US3766963A

US3766963A - Continuous casting methods and apparatus

Info

Publication number: US3766963A
Application number: US00136814A
Authority: US
Inventors: I Rossi
Original assignee: Innocenti Santeustacchio SpA
Current assignee: SMS Group SpA
Priority date: 1971-04-23
Filing date: 1971-04-23
Publication date: 1973-10-23
Anticipated expiration: 1990-10-23

Abstract

Continuous casting of strands wherein the strand after emerging from beneath a mold is gripped by power driven rollers and forced downwardly through guide elements defining a curved path to a horizontal direction of strand movement and through straightening elements which straighten the strand while it is still in a hot and plastic state.

Description

United States Patent 11 1 Rossi 1 Oct. 23, 1973 CONTINUOUS CASTING METHODS AND 3,391,725 7/1968 ROSSi 164/283 x 3,515,202 6/1970 Bick et al 164/89 APPARATUS V 3,559,720 2/1971 Vogel et al. 164/283 x [75 Inventor: Irving Rossi, Mornstown, NJ. FOREIGN PATENTS 0R APPLICATIONS [73] Asslgnee: gi i 'fii 403,304 5/1970 Australia 164/282 [22] Filed: Apr. 23, 1971 Primary Examiner-R. Spencer Annear Attorney-Joseph M. Fitzpatrick, John Thomas Cella, [2U Appl' 136314 Charles B. Cannon and Lawrence F. Scinto et al.

[52] US. Cl. 164/89, 164/282 57 ABSTRACT [51] Int. Cl. 822d 11/12 581 Field of Search 164/82, 89, 274, cmlmwus castmg Strands the Strand after l64/282 283 emerging from beneath a mold is gripped by power driven rollers and forced downwardly through guide [56] References Cited elements defining a curved path to a horizontal direction of strand movement and through straightening e1- 2 284 703 PATENTS 164/282 x ements which straighten the strand while it is still in a 6 1111 61 a h t d 1 ti t t 2,698,467 l/l955 Tarquinee 164/283 X 0 a p as 2,920,359 1/1960 Easton et al. 164/274 X 13 Claims, 8 Drawing Figures 3,358,744 12/1967 Rossi 164/282 3,375,864 4/1968 Butkevich et a1 164/282 I; LFJ 65 as Ill I: I: l

CONTINUOUS CASTING METHODS AND APPARATUS This invention pertains to methods and apparatus for the continuous casting of metal and provides improvements therein adapted more particularly for the continuous casting of billets.

In the continuous casting of billets, as well as slabs, an apparatus and method conventionally employed comprises a water-cooled tubular mold mounted at an elevated location with respect to the ground and with its top disposed above its base for gravity reception of molten metal teemed into the mold from a tundish. To start the operation, ,a plug or dummy billet is employed, one end of which is inserted and sealed into the base of the mold aperture, the end so inserted mounting a ring, hook, key, or the like, about which a portion of the teemed metal solidifies, whereupon the dummy is withdrawn followed by a continuous billet strand consisting of a solidified outer shell and a molten metal interior.

Guide means, such as guide rolls, are conventionally disposed below the mold for guiding the continuously cast strand along a preselected path which may extend vertically downward from the mold but more generally extends along an arcuate path into tangency with a horizontal direction of traverse at which a straightening unit having power driven rolls, is disposed for straightening the cast strand prior to passage through a cutoff device which shears the strand into lengths. Coolant sprays are provided along the path of traverse for progressively increasing the thickness of solidified outer shell until the strand is substantially solidified throughout as it enters the straightening unit.

