Bleimonosilicat und Bleibisilicat
besteht, wobei das Benetzungs- und Viskositätsmodifiziermittel in der Lage ist, die
Viskosität des Glasbasisschmiermittels daran zu hindern, bei hohen Drücken zusammenzubrechen,
um den Bereich von Drücken auszudehnen, in welchem das Glasbasisschmiermittel Schmiereigenschaften
hat.
2. Glasschmiermittel nach Anspruch 1, weiter beinhaltend einen Träger, ausgewählt aus
der Gruppe, die aus Xylol, Trichlorethylen, Glycolether, Alkoholen, Ketonen und Wasser
besteht.
3. Glasschmiermittel nach Anspruch 2, beinhaltend 48 Gew.% bis 55 Gew.% Glaspulver, 5
Gew.% bis 20 Gew.% Bindemittel, 3 Gew.% bis 6 Gew.% rheologisches Mittel, 4 Gew.%
bis 8 Gew.% Benetzungs und Viskositätsmodifiziermittel und 35 Gew.% bis 45 Gew.% Träger.
4. Glasschmiermittel nach den Ansprüchen 1 bis 3, wobei: das rheologische Mittel aus
der Gruppe ausgewählt ist, die aus BN, Ni, NiO und Cr₂O₃ besteht.
5. Glasschmiermittel nach den Ansprüchen 1 bis 3, wobei:
das Bindemittel ein Styrolbutadien ist,
das rheologische Mittel BN ist, und
das Benetzungs und Viskositätsmodifiziermittel Kaliumtetraborat ist.
6. Glasschmiermittel nach Anspruch 2, wobei der Träger Xylol ist.
7. Glasschmiermittel nach Anspruch 1 oder 2, wobei das Glasschmiermittel einen trockenen
Film von 0,004 g/cm² bis 0,015 g/cm² auf dem warmumzuformenden Metallteil bildet.
8. Verfahren zum Schmieden eines Metallkörpers in eine gewünschte Form, beinhaltend die
Schritte:
(a) Überziehen des Metallkörpers mit einem rheologisch gesteuerten Glasschmiermittel,
beinhaltend eine Mischung aus:
(i) einem Glaspulver mit 1 Gew.% bis 3 Gew.% Al₂O₃, 25 Gew.% bis 35 Gew.% PbO, <0,1
Gew.% MgO, <0,5 Gew.% CaO, 5 Gew.% bis 8,5 Gew.% Na₂O, Rest SiO₂, wobei das Glaspulver
eine Partikelgröße von 1 µm bis 30 µm hat, eine Viskosität von 10² Poise bis 10⁴ Poise,
wenn es auf Temperaturen zwischen 899 °C und 1149 °C erhitzt wird, und in der Lage
ist, ein Glasbasisschmiermittel auf einem Metallteil zu bilden, das warmumgeformt
wird;
(ii) einem Bindemittel, ausgewählt aus der Gruppe, die aus Alkyd und Siliconharzen,
Emulsionen auf Wasserbasis und thermoplastischen Harzen besteht;
(iii) einem rheologischen Mittel, das in der Lage ist, bei Drücken über etwa 550 MPa
als Schmiermittel zu dienen; und
(iv) einem Benetzungs- und Viskositatsmodifiziermittel, ausgewählt aus der Gruppe,
die aus Natriumtetraborat, Kaliumtetraborat, Borsäure, Bleimonosilicat und Bleibisilicat
besteht, wobei das Benetzungs- und Viskositätsmodifiziermittel in der Lage ist, die
Viskosität des Galsbasisschmiermittels daran zu hindern, bei hohen Drücken Zusammenzubrechen,
um den Bereich von Drücken auszudehnen, in welchem das Glasbasisschmiermittel Schmiereigenschaften
hat;
(b) Erhitzen des überzogenen Metallkörpers;
(c) Einbringen des überzogenen Metallkörpers in eine Schmiedemaschine;
(d) schnelles Ausüben von ausreichendem Druck, um den überzogenen Metallkörper in
eine gewünschte Form zu verformen;
wodurch der geschmiedete Metallkörper eine glatte, rißfreie Oberfläche hat.
9. Verfahren nach Anspruch 8, wobei der Metallkörper ein Material umfaßt, das aus der
Gruppe ausgewählt wird, die aus einer Titanlegierung, einer Nickelsuperlegierung und
einer rostfreien Stahlsuperlegierung besteht.
10. Verfahren nach Anspruch 8 oder 9, wobei das rheologisch gesteuerte Glasschmiermittel
weiter einen Träger umfaßt, der aus der Gruppe ausgewählt wird, die aus Xylol, Trichlorethylen,
Glycolether, Alkoholen, Ketonen und Wasser besteht.
11. Verfahren nach den Ansprüchen 8 bis 10, wobei: das rheologische Mittel aus der Gruppe
ausgewählt wird, die aus BN, Ni, NiO und Cr₂O₃ besteht.
