US3608620A

US3608620A - Apparatus for guiding a straightened strand in a continuous casting machine

Info

Publication number: US3608620A
Application number: US884820A
Authority: US
Inventors: Georg Bollig; Horst Grothe; Walter Meier; Josef Zeller
Original assignee: Schloemann AG
Current assignee: Schloemann AG
Priority date: 1968-12-13
Filing date: 1969-12-15
Publication date: 1971-09-28
Anticipated expiration: 1988-09-28
Also published as: JPS4822885B1; SE364889B; NL6918409A; AT297241B; FR2026066B1; GB1274557A; FR2026066A1

Abstract

In a continuous casting machine a strand having a solidified shell and a liquid core moves onto a roller table and a dummy bar attached to the head end of a strand is detached from the strand and removed from the path of the strand, or is inserted into the strand path in the machine, at a point in the area of said roller table. Dummy bar storage apparatus has an end portion movable into and out of the path of a strand at said point for the insertion or removal of a dummy bar. As disclosed, the machine includes guide apparatus for supporting a strand moving onto the roller table by support means for engaging and supporting at least two opposite sides of a strand to resist bulging due to ferrostatic pressure in the strand core. The guide apparatus includes at least one movable guide unit, which is movable away from said point to provide clearance for the end portion of the dummy bar storage apparatus to move into the strand path at said point for inserting or removing a dummy bar, and which is movable toward said point, when the latter end portion is out of the strand path, so that the guide apparatus engages and supports a strand at said point.

Description

Wit

v [72] Inventors Appl. No.

Filed Patented Assignee Priorities Georg Bollig Buederlch;

Horst Grothe, Kaarst, Germany; Walter Meier, Winterthur; Josef Zeller, Weesen, Switzerland Dec. 15, 1969 Sept. 28, 1971 Schloemann Alttieggesellseliatt Duesseldori, Germany and Concast AG, Zurich, Switzerland Dec. 13, 1968; Jan. 20, 1969 Germany; Switzerland APPARATUS FOR GUIDING A STRAIGl-ITENIED STRAND IN A CONTINUOUS CASTING MACE 3 ,483 ,915 12/1969 Schneckenburger et al 164/282 X 3,495,651 2/1970 Rokop et al7 164/282 X 3,496,990 2/1970 Meier et al 164/282 3,528,488 9/1970 Bode 164/282 Primary Examiner-J. Spencer Overholser Assistant Examiner-John E. Roethel Attorney-Sandoe, Hopgood & Calimafde ABSTRACT: In a continuous casting machine a strand having a solidified shell and a liquid core moves onto a roller table and a dummy bar attached to the head end of a strand is detached from the strand and removed from the path of the strand, or is inserted into the strand path in the machine, at a point in the area of said roller table. Dummy bar storage apparatus has an end portion movable into and out of the path of a strand at said point for the insertion or removal of a dummy bar. As disclosed, the machine includes guide apparatus for supporting a strand moving onto the roller table by support means for engaging and supporting at least two opposite sides of a strand to resist bulging due to ferrostatic pressure in the strand core. The guide apparatus includes at least one movable guide unit, which is movable away from said point to provide clearance for the end portion of the dummy bar storage apparatus to move into the strand path at said point for inserting or removing a dummy bar, and which is movable toward said point, when the latter end portion is out of the strand path, so that the guide apparatus engages and supports a strand at said point.

PATENIEU SEP28 I971 MU 2 0F 4 FIG.4

INVLN'IORS GEORG BOLLIG HORST GROTHE BY JOSEF ZELLER M Ho I MI flh lfl ATTORNEYS PATENTEI] saves I971 SHEET 8 0F 4 FIG.8

mw ww HORST 6R0 INE MEIER mun aoser ZELLER Ink H 14" q MAM ATTORNEYS The present invention relates to a guide apparatus for a straightened continuous steel casting having an externally solidified shell and a liquid core. The continuous casting machine has a guide apron of which at least a part is curved and which leads in a straight roller table. A flexible dummy bar is introduced or removed in the area of this straight roller apron.

