Field of invention: This invention relates to slide gate plates and ladle or collector nozzle, refractory design. The present invention particularly relates to Slide Gate Plates and ladle or collector nozzle, hereinafter referred to as"Slide Gate Plates"and"Nozzle", which is provided with an isostatically pressed sleeve in its centre bore.

Prior art: The Slide Gate Plate and connected nozzles are conventionally used in a moulding process to cast molten steel into tundish or ingot in a controlled manner. Heitherto known Slide Gate Plate consists of two refractories plates-one of them being fixed and called top plate, and other being moving or sliding and called bottom plate. The fixed plate is attached to the bottom of the ladle and the sliding or the moving plate is attached to a collector nozzle for discharge of steel into tundish or ingot mould.

The Slide Gate Plates are exposed to very high thermal shock due to the fact that a large temperature difference occurs between the peripheral portion of the flow out nozzle hole of the gate plate and the outer portion away from the nozzle hole. This high thermal shock leads to spalling causing thereby considerable damage to such Slide Gate Plates. These Slide Gate Plates are also corroded by molten steel and slag as low melting point materials are washed away by molten steel flow.

To overcome these problems the Slide Gate Refractors use different raw materials like Alumna, Magnesia, Zirconia, etc. The conventional and existing methods of manufactures of Slide Gate Plate and nozzles are either by hydraulic pressing and firing or through pre-casting route or both.

However, the existing Slide Gate Plate suffer with following drawbacks :- 1. At times due to excessive corrosion at the joint of the bottom plate and collector nozzle, molten metal leak out which leads to breakouts; 2. Due to various stresses, cracks or erosion takes place in plate and nozzles particularly in area in and around bore of nozzle and plate; 3. Due to sticking of solidified steel on the slide surface, peeling of slide surface takes place ; 4. Adhesion of Alumna deposit on the inner side of the bore causes clogging of bore, Accordingly, this is an object of the present invention to obviate the drawbacks in the conventional or existing Slide Gate Plates.

Yet another object of the present invention is to provide the Slide Gate Plate which eliminates the joint in the bottom plate and collector nozzle thereby avoiding all kinds of failures of plate and collector nozzle joints.

Yet another object of the present invention is to provide a Slide Gate Plate and nozzle which is cost effective at the same time ensures highest degree of performance.

Another object of the present invention is to provide the Slide Gate Plate and nozzle, which has long life and uniform properties.

Detailed description of the invention: Accordingly, the present invention provides a Slide Gate Plate system which comprises of a top plate fixedly attached to the bottom of the ladle, a bottom or moving plate, a collector nozzle for discharging of steel into tundish or ingot mould, the said bottom or moving plate being slidingly attached to the said collector nozzle, and a single or multiple, isostatically pressed sleeve (s) being inserted in a centre hole in the bottom plate and collector nozzle and a ladle nozzle, in which the central portion around bore is made of isostatically pressed sleeve of similar or different composition as to rest of the nozzle.

The isostatically pressed sleeve which forms the core part of the refractory plate or nozzle can be made of different composition and of different configuration. Even in the same isostatically pressed sleeve different composition can be used at different height to take care of the erosion pattern at different places.

Another aspect of the present invention is to provide a method of making the Slide Gate Plate system which comprises: (a) forming a insert plate of a known material which then being pressed, fired and impregnated; (b) forming an isostatically pressed sleeve of uniform thickness to be used in the collector nozzle or ladle nozzle and/or slide plate to provide uniform density through out the bore for a minimum erosion; (c) fixing the said sleeve to insert plate by jointing them together in close tolerance with the help of jointing mortar; (d) drying the jointed inserts in order to harden the joints; (e) fixing the said jointed inserts in the metallic cassette and allowing it to become hard; and (f) air curing and drawing the same in the conventional manner to obtain the Slide Gate Plate.

Brief Description of the invention with Drawings : Now the present invention will be described with reference to accompanying drawings, Figure-1 shows sectional view of a conventional Slide Gate Plate and Nozzles ; Figure-2 shows a sectional view of a Slide Gate Plate and Nozzles of the present invention.

Referring to figures, a slide gate plate system comprises of a bottom plate (1), a collector nozzle (2), a ladle nozzle (3), insert plate (4), a castedlfired plate for fixing Insert plate (5), and an single isostatically pressed sleeve (6) which eliminates the joint between the said bottom plates and collector nozzle.

Detailing of the process followed for manufacture of Slide Gate Plates and Nozzles:- (1) Bottom Plate :- For manufacturing this plate four steps are followed:- a) Insert plate making : This plate is designed in such a way that sliding area during use is taken care and the dimensions of plate are fixed. Then this plate insert is pressed on normal hydraulic press, dried, fired and processed; b) Isostatically Pressed Sleeve: This is designed in such a way that erosion of the slide plate/nozzle portion is taken care and thickness of insert is fixed. This sleeve is pressed isostatically to give it uniform density throughout the bore for minimum erosion. Then it is dried, fired and processed; c) Fixing of sleeve and insert plate : Sleeve and insert plate are joined together in close tolerance (less than 0. 5mm) with the help of suitable jointing mortar.

Then both are dried so that joint is hard for further processing ; d) Final casting of Bottom Plate: Jointed plate and sleeve inserts are fixed in the metallic cassette and the balance portion of remaining plate and nozzle is casted with a specially developed castable. After 6-8 hrs the castable becomes hard and then this is air cured and dried in drier.

(2) Nozzles: a) Sleeve processing :-Based on the bore size of the nozzle, suitable size of sleeve is designed and pressed isostatically. Composition of the sleeve could be totally different from that of the rest of the nozzle. b) Making of nozzle :-This is done in 2 ways. In first case, the isostatically pressed sleeve is put in a mould and cast with suitable grade of castable to give exact shape of nozzle, with sleeve in the core In the second case nozzle with suitable bore to accommodate the isostatically pressed sleeve is pressed and fired. After firing the isostatically pressed sleeve is fixed with correct type of mortar.

The invention described above with reference to accompanying drawing is merely illustrative in nature to understand the aspects of the invention. However, this is not intended to limit the scope of the invention to the embodiments as described above. The combinations and permutation within the scope of the invention are possible without departing from the soul of the invention.