Title of Invention	AN IMPROVED DEVICE FOR STOPPING PRIMARY SLAG CARRY OVER.
Abstract	An improved device to preferentially block carry over slag during tapping of steel from converters which comprises a plurality of steel discs or fins (1,2,3 ) of varying diameter attached to a pipe or tube (4). The device is adapted to melt on contact with molten steel and thus preferentially block carry over slag. It is easy to be inserted even from a distance.

Full Text

Field of Invention The present invention relates to a device for preferentially blocking slag carry over. The device is a converter tap hole plug which comprises plurality of circular steel discs of varying diameter attached to a steel tube. The said device is adapted to melt on contact with molten steel and thus block initial carry over slag. Description of Known Art Tapping of steel from primary steel making vessel like basic oxygen furnaces (BOF) and electric are furnaces (EAF) is associated with carry over slag (CO slag) flow into teeming ladle. CO slag having high oxygen potential and high impurity content have many deleterious effects Properties of final steel products are affected by ladie slag properties that in turn gets affected by the quantity of carry over slag because of its high oxygen potential and impurity content. Normally the steel properties like inclusion content and morphology, total oxygen content, sulfur content, phosphorous reversal and operating a parameters like electrical are stability and heating efficiency in ladle furnace/Vacuum Arc Degassing, ladle refractory wear, alloy recovery etc. are directly or indirectly affected by the quantity of CO slag. The total quantity of CO slag that flow into ladle during tapping may be divided into three parts. o Initial slag carry over: slag that flow into ladle at the start of tapping during converter tilting constitutes 20-25% of total CO slag quantity. o Middle slag carry over: slag that flow into ladle due to vortex formation in primary vessel during tapping amounting to 50-60% of total carry over slag. o Final slag carry over: slag that flow during slow tilting back of tapping vessel constituting the rest of total carry over slag. The growing quality requirements in final product necessitate the need to control the quantity of carry over slag into the steel ladle. Hence, continued efforts are on to develop new slag stopping devices or improve the existing one. For stopping the initial slag plug type devices like ceramic or refractory plug or gunny bag soaked with binders are used. For stopping the middle slag DART, 2 refractory floating balls etc. are put into operation during tapping to stop the drainage of slag through vortex formation. Similarly to stop end slag pneumatic slag stoppers, slide gates on taps hole, optical sensors connected with quick tilting back of steel making vessel etc. are being used. In India only middle or end slag stopping devices like DART, pneumatic slag stoppers, slide gates at tap hole are used to stop slag carry over. For restricting initial slag carry over primarily refractory or ceramic plugs or gunny bag are used in different plants abroad but rarely in India. These initial slag stopping devices are fitted inside the tap hole just before the commencement of tapping. These plugs are either burnt or melt in contact with steel after blocking the initial slag during tapping. However, use of these plugs is associated with major disadvantages like tap hole jamming resulting delay in tapping and loss of unit productivity; becoming loosely fit into tap holes with use as tap hole diameter increases and forced out at the start of tapping; and fitting into tap hole is cumbersome. Objects of the Invention Thus the basic object of the present invention is to provide an improved device adapted to preferentially block carry over slag during tapping of steel from converters comprising a plurality of steel discs or fins of varying diameter attached to a pipe or tube. Another object of the present invention is to provide a device to block carry over slag such that it would melt in contact with the molten steel. A further object is to provide a device to block carry over slag, which is easy to [insert and is cost effective. Summary of the invention Thus according to the main aspect of the present invention there is provided an improved device adapted to preferentially block carry over slag during tapping of steel from converter comprising a plurality of steel discs or fins of varying diameter attached to a pipe or tube. 3 Detailed Description of the Invention The present inventors have now found an improved device for preferentially blocking the carry over slag comprising a plurality of steel discs of varying diameter attached to a pipe which is adapted to melt in contact with molten steel. The device is a quick melting converter tap hole plug, made of circular steel discs attached to a steel tube. Thus it selectively allows only molten steel to pass through. The problem of increase in internal diameter of the tap hole converter with the increase in tap hole life is effectively taken care of by the plurality of steel discs of varying diameters. The device of the present invention is an assembly of three circular discs. The discs are made of 0.05 to 1.0mm, preferably 1.0 mm thick steel sheet of increasing diameter welded with the help of washer on a steel pipe that runs through the center of these discs. The edges of the discs are provided with slits or cuts to enable the device to fit firmly in the tap hole. The device is light weight (for 300 ton BOF weighs about 2 kg.) and easy to handle and insert and is cost effective. The discs melt within a range of 0-10 seconds after it comes in contact with liquid steel and do not cause tap hole jamming. After steel melting is complete in converters, it is tapped into ladle through a tap hole (located at the top side of the converter) by tilting the converter slowly. During tapping of steel, slag also flow into ladle as an undesirable liquid through the same tap hole with steel. Inside