Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0637—Accessories therefor
  • B22D11/0665—Accessories therefor for treating the casting surfaces, e.g. calibrating, cleaning, dressing, preheating
  • B22D11/0668—Accessories therefor for treating the casting surfaces, e.g. calibrating, cleaning, dressing, preheating for dressing, coating or lubricating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/07—Lubricating the moulds

Definitions

• the present invention relates to a method of producing metal sheet by a
• this invention pertains to a process for producing
• Metal sheet, plate and foil products have been made by a variety of
• One process for producing aluminum and aluminum alloy sheet is the roll casting process.
• the present invention is particularly directed to the process of roll casting using twin casting rolls.
• molten metal which is
• Such rolls typically filtered and may be alloyed and refined, is fed between mating casting rolls.
• Such rolls may be of various widths and diameters, with 600 to 1 ,000 mm roll diameters being common, as are strip product widths on the order of 1 to 2 meter.
• the rolls are cooled, such as by internal liquid cooling, to cause the exterior surface of the roll shell to be maintained at a temperature sufficient to cause progressive solidification of the
• the metal sheet exiting the caster is coiled for subsequent hot rolling, cold rolling, homogenization and annealing.
• the casting speed must be controlled at a rate that insures that the outside walls of the sheet are adequately and progressively solidified. Also, casting speed must insure that the entire sheet is solidified prior to hot reduction of the sheet. Solidification must be uniform to insure that internal voids are not present. A surface void condition, called a bleed-out, must be avoided.
• a surface void condition called a bleed-out, must be avoided.
• As casting speed is increased it has been found that the casting roll surface temperature increases. Likewise, the temperature of the outside surface of the cast product increases. As the temperatures of the aluminum sheet being cast and the outside shell of the steel casting roll rise, the surfaces experience a surface welding which tends to cause sticking of the sheet to the roll. When such sticking occurs, the casting speed must be reduced.
• One approach to alleviating the sticking condition is to provide an agent
• Such agents include release agents which act to prevent sticking between the sheet and the outside shell of the casting roll.
• Typical agents that have been used in roll casting are graphite and magnesium oxide.
• the application of a thermal barrier may impede the cooling efficiency in the casting process since the thermal barrier serves as an insulative layer
• release agent onto the surface of a roll shell. Areas not covered by the release agent tend to cause microwelding to occur between the cast strip and the roll shell.
• Hazelett Strip Casting Corporation discloses in a number of
• permanent surface coatings are fusion bonded permanent matrix coatings covered with a dry, porous belt dressing.
• a gaseous layer such as helium, may also be
• An example of dry belt dressings for thermal insulative purposes are graphite, acetylene soot or other carbonaceous materials.
• diatomaceous silica may also be continuously or intermittently provided to coated belts
• thermal barrier such as soot
• Exemplary materials are dispersions of refractory materials to which carbon or graphite are added.
• US 3,557,866 shows an apparatus for applying a liquid thermal barrier and release agent to the bottom and the sidewalls of a peripheral groove in a casting
• the present invention may be summarized as providing a method for high
• the casting method involves moving two opposed casting surfaces, such as axially aligned twin rolls relative to one another.
• carbonaceous material is applied to the casting surfaces at a layer thickness of less than about 1.5 micron, and preferably less than about 0.4 micron.
• Molten metal is progressively solidified as the metal passes through the casting zone of the caster. Such solidification is completed prior to reducing the gauge of the solidified product at
• this invention relates to the uniform
• a high rolling force may negate the insulative effect of the thin, uniform carbonaceous layer while retaining the parting agent benefits and thereby
• An objective of this invention is to provide an improved roll casting
• Another advantage of this invention is to provide a roll casting process that permits a significant increase in the speed of the roll caster.
• An advantage of this invention is that the compressive condition peculiar
• Another advantage of this invention is that water, or other liquid agents are not required to deliver the carbonaceous material to the casting surface. This may improve roll shell life since the roll shell may not thermally fatigue as fast.
• a further advantage of this invention is that sheet may be cast at relatively high casting speeds which exhibits a more uniform surface texture and appearance.
• Figure 1 is a sketch of a typical arrangement for a horizontal roll casting operation from a melting furnace through a roll caster to a coiler for finished product.
• Figure 2 is an enlarged cross-sectional view taken about the centeriine of
• FIG. 3 is a view of an exemplary apparatus which can be used to deposit a carbonaceous layer of material onto the exterior surface of a rotating casting
• FIGS 4, 5, 6 and 7 illustrate altemative apparatus that could be used to
• Figure 8 is a photomicrograph of a layer of fine soot applied onto a
• Figure 9 is another photomicrograph of a layer of fine soot applied onto a
• Figure 10 is a photomicrograph of a layer of colloidal graphite, of the prior
• Figure 11 is a photomicrograph of the fine soot layer of Figure 8 shown at
• Figure 1 illustrates a typical arrangement for a horizontal roll caster.
• metal is melted in a furnace 2.
• the molten metal may be alloyed,
• the molten metal is
