Nozzle for continuous slab casting

Information

  • Patent Grant
  • 6173755
  • Patent Number
    6,173,755
  • Date Filed
    Thursday, May 23, 1996
    28 years ago
  • Date Issued
    Tuesday, January 16, 2001
    23 years ago
Abstract
An improved casting nozzle for continuous slab casting machines is provided. The nozzle includes a sloped surface which reduces molten metal turbulence during the casting process. The nozzle also includes a resilient, thermal insulation layer which prevents undesired backflow and premature solidification of the molten metal near the nozzle tip. The nozzle may also include a friction reducing layer which prevents excessive wear or fracture of the nozzle as it contacts the casting mold. The casting nozzle is suitable for use with both horizontal and vertical continuous casting machines, and may be used with various types of casting molds including continuous belt or caterpillar molds, and stationary molds. The improved nozzle may be used to cast various metals such as aluminum and aluminum alloys.
Description




BACKGROUND OF THE INVENTION




The present invention relates to continuous slab casting of metals, and more particularly to a molten metal delivery nozzle for continuous slab casting which reduces turbulence and premature freezing of the molten metal, thereby improving the surface quality of the resultant casting.




Continuous casting techniques have been used to form slabs or strips of various metals such as aluminum, copper, zinc and steel. Several types of continuous casting machines are known. For example, one type of casting machine comprises an opposing pair of moving continuous belts which form a mold into which molten metal is introduced. U.S. Pat. Nos. 4,602,668, 4,785,873 and 4,798,315 disclose such continuous belt casting machines.




Continuous slab casting machines have also incorporated opposing caterpillar-type molds in place of continuous belts, as shown in U.S. Pat. Nos. 3,774,670, 4,290,477, 4,485,835 and 4,619,309.




Prior art slab casting machines have also incorporated a single flat surface onto which the molten metal is cast. U.S. Pat. No. 4,721,152 discloses one such single-belt continuous casting machine.




A major disadvantage of prior art continuous slab or strip casting machines is the production of castings having poor surface quality due to such factors as molten metal turbulence and premature solidification near the nozzle tip. These problems are thought to result from meniscus instability of the molten metal at the nozzle discharge area. Attempts have been made to reduce meniscus instability by methods such as shrouding the molten metal with inert gas as it exits the nozzle. However, the control of meniscus instability by such methods is difficult and has not resulted in a consistent production of castings having optimum surface quality.




The present invention has been developed in view of the foregoing and to overcome other deficiencies of the prior art.




SUMMARY OF THE INVENTION




The present invention provides an improved molten delivery nozzle for continuous slab or strip casting which reduces turbulence, backflow and premature freezing of the molten metal, thereby producing cast slabs having highly superior surface quality. The improved nozzle promotes meniscus stability during the casting operation which reduces porosity and improves the surface quality of the cast products.




An object of the present invention is to provide an improved molten delivery nozzle for use in slab or strip casters.




Another object of the present invention is to provide an apparatus for casting a metal slab or strip including a casting mold and a molten delivery nozzle slidingly engaged with the casting mold for delivering molten metal to the mold. The nozzle includes at least one resilient, thermal insulation layer which provides a seal between the casting mold and nozzle, and prevents premature solidification of molten metal near the nozzle tip. The casting mold may comprise a continuous belt or caterpillar mold, or may comprise a stationary mold.




Another object of the present invention is to provide a molten metal delivery nozzle having a sloped configuration which reduces molten metal turbulence during the casting operation.




Another object of the present invention is to provide a method of casting a metal slab or strip including the use of a casting mold and a molten metal delivery nozzle in sliding engagement with the mold. Molten metal is delivered through the nozzle into the mold where it solidifies to form a slab or strip. During the casting process, the meniscus of the molten metal is controlled in order to improve surface quality of the resultant slab. The nozzle is configured such that it reduces turbulence, backflow and premature solidification of the molten metal at the nozzle tip. The method may include the use of horizontal or vertical continuous casting machines.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a partially schematic cross-sectional side view showing a continuous casting apparatus in accordance with an embodiment of the present invention.





FIG. 2

is a perspective view showing a molten metal delivery container including a casting nozzle in accordance with an embodiment of the present invention.





FIG. 3

is an exploded view of the casting container shown in FIG.


2


.





FIG. 4

is an exploded view of a molten metal delivery container including a casting nozzle in accordance with a preferred embodiment of the present invention.





