Claims:1. A method for continuously casting an article in a continuous casting process, the method comprising:
pouring molten metal from a tundish to a mould, wherein the mould is cooled by a primary cooling process and defines a passage through which molten metal flows and a layer of the molten metal in contact with walls of the mould solidifies forming the slab;
drawing the slab from an exit of the mould; and
subjecting, the slab to a secondary cooling process to further solidify molten metal inside the slab, the secondary cooling process includes:
spraying cooling fluid at:
a first intensity ranging from 2 ltrs/Kg/m to 4 ltrs/Kg/m up to a distance of 0.5 meters after the exit of the mould; and
a second intensity ranging from 0.75 ltrs/Kg/m to 2 ltrs/Kg/m up to a distance ranging from 0.5m to 1.5m after the exit of the mould,
wherein, the secondary cooling process arrest crack propagation in the slab and eliminates shape deformation of the slab.

2. The method as claimed in claim 1, wherein the secondary cooling process arrests the propagation of sub-surface off-corner cracks in the slab.

3. The method as claimed in claim 1, wherein the cooling fluid is sprayed onto the slab in form of at least one of air mist and jet spray.

4. The method as claimed in claim 1, wherein cross section of the mould is polygonal including square type and rectangular type.

5. The method as claimed in claim 4, wherein cross section of the mould is circular.

6. The method as claimed in claim 1, wherein the cooling fluid is sprayed onto each surface of the article.

7. The method as claimed in claim 1, wherein the cooling fluid is sprayed through a plurality of nozzles. , Description:TECHNICAL FIELD:

Present disclosure relates in general to a field of metallurgy. Particularly, but not exclusively, the present disclosure relates to continuous casting of articles. Further embodiments of the present disclosure are directed to a method for continuously casting of articles such as slabs, billets and blooms in the continuous casting process with improved cooling.

BACKGROUND OF THE DISCLOSURE:

Long continuous casting products are cast predominantly in tubular permanent molds with a rectangular, and often with an approximately square or round, cross-section. The billet, blooms, and slabs are then further processed by rolling or forging.

For producing continuous casting products with good surface and texture quality, in particular billet, bloom, and slabs, a uniform heat transition along the circumferential line of the slab cross-section between the slab being formed and the wall of the die cavity is of crucial importance. Many proposals are known for designing the geometry of the die cavity, in particular in the areas of the corner fillets of the die cavity, in such a way that no damaging air gaps arise between the slab shell being formed and the wall of the permanent mold, causing an uneven heat transition along a circumferential line of the slab cross-section and solidification defects and fractures.

The configuration of the edges/corners in the die cavity of the permanent mold makes it difficult to achieve a uniform cooling between a slab shell being formed and the walls of the permanent mold, in particular over the circumference of the die cavity. The incipient solidification of the slab just below the bath level in the permanent mold proceeds differently on straight sections of the circumference of the die cavity from the corner area. The heat flow on the straight or substantially straight sections is quasi, one-dimensional and follows the law of heat transmission through a flat wall. In contrast to this, the heat flow in the edged corner areas is two-dimensional and it follows the law of heat transmission through the wall.

The resulting slab shell is normally thicker in the corner areas at the start of solidification below the bath level than on the straight surfaces and begins to shrink sooner and more intensely. The result of this is that the slab shell lifts up irregularly from the wall of the permanent mold in the corner areas and air gaps form, which drastically impair the heat transmission. Not only does this impairment of the heat transmission delay the further growth of the shell, but it can even cause a re-fusion of already solidified inner layers of the slab shell. This fluctuating pattern of the heat flow cooling and re-heating leads to slab defects such as surface and internal cracks at the edges or in areas near the edges, and also cause defects such as rhomboidity, indents, etc. A re-fusion of the slab shell or larger longitudinal cracks can also lead to fractures.

The present disclosure is directed to overcome one or more limitations stated above or any other limitations associated with the conventional arts.

The information disclosed in this background of the disclosure section is only for enhancement of understanding of the general background of the disclosure and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of the conventional arts are overcome by an apparatus and a method as claimed and additional advantages are provided through the provision of apparatus and the method as claimed in the present disclosure.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment of the disclosure, a method for continuously casting an article in a continuous casting process is disclosed. The method includes pouring molten metal from a tundish to a mould. The mould is cooled by a primary cooling process and defines a passage through which molten metal flows and a layer of the molten metal in contact with the walls of mould solidifies forming the slab. Further, the slab is drawn from an exit of the mould. The method includes subjecting the slab to a secondary cooling process to further solidify molten metal inside the slab. The second cooling process includes spraying cooling fluid at a first intensity ranging from 2ltrs/Kg/m to 4ltrs/Kg/m up to a distance of 0.5 meters after the exit of the mould. Further, cooling fluid is sprayed at a second intensity ranging from 0.75ltrs/Kg/m to 2ltrs/Kg/m up to a distance ranging from 0.5 meters to 1.5 meters after the exit of the mould. The secondary cooling process arrest crack propagation in the slab and eliminates shape deformation of the slab.