In such conventional installations, the strand is pulled from the mold through the guide means by the power driven rolls of the straightening unit, and since the hot strand, especially that of steel, is considerably weaker in tension than it is in compression, it must be rapidly cooled and solidified in passing along the guide means to prevent rupture by the pull thereon exerted entirely from below by the straightening unit. However, as the billet strand thus progressively solidifies, it become progressively stiffer, necessitating massive power driven rolls in the straightening unit for pulling the strand through the guide means and also for straightening the strand.

in marked contrast to this conventional mode of operation, in my invention, an apparatus and method is provided whereby the cast strand is pushed through the guide means by one or more pairs of power driven rolls which are mounted between the mold and the guide means. Since as above stated the hot metal of the strand is much stronger in compression than in tension, it can be thus pushed through the guide means in a hotter and hence more plastic and pliable state and with less thickening of the solidified outer shell of the strand than is required for pulling the strand through the guide means in accordance with conventional practice.

For assuring that the billet strand as thus pushed through the guide means will follow a desired preselected path, I provide a tubular guide member through which the strand is thus pushed, which preferably is of arcuate contour longitudinally thereof for guiding the strand from the mold into tangency with a horizontal direction of traverse for passage through a cutoff device.

By maintaining the strand in a sufficiently hot and plastic state as it thus pushed through the tubular guide member, I find that the strand will substantially of its own weight, pass downwardly along and be guided by the tubular guide and will straighten itself out in a horizontally disposed lower terminal section of said guide, whereby the conventionally employed straightening unit may be eliminated, and the strand passed directly from the guide to a cutoff device for shearing into lengths.

In order to assure that the solidified outer shell of the cast strand will be sufficiently thickened upon being engaged by the driven rolls disposed between the mold and the tubular guide member, for pushing the strand through the tubular guide member, I further provide in the apparatus of my invention, an open grid structure including a series of spaced bars attached to the base of the mold and which extend downwardly along an arcuate path thence to a distance slightly short of that where the driven rolls are located. Spray jets are mounted along and about grid for spraying a coolant liquid, such as cold water, onto the billet strand as it passes from the mold to the driven rolls, thereby rapidly increasing the outer solidified shell of the strand to a sufficient depth and strength to support the roll pressure. The tubular guide member mounts guide bars or rolls internally thereof for guiding the billet strand therethrough. The tubular guide member also mounts spray nozzles therealong and thereabout for spraying a coolant liquid, such as cold water, onto the billet strand as it passes through the guide member.

For start-up operations, the apparatus of the invention employs a relatively short plug or starter bar of a linked construction such as to be insertable through the mold downward until its upper end seals the base of the mold with the lower end of the starter bar engaging the rolls of the uppermost driven roll pair. On the upper end of the starter bar is mounted a key, hook, or the like, shaped to anchor upon solidification, molten metal teemed thereabout, thus to initiate the continuous casting operation upon driving the aforesaid roll pair in the direction to withdraw the starter bar from the mold followed by the billet strand. The driven rolls push the starter bar and attached billet strand thence through the tubular guide member to the cutoff device, whereat the billet strand is severed from the starter bar to permit removal thereof from the path of the strand traverse.

In accordance with my invention, I propose to so control the cooling rate of the cast billet strand as it passes from the mold to the horizontal traverse at a temperature of about l,200-2,000F such that the casting will straighten itself out by gravity within a horizontally disposed terminal section of the tubular guide and be completely solidified when it enters the cutoff device. Therefore, the casting apparatus can be made of relatively light and economical construction. Also, by shearing the billet strand while thus hot but solidified, the size and power of the shear may be correspondingly reduced.

Having thus described the invention in general terms, reference will now be had for a more detailed description to the accompanying drawings wherein:

FIG. 1 is a longitudinal, vertical elevation, partly in section, of an apparatus according to the invention, this view illustrating the invention as employed for the continuous casting of a metal ingot subsequent to start-up operation thereof.

FIGS. 2-5 inc., are transverse sections of FIG. 1 as taken at 22 to 5-5 inc., respectively of FIG. 1.

FIG. 6 is a partial view of FIG. 1, as modified to illustrate the start-up operation of the apparatus by means of an articulated dummy plug or starter bar; while FIG. 7 is a longitudinal sectional view of the dummy plug shown in elevation in FIG. 6, and FIG. 7a is a section at 7a-7a of FIG. 7.