FIG. 5

is a cross-sectional side view showing a portion of a casting nozzle in accordance with a preferred embodiment of the present invention.





FIG. 6

is a cross-sectional side view showing a portion of a casting nozzle in accordance with an alternative embodiment of the present invention.





FIG. 7

is a cross-sectional side view showing a portion of a casting nozzle in accordance with another embodiment of the present invention.





FIG. 8

is a front view showing a casting nozzle and casting belt in accordance with an embodiment of the present invention.





FIG. 9

is a partially schematic cross-sectional side view showing a continuous casting apparatus in accordance with another embodiment of the present invention.





FIG. 10

is a photograph of the surface of a cast aluminum slab produced in accordance with an apparatus and method of the present invention.




FIGS.


11


-


14


are comparative photographs of cast aluminum slabs showing the poor surface quality thereof.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring to the drawings, wherein like reference numerals represent like elements throughout the several figures,

FIG. 1

is a partially schematic cross-sectional side view showing a continuous caster


10


in accordance with the present invention. The caster includes a molten metal feed container


11


disposed on a casting belt


12


. The container


11


comprises a front wall


15


, a back wall


16


and a side wall


17


. Although not shown in the cross-sectional view of

FIG. 1

, the container


11


comprises another side wall


18


, as shown in FIG.


2


. The container


11


also comprises a bottom nozzle


20


which, in the embodiment shown in

FIG. 1

, rests on the casting belt


12


. The right portion of the bottom nozzle


20


shown in

FIG. 1

comprises a sloped surface


21


disposed at an angle A measured from the vertical direction. The lower portion of the front wall


15


comprises an opening


22


. The sloped surface


21


and side wall opening


22


define a slit-like nozzle opening for the container


11


. As more fully described below, the angle A of the sloped surface


21


is selected in order to reduce turbulence and improve meniscus stability during the casting operation. While the sloped surface shown in

FIG. 1

is substantially flat or planar, the sloped surface can alternatively be curved. For example, the sloped surface may be have a concave or convex configuration.




During casting, the casting belt


12


moves in the direction B shown in FIG.


1


. Alternatively, during the casting operation, the belt


12


may be held stationary while the container


11


is moved toward the left in FIG.


1


. The slab caster may include an end dam


31


to provide containment for the molten metal during the casting operation. In addition, the caster may include a cover made of graphite


32


which serves as an insulator to prevent heat transfer towards the free surface. During the casting operation, cooling fluid


33


may be directed toward the casting belt


12


in the area of the nozzle tip as shown in

FIG. 1

in order to extract heat from the casting and aid in the solidification of the slab.




Molten metal


40


is introduced into the container


11


where it is preferably maintained at a level sufficient to supply a sufficient pressure head during casting. While it is preferred to carry out the casting operation at atmospheric pressure, it is also possible to supply the molten metal through a pressurized container. After it is introduced into the container


11


, the molten metal


40


flows generally in the vertical direction Y toward the bottom of the container, where it is then directed in the horizontal direction X toward the sloped surface


21


of the nozzle


20


. As it exits the container


11


through the sloped nozzle opening


21


, the molten metal contacts the casting belt


12


which serves as a mold for the cast metal. With the aid of the cooling fluid


33


, the metal solidifies from the molten state


41


to the solid state


42


to form a slab.




The sloped surface


21


minimizes the cascade height in the area of the nozzle tip, and promotes laminar flow of the molten metal as it exits the container


11


into the casting mold. The cascade height, which is defined by the distance from the edge of the nozzle tip to the mold, is preferably less than 0.1 inch and more preferably less than 0.0625 inch. The angle A of the sloped surface


21


may range from 5 to 85 degrees, with angles of 15 to 80 degrees being preferred. The angle A is selected such that turbulence of the molten metal is reduced in the nozzle tip area.