In an embodiment of the disclosure, the secondary cooling process arrests the propagation of sub-surface off-corner cracks in the slab.

In an embodiment of the disclosure, the cooling fluid is sprayed onto slab in form of at least one of air mist and jet spray.

In an embodiment of the disclosure, cross section of the mould is polygonal including square type and rectangular type.

In an embodiment of the disclosure, cross section of the mould is circular.

In an embodiment of the disclosure, the cooling fluid is sprayed onto each surface of the article. The cooling fluid is sprayed through a plurality of nozzles.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

The novel features and characteristic of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

FIG.1 is a flow chart showing a method for continuously casting a slab in a continuous casting process, in accordance with an embodiment of the present disclosure.

FIG.2a and 2b is an exemplary illustration of formation of shell within a mould and deformation in the shell.
FIG.3 is an exemplary illustration of formation of sub-surface off-corner crack in the shell.

FIG 4 illustrate an exemplary image of a shell in which the subsurface crack is arrested.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent processes do not depart from the spirit and scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

Embodiments of the present disclosure discloses a method for continuously casting articles such as slab, billet, blooms and the like [hereinafter referred to as casted article] in a continuous casting process. Specifically, the present disclosure discloses optimizing operational parameters to eliminate shape deformation of the casted article. The present disclosure may be directed towards employing optimized secondary cooling parameters in the continuous casting process. The casted article of the present disclosure is drawn from an exit of the mould and may be subjected to the secondary cooling process which may include spraying cooling fluid at a first intensity and a second intensity. The first intensity of spraying cooling fluid may range from 2ltrs/Kg/m to 4 ltrs/Kg/m up to a distance of 0.5m from the exit of the mould. Further, the second intensity may range from 0.75ltrs/Kg/m to 2 ltrs/Kg/m up to a distance ranging from 0.5m to 1.5m after the exit of the mould. This optimized cooling schedule may ensure that the crack propagation in the casted article is arrested and rhomboidity or shape deformation is eliminated.

The terms “comprises…. a”, “comprising”, or any other variations thereof used in the specification, are intended to cover a non-exclusive inclusion, such that an assembly that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or method. In other words, one or more elements in an assembly proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the assembly.

Henceforth, the present disclosure is explained with the help of one or more figures of exemplary embodiments. However, such exemplary embodiments should not be construed as limitation of the present disclosure.

The following paragraphs describe the present disclosure with reference to FIG(s) 1 to 4b. In the figures, the same element or elements which have similar functions are indicated by the same reference signs. For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to specific embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the illustrated methods, and such further applications of the principles of the disclosure as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention pertains.

The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description. It is to be understood that the disclosure may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific method or steps illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hereinafter, preferred embodiments of the present disclosure will be described referring to the accompanying drawings. While some specific terms of “below”, “above”, or “along” and other terms containing these specific terms and directed to a specific direction will be used, the purpose of usage of these terms or words is merely to facilitate understanding of the present invention referring to the drawings. Accordingly, it should be noted that the meanings of these terms or words should not improperly limit the technical scope of the present invention.

Generally, a continuous caster may comprise of the following key elements including a ladle turret, a ladle, a tundish with or without a stopper rod, an entry nozzle, a mould, a roller contaminant section with additional cooling chambers, a withdrawing unit and a torch cutting apparatus. The continuous caster further includes a run out table that may be configured to receive continuous casted product. Molten metal such as steel from an electric arc furnace or a basic oxygen furnace may be tapped into the ladle and may be shipped to the continuous caster. This batch of molten metal may be used to cast several slabs, blooms, billets and the like, the process of forming the said articles are elucidated further in the present disclosure. Hereinafter, an exemplary continuous casting process may be elucidated with respect FIG.1.

