GB1593372A - Refractory structures - Google Patents

Description

(54) REFRACTORY STRUCTURES (71) We, DIDIER-WERKE A.G., a Company organised under the laws of the Federal Republic of Germany, of Lessingstrasse 16, 62 Wiesbaden, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to refractory structures for use in the outlets of metallurgical vessels such as casting ladles and tundishes and to refractory structures for use in outlet control devices for such vessels and in particular sliding gate valves.

The invention also extends to methods of making the novel structures and to novel sliding gate valves incorporating the novel refractory structures.

The invention is described with particular reference to the casting of steel but the structures are applicable to the casting of other metals of lower melting point for example copper alloys and aluminium.

Such apparatus comprises a stationary refractory upper plate defining a discharge passage and adapted to be located on the outside of the vessel in juxtaposition to the outlet orifice of the vessel, e.g. by being held in a metal mounting attached to the.

shell of the vessel, and a movable refractory sliding plate defining a discharge passage and mounted for movement between an open position in which the discharge passages of the two plates are in register and a closed position in which the movable plate shuts off the discharge passage of the fixed plate.

Such apparatus will be referred to herein as a sliding gate valve and it will be appreciated that the movement of the movable plate can be rotatary though a straight sliding motion is preferred.

One form of such apparatus has a fixed upper plate and a moveable lower plate.

Such apparatus will be referred to herein as a two plate sliding gate valve. The moveable plate is preferably mounted for movement in a metal casing, and may incorporate an outlet nozzle or co-operate with one which is also mounted in the metal casing for movement with the sliding plate.

Another form of such apparatus has the movable plate mounted for movement between upper and lower fixed plates and is thus substantially parallel faced and the lower fixed plate incorporates or cooperates with an outlet nozzle.

Such apparatus will be referred to as a three plate sliding gate valve.

Conventional refractory plates and nozzles for use in such apparatus are made by pressing a refractory granular mass and then firing it at high temperature and then drilling out the outlet passage.

Conventional pressed and fired refractory plates of sliding gate valves are subject to very severe conditions in use particularly for metals like steel which have to be cast at very high temperatures exceeding 1500"C.

This leads to rapid wear, by thermal shock, chemical corrosion, mechanical erosion and mechanical stress, so that the refractory plates have to be replaced at very frequent intervals. Under the most severe conditions these plates have to be replaced after each casting even if the highest quality of refractory material is used. This is very inconvenient operationally, the more so as these plates have to be accurately mounted in metal supports by means of an intermediate layer of mortar which takes time to set.

It is one object of the invention to simplify replacement of the nozzles which are used on the inlet and outlet sides of the sliding gate valve and to provide nozzles for sliding gate valves which may be mounted without the use of mortar. According to the present invention a refractory nozzle for use with a refractory plate for a sliding gate valve for the outlet of vessels containing molten metal, incorporates at least one discharge passage extending through the nozzle from one end face to the opposite end face thereof and consists of a refractory material surrounded by a metallic sheath.

the refractory material being a refractory concrete poured into and set in the metallic sheath constructed as a dead mould substantially the whole of the surface of the nozzle apart from the end faces thereof being sheathed. The nozzle can be used on the inlet or outlet side of the sliding gate valve.

Preferably the metallic sheath and the refractory concrete have the same coeffi cicnt of thermal expansion.

The term cold cured includes materials which have been hcated merely to dry them, and also materials which have been impregnated e.g. with pitch e.g. at 450"C followed by hcating to remove the volatiles at for example 600"C.

The concrete is desirably a hydraulic setting and bonding, high alumina, refractory concrete with a compressive strength of at least 400 Kp/cm2 determined on the dried, cold, unfired product and at least 700 Kp/cm2 after firing at 14()() C and a stability of shape of at least + 0.2% at 14000C.

Nozzles in accordance with this aspect of the invention may be made by providing a mould having the desired shape for the structure, locating the metal sheath, constructed as a dead mould, in the mould inserting a removable core in the location for the discharge passage, preparing a cold setting cold curable refractory concrete composition having the desired refractory properties after setting, inserting the con crcte into the mould within the sheath or into the sheath, allowing the concrete to set in the sheath, removing the set composite structure from the mould (if used), allowing the structure to cold cure, removing the removable core, drying the structure, and preferably machining the face, which is to mate with a face of the plate with which the nozzle is associated in use, to the desired degree of flatncss.