In a continuous casting plant comprising an open ended mold the externally solidified casting which still has a liquid core is withdrawn from one open end of the mold. In the following guide apron, which is curved in at least part of its length, the casting is cooled and is then straightened in a combined withdrawal and straightening apparatus which delivers the casting onto a straight roller table. Means for the introduction of a dummy bar into the path of the casting, and for removing it from said path, are usually provided behind the final pair of rolls of withdrawal and straightening apparatus, or behind the final bending roll in cases in which the casting is straightened in the guide apron.

When the casting rate of strands of large cross sections is increased, bulges may appear on the strand after has passed the point where the dummy bar is introduced into the path. The length of the liquid core in the strand increases roughly in proportion with the casting rate and the bulging results from the thinner and hotter solidified skin. The bulges reduce the quality of the casting and cause difficulties-particularly during further processing-and also increase risk of a breakout of liquid metal.

It is known that in machines operating at high casting speeds, the liquid core extends into the straightened part of the strand and that therefore the strand must be further supported and cooled. The entry and removal point of the dummy bar in such a machine is located at the end of the zone in which the strand is still supported. Consequently, the dummy bar and the equipment for storing it must be correspondingly longer, or additional withdrawal rolls must be provided. This prolongs the time needed for the introduction of the dummy bar into the machine before the beginning of the casting. The time needed to prepare the apparatus for a new casting cycle is thus prolonged and the productivity of the machine is proportionately reduced. Moreover, a longer dummy bar, and the correspondingly longer storage apparatus, occupy more space.

An object of the present invention is to provide a continuous casting machine for high casting speeds and for large casting cross sections, in which bulging of the strand will not occur behind the entry and removal point of the dummy bar, despite the fact that the plant offers all the advantages of locating the entry and removal point for the dummy bar immediately behind the point where the strand has been straightened, and where the strand still has a liquid core According to the invention this is achieved by forming a guide apparatus which is composed of a roller table and cooperating guide units consisting of rolls and/or plates. This guide apparatus is located at the downstream side of the introduction and removal point of the dummy bar and is adapted to support the strand on at least two opposite sides against the ferrostatic pressure so as to prevent bulging. At least one of the guide units can be moved in linear direction, or tilted, for clearing the point at which the dummy bar is introduced and removed.

This guide apparatus permits the casting of slabs of, for example, l,l mm. X 300 mm. at a rate of up to 2 meter/minute without bulging, whereas a conventional casting rate under the same casting conditions, but without this guide apparatus, is only about 1 meter/minute.

Depending on the size of the machine, on the means for coupling the dummy bar and the strand and on local conditions, at least one of these guide units may be movable either in the longitudinal direction of the strand or transversely thereto.

For strands in which the liquid core extends for only a short distance beyond the introduction and removal point of the dummy bar, all cooperating guide units could be linearly and tiltably movable.

It is very important for the quality of the casting and the casting speed that the guide apparatus can receive and support the strand immediately after the dummy bar has been detached from the strand and before bulges can appear. Consequently, it is preferred that the displacement of one of the guide units towards the dummy bar entry and removal point should coincide with the detachment of the dummy bar from the strand.

The guide apparatus is movable perpendicularly to the roller table in order to facilitate the reception of curved leading ends of strands and also to permit the withdrawal of curved cold strands from a curved apron. For this purpose, the main frame members of the guide apparatus, which has guide units movable in longitudinal direction of the strand, can be raised and lowered by power cylinders.

The forces generated by the ferrostatic pressure, which are first absorbed by the movable guide units, are not transmitted to'the main frame members by wheels or other movable parts. Instead, when ferrostatic forces are operative the frame members opposite the wheels of the movable guide units bear directly against the main frame members of the guide apparatus.

Guide units which are movable perpendicular to the strand can be used for disconnecting the dummy bar from the strand.