The front, back and side walls


15


,


16


,


17


and


18


of the container


11


are made from any suitable material, preferably a refractory material capable of withstanding the elevated temperature and reactive nature of the molten metal to be cast. Calcium silicate board sold under the name PYROTEK B-3 is suitable. The bottom nozzle


20


of the container


11


is likewise made of a material capable of withstanding the elevated temperature and corrosive nature of the particular molten metal. Furthermore, the bottom nozzle


20


, which is in sliding engagement with the belt


12


during the casting operation, comprises means for sealing the container


11


against the casting belt


12


. By providing a seal between the container


11


and the casting belt


12


, the bottom nozzle


20


prevents undesired backflow of molten metal, which improves the surface quality of the resultant cast product. In addition, the bottom nozzle


20


comprises a material having low thermal transfer characteristics, which acts as an insulator to reduce or eliminate premature solidification of the molten metal during casting. Thus, in addition to containing the molten metal, the bottom nozzle


20


also functions as a molten metal seal and as a thermal barrier. These features, in combination with the sloped surface


21


of the nozzle, provide a molten metal delivery nozzle which reduces turbulence, backflow and premature solidification of the molten metal near the nozzle tip, which improves slab surface quality. The nozzle of the present invention controls the meniscus of the molten metal at the nozzle discharge area, thereby improving the surface quality of the cast slab. The meniscus is controlled to provide the desired angle of contact between the molten metal and the mold at the tip area.




In a preferred embodiment, the bottom nozzle


20


may also be provided with a friction reducing surface in order to decrease the friction generated at the interface of the container


11


and the casting belt


12


, and to protect the bottom of the container from excessive wear or fracture.





FIG. 2

is a perspective view of a molten metal feed container


11


in accordance with an embodiment of the present invention. The container


11


comprises front wall


15


, back wall


16


and side walls


17


and


18


. When fully assembled, the front wall slides into retaining grooves


19


disposed in the side walls


17


and


18


. As shown more clearly in

FIGS. 3 and 4

, the front wall


15


includes stepped edges which fit within the retaining grooves


19


of the side walls. The retaining grooves


19


terminate a short distance from the bottom nozzle


20


of the container


11


. When the front wall is installed in the grooves, a small slit-like opening is provided along the lower front edge of the container adjacent to the sloped surface


21


. In accordance with the present invention, the height of the opening may be adjusted to control the rate of molten metal flow through the nozzle. The height of the opening is preferably set at a level which facilitates laminar flow of the molten metal as it exits the container through the nozzle.





FIGS. 3 and 4

are exploded views of alternate embodiments of the present invention. In each of these embodiments, the container includes front and back walls


15


and


16


, as well as side walls


17


and


18


. The side walls


17


and


18


include retaining grooves


19


for the front wall. In the embodiment of

FIG. 3

, the bottom nozzle


20


and the sloped surface


21


are provided as a unitary piece. In contrast, the bottom portion shown in

FIG. 4

comprises a nozzle tip portion


24


including the sloped surface


21


and a separate body portion


25


. The use of separate tip and body portions as shown in

FIG. 4

has the advantage that it can be replaced easily if the tip becomes worn, or if a different tip slope is desired.




FIGS.


5


-


7


show cross-sectional side views of bottom nozzles


20


in accordance with various embodiments of the present invention. In

FIG. 5

, the bottom nozzle


20


comprises a tip portion


24


and a body portion


25


similar to that shown in

FIG. 4

made of refractory material such as PYROTEK B-3. In addition, the bottom surface of the tip


24


shown in

FIG. 5

is provided with a layer of resilient insulating material


26


which possesses elastic as well as thermal insulating properties. A particularly preferred material for the layer


26


is non-respirable fiber paper comprising fibrous glass and a latex binder which is sold under the name Q-BLOC. The bottom nozzle


20


shown in

FIG. 5

also includes a friction reducing layer


27


which covers both the resilient insulating layer


26


of the tip


24


and the bottom surface of the body portion


25


. During the casting operation, the friction reducing layer


27


contacts the casting belt to reduce friction between the container


11


and the casting belt


12


, and to prevent excessive wear of the container. Graphite is a preferred material for the friction reducing layer


27


. In particular, graphite in the form of flexible foil having a thickness of 0.01 inch sold under the name GRAFOIL is a preferred material for the friction reducing layer


27


.




As shown in

FIG. 5

, the tip


24


includes a sloped surface


21


disposed at an angle A as described above. The various components shown in

FIG. 5

may be assembled in any suitable manner, with the use of high temperature-resistant adhesives being preferred. For example, core paste sold under the name ZIP STICK may be used as an adhesive to secure the components together. The dimensions of the components shown in

FIG. 5

may be varied to achieve the desired results. For example, the thickness of the back portion


25


and tip portion


24


may preferably range from 0.2 to 2 inch, and more preferably from 0.25 to 1.0 inch. Where PYROTEK B-3 is used as the back and tip portions, a thickness of 0.5 inch is suitable. The thickness of the resilient insulating layer


26


is typically less than about 0.3 inch, preferably ranging from about 0.05 to 0.25 inch, and more preferably from about 0.1 to 0.2 inch. Where Q-BLOC is used as the resilient insulating layer


26


, a thickness of 0.125 inch is suitable. The friction reducing layer


27


is preferably provided as a thin layer ranging from about 0.001 to 0.1 inch, and more preferably from about 0.005 to 0.02 inch. Where GRAFOIL is used as the friction reducing layer


27


, a thickness of 0.01 inch is suitable.