Figure. 1 is an exemplary embodiment of the present disclosure illustrating a flowchart of a method for continuously casting slabs, billets, blooms and the like, the said components may hereinafter be referred to as casted article. The method is now described with reference to the flowchart blocks and is as below. The order in which the method is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject. The various processing steps are described in their respective order below:

At block 1, molten metal from an electric arc furnace or a basic oxygen furnace may be tapped into the ladle and may shipped to the continuous caster. The ladle may be placed into the casting position above the tundish by the turret. Further, the molten metal may be poured into the tundish, and then into the mould. In an embodiment, the mould is a tube mould and cross section of the mould may be polygonal including square type and rectangular type. In some embodiments, cross section of the mould may be circular. The molten metal may be poured into the mould through a submerged entry nozzle. In an embodiment, the submerged entry nozzle may be configured to regulate the molten metal flow rate and may provide precise control of the molten metal level in the mould. The mould may be cooled by a primary cooling means. The primary cooling means may be defined internally with the mould or may be provided externally. The primary cooling means may be designed with a plurality of channels configured to channelize cooling liquid around the mould. The cooling liquid used in the present disclosure may be water and the mould of the present disclosure may be a water-cooled mould. As shown in FIG.2a and 2b, as the molten metal moves down the mould (M) [i.e., cooled by primary cooling process] at a controlled rate, a layer of molten metal in contact with the walls of the mould solidifies forming an outer shell (S) defining the casted article [i.e., the outer shell of the molten metal becomes solidified].

Generally, during the solidification of molten metal within the mould, shape deformation especially, rhomboidity/off-squareness and bulging due to sub-surface off-corner cracks may be a major concern [which can be seen from FIG(s) 2a and 2b part 4]. The sub-surface cracks may be formed due to the non-uniform cooling at the mould, thermal shrinkage stresses, mechanical stresses, ferro static pressure etc. The sub-surface cracks are depicted in FIG.3 with reference made to letter C. Upon formation of crack inside the mould followed by subsequent flow of segregated liquid inside the crack, the solidification continues at the solid liquid interfaces as the casted article moves down the mould. Induction of further stresses inside the mould due to thermal or mechanical factors, it may get concentrated at the crack and be a weak zone. In case of high reheating or bulging at the exit of the mould, crack would continue to extend until it meets the diagonal and then proceed along the diagonal as it becomes the weakest zone due to segregated liquid at the dendritic confluence. The rate of solidification and shell thickness after crack arrest would this play a major role in determining which of the two competing events viz stress generation and strength due to continuously occurring new solidification-after-crack dominates. The cross section of the article is as shown in FIG. 4 depicts an arrested crack shell. The method of the present disclosure elucidated hereinafter may address the said problem in the casted article. Upon exiting the mould, the casted article enters a roller section [as shown at block 102]. The rollers aid in drawing the casted article out of the mould. The rollers draw the casted article on to a run out table of length ranging from 3m to 15m. In some embodiments, the shape of the casted article may resemble cross section of the mould.

At block 103, the casted article exiting the mould is further cooled by a secondary cooling means. The secondary cooling means include a plurality of nozzles that may be alternatively positioned with respect to plurality of rollers in the roller section. The casted article may be subjected to a secondary cooling process when the casted article is passed through the secondary cooling means. The secondary cooling process may be configured to spray cooling fluid such as water or air mist onto the casted article. In an embodiment, the cooling fluid may be sprayed in the form of air mist or jet spray and such cooling fluid may be sprayed on all the surfaces of the article. The secondary cooling process includes spraying the cooling fluid on to the casted article with a first intensity and a second intensity. The cooling fluid may be sprayed onto the casted article at the first intensity up to a distance of 0.5m after the exit of the mould. The first intensity of spraying the cooling fluid may range from 2ltrs/Kg/m to 4ltrs/Kg/m. Further, from 0.5m to 1.5m of the casted article, the cooling fluid may be sprayed at the second intensity ranging from 0.75ltrs/Kg/m to 2ltrs/Kg/m. Use of the secondary cooling process significantly increases heat extraction from the surface of the solidifying casted article. Also, the secondary cooling process may be capable of enduring thermal stresses of solidification and mechanical stresses due to weight of the liquid column inside the casted article. The secondary cooling process may arrest crack propagation in the casted article. The cracks arrested may be subsurface off-corner cracks. Also, the secondary cooling process eliminates shape deformation of the casted article.

In an embodiment, the method of according to the present disclosure ensure that the casted article such as billets, slabs, blooms etc. are formed without deformation. Also, due to the optimized cooling parameter, the propagation of off-corner cracks is arrested.

It is to be understood that a person of ordinary skill in the art may develop a system of similar configuration without deviating from the scope of the present disclosure. Such modifications and variations may be made without departing from the scope of the present invention. Therefore, it is intended that the present disclosure covers such modifications and variations provided they come within the ambit of the appended claims and their equivalents.

Equivalents

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding the description may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated in the description.

Referral Numerals:
Description Reference number
Flow chart 101-103
Mould M
Outer shell S
Crack C