The invention is described in detail below with respect to embodiments shown in the accompanying drawings in which:

FIG. 1 is a side elevation, partly in section, of guide apparatus in accordance with the invention showing the dummy bar storage device in lower position;

FIG. 2 is a section on lines ll-ll of FIG. 1;

FIG. 3 is a side elevation as in FIG. 1, but showing the dummy bar storage device in raised position;

FIG. 4 is a side elevation, partly in section, of another embodiment of guide apparatus of this invention, showing the dummy bar storage device in lower position;

FIG. 5 is a side elevation similar to FIG. 4, but showing the dummy bar storage device in raised position;

FIG. 6 is a section on lines VI-Vl of FIG. 5;

FIG. 7 is a side elevation, partly in section, of a third embodiment of guide apparatus of this invention; and

FIG. 8 is a side elevation, partly in section, of a fourth embodiment of guide apparatus of this invention, which has a pivotable guide unit.

Referring to the drawings, FIG. 1 shows a conventional curved roller apron l which guides a strand 5 into withdrawal and straightening apparatus 2. When a straight mold is used, this curved apron I may be preceded by a straight roller apron. Indicated at 3 is the point at which a dummy bar 4 is introduced into and removed from the path of a strand 5. The strand 5, which has been straightened in the withdrawal and straightening apparatus 2, is shown connected to a flexible dummy bar 4i.

A dummy bar storage apparatus 7 is located above a straight roller table 6 and is pivotable around pivot 3. A power cylinder 9 has lowered the storage apparatus 7 into the path of the strand 5 to receive the dummy bar 4 and conventional means, not shown in the drawing, such as a cable, is provided for pulling the dummy bar 4 into the storage apparatus 7. When the leading end of strand 5 has reached the position illustrated in FIG. 1, i.e., when the dummy bar head 4a has passed the withdrawal and straightening apparatus 2, the power cylinder 9 lifts the storage apparatus 7 and thus detaches the dummy bar head 40 from the leading end of the strand 5.

In order to provide support from above for the strand 5 to contain the internal ferrostatic pressure while the strand continues to advance on rollers 10 of the roller table 6, a guide unit II, which forms part of the guide apparatus located after the dummy bar entry and exit point 3 and which can be moved in the longitudinal direction of the strand, is propelled by wheels 12 towards the entry and exit point 3. At the same time, the dummy bar 4 is detached from the strand 5. The wheels 12 run on rails 13 supported by channels 14 on both sides of the roller table 6. These channels 14 are connected by cross members 15 to form a frame and the guide unit 11 can be raised and lowered by power cylinders 16 acting on said frame. Spacers 17 permit a rapid and accurate perpendicular adjustment to different strand sizes.

FIG. 2 shows the guide unit 11, comprising the wheels 12, wheel casings 20, longitudinal members 21, cross members 22 and guide means for the strand 5, such as rollers 24 and/or plates 23. Rollers 24 are located between the plates 23 to provide a clearance gap for cooling water between the surface of the strand and the plates 23. Guide unit 11 is moved by pinions 25 which mesh with racks 26. A DC motor 27 (FIG. 1) drives the pinion 25 by chain 270. The motor 27 is synchronized with the power cylinder 9 and advances the unit 1 1 towards the dummy bar entry and exit point 3 in such a way that it arrives in its operative position and presses on the strand 5 as quickly as possible.

The guide unit 11 has a clearance 28 with respect to the channels 14 in order to be movable thereunder; during movement of the guide unit 11, when there is no strand therein, the clearance 28 between the longitudinal members 21 of the unit and the channels 14 is about 4 mm. As a strand 5 enters the guide unit 11, the guide unit, which rests freely on wheels 12, is lifted by the strand forcing its way under the rollers 24 until the unit's upper longitudinal members 21 bear tightly against the channels 14. The ferrostatic pressure is thus directly transmitted by the upper longitudinal members 21 to the channels 14. i

The rollers 24 and the cooling plates 23 are resiliently mounted by suitable means, such as by springs 29, or by hydraulic dampers, in guide bearings 35 to give sufficient support to the strand 5 to contain the ferrostatic pressure within, but to yield to excessive pressure. The guide bearings 35 may be constructed as described in the U.S. Pat. application Ser. No. 814,247, filed on Apr. 8, 1969. By using double-acting power cylinders as guide bearings 35, the rollers 24 and/or the cooling plates 23 can be lifted individually or in groups to insure an unobstructed introduction of the leading end of the strand into the guide unit 11. The lifting and lowering of the rollers 24 and cooling plates 23 may be controlled by a copying or counting mechanism.

