Description:FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

1 TITLE OF THE INVENTION :
STEEL LADLE HAVING BOTTOM CONFIGURATION WITH FIN TYPE RECTANGULAR VORTEX BUSTERS TO REDUCE METAL LOSS IN 350 TON LADLE DURING TEEMING OF LIQUID STEEL.



2 APPLICANT (S)

Name : JSW STEEL LIMITED;

Nationality : An Indian Company.

Address : Dolvi Works, Geetapuram, Dolvi, Taluka Pen, Dist. Raigad, Maharashtra-402107,India; Having the Registered Office at
JSW CENTRE,BANDRA KURLA COMPLEX,BANDRA(EAST), MUMBAI-400051, STATE OF MAHARASHTRA, INDIA.




3 PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
Present invention is directed to Steel Ladle adapted for reducing metal loss in ladle during slag-free teeming of liquid steel from ladle to tundish, including a 350 T steel ladle having a less density slag layer thereon. More particularly, the present invention is directed to provide steel ladle with improved ladle bottom configuration involving fin type rectangular shaped vortex buster with 180° included anglenear the teeming nozzle in slope bottom steel ladles thereby delaying the vortex formation to prevent slag entrainment from ladle to tundish and eventually reduce the metal loss to 1.7 tons per heat, as compared to 8-9 tons of metal loss per heat in existing method.