• cast strip material 12 which is typically coiled on a coiler 14 as finished product for
• a strip guide and shear unit 15, as shown, may be used to guide the
• a controller 9 monitors and
• inventions may be applicable to vertical roll casting and other casting processes where progressive solidification followed by a gauge reduction of the hot, solidified material
• Figure 2 illustrates the casting zone Z of a roll caster. As shown, the
• molten metal 16 is fed to the roll bite. It is important that the molten metal temperature
• the molten metal begins to solidify at the initial point of contact 18 with the upper roll 10 and simultaneously at the initial point of contact 20 with the lower roll 8.
• the casting zone Z shown in Figure 2 is typically less than about 100 mm
• the casting zone Z is characterized by three distinct areas.
• the first area A1 is where solidification begins but the majority of the metal is in the molten state. Thermal efficiency in this area is high.
• the second area A2 is where the internal molten metal has not yet solidified but is not in the molten state. This area is commonly known as the mushy zone 21. Thermal conductivity in this mushy zone is typically poor, because the metal begins to solidify and contracts away from its contact with the roll surface.
• the prior practice of using water or other agents to carry a surface agent, such as graphite, to the roll results in some liquid being present in this zone.
• the evaporation of the liquid may create a gaseous barrier between the metal and the roll further insulating them and decreasing the thermal efficiency of the cooling process.
• the third area A3 begins where the metal is solidified and ends at the centeriine of the rolls. Thermal efficiency in this third area is also high.
• the present invention eliminates the need to identify a balance between
• Soot particles of the present invention are typically of a size less than about 0.1 micron.
• Figure 10 illustrates soot particles at 10,000 magnification
• Soot can be applied in a very thin layer, typically less than
• the fine carbonaceous material covers
• the thickness of the soot layer is uniform.
• the thickness of the soot layer is uniform.
• layer is substantially the same thickness across the roll onto which metal is to be cast.
• Figure 10 shows that colloidal graphite of the prior art does not have a fine particle size, is not applied in a
• thin layer does not substantially cover the entire surface, and is not uniformly applied
• Figure 10 shows bare spots where molten aluminum would come into direct contact with the bare steel of the roll surface, forming an aluminum-iron
• propane and natural gas may also be burned in
• soot may
• the powder can be generated as a fine powder and the powder can be applied to the roll surface such
• the tip 24 of an acetylene torch 26 may be directed
• the soot layer 32 must be sufficiently thin, such as less than about 1.5 micron, to avoid
• soot applicator or applicators relative to the casting surface in a substantially uniform fashion.
• Figure 4 shows an alternative embodiment in which a number of
• acetylene torches may be mounted laterally across the width of a casting roll. Care must be taken to assure that the carbonaceous material is deposited substantially across the entire surface of the moving drum. Therefore, spacing of the torches is
• FIGS. 5 and 6 illustrate an altemative embodiment in which a single
• acetylene torch is driven across the face of the rotating drum to provide a uniform, thin
• Figure 6 shows a drive
• Figure 7 shows another alternative embodiment for burning a gas to
• the perforations should be sized, located and
• the burner could be stationary or it could oscillate alone or in combination with other burners to accomplish the carbonaceous layering or
• a roll caster was operated to cast alloy 1145 to an as-cast gauge of about 5 mm, with a thick, nonuniform colloidal graphite layer, and then the same alloy was cast to the same gauge using a thin, uniform layer of soot.
• the following operating parameters and measurements were obtained:
• Carbonaceous Laver type of material colloidal graphite soot thickness varies 0-2 micron 0.4 micron uniformity non-uniform very uniform particle size varies up to about 4 uniform of about 0.1 micron micron structure crystalline amorphous
• increased roll shell life may be due to the fact that the roll shell surface is not being cooled by an agent, such as water, used to carry other surface agents to the roll
• soot may be applied at various densities.
• TGA thermal gravometric analysis
• the present invention permits roll casting speed to be increased.
• the roll caster of this invention hot rolls the solidified strip as the strip passes through the roll bite.
• Such hot reduction is at least 10%, and possibly 50%.
• the heat encountered in such a hot rolling operation has the effect of
• Substantially complete burning assures that the carbonaceous material does not leave an unsightly, dirty residue on the strip surface. Most users of the strip material prefer, primarily for cosmetic reasons, that the strip material be substantially free of such residue.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=4061772

Family Applications (1)

Country Status (7)

Cited By (3)

Families Citing this family (2)

Citations (4)

Family Cites Families (10)

• 1995
  • 1995-06-16 BR BR9502834A patent/BR9502834A/pt not_active IP Right Cessation
• 1996
  • 1996-06-14 JP JP09503348A patent/JP3085985B2/ja not_active Expired - Lifetime
  • 1996-06-14 WO PCT/US1996/010319 patent/WO1997000147A1/en not_active Application Discontinuation
  • 1996-06-14 AU AU61768/96A patent/AU6176896A/en not_active Abandoned
  • 1996-06-14 EP EP96919420A patent/EP0850115A4/en not_active Withdrawn
  • 1996-06-14 KR KR1019970709432A patent/KR100360176B1/ko active IP Right Grant
  • 1996-06-18 AR ARP960103191A patent/AR002508A1/es active IP Right Grant

Patent Citations (4)

Non-Patent Citations (1)

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