Referring to FIGS. 1-5, inc., the apparatus therein shown comprises a tundish 10 containing molten metal, in this case steel, which is teemed thence by gravity, as at 11, into the top of a substantially vertically disposed tubular mold 12, made of a metal of high thermal conductivity, such as copper. The mold is cooled by a series of spray jets 13, which sprays a coolant liquid, such as cold water, against all sides thereof. This causes the molten steel to solidify adjacent the mold walls, as at 14, into an outer shell of the cast metal enclosing a core of the molten steel, as at 15. The mold is of substantially rectangular cross-section, as shown in FIG. 2, for continuously casting a billet strand of preselected sectional dimensions.

The billet strand so-formed, comprising its outer solidified shell 14 and molten interior 15, exits, as at 16, from the base of the mold, whereat it passes through a passage formed by a gridwork of bars attached-to the base of the mold, which guide and support the billet strand, as at 17, 18, FIGS. 1 and 3. A series of spray nozzles are disposed about and along the gridwork, as at 19, 20, for spraying a liquid coolant, such as cold water, onto the billet strand through the openings between the grid bars, and also onto the grid bar's, thus to increase rapidly the thickness of the solidified outer shell of the billet strand in the manner illustrated at 14 of FIG. 3.

The billet strand, after passing through the grid structure 17, 18, passes between a pair of driven rolls, as at 25, 26, FIGS. 1 and 4, each roll of which is peripherally so grooved and otherwise shaped, as at 27, 28, 29, FIG. 4, as to engage adjacent faces of the billet strand 16, as at 30, 31, and such that the rolls conjointly engage all sides of the billet strand in the manner illustrated in FIG. 4. The

rolls

25, 26 are geared to an electrical motor by obvious means (not shown), for driving the rolls in either direction of rotation. With the apparatus operating as shown in FIG. 1, the rolls are driven in such direction as to propel the billet downwardly and push it through a tubular guide member 32 mounted below the rolls and in the manner shown in FIG. 1.

The tubular guide member 32 is constructed as shown in FIGS. 1 and 5, and comprises a housing of longitudinally bifurcated sectional construction, the sections as at 33, 34, of which are bolted together, as at 35, 36, at spaced points along their length, for ease of assembly and disassembly. Each section mounts in its interior, a series of longitudinally extending guide bars, as at 37, 38, the inner ends of which form a passageway of the sectional contour of the billet strand 16, and which collectively engage all four walls of the billet strand in the manner shown in FIG. 4. Spray jets penetrate thetubular guide member 32 at spaced points thereabout and therealong, as at 40, 41 and 42, 43, for spraying a coolant, such as water, onto all sides of the billet strand throughout its length. These sprays are adjusted to provide controlled cooling of the strand. Thereby the billet strand passes through the tubular member 32 and conforms to the passageway therethrough substantially of its own weight. Guide rolls may be substituted for the guide bars 37, 38.

On exiting from the tubular guide member 32, the billet strand passes a cutoff device 47,'which shears the billet strand into desired lengths.

In order to start the continuous casting operation, as illustrated in FIGS. 1-5, inc., and as above-described with reference thereto, a plug or starter bar is employed, as illustrated in FIGS. 7 and 7a, and as utilized in the manner shown in FIG. 6. Referring thereto, the starter bar, shown generally at 50, comprises a head member 51, made preferably of copper, and shaped to fit and seal into the bottom of the mold 12, in the manner shown in FIG. 1. The head member 51 is fitted with a key member 52, preferably made of steel, such that a portion of the molten steel teemed from the tundish into the mold, will solidify about the key member for anchoring the solidified base of the cast billet to the starter bar. The head member 51 terminates at its base in a curved or spherically-shaped, concave surface, as at 51a, which bears against a complementary convex curved or spherical surface 53 formed on the upper end of a link member 54, comprising one of a series of link members 54-57, similarly shaped to bear one against another seriatum in the manner. best shown in FIG. 7. The series of members 51 and 54-57, inc., are articulatively linked together by means of a flexible strip of steel 58, which extends through slots of these members and is pin welded at its upper end, as at 60, to the upper member 51, and terminates at-its base in a projecting bolt 61 welded to the lower end of strip 58 and encircled by a helical compression spring 62, interposed between the lowermost link member 57 anda terminal nut 63 threaded onto the bolt. The starter bar may thus be flexed and bent to correspond to the arcuate and horizontal traverse of the billet strand to the cutoff, beyond which it is severed from the casting by the shear.