FIG. 6

illustrates a bottom nozzle


20


in accordance with another embodiment of the present invention. In this embodiment, the bottom nozzle


20


comprises a unitary piece of refractory material similar to the configuration shown in

FIG. 3. A

resilient insulating layer


26


is attached to the entire lower surface of the bottom nozzle


20


. In this embodiment, the resilient insulating layer


26


comprises a material that is elastic and thermally insulating, as well as sufficiently durable to withstand contact with the casting belt during the casting operation. The resilient insulating layer


26


shown in

FIG. 6

thus functions as a sealing layer to prevent molten metal backflow, a thermal insulator to prevent premature solidification of molten metal at the nozzle tip, and a durable, friction reducing layer.




In the embodiment shown in

FIG. 7

, the bottom nozzle


20


comprises a unitary piece of refractory material similar to the embodiments of

FIGS. 3 and 6

. However, the bottom nozzle


20


comprises a resilient insulating layer


26


disposed on the entire lower surface of the bottom nozzle


20


, and a friction reducing layer


27


attached to the resilient layer


26


. While the use of such a resilient insulating layer


26


provides a relatively flat surface for contacting the casting belt, the use of such a large layer of resilient insulating material may result in increased cost in comparison with the partial layer shown in FIG.


5


.





FIG. 8

is a front view of a nozzle


20


similar to that shown in

FIGS. 5 and 7

disposed on a casting belt


12


. The nozzle includes a sloped surface


21


as described previously, as well as a resilient insulating layer


26


and friction reducing layer


27


. The area of contact between the casting belt


12


and friction reducing layer


27


is sealed across the entire width of the nozzle


20


through the elastic action of the resilient insulating layer


26


.





FIG. 9

is a partially schematic cross-sectional side view of a vertical continuous casting apparatus in accordance with an alternative embodiment of the present invention. In this embodiment, the slab caster


110


comprises a molten metal tundish


111


having side walls


115


,


116


and


117


. The feed container


111


also comprises a fourth side wall which is not shown in the cross-sectional view of FIG.


9


. The slab caster


110


includes a pair of opposing continuous casting belts


112


which form a continuous casting mold. The bottom portion of the container


111


tapers into a slot-shaped nozzle


120


which is inserted between the casting belts


112


. The nozzle


120


comprises opposing sloped surfaces


121


which reduce turbulence during the casting operation, as more fully described below. The container


111


and the nozzle


120


are preferably made of refractory material such as PYROTEK B-3. The nozzle


120


comprises a pair of resilient insulating layers


126


disposed on the exterior surfaces of the refractory material. In addition, friction reducing layers


127


are attached to the resilient insulating layers


126


. The layers


126


and


127


may be assembled together by any suitable means such as adhesives which are resistant to the high temperatures encountered during casting operations.




The continuous casting belts


112


are driven by a series of rolls


134


. During casting, cooling fluid


133


is directed against the casting belts


112


in order to facilitate the solidification of the molten metal. Molten metal


140


introduced into the container


111


flows through the nozzle


120


into the casting mold formed by the continuous belts


112


. Once introduced into the casting mold, the molten metal


141


solidifies to form a solid slab


142


which is removed from the casting mold in the direction C shown in FIG.


9


.




The nozzle


120


shown in

FIG. 9

comprises left and right portions, each of which has a sloped surface


121


, a resilient insulating layer


126


and a friction reducing layer


127


. Each of these portions may be configured in a manner similar to that shown in FIGS.


5


-


7


. Thus, the sloped surface


121


is disposed at an angle A measured from the horizontal direction in

FIG. 9

, which corresponds with the angle A of the sloped surfaces


21


previously described: Each side of the nozzle


120


shown in

FIG. 9

may comprise a tip portion having the resilient insulating layer disposed thereon, similar to the embodiment of FIG.


5


. Furthermore, each side of the nozzle


120


may comprise a single layer of resilient insulating material which also serves as a wear-resistant friction reducing layer, similar to the embodiment shown in FIG.


