Claims:We Claim:

1. A system for controlled centering and alignment of a submerged entry nozzle (SEN) in the mold in continuous caster comprising:

a movable tundish car support structure with the tundish and carrying the submerged entry nozzle for movably and selectively positioning the said submerged entry nozzle in said mold thereunder;
at least two non contact laser sources/sensors mounted on said tundish car structure such as to extend into said mold for said submerged disposition of the said submerged entry nozzle in said mold
said non contact laser sources/sensors on either side of mold adapted to generate a laser line enabling precise centering of the SEN in the center of the mold and also align the SEN port parallel to the narrow face of the mold at start of a cast.
2. A system as claimed in claim 1 wherein said non contact laser sources/sensors are adapted to provide laser beam directed to rectangular SEN ports from either side;

centre of the ports on the SEN duly marked separately over the ports for matching with laser beam for the purpose of centering;
means to provide controlled lateral movement of tundish car to match port centers of SEN marked thereon with the laser beam directed from either side of the mold for precise centering and alignment;
means to lock the position of the tundish car as the beam on either side matches the marked centre line on the SEN before casting is started.
3. A system as claimed in anyone of claims 1 or 2 wherein two lasers are fixed to match on the central line of the mold and laser beams directed from either side of tundish car coincide with each other at the centre of the car.

4. A system as claimed in anyone of claims 1 to 3 wherein laser beams can be point or line and source gun is rigidly fixed to the car structure, to avoid misalignment during the car movement and jerks.

5. A system as claimed in anyone of claims 1 to 4 which ensures centering even during the casting involving said non contact sensors.

6. A system as claimed in anyone of claims 1 to 5 is not affected by the dust and heat generated during the casting and ensures all time accuracy.

7. A method for controlled centering and alignment of a submerged entry nozzle (SEN) in the mold in continuous caster involving the system as claimed in claims 1 to 5 comprising

placing tundish with SEN on tundish car;
marking centre of the ports on the SEN separately over the ports using a scale and a marker;
lowering centre marked SEN into the mold and directing the laser beams from laser source/sensors fixed on the tundish car structure on either side of the mold to match the centres of the SEN port marked thereon by adjusting the lateral movement of the tundish car;
locking the the position of the tundish car when beam on either side matches the marked centre line on the SEN, before casting is started.
8. A method as claimed in claim 7 wherein two laser beams are used to ensure centering from either side and avoid misalignment.

9. A method as claimed in anyone of claims 7 or 8 ensures SEN equally spaced from mold wider face and SEN ports parallel to the narrow face of the mold.

10. A method as claimed in anyone of claims 7 to 9 wherein centering can be maintained even during the casting as the process uses non contact sources.

11. A method as claimed in anyone of claims 7 to 10 wherein any misalignment during the SEN ramping can be also be adjusted during the casting using the laser beam centering method.

12. A method as claimed in anyone of claims 7 to 11 ensure uniform fluid flow in the mold, reduced turbulences and lower temperature variations.

13. A method as claimed in anyone of claims 7 to 12 ensure a significant reduction in entrapment defects (resulting from turbulent surface), vortexing, temperature variation alarms and casting stoppages.

14. A method as claimed in anyone of claims 7 to 13 providing a simple SEN centering technique without any operator or machine errors.

Dated this the 4th day of July, 2016
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

, Description:FIELD OF THE INVENTION
The present invention relates to a system for controlled centering and alignment of a submerged entry nozzle (SEN) in the mold using non-contact laser sensors and a method of such alignment where laser line is matched to the centre of the SEN and centre of the mold to perfectly align them at the start of the cast to keep the SEN ports parallel to the narrow face of the mold. The developed alignment process utilizes a set of two laser sensors fixed on the tundish car on the either side in a straight axis. The system and method according to the present invention ensure precise alignment of SEN and mold enabling symmetric fluid flow in the mold region of continuous casters so that Rectangular outlet port would distribute liquid steel more evenly without touching the wide faces while casting a narrow section causing least disturbances to the liquid metal level meniscus. The accurate positioning of the SEN governs the fluid flow in the mold which in-turn controls the inclusion flotation, meniscus turbulence and development of uniform solidification front.