Referring to FIGS. 6 and 7, the lower end of the starter bar 50 is inserted into the top of the mold l2.and thrust downwardly until its upper end 51 seals the base of the mold and its lower end 57 engages the

rolls

25, 26, in the manner shown in FIG. 6. Teeming of molten steel from the tundish 10 into the mold is thereupon started, and upon solidification of the metal about the starter key 52, the

rolls

25, 26 are driven to withdraw the starter bar from the mold fOllOWBd'b) the cast billet strand. The starter bar, followed by the cast billet is fed thence by the rolls down through the tubular guide member 32, and thence to the cutoff device 47. When the starter bar, followed by the billet strand clears the cutoff device, it is activated to shear the end billet strand in the manner shown at 65 at FIG. 1. The starter bar is removed from the casting line so that the casting operation thus initiated, may be continued.

The starter bar 50, FIG. 7, is made preferably of copper, and it is sprayed at the time of or before the liquid metal is introduced into the mold so that the incoming metal is instantaneously solidified and thus the'withdrawal of the starter bar and the solidified steel strand can be quickly started. Also referring to FIG. 6, the mold may be straight or curved and it may be oscillated or vibrated or static.

I claim:

1. The method of continuous metal casting which comprises: casting hot, molten metal into an elevated tubular mold with chilling to produce an issuing strand comprising an outer shell of solidified metalencasing a molten metal core, mechanically buttressing said issuing strand at spaced points thereabout and longitudinally thereof while spraying a coolant on all sides of said strand for thickening said shell, thence gripping said strand and progressively pushing it under compression downwardly into and through tubular mechanical guide means having a series of elements extending along the length thereof to form a passageway of the sectional contour of the strand and to collectively engage all of the different walls of the strand, said passageway being shaped to define a path extending arcuately from a downward direction to a horizontal direction, and while maintaining said strand in a sufficiently hot and plastic state to conform to the shape of said guide means and to conform substantially of its own weight to said mechanical guiding.

2. The method according to claim 1 wherein said strands upon traversing said path in said horizontal direction is straightened and is progressively sheared into discreet lengths.

3. The method according to claim 1 wherein during said mechanical guiding said strand use steel is subjected to controlled cooling such as to solidify said strand throughout while maintaining said strand as solidified at a temperature in the range of about l,2002,000F, and shearing said strand while at said temperature into discrete lengths.

4. The method according to claim 2 wherein said strand use steel is solidified throughout and is at temperature within the range of about 1,2002,000F when sheared into discrete lengths.

S. The method according to claim 1 wherein said strand is gripped between rolls driven in a direction to push said strand downwardly along said mechanically guided path.

6. The method according to claim 2 wherein said strand is gripped between rolls driven in a direction to push said strand along said mechanically guided arcuate path and thence horizontally extending path.

7. Apparatus for continuous metal casting, comprising: a tubular mold having means for cooling the same, means mounting the mold with its ends differently elevated, spaced grid bars extending downwardly from the mold base for receiving, guiding and buttressing a metal strand as cast from said mold, means for spraying a coolant liquid through said bars onto said strand, tubular guide means mounted beneath said mold for receiving and guiding said strand, said tubular guide means having a series of elements extending along the length thereof to form a passageway of the'sectional contour of the strand and to collectively engage all of the different walls of the strand, said passageway defin ing a path which extends arcuately from a downward direction to a horizontal direction, rolls mounted below said grid bars and relatively positioned to receive and grip said strand, and means for driving said rolls to force said strand under compression through said guide means.

