COVER FOR CASTING VESSELS IN CONTINUOUS CASTING MACHINES
United States Patent 3814408
A cover for casting vessels such as tundishes used in connection with continuous casting machines comprises a body formed of a base metal such as cast iron which is provided with reinforcing members extending therethrough formed of a metal such as steel having a higher tensile strength than said base metal whereby the resistance of said cover to warping is improved.
US Patent References:
Ingot mold
Jones - January 1935 - 1989096
Ingot cap
Belding - February 1940 - 2190392
Method for fluxing molten light metals prior to the continuous casting thereof
Peterson et al. - January 1958 - 2821472
Lining of the internal surface of a blast furnace
Zherebin et al. - April 1968 - 3379427
CONTINUOUS CASTING APPARATUS WITH TILTABLE INTERMEDIATE LADLE
Bick et al. - March 1969 - 3433288
Ingot mold
Jones - January 1935 - 1989096
Ingot cap
Belding - February 1940 - 2190392
Method for fluxing molten light metals prior to the continuous casting thereof
Peterson et al. - January 1958 - 2821472
Lining of the internal surface of a blast furnace
Zherebin et al. - April 1968 - 3379427
CONTINUOUS CASTING APPARATUS WITH TILTABLE INTERMEDIATE LADLE
Bick et al. - March 1969 - 3433288
Application Number:
05/208717
Publication Date:
06/04/1974
Filing Date:
12/16/1971
View Patent Images:
Export Citation:
Assignee:
Concast AG (Zurich, CH)
Primary Class:
Other Classes:
249/204, 266/275, 164/411, 164/348, 220/645
International Classes:
B22D11/10; B22D41/00; F27D1/10
Field of Search:
266/39,40,43,1R 249/120,135,199,202,204 164/281,283,335,337,348,411,412 220/71,24R
Other References:
Publication: The Iron Age; December 9, 1948, pages 93-96..
Primary Examiner:
Dost, Gerald A.
Attorney, Agent or Firm:
Sandoe, Hopgood & Calimafde
Claims:
I claim as my invention
1. A cover for use with casting vessels of continuous casting machines comprising a body of base metal, said base metal being cast iron, and reinforcing members encasted in said base metal and extending therethrough, said members being formed of steel having a tensile strength greater than that of said base metal, said reinforcing members projecting beyond said body and serving as carrying pins for handling the cover.
2. A cover for use with casting vessels of continuous casting machines comprising a body of base metal, said base metal being cast iron, and reinforcing members encasted in said base metal and extending therethrough, said members being formed of steel having a tensile strength greater than that of said base metal, said reinforcing members having passages extending therethrough for the circulation of coolant.
3. A cover for use with casting vessels of continuous casting machines comprising a body of base metal, said base metal being cast iron, and reinforcing members encasted in said base metal and extending therethrough, said members being formed of steel having a tensile strength greater than that of said base metal, said body being provided with an aperture extending therethrough and having a reinforcing member encircling said aperture.
1. A cover for use with casting vessels of continuous casting machines comprising a body of base metal, said base metal being cast iron, and reinforcing members encasted in said base metal and extending therethrough, said members being formed of steel having a tensile strength greater than that of said base metal, said reinforcing members projecting beyond said body and serving as carrying pins for handling the cover.
2. A cover for use with casting vessels of continuous casting machines comprising a body of base metal, said base metal being cast iron, and reinforcing members encasted in said base metal and extending therethrough, said members being formed of steel having a tensile strength greater than that of said base metal, said reinforcing members having passages extending therethrough for the circulation of coolant.
3. A cover for use with casting vessels of continuous casting machines comprising a body of base metal, said base metal being cast iron, and reinforcing members encasted in said base metal and extending therethrough, said members being formed of steel having a tensile strength greater than that of said base metal, said body being provided with an aperture extending therethrough and having a reinforcing member encircling said aperture.
Description:
The present invention relates to a cover made of a metal casting for casting vessels in continuous casting machines. Such casting vessels are principally used as tundishes, distributing launders, holding vessels or the like.