BACKGROUND OF THE INVENTION:
Steelmaking process can be divided into two stages: (a) Primary steel making where carbon-rich liquid iron is converted into steel and (b) Secondary steel making which includes any post-primary steel making processes before casting. Finally, the steel is solidified through the casting process to obtain the desired end product.
Liquid steel is first produced in BOF by melting a mixture of liquid iron and scrap steel with oxygen blown into the furnace. Once the desired chemical composition and temperature are reached, the liquid steel from the BOF is transferred to a steel ladle. At the ladle furnace station, further refining processes are carried out to achieve the desired final steel chemistry with the preferred level of steel cleanliness. These processes may include the addition of slag formers, desulphurization, deoxidation, alloy addition, homogenization, inclusion modification, and inclusion flotation. During this process, liquid slag is produced by addition of slag formers, which act as a sink to the impurities generated in the process. The liquid slag is less denser as compared to liquid steel and floats above the liquid steel.
After processing in ladle furnace station, the steel ladles are moved to the caster where the liquid steel is poured into a tundish through a teeming nozzle located at the bottom of the steel ladles through a refractory tube called shroud. This practice is commonly known as liquid steel teeming process.
During the teeming of liquid steel, liquid slag can also be entrained when the liquid steel height is low inside the steel ladle. This phenomenon can happen through vortex formation by dragging the less denser slag while teeming of liquid steel. Vortex formation at the critical liquid height and drain sink formation during the final stages of teeming are reported as the prime mechanisms for slag entrainment. As the liquid steel flows, it creates a swirling motion due to the centrifugal forces or rotational velocity acting on the liquid. At the end of the teeming process, preferably when the liquid steel height is equal to the teeming nozzle diameter, drain sink can occur. The entrained steelmaking slag can hamper the subsequent casting process and cleanliness of steel will also be deteriorated. Hence, teeming of liquid steel is generally terminated early to avoid any entrainment of steelmaking slag into tundish. This practice however results in a considerable amount of leftover steel inside the steel ladle. This metal loss is considered as scrap which is subsequently reprocessed during the primary steelmaking process.
At present, there are two options available for steel ladles: flat-bottom ladles and slope-bottom ladles (see Figure 1). The slope-bottom ladles have a 4° angle that starts from a height of 40 mm on the ladle's side wall and extends to the well block. The capacity of these ladles is 350 tons. The side walls and bottom lining of the steel ladle are made of alumina spinel refractory material. The distance between the ladle center and teeming nozzle is 0.55R where R is the bottom radius of the ladle. The top diameter of well block of existing ladles is of 555 mm. Currently, following the teeming of liquid steel from steel ladle into tundish, approximately 7-8 tons of metal are left in the steel ladle.
At caster, during the teeming of liquid steel from ladle to tundish, slag entrains along with the stream of liquid steel when liquid steel bath height is low inside the steel ladle. This slag carry over happens due to vortexing and drain sink phenomena. Teeming is generally terminated early to avoid any entrainment of slag into tundish which results in leftover steel inside the steel ladle. This residual liquid steel is considered as “metal loss” which decreases the overall process yield.
Currently, in the two types of steel ladles namely, flat bottom steel ladles and slope bottom steel ladles total metal loss varies between8-9 tons per heat. Generally, the leftover steel in steel ladle is considered as scrap and it is reprocessed during primary steelmaking process which requires energy. Hence, the present invention targets to reduce metal loss and also the overall specific energy consumption.
Some relevant patent documents in the same filed revealing the state of the prior arts are summarized below:
Patent no. US 2009/0206528A1, titled “High yield ladle bottoms” discloses refractory bottom lining design for a steel ladle to increases the yield of slag-free steel and reduces the entrainment of slag into the stream of liquid metal during teeming. The upper surface of the bottom lining is composed of three sections: an uppermost section, an intermediate section and a lowermost section. Each section has an upper surface at a discrete elevation such that the highest elevation is found on the uppermost section, while the lowest elevation is on the lowermost section. These sections form a stepped pathway leading from the top to the bottom. To facilitate the drainage of molten metal from the steel ladle, there is an opening in the lowest section of the bottom lining. The bottom lining is consisting of a combination of a refractory castable and refractory bricks. This invention primarily focuses on stepped ladle bottom to prevent slag entrainment during teeming of liquid steel. No fin type straight vortex busters were explored in this invention to achieve the desired outcome.
Patent no. CN103949629A, titled “Ladle bottom structure capable of reducing continuous casting ladle cast residues” discloses a ladle bottom structure capable of reducing continuous casting ladle cast residues. The ladle bottom structure comprised of two flat surfaces with different height and a transition curved surface. A ladle outlet is provided on the flat surface with lower height. The ladle capacity is 120 tons. The steel ladles with new bottom structures are capable to reduce the residual steel quantity from 6.71 tons to 1.7 tons. No fin type straight vortex busters were explored in this invention to achieve the desired outcome.
Patent no. CN203484651U, titled “Continuous casting steel liquid ladle low in vortex and high in molten steel yield” discloses a steel ladle having refractory baffle which can reduce the critical height for vortex formation, thereby liquid steel yield can be improved. This invention considers only one baffle which is located between the teeming nozzle and the adjacent steel ladle refractory wall. The baffle height is 100-600 mm and thickness is 60-200 mm for a 300 tons capacity steel ladle. The baffle is made of calcareous or magnesia-alumina refractory material. The steel ladle bottom is flat.
Patent no. AU671182B2, titled “Flow control device for the suppression of vortices” discloses a flow control device comprising a baffle plate above teeming nozzle and radial dividers arranged in a radial pattern around a nozzle through which liquid steel is to be drained. Therefore, teeming nozzle is integral part of this device. The baffle plate is circular having a diameter which is at least six to eight times greater than the diameter of the teeming nozzle at the exit. The baffle plate has an eccentric hole relative to the longitudinal axis of the nozzle which can allow the nozzle to be filled with particulate material prior to draining of liquid steel. The teeming nozzle includes a rotatable flow obturator which regulate the flow of liquid steel. This invention does not specify whether the bottom of the ladle is flat or sloped.
Patent no. JP2000218362A, titled “Well block for preventing slag inclusion, and molten metal container, to which it is attached” discloses a well block which can prevent the occurrence of a molten metal vortex. This well block is comprised of a high alumina base part, high alumina projection parts which are integrated with the base part and a metal discharging nozzle. Therefore, the projection parts which are responsible for preventing the vortex are integral part of the well block. The height of projection parts is 200 mm from the bottom surface of the container main body. The invention is not only specific to steel ladle, but also applicable tundish or similar type of containers. The shape of the projection parts can be rectangular parallelepiped type or corrugated column type. However, the shape and size of the projection parts are not particularly limited as long as it can suppress the vortex formation. The number of the projection parts provided on the base is also not particularly limited and is usually four. This invention does not specify whether the bottom of the ladle is flat or sloped.
Patent no. CN112207268B, titled “Circular vortex-resisting device for bottom of steel ladle” discloses a device intended to counteract circular vortex formation in the lower part of a steel ladle to reduce steelmaking slag in the steel ladle from entering a tundish so as to improve the quality of steel and it includes three components (bottom, middle and upper part) arranged in a sequential order from the bottom to the top. The bottom part is in the shape of a cylinder and contains a central through hole in the middle. On the outside of the lower section, there is a concave outer fixing groove, while on the inside, there is a convex inner fixing groove. The middle part is a round table with a smaller upper segment and a larger lower segment. Notably, the round table is equipped with a second central through hole. The upper part of the device is a cylinder which is provided with a third central through hole. The central axes of the first central through hole, the second central through hole and the third central through hole are on the same straight line. Therefore, the discharging nozzle is integral part of the device. This invention does not specify whether the bottom of the ladle is flat or sloped.
Patent no. CN113042721B, titled “Dam-shaped vortex-resisting device for bottom of ladle” discloses a dam-shaped vortex-resisting device for the bottom of a ladle. The size of this device is as follows: thickness 150-350 mm, height 400-850 mm and width 350-650 mm. Semicircular stabilizing grooves having radius 50-130 mm which are penetrated front and back are symmetrically arranged between the upper bottom edges of the left and right surfaces. This device can be used at the ladle bottom to reduce the critical height for vortex formation. This invention does not specify whether the bottom of the ladle is flat or sloped. The installation location of this device with respect to the teeming nozzle location has not been mentioned.