8. Apparatus according to claim 7 in combination with a tubular guide member mounted beneath said rolls for receiving and guiding said strand, and means penetrating said tubular guide member for spraying a coolant liquid onto said strand in passing through said member.

9. Apparatus according to claim 8, wherein said tubular member is, in part, of arcuate configuration longitudinally thereof for guiding said cast metal strand from an upper to a lower elevation and terminates at its lower end in a substantially rectilinear portion for straightening said strand as it exits from said member.

10. Apparatus according to claim 9 including a cutoff device disposed adjacent the exit from said tubular guide member, for shearing said strand into discrete lengths.

11. Apparatus according to claim 9, wherein said tubular guide member comprises a housing of longitudinally bifurcated, sectional construction having means for assembling and disassembling said sections, said housing sections mounting means for guiding said cast metal strand through said member, said housing being of substantially greater transverse dimensions than said cast metal strand and having spray nozzles penetrating said housing for spraying a coolant on and about said strand.

12. Apparatus according to claim 7 including a starting starter bar consisting of a head member adapted to ift into the base of said mold and mounting an anchoring lug thereon, and a plurality of link members, linked seriatum to said head member by means of a flexible, aligning spring member, said head and link members engaging one another in contoured complementary surfaces for relative articulation thereof.

13. Apparatus according to claim 12, wherein the head member of said starter bar is made of a metal of high thermal conductivity for rapid cooling by spraying prior to metal casting.

Claims

1. The method of continuous metal casting which comprises: casting hot, molten metal into an elevated tubular mold with chilling to produce an issuing strand comprising an outer shell of solidified metal encasing a molten metal core, mechanically buttressing said issuing strand at spaced points thereabout and longitudinally thereof while spraying a coolant on all sides of said strand for thickening said shell, thence gripping said strand and progressively pushing it under compression downwardly into and through tubular mechanical guide means having a series of elements extending along the length thereof to form a passageway of the sectional contour of the strand and to collectively engage all of the different walls of the strand, said passageway being shaped to define a path extending arcuately from a downward direction to a horizontal direction, and while maintaining said strand in a sufficiently hot and plastic state to conform to the shape of said guide means and to conform substantially of its own weight to said mechanical guiding.

3. The method according to claim 1 wherein during said mechanical guiding said strand use steel is subjected to controlled cooling such as to solidify said strand throughout while maintaining said strand as solidified at a temperature in the range of about 1,200*-2,000*F, and shearing said strand while at said temperature into discrete lengths.

4. The method according to claim 2 wherein said strand use steel is solidified throughout and is at temperature within the range of about 1,200*-2,000*F when sheared into discrete lengths.

5. The method according to claim 1 wherein said strand is gripped between rolls driven in a direction to push said strand downwardly along said mechanically guided path.

7. Apparatus for continuous metal casting, comprising: a tubular mold having means for cooling the same, means mounting the mold with its ends differently elevated, spaced grid bars extending downwardly from the mold base for receiving, guiding and buttressing a metal strand as cast from said mold, means for spraying a coolant liquid through said bars onto said strand, tubular guide means mounted beneath said mold for receiving and guiding said strand, said tubular guide means having a series of elements extending along the length thereof to form a passageway of the sectional contour of the strand and to collectively engage all of the different walls of the strand, said passageway defining a path which extends arcuately from a downward direction to a horizontal direction, rolls mounted below said grid bars and relatively positioned to receive and grip said strand, and means for driving said rolls to force said strand under compression through said guide means.

12. Apparatus according to claim 7 including a starting starter bar consisting of a head member adapted to fit into the base of said mold and mounting an anchoring lug thereon, and a plurality of link members, linked seriatum to said head member by means of a flexible, aligning spring member, said head and link members engaging one another in contoured complementary surfaces for relative articulation thereof.