The method preferably also includes the step of impregnating the cast dried structure with an appropriate carboniferous composition such as pitch, in a liquid state e.g. at 450 followed by further heating e.g. at 600"C to drive off volatile constituents.

Clearly any parts of the nozzle which it is desired should remain porous or open such as ducts must be appropriately masked during the procedure.

The metal sheath is preferably spaced from the said discharge passage or passages, preferably by a distance of at least 50% the radius of the discharge passage and desirably by a distance of 50% to 100% of the radius, the criteria for the spacing being that sufficient insulation of the metal sheath must be provided to prevent its reinforcing function being negated.

The thin metal sheath is desirably provided with keying means to engage the refractory body preferably located at the face remote from the discharge aperture.

The metal sheet preferably has a thickness of less than 20% of the thinnest part of the refractory body and is located on the outside face of the body so as to directly engage machined bearing areas in the metal support for the nozzle obviating the need for mortar.

In contrast to known nozzles the refractory nozzle according to the invention can be manufactured in a single operation without the use of mortar and give high accuracy to size by using the desired metallic sheath itself as the casting mould and so obtaining strong bonding between the sheath and the refractory concrete. Refractory nozzles according to the invention can be economically produced and are of high quality. It is unexpected that refractory nozzles of this type meet the exacting requirements in use of contact with molten metal.

The invention also extends to a process of manufacturing a nozzle for use with a refractory plate of a sliding gate valve for the outlet of vessels containing molten metal, the nozzle consisting of a refractory material surrounded by a metallic sheath constructed as a dead mould substantially the whole of the surface of the nozzle apart from the ends thereof becoming sheathed.

An outlet nozzle in accordance with the present invention can advantageously be used as part of sliding gate valve for the outlet of vessels containing molten metal, incorporating a refractory plate, the apparatus incorporating a supporting frame for the plate and in which the plate is braced in the supporting frame and the nozzle is braced to the plate. The special metallic sheath facilitates this bracing so that also the mounting of the refractory plate, such as a sliding plate on the supporting frame does not require fixing by means of mortar and this permits simple and quick replacement as compared for example with conventional fired ceramic plates and that is a great advantage particularly where different sliding plates or outlet nozzles are to be used for example magnesite plates are preferentially used for continuous casting and concrete plates according to the invention are preferred for chill casting.

The sliding gate valve is preferably provided with a wedge shaped member ad)ust- able on the supporting frame which can act through a thrust piece of a shape fitting the shape of the refractory plate to brace the plate in the supporting frame.

The thrust piece preferably exerts bracing forces on the refractory plate in the longitu dinal as well as in the transverse direction.

The invention may be put into practice in various ways and one specific embodiment will be described by way of example with reference to the accompanying drawing which is a diagrammatic cross section of a sliding gate with a sliding plate and an outlet nozzle in accordance with the invention.

The cold setting cold cured concretes may be refractory alumina cement compositions.

These compositions are high alumina concretes in which the aggregate material is selected to have appropriate refractory properties for the metals with which the nozzle will be used.

Thus for casting metals such as aluminium or alloys having melting points of the same order of magnitude as aluminium, refractory concretes such as those containing 12 to 20% of hydraulic alumina cement and 80 to 88% of inert refractory aggregate can be used.

Two specific examples of such concretes are given below: Example 1 80 parts by weight of refractory aggregate containing 40% by weight of alumina particle size 0 to 5 mm was mixed with 20 parts by weight of Lafarge alumina cement containing 40% by weight of Al203 and 12 parts by weight of water.

This mixture is then poured into a dead mould (e.g. 7 in the Figure) which is located within the main mould, the concrete compacted by vibration if desired, allowed to set, and the composite nozzle incorporating the concrete and the dead mould or sheath removed from the main mould and allowed to cure and dry.

Example 2 80 parts by weight of Guyana bauxite containing 88% Al203 particle size 0 to 5 mm was mixed with 20 parts by weight of SECAR 250 (Registered Trade Mark) Lafarge cement containing 70% Al203 and 10 parts by weight of water. This concrete can be cast as described for Example 1.

However, when the plates are to be used to cast steels having melting points above 1500"C which are cast at temperatures 50"C to 600C above their melting points, the conditions which the plates have to withstand are very much more severe and in order to enable more than one casting operation to be carried out safely with the same plates, special compositions have to be used.

Thus the conditions involve very severe mechanical erosive and chemical corrosive attack on the edges of the discharge passages of the plates combined with extreme thermal shock, the plates before the pour starts being at only 200"C to 3000C, and especially with large vessels, considerable mechanical stress due to the head of molten metal above the plates.