FIG. 3 shows the movable guide unit 11 in operative position cooperating with the rollers of the roller table 6. The forces generated by the ferrostatic pressure in the liquid core 36 of the strand 5 act on the solidified shell of the strand and are counteracted by the rollers 10 of the roller table 6 and the rollers 24 of the guide unit 11. Sprays 33 cool the strand as an alternative to the cooling plates 23 shown in FIG. 1. Either all or only individual rollers 10 of the roller table 6 may be driven for conveying the strand 5. The rollers 24 of the guide unit 11 may also be driven.

FIG. 4 shows an embodiment of the invention in which two

guide units

60 and 61 are movable perpendicular to the longitudinal axis of the strand 5. The dummy bar storage apparatus 7' is pivoted in a sliding pivot, consisting of a pivot 8' and a slot 55 and, as shown, in its operative position it rests on a cross member 57. When the dummy bar head 4a reaches the position shown in FIG. 4 the cooperating

guide units

60 and 61 are lifted by a power cylinder 59. This upward movement causes the detachment of the dummy bar head 40 from the strand 5 and also lifts the lower guide unit 60 to the elevation of the roller table 65, and the upper guide unit 61 to the elevation of the strand guide 65a. Rollers 62 of the upper guide unit 61 cooperate with rollers 63 of the lower guide unit 60. Guide means, such as guide rollers 64, are mounted on the

guide units

60 and 61 to prevent them from tilting caused by the eccentrical reaction force generated during the detachment of the dummy bar head 4a from the strand 5. A suitable manner for detaching the dummy bar head 40 from the strand 5 is described in the U.S. Pat. application Ser. No. 736,095, filed on June ll, 1968.

FIG. 5 shows the

guide units

60 and 61 in operating position after having been moved perpendicular to the longitudinal axis of the strand 5, which is shown passing through the guide units. The liquid core of the strand is indicated at 36.

As an alternative design, the lower guide unit 60 may be rigidly connected to the roller table 65 while the upper guide unit 61 may be movable horizontally in the transverse direction to the longitudinal axis of the strand.

FIG. 6 shows a stop 70 which limits the upward movement of the

guide units

60 and 61. Spacers 71 and shims 72 are used to adjust the space between the guide units for the strand size. The rollers 62 are supported in guide bearings 35 as in the description of FIG. 2.

FIG. 7 shows a guide unit 83 located between the withdrawal and straightening apparatus 2 and a roller table 85. The guide unit 83 comprises a roller table with rollers 86 and an upper member 87 with rollers 81. The strand 5 is guided by the

rollers

86 and 81. The roller table 80 and the upper member 87 form a unit which is connected by tie rods 84 and power cylinders (not shown). The tie rods 84 are held by cross members 89 and are kept at a suitable distance above the upper member 87 by spacers 90 to obtain the required distance between the

rollers

81 and 86 according to the strand size that is being cast. The spacers 90 have different thicknesses so that a few of them can be combined to produce any desired distance between the

rollers

81 and 86. Trucks 91 which roll on

rail sections

92 and 93, are pivotably mounted on both ends of the roller table 80. The downstream end of the rail section 93 slopes in the direction of the strand travel so that the inlet and of the guide unit 83 is thereby lowered when it moves in the direction of the strand travel, as indicated by arrow 94. The guide unit 83 is driven by a lever 95 which is connected to the roller table 80 by a sliding pivot 96. The other end of the lever 95 is pivoted on a bearing block 97 in the foundation. The lever 95 is articulated to the piston rod 98 and actuated by power cylinder 99. The above described combined longitudinal and tilting movement of the strand inlet end of the guide unit 83 is necessary when the dummy bar 4 is being introduced into the casting machine at the dummy bar entry-exit point 3 to prepare the machine for a new casting.

FIG. 7 shows the strand 5 and the dummy bar 4 in dot and dash lines in the position in which the dummy bar is about to be disconnected. During this operation, and also when the dummy bar is introduced into the machine, sufficient space is made available by withdrawing the guide unit 83 to its position indicated in dot and dash lines.