OBJECTS OF INVENTION:
The basic object of the present invention is directed to steel ladle having bottom configuration adapted for reducing the metal loss in steel ladle having 4oslope bottom with two fin type rectangular shaped straight vortex busters having 180° included angle to reduce metal loss in ladle during slag-free teeming of liquid steel from ladle to tundish, thereby increasing the process yield and reducing overall specific energy consumption.
A further object of the present invention is directed to a steel ladle having bottom configuration adapted for reducing the metal loss with two fin type rectangular shaped straight vortex busters separated by 180o included angle and placed perpendicularly with respect to the tangent of top peripheral surface of the well block but not integral part of the well block, thereby these vortex busters can be installed easily at the bottom of the steel ladle without any modification of existing flow control devices.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to Steel Ladle adapted for reducing metal loss in ladle during slag-free teeming of liquid steel from ladle to tundish comprising:

vortex busters disposed at the ladle bottom, said vortex busters comprising fin type vortex busters placed perpendicular with respect to the tangent of top peripheral surface of well block for effectively suppressing rotational velocity of fluid near teaming nozzle and thereby reducing metal loss in steel ladle during teeming process.

A further aspect of the present invention is directed to said steel ladle comprising

said steel ladle having a sloped ladle bottom with 30 to 50 preferably about 40 slope bottom with two fin type rectangular shaped vortex buster having 1800 included angles to reduce metal loss in ladle during slag-free teeming of liquid steel from ladle to tundish for increasing process yield and reducing overall energy consumption.

A still further aspect of the present invention is directed to said steel ladle comprising two fin type rectangular shaped straight vortex busters with dimensions of 180 mm to 220mm preferably about 200 mm in length, 80 mm to 120 mm preferably about 100 mm in height and 25 mm to 75 mm. preferably about 50 mm in width, separated by 180o included angle and placed perpendicularly with respect to the tangent of top peripheral surface of the well block.