For such conditions we prefer to use refractory concretes containing from 5 to 8 parts by weight of at least one hydraulic alumina cement, 2.5 to 4 parts by weight of at least one pulverent refractory material, desirably having a particle size of less than 50 microns, and preferably less than 1 micron, which may be clay, e.g. Kaolin or bentonite, micronised chromite or micronised fosterite, 0.01 to 0.30 parts by weight of an agent effective to increase the fluidity of the composition comprising an alkali metal phosphate, alkali metal polyphosphate, alkali metal carbonate, alkali metal carboxylate or alkali metal humate and 87.7 to 92 parts by weight of at least one refractory aggregate, desirably all of which passes a 10 mm mesh and about 25% of which passes a 0.5 mm mesh.

The hydraulic alumina cement may be any one or more of the following commer cial products: Lafarge "SECAR" 162, SECAR 250, SU PERSECAR 250 Registered trade mark), Rollandshutte (Registered Trade Mark) Standard, Rollandshutte Super, Istrabrand, Lumnite and ALCOA CA 25 (Registered Trade Mark).

The refractory aggregate may be calcined refractory clay, bauxite, cyanite, sillimanite, andalusite, corundum, tabular alumina, silicon carbide, magnesia, chromite or zircon or mixtures thereof.

Two specific examples of such concretes are given below: Example 3 90 parts by weight of refractory aggregate containing 40% by weight of alumina, particle size 0 to 5 mm was mixed with 6 parts by weight of Lafarge alumina cement containing 40% by weight of Awl203, 4 parts by weight of clay and 0.12 parts by weight of DOLAFLUX KJ (registered trade mark for a fluidizing agent sold by Zschimmer and Schwartz and comprising 38% sodium phosphate, 11% sodium silicate, 14% sodium carbonate and 37% sodium humate) and 7 parts by weight of water. This mixture is thixotropic and is thus easily cast and can be made to accurately fill the mould by shaking or vibrating the mould or inserting a vibrator in the liquid concrete in the mould.

Example 4 92 parts by weight of Guyana bauxite containing 88% Awl203, particle size 0 to 5 mm was mixed with 5 parts by weight of SECAR 250 (Registered Trade Mark) Lafarge cement containing 70% Awl203, 3 parts by weight of clay, 0.10 parts by weight of GIEBFIX special (a fluidizing agent sold by Zschimmer and Schwartz and comprising 64(who sodium phosphate, 26% sodium silicate and 10% sodium carbonate) and 6 parts of water.

This concrete can be cast in the same way as Example 3.

The metal sheath of the present invention is incorporated in the plate during the casting process as a dead mould. on the exterior side of the outlet nozzle remote from the heated aperture in the outlet nozzle.

The metal sheet, preferably of steel, preferably has a thickness of less than 20%, preferably 5% to 15% of the thickness of the thinnest part of the refractory body of the sleeve. The metal sheet preferably has a shoulder surrounding the sleeve, the walls of the shoulder forming a thrust face. The metal sheet may also have protuberances, hooks, loops or apertures to assist keying to the refractory concrete body of the sleeve, preferably loops are punched up out of the plane of the sheet so as to be keyed into the concrete body.

Referring now to the drawing there is shown a sliding gate 1 which has a sliding plate 2 with a discharge passage 3 and is braced or gripped in a surrounding frame 8.

The sliding plate 2 has a boss 17 surrounding the discharge passage 3 and tapering downwards from the flat underside of the sliding plate 2. The sliding plate 2 is covered by a metallic sheath on its outer edge and on the bottom area of its flat part as well as on the outer edge of the boss 17. The sliding plate 2 is made in such a way that the refractory concrete and the metallic sheath have a specific coefficient of thermal expansion of 0.7 to ().96/o at 1()00 C, preferably 0.8% at 1()0() C. The upper sliding face 20 of the sliding plate 2 and the downward facing surface 25 of the boss 17 are not sheathed.

The structure is preferably made by pouring the refractory concrete in through the opening of the mould 6 from the side where the boss 17 is located. During pouring the discharge tube 3 is held open by a core. A sleeve or insert 24 of higher wear resistance, indicated by dotted lines, may be cast as an integral part around the inlet end of the discharge passage 3, whilst the concrete for the sliding plate 2 is being poured into the mould.

The sliding plate forms the subject matter of our co-pending application No. 26648/76 Serial No. 1593371.