FIG. 8 shows, as a further embodiment of the invention, a guide apparatus having a pivotable guide unit 41. In the position shown, the lead end of the strand 5 has just left the last pair of rollers of the withdrawal and straightening apparatus 2 and the dummy bar 4 is about to be disconnected from the strand 5. After the dummy bar 4 has been completely disconnected from the strand 5 and has been removed out of the swing area of the guide unit 41, the latter is lowered abut its pivot 47 into a position, shown in dot and dash lines, in which it guides and supports the advancing strand 5. The rollers 10 of the roller table 6 cooperate with rollers 44 of the pivotable guide unit 41 and rollers 45 of the strand guide 46 to form a guide apparatus. The guide unit 41 is articulated to the piston rod 48, and is raised and lowered by power cylinder 49.

The embodiments of the invention shown in FIGS. 1, 4, 7 and 8 are preferably used for the casting of slabs. The narrow sides of the slabs are usually not supported. However, they can also be updated for the casting of shapes which require support on all sides.

The invention is not restricted to the shown embodiments. For instance, the dummy bar could be introduced into the casting machine from below, whereby the upper parts of the guide apparatus would be stationary, while the lower parts would be designed as movable guide units. In still another design, both the upper and the lower components of the guide apparatus could be designed as movable guide units.

What is claimed is:

i. A continuous casting machine in which a cast strand having a solidified shell and a liquid core moves along an at least partly curved guide apron which leads onto a roller table, in which a dummy bar attached to the lead end of the strand is detached therefrom and removed from the path of the strand at a point in the area of said roller table, and which includes dummy bar storage apparatus having an end portion movable into and out of the path of the strand at said point for insertion of the dummy bar into, and the removal of it from, said path of the strand, characterized in that guide apparatus is provided for supporting the strand as the strand moves onto said roller table, said guide apparatus having support means at least at two opposite sides for engaging opposite sides of a strand to resist bulging of the strand due to ferrostatic pressure in the core thereof, and said guide apparatus incorporating a guide unit mounted for movement away from the point in the path of the strand at which said end portion of the dummy bar storage apparatus moves into and out of said path so as to provide clearance for said end portion to move into said path and then for movement toward said point when the said end portion is out of said path for the guide apparatus to support a strand at said point.

2. The casting machine of claim 11 wherein said guide apparatus comprises a lower support surface for the underside of a strand and a guide unit mounted above said support surface in cooperative strand-supporting relative thereto, said guide unit having guide elements thereon for engaging the upper side of a strand, and said guide unit being mounted for movement generally parallel to the support surface in the longitudinal direction thereof, toward and away from said point.

3. The casting machine of claim 2 which includes power drive means connected for moving the guide unit toward said point when said end portion of the dummy bar storage apparatus is moved out of the path of the strand at said point.

4. The casting machine of claim 2 in which the guide apparatus includes a frame, having an overhead portion above said lower support surface, and in which said guide unit is supported on said frame for movement thereon generally parallel to, and relatively along, the lower support surface, said guide unit being mounted for upward movement relative to the frame, up to said overhead portion of the frame which limits further upward movement, so that sufficient upward movement of a strand within the guide apparatus moves the guide element up against said overhead portion whereby continued upward pressure of the strand is transmitted to the frame.

5. The casting machine of claim 4 including means for moving the frame up and down relative to said lower support surface for to vary the height of the strand-receiving space between the lower support surface and the guide elements of the guide unit.

6. The casting machine of claim 4 in which the frame includes resilient means arranged for urging the guide unit downward relative to the frame whereby upward movement of the guide unit is against the pressure of said resilient means.

7. The casting machine of claim 1 in which said guide apparatus comprises a pair of guide units in parallel-spaced relation forming a strand receiving passage between them, at least one of said units being movable transversely of the path for the strand at said point to be movable away from said point to provide clearance for said end portion of the dummy bar storage apparatus and, when said end portion is out of said path, to be movable to a position toward said point, in which position said strand receiving passage is aligned to support therethrough a strand moving onto said roller table.