Conventional covers consist of refractory material or are lined with it. Due to the mechanical and thermal stresses to which such covers are exposed they do not last very long. The destruction of the refractory brickwork necessitates time-consuming repairs, apart from the fact that any refractory material that drops off may cause trouble in the casting process itself. It has therefore been proposed to make such covers of metal, more particularly of steel plate, non-scaling and/or high temperature steel, copper or cast iron. However, this known type of metal cover has the drawback of warping easily under high thermal stress, or that for instance cast iron covers form cracks which may cause the cover to fracture, and therefore reduce its usefulness and its operating safety.
It is therefore an object of the present invention to prolong the durability and therefore the useful life of metal covers and to avoid the undesirable consequences of cracks that may have formed for instance when the cover undergoes thermal stress, and also to reduce the tendency of the cover to warp.
According to the present invention this is achieved by encasting in the metal of the cover reinforcing members consisting of a metal of superior tensile strength.
Should cracks form in the base metal when the cover has been repeatedly used, then these cracks are blocked by the encasted higher tensile strength members and the cracks are thereby prevented from spreading. The formation of a continuous crack, which would otherwise cause the cover to fracture, is thus prevented. Moreover, the tendency of the cover to warp as a result of strain due to thermal radiation is also reduced. A cover of the proposed construction is capable of lasting for more than 1,000 castings, compared with conventional covers consisting exclusively of cast metal, which do not last for more than about 100 castings. This illustrates the great economic importance of the present invention. Besides these advantages, dangerous interruptions of the casting process which are caused by fragments of the cast cover falling into the metal pool no longer occur.
In a preferred form of construction the base metal for forming the cover body may be cast iron, with steel being used for the reinforcing members. As known, cast iron is very brittle, whereas steel has a tensile strength and toughness greatly superior to cast iron. Cracks, which "run" fairly easily in cast iron, are intercepted at the interface between the cast iron and the steel reinforcing members. The differences in the expansion properties between cast iron and steel promote thermal stability, i.e., they assist in keeping the cover in shape. The combination of cast iron and steel as materials for the cover respectively the cover reinforcing members therefore ensures prolonged durability, operating safety and a low tendency to distort.
Apart from the above combination it would alternatively be possible to embed high tensile strength rolled steel sections in cast steel covers. This would also prevent the formation of continuous cracks.
The cross section of the reinforcement is arbitrary and may be say round or square. However, better results can be expected from sections that generate major moments of resistance to flexure, such as girder sections. Concrete reinforcing steel may also be used. For the production of the covers the reinforcing members are simply placed in the casting mold and encast in the metal that forms the cover.
To facilitate the handling of such a cover the length and position of the embedded reinforcing members may be so chosen that the reinforcements project from the rim of the cover so that they can be used as brackets for transporting the covers, i.e., by a crane.
In yet another embodiment of the present invention the reinforcing members may be provided with bores for the passage therethrough of a coolant to cool the cover.
The cover is exposed to fluctuating temperatures, since during the casting process it is exposed from below to the radiant heat of the liquid steel contained in the casting vessel, while it will cool off when the casting vessel has been emptied of the liquid steel. This results in a temperature profile in the cover which varies with reference to time. The different degrees of expansion at different temperatures cause arching of the cover and the enforced bending leads to the appearance of the usual neutral bending line. In order to control the tendency of the cover to warp and to form cracks in an even more efficient way another useful feature of the invention consists in locating most of the reinforcing members in the zone above or below this neutral bending line, i.e., offset therefrom, so that the longitudinal axis of the reinforcing member does not coincide with the neutral bending line or plane of the cover. A particularly desirable effect is achieved if the coefficients of expansion of the base metal and of the reinforcing metal are different, so that strains will be generated by this difference which reduce the tendency to cracking and warping of the cover.
The location and number of the reinforcing members will principally depend upon the geometrical size and shape of the cover. For example, in a tundish an opening is provided for the supply from a ladle of the metal that is to be poured into the mold and possibly further openings are necessary for controlling the pouring rate of the liquid metal from the tundish into the molds with stopper rods. Since cracks often tend to connect with these openings, it is also preferred to provide reinforcing members around these openings.
Covers according to the present invention are schematically shown in the drawings in which:
FIG. 1 is a plan view of the cover of a tundish seen from above.