The discharge passages are of slightly tapered form to assist removal of the cores.

The sliding plate 2 is braced or gripped in the frame 8 by driving in a wedge shaped member 10, held under an overhang 9 of the frame 8, so that it presses against a thrust piece 11, which conforms to the end of the sliding plate 2, e.g. having the same curvature if the end of the plate is rounded. The piece 11 being acted upon by the wedge shaped member, against the edge of and engaging the end of the sliding plate 2 thus presses the sliding plate 2 against the opposite end flange 12 of the frame 8 and the plate is thus gripped between the members 11 and 12 of the frame 8. The frame 8 has a hole 13 for attachment of the slider rod (not shown) located in it next to the end flange 12.

The flat underneath part of the frame 8 has a downwardly extending collar 19, surrounding the boss 17 but spaced therefrom. An interchangeable chamber 14 is mounted within the collar 19 by means of a locking device 16.

An outlet nozzle 4 (in accordance with the present invention) with a discharge passage 5 is located within the chamber 14 by means of an outwardly and upwardly extending conical area or shoulder 15, which rests on a corresponding oppositely disposed surface of a sealing sleeve 31 which is detachably fixed to the chamber 14. The outlet nozzle 4 is also surrounded by a metallic sheath 7.

The outlet nozzle 4 is manufactured by pouring refractory concrete into the metallic sheath 7 constructed as a dead mould and allowing it to set in the sheath. The metallic sheath 7 covers only the outer surfaces of the outlet nozzle 4, including the inclined area 15, but the ends of the nozzle 4 facing upwards and downwards are left free. The outlet nozzle 4 has a recess 18 formed in its upper end. During casting the discharge passage 5 and the recess 18 are held open e.g. by cores. The boss 17 of the sliding plate 2 nests in the recess 18 in the sleeve 4.

Only alternative embodiments of a sliding plate and an outlet nozzle, being wearing parts of a sliding gate valve have been illustratively explained in detail. Corresponding embodiments for the bottom plate of a sliding gate valve and an inlet nozzle, can readily be made particularly because the bottom plate and the sliding plate on the one hand and the inlet nozzle and the outlet nozzle on the other hand may be identical or at least very similar both in shape and materials.

WHAT WE CLAIM IS: 1. A refractory nozzle for use with a refractory plate for a sliding gate valve for the outlet of vessels containing molten metal incorporating at least one discharge passage extending through the nozzle from one end face to the opposite end face thereof and consisting of a refractory material surrounded by a metallic sheath, the refractory material being a refractory concrete poured into and set in the metallic sheath constructed as a dead mould substantially the whole of the surface of the nozzle apart from the end faces thereof being sheathed