The casting machine of claim 7 in which said movement of at least one of said units transversely of the path for the strand and toward said point brings said one of the units into engagement with the end portion of a dummy bar attached to a strand on said path and disconnects said dummy bar from said strand by moving said end portion of said dummy bar out of said path.

9. The casting machine of claim 7 which includes means for adjusting the spaced relation of the pair of guide units to vary the heiglfit of said strand receiving passage.

it). e casting machine of c arm 7 which includes power means connected for moving the guide unit toward said point when said end portion of the dummy bar storage apparatus is moved out of the path of a strand at said point.

11. The casting machine of claim 1 in which said guide apparatus comprises a pair of guide units joined together in parallel-spaced relation and forming a strand receiving passage between them, said pair of units being movable generally in the longitudinal direction of the path of the strand toward and away from said point, means for tilting said pair of units out of said path as the units move sway from said point to provide clearance for said end portion of the dummy bar storage apparatus to move into said path, and said tilting means being operable, when said portion of the dummy bar storage apparatus is out of said path and the units are moved toward said point, for tilting said units to a position in which said strand receiving passage is aligned to support therethrough a strand moving onto the roller table.

12. The casting machine of claim 11 including power drive means for moving said pair of units generally in said longitudinal direction toward and away from said point.

13. The casting machine of claim 12 in which said power drive means comprises a lever pivotally connected to said pair of units and a power cylinder connected to the lever for pivotting the lever to move the pair of units toward and away from said point.

M. The casting machine of claim 11 including tie rods connected for joining the guide units together with spacers associated with said tie rods for varying the height of the strand receiving passage between the units.

15. The casting machine of claim 1 wherein said guide apparatus comprises a lower support surface for the underside of a strand and a guide unit mounted above said support surface in cooperative strand-supporting relation thereto, said guide unit having guide elements thereon for engaging the upper side of a strand, and said guide unit being pivotally mounted for movement toward and away from said lower support surface respectively supporting a strand at said point and for providing said clearance for the end portion of the dummy bar storage apparatus.

Claims

1. A continuous casting machine in which a cast strand having a solidified shell and a liquid core moves along an at least partly curved guide apron which leads onto a roller table, in which a dummy bar attached to the lead end of the strand is detached therefrom and removed from the path of the strand at a point in the area of said roller table, and which includes dummy bar storage apparatus having an end portion movable into and out of the path of the strand at said point for insertion of the dummy bar into, and the removal of it from, said path of the strand, characterized in that guide apparatus is provided for supporting the strand as the strand moves onto said roller table, said guide apparatus having support means at least at two opposite sides for engaging opposite sides of a strand to resist bulging of the strand due to ferrostatic pressure in the core thereof, and said guide apparatus incorporating a guide unit mounted for movement away from the point in the path of the strand at which said end portion of the dummy bar storage apparatus moves into and out of said path so as to provide clearance for said end portion to move into said path and then for movement toward said point when the said end portion is out of said path for the guide apparatus to support a strand at said point.

2. The casting machine of claim 1 wherein said guide apparatus comprises a lower support surface for the underside of a strand and a guide unit mounted above said support surface in cooperative strand-supporting relative thereto, said guide unit having guide elements thereon for engaging the upper side of a strand, and said guide unit being mounted for movement generally parallel to the support surface in the longitudinal direction thereof, toward and away from said point.

8. The casting machine of claim 7 in which said movement of at least one of said units transversely of the path for the strand and toward said point brings said one of the units into engagement with the end portion of a dummy bar attached to a strand on said path and disconnects said dummy bar from said strand by moving said end portion of said dummy bar out of said path.

9. The casting machine of claim 7 which includes means for adjusting the spaced relation of the pair of guide units to vary the height of said strand receiving passage.

10. The casting machine of claim 7 which includes power means connected for moving the guide unit toward said point when said end portion of the dummy bar storage apparatus is moved out of the path of a strand at said point.

14. The casting machine of claim 11 including tie rods connected for joining the guide units together with spacers associated with said tie rods for varying the height of the strand receiving passage between the units.