FIG. 2 is a plan view from above of a different embodiment of a tundish cover.
FIG. 3 is a vertical section of a casting vessel and cover and
FIG. 4 is a section taken on the line IV -- IV in FIG. 3.
FIG. 1 shows a tundish cover 1 of a three-strand billet casting machine. Encast in the cover 1, which consists of cast iron and is about 200 mm thick, are reinforcing members 2. These members consist of steel and have a square cross section, each side of the square being 45 mm long. An opening 3 in the cover serves for pouring steel from a ladle into the tundish. Openings 4 are provided for three stopper rods, not shown, which serve for controlling the flow of steel from the tundish into three molds. The length of the parallel reinforcing members 2 is such that they project from the edges of the cover 1 and that the projecting ends can be used as carrying pins 5 for handling the cover.
FIG. 2 shows another tundish cover 6, likewise made of cast iron. This cover contains reinforcing members 7 which are water-cooled tubes of steel. Cooling water can be circulated through the bores 8 in the members for cooling the cover. This cooling reduces the tendency of the cover to distort when it is exposed to the thermal radiation of the liquid metal which is contained in the casting vessel. The ends of the tubes projecting from the edge of the cover 6 are provided with flanges for connecting them to a cooling water circuit, not shown in the drawing. In the illustrated embodiment the liquid metal inlet opening 3 is also surrounded by such tubes which serve as reinforcing members.
FIGS. 3 and 4 illustrate a cover 9 which rests on a casting vessel 12 and contains reinforcing members 10. The thermal radiation emitted from below the cover by the metal bath 13 thermally stresses the cover 9 and thereby induces it to warp. However, distortion of the cover 9 is prevented by the particular position of the encast reinforcing member 10, since the larger part of the cross section of the member 10 is contained in the strained zone which is located above the neutral bending line 11, i.e. the horizontal center line of member 10 is offset in upward direction from the neutral bending line 11. Member 10 forms in this location, which is also colder, a particularly effective reinforcement.
Conventional covers consist of refractory material or are lined with it. Due to the mechanical and thermal stresses to which such covers are exposed they do not last very long. The destruction of the refractory brickwork necessitates time-consuming repairs, apart from the fact that any refractory material that drops off may cause trouble in the casting process itself. It has therefore been proposed to make such covers of metal, more particularly of steel plate, non-scaling and/or high temperature steel, copper or cast iron. However, this known type of metal cover has the drawback of warping easily under high thermal stress, or that for instance cast iron covers form cracks which may cause the cover to fracture, and therefore reduce its usefulness and its operating safety.
It is therefore an object of the present invention to prolong the durability and therefore the useful life of metal covers and to avoid the undesirable consequences of cracks that may have formed for instance when the cover undergoes thermal stress, and also to reduce the tendency of the cover to warp.
According to the present invention this is achieved by encasting in the metal of the cover reinforcing members consisting of a metal of superior tensile strength.
Should cracks form in the base metal when the cover has been repeatedly used, then these cracks are blocked by the encasted higher tensile strength members and the cracks are thereby prevented from spreading. The formation of a continuous crack, which would otherwise cause the cover to fracture, is thus prevented. Moreover, the tendency of the cover to warp as a result of strain due to thermal radiation is also reduced. A cover of the proposed construction is capable of lasting for more than 1,000 castings, compared with conventional covers consisting exclusively of cast metal, which do not last for more than about 100 castings. This illustrates the great economic importance of the present invention. Besides these advantages, dangerous interruptions of the casting process which are caused by fragments of the cast cover falling into the metal pool no longer occur.
In a preferred form of construction the base metal for forming the cover body may be cast iron, with steel being used for the reinforcing members. As known, cast iron is very brittle, whereas steel has a tensile strength and toughness greatly superior to cast iron. Cracks, which "run" fairly easily in cast iron, are intercepted at the interface between the cast iron and the steel reinforcing members. The differences in the expansion properties between cast iron and steel promote thermal stability, i.e., they assist in keeping the cover in shape. The combination of cast iron and steel as materials for the cover respectively the cover reinforcing members therefore ensures prolonged durability, operating safety and a low tendency to distort.