6


. Alternatively, each side of the nozzle


120


may be made from a single piece of refractory material having a resilient insulating layer and a friction reducing layer covering its entire surface in a manner similar to that shown in FIG.


7


.




In the embodiment of

FIG. 9

, the resilient insulating layers


126


seal the nozzle


120


against the casting belts


112


, thereby preventing unwanted backflow of molten metal. In addition, the layers


126


provide thermal insulation for the molten metal as it exits the nozzle


120


, thereby preventing premature solidification near the nozzle tip that would otherwise occur due to the action of the cooling fluid


133


. The friction reducing layers


127


serve to reduce the friction created between the nozzle


120


and the continuous belts


112


, and to prevent excessive wear or fracture of the resilient insulating layers


126


.




The vertical continuous casting apparatus shown in

FIG. 9

has the advantage that the molten metal


141


entering the casting mold acts through the force of gravity to fill voids in the casting caused by solidification shrinking. The use of the resilient insulating layer


126


to tightly seal the nozzle


120


against the casting belts


112


advantageously prevents backflow and promotes meniscus stability of the molten metal during the casting operation. The sloped surfaces


121


promote laminar flow of the molten metal as it enters the mold cavity from the nozzle


120


. By reducing the turbulence of the molten metal, the nozzle


120


controls meniscus instability during casting. Superior castings are thereby achieved having excellent surface quality.




While a single-belt horizontal slab caster is shown in

FIG. 1 and a

dual-belt vertical slab caster is shown in

FIG. 9

, the improved casting nozzle of the present invention is suitable for use in conjunction with other types of continuous casters. For example, the nozzle may be used with dual-belt horizontal slab casters and the like or with roll casters.




The following examples illustrate various aspects of the present invention and are not intended to limit the scope thereof.




EXAMPLE 1




A casting apparatus is provided comprising a stationary horizontal surface with two parallel side dams and an end dam defining a horizontal slab casting mold. The horizontal surface is made of steel sheet while the side and end dams are made of calcium silicate refractory material. The parallel side dams are placed 10 inches apart to define a 10 inch wide casting mold. A molten metal feed container comprising front, back and side walls is assembled from separate parts as shown in FIG.


4


. The walls extend to a height of approximately 5.5 inches. The container comprises a bottom portion similar to that shown in

FIGS. 1 and 4

having a width of approximately 5.625 inch, a length of 7.875 inch and a thickness of 0.5 inch. The bottom portion is assembled from two pieces of refractory material comprising tip and back portions similar to that shown in FIG.


5


. The tip includes a sloped surface disposed at an angle A of 75 degrees measured from the vertical direction as shown in

FIGS. 1 and 5

. The bottom portion, as well as the front, back and side walls, are made of PYROTEK B-3 refractory material. A 0.125 inch thick sheet of Q-BLOC resilient insulating material is glued to the underside of the nozzle tip using ZIP STICK core paste. A 0.01 inch thick sheet of GRAFOIL friction reducing material is glued to the underside of the Q-BLOC, and is also glued to the exposed portion of the PYROTEK B-3 refractory material as shown in

FIG. 5

using ZIP STICK core paste. The side, back and bottom sections of the feed container are glued together with ZIP STICK core paste, and the front wall of the container is slid into the retaining grooves in the side walls. The container is then placed on the horizontal surface of the casting mold between the parallel side dams and abutting the end dam. Molten aluminum having a composition of 1.2 Mn, 1.0 Mg, balance Al (Aluminum Association 3004) at a temperature of between 1260 and 1360° F. is poured into the feed container to a height of approximately 3.5 inches. The feed container is then slid at a constant rate of approximately 3.5 inches per second along the horizontal surface of the casting mold. During the casting operation, the lower surface of the casting mold is cooled by a series of water jets. The resulting aluminum slab is about 0.5 inch thick. Upon removal from the mold, the surface of the slab formed adjacent to the horizontal mold surface is examined and is found to be extremely smooth with minimal liquation and other defects, such as laps, ripples and coldshuts. The surface of the resultant slab is shown in the photograph of FIG.


10


.




EXAMPLE 2




Example 1 is repeated for aluminum alloys having the following compositions: AA 5182 (4.5 Mg, 0.35 Mn, balance Al); and AA 5052 (2.5 Mg, 0.25 Cr, balance Al). In each case, the surface of the casting is similar to that shown in

FIG. 10

with minimal liquation and other surface defects, such as laps, ripples and coldshuts.