A still further aspect of the present invention is directed to said steel ladle wherein said fin type rectangular vortex busters are reasonably secured with respect to the well block, free of any modification of existing flow control devices.

A still further aspect of the present invention is directed to said steel ladle wherein ladle bottom configuration adapted to reduce metal loss in 350 ton ladle during teeming of liquid steel comprising

said steel ladle with slopped bottom having side walls and bottom lining of the steel ladle made of alumina spinel refractory material;

said slope at ladle bottom selectively provided from ladle's side wall and extends to a well block spaced apart from impact pad;

said well block having desired diameter and selectively disposed at said slopped ladle bottom in communication with a teeming nozzle below the ladle for delivering liquid steel to the tundish at caster;

said two fin type straight rectangular vortex busters disposed at 1800 included angle near to said well block adapted to reduce metal loss in steel ladle during teeming process.

Another aspect of the present invention is directed to said steel ladle wherein slope angle of 4° is maintained from 40 mm ladle side wall height to the well block connected to teeming nozzle.

Yet another aspect of the present invention is directed to said steel ladle wherein the well block diameter is maintained in the range from 500 mm to 600 mm preferably 555 mm for a slope bottom steel ladle.

A further aspect of the present invention is directed to said steel ladle wherein distance between the ladle center and teeming nozzle is 0.55R where R is the bottom radius of the ladle.

A still further aspect of the present invention is directed to said steel ladle wherein said fin type rectangular vortex busters are made of refractory material to withstand the steelmaking temperature.

A still further aspect of the present invention is directed to said steel ladle wherein said two fin type rectangular shaped vortex buster are adapted to effectively suppress the rotational velocity of fluid near the teeming nozzle, thereby delaying the vortex formation and helps to keep low quantity of retained liquid steel inside the steel ladle to a minimum of 1.7tons during slag-free teeming process.

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

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In Fig.1, A is the ladle wall, Fig.1 B shows the schematic of flat bottom design and Fig.1 C shows the schematic of slope bottom design.
In Fig.2, 1 shows the existing flat bottom of the ladle with 2 showing the impact pad, 3 showing the well block and 4 showing the teeming nozzle.
In Fig.3, 5 shows the existing ladle slope bottom.
In Fig.4, 6 shows the increased well block top diameter.
In Fig.5, 7 shows the increased slope inclination angle.
In Fig.6, 8 shows the application of two fin type rectangular shaped vortex buster with 180° included angle with existing slope bottom ladle.
In Fig.7, 8 shows the application of two fin type rectangular shaped vortex buster with90° included angle with existing slope bottom ladle.
In Fig.8, 9 shows the application of two fin type rectangular shaped vortex buster with180° included angle with existing flat bottom ladle.
In Fig. 9 shows graphical illustration of various Ladle design experimented vs. retained steel weight in the ladle (tons).