the converter, slag float atop the steel due to density difference and during converter tilting it reaches the tap hole before steel and flow into the ladle (if the tap hole is not blocked preferentially for slag). Just before tapping, the device of the present invention is inserted into the tap hole of the converter with the help of an insertion rod. Insertion is done after mounting the device on a steel rod of suitable diameter and after the device is inserted into tap hole tapping of steel commences. The external diameter of the insertion rod matches with the internal diameter of central steel pipe of slag stopper. During tapping the device blocks the slag preferentially but when steel reach the tap hole the discs melt in contact with steel and allow only steel to flow out of tap hole into the teeming ladle restricting initial slag flow. 4 The present device effectively stops the initial slag carry over to nil and takes care of increasing tap hole diameter with increasing diameter of circular discs. As the slag stopper is inserted with an insertion rod, it can be fitted into the tap hole from a distance (from converter floor), with ease and safety. The invention is now explained with respect to illustrative non-limiting accompanying drawings. Brief Description of the accompanying drawings Fig. 1: The isometric view of the device of the present invention. Fig 2a: Elevation of the device of present invention used in 300ton converter of SMS-II, BSL Fig 2b: Plan view of the device of present invention used in 300ton converter of SMS-II, BSL Fig 2c: Detail of a disc/fin (3) of the device of present invention used in 300ton converter of SMS-II, BSL Fig. 2d: Detail of washer (8) of present invention used in 300ton converter of SMS-II, BSL Fig. 2e: Detail of central pipe (4) of present invention used in 300ton converter of SMS-II, BSL Detailed Description of the Accompanying Drawings Fig 1: The device of the present invention is shown in isometric view having three circular discs or fins (1, 2, 3). The discs are so arranged that the smallest (1) is at the top and the largest (3) is at the bottom. The pipe or tube 4 runs through the center of the discs. The ridge (5) on the top of insertion rod (6) work as a seat for the device while transportation and insertion. The fitting of the device in the converter tap hole (7) is indicated. Fig. 2a: The device of the present invention used in 300ton converter of SMS-II, BSL is shown as elevation view. The diameter of the discs 1, 2, 3 are 180,200,210mm respectively. The discs are provided with slits at the edges. 3 has 5 16 slits while 2 and 1 have 10 each. The discs are equidistant from one another at a distance of 100mm. The pipe 4 passes through the disc and a washer (8) is present at each connection. Fig 2b: The device of the present invention used in 300ton converter of SMS-II is shown as plan view. The three discs of diameter of 180,200,210mm respectively are placed with the washer (8). Fig 2c: Details of a Disc (3) is of the device of the present invention used in 300ton converter of SMS-II, BSL is shown. The disc is 1 mm in thickness and has 16 slits. Depth of each slit is 25mm. The slits provide better grip of the discs inside tap hole and prevent slag carry over. Fig. 2d: Detail of washer (8). The washer has external diameter 72 and internal diameter 40mm. Fig. 2e: Detail of central pipe (4). The pipe has inner diameter of 24mm and outer diameter of 32mm. Using only DART (middle slag acting device) in this 300 ton BOF and measuring the resultant slag carry over through rod dip method, was shown to be between 14 and 16 kg/t of liquid steel. With the use of initial slag stopper of the present invention and DART working in tandem, slag carry over in 300ton converter of SMS-II, could be restricted to 6 We claim: 1) An improved device to preferentially block carry over slag during tapping of steel from converters which comprises a plurality of steel discs or fins of varying diameter attached to a pipe or tube; the pipe or tube runs through the center of the discs. 2) A device as claimed in claim 1 wherein the steel discs are adapted to melt within 0 to 10 seconds of contact with molten steel. 3) A device as claimed in claim 1 or 2 wherein the steel discs are made of 0.05 to 1.0 mm, preferably 1.0 mm thick steel sheet. 4) A device as claimed in any preceding claim wherein the arrangement of the steel discs is such that the smallest one is at the top and the largest one is at the bottom. 5) A device as claimed in any preceding claim wherein the arrangement of the steel discs is such that they are welded on to the said pipe that runs through their center. 6) A device as claimed in any preceding claim wherein the said device is adapted to block initial carry over slag by fitting onto the tap hole of the converter. 7) A device as claimed in any preceding claim wherein the said device is inserted into the tap hole of the converter with the help of an insertion rod. 8) A device as claimed in claim 6 wherein the internal diameter of the central pipe corresponds to the outer diameter of the said insertion rod. 7 9) A device as claimed in any preceding claim wherein the said discs are provided with slits on their edges such that the device fits firmly to the tap hole of the converter. An improved device to preferentially block carry over slag during tapping of steel from converters which comprises a plurality of steel discs or fins (1,2,3 ) of varying diameter attached to a pipe or tube (4). The device is adapted to melt on contact with molten steel and thus preferentially block carry over slag. It is easy to be inserted even from a distance.

Documents:

00009-kol-2004 abstract.pdf

00009-kol-2004 claims.pdf

00009-kol-2004 correspondence.pdf

00009-kol-2004 description(complete).pdf

00009-kol-2004 drawings.pdf

00009-kol-2004 form-1.pdf

00009-kol-2004 form-18.pdf

00009-kol-2004 form-2.pdf

00009-kol-2004 form-3.pdf

00009-kol-2004 letters patent.pdf

00009-kol-2004 p.a.pdf

9-KOL-2004-(01-02-2012)-FORM-27.pdf

9-KOL-2004-FORM 27.pdf