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. by Zschimmer and Schwartz and comprising 64(who sodium phosphate, 26% sodium silicate and 10% sodium carbonate) and 6 parts of water. This concrete can be cast in the same way as Example 3. The metal sheath of the present invention is incorporated in the plate during the casting process as a dead mould. on the exterior side of the outlet nozzle remote from the heated aperture in the outlet nozzle. The metal sheet, preferably of steel, preferably has a thickness of less than 20%, preferably 5% to 15% of the thickness of the thinnest part of the refractory body of the sleeve. The metal sheet preferably has a shoulder surrounding the sleeve, the walls of the shoulder forming a thrust face. The metal sheet may also have protuberances, hooks, loops or apertures to assist keying to the refractory concrete body of the sleeve, preferably loops are punched up out of the plane of the sheet so as to be keyed into the concrete body. Referring now to the drawing there is shown a sliding gate 1 which has a sliding plate 2 with a discharge passage 3 and is braced or gripped in a surrounding frame 8. The sliding plate 2 has a boss 17 surrounding the discharge passage 3 and tapering downwards from the flat underside of the sliding plate 2. The sliding plate 2 is covered by a metallic sheath on its outer edge and on the bottom area of its flat part as well as on the outer edge of the boss 17. The sliding plate 2 is made in such a way that the refractory concrete and the metallic sheath have a specific coefficient of thermal expansion of 0.7 to ().96/o at 1()00 C, preferably 0.8% at 1()0() C. The upper sliding face 20 of the sliding plate 2 and the downward facing surface 25 of the boss 17 are not sheathed. The structure is preferably made by pouring the refractory concrete in through the opening of the mould 6 from the side where the boss 17 is located. During pouring the discharge tube 3 is held open by a core. A sleeve or insert 24 of higher wear resistance, indicated by dotted lines, may be cast as an integral part around the inlet end of the discharge passage 3, whilst the concrete for the sliding plate 2 is being poured into the mould. The sliding plate forms the subject matter of our co-pending application No. 26648/76 Serial No. 1593371. The discharge passages are of slightly tapered form to assist removal of the cores. The sliding plate 2 is braced or gripped in the frame 8 by driving in a wedge shaped member 10, held under an overhang 9 of the frame 8, so that it presses against a thrust piece 11, which conforms to the end of the sliding plate 2, e.g. having the same curvature if the end of the plate is rounded. The piece 11 being acted upon by the wedge shaped member, against the edge of and engaging the end of the sliding plate 2 thus presses the sliding plate 2 against the opposite end flange 12 of the frame 8 and the plate is thus gripped between the members 11 and 12 of the frame 8. The frame 8 has a hole 13 for attachment of the slider rod (not shown) located in it next to the end flange 12. The flat underneath part of the frame 8 has a downwardly extending collar 19, surrounding the boss 17 but spaced therefrom. An interchangeable chamber 14 is mounted within the collar 19 by means of a locking device 16. An outlet nozzle 4 (in accordance with the present invention) with a discharge passage 5 is located within the chamber 14 by means of an outwardly and upwardly extending conical area or shoulder 15, which rests on a corresponding oppositely disposed surface of a sealing sleeve 31 which is detachably fixed to the chamber 14. The outlet nozzle 4 is also surrounded by a metallic sheath 7. The outlet nozzle 4 is manufactured by pouring refractory concrete into the metallic sheath 7 constructed as a dead mould and allowing it to set in the sheath. The metallic sheath 7 covers only the outer surfaces of the outlet nozzle 4, including the inclined area 15, but the ends of the nozzle 4 facing upwards and downwards are left free. The outlet nozzle 4 has a recess 18 formed in its upper end. During casting the discharge passage 5 and the recess 18 are held open e.g. by cores. The boss 17 of the sliding plate 2 nests in the recess 18 in the sleeve 4. Only alternative embodiments of a sliding plate and an outlet nozzle, being wearing parts of a sliding gate valve have been illustratively explained in detail. Corresponding embodiments for the bottom plate of a sliding gate valve and an inlet nozzle, can readily be made particularly because the bottom plate and the sliding plate on the one hand and the inlet nozzle and the outlet nozzle on the other hand may be identical or at least very similar both in shape and materials. WHAT WE CLAIM IS:

1. A refractory nozzle for use with a refractory plate for a sliding gate valve for the outlet of vessels containing molten metal incorporating at least one discharge passage extending through the nozzle from one end face to the opposite end face thereof and consisting of a refractory material surrounded by a metallic sheath, the refractory material being a refractory concrete poured into and set in the metallic sheath constructed as a dead mould substantially the whole of the surface of the nozzle apart from the end faces thereof being sheathed

2. A refractory nozzle as claimed in Claim 1 in which the metallic sheath and the refractory concrete have the same coefficient of thermal expansion.

3. A refractory nozzle as claimed in Claim 1 or Claim 2 in which the metallic sheath contains hydraulic setting and bonding, high-alumina, refractory concrete with a com2pressive strength of at least 400 Kp/cm determined on the dried, cold, unfired product and at least 700 Kp/cm after firing at 14000C and a stability of shape of at least+0.2cib at 14000C.

4. A refractory nozzle as claimed in any one of Claims 1 to 3 in which the metal sheath is thin metal plate which has a thickness of not more than 20% of the thickness of the thinnest part of the nozzle.

5. A refractory nozzle as claimed in Claim 1 substantially as specifically described herein with reference to the accompanying drawing.

6. A process for making a refractory nozzle as claimed in any one of claims 1 to 5 in which a refractory concrete is poured into and allowed to set around a removable core located in the metallic sheath and arranged to define the discharge passage in the metallic sheath which is constructed as a dead mould substantially the whole of the surface of the nozzle apart from the end faces thereof becoming sheathed.

7. A process as claimed in Claim 6 in which the the refractory concrete is a hydraulic setting and bonding, highalumina, refractory concrete with a compressive strength of at least 400 Kp/cm2 determined on the dried, cold, unfired product and at least 700 Kp/cm2 after firing at 1400"C and a stability of shape of at least + 0.2% at 1400"C.

8. A process as claimed in Claim 6 substantially as specifically described herein with reference to the accompanying drawing.

9. A refractory nozzle whenever made by a process as claimed in any one of Claims 6 to 8.