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
The present invention is directed to steel ladle having bottom configuration adapted for reducing the metal loss in steel ladle having 4oslope bottom with two fin type rectangular shaped straight vortex busters having 180° included angle to reduce metal loss in ladle during slag-free teeming of liquid steel from ladle to tundish, thereby increasing the process yield and reducing overall specific energy consumption.
At present, there are two options available for steel ladles: flat-bottom ladles and slope-bottom ladles as shown in accompanying Figure 1. The slope-bottom ladles have a 4° angle that starts from a height of 40 mm on the ladle's side wall and extends to the well block. The capacity of these ladles is 350 tons. The side walls and bottom lining of the steel ladle are made of alumina spinel refractory material. The distance between the ladle center and teeming nozzle is 0.55R where R is the bottom radius of the ladle. The top diameter of well block of existing ladles is of 555 mm.Currently, following the teeming of liquid steel from steel ladle into tundish, approximately 7-8 tons of metal are left in the steel ladle.
Computational fluid dynamic simulations have been done using Ansys Fluent software for multiple number of ladle bottom designs to find out the best design to reduce metal loss in steel ladle. Table 1 shows the details of different ladle bottom designs and corresponding identification number. Existing ladle bottom designs (flat and slope bottom) were considered for simulation to validate simulation results with actual plant data (metal loss data). Further the following modified ladle bottom designs were also considered for simulations: slope bottom ladle with changed well block diameter, slope bottom ladle with changed slope and flat and slope bottom ladle with two rectangular fin type straight vortex busters. Figures 2-8 show the different ladle bottom configurations trialed according to present invention.
A three-dimensional transient multiphase model has been considered for simulations. The adopted turbulence model is standard k-epsilon with enhanced wall treatment. The bottom of the steel ladle contains liquid steel and thin slag layer is present above the steel layer. Presence of air is considered above the slag phase. Properties of steel and slag (steel: density – 7020 Kg/m3, viscosity – 0.006 Pa.s; slag: density – 2786 Kg/m3, viscosity – 0.09 Pa.s) are considered at steelmaking temperature to represent actual scenario. Chemical reaction between steel and slag has not been modeled and constant steelmaking temperature has been considered for simulations. Volume of fluid (VOF) model with implicit scheme has been considered for simulations. Implicit body force formulation, sharp interface modelling and surface tension modelling with continuum surface model and wall adhesion have also been considered. Pressure outlet boundary condition considered at the top of the ladle and at teeming nozzle exit. Standard no slip stationary boundary condition considered at ladle walls. SIMPLE solver scheme has been considered for the pressure velocity coupling method. The results of simulation trials are given in following Table 1.
Table 1: Different simulation cases and corresponding design identification number
Design Type Modification Design Id
Existing flat bottom ladle Existing design FBD1
Existing slope bottom ladle Existing design SBD1
Modified slope bottom ladle Well block top diameter changed from 555 mm to 700 mm SBD2
Modified slope bottom ladle Slope changed with inclination angle of 8° SBD3
Modified slope bottom ladle two fin type rectangular shaped vortex buster with 180° included angle with existing slope bottom SBD4
Modified slope bottom ladle two fin type rectangular shaped vortex buster with 90° included angle with existing slope bottom SBD5
Modified flat bottom ladle two fin type rectangular shaped vortex buster with 180° included angle with existing flat bottom FBD2

Simulation results (see Figure 9) show that the retained steel quantity is 8 tons and 7.5 tons for existing flat bottom (1) and slope bottom (5) ladle designs respectively. This observation is perfectly matching with the actual plant data which confirms the validation of the model. In case of SBD2, the well block (6) diameter was increased from 555 mm to 700 mm for a slope bottom steel ladle and in case of SBD3, the ladle bottom slope angle has been increased from 4o to 8oby maintaining 80 mm ladle side wall height to the well block. In both cases SBD2 and SBD3 show some improvement to retain lower amount of liquid steel 5.7 tons and 6.2 tons respectively inside the steel ladle for slag-free teeming process. Further a new design of using a fin type vortex buster at the ladle bottom was explored. In cases SBD4 and SBD5, where the steel teeming process with two fin type rectangular shaped vortex busterwith included angle of 180°(8) and 90° (9) was simulated. The best ladle bottom design in terms of retaining lowest liquid steel quantity (1.7 tons)was slope bottom ladle with two fin type rectangular shaped straight vortex busters with 180° included angle(SBD4). In case of FBD2, two fin type rectangular shaped vortex busterwas applied but the metal retained was 8 tons.
So, the application of two fin type rectangular shaped vortex buster with 180° included angle in the existing slope bottom design yield the best result with 1.7 tons. These vortex busters are separated by 180o included angle and located at the periphery of top well block part. However, these vortex busters are not integral part of the well block and placed perpendicularly with respect to the tangent of top peripheral surface of the well block. The dimensions of each vortex busters are as follows: length – 200 mm, height – 100 mm and width – 50 mm. These vortex busters should be made of refractory material to withstand the steelmaking temperature. These two fin type rectangular shaped vortex buster can effectively suppress the rotational velocity of fluid near the teeming nozzle, thereby delaying the vortex formation. It helps to keep low quantity of retained liquid steel inside the steel ladle during slag-free teeming process. Consequently, this particular ladle bottom design has the potential to enhance the overall process yield. Typically, the excess steel present in the steel ladle is regarded as scrap and undergoes reprocessing in the primary steelmaking process, which consumes energy. As a result, this design has the ability to decrease the overall specific energy consumption.
Therefore, simulation study results show that the slope bottom ladle (slope angle of 4° maintained from 40 mm ladle side wall height to the teeming nozzle) with two fin type rectangular shaped straight vortex busters having 180° included angle is the best ladle bottom design to reduce metal loss in steel ladle during teeming process. Plant trials have been planned with this design and same result is confirmed from this plant trial.