Apart from the above combination it would alternatively be possible to embed high tensile strength rolled steel sections in cast steel covers. This would also prevent the formation of continuous cracks.
The cross section of the reinforcement is arbitrary and may be say round or square. However, better results can be expected from sections that generate major moments of resistance to flexure, such as girder sections. Concrete reinforcing steel may also be used. For the production of the covers the reinforcing members are simply placed in the casting mold and encast in the metal that forms the cover.
To facilitate the handling of such a cover the length and position of the embedded reinforcing members may be so chosen that the reinforcements project from the rim of the cover so that they can be used as brackets for transporting the covers, i.e., by a crane.
In yet another embodiment of the present invention the reinforcing members may be provided with bores for the passage therethrough of a coolant to cool the cover.
The cover is exposed to fluctuating temperatures, since during the casting process it is exposed from below to the radiant heat of the liquid steel contained in the casting vessel, while it will cool off when the casting vessel has been emptied of the liquid steel. This results in a temperature profile in the cover which varies with reference to time. The different degrees of expansion at different temperatures cause arching of the cover and the enforced bending leads to the appearance of the usual neutral bending line. In order to control the tendency of the cover to warp and to form cracks in an even more efficient way another useful feature of the invention consists in locating most of the reinforcing members in the zone above or below this neutral bending line, i.e., offset therefrom, so that the longitudinal axis of the reinforcing member does not coincide with the neutral bending line or plane of the cover. A particularly desirable effect is achieved if the coefficients of expansion of the base metal and of the reinforcing metal are different, so that strains will be generated by this difference which reduce the tendency to cracking and warping of the cover.
The location and number of the reinforcing members will principally depend upon the geometrical size and shape of the cover. For example, in a tundish an opening is provided for the supply from a ladle of the metal that is to be poured into the mold and possibly further openings are necessary for controlling the pouring rate of the liquid metal from the tundish into the molds with stopper rods. Since cracks often tend to connect with these openings, it is also preferred to provide reinforcing members around these openings.
Covers according to the present invention are schematically shown in the drawings in which:
FIG. 1 is a plan view of the cover of a tundish seen from above.
FIG. 2 is a plan view from above of a different embodiment of a tundish cover.
FIG. 3 is a vertical section of a casting vessel and cover and
FIG. 4 is a section taken on the line IV -- IV in FIG. 3.
FIG. 1 shows a tundish cover 1 of a three-strand billet casting machine. Encast in the cover 1, which consists of cast iron and is about 200 mm thick, are reinforcing members 2. These members consist of steel and have a square cross section, each side of the square being 45 mm long. An opening 3 in the cover serves for pouring steel from a ladle into the tundish. Openings 4 are provided for three stopper rods, not shown, which serve for controlling the flow of steel from the tundish into three molds. The length of the parallel reinforcing members 2 is such that they project from the edges of the cover 1 and that the projecting ends can be used as carrying pins 5 for handling the cover.
FIG. 2 shows another tundish cover 6, likewise made of cast iron. This cover contains reinforcing members 7 which are water-cooled tubes of steel. Cooling water can be circulated through the bores 8 in the members for cooling the cover. This cooling reduces the tendency of the cover to distort when it is exposed to the thermal radiation of the liquid metal which is contained in the casting vessel. The ends of the tubes projecting from the edge of the cover 6 are provided with flanges for connecting them to a cooling water circuit, not shown in the drawing. In the illustrated embodiment the liquid metal inlet opening 3 is also surrounded by such tubes which serve as reinforcing members.
FIGS. 3 and 4 illustrate a cover 9 which rests on a casting vessel 12 and contains reinforcing members 10. The thermal radiation emitted from below the cover by the metal bath 13 thermally stresses the cover 9 and thereby induces it to warp. However, distortion of the cover 9 is prevented by the particular position of the encast reinforcing member 10, since the larger part of the cross section of the member 10 is contained in the strained zone which is located above the neutral bending line 11, i.e. the horizontal center line of member 10 is offset in upward direction from the neutral bending line 11. Member 10 forms in this location, which is also colder, a particularly effective reinforcement.