BACKGROUND OF THE INVENTION
At continuous casting, steel flows from the tundish to the mold through a submerged entry nozzle, SEN. This protects the molten steel from reoxidizing in contact with the atmosphere. The flow rate is controlled with a gate or stopper rod to maintain optimum casting conditions. SEN is fixed to a movable tundish car and Mold is fixed on the caster platform. At the start of the casting, the tundish car is moved above the mold and the SEN is centered and lowered in to the mold. SEN Alignment in the mold plays a vital role in a continuous casting mold. It governs the fluid flow pattern inside the mold, which in turn, dictates the quality and productivity of the process. Misalignment of metal-delivery systems on either of the axis, can cause asymmetric fluid flow in the mold region of continuous casters, leading to abnormal surface turbulence, insufficient superheat transport to the meniscus, slag entrainment, inclusion entrapment, and other quality problems. Till date in all casters the SEN is centered manually which is error prone, vary between operators and results in frequent misalignment issues.

In the continuous casting process liquid steel flows out of the ladle into the tundish and then is fed into a water-cooled copper mold. Solidification begins in the mold, and continues through the caster. In continuous caster, the tundish sits on a movable tundish car which is used to position the tundish for pre-heating before the start of the casting and later position it over the mold for casting. The tundish car is hydraulically driven and operated manually for its positioning. SEN (submerged entry nozzle) is attached to the tundish and is also pre-heated before the casting. The submerged entry nozzle (SEN) is used to transport the molten steel from a tundish to a mold. The main purpose of its usage is to prevent oxygen and nitrogen pick-up by molten steel from the gas. Furthermore, to achieve the desired flow conditions in the mold. The SEN has 2 rectangular holes or ports symmetrically opposite position embedded in a vertical cylindrical nozzle at the bottom having a tapered bore for equally distributing the metal in the mold. Rectangular outlet port would distribute liquid steel more evenly without touching the wide faces while casting a narrow section. A downward angled port impinges liquid steel deep into the mold. This would cause least disturbances to the meniscus. At the start of the casting the tundish car is moved and the SEN is brought over and lowered into the mold. The SEN is centered in the mold and ports are kept parallel to the narrow face by the operator by visual inspection. The operator vary the lateral movement, for placing SEN in mold such that it is equally spaced between wider and narrow mold walls, or the rectangular opening and having desired SEN port hole orientation parallel to the narrow face of the mold. The accurate positioning of the SEN governs the fluid flow in the mold which in-turn controls the inclusion flotation, meniscus turbulence and development of uniform solidification front. However, this operator dependent centering and alignment in not always accurate and frequently results in off-centring and misalignment.

Off centering or misalignment of SEN results in fluctuations of the top surface, the transport of superheat, meniscus freezing, shell thinning from the jet impinging upon the solidifying shell, thermal stress, and crack formation. The entrainment of mold slag due to excessive surface velocities and level fluctuations is one of the most important causes of defects found in steel products. High speed surface flows or asymmetrical flow in the mold also induces vortices near the SEN which entraps slag deep into the slab. With the SEN deviation from the centerline of the mold, the vortexing zone is gradually increased because of a stronger biased flows. Asymmetrical flow in the mold also results in non-uniform temperature distribution or heat transfer on the mold surface leading to shell thinning on one side. This can even lead to break-out and casting stoppages. With increasing the production with higher casting speeds, it becomes important to keep uniform fluid flow in the mold by developing a new and more reliable method of SEN centering in the mold.

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to a system for precise controlled centering and alignment of a submerged entry nozzle (SEN) in the mold using non-contact laser sensors and a method of such alignment where laser beam is matched to the centre of the SEN and centre of the mold to perfectly align them at the start of the cast.

A further object of the present invention is directed to a system and method for controlled centering and alignment of a submerged entry nozzle (SEN) in the mold using non-contact laser sensors wherein the system ensures SEN equally spaced from mold wider face and SEN ports parallel to the narrow face of the mold.

A still further object of the present invention is directed to a system and method for controlled centering and alignment of a submerged entry nozzle (SEN) in the mold using non-contact laser sensors to ensure uniform fluid flow in the mold, reduced turbulences and lower temperature variations.

A still further object of the present invention is directed to a system and method for accurate alignment of a submerged entry nozzle (SEN) in the mold using non-contact laser sensors favouring significant reduction in entrapment defects (resulting from turbulent surface), vortexing, temperature variation alarms and casting stoppages.