, Claims:We Claim:

1. Steel Ladle adapted for reducing metal loss in ladle during slag-free teeming of liquid steel from ladle to tundish comprising :

vortex busters disposed at the ladle bottom, said vortex busters comprising fin type vortex busters placed perpendicular with respect to the tangent of top peripheral surface of well block for effectively suppressing rotational velocity of fluid near teaming nozzle and thereby reducing metal loss in steel ladle during teeming process.

2. The steel ladle as claimed in claim 1 comprising

said steel ladle having a sloped ladle bottom with 30 to 50 preferably about 40 slope bottom with two fin type rectangular shaped vortex buster having 1800 included angles to reduce metal loss in ladle during slag-free teeming of liquid steel from ladle to tundish for increasing process yield and reducing overall energy consumption.

3. The steel ladle as claimed in anyone of claims 1 or 2 comprising two fin type rectangular shaped straight vortex busters with dimensions of 180 mm to 220mm preferably about 200 mm in length, 80 mm to 120 mm preferably about 100 mm in height and 25 mm to 75 mm preferably about 50 mm in width, separated by 180o included angle and placed perpendicularly with respect to the tangent of top peripheral surface of the well block.

4. The steel ladle as claimed in anyone of claims 1 to 3 wherein said fin type rectangular vortex busters are reasonably secured with respect to the well block, free of any modification of existing flow control devices.

5. The steel ladle as claimed anyone of claims 1 to 4 wherein ladle bottom configuration adapted to reduce metal loss in 350 ton ladle during teeming of liquid steel comprising

said steel ladle with slopped bottom having side walls and bottom lining of the steel ladle made of alumina spinel refractory material;

said slope at ladle bottom selectively provided from ladle's side wall and extends to a well block spaced apart from impact pad;

said well block having desired diameter and selectively disposed at said slopped ladle bottom in communication with a teeming nozzle below the ladle for delivering liquid steel to the tundish at caster;

said two fin type straight rectangular vortex busters disposed at 1800 included angle near to said well block adapted to reduce metal loss in steel ladle during teeming process.

6. The steel ladle as claimed in anyone of claims 1 to 5 wherein slope angle of 4° is maintained from 40 mm ladle side wall height to the well block connected to teeming nozzle.

7. The steel ladle as claimed in anyone of claims 1 to 6 wherein the well block diameter is maintained in the range from 500 mm to 600 mm preferably 555 mm for a slope bottom steel ladle.

8. The steel ladle as claimed in anyone of claims 1 to 7 wherein distance between the ladle center and teeming nozzle is 0.55R where R is the bottom radius of the ladle.

9. The steel ladle as claimed in anyone of claims 1 to 8 wherein said fin type rectangular vortex busters are made of refractory material to withstand the steelmaking temperature.

10. The steel ladle as claimed in anyone of claims 1 to 9 wherein said two fin type rectangular shaped vortex busterare adapted to effectively suppress the rotational velocity of fluid near the teeming nozzle, thereby delaying the vortex formation and helps to keep low quantity of retained liquid steel inside the steel ladle to a minimum of 1.7tons during slag-free teeming process.

Dated this the 10th day of July, 2023
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199