1. Un lubrifiant de verre régulé rhéologiquement pour le façonnage de métal à chaud,
comprenant un mélange de:
(a) une poudre de verre comprenant 1 %wt à 3 %wt Al₂O₃, 25 %wt à 35 %wt PbO, <0,1 %wt
MgO, <0,5 %wt CaO, 5 %wt à 8,5 %wt Na₂O, le complément étant du SiO₂, dans lequel
la poudre de verre a une dimension de particules de 1µ à 30µ, une viscosité d'environ
10² poises à environ 10⁴ poises lorsqu'elle est chauffée à des températures entre
899°C et 1149°C et est capable de former un lubrifiant de base en verre sur un élément
de métal qui sera façonné à chaud;
(b) un liant choisi dans le groupe comprenant les résines alkydes et de silicones, des
émulsions à base d'eau, et des résines thermoplastiques;
(c) un agent rhéologique capable de fonctionner comme lubrifiant à des pressions supérieures
à environ 550 MPa; et
(d) un agent mouillant et modifiant la viscosité choisi dans le groupe comprenant le
tétraborate de sodium, le tétraborate de potassium, l'acide borique, le monosilicate
de plomb et le bisilicate de plomb dans lequel l'agent de mouillage et modifiant la
viscosité est capable d'empêcher la viscosité des lubrifiants à base de verre de se
rompre à des pressions élevées pour augmenter l'intervalle de pression sur lequel
le lubrifiant de base en verre a des propriétés lubrifiantes.
2. Lubrifiant de verre selon la revendication 1 comprenant en outre un véhicule choisi
dans le groupe consistant en xylène, trichloroéthylène, glycol éther, alcools, cétones
et eau.
3. Lubrifiant de verre selon la revendication 2 comprenant 48 %wt à 55 %wt de poudre
de verre, 5 %wt à 20 %wt de liant, 3 %wt à 6 %wt d'agent rhéologique, 4 %wt à 8 %wt
d'agent mouillant et modifiant la viscosité, et 35 %wt à 45 %wt de véhicule.
4. Lubrifiant de verre selon les revendications 1 à 3 dans lequel l'agent rhéologique
est choisi dans le groupe consistant en BN, Ni, NiO, et Cr₂O₃.
5. Lubrifiant de verre selon les revendications 1 à 3 dans lequel:
le liant est un styrène-butadiène,
l'agent rhéologique est du BN, et
l'agent de mouillage et modifiant la viscosité est du tétraborate de potassium.
6. Lubrifiant de verre selon la revendication 2 dans lequel le véhicule est du xylène.
7. Lubrifiant selon les revendications 1 ou 2 dans lequel le lubrifiant de verre forme
un film sec de 0,004 g/cm² à 0,015 g/cm² sur un élément métallique à façonner à chaud.
8. Un procédé pour forger un corps métallique en une forme souhaitée, comprenant les
étapes de:
(a) enduire le corps métallique au moyen d'un lubrifiant de verre régulé rhéologiquement
qui comprend un mélange de:
(i) une poudre de verre comprenant 1 %wt à 3 %wt Al₂O₃, 25 %wt à 35 %wt PbO, <0,1 %wt
MgO, <0,5 %wt CaO, 5 %wt à 8,5 %wt Na₂O, le complément étant du SiO₂, où la poudre
de verre a une dimension de particules de 1µ à 30µ, une viscosité de 10² poises à
10⁴ poises lorsqu'elle est chauffée à des températures entre 899°C et 1149°C et est
capable de former un lubrifiant de base en verre sur l'élément métallique qui sera
façonné à chaud;
(ii) un liant choisi dans le groupe comprenant les résines alkydes et de silicones, des
émulsions à base d'eau et des résines thermoplastiques;
(iii) un agent rhéologique capable de fonctionner comme lubrifiant à des pressions supérieures
à environ 550 MPa; et
(iv) un agent de mouillage et modifiant la viscosité choisi dans le groupe comprenant
le tétraborate de sodium, l'acide borique, le monosilicate de plomb et le bisilicate
de plomb, où l'agent de mouillage et modifiant la viscosité est capable d'empêcher
la viscosité du lubrifiant de base en verre de se rompre à des pressions élevées pour
augmenter l'intervalle de pression sur lequel le lubrifiant de base en verre a des
propriétés lubrifiantes;
(b) chauffer le corps métallique enduit;
(c) disposer le corps métallique enduit dans une forge;
(d) appliquer rapidement une pression suffisante pour déformer le corps métallique enduit
en une forme souhaitée;
où le corps métallique forgé a une surface lisse sans fracture.
9. Procédé selon la revendication 8 dans lequel le corps métallique comprend une matière
choisie dans le groupe consistant en alliage de titane, superalliage de nickel, et
superalliage en acier inoxydable.
10. Procédé selon la revendication 8 ou 9 dans lequel le lubrifiant de verre régulé rhéologiquement
comprend en outre un véhicule choisi dans le groupe consistant en xylène, trichloroéthylène,
glycol éther, alcools, cétones, et de l'eau.
11. Procédé selon les revendications 8 à 10 dans lequel:
l'agent rhéologique est choisi dans le groupe consistant en BN, Ni, NiO, et Cr₂O₃.