A still further object of the present invention is directed to a system and method for accurate alignment of a submerged entry nozzle (SEN) in the mold using non-contact laser sensors wherein any misalignment during the SEN ramping can also be adjusted during the casting using the laser beam centering method.

A still further object of the present invention is directed to a system and method for accurate alignment of a submerged entry nozzle (SEN) in the mold using non-contact laser sensors wherein the system performance and reliability is not affected by the dust and heat generated during the casting and ensures all time accuracy without any operator or machine errors, which was not possible with manual centering method.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a system for controlled centering and alignment of a submerged entry nozzle (SEN) in the mold in continuous caster comprising:

a movable tundish car support structure with the tundish and carrying the submerged entry nozzle for movably and selectively positioning the said submerged entry nozzle in said mold thereunder;
at least two non contact laser sources/sensors mounted on said tundish car structure such as to extend into said mold for said submerged disposition of the said submerged entry nozzle in said mold
said non contact laser sources/sensors on either side of mold adapted to generate a laser line enabling precise centering of the SEN in the center of the mold and also align the SEN port parallel to the narrow face of the mold at start of a cast.

A further aspect of the present invention is directed to said system wherein said non contact laser sources/sensors are adapted to provide laser beam directed to rectangular SEN ports from either side;
centre of the ports on the SEN duly marked separately over the ports for matching with laser beam for the purpose of centering;
means to provide controlled lateral movement of tundish car to match port centers of SEN marked thereon with the laser beam directed from either side of the mold for precise centering and alignment;
means to lock the position of the tundish car as the beam on either side matches the marked centre line on the SEN before casting is started.
A still further aspect of the present invention is directed to said system wherein two lasers are fixed to match on the central line of the mold and laser beams directed from either side of tundish car coincide with each other at the centre of the car.

A still further aspect of the present invention is directed to said system wherein laser beams can be point or line and source gun is rigidly fixed to the car structure, to avoid misalignment during the car movement and jerks.

Another aspect of the present invention is directed to said system which ensures centering even during the casting involving said non contact sensors.

Yet another aspect of the present invention is directed to said system which is not affected by the dust and heat generated during the casting and ensures all time accuracy.

A further aspect of the present invention is directed to a method for precise centering and alignment of a submerged entry nozzle (SEN) in the mold in continuous caster involving the system as described above comprising
placing tundish with SEN on tundish car;
marking centre of the ports on the SEN separately over the ports using a scale and a marker;
lowering centre marked SEN into the mold and directing the laser beams from laser source/sensors fixed on the tundish car structure on either side of the mold to match the centres of the SEN port marked thereon by adjusting the lateral movement of the tundish car;
locking the position of the tundish car when beam on either side matches the marked centre line on the SEN, before casting is started.
A still further aspect of the present invention is directed to said method wherein two laser beams are used to ensure centering from either side and avoid misalignment.

A still further aspect of the present invention is directed to said method that ensures SEN equally spaced from mold wider face and SEN ports parallel to the narrow face of the mold.

Another aspect of the present invention is directed to said method wherein centering can be maintained even during the casting as the process uses non contact sources.

Yet another aspect of the present invention is directed to said method wherein any misalignment during the SEN ramping can be also be adjusted during the casting using the laser beam centering method.

A further aspect of the present invention is directed to said method that ensure uniform fluid flow in the mold, reduced turbulences and lower temperature variations.

A still further aspect of the present invention is directed to said method which ensure a significant reduction in entrapment defects (resulting from turbulent surface), vortexing, temperature variation alarms and casting stoppages.

A still further aspect of the present invention is directed to said method providing a simple SEN centering technique without any operator or machine errors.

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to the following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1: Shows the Schematic arrangement of Tundish, SEN and Mold in a conventional continuous caster.
Figure 2: shows the ideal positioning of SEN in relation to Mold walls.
Figure 3: shows the Off-centre positioning of SEN in Mold which needs to be avoided.
Figure 4: shows the Misaligned positioning of SEN in Mold which should be avoided.
Figure 5: shows the Centering of SEN in mold using non contact lasers sensors mounted on Tundish car.
Figure 6: shows the photo image of SEN and laser system according to present invention mounted on Tundish car.
Figure 7: shows an illustration of SEN centering method using laser beam.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The present invention is directed to a system for controlled centering and alignment of a submerged entry nozzle (SEN) in the mold using non-contact laser sensors and a method of such alignment where laser beam is matched to the centre of the SEN and centre of the mold to perfectly align them at the start of the cast to ensure uniform fluid flow in the mold, reduced turbulences and lower temperature variations. Importantly also, using the system and method according to the present invention, any misalignment during the SEN ramping can also be adjusted during the casting using the laser beam centering method.