EXAMPLE 3




Example 1 is repeated except the bottom nozzle portion of the feed container is not provided with a sloped surface but is rather provided with a vertical opening (angle A of 0 degrees). The resultant casting exhibits poor surface quality due to the large cascade height and the resulting local turbulence or circulation of the molten aluminum as it exits the feed container. The poor surface quality of the resultant slab is shown in the photograph of FIG.


11


.




EXAMPLE 4




Example 1 is repeated except no layer of Q-BLOC resilient insulating material is disposed underneath the nozzle tip and no layer of GRAFOIL is used. The surface quality of the resultant slab is poor due to backflow and premature freezing of the molten metal near the nozzle tip. The poor surface quality of the resultant slab is shown in the photograph of FIG.


12


.




EXAMPLE 5




Example 1 is repeated except no layer of GRAFOIL friction reducing material is attached to the underside of the Q-BLOC or to the back portion of the feed box. The resultant slab has relatively poor surface quality which includes rough areas and drag lines created by pieces of the Q-BLOC layer which are dislodged during the casting operation. The poor surface quality of the resultant slab is shown in the photograph of FIG.


13


.




EXAMPLE 6




Example 1 is repeated except no layer of Q-BLOC resilient insulating material is used, and the GRAFOIL friction reducing layer is applied directly to the entire underside of the feed box. The resultant casting has poor surface quality due to premature solidification of the molten metal near the nozzle tip. The poor surface quality of the resultant slab is shown in the photograph of FIG.


14


.




While particular embodiments of the invention have been described herein, for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details may be made without departing from the invention as set forth in the appended claims.



Claims
  • 1. Apparatus for casting a metal product comprising:(a) a casting mold; and (b) a molten metal delivery nozzle for delivering molten metal to the mold, the nozzle comprising: (i) at least one interior surface for containing the molten metal; (ii) at least one substantially planar exterior surface in contact with the casting mold; (iii) a sloped surface extending from the interior surface toward the exterior surface defining a nozzle tip for reducing molten metal turbulence as the metal exits the nozzle; (iv) means for substantially sealing the nozzle against the mold and for thermally insulating the nozzle comprising a layer of resilient, thermally insulating material disposed on the nozzle; and (v) a layer of friction reducing material disposed on the layer of resilient, thermally insulating material.
  • 2. The apparatus of claim 1, wherein the molten metal delivery nozzle is slidingly engaged with the casting mold.
  • 3. The apparatus of claim 1, wherein the sloped surface is substantially planar.
  • 4. The apparatus of claim 1, wherein the casting mold comprises at least one moving belt.
  • 5. The apparatus of claim 1, wherein the casting mold comprises means for cooling at least a portion of the mold adjacent an engaging surface between the mold and the nozzle.
  • 6. The apparatus of claim 1, wherein the layer of resilient, thermally insulating material has a thickness of less than about 0.3 inch.
  • 7. The apparatus of claim 1, wherein the layer of resilient, thermally insulating material has a thickness of from about 0.05 to 0.25 inch.
  • 8. The apparatus of claim 1, wherein the resilient, thermally insulating material includes fibrous glass and a latex binder.
  • 9. The apparatus of claim 1, wherein the layer of resilient, thermally insulating material comprises a substantially planar exterior surface which is in contact with the casting mold.
  • 10. The apparatus of claim 1, wherein the layer of friction reducing material comprises graphite foil.
  • 11. The apparatus of claim 10, wherein the graphite foil has a thickness less than about 0.1 inch.
  • 12. The apparatus of claim 10, wherein the graphite foil has a thickness of from about 0.005 to 0.02 inch.
US Referenced Citations (13)
Number Name Date Kind
2348178 Merle May 1944
3774670 Gyöngyös Nov 1973
4290477 Huber et al. Sep 1981
4485835 Huber et al. Dec 1984
4602668 Bolliger Jul 1986
4619309 Huber et al. Oct 1986
4649984 Bedell et al. Mar 1987
4721152 Reichelt et al. Jan 1988
4785873 Lauener Nov 1988
4791979 Liebermann Dec 1988
4798315 Lauener Jan 1989
4928748 Guthrie et al. May 1990
5660757 Smith Aug 1997
Foreign Referenced Citations (1)
Number Date Country
60-21169 Feb 1985 JP