Referring first to accompanying Figure 1, wherein a schematic arrangement of tundish, SEN and mold has been shown in the continuous casting process where liquid steel flows out of the ladle into the tundish and then is fed into a water-cooled copper mold. Solidification begins in the mold, and continues through the caster. In continuous caster, the tundish sits on a movable tundish car which is used to position the tundish for pre-heating before the start of the casting and later position it over the mold for casting. The tundish car is conventionally hydraulically driven and operated manually for its positioning which introduces various types of error and mismatch.

The operator vary the lateral movement, for placing SEN in mold such that under ideal position as shown in Figure 2, it is equally spaced between wider and narrow mold walls, or the rectangular opening and having desired SEN port hole orientation parallel to the narrow face of the mold. The accurate positioning of the SEN governs the fluid flow in the mold which in-turn controls the inclusion flotation, meniscus turbulence and development of uniform solidification front.

However, this operator dependent centering and alignment is not always accurate and frequently results in off-centring and misalignment. Off centering as shown in Figure 3 or misalignment as shown in Figure 4 of SEN results in fluctuations of the top surface, the transport of superheat, meniscus freezing, shell thinning from the jet impinging upon the solidifying shell, thermal stress, and crack formation.

The present invention thus provides a solution to above stated problems associated with conventional positioning of tundish subentry nozzle in relation to mold opening by a innovative system and method wherein the manual error is totally eliminated by incorporating laser sensor based non contact positioning system that avoids reliance on human accuracy such that cast product quality as well as productivity is improved by avoiding unwanted variation in operational parameters leading to casting defects or even break-out and casting stoppages when operating at high casting speeds.

According to a basic aspect of the present invention, the same is directed to a system and method for precise centering and alignment of SEN in the mold for uniform fluid/liquid metal flow in the mold. It is an object of the present invention to centre the SEN using two non-contact laser sensors mounted on the tundish car.

Accordingly, the system of the present invention involves fixing two laser source/sensors(1) on the tundish car structure on either side of the mold(4). The two lasers(1) are fixed to match on the central line of the mold as shown in accompanying Figure 5. The laser beams(2) coincide with each other at the centre of the car. Two beams are used to ensure centering from either side and avoid alignment. The laser beams can be point or line and source gun is rigidly fixed to the car structure, to avoid misalignment during the car movement and jerks. The centre of the ports on the SEN(3) is marked separately over the ports using a scale and a marker.

According to the method of the invention, the laser beam on the either side of tundish car is used to match to each of the centre marked on either side of the SEN and centre of the mold as shown in Figure 6 to perfectly align them at the start of the cast. First the centre marked SEN is lowered into the mold and the laser beam is put to match the centre of the SEN by adjusting the lateral movement of the tundish car. As the beam on either side matches the marked centre line on the SEN as can be seen accompanying Figure 7, the position of the tundish car is locked and casting is started. This system ensures centering even during the casting, as the process uses non contact sources. Any misalignment during the SEN ramping can also be adjusted during the casting using the laser beam centering method. This system in not affected be the dust and heat generated during the casting and ensures all time accuracy, which was not possible with manual centering method.

This new system ensures SEN equally spaced from mold wider face and SEN ports parallel to the narrow face of the mold. This new method of SEN centering is a simple technique without any operator or machine errors.

It is thus possible by way of the present invention to provide a system and method for controlled centering and alignment of a submerged entry nozzle (SEN) in the mold using non-contact laser sensors and a method of such alignment where laser beam is matched to the centre of the SEN and centre of the mold to perfectly align them at the start of the cast or even during casting, in order to uniform fluid flow in the mold, reduced turbulences and lower temperature variations. There has been a significant reduction in entrapment defects (resulting from turbulent surface), vortexing, temperature variation alarms and casting stoppages with use of the new centering method. The system and method of the invention is simple yet reliable to ensure improved productivity and quality in continuous caster avoiding casting defects or even break-out and casting stoppages when